Hate ^allege of JVgricultutc At (Sfornell UniaerHitH Hibratg Cornell University Library TN 775.R55 1896 Aluminium; its history, occ"''* "SiPmSP^ 3 1924 003 633 751 Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924003633751 ALUMINIUM. ALUMINIUM: ITS HISTORY, OCCURRENCE, PROPERTIES, METALLURGY AND APPLICATIONS, INCLUDING ITS ALLOYS. BY JOSEPH W. RICHARDS, A. C, Ph.D., INSTRUCTOR IN METALLURGY AT THE LEHIGH UNIVERSITY. \ THIRD EDITION, REVISED AND ENLARGED. ILLUSTKATED BY f . . FORTY-FOUR ENGRAVINGS AND TWO DIAGRAMS. PHILADELPHIA : HENRY CAREY BAIRD & CO., INDUSTRIAL PUBLISHERS, BOOKSELLERSi, AND IMPORTERS, No. 810 Walnut Stbebt. LONDON : SAMPSON LOW, MARSTON & CO., Limited, ST, dunstan's house, petteb lane, fleet stbeet, 1896, TH115' (5 13% S^ COPYEiaHT BY JOSEPH W. RICHARDS, 1895. Feinted by the WICKEESHAM PRINTING CO., 63 and 55 N. Queen Street, Lancastek, Pa., U. S. A. l>e&icatlon. TO THE MEMORY OF iFteberick Mobler OP GOTTINGEN, THE DISCOVERER OP ALUMINIUM, AND OF Ibenti Sainte^Claite Seville OF PARIS, FOUNDER OP THE ALUMINHJM INDUSTRY. THE FRUITS OF WHOSE LABOBS HAVE ENBICHED SCIENCE AND BENEFITED MANKIND. PREFACE TO THE THIRD EDITION. Ten years ago aluminium was an almost unknown metal; then it sold for twelve dollars a pound, now it is bought for fifty- cents ; then the yearly production was less than is the present daily output ; then only three books had been written about it, since then seven have appeared and two journals have been es- tabHshed to represent it. The lowering of the price, the increased production, the wide circulation of reliable information about aluminium, have brought to pass the dream of Deville, for it has truly become a metal of every-day life. The abundance of aluminium in nature, the purity of its ores, its wonderful lightness and adaptability to numerous purposes, indicate that the goal of the aluminium industry will be reached only when this metal ranks next to iron in its usefulness to man- kind. To assist this consummation by furnishing all the reliable in- formation about aluminium, to thus enlighten the general reader, help the workman, instruct the student, assist the experimenter, and in every way to speed the industry on its destined path, is the raison d'etre of this work. The writer thanks the public for its generous appreciation of his past endeavors. The volume has been revised to date, sev- eral chapters have been largely re-written, and every effort has been made to make the work worthy of the splendid industry which it represents. Joseph William Richards. The LEfflGH University, Bethlehem, Pa., October zj, iSgs- (vii) PREFACE TO THE SECOND EDITION. If it was true that no apology was necessary in presenting a work on Aluminium in English, as stated in the preface to the first edition of this book, it is equally true that still less apology is necessary in offering an improvement on that work. The present volume is designed to be an improvement on the former one in the following respects : Mistakes have been corrected wherever detected by the author or pointed out by his friends ; in some instances the order of treatment of different parts has been revised, so as to bring them into strict, logical sequence ; the more strictly historical processes are described in greater detail, in order to preserve a complete record of the rise of the aluminium industry; chapters have been added treating on the properties and the preparation of aluminium compounds, on the theoretical aspect of the reduction of aluminium com- pounds, and on the analysis of commercial, aluminium and its common alloys ; the original chapters have been in several cases sub-divided, and every part treated more by itself and in greater detail than before ; finally, additions have been made through- out recording and describing the progress achieved in the last three years, with a completeness which it is hoped is up to the standard of the rest of the book. The method of treatment in the present edition will be found to be more critical, for wherever a reasonable doubt might be expressed as to the correctness of certain claims, or a rational explanation advanced for certain phenomena, the author has not (ix) X PREFACE TO THE SECOND EDITION. hesitated to put his best thought on the question and to state his conclusions unreservedly. The friendly criticisms of the scientific press and their sug- gestions have been kept in view in preparing this new edition. The spelHng " aluminium " has been retained, because no suffi- cient reasons have been advanced for changing it to " alu- minum;" and even if each way was equally old and as well- sanctioned by usage and analogy as the other, the author's choice would be the longer spelling, as being more euphonious and agreeable to the ear. It has been the author's endeavor to make this volume as complete as possible, as accurate as possible, to write it in a manner which will be entertaining to the general reader, and to furnish a treatise which will be of practical value to the practical metallurgist, as well as of scientific merit where it touches on matters of theory. J. W. R. Bethlehem, Pa., March 12, i8()o. PREFACE TO THE FIRST EDITION. No apology is necessary in presenting a work on Aluminium in English. In 1858 Tissier Bros, published in France a small book on the subject. H. St. Claire Deville, the originator of the aluminium industry, published a treatise, also in French, in 1859. Deville's book is still the standard on the subject. Until December, 1885, we have an intermission, and then a work by Dr. Mierzinski, forming one of Hartleben's Chemisch-Technische Bibhothek, which is a fair presentation of the industry up to about 1883, this being a German contribution. Probably be- cause the English-speaking people have taken comparatively little hand in this subject, we find no systematic treatise on aluminium in our language. The present work aims to present the subject in its entirety to the English reader. Tissier, Deville, Mierzinski, and the German, French, and English scientific periodicals have been freely consulted and extracted from, full credit being given in each case to the author or journal. As this art has of late advanced so rapidly, it has been a special aim to give everything that has been printed up to the time of publication. The different parts of the work are arranged in what seemed their logical order, corresponding closely to that followed by Deville. The Appendix contains an account of laboratory ex- periments, etc., several of which, it is trusted, may be of value. In conclusion, the author wishes to thank the Faculty of his " Alma Mater," Lehigh University, for their permission to use (xi) Xli PREFACE TO THE FIRST EDITION. his Thesis on Aluminium as the basis of this treatise ; also, to acknowledge his indebtedness to Dr. Wm. H. Greene, of Phil- adelphia, for assistance rendered in the preparation of the work for the press. J. W. R. Philadelphia, November 2j, j8S6. ABBREVIATIONS DSED IN MAKING REFERENCES. SEPARATE WORKS ON ALUMINIUM {Arranged chronologically.^ Tissier . Recherche de 1' Aluminium. C. & H. Tis- sier. Paris : J. Hetzel et Cie. 1858. Uhlenhuth Die Darstellung des Aluminiums. Ed. Uhl- enhuth. Quedlinburg: G. Basse. 1858. Deville De I'Aluminium. H. St. Claire Deville. Paris : Mallet-Bachelier. 1859. Mierzinski . Die Fabrikation des Aluminiums. Dr. Stan- islaus Mierzinski. Vienna : Hartleben's Chemisch-technische Bibliothek. 1885. Richards (ist Ed.) Aluminium. Joseph W. Richards. Phila- delphia : Henry Carey Baird & Co. 1887. Richards (2nd Ed.) Aluminium. Joseph W. Richards. Phila- delphia : Henr}' Carey Baird & Co. i8go. Le Verrier Note sur la Metallurgie de I'Aluminium. U. LeVerrier. Paris: BaudryetCie. 1891. Minet L' Aluminium. Adolphe Minet. Paris ; Ber- nard Tignol. 1892. Lejeal L'Aluminium. Adolphe Lejeal. Paris: J. B. Bailli^re et File. 1894. TREATISES IN ENCYCLOPEDIAS. Fremy Enclyclop£die Chimique. Fremy. Paris : Ch. Dunod. Art : L'Aluminium par Margottet (1883). Art : L'Aluminium et ses Alliages par Wick- ersheimer (1890). Kerl and Stohman Enclyclopadisches Handbuch der Tech- nischen Chemie. 4th Ed. Brunswick : Vieweg und Sohn. 1886. Art: Aluminium von R. Biederman. Watts Watts' Dictionary of Chemistry. ( xiii ) xiv ABBREVIATIONS USED IN MAKING REFERENCES. JOURNALS AND PERIODICALS. Ann. de Chim. et de Phys. . . Annales de Chimie et de Physique. Ann. der Chem. und Pharm. ) Liebig's Annalen der Chemie und Phar- Liebig's Ann J made. Bull, de la Soc. Chim Bulletin de la Soci^t^ Chimique de Paris. Chem. News The Chemical News. Chem. Zeit. . . Chemiker Zeitung (Cothen). Compt. Rend Comptes Rendus de les Stances de I'Acadd- mie. Paris, Dingl. Jrnl Dingler's Polytechnisches Journal. E. and M. J The Engineering and Mining Journal. Jahresb. der Chem Jahresbericht ueber die Fortschritte der Chemie. Jrnl. Chem. Soc Journal of the Chemical Society. Jrnl. der Pharm Journal der Pharmacie. Jrnl. fiir pr. Chem Erdmann's Journal fiir praktische Chemie. Mon. Scientif. Le Moniteur Scientifique. Dr. Quesnesville. Phil, Mag The London and Edinburgh Philosophical Magazine. Phil. Trans ... Transactions of the Royal Philosophical Society. Pogg. Ann Poggendorff's Annalen. Poly. Centr. Blatt Polytechnisches Central-Blatt. Proc. Ac. Nat. Sci. .... Proceedings of the Academy of Natural Sciences (Philadelphia). Quarterly Journal Quarterly Journal of the Society of Arts. Rpt. Brit. A. A. S Report of the British Association for the Advancement of Science. Sci. Am. (Suppl.) Scientific American (Supplement). Wagner's Jahresb Wagner's Jahresbericht der Chemischen Technologic. Zeit. fiir anal. Chem Zeitschrift fiir Analytische Chemie. JOURNALS REPRESENTING THE ALUMINIUM INDUSTRY. The Aluminum World .... New York. Published monthly. Estab- lished September, 1894. L'Aluminium Paris. Published monthly. Established January, 1895. CONTENTS. CHAPTER I. History op Ai■ Bauxite from Freisstritz (Schnitzer). White > White Wocheinite (L. Mayer and O. Wagner). Bauxite from Irish Hill. OCCURRENCE OF ALUMINIUM IN NATURE. 43 10. Bauxite from Co. Antrim (Spruce). 11. « " Glenravel (F. Hodges). 12 and 13. " " Hadamar in Hesse (Retzlaff). 14. From Klein-Steinheim (Bischof). 15 and 16. From Langsdorfi (I. Lang). 17. Bauxite from Dublin, Ireland, brought to the Laurel Hill Chemical Works, Brooklyn, L. I., and there used for making alums. It is dirty white, hard, dense, compact, and in addition to the ingredients given above contains 0.59 per cent, of lime and some titanic acid. It costs $6 per ton laid down in the works. The above analysis, made by Mr. Joiiet, is furnished me by the kindness of the superintendent of the works, Mr. Herreshoff. The American bauxites are fully equal to the foreign in quality, as is shown by the following analyses : Ferric Oxide. Silica Water Titanic Acid. 18 Alumina | 37-62 1.83 11.48 28.63 19 55-59 6.08 10.13 28.99 20 21 22 46.44 58-60 46.72 22.15 9.II 2.14 4-89 3-34 29.01 26.68 28.63 20.15 — — 0.87 Alumina — Ferric Oxide Silica Water Titanic Acid 58.61 2.63 8.29 27.42 3-15 24 67-53 trace 1-34 28.00 2.92 25 60.61 0.21 2-47 32.00 4.18 26 61.87 2.38 0.40 30.50 27 40-93 22.60 8-99 20.43 18. Little Rock Region, Pulaski Co., Arkansas. jg >I « " " " 20. Red variety. Saline Co., Arkansas. 21. Pink " 22. White variety, Floyd Co., Georgia. 2j- 24. Georgia Bauxite Company. 2c " " " 26. Wharwhoop Mine, Cherokee Co., Alabama. 27. Red variety, Cherokee Co., Alabama. 44 ALUMINIUM. Regarding French bauxites, Francis Laur, the first to work the French deposits, states* that one of their peculiarities is that the bulk of that mined contains a nearly constant amount of alumina, of silica, ferric oxide and water taken together, and of other impurities. The proportions are very nearly Alumina 68 to 70 per cent. Silica, ferric oxide and water 27 " Other impurities 3 to 4 " In the bauxite from Baux, that first worked, the silica, ferric oxide and water are present in about equal proportions ; that is, about 8 to 10 per cent, of each. In the pale bauxite from Villeveyrac (Herault) there is almost no iron, and the 27 per cent, is nearly evenly divided between silica and water ; what small amount of ferric oxide does occur in it can be put into the list of " other impurities." The red bauxite, discovered in 1880 in the south of France, is very constant in composition, and may be regarded as the inverse of the pale variety. In this red kind the silica is so small as to be relegated to the acces- sory constituents, while water and ferric oxide alone make up the 27 per cent. These three varieties represent the three types of bauxite which are mined in large quantities. The pale variety, being low in iron, is preferred for making aluminium sulphate by treatment with sulphuric acid, which attacks it very readily; the red kind is preferred for the sodium carbonate treatment, as the iron does not interfere, while silica is kept out of the alumina produced. Besides these kinds, some varieties are found with the 27 per cent, either all water, all silica or all ferric oxide. We would thus have, as the composition of the typical kinds of bauxite found in France, the following: Water. Silica. Ferric oxide. Hyaline bauxite 27 o o Silicious type, compact o 27 o Ferruginous type, in pisolites o o 27 Red bauxite of Var 131^ o 131^ Pale bauxite of Villeveyrac 131^ i^}4 o Mixed bauxite of Baux 9 9 9 * Trans. Am. Inst. Mining Eng., Feb., 1894. OCCURRENCE OF ALUMINIUM IN NATURE. 45 Mr. A. E. Hunt, of Pittsburgh, in the discussion of this paper, remarked that there are vast quantities of bauxite in Georgia, Alabama and Arkansas, which run low in both silica and ferric oxide, containing less than 5 per cent, of both these ingredients, but with about 4.5 per cent, of titanic acid. It is his experience that when the water of hydration is below 31 per cent., in the greyish and white bauxite from Georgia and Alabama, the silica is always high. If the bauxite is red, however, the water may be low without the silica being high. He cites the follow- ing analyses illustrating this point : Combined water. Silica. Ferric oxide. Titanic acid. Alumina, 33-43 0.80 0.47 4.20 61.10 32.00 2.66 0.47 4.06 60.81 20.93 22.96 0.47 4.72 51.14 16.70 32-03 0.71 3-76 47-03 18.20 3.10 17-3° 3-9° 57.00 It will be seen that Mr. Laur's generalizations regarding French bauxites do not hold good for the American varie- ties ; the constancy of the titanic aci,d is also remarkable. Cryolite. Cryolite was first found at Ivigtuk in Arksut-fiord, west coast of Greenland, where it constitutes a large bed or vein in gneiss. It was very rare even in mineralogical collections until 1855, when several tons were carried to Copenhagen and sold under the name of " soda mineral." It is a semi-transparent, snow- white mineral. When impure it is yellowish or reddish, even sometimes almost black. It is shining, sp. gr. 2.95, and hard- ness 2.5 to 3. It is brittle, not infrequently contains ferrous carbonate, sulphide of lead, silica, and sometimes columbite. It is fusible in the flame of a candle, and on treatment with sulphuric acid yields hydrofluoric acid. As will be seen further on, cryolite was first used by the soap-makers for its soda ; it is still used for making soda and alumina salts, and to make a white glass which is a very good imitation of porcelain. The Pennsylvania Salt Company in Philadelphia import it from 4-6 ALUMINIUM. Ivigtuk by the ship-load for these purposes ; lately they have discontinued making the glass. Cryolite is in general use as a flux. A very complete description of the deposit at Ivigtuk can be found in Hoffman's " Chemische Industrie." Pure cryolite contains Aluminium l3-° Fluorine 54-5 Sodium 32.5 100.00 Or otherwise stated, Aluminium fluoride 40.25 Sodium fluoride ■* 59-75 100.00 From the reports in the Mineral Resources of the United States we find that there was imported by the Pennsylvania Salt Company in 1892, 8000 long tons, which was valued at $9 a ton. The importers say this value is too low ; they sell what they call pure prepared cryolite at $60 a ton. This so called pure article was found by Prof. Rogers, of Milwaukee, to contain two per cent, of silica and one per cent, of iron ; in fact, the whitest cryolite always contains silica microscopically disseminated through it, which cannot be separated out by any means. The only known deposit of cryolite in the United States is that found near Pike's Peak, Colorado, and described by W. Cross and W. F. Hillebrand in the "American Journal of Science," October, 1883. It is purely of mineralogical import- ance and interest, occurring in small masses as a subordinate constituent in certain quartz and feldspar veins in a country rock of coarse reddish granite. In composition, however, it is practically identical with the Greenland cryolite, so that the following analysis by Mr. Hillebrand will stand for a typical analysis of cryolite as found in nature : OCCURRENCE OF ALUMINIUM IN NATURE. 47 Fluorine 53.55 per cent. Aluminium , 12,81 " Sodium 32.40 " Ferric Oxide 0.40 " Lime 0.28 " Water 0.30 " Corundum. Until 1869 the sole sources of corundum were a few river washings in India and elsewhere, where it was found in scat- tered crystals. Its cost was twelve to twenty-five cents a pound. Within the last twenty years numerous mines have been opened in the eastern United States, the first discovery of which was due to Mr. W. P. Thompson, and is thus described by him : * " In 1869, in riding over a spur of the Alleghenies in north- ern Georgia, I found what has proven to be an almost inex- haustible mine of corundum in the chrysolite serpentine, the first instance on record of the mineral being found. /« situ. Previ- ously it had been washed out of debris at Cripp's Hill, N. C, and at a mine in West Chester, Pa., both on the slopes of the chrysolite serpentine. The clue being thus obtained accident- ally, about thirty mines were shortly afterwards discovered in the same formation ; but of the thousands of tons thus far dug out, the larger portion has come from the mines I discovered. " At present it can be bought at about ten dollars per ton at the mines. It is nearly pure alumina. Disapore, a hydrated alumina, is also found in the same region and locality. Corun- dum will probably always be the principal source in America of material from which to manufacture pure aluminium ; but in Great Britain, in all probability, manufacturers must look to alumina prepared artificially from cryolite or from sulphate of alumina." In 1892 the production of corundum in the United States was somewhat over 2000 short tons, valued at $40 a ton when sifted and broken to proper sizes for the market, the Hamp- * Journal of the Society of Chemical Induustry, April, 1886. 48 ALUMINIUM. den Emery Company, at Laurel Creek, Ga., and at Corundum Hill, N. C, and the Unionville Corundum Mines Company, at Unionville, Chester Co., Pa., being the principal producers. Thus, while corundum may be worth in bulk at the mines only $io a ton, yet it is extremely hard to crush, and when broken up fine is worth far more as an abrasive than as an aluminium ore. The present large development of bauxite mining has completely nullified the use of corundum as a source of alumin- ium, and I do not suppose that at present a single pound of aluminium is being made from it. Kaolin. The mineral kaolin is variously known as white china clay, fuller's- earth, or pure white clay. It is essentially a hydrated silicate of aluminium, containing when pure Alumina 39.8 per cent. Silica 46.3 Water 13.9 " Its chemical formula is Al2O3.2SiO2.2H2O. If the water is driven off by calcination, the residue contains 46.2 per cent. of alumina, or 24.4 per cent, of aluminium. Kaolin has been formed mostly by the atmospheric decom- position of feldspar, the alkalies of which are changed into carbonates by the carbonic acid of the rain water, and are then leached out, carrying with them part of the silica in solution, and leaving kaolin, according to the reaction, K2Al2Si60,6f2H20+C02=Al2SiA.2H20+K2C03-t-4Si02. Kaolin acquires a certain plasticity when mixed with water. Hydrochloric and nitric acids have no action on it, but cold sulphuric acid dissolves its alumina, setting the silica at liberty. It is infusible unless contaminated with particles of feldspar or calcium sulphate, carbonate, or phosphate. The specific gravity of kaolin is 2.3. If fused with six times its weight of caustic potash, the resulting mass gives up potassium aluminate when OCCURRENCE OF ALUMINIUM IN NATURE. 49 washed with water, An analogous result is obtained with sodium carbonate. Grabau has prepared very pure aluminium fluoride from kaolin by the use of sulphuric acid and subse- quent boiling with fluorspar. Large deposits of kaolin are found in many parts of the world. The best locality in Europe is near Limoges, France, with which the famous Sevres porcelain is made. Large beds are found in Cornwall and West Devon, England. In the United States the largest deposits are at Wilmington, Del., and in South Carolina, Georgia and Alabama. These deposits are worked extensively, and the product used by the pottery, paper, cotton, and various other industries. The value at the mines is very small, it not costing over $0.50 per ton to mine it, but for many purposes it must be crushed, washed, and even floated, which increases its value to $5 or $10 a ton in New York city. The purity of kaolin, and the almost inexhaustible beds in which it occurs, stamp it as the natural ore of aluminium. All that is needed is a cheap process for separating the pure alu- mina from the silica, in which case no other mineral could compete with it as the main staple of the aluminium industry. This is a promising field for chemical experimenters, for such a process would be of great value. Common clays are either very impure kaolin, or else they contain chemically a much larger proportion of silica. The percentage of silica may range from 50 per cent, up to 70 per cent, while that of the alumina present ranges downwards from 35 to 15 per cent. These common clays are far too impure and low in silica to serve as a source of aluminium, and in no case could they compete with kaolin. Some anhydrous silicates of aluminium are found in nature, such as Disthene, Andalusite and Cyanite, whose formula is AUOj.SiOj, containing 62.5 per cent, of alumina ; but they do not occur in large quantities, and, even if they did, are so hard and difficult to decompose that they would never be preferred to kaolin. 4 50 aluminium. Native Sulphate of Alumina. In the summer of 1884, a large deposit of rock called " native alum" was discovered on the Gila River, Socorro County, New Mexico, about two miles below the fork of the Little Gila, and four miles below the Gila Hot Springs. The deposit is said to extend over an area one mile square and to be very thick in places. The greater part of the mineral is impure, as is usual with native occurrences, but it is thought that large quantities are available. A company formed in Socorro has taken up the alum-bearing ground. Through the kindness of Mr. W. B. Spear, of Philadelphia, the author was enabled to get a speci- men of the mineral. It is white, with a yellowish tinge. On close examination it is seen to consist of layers of white, pure-looking material ar- ranged with a fibrous appearance at right angles to the lamina- tion. These layers are about one-quarter of an inch thick. Separating them are thin layers of a material which is deeper yellow, harder and more compact. The whole lump breaks easily, and has a strong alum taste. On investigation, the fibrous material was found to be hydrated sulphate of alumina, the harder material sulphate of lime. Analysis showed 7 to 8 per cent, of insoluble material, the remainder corresponding to the formula Al2(S04)3.i8H20. A small amount of iron was present. State Geologist Waring informs the writer that the deposits occur only in sheltered spots protected from the rain, that the region is eruptive, and that where the trachyte rock is being decomposed by sulphuric gases and waters, the salts rise to the surface and form crusts in protected places. Often the earth contains 10 per cent, or more of the anhydrous sulphate. A similar mineral occurs in Purgatory Valley, 12 miles east of Trinidad, Colorado. A variety of the same mineral containing some silica was found in a stratum 25 feet thick by the Congo Coal Company, while sinking a shaft at Congo, Ohio, in 1893. An analysis of this by Dr. Lisle, of Springfield, Ohio, gave OCCURRENCE OF ALUMINIUM IN NATURE. Si Alumina 50.16 per cent. Silica 28.98 " Lime 0.46 " Sulphuric acid 16.21 " Water 4.28 " These minerals would appear to ofifer a cheap source of alumina, as the operations necessary for treating them are very- simple, being solution in warm water, filtration, evaporation, and roasting. The excessive freight charges are against the New Mexico and Colorado deposits, but that in Ohio should be of considerable economic importance if the reports concern- ing its extent are verified. CHAPTER III. PHYSICAL PROPERTIES OF ALUMINIUM. Commercial aluminium is never chemically pure, and there- fore displays properties varying more or less from those of the pure .metal according to the character and amount of impurities present. In this treatise, whenever the properties of aluminium are mentioned, they must be understood to refer to the chemi- cally pure metal, and not to the commercial article, unless spe- cifically stated. The impurities most frequently present in commercial alu- minium are iron and silicon. These are found in all brands, varying in amount from i per cent, in the purest to 6 and even 8 per cent, in the worst. Besides these, various other impuri- ties are found coming from accidental sources in the manufac- ture ; thus, some of the first metal made by Deville contained a large amount of copper (Analysis i), coming from boats of that metal which he used in his experiments. Metal made later by Deville contained zinc, coming from zinc muffles which he had borrowed and used for retorts, old retorts broken up having been used in the composition of the new ones. More recently, aluminium has been produced by the agency of sodium in the presence of lead, which latter it takes up in small amount. Sodium is liable to remain alloyed in very small pro- portion, yet it is an element so easily attacked that it destroys some of the most valuable qualities of the aluminium. The distinct effect, however, of each of these usual impurities in modifying the physical properties of aluminium has not yet been investigated in a thoroughly satisfactory manner. A few years more, however, of increasing familiarity with and hand- ling of the metal on a large commercial scale will, I believe, (52) PHYSICAL PROPERTIES OF ALUMINIUM. S3 cause the effect of foreign elements on aluminium to be as plainly recognized as is now the case with carbon and the metalloids in iron. In general, we may say that silicon seems to play a role in aluminium closely analogous to that of carbon in iron ; the purest aluminium is fibrous and tough, but a small percentage of silicon makes it crystalline and brittle. Further- more, a considerable proportion occurs in the graphitoidal state, and may be separately estimated as graphitoidal silicon by dissolving the metal in dilute hydrochloric acid in the pres- ence of bromine water. A small amount of silicon, however,, gives pure aluminium a bluish cast, a disagreeable smell, and greatly lessens its resistance to corroding agents. A small proportion of iron makes the metal denser and stronger, but a quantity above i per cent, quickly makes it brittle. A small quantity of copper whitens aluminium, makes it much stronger and lessens its shrinkage in casting, but with over 5 per cent, it becomes brittle. As aluminium was made by the sodium processes, it con- tained as impurity about equal quantities of iron and silicon ; as made by the electrolytic processes, the iron present is usually much less than the silicon. Carbon can only exist in alumin- ium that has been subjected to an intense heat, such as in an electric furnace, when it may be absorbed in small quantity, and makes the metal brittle ; it does not occur, however, in ordinary commercial aluminium. Titanium may occur in aluminium made from raw bauxite, which frequently contains titanic oxide ; its presence in small amount makes the metal much stronger, but gives it a bluish tint. There is needed a systematic investigation of the effect of small amounts of impuri- ties on the physical and chemical properties of pure aluminium. The following analyses are of considerable historic interest as showing incidentally the improvement which has been made in the quality of the commercial metal since the beginning of the industry : 54 ALUMINIUM. Aluminium. 1. Deville Process 88.350 2. " " 92.500 3. " " 92.000 4. " " 92.969 5. " " 94-700 6. " " 96.160 7. Tissier Bros 94.800 8. Morin & Co., Nanterre 97.200 9. " " 97.000 10. " " 98.290 11. " " 97.680 12. Merle & Co., Salindres 96.253 13. " " 96.890 14. " " 97-400 15. " " 97.600 16. Frishmuth 97-49 17- " 97-75 18. Hall's Process 98-34 19. Deville-Castner - . 99.20 20. Grabau Process 99.62 21. " " 99-So 22. Hall's Process 99-93 Silicon. Iron. 2.87 2.40 0.70 6.80 0.45 7-55 2.149 4.88 3-70 1.60 0.47 3-37 4.40 0.80 0.25 2.40 2.70 0.30 0.04 1.67 0.12 2.20 0.454 . 3-293 1.270 1.840 1. 00 1.30 0.40 1.40 1.90 0.61 1.70 0.55 1-34 0.32 0.50 0.30 0.23 0.15 0.12 0.08 0.07 trace. Notes on the above analyses :- 2 and 3- 4- 5- 7- 8. 9- [O, II. 12, 13. 14. 15- 16. Analyzed by Salvetat. Contained also 6.38 per cent, of copper and a trace of lead. Analyzed by Dumas. Parisian aluminium bought in La Haag, Analyzed by SalvStat. Contained also a trace of sodium. Parisian aluminium bought in Bonn and analyzed by Dr. Kraut. Made at the works near Rouen, in 1858, from cryolite. Analyzed by Demond^ur. Analyzed by Sauerwein. Contained also traces of lead and sodium. Analyzed by Morin. Average of several months' work. Analyzed by Kraut. Represents the best product of the French works sent to the London Exhibition in 1862. Analyzed by Mallet. The best metal v/hich could be bought in 1880. Purchased in Berlin by Mallet, and used by him as the material which he purified and used for determining the atomic weight of aluminium. Analyzed by Hampe. This was the purest metal which could be bought in 1876. No. 14 contained also o.io per cent, of copper and 0.20 per cent, of lead. No. 15 contained 0.40 per cent, of copper and 0.20 per cent, of lead. Bought in Philadelphia as Frishmuth's aluminium, in 1885, and analyzed by the author. PHYSICAL PROPERTIES OF ALUMINIUM. 55 17. Specimen of the metal composing the tip of the Washington Monument, cast by Frishmuth. This analysis is reported by R. L. Packard m the Mineral Resources of the United States, 1883-4. 18. The best ordinary grade of metal made by this process, analyzed by Hunt & Clapp, Pittsburgh. For average analyses, etc., see description of pro- cess. 19. The best grade made by this process, exhibited at the Paris Exposition, 1889. Analyzed by CuUen. 20. Analysis by Dr. Kraut of metal being made on a commercial scale. 21. Analysis by Grabau of the purest metal yet obtained by his process. 22. Made from chemically pure alumina, in order to determine what degree of purity was attainable by the electrolytic processes. In addition to the above, the following analyses made in the Pittsburgh Testing Laboratory show the quality of commercial aluminium which has been put on the market in recent years : Com- Graphi- Alumin- bined toidal Second Quality Metal. ium. Silicon. Silicon. Iron. Copper. Sodium. Lead. Pittsburgh Reduction Co 9S-00 1.50 1.35 2.00 0.07 0.04 0.03 Society Anon, de TAluminium .. 95.00 0.90 i.oo 3.00 0.05 o.oi 0.04 Alliance Aluminium Co 95-00 0.90 0.75 3.25 0.02 0.07 o.oi The Aluminium Co., Limited . . . 95.00 0.85 0.75 3.00 o.io 0.30 nil The Al. LA. G., Switzerland ... 95.00 1.75 1.15 2.00 o.ci 0.07 nil " " " ... 94.15 1.02 0.54 2.80 1.49 — — First Quality Metal. Pittsburgh Reduction Co 97.00 1.55 1.25 0.13 0.03 0.02 0.02 Soc. Anon, de I'Al 97.00 0.90 0.82 1.20 0.04 o.oi 0.03 Alliance Al. Co., Ltd 97.00 0.95 0.53 1.45 0.01 0.05 o.oi The Al. Co., Limited 97.00 0.75 0.52 1.55 0.03 0.15 nil Pittsburgh Reduction Co 98.00 1.30 0.60 0.07 o.oi o.oi o.oi Soc. Anon, de I'Al 98.00 0.71 0.35 0.90 o.oi o.oi 0.02 Alliance Al. Co., Ltd 98.00 0.90 0.29 0.75 o.oi 0.04 o.oi The Al. Co., Limited 98.00 0.90 0.23 0.80 0.02 0.05 nil Pittsburgh Reduction Co 98.52 0.42 0.72 0.05 0.06 nil 0.04 " " " 99.00 0.80 0.15 0.03 O.OI nil O.OI Soc. Anon, de I'Al 99-00 0.35 0.13 0.50 nil o.oi o.oi Alhance Al. Co., Ltd 99.00 0.31 0.20 0.45 nil 0.03 o.oi The Al. Co., Limited 99-°° °-^l °-'S o-5S °-°2 o.oi nil Pittsburgh Reduction Co 99-20 041 0.34 0.05 nil nil nil Alliance Al. Co., Ltd 99- H o-23 0.17 0.46 nil nil nil Pittsburgh Reduction Co 99-34 °A° 0-21 0.05 nU nil nil The makers represented above are : The Pittsburgh Reduction Company. New Kensington, Pa. 56 ALUMINIUM. The Alliance Aluminium Company, Limited. Wallsend-on- Tyne, England. The Aluminium Company, Limited. Oldbury, near Birming- ham, England. The Societe Anonyme de I'Aluminium. Nanterre, France. The Aluminium Industrie Actien-Gesellschaft. Neuhausen, Switzerland. The second, third and fourth of these firms used the sodium process, the others the electrolyic methods. It is at once seen that for metal with the same proportion of aluminium, that made by the electrolytic processes contains less iron, but more silicon, than that made by the sodium processes ; there is no observable regularity in the proportion of combined and graph- itoidal silicon to the amount of iron. On an average, the graph- itoidal silicon is about one-third to two-thirds of the combined silicon. Rammelsberg (Kerl's Handbuch) investigated the question of the different states of silicon in aluminium. He found in aluminium reduced from cryolite by sodium in a porcelain cru- cible, that on treatment with hydrochloric acid, the combined silicon changes into silica, or part escapes as silicon hydride, while the graphitoidal silicon remains as a black residue. Two analyses gave him the following results : 1.. 2. Silicon obtained as silica 9.55 1.85 Free silicon 0.17 0.12 Silicon escaping in SiH'' 0.74 0.58 In aluminium containing 6.20 per cent, of total silicon, ana- lyzed in the Pittsburgh Reduction Co.'s laboratory, 3.85 per cent, was graphitoidal silicon. In another specimen, contain- ing 5 -30 per cent, of total silicon, 2.40 per cent, was graphi- toidal. An experiment, made at the Pittsburgh Testing Laboratory, to determine the influence of quick or slow cooling on the con- dition of the silicon, showed that the chilled metal contained, slightly more of the silicon in the graphitoidal state and less in the combined state than metal slowly cooled. PHYSICAL PROPERTIES OF ALUMINIUM. 57 This result is the opposite of the behavior of carbon in iron, and it is found, as might be expected, that no appreciable dif- ference in hardness can be detected between the surfaces of ingots cast in chills and those cast in hot moulds. M. Dumas found that aluminium usually contains gases, about which he makes the following statements:* On submit- ting aluminium in a vacuum to the action of a gradually increas- ing temperature up to the softening point of porcelain, and letting the mercury pump continue acting on the retort until it was completely exhausted, considerable quantities of gas were withdrawn. The liberation of the gas from the metal seems to take place suddenly towards a red-white heat. 200 grammes of aluminium, occupying 80 c.c, gave 89.5 c.c. of gas, meas- ured at 17° and 755 mm. pressure. The gas consisted of 1.5 c.c. carbonic acid, and 88 c.c. hydrogen. Carbonic oxide, nitrogen and oxygen, were absent. The author has observed that molten aluminium will absorb large quantities of gas. On passing sulphuretted hydrogen into the melted metal for about twenty minutes some aluminium sulphide was formed, while the metal appeared to absorb the gas. On pouring, the metal ran very sluggishly, with a thick edge, but when just on the point of setting, gas was disengaged so actively that the crackling sound could be heard several feet away, and the thick metal became suddenly quite fluid and spread over the plate in a thin sheet. The gas disengaged seemed by its odor to contain a large proportion of sulphur- etted hydrogen, although free hydrogen may have been pres- ent in it. Le Verrier has established the presence of carbon in small amount in commercial aluminium.! Taking a large quantity of metal and treating it with a current of hydrochloric acid or hydriodic acid gas, entirely free from oxygen, there remains a grey residue. This, treated with dilute hydrochloric acid, gives a very light residue of amorphous carbon, of a maroon color, * Comptes Rendus, xc, 1027 (1880). t Comptes Rendus, July, 1894, p. 14. 58 ALUMINIUM. ■which, on being separated out, can be entirely burnt to car- bonic acid gas in a current of oxygen. This carbon does not contain a trace of graphite ; it is entirely amorphous. It is easiest estimated by dissolving ten grammes of aluminium in a concentrated solution of caustic potash, washing the residue with water, drying, burning in a current of oxygen, and weigh- ing the carbonic acid formed. In three specimens tested there were found 0.104, O.108 and O.080 per cent, of carbon respect- ively. To determine the effect of carbon on the physical prop- erties of aluminium, he melted best quality metal, cast a specimen ingot, and then dissolved in it some crystallized aluminium carbide, AhCs (for method of making this see Chap- ter XIV) . A specimen of the carburized metal was then cast and tested. The results were as follows; the weights being per square millimetre of section : Cast Specimens. Elastic Limit. Breaking Load. Elongation. Pure aluminium — 1 1. 1 kilos. 9 per cent. Carburized aluminium — 6.5 " 5 " — 8.6 " 3 " Rolled Specimens. Elastic Limit. Breaking Load. Elongation. Pure aluminium, hard 23 kilos. 25.0 kilos. 2.0 per cent. " " annealed 8 " 14.0 " 23.0 " Carburized aluminium, hard 20 " 20.79 " 2.5 " " " annealed 7.7 " 13.80 " 26.5 " It would appear that the cast metal shows the greatest de- terioration by the presence of carbon. Le Verrier also proved the presence of traces of nitrogen in commercial aluminium by passing the hydrogen evolved during solution in dilute caustic potash into a Nessler solution, which then gives the ammonia reaction. To determine the exact effect of nitrogen, some aluminium was melted and a current of nitrogen passed into it. The metal became saturated with the gas, and showed the following diminution in strength : PHYSICAL PROPERTIES OF ALUMINIUM. 59 Cast Specimens. Elastic Limit, Breaking Load. Elongation. Pure aluminium 7.5 kilos. i I.I kilos. 9 per cent. Aluminium saturated with nitrogen 6.5 " g.6 " 6 " Le Verrier considers that nitrogen and carbon occur in alu- minium in the state of aluminium nitride and carbide re- spectively, dissolved in the excess of aluminium. The same investigator has discovfered by the microscope, in the residue left by dissolving in hydrochloric acid, very small, sharp crys- tals of boron carbide, the boron coming from the boric acid used in agglomerating the carbon electrodes. A little amor- phous alumina is also sometimes to be found. Color. Deville : The color of aluminium is a beautiful white with a slight blue tint, especially when it has been strongly worked. Being put alongside silver, their color is sensibly the same. However, common silver, and especially that alloyed with copper, has a yellow tinge, making the aluminium look whiter by comparison. Tin is still yellower than silver, so that alu- minium possesses a color unlike any other useful metal. Mallet: Absolutely pure aluminium is perceptibly whiter than the commercial metal ; on a cut surface very nearly pure tin- white, without bluish tinge, as far as could be judged from the small pieces examined. The purest-looking aluminium examined by the author is that made by Grabau. On a fresh fracture it is absolutely ■white, but on long exposure to the air it takes a faint, almost imperceptible bluish tint. On a cut surface it has the faintest suspicion of a yellow tint, not so decided as the yellowish color of pure tin. Ordinary commercial aluminium is bluish on a fresh fracture, the tint being deeper the greater the amount of impurities it contains. A specimen with 10 per cent, of silicon and 5 per cent, of iron was almost as blue as lead. It is my belief that a very small percentage of copper closes the grain -and whitens the fracture a little; I have also found that chilling 6o ALUMINIUM. suddenly from a high temperature has the same effect. Wheir ingots of aluminium are exposed a long time to damp air, the thin film of oxide forming on them gives a more decided bluish cast to the metal, since the coating is perfectly snow-white and hence, by contrast, heightens the bluish tint of the metallic background. Mourey recommended removing this discolora- tion by placing the articles first in dilute hydrofluoric acid, 1,000 parts of water to 2 of acid, and afterwards dipping in nitric acid. The oxide would thus be dissolved and the original color restored. Pure aluminium possesses to the highest de- gree that property expressed best by the French term " eclat." It is rather difficult to see why the blue tint should be more prominent after the metal has been worked, yet I think two reasons will explain this phenomenon ; first, aluminium is not a hard metal, and on polishing or burnishing, particles of dirt or foreign substances are driven into the pores of the metal,, thereby altering its color slightly ; second, any metal looks whiter when its surface is slightly rough than when highly polished, in the latter case it being as much the reflected color of the general surroundings as the color of the metal itself which is seen. I have never seen any highly polished white metal which did not look bluish, especially when reflecting out- door light. I think this explains why opera-glasses, rings, jewelry, etc., generally look bluer than the bar or ingot-metal from which they are made. Aluminium takes a very beautiful mat, which keeps almost indefinitely in the air, the surface thus slightly roughened ap- pearing much whiter than the original polished surface. Alu- minium can be polished and burnished without much difficulty if attention is given to a few particulars which it is necessary to observe. (For methods of poHshing, etc., see Chapter XIII.) Extremely thin films of aluminium are fine violet-blue by transmitted light. Fracture. A cast ingot of purest aluminium has a slightly fibrous structure, a section y^ inch thick bending twenty degrees or PHYSICAL PROPERTIES OF ALUMINIUM. 6 1 SO from a straight line when sharply bent before showing cracks at the outside of the turn. The fracture of such an ingot is uneven, rough, and very close, often showing a curious semi- fused appearance, as if it had been already exposed to heat and the sharpest points melted down. However, only the purest varieties show these peculiarities. Metal containing 96 to 97 per cent, of aluminium begins to show a crystalline structure, breaks short, and with a tolerably level surface. Metal less than 95 per cent, pure shows large shining crystal surfaces on the fracture, the smaller crystals being on the outside of the ingot where it has been cooled most quickly, while in the cen- tre the crystalline surfaces may be as large as tV inch in diameter. A specimen containing only 85 per cent, of alumin- ium broke as short as a bar of antimonial lead, with a large granular, crystalline surface. Working the metal increases its fibrousness greatly, the sec- tion of a square rolled bar of good metal looking very much like that of a low-carbon steel. Hardness. The purest aluminium is distinctly softer than the commer- cial ; estimated on the scale of hardness proposed by Mohs it would be written as about 2.5, that is, a little harder than can be scratched by the nail. It is not so soft as pure tin. The presence of impurities, however, rapidly increases the hardness. While 99 per cent, aluminium can be cut smoothly with the knife and shavings turned up almost as with pure tin, yet 95 per cent, metal can hardly be cut at all ; the shavings break off short, and a fine grating is felt through the blade. Aluminium becomes surface hardened by cold working. Castings of aluminium drop-forged cold, in dies, are made sensibly harder and thus adapted for standing more wear. Cold drawing or rolling gives to it nearly the hardness of brass. In a drop test to investigate this quality made in the Pittsburgh Testing Laboratory, the following comparative results were reached : 62 ALUMINIUM. Hardness. Aluminium, rolled 62 Aluminium, cast 47 Brass, rolled 86 Brass, cast 71 Copper 100 Experience in testing various specimens of commercial alu- minium with the knife will, I am sure, enable a person to be- come quite skillful in determining the purity and in separating different grades from each other. Taking this test in connec- tion with the breaking and surface of fracture, it appears to me that these indications are as significant and can be made of as much use as the corresponding tests for iron, steel, and other metals. Mr. Joseph Richards, the author's father, having had many years' experience in testing lead, tin, zinc, and similar metals, in which the knife-blade has been put to good service, has been able with very little practice to arrange a number of specimens of aluminium correctly according to their purity sim- ply by noting carefully the way they cut and the color of the cut surface. These tests will in the future, I am sure, be of great use to those handling aluminium on a large scale, es-- pecially in the works where it is produced. Specific Gravity. Mallet: The specific gravity of absolutely pure aluminium- was carefully determined at 4° C, and the mean of three closely agreeing observations gave 2.583. Commercial aluminium is almost always heavier than this, but the increase is not in direct proportion to the amount of impurities present. There are two reasons why this last state- ment is correct; first, we cannot say what expansion or con- traction may take place in forming the alloy; second, while- most of the impurities which occur are much heavier than alu- minium, yet silicon, the most frequent of all, has a specific gravity of only 2.34 (Deville's determination), and therefore acts in the opposite direction to the other impurities, though. PHYSICAL PROPERTIES OF ALUMINIUM. 63 not to SO great an extent. The following analyses and specific gravities may give some information on this point: — Analysis. Specific Gravity. Aluminium. Silicon. Iron. Observed. Calculated. 97.60 0.60 1.80 2-73S 2.61 (2.64) 95-93 2.01 2.06 2.800 2.61 (2.69) 94.16 4-36 1.48 2.754 2.59 (2.74) 78.- 16.— 4-— 2.85 2.66 It is seen in each case that the calculated specific gravity is. much less than the observed, which would show contraction in volume by alloying. Indeed, this is a prominent characteristic of aluminium alloys, aluminium often taking up several per cent, of its weight of another metal without its volume being increased, the particles of the other metal seeming to pass be- tween those of the aluminium ; thus probably accounting for the extraordinary strength and closeness of many of the alumin- ium alloys. This subject is treated more at length in the chap- ter on alloys. We can see the large contraction taking place by inspecting the numbers in parentheses under the heading "Calculated." These are computed on the supposition that the volume of the impure aluminium is equal to that of the pure aluminium entering into it. As these numbers are also- less than the observed specific gravities, the extraordinary fact is shown that aluminium can absorb several per cent, of iron and silicon and yet will decrease in volume in doing so. The remarks thus far made are based on the gravity of cast metal. Aluminium increases in density by being worked : De- ville states that metal with a specific gravity of 2.56 had this increased to 2.67 by rolling, which, he says, may explain the diflerences existing in its properties after being annealed or worked. He remarked further that heating this rolled metal to 100°, and cooling quickly, changed its specific gravity very little, lowering it to 2.65. I have observed that on heating a piece of aluminium almost to its fusing point and suddenly chiUing it in water, its specific gravity was lowered from 2.73 to 2.69. 64 ALUMINIUM. Experiments made by Prof. J. W. Langley with aluminium 98.52 per cent, pure, the rest being mostly silicon, gave its specific gravity as follows : Sample sawn from centre of a cast ingot 2.587 Same, annealed 2.692 Rolled into sheet 0.0625 inch thick 2.710 Stamped into medals 2.725 The low specific gravity of aluminium, when compared with that of the other metals, is (in the words of a recent lecturer) " the physical property on which our hopes of the future use- fulness of aluminium chiefly rest." The following table will facilitate this comparison : Specific Gravity. Alumin- Founds in a Kilos in .1 Water = I. ium =: i. cubic foot. cubic meter. Platinum 21.5 8.3 1344 21,500 Gold 19.3 7.4 1206 19,300 Lead 11.4 4.6 712 11,400 Silver 10.5 4.0 656 10,500 Copper 8.9 3.5 557 8,900 Iron and steel 7.8 2.8 487 7,800 Tin 7.3 2.7 456 7,300 Zinc 7.1 2.7 444 7,100 Aluminium 2.6 i.o 163 2,600 In comparing the price of aluminium with that of a metal which it might replace, for purposes where the bulk of the arti- cle is fixed, it is of first importance to take this low specific gravity into account. When we come to consider closely, we find that almost every article of use or ornament is wanted of a fixed size, and therefore the real basis of comparison of prices is that of a fixed volume of the metal rather than a fixed weight. To facilitate this comparison, I give below the actual market prices of one pound weight of the common metals, with the prices of equal volumes: PHYSICAL PROPERTIES OF ALUMINIUM. 65 Value of Relative cost Value of Relative cost I pound, of equal weights, i cubic foot, of equal volumes. Silver jSio.oo 2850 ;J656o.oo 1 1430 Nickel 0.50 140 279.00 468 Aluminium 0.35 100 S7-S0 10° German silver 0.30 85 167,00 290 Tin 0.15 43 68.50 120 Bronze 0.15 43 79.00 137 Brass 0.12 34 61.75 107 Copper o.io 28 55.75 97 Lead 0.04 11 28.50 50 Zinc 0.04 II 17-75 3' Steel 0.02 6 9.75 17 Cast Iron o.oi 3 5.00 8 It is therefore evident, that for almost all uses to which aluminium is applicable, there are only five of the common metals which are cheaper, viz., copper, lead, zinc, steel and cast- iron. When it is further remembered that the cost of the metal alone usually forms only a small part of the value of the finished article, it can be further asserted that there should be only a trifling diflference between the cost of an article made in alu- minium and one of tin, bronze, brass or copper. The sole reason why aluminium articles are not sold more cheaply at present, lies in the fact that they are not made and sold in such large quantities ; the increase of the aluminium industry will therefore ensure lower prices for aluminium goods. Fusibility. Deville : Aluminium melts at a temperature higher than that of zinc, lower than that of silver, but approaching nearer to that of zinc than silver. It is, therefore, quite a fusible metal. Mallet : It seems that pure aluminium is a Httle less fusible than the commercial metal. Pictet determined the melting point to be 600°, Heeren about 700°, while Van der Weyde placed it as high as 850°. On a sample containing 0.5 per cent, of iron, Carnelly determined the melting point at 700° ; with 5 per cent, of iron it did not fuse completely until 730°. The discordance between these various experimenters lies chiefly in the errors of the pyro- S 66 ALUMINIUM. meters used. Since the perfection of the electric pyrometer by Le ChateHer, the melting point of the purest aluminium has been repeatedly observed as very close to 625°. This figure is probably correct within 5°. A very small admixture of iron and silicon lowers the melt- ing point. Le Chatelier found with a metal containing 1.50 per cent, silicon and 0.75 per cent, iron, the melting point 619°- A larger quantity of either of these elements quickly operates in the other direction, and prevents fluid fusion until a temperature above 625° is reached. Spring has determined that aluminium powder flows to a solid mass at a pressure of 38 tons per square inch, at ordinary temperatures. Volatilization. Deville : Aluminium is absolutely fixed, and loses no part of its weight when it is violently heated in a forge fire in a carbon crucible. This statement was made in 1859, and can still be accepted as true as far as ordinary furnace temperatures are concerned. But, with the use of the electric furnace, temperatures have been attained at which aluminium does sensibly volatilize. In Cowles Bros, electric furnace it is stated that the aluminium is almost all produced as vapor and as such is absorbed by the copper or iron present ; when these are not present it is found condensed in the cooler upper part of the furnace. A similar experience has been met in other electric furnace processes, so that the volatilization of aluminium at these extreme tempera- tures may be accepted as a fact. Aluminium vapor has been recently produced in an electric furnace in large enough amounts to determine that it is of a green-blue color. Odor. The purest aluminium has no perceptible odor, but metal containing i per cent, or more of silicon exhales the odor of silicon hydride, exactly the same odor as proceeds from cast PHYSICAL PROPERTIES OF ALUMINIUM. 6^ iron. Second quality commercial aluminium gives this smell quite strongly, but in the present first quality metal it is difficult to detect it except by smelling immediately after a brisk rubbing. Taste. The same remark may be made regarding taste as of the odor. The purest metal has no taste ; the impure tastes like iron, but not so strongly. Magnetism. Deville, as also Poggendorff and Reiss, state that aluminium" is very feebly magnetic. It must be remembered, however, that they tested metal made by the sodium process, which almost invariably contained iron. Prof. Frank Very, of the Allegheny Observatory, Allegheny, Pa., finds aluminium with only a trace of iron to be absolutely non-magnetic. With 0.05 per cent, of iron, none could be ob- served. An ingot containing 1.5 per cent, iron showed faint polarity, while with 2 per cent, the polarity was very decidedly observed. Since the present first quality commercial aluminium contains less than 0.2 per cent, of iron, and frequently only 0.05 per cent., we may observe that this is less than is usually found in commercial brass, bronze or german-silver, and for this reason, as well as its other valuable properties, aluminium answers very well for compass boxes or cases, or parts of electrical instru- ments where non-magnetic properties are desired. Sonorousness. Deville: "A very curious property, which aluminium shows the more the purer it is, is its excessive sonorousness, so that a bar of it suspended by a fine wire and struck sounds like a crystal bell. M. Lissajous, who with me observed this prop- erty, has taken advantage of it to construct tuning forks of aluminium, which vibrate very well. I also tried to cast a bell, which has been sent to the Royal Institution at London at the -68 ALUMINIUM. request of my friend Rev. J. Barlow, vice-president and secre- tary of the institution. This bell, cast on a model not well adapted to the qualities of the metal, gives a sharp sound of considerable intensity, but which is not prolonged, as if the clapper or support hindered the sound, which, thus hindered, becomes far from agreeable. The sound produced by the in- gots is, on the contrary, very pure and prolonged. In the ex- periments made in Mr. Faraday's laboratory, this celebrated physicist has remarked that the sound produced by an ingot of aluminium is not simple. One can distinguish, by turning the vibrating ingot, two sounds very near together and succeeding each other rapidly, according as one or the other face of the ingot faces the observer." The bell referred to above was 20 kilos in weight and 50 centimetres in diameter, but as Deville admits, its sound was not pleasing, and a contemporary writer, evidently not very enthusiastic in sounding the praises of aluminium, said that " while the bell was highly sonorous, yet it gave a sound like a cracked pot." I have not heard that any large bell has since been cast, but it is certain that the metal in bars has a highly musical ring. Faraday's observation has also been verified, for a recent lec- turer suspended by one end a bar 6 feet long 31^ inches wide, and I y^ inches thick, and on striking it a prolonged vibration ensued, two notes being recognized, A sharp and D sharp, the latter more subdued. Within the last few years aluminium has been extensively employed for sounding boards in public hails, the sounding boards of pianos, and even for the construction of horns and violins. The sounding board in the Lyceum Hall, New York city, is an example. The particular advantage is, its not being affected by a moist atmosphere. Dr. Alfred Springer, of Cin- cinnati, in speaking of its use for sounding boards says,* " It .differs from all other metals in the absence of the comparatively * Trans. A. A. Adv. Science, 1891, vol. 40, p. 182. PHYSICAL PROPERTIES OF ALUMINIUM. 69 continuous and uniform higher partial tones, which give in other metals the tone-color called " metallic," and further, that it also possesses an elasticity capable of sympathetic vibration uniformly through a wide range of tone-pitch, which renders it in this respect superior to wood." Dufour has measured the velocity of sound in aluminium at 4950 metres per second, almost the same figure as for steel. Crystalline Form. Deville : " Aluminium often presents a crystalline appearance when it has been cooled slowly. When it is not pure, the little crystals which form are needles, and cross each other in all directions. When it is almost pure it still crystallizes by fusion, but with difficulty, and one may observe on the surface of the ingots hexagons which appear regularly" parallel along lines which centre in the middle of the polygon. It is an error to conclude from this observation that the metal crystallizes in the rhombohedral system. It is evident that a crystal of the regu- lar system may present a hexagonal section; while on the other hand, in preparing aluminium by the battery at a low temperature, I have observed complete octahedrons which were impossible of measurement, it is true, but their angles appeared equal." By slowly cooling a large body of melted aluminium and pouring out the fluid interior, distinct octahedrons may be observed. Elasticity. Cast aluminium is not very elastic; it may be likened in this respect to cast silver. When worked, however, it becomes more rigid and elastic. Mallet remarked that absolutely pure aluminium seemed to be less hardened by hammering than ordinary commercial metal. Cast aluminium stiffens up very quickly in rolling or drawing, and the strains set up in the metal can be removed by an yo ALUMINIUM. annealing, which consists in heating the metal to an incipient red heat and then either allowing to cool slowly, or leaving a few minutes at that heat and then cooling quickly by plunging into water. Metal thus treated becomes very soft and pliable, hardly any more elastic than lead, and will stand considerable working before it again becomes stiff and elastic. The presence of 2 to 5 per cent, of copper, nickel, silver, German-silver or titanium increases very greatly the elasticity of aluminium without increasing noticeably its specific gravity or impairing its malleability. Tensile and Compressive Strength. W. H. Barlow* was the first to carefully test the tensile strength of aluminium. He used a rolled bar one-quarter inch square. With -a test piece two inches long, the tensile strength was found to be 26,800 pounds per square inch, with elongation before breaking of 2.5 per cent. Kamarschf tested aluminium wire, and obtained an average of 12.5 kilos per square millimetre, equal to nearly 18,000 pounds per square inch. This wire must have been annealed, while the bar tested by Barlow was worked stiff before testing. Mr. Spilsbury, of the Trenton Iron Co., obtained with alu- minium wire of one-sixteenth inch diameter a tensile strength of 62,300 pounds per square inch, the wire having been drawn with one annealing from a wire-rod one-sixth inch in diameter. The same wire made 47 bends at a right angle before breaking. A most valuable series of mechanical tests of aluminium have been made by the Pittsburgh Reduction Company, and are copied as follows| : * Rpt. British Assoc. Adv. Science, 1882, p. 668. fDingler, Vol. 172, p. 55. J Transactions Am. Inst. Mining Engineers. Vol. XVIII., p. 528 (1890). PHYSICAL PROPERTIES OF ALUMINIUM. Tensile Tests. n No. I quality commercial metal, averaging over 98 per cent. pure. Ordinary castings of over \ inch sectional area, as cast .... Same, annealed Same castings, hardened by drop forging cold Rolled bars, left hard Same, annealed Hammered bars, left hard Same, annealed "Wire i to J inch diameter, as drawn Same, annealed Wire y\ to -^^ inch diameter, as drawn Wire ^ to ^ J ^ inch diameter, as drawn Same, annealed Plates to \ inch thick, as rolled Same, annealed Sheets \ to -^-^ inch thick, as rolled Same, annealed Sheets ^V '° ttss '^^'^ 'C!\\<^, as rolled Same, annealed •a 3 § 6,132 6,600 10,000 16,000 13.870 14,630 14,000 12,000 10,870 32,000 26,000 21,000 9.300 8,500 12,500 10,700 13.500 11,000 c »H 4) u ■a p-.s rt ^ rt 15,640 17,100 24,000 32,500 25,000 24,120 22,000 24,500 22,830 54,000 49,000 33,000 22,740 17.740 25,000 21,070 27,500 23,000 •a . & O a a 4) j-j • "S "> So 8.66 15.00 18.00 42.00 49.11 3S-H 43.00 58.46 65-57 68.00 54.00 62.00 12.40 13-73 35-50 39.00 40.00 43-50 3,000 3,500 3.000 6,000 6,000 5.500 5,500 4,500 4,500 12,000 10,000 7,000 4,000 4,000 4.500 4,500 4,500 4,500 72 ALUMINIUM. Compressive Tests. Same metal is in above tensile tests, about 98 per cent. pure. Ordinary casting, as cast Same, annealed Same, hardened by drop forging. Rolled bars, left hard Same, annealed Hammered bars, left hard Same, annealed Metal containing 4.5 per cent, silicon and 1.5 per cent, iron, casting, unannealed Metal containing 1.14 per cent, silicon and 0.05 per cent, iron, castings, unannealed Same, larger test-piece .d DA . •S.J- g^^ •= 0. c "»-S a e »■" a-" 0, a i^ u 31-50 37-35 30.00 0.38 4.00 10.27 96.00 The figure last given includes the loss sustained in polishing the metal to its original appearance before immersion. It re- sults from these tests that a sheet of aluminium one millimetre thick, if left standing in concentrated nitric acid, would sustain constant immersion at ordinary temperatures for 3600 days (Lunge), 43 days (Le Roy), or 14 days (Richards), if taken out every day and polished bright. Concerning the use of aluminium in the Grove battery, which is not a constant battery, but only used to give a strong cur- rent for a short time, aluminium sheet one millimetre thick will last a long time and cost only a fraction as much as thin platinum. Hydrochloric Acid. This acid attacks commercial aluminium rapidly, quicker when hot than when cold, and the concentrated quicker than the dilute. The very pure metal, however, is attacked slowly, showing that, as with sulphuric acid, the galvanic action of the impurities keeping the aluminium free from a protecting layer •of gas, has a great influence on the resistance to acids. Gase- ous hydrochloric acid attacks the metal even at a very low .temperature. The presence of silicon, particularly, increases the facility 92 ALUMINIUM. with which the metal is attacked. When silicon is present, the graphitic silicon remains behind as a black residue, while the combined silicon partly forms silica and partly escapes as sili- con hydride (SiHi), having a very disagreeable smell. When the amount of combined silicon is small, almost all of it may thus escape. In analyzing aluminium, this loss is prevented by keeping the acid well oxidized by bromine water, which pre- vents the formation of the gas. On evaporating to dryness,, after solution, and taking up with water, the graphitoidal sili- con remains as a black crystalline residue, while the combined silicon has all been changed to white silica. These can be separated by washing with hydrofluoric acid, which dissolves the silica but leaves the silicon unattacked. If a small amount of hydrochloric acid is present in a mix- ture of acids, it leads the attack on the metal, and the other acids form aluminium salts by reacting on the aluminium chloride formed. Hydrobromic, hydriodic and hydrofluoric acids act similarly to hydrochloric. Aluminium fluoride, how- ever, is not so soluble in water as the other halogen salts, and the attack by hydrofluoric acid is therefore hindered by the formation of an insoluble coating on the aluminium when the solution passes a certain degree of concentration. In an experiment by the writer, best commercial rolled alu- minium was put into cold, dilute (3 per cent.) hydrochloric acid. It was some time before any action was observable, and then it was very slow. It lost, after cleaning, at the rate of 5S grammes per square metre of surface per day, which was only a little over half as much as was dissolved by cold, concentrated nitric acid in the same time. A piece of the same metal, how- ever, alloyed with three per cent, of nickel was rapidly attacked under these conditions, and over thirty times as much of it was dissolved in a given time, thus showing strikingly the influence of a small amount of impurity. Organic Acids, Vinegar, Etc. Deville : " Weak acetic acid acts on aluminium in the same CHEMICAL PROPERTIES OF ALUMINIUM. 93 way as sulphuric acid, i. e., in an inappreciable degree or with extreme slowness. I used for the experiment acid diluted to the strength of strongest vinegar. M. Paul Morin left a plaque of the metal a long time in wine which contained tartaric acid in excess and acetic acid, and found the action on it quite in- appreciable. The action of a mixture of acetic acid and com mon salt in solution in pure water on pure aluminium is quite different, for the acetic acid replaces a portion of the chlorine existing in the sodium chloride, rendering it free. However, this action is very slow, especially if the aluminium is pure." " The practical results flowing from these observations deserve to be clearly defined, because of the applications which may be made of aluminium to culinary vessels. I have observed that the tin so often used and which each day is put in contact with common salt and vinegar, is attacked much more rapidly than aluminium under the same circumstances. Although the salts of tin are very poisonous, and their action on the economy far from being negligible, the presence of tin in our food passes un- perceived because of its minute quantity. Under the same circumstances aluminium dissolves in less quantity; the acetate of aluminium formed resolves itself on boiling into insoluble alumina or an insoluble sub-acetate, having no more taste or action on the body than clay itself. It is for that reason and because it is known that the salts of the metal have no appre- ciable action on the body, that aluminium may be considered as an absolutely harmless metal." The low price of aluminium has within the last two years rendered possible this application to culinary utensils foreseen by Deville, and has led to several investigations as to its resist- ance to the acids and salts liable to be met with in food. Two German pharmacists, Lubbert and Roscher, conducted tests of this kind in 1891, but their results were only qualitative, not quantitative, and they made the mistake of using thin aluminium foil, which averages only o.ooi inch thick, instead of heavier sheet. The result was that they found their thin foil totally dissolved by two days immersion in oxalic acid (1,5 94 ALUMINIUM. and lO per cent.), gallic acid (2 per cent.), and corrosive sub- limate (i per cent.) ; and by four days constant immersion in I, 5 and 10 per cent, solutions of formic, acetic, butyric, lactic,, tartaric and citric acids, pure oleic acid, 10 per cent, solutions of palmitic or stearic acids, in 5 per cent, solutions of carbolic acid, 4 per cent, solution of boric acid, and in pure red wine, white wine, coffee and tea. It has been found, however, that because of its thinness alu- minium foil does not resist corrosion as does the heavier sheet- metal, and while the above results may be strictly true for foil 0.00 1 inch thick, yet ordinary sheet aluminium is not attacked to anything like such an extent. Culinary utensils are made of sheet at least i millimetre (0.04 inch) thick, and tests of mate- rial of this thickness made by subsequent investigators have given very different results. Balland* conducted tests for several months, and found that air, water, wine, beer, cider, coffee, milk, oil, butter, fat, urine, saliva and damp earth have less action on aluminium than on iron, copper, lead, zinc, or tin. Vinegar and salt together at- tack it, but so slightly as not to prevent its use for cooking; a sheet only lost 1.3 per cent, of its weight in vinegar, and 0.2 per cent, of its weight in a 5 per cent, salt solution after four months' immersion. Ruppf states that he has kept different kinds of liquid and semi-solid food in aluminium vessels for 4 to 28 days, at the ordinary temperature, and found the metal unaltered. The metal used contained 0.30 per cent, of iron, 0.08 silicon and 99.66 aluminum. Prof. Geo. Lunge, | of Zurich, has made a most careful and systematic investigation of this subject. Assisted by Ernst Schmid, he made the following series of tests ; ordinary com- mercial sheet aluminum from Neuhausen was used. It ana- lyzed : * Comptes Rendus, 1892, Vol. 114, p. 1536. t Chronique Industrielle, June 12, 1892. I Zeitschrift fiir angewandte Chemie, January, 1892. CHEMICAL PROPERTIES OF ALUMINIUM. 95 Aluminium 99.20 per cent, (by difference) Combined silicon 0.44 " Graphitic " o.i I " Iron 0.25 " Copper trace. The sheet was i minimetre thick, and was cut into strips of a fixed size. These were first carefully cleaned by caustic soda and sulphuric acid, and then immersed six days in the liquids at the ordinary temperature, each liquid being tested twice to guard againt mistakes. The following are their results, ex- pressed as the weight dissolved per day in milligrammes per square metre of surface exposed : Loss of weight per day in milligrammes per square Liquid. i metre of surface. Ordinary claret 47.3 " hock 51.2 Brandy 18.0 Pure 50 per cent, alcohol 10.2 Tartaric acid, 5 per cent, solution 28.2 " '■ I " " 43.0 Acetic " S " " .64.2 " " I " " 73.0 Citric " 5 " " 35-8 " I " " 31-7 Lactic " 5 " " ■■■■■ 79-5 Butyric " 5 " " 21.8 Carbolic " 5 " " 3-8 " " 1 " •• 8.2 Boric " 4 " " 29.5 Salicylic " I4 " " 105.8 Coffee (poured hot) 8.3 Tea " 00 Beer o-o The aluminium strips used showed outward evidences of corrosion in only a few places ; only in the case of the salicylic acid solution had the metal lost its bright surface and become dull. In the case of brandy and alcohol, where the quantitative action was very slight, the surface of the aluminium showed a few fungus-like excresences, probably formed by alumina, caused by accidental flaws in the sheet. In the case of a wine 96 ALUMINIUM. rich in tannin, these spots are liable to be darkened by the in- fluence of the trace of iron dissolved from the aluminium, form- ing tannate of iron, but the amount thus formed is infinitesmal. The weights dissolved are so extremely small, that it may be calculated that a canteen holding a litre could be kept full of the strong acetic acid for 55 years before losing half its weight. Lunge and Schmid conclude that, " the action of coffee, tea and beer is practically zero ; that of acids and acid liquids is more pronounced, but in the worst case too slight to cause any alarm whatever. Nor is there the slightest danger of any in- jurious action on the human body by such traces of aluminium compounds, seeing that our food contains very much more than these ; in fact, they could not act injuriously unless quantities hundreds of times larger were regularly entering the stomach." The only criticism we have to make of this valuable investiga- tion is that the solutions should have been tested hot, even boiling, as well as cold. While it is perfectly true, as remarked by a Washington lady, that " we hope never to have occasion to serve our families with poisoned soups or salicylic or boracic acid stews," yet if Lunge had made the hot-liquid tests we should, at least, have known the worst that could possibly hap- pen to the aluminium culinary utensils. Happily, actual experience has settled all these questions. An aluminium sauce-pan used in the writer's family constantly for two years, which has been used for boiling milk, cooking oatmeal and vegetables, stewing meats and preserving several kinds of fruits, lost less than one-quarter ounce in the whole two years, an average of less than 15 milligrammes per day per square metre of surface exposed, including frequent cleaning. I have calculated that at this rate the utensil will become a fam- ily heirloom unless accident overtakes it, for it could stand this rate of wear for over a century before losing half its weight. Other experiences equally as striking could be cited, and no better proof of the suitability of aluminium for culinary utensils could be wished. The German Minister of War, after thorough experiments by an army commission, has adopted aluminium CHEMICAL PROPERTIES OF ALUMINIUM. • 9/ canteens and drinking cups for the soldiers, and entire sets of cooking utensils for use in the officers' quarters. It is the writer's opinion that within a short time the larger part of all the aluminium made will be needed to supply the great demand which will arise for these culinary utensils. Sodium Chloride. Common salt does not, when molten, corrode aluminium, so that it forms a good flux to melt the metal with. It does not possess the property, like fluorspar, of dissolving alumina, but acts simply by its fluidity to give a clean melt. A solution of common salt acts very feebly on aluminium. A strip of rolled aluminium immersed in a three per cent, solu- tion at 27° C. lost weight at the rate of 394 milligrammes per day per square metre of surface (Hunt). The writer found a corresponding loss of 400 milligrammes per day on sheet im- mersed in a strong brine kept at 65° C. (150° F.) At that rate it would take nine years' constant immersion to entirely dissolve a sheet one millimetre thick. When an acid is present with the salt, the action is stronger than when either is alone. Mr. Hunt found that when two per cent, of acetic acid was added to the salt solution previously mentioned, the corrosion was increased to 1738 milligrammes per day. This solution will fairly represent the extreme con- ditions to which aluminium will be subjected in domestic culi- nary operations, and shows that the corrosion is so slight as to be of no practical consequence, being much less than copper, tin-plate or iron would sufifer under similar conditions. Sea-water corrodes aluminium slightly, but much less than iron or steel, under similar conditions. Strips of aluminium on the sides of a wooden sailing vessel lost less than 100 milli- grammes per square metre of surface during six months' ex- posure (Hunt). Messrs. Yarrow & Co., on the Thames, having in view the building of an aluminium torpedo boat for the French government, took two plates of aluminium stiffened by alloying with six per cent, of copper, and after weighing 7 98 ALUMINIUM. accurately secured them on the sides of a wooden, coppered sailing vessel, the copper being removed to make place for the aluminium. This ship made a voyage round the world ; then the aluminium plates were removed, weighed, and found to have suffered no appreciable loss. As a consequence of this result, Messrs. Yarrow proceeded with the construction of the boat, which is the largest vessel yet built of aluminium, having a length of sixty feet, beam nine feet three inches and a maxi- mum speed of twenty-two knots (twenty-five and one-half miles) per hour. It is to be recommended, however, that aluminium hulls in- tended for salt water should be painted, in order to reduce any possible corrosion to a minimum. Organic Secretions. These act only slightly on aluminium, the degree of corrosion being proportioned mostly to the amount of sodium chloride present in the secretion and its degree of acidity, or, particu- larly, of alkalinity. The saliva acts on it so slightly that alu- minium dental plates may be worn for many years without any appreciable corrosion. M. Charriere, a French physician, was the first to make a small tube of it for a person on whom trache- otomy had been performed. He found it to remain almost unaltered by contact with purulent matter ; after a long time a little alumina was formed on it, hardly enough to be visible. The use of aluminium for suture wire is also highly recom- mended ; many instruments for physician's use are being made of aluminium, its great advantages being lightness, incorrodibil- ity, and being so easily cleansed, particularly by antiseptic solutions. The tarnishing of polished aluminium articles when constantly handled is due to the perspiration, which contains about two per cent, of sodium chloride and about an equal quantity of organic acids. Its action is not very strong, yet sufficient to spoil a high polish and give a visible tarnish, as would indeed happen to almost any other metal. If, however, the perspiration is profuse and acts on the aluminium con- CHEMICAL PROPERTIES OF ALUMINIUM. 99 stantly while warm, a deeper corrosion results. I have seen an aluminium ankle-stiffener, of metal about one millimetre thick, which was worn in the heel of a boot for about a year, and was then eaten nearly through by the corrosion due to perspiration a little above the ankle. The shoe lining which covered it had served to keep it constantly in contact with the perspiration, while the temperature may have been about 85° C. This is, however, an extreme case, and it would be interesting to know whether steel or very stifif leather would have lasted as long_ under the same circumstances. Caustic Alkalies. Deville : " Solutions of caustic potash or caustic soda ict' with great energy on aluminium, transforming it into aluminate of potash or soda, setting free hydrogen. However, it is not attacked by caustic potash or soda in fusion ; one may, in fact, drop a globule of the pure metal into melted caustic soda raised almost to red heat in a silver vessel, without observing the least disengagement of hydrogen. Silicon, on the contrary, dissolves with great energy under the same circumstances. I have employed melted caustic soda to clean siliceous alumin- ium. The piece is dipped into the bath kept almost at red heat. At the moment of immersion several bubbles of hydro- gen disengage from the metallic surface, and when they have disappeared all the silicon of the superficial layer of aluminium has been dissolved. It only remains to wash well with water and dip it into nitric acid, when the aluminium takes a beautiful mat. Mallet found that the purest aluminium resists the caustic alkaline solution better than the commercial metal. I have- noticed the same fact in comparing aluminium of different degrees of purity; best commercial metal withstood the action of cold, dilute caustic potash solution seven times better than when it contained three per cent, of copper, and seventy times better than when two per cent, of copper and one per cent, of zinc were present. lOO ALUMINIUM. Prof. A. Stutzer,* of Bonn, finds that the metal made by the electrolytic processes dissolves much slower than that made by the former sodium processes. He ascribes this to the latter metal containing nearly one per cent, of sodium. This, how- ever, can hardly be the case, because metal made by the Deville process rarely contained more than a trace of sodium. The true reason must be simply the greater purity of the metal now be- ing made by electrolysis, which averages over 99 per cent, pure for best quality metal, while the Deville metal was rarely over 98 per cent. pure. Ammonia. Aqua ammonia acts slowly on aluminium, producing a little alumina, part of which remains dissolved. Ammonia gas does • not appear to act on the metal. Lime Water. This acts rapidly on aluminium at first, but the resulting calcium aluminate is insoluble in water, and is, therefore, pre- cipitated on the metal and quickly protects it from further action. If this coating is scraped off the action is repeated. Solutions of Metallic Salts. Deville : " The action of any salt whatever on aluminium may be easily deduced from the action of its acids on that metal. ' We may, therefore, predict that in acid solutions of sulphates and nitrates aluminium will precipitate no metal, not even silver, as Wohler has observed. But the hydrochloric solutions of the same metal will be precipitated, as MM. Tissier have shown. Likewise, in alkaline solutions, silver, lead, and metals high in the classification of the elements are precipitated. It may be concluded from this that to deposit aluminium on other metals by means of the battery, it is always necessary to use acid solutions from which hydrochloric acid, free or combined, .should be absent. For similar reasons the alkaline solutions of * Zeitschr. fiir angewandte Chemie, 1890, No. 23. CHEMICAL PROPERTIES OF ALUMINIUM. lOI the same metals cannot be employed, although they give such good results in plating common metals with gold and silver. It is because of these curious properties that gilding and silvering aluminium are so difficult." These conclusions by Deville are confirmed only when using pure aluminium; the impure metal, containing iron, silicon, or perhaps sodium, may produce very slight precipitates in cases where pure aluminium would produce none. Some observers have noted different results in some cases even when using alu- minium free from these impurities. We will therefore take up these cases and consider them separately. Mercury. — * Aluminium decomposes solutions of mercuric chloride, cyanide or nitrate, mercury separating out first, then forming an amalgam with the aluminium which is immediately decomposed by the water, the result being alumina and mer- cury. From an alcoholic solution of mercurous chloride the mercury is precipitated more quickly at a gentle heat. A solu- tion of mercurous iodide with potassium iodide is also reduced in like manner. Copper. — * From solution of copper sulphate or nitrate, alu- minium separates out copper only after two days' standing, as either dendrites or octahedra ; from the nitrate it also precipi- tates a green, insoluble basic salt. Copper is precipitated immediately from a solution of cupric chloride; but slower from the solution of copper acetate. The sulphate or nitrate solutions behave similarly if potassium chloride is also present, and the precipitation is complete in presence of excess of alu- minium. Silver. — *From a nitrate solution, feebly acid or neutral, aluminium precipitates silver in dendrites, the separation only beginning after six hours' standing. From an ammoniacal solution of silver chloride or chromate, aluminium precipitates the silver immediately as a crystalline powder. Cossa con- firms the statement as to the nitrate solution. Lead. — * From nitrate or acetate solution the lead is slowly * Dr. Mierzinski. I02 ALUMINIUM. precipitated in crystals ; an alkaline solution of lead chromate gives precipitates of lead and chromic oxide. Zinc. — * An alkaline solution of zinc salt is readily decom- posed and zinc precipitated. Margottet states that all metallic chlorides excepting those of potassium or sodium are reduced from solution. This state- ment can hardly include chlorides of magnesium or lithium, since magnesium precipitates alumina from solutions of alu- minium salts. Alkaline or ammoniacal solutions are more easily decomposed than acid solutions ; in alkaline solutions the cause being the facility with which aluminates of the alka- lies are formed. Alkaline Chlorides. — A solution of sodium or potassium chlorides is not appreciably affected by pure aluminium, either cold or warm. However, rather impure aluminium which was packed in a case with saw-dust and kept wet with sea-water for two weeks was corroded ; whether the result would have been the same without the presence of the saw-dust or with purer aluminium, I cannot say. Aluminium Salts. — It is a curious fact that a solution of alu- minium chloride will attack aluminium, forming a basic-chloride with evolution of hydrogen. A solution of alum does not attack aluminium, but if sodium chloride is added it is dissolved with evolution of hydrogen. It is interesting to note that while neither of these salts alone attacks aluminium, the mixture of the two does. Fluorspar. Fluorspar on being melted gives off a little hydroflouric acid vapor, caused by the action of the hydroscopic moisture in it. This vapor will attack aluminium, forming fluoride. Aside from this slight action, the molten fluorspar has no action on the aluminium. It has, however, the property of dissolving a small proportion (about 2 per cent.) of alumina, and this action causes it to be a very efficient flux, because small * A. Cossa, Bull, de la Soc. Chim., 1870, p. 199. CHEMICAL PROPERTIES OF ALUMINIUM. IO3 globules of aluminium are usually encrusted with a thin film of alumina which prevents them from running together to a but- ton. The fluorspar, by dissolving this coating and affording a fluid mass, fluxes the separated globules together. It is often used in connection with cryolite and common salt. Cryolite. Melted cryolite is a very good flux for aluminium, for the same reason as described under fluorspar. It can, however, dissolve over 20 per cent, of alumina, and is therefore that much more efficient as a fluxing agent. At a temperature above the melting point of copper it attacks the aluminium itself, if it is put into it finely divided, but the metal en masse is not sensibly attacked. The result of this attack must be the formation of a sub-fluoride, possibly AIF2. Silicates and Borates. Neither of these classes of compounds can be used as fluxes or slags in working aluminium, since they both rapidly corrode the metal. Deville had little difficulty in decomposing these salts so completely with metallic aluminium that he isolated silicon and boron. If aluminium is melted in an ordinary glass vessel it attacks it, setting free silicon from silica, forming an aluminate with the alkali present and an alloy with the sili- con set free. Aluminium melted under borax is rapidly dis- solved, an aluminium borate being formed. It is thus seen that the common metallurgic slags are altogether excluded from the manufacture of aluminium, and also that it is an im- possibility to manufacture pure aluminium direct from minerals containing silica. The result of reducing kaolin, for instance, would inevitably be highly siliceous aluminium, from which there is no known method of separating out pure aluminium. These facts also point to the importance of keeping molten aluminium from contact with the ordinary siliceous refractory materials in working it. Even the best quality plumbago crucibles will increase the percentage of silicon in commercial I04 ALUMINIUM. aluminium at least 0.25 per cent, at one melting. Magnesia brick linings and magnesia-lined crucibles should be used for melting it in. Nitre. Deville : " Aluminium may be melted in nitre without under- going the least alteration, the two materials rest in contact without reacting even at a red heat, at which temperature the salt is plainly decomposed, disengaging oxygen actively. But if the heat is pushed to the point where nitrogen itself is disen- gaged, there the nitre becomes potassa, a new affinity becomes manifest, and the phenomena change. The metal then com- bines rapidly with the potassa to give aluminate of potash. The accompanying phenomenon of flagration often indicates a very energetic reaction. Aluminium is continually melted with nitre at a red heat to purify it by the oxygen disengaged, with- out any fear of loss. But it is necessary to be very careful in doing it in an earthen crucible. The silica of the crucible is dissolved by the nitre, the glass thus formed is decomposed by the aluminium, and the silicide of aluminium formed is then very oxidizable, especially in the presence of alkalies. The purification by nitre ought to be made in an iron crucible well oxidized by nitre inside." If finely divided aluminium is mixed with nitre and brought to a red heat, the metal is oxidized with the production of a fine blue flame. (Mierzinski.) Nitre is also used sometimes in the composition of aluminium flash-light powders. Alkaline Sulphates and Carbonates. Tissier : "Only 2.65 grammes of aluminium introduced into melted red-hot sodium sulphate (NajSOj) decomposed that salt with such intensity that the crucible was broken into a thousand pieces, and the door of the furnace blown to a dis- tance. Heated to redness with alkaline carbonate, the alu- minium was slowly oxidized at the expense of the carbonic acid, carbon was set free, and an aluminate formed. The re- action takes place without deflagration." chemical properties of aluminium. i05 Metallic Oxides. Tissier Brothers made a series of experiments on the action of aluminium on metallic oxides. Aluminium leaf was care- fully mixed with the oxide, the mixture placed in a small por- celain capsule and heated in a small earthen crucible, which served as a muffle. The results were as follows : Manganese dioxide. — No reaction. Zinc oxide. — No reaction even at white heat. Ferric oxide. — By heating to white heat one equivalent of ferric oxide and three of aluminium, the reaction took place with detonation, and by heating sufficiently we obtained a metallic button, well melted, containing 69.3 per cent, of iron and 30.7 per cent, of aluminium. Its composition corresponds very nearly to the formula AlFe. It would thus appear that the decomposition of ferric oxide will not pass the limit where the quantity of iron reduced is sufficient to form with the alu- minium the alloy AlFe. Lead oxide. — We mixed two equivalents of litharge with one of aluminium, and heated the mixture slowly up to white heat, when the latter reacted on the litharge with such intensity as to produce a strong detonation. We made an experiment with fifty grammes of litharge and 2.9 grammes of aluminium leaf, when the crucible was broken to pieces and the doors of the furnace blown off. Copper oxide. — Three grammes of black oxide of copper mixed with 1.03 grammes of aluminium detonated, producing a strong explosion, when the heat reached whiteness. Beketoff"* reduced baryta (BaO) with metallic aluminium in excess, and obtained alloys of aluminium and barium contain- ing in one case twenty-four per cent., in another thirty-three per cent, of barium. If any of the metallic oxides are fluxed, as by being dis- solved in cryolite, metallic aluminium reduces them to metal at once. Messrs. Green and Wahl have patented this method of * Bull, de la Soc. Chimique, 1887, p. 22. I06 ALUMINIUM. producing pure metallic manganese, which is at present being put into operation in Philadelphia on a commercial scale. Miscellaneous Agents. Phosphate of lime. — Tissier Brothers heated to whiteness a mixture of calcium phosphate with aluminium leaf, without the metal losing its metallic appearance or any reaction being noted. Hydrogen. — This gas appears to have no action on alumin- ium, except to be dissolved in it in a moderately large quantity. Chlorine. — Gaseous chlorine attacks the metal rapidly. Alu- minium foil heated in an atmosphere of chlorine takes fire and burns with a vivid light. Bromine, iodine, act similarly to chlorine. Fluorine. — Fluorine gas forms a thin coating of fluoride which prevents a deeper attack. If the metal is at a dark-red heat, a violent incandescence ensues, and the attack is very energetic. Under the microscope the residue is seen to be globules of alu- minium covered with uncrystallized fluoride. Silver chloride. — Fused silver chloride is decomposed by aluminium, the liberated silver as well as the excess of alumin- ium being melted by the heat of the reaction. Mercurous chloride. — If vapors of mercurous chloride are passed through a tube in which some hot aluminium is placed, mercury is separated out, aluminium chloride deposits in the cooler part of the tube, and the aluminium is melted by the heat developed. Carbonic oxide. — Aluminium acts on this gas, forming alu- mina and setting free carbon. Prof. Arnold proved this by taking molten steel of a known content of carbon, and after adding to it several per cent, of aluminium, he passed a current of this gas through it for one hour. A sample of the metal subsequently analyzed showed one-third more carbon than before the treatment. This reaction is one of the causes of the advantage of adding aluminium to molten steel, as it thus jemoves one of the gases which form blow-holes in the cast- ings. CHAPTER V. PROPERTIES AND PREPARATION OF ALUMINIUM COMPOUNDS. In this chapter we propose to note in rather condensed form the prominent characteristics of the various aluminium com- pounds, with an outline of the methods by which they can be produced, reserving for another chapter, however, the prepara- tion of those salts which are now being manufactured on a commercial scale for purposes of further treatment for alumin- ium. I do not propose this as a substitute for the various chemical treatises on this subject, but simply to add to the completeness of this work in order that a fair understanding of the other parts of the book may not be missed because data of this nature are not immediately at hand. Parts of this chapter are taken from M. Margottet's treatise on aluminium, in Fremy's Enclycopedie Chimique. General Considerations. Position of aluminium in the periodic classification of the ele- ments. — Mendeleeff places aluminium in his third family of elements, it being preceded by boron, and followed by the rare elements scandium, gallium, yttrium, indium, didymium, erbium and thallium. These elements all form oxides of the same general form, R2O3, and their other chemical compounds are ■correspondingly similar. As we have zinc, cadmium and mer- cury as the analogues of magnesium in the second group, so we have gallium, indium and thallium as the corresponding ana- logues of aluminium in the third group. Unfortunately, these elements are so rare that we are not so familiar with their prop- erties as we could wish. We can notice, however, that as the atomic weight increases the specific gravity and the atomic (107 ) I08 ALUMINIUM. volume increase also, while the compounds formed by these metals become more easily decomposable. For instance : Element. Atomic Weight. Specific Gravity. Atomic Volume. Boron ii 2.5 4.5 Aluminium 27 2.7 10 Gallium 70 5.9 12 Indium 113 7.4 14 Thallium 204 11.8 17 Structure of aluminium compounds. — Aluminium has until re- cently been regarded as a quadrivalent element, for the reason that no compound was known whose molecule contained less than two atoms of aluminium combined with six atoms of a mono- valent element. Thus, the oxide was AI2O3, the chloride AhCle,, etc. It was, therefore, supposed that in the molecule of every aluminium compound the two atoms of aluminium were held together by an exchange of one bond, and since each atom had three bonds left over, it was supposed that each single alumin- ium atom had four bonds or affinities. The composition of the oxide and chloride were therefore represented graphically as. follows : r O -, Cl cl = A1— A1 = Cl — Al — Al — Cl A dl The two atoms of aluminium, having six free affinities, were spoken of as a " double hexad-atom." All this reasoning, however, has broken down since the dis- covery of compounds containing only one atom of aluminium! in a molecule, and in which the aluminium is undoudtedly tri- valent; such are the organic salts A^CHa),, A1(C2H5)3,. A1(C5H702)3. In the latter salt, the vapor density corresponds to the formula given at only 45° above its melting point- Even aluminium chloride itself has been proven to have the formula AlCls when its vapor density is taken at a temperature above 800°. We are therefore constrained to drop the former PROPERTIES OF ALUMINIUM COMPOUNDS. IO9 ideas, and consider aluminium as tri-valent. The graphic formulae given above must then be written Cl = A1 — O — Al = o Cl — Al — Cl The tri-valency of aluminium is also required by its position in the list of elements. Thus we have, taking the elements immediately preceding and following it : Atomic Weight. Valence in organic salts Sodium 23 I Magnesium 24 2 Aluminium 27 3 Silicon 28 4 Phosphorus 31 3 Sulphur 32 2 Chlorine 353^ i Aluminium acts as a feeble base or a rather strong acid. As a base it has many analogies with iron in ferric compounds. For instance, the oxides AlzOs and FcjOg crystallize in the same iorms, rhombohedra, with almost exactly the same fundamen- tal angles, while the native hydrous oxides AI2O3.H2O and Fe^Os.HjO, both crystallize in the orthorhombic system with very similar angles and cleavages. As an acid, it forms com- pounds analogous to ferric and chromic acids. For instance : Aluminate of iron ^. FeAl^O,. Ferrate " " FeFejOj. Chromate " " FeCr^O^. These all crystallize in isometric octahedra, and are in every respect very similar minerals. The salts in which aluminium acts as an acid are called aluminates. They may be written as salts of aluminic acid, HjAljO^, but there are other alumin- ates known having a smaller proportion of alumina, and it is much more convenient to express the composition of all these aluminates by the dualistic method. Thus, there are known to exist (see Bayer's method of treating bauxite, next chapter.) I lO ALUMINIUM. Al203.Na20. AljOj.zNa^O. Al,03.3Na,0. AljOs.eNa^O. the writing of which formulae by the rationalistic method would be very cumbersome. The normal or neutral salts of aluminium as a base may be regarded as the acid with its hydrogen replaced by alumin- ium. Thus : Acid. Salt. 3HCI AlCls 3QH,0, AlCQHsO,), 3H,S0t A1,(S0J3 HaPjO^ AIP2O4 Aluminium, however, has a great tendency to form basic salts when these neutral salts are put in contact with an excess of aluminium or alumina. It is most convenient to write the formulae of these by the dualistic method. Thus we have : Normal sulphate, AI2O3.3SO3.16HJO. Basic sulphate, 2AI2O3.SO3.10H2O. Normal acetate, AI2O3.6C2H2O. Basic acetate, Al20s.2C2H.^0.2H20. While the writer has no intention of going back to the duaHstic theories which such formulae were first used to repre- sent, yet he takes the liberty of using these formulas to represent the empirical composition of these salts, because of their con- venience, and without attaching to them any theories as to the internal structure of the molecules. General methods of formation and properties. — Hydrated alu- mina, which has not been too strongly heated, dissolves in strong acids, forming salts which are mostly soluble in water. In the feebler acids and in all organic acids it is completely in- soluble. The salts of these latter acids are formed best by de- composing solution of aluminium sulphate with the barium or lead salt of the acid in question. Most aluminium salts are soluble in water and rather difficult to crystallize : the few in- soluble salts are white, gelatinous, and similar to the hydrate PROPERTIES OF ALUMINIUM COMPOUNDS. Ill in appearance. In the neutral salts the acid is loosely held, for their solution strongly reddens litmus paper and their action is as if part of the acid were free in the salt. For instance, a solution of alum attacks iron giving ofi hydrogen, a soluble basic salt of aluminium being formed as well as sulphate of iron. The neutral salts of volatile acids give ofif acid simply by boiling their solutions, basic salts being formed. An aqueous solution of aluminium chloride loses its acid almost completely on evaporation. Gentle ignition is sufficient in most cases to completely decompose aluminium salts. Hydrated alumina dissolves easily in caustic alkali, forming soluble aluminates ; with baryta two aluminates are known, one soluble, the other not ; all other known aluminates are insoluble. Chemical reactions. — Neutral solutions of aluminium salts react as follows with the common reagents : Hydrogen sulphide produces no precipitate. Ammonium sulphide precipitates aluminium hydrate with separation of free sulphur. Caustic potash or soda precipitates aluminium hydrate, solu- ble in excess. Aqua ammonia precipitates aluminium hydrate insoluble in excess, especially in presence of ammoniacal salts. Alkaline carbonates precipitate aluminium hydrate insoluble in excess. Sodium phosphate precipitates white gelatinous aluminium phosphate, easily soluble in acids or alkalies. Before the blowpipe most aluminium compounds are infusible or are quickly converted into infusible alumina. In the light- colored, infusible compounds, the aluminium may be recognized by giving a beautiful, enamel-like blue color (Thenard's blue) when moistened with dilute solution of cobalt nitrate and ignited in a pure oxidizing flame. Light-colored fusible com- pounds will also give the same reaction, but in them the ab- sence of silica, boric and phosphoric acids must be proven by other tests before the presence of aluminium can be asserted with certainty. i i 2 aluminium. Aluminium Oxide. Commonly called alumina. Composition Al^Oj, and contains 52.95 per cent, of aluminium when perfectly pure. Colorless corundum is a natural pure alumina, in which state it is infusible at ordinary furnace heats, insoluble in acids, has a specific gravity of 4, and is almost as hard as the diamond. To get this into solution it must be first fused with potassium hydrate or bisulphate. The alumina made by igniting aluminium hy- drate or sulphate is a white powder, easily soluble in acids if the ignition has been gentle, but becoming almost insoluble if the heat has been raised to whiteness. The specific gravity of this ignited alumina also varies with the temperature to which it has been raised; if simply to red heat, it is 3.75 ; if to bright redness, 3.8; and if to whiteness, 3.9. In the last case it ac- quires almost .the hardness of corundum. It can be melted to a clear, limpid liquid in the oxyhydrogen blow-pipe ; after cool- ing it forms a clear glass, often crystallized. Small artificial crystals of alumina, exactly similar to the natural ones, have been obtained by dissolving powdered alumina in fused boric oxide and then volatilizing the latter by an intense heat. Fluorine gas acts energetically on powdered alumina. As soon as it comes in contact, the whole mass becomes incandes- cent, forming a fluoride and disengaging oxygen. The reaction A\A + 6F = 2AIF3 + 30. disengages i,ioo calories of heat per kilogramme of fluorine acting. Gaseous chlorine does not act on it even at redness, but if carbon is present at the same time aluminium chloride is formed. Similarly, although neither carbon nor sulphur, alone or mixed together, acts on alumina, carbon bisulphide converts it into aluminium sulphide. The preparation of alumina for commercial purposes is de- scribed at length in the next chapter. properties of aluminium compounds. ii 3 Aluminium Hydrates. There are three natural hydrates of aluminium, which may- be briefly described as follows : Diaspore, formula AI2O3.H2O or Al202.(OH)j, containing 85 per cent, of alumina, occurs in crystalline masses as hard as quartz, with a specific gravity of 3.4. Bauxite, approximately of the formula AI2O3.2H2O or Al20.(OH)4, with the aluminium replaced by variable quantities of iron. If perfectly pure, it would contain 74 per cent, of alumina. Hydrochloric acid re- removes from it only the iron ; heated with moderately dilute sulphuric acid it gives up its alumina; a concentrated alkaline solution also dissolves the alumina. Calcined with sodium carbonate it forms sodium aluminate without melting. Gibbsite, formula AI2O3.3H2O or Al2(OH)6, containing, when pure sixty- five per cent, of alumina, is a mineral generally stalactitic, white, and with a specific gravity of 2.4. It loses two-thirds of its water at 300° and the rest at redness. The artificial hydrates are of two kinds, the soluble and in- soluble modifications. The latter is the common hydrate, such as is obtained by adding ammonia to a solution containing alu- minium. The precipitate is pure white, very voluminous, and can be washed free from the salts with which it was precipi- tated only with great difficulty. Its composition is Al2(OH)6, corresponding to the mineral gibbsite. It is insoluble in water, but easily soluble in dilute acids or alkali solutions. It dis- solves in small quantity in ammonia, but the presence of am- monia salts counteracts this action. When dissolved in caustic potash or soda the addition of ammoniacal salts reprecipitates it. It loses its water on heating, in the same manner as gibbsite. Many other properties of this hydrate, and its manufacture on a large scale, are given in the next chapter. The soluble modi- fication can only be made by complicated processes, too long to be described here, and is principally of use in the dyeing industries ; a full description can be found in any good chemi- cal dictionary. 8 114 aluminium. Aluminates. Potassium aluminate. — Formula KjAljO^, crystallizes with three molecules of water, the crystals containing forty per cent, alumina, 37.5 per cent, potassa and 21.5 per cent, of water. It is formed when precipitated alumina is dissolved in caustic potash, or by melting together alumina and caustic potash in a silver dish and dissolving in water. If the solution is evapo- rated in vacuo, brilliant hard crystals separate out. They are soluble in water but insoluble in alcohol. Sodium aluminate has not been obtained crystallized. Ob- tained in solution by dissolving alumina in caustic soda or by fusing alumina with caustic soda or sodium carbonate and dis- solving in water. If single equivalents of carbonate of soda and alumina are used, the aluminate seems to have the com- position NajAljOi) if an excess of soda is used, the solution appears to contain Al2(0Na)e, or AljOj.sNajO. Dr. Bayer thinks that Al203.2Na20 and Al203.6Na20 are also possible in solution. If a solution of sodium aluminate is concentrated to 20° or 30° B., alumina separates out; if carbonic acid gas is passed through it, aluminium hydrate is precipitated. For a description of its' manufacture on a large scale, see next chapter. Barium aluminate. — Formula BaAl^Oi. Deville prepared it by calcining a mixture of nitrate or carbonate of barium with • an excess of alumina, or by precipitating sulphate of aluminium in solution by baryta water in excess. The aluminate is solu- ble in about ten times its weight of water and crystallizes out on addition of alcohol. The crystals contain four molecules of water. Gaudin obtained it by passing steam over a mixture of alumina and barium chloride, or of alumina, barium sulphate, and carbon, at a red heat. Tedesco claimed that by heating to redness a mixture of alumina, barium sulphate, and carbon, barium aluminate was extracted from the residue by washing with water. He utilized this reaction further by adding solu- tion of alkaline sulphate, barium sulphate being precipitated PROPERTIES OF ALUMINIUM COMPOUNDS. II5 (which was used over), while alkaline aluminate remained in solution. Calcium, aluminate. — Lime water precipitates completely a solution of potassium or sodium aluminate, insoluble gelatinous calcium aluminate being formed, of the formula A]2(06Ca3) or' AljOs.sCaO. At a red heat it melts to a glass, which, treated after cooling with boiling solution of boric acid, affords a com- pound appearing to contain aAljOj-SCaO. (Tissier.) Lime water is also completely precipitated by hydrated alumina, the-^^ compound formed having the composition CaAljOi or AI2O3.-- CaO. Also, by igniting at a high temperature an intimate mixture of equal parts of alumina and chalk, Deville obtained^ a fused compound corresponding to the formfila CaAljO^. Zinc aluminate occurs in nature as the mineral Gahnit^, formula ZnALOi. Berzelius has remarked that when a solution of zinc oxide in ammonia and a saturated solution of alumina in caustic potash are mixed, a compound of the two oxides is precipitated, which is redissolved by an excess of either alkali. Copper aluminate. — On precipitating a dilute solution of sodium aluminate with an ammoniacal solution of copper sul- phate, the clear solution remaining contained neither copper nor aluminium. Whether the precipitate contained these com- bined as an aluminate I did not determine. Magnesium aluminate occurs in nature as Spinel; iron aluminate as Hercynite; beryllium aluminate as Chrysoberyl. The first mentioned has been lately proven to exist in small quantities in crystallized blast-furnace slags.* Ebelman has also prepared it in small crystals by dissolving alumina and magnesia in fused boric oxide and driving off some of the solvent by intense heat. Aluminium Chloride. Formula AICI3, contains 20.2 per cent, of aluminium. The commercial chloride is often yellow or even red from the pres- ence of iron, but the pure salt is quite white. It absorbs water * P. W. Shimer. Journal Am. Chemical Soc, 1894, p. 501. Il6 ALUMINIUM. very rapidly from the air. It usually sublimes without melting, ■especially when in small quantity, but if a large mass is rapidly ieated, it may melt and even boil, but its melting point is very close to its boiling point. Friedel and Crafts have determined the melting point as 178°, boiling point 183°. When sublimed it deposits in brilliant, hexagonal crystals. A current of steam rapidly decomposes it into alumina and hydrochloric acid. Oxygen disengages chlorine from it at redness, but decomposes it incompletely. Potassium or sodium decomposes it ex- plosively, the action commencing below redness. Anhydrous sulphuric acid converts it into aluminium sulphate. Alumin- ium chloride combines with many other chlorides, forming the double salts. On dissolving this salt in water, or by dissolving alumina in hydrochloric acid, a solution is obtained which on evaporation deposits crystals having the formula AICI3.6H2O. If these crystals are heated, they decompose, losing both water and acid and leaving alumina. Thus it is not possible to obtain anhydrous aluminium chloride by evaporating its solution, and the anhydrous salt must be made by other methods, detailed at length in the next chapter. Aluminium-Sodium Chloride. formula AlClj.NaCl contains 14 per cent, of aluminium. The commercial salt is often yellow or brown from the presence ,of ferric chloride, but the pure salt is perfectly white. Its melt- ing point has been generally stated to be 180°, but Mr. Baker, to Cis as in Fig. 12. As to the end, in one form the edge was not turned up, leaving the end open as in Fig. 13. Another form, which I use when wishing to let the sodium accumulate in the condenser till it is quite full, is made by turning up the edge at the end all but a small space left free, thus giving the end the appearance of Fig. 14, this -device also being shown in Fig. 11. The gas evolved during 1 88 ALUMINIUM. the reaction then escapes at the hole 0. The most rational arrangement of the apparatus is that shown in Fig. 15. In this condenser the lower part, instead of being horizontal, is in- clined, and the end having two openings, O and 0' , the sodium trickles out at the lower one as it condenses, while the gas es- capes by the slightly larger upper opening. In placing the plates together, the raised edges are washed with hme so as to form a good joint with the flat plate, and the plates are kept together by strong pressure grips. To conduct the operation, the bottles are filled entirely with mixture, the tube T adjusted, and then placed on the two sup- ports, there being already a good bed of fire on the grate. The front is put up, the shaft filled with coke, and the damper opened. The gases disengaged from the bottle are abundant, of a yellow color ; at the end of half an hour white fumes of carbonate of soda appear. The condenser should not yet be attached, but it should be noted if any sodium condenses on a cold iron rod pushed into the tube, which would be indicated by its fuming in the air. As soon as this test shows that sodium is being produced, the condenser is attached and the fire kept quite hot. The condenser soon becomes warm from the gases passing through it, while the sodium condenses and flows out at the end D (Fig. 15). It is received in a cast-iron basin L, in which some non-volatile petroleum is put. When at the end of a certain time the condenser becomes choked, it is replaced by another which has been previously warmed up to 200° or 300° by placing it on top of the furnace. If the closed con- denser is used, care must be taken to watch when it becomes full, on the point of running from the upper opening, and the condenser then replaced and plunged into a cast-iron pot full of petroleum at a temperature of 150°. The sodium here melts at the bottom of this pot and is ladled out at the end of the day. The oil is generally kept up to 150° by the hot con- densers being plunged in constantly. The pot ought to have a close cover, to close it in case the oil takes fire ; the extinc- tion of the fire can thus be assured and no danger results. If THE MANUFACTURE OF SODIUM. 1 89 the oil fires just as a condenser is being introduced, the sodium is run out in the air without igniting, the only drawback being that the condenser must be cleaned before using again. This method occasions a large loss of oil, however, and has been completely abandoned for the other form of condensers. When the operation proceeds well only pure sodium is obtained, the carbonized products which accompany in so provoking a man- ner the preparation of potassium not occurring in quantity sufficient to cause any trouble. Before using a condenser a second time it is put on a grating over a basin of petroleum and rubbed with a chisel-pointed tool in order to remove any such carbonized products. From time to time this material is ■collected, put into a mercury bottle, and heated gently. The oil first distils, and is condensed in another cold bottle. The fire is then urged, a condenser attached, and the operation pro- ceeds as with a fresh charge, much sodium being thus recov- ered. The raw sodium is obtained from the bottles in quantities of over half a kilo ; it is perfectly pure, dissolving in absolute alcohol without residue. It is melted and moulded into ingots just as lead or zinc. The operation I have described is exe- cuted daily, and only once has the sodium ignited. To prevent such accidents it is simply necessary to keep water away from the apparatus. The reduction of carbonate of soda and the production of sodium are such easy operations that when tried by those conversant with the manufacture of potassium or who have read about the difficulties of the production of sodium, success is only gained after several attempts — the failure being due solely to excess of precautions. The reduction should be carried on rapidly, so that a bottle charged with two kilos of rriixture may be heated and emptied in, at most, two hours. It is unnecessary to prolong the operation after the yellow flame stops issuing from the condenser, for no more sodium is ob- tained and the bottle may frequently be destroyed. The temperature necessary for the reduction is not so high as it has teen so far iiriagined. M. Rivot, who has assisted in these ex- I go ALUMINIUM. periments, thinks that the bottles are not heated higher than the retorts in the middle of the zinc furnaces at Vielle Mon- tagne. I have been even induced to try cast-iron bottles, but they did not resist the first heating, without doubt because they were not protected from the fire by any luting or covering. But I was immediately successful in using cast-iron bottles decar- burized by the process used for making malleable castings. The mercury bottles heated without an envelope ought to serve three or four operations when entrusted to a careful workman. Besides all these precautions, success in this work depends particularly on the ability and experience of the workman, who can at any time double the cost of the sodium by carelessness in managing the fire. _ Continuous manufacture in cylinders. It might be thought that by increasing proportionately in all their parts the dimen- sions of the apparatus just described, it would be easy to pro- duce much larger quantities of sodium. This idea, which naturally presented itself to me at once, has been the cause of many unfruitful attempts, into the details of which I will not enter. I must, however, explain some details which may ap- pear insignificant at first sight, but which were necessitated during the development of the process. For instance, it will perhaps look irrational for me to keep the same sized outlet tubes and condensers that were used with the mercury bottles, for tubes five times as large ; but I was forced to adopt this arrangement after trying the use of tubes and condensers of all sizes ; indeed, it is fortunate for the success of the operation that this was so, for it became very injurious to the workmen to handle the large and weighty apparatus in the face of a large sodium flame. The mixture of sodium carbonate and carbon is made in the manner already described. I would say again that a previous strong calcination of the materials presents a great advantage^ not only because it permits putting a much larger weight into the retorts at once, but also that, being more compact, the mix- ture will not rise as powder and be violently thrown out of the THE MANUFACTURE OF SODIUM. 191 Strongly-heated retorts. The mixture should also be calcined as needed, and used to fill the tubes while still red hot. When cold, uncalcined mixture is used, it is put into large cartridges of thick paper or canvas, 8 centimetres diameter and 35 cen- timetres long. The furnace and tubes are shown in section in Fig. 16. The tubes T are 120 centimetres long, 14 centimetres inside diameter, and 10 to 12 millimetres in thickness. They are formed from one piece of boiler iron, bent and welded along Fig. 16. one side. The iron plate P which closes one end is about 2 centimetres thick, and pierced on one of its edges quite close to the side of the cylinder by a hole in which is screwed or fitted an iron tube, Z, 5 to 6 centimetres long and 15 to 20 millimetres inside diameter, and tapering off at the end to fit into the condenser neck. The other end of the tube is closed by an iron plug, 0, terminated by a knob. The welded side of the tube is kept uppermost. These iron tubes should not, like the mercury bottles, be heated in the bare fire ; it is necessary to coat them with a resistant luting which is itself enveloped by a refractory jacket i centimetre thick, 22 centimetres interior 192 ALUMINIUM. diameter, and the same length as the retorts. This protection is commenced by plastering the retorts over with a mixture of equal parts of raw clay and stove ashes, which have been made into a paste with water and as much sand worked into the mix- ture as it will take without losing its plasticity, also adding some horse manure. This luting should be dried slowly, and the tube thus prepared is introduced into the refractory jacket, the open space between the two being filled with powdered refractory brick. Finally, luting is put on the iron plate P, so that no part of it is exposed to the flame. The furnace I have used is a reverberatory, but I do not re- commend its use without important modifications, because it does not realize all the conditions of easy and economic heat- ing. The grate is divided into two parts by a little wall of re- fractory brick, on which the middle of the reduction cylinders rests. The tubes are thus seen to be immediately over the bed of fuel. The top of the bridge is a little higher than the upper edge of the cylinders, this and the very low arch making the flame circulate better all around the tubes. A third cylinder might easily be placed above these two, and be heated satis- factorily, without any more fuel being burnt. This reverbera- tory receives on its bed the mixtures to be calcined, placed in cast-iron or earthen pots according to their composition. When the furnace is kept going night and day producing sodium, the temperature rises on the bed to clear cherry-red, and experience has shown that other reducing cylinders might be placed there, under such conditions, and be heated suf- ficiently for the reduction. All that I have said of the manufacture of sodium in mercury bottles applies equally to its manufacture in cylinders. The only difference consists in the charging and discharging, and I have only to add several precautions to be taken. On intro- ducing the cartridges containing uncalcined mixture, only 8 to 9 kilos can be heated at once ; double as much can be used of previously-calcined mixture. The plug is put in place, not so tightly that it cannot easily be taken out again ; a little THE MANUFACTURE OF SODIUM. 1 93 luting stops all leakages which show themselves. The reduc- tion lasts about four hours. When it is finished, a little water is thrown on the plug 0, and it is easily loosened and removed. On looking into the cylinder, the cartridges are seen to have kept their shape, but have shrunken so much that their diameter is only about 2 to 3 centimetres ; they are very spongy. This shows that the mixture has not melted ; the remainder is prin- cipally lime and carbon, and free from sodium carbonate. While opening the cylinder, a bright-red-hot iron is thrust into the outlet tube L, to keep dirt from getting into it, and it is kept in until the charging is finished. The cartridges are put in by means of semi-cylindrical shovels. The sudden heating of the mixture disengages soda dust from uncalcined mixtures, which is very disagreeable to the workmen. The cylinders are closed, and when the sodium flame appears at the outlet tube the condenser is attached, and the operation proceeds as already described. The envelopes of the cylinders are thick enough to prevent the distillation of the sodium being in any way affected by the accidental causes of cooling the fire. So when fresh fuel is charged or the door of the reverberatory is opened, causing the draft to cease almost entirely in the fire-place, the operation should not suffer by these intermittences, provided.that they are not too long prolonged. In short, when operating in cylinders, the production of sodium is easier, less injurious to the work- men, and less costly in regard to labor and fuel than when working with mercury bottles. At times, after working a fort- night with many interruptions dangerous for the apparatus, my experiment has been suddenly ended. The furnace was intact ; the envelopes of the tubes were split open, and the luting on the tubes found to be compact and coherent, but without traces of fusion, showing perfect resistance. The iron tubes mean- while had not suffered inside or out, and seemed as though they would last indefinitely. I attribute this success to the par- ticular care given to the composition of the jackets, and to the perfection with which the tubes had been welded. Only on 13 194 ALUMINIUM. one of the tubes was a very slight crack found, on a part not the most highly heated, and not sufficient to cause the tube to be discarded. Tissier Bros.' method of procedure. (1856). As related in the historical treatment of the subject (p. 13), Deville charged the Tissier Bros, with appropriating from him the process for the continuous production of sodium in cylinders, which, as just given, was devised during the experiments at Javel. On the other hand, the Tissier Bros, asserted their right to the process, patenting it, and using it in the works started at Rouen in the latter part of 1855. The following details are taken from Tissier's " Recherche de 1' Aluminium," only such being selected as supplement Deville's description, which has just been given. The sodium carbonate is first well dried at a high temper- ature, then mixed with well-dried pulverized charcoal and chalk, ground to the finest powder, the success of the operation de- pending on the fineness of this mixture. The proportions of these to use are various. One simple mixture is of Sodium carbonate 566 Coal 244 Chalk 95 Coke 95 1000 Another contains — Sodium carbonate 615 Coal 277 Chalk 108 1000 The addition of chalk has the object of making the mixture less fusible and more porous, but has the disadvantage that the residue remaining in the retort after the operation is very im- pure, and it is impossible to add any of it to the succeeding charge ; and also, some of it being reduced to caustic lime forms caustic alkali with some sodium carbonate, which is then THE MANUFACTURE OF SODIUM. 195 lost. WheD the mixture is well made it is subjected to a pre- limiinary calcination. This is done in cast-iron cylinders, two of which are placed side by side in a furnace and heated to redness (see Fig. 17). This is continued till all the moisture, carbonic acid, and any carburetted hydrogen from the coal, cease coming off. The mass contracts, becomes white and somewhat dense, so that a larger amount of the mixture can now be treated in the retorts where the sodium is evolved. As soon as the outcoming gases burn with a yellow flame, showing Fig. 17. sodium coming ofT, the calcination is stopped. The mixture is then immediately drawn out on to the stone floor of the shop, where it cools quickly and is then ready for the next operation. This calcination yields a mixture which without any previous reactions is just ready to evolve sodium when brought to the necessary temperature. This material is made into a sort of cylinder or cartridge and put into the decomposition retorts (see Fig. 16). The charging should be done quickly. The final retorts are of wrought-iron, since cast-iron would not stand the heat. At each end this retort is closed with wrought- iron stoppers and made tight with fire-clay. Through one stopper leads the pipe to the condenser, the other stopper is the one removed when the retort is to be recharged. These retorts are placed horizontally in rows in a furnace. Usually four are placed in a furnace, preferably heated by gas, such as the Siemens regenerative furnace or Bicheroux, these being 196 ALUMINIUM. much more economical. In spite of all these precautions the retorts will be strongly attacked, and in order to protect them from the destructive action of a white heat for seven or eight hours they are coated with some kind of fire-proof material. The best for this purpose is graphite, which is made into cylin- ders enclosing the retorts, and which can remain in place till the furnace is worn out. These graphite cylinders not only protect the iron retorts, but prevent the diffusion of the gas- eous products of the reaction into the hearth, and so support the retorts that their removal from the furnace is easily accom- plished. Instead of these graphite cylinders the retorts may be painted with a mixture that melts at white heat and so en- amels the outside. A mixture of alumina, sand, yellow earth, borax, and water-glass will serve very well in many cases. We would remark that the waste gases from this furnace can be used for the calcining of the mixture, or even for the reduction of the aluminium by sodium, where the manufacture of the former is connected with the making of the sodium. As for the reduction of the sodium, the retort is first heated to redness, during which the stopper at the condenser end of the retort is left off. The charge is then rapidly put in, and the stopper at once put in place. The reaction begins almost at once and the operation is soon under full headway, the gases evolved burning from the upper slit of the condenser tube with a flame a foot long. The gases increase in volume as the operation continues, the flame becoming yellower from sodium and so intensely bright as to be insupportable to look at. Now has come the moment when the workman must quickly adapt the condenser to the end of the tube projecting from the retort, the joint being greased with tallow or parafHn. The sodium collects in this in a melted state and trickles out. The length of the operation varies, depending on the intensity of the heat and the quantity of the mixture ; a charge may sometimes be driven over in two hours, and sometimes it takes eight. We can say, in general, that if the reaction goes on quickly a some- what larger amount of sodium is obtained. The higher the THE MANUFACTURE OF SODIUM. 1 97 heat used, however, the quicker the retorts are destroyed. The operation requires continual attention. From time to time, a workm-an with a prod opens up the neck of the condenser, but if care is not taken the metal overflows ; if this happens, the metal overflowing is thrown into some petroleum, while another man replaces the condenser with an empty one. The operation is ended when the evolution of gas ceases and the flame becomes short and feeble, while the connecting tube be- tween the retort and condenser keeps clean and does not stop up. As soon as this occurs, the stopper at the charging end is removed, the charge raked out into an iron car, and a new charge being put in, the operation continues. After several operations the retorts must be well cleaned and scraped out. The sodium thus obtained is in melted bits or drops, mixed with carbon and sodium carbonate. It must, therefore, be cleaned, which is done by melting it in a wrought-iron kettle under paraffin with a gentle heat, and then casting it into the desired shapes. The sodium is kept under a layer of oil or any hydrocarbon of high boiling point containing no oxygen. Tissier gives the reaction as — Na2C03+2C=3CO+2Na. The sodium is condensed, while the carbonic oxide, carrying over some sodium, burns at the end of the apparatus. This would all be very simple if the reaction of carbonic oxide on sodium near the condensing point did not complicate matters, producing a black, infusible deposit of sodium monoxide (Na^O) and carbon, which on being melted always give rise to a loss of sodium. Deville's Improvements at La Glacier e (1857). At this works Deville tried the continuous process of manu- facturing sodium in cylinders on a still larger scale, with the fol- lowing results, as described by Deville himself: — " We made no change in the composition of the mixtures used 198 ALUMINIUM. from those already described, or in the form or size of the iron tubes or the method of condensation ; but we worked with six cylinders at a time in a furnace similar to the puddling furnaces of M. Guadillot, the tubes being protected by refractory envel- opes. The cylinders were so arranged on the hearth that the flame bathed all parts of their surface. A low brick wall ex- tends down the centre of the hearth, supporting the middle of the cylinders, which extend across it. The hearth is well rammed with refractory sand, and the space between it and the bottom of the cylinder serves as a passage-way for most of the flame. " Our six cylinders worked satisfactorily for five days. We were able to observe that they were all heated with remarkable uniformity, and that the heat was sufficient all round them. It also appeared that the rear end of the cylinders required only a hermetic seal. Indeed, as soon as the operation was well under way and sodium distilling off, some of it condensed and oxidized in the cool parts of the apparatus, forming a sort of plug of carbonate and carbides of sodium, which the vapor and gases could no longer penetrate. We were thus able for a long time to distil sodium away from one of our tubes which was entirely opened at the rear. " This new furnace worked so well that we were hopeful of complete success, when an accident happened which compelled the stopping of the experiment. The iron tubes had been ordered 1.20 metres long, the size of the hearth calculated ac- cordingly, but they were delivered to us only 1.05 metres long. We made use of these, with the result that the rear ends be- came red-hot during the operation and allowed sodium vapors to leak through. These leaked through the luting, and escap- ing into the furnace, melted the envelopes very rapidly. "In another attempt, in which this fault was avoided, we were unsuccessful because the envelopes gave way at the first heat- ing up, both they and the iron tubes being of inferior quality. We were considerably inconvenienced by the failure of these experiments, which caused considerable expense and gave no very definite results. Just then a new sort of apparatus was THE MANUFACTURE OF SODIUM. 1 99 devised, a description of which is given later on. It will be seen that we were compelled to employ tubes of very small value, so that their destruction in case of accident involved no great loss, and to heat each one by an independent fire, so that the stoppage or destruction of one cylinder would not necessitate the stoppage or endanger the safety of the neighboring ones." Cast-iron vessels. Deville tried at La Glaciere, as well as at Javel, to utilize cast-iron vessels for producing sodium. Deville states the difficulties which caused their use to be unsuccessful to be as follows : "The result was always unfavorable. Sodium is obtained, but as soon as its production becomes rapid the vessel melts and the operation is quickly ended. This follows because the tem- perature necessary for the production of the metal is far from being sufficient for producing it in large quantities at once ; and we know that this is the one condition for condensing the so- dium well and obtaining it economically. This observation led me to think that by diminishing very much the temperature of the furnace, large apparatus of cast-iron with large working surface could be used, thus making at a time a large amount of metallic vapor which could be condensed in recipients of ordi- nary size. The whole large apparatus would thus have the out- put of a smaller one worked at a higher temperature. My ex- perience has shown me that in large-sized tubes heated to a low temperature there is formed in a given time about as much sodium as from a single mercury bottle at a much higher heat. This is the reason why larger condensers are not necessary with the larger tubes. Before knowing this fact, I tried a large number of useless experiments to determine the size of con- densers suitable for large apparatus. It is on this principle that I have long been endeavoring to make sodium without working at high temperatures, and using less costly and more easily protected apparatus." Improvements used at Nanterre (1859). The method used here was exactly that already described, 200 ALUMINIUM. the improvements being solely in details of the apparatus. These are described by Deville as follows : — " The experiments made at Javel and the continuous process used at Glaciere have shown us in the clearest manner the ab- solute necessity of efficient protection for the iron cylinders, for without this protection the method cannot be practiced with economy. Further, experiments in this direction are very costly, for the failure of a tube stops the working of a large number of cylinders, and often compromises the brick-work of the furnace itself. We therefore came to the conclusion that for making the small quantity of sodium we required, 300 to 500 kilos a month, it would be better to employ smaller apparatus, independent of each other and easy to replace. " The iron tubes are made of thinner iron and at very little ex- pense, by taking a sheet of iron, curving it into a cylinder and riveting the seam. This tube resembles very closely those used at Javel, shown in Fig. 16, but of smaller dimensions. It is closed at each end by cast-iron plugs, one of which has a hole for the outlet tube. These cylinders are filled with sodium mixture and placed in furnaces of the form of Fig. 10, except it is necessary to have openings in the back and front of the fur- nace so that the cast-iron plugs closing the cylinders may be outside, to prevent their melting. We used coke at first for fuel, fed around the cylinders, but M. Morin has since placed the tubes out of direct contact with the fuel, uses soft coal, and heats the tubes by contact with the flame and by radiation. In the latest form used, two cylinders are placed in each furnace, and, in general, they serve for two or three operations. All that has been said in connection with the manufacture in mercury bot- tles is immediately applicable to the manufacture in cylinders of this kind, the capacity of which may vary from two to six or eight litres, without any change in the manner of using them. We have, however, adopted altogether condensers of cast-iron. The neck is cylindrical and belongs only to one-half of the ap- paratus, the neck end of the other plate being beveled and fit- ting closely against a recess in the other plate." THE MANUFACTURE OF SODIUM. 20I The foregoing shows the sodium industry as it was perfected by Deville, in 1859, and as it remained for twenty-five years without sensible change. The cost of sodium by this process is stated to have been, in 1872, as follows: — Manufacture of one kilo of sodium. Soda 9.35 kilos @ 32 fr. per 100 kilos = 3 fr. 9 cent. Coal 74.32 " " 1.40" " " " = I " 4 " Wages 3 " 73 " Expenses 3 " 46 " Total 1 1 fr. 32 cent. which is equal to $1 per lb. The larger part of the expense account is the cost of retorts or tubes in which the operation takes place, and which are so quickly destroyed that the re- placing of them forms nearly one-quarter of the cost of the metal. Minor Improvements (185 9- 1888). An experiment made by Deville in 1864* is of considerable interest in connection with some more recent processes. Guy Lussac and Thenard having observed that caustic potash is re- duced by iron, Deville took a mercury bottle with an aperture above and one below, to which was fitted an iron tube and a sodium condenser. Finely divided iron, reduced by hydrogen, was put into the bottle, and when red hot, caustic soda was in- troduced through the upper aperture. The iron was strongly acted upon, and in less than 20 minutes Deville obtained y^ a kilo of pure sodium. The reduction was stopped by a mixture of soda and iron oxide filling up the lower opening. The ar- rangement and reactions suggest strongly some later processes. Why Deville did not continue on this line, I cannot say. R. Wagnerf uses paraffin in preference to paraffin oil in which to keep the sodium after making it. Only pure paraffin, which has been melted a long time on a water-bath, and all its water driven off, can be used. The sodium to be preserved is * Lef ons de Chemie, 1864-5, P- 336- + Dingier, 1883, p. 252. 202 ALUMINIUM. dipped in the paraffin melted on a water-bath, and kept at no higher heat than 55° C, and the metal is thereby covered with a thick coat of paraffin which protects it from oxidation, and may then be put up in wooden or paper boxes. When the metal is to be used, it is easily freed from paraffin by simply warming it, since sodium melts at 95° to 96° C, and the paraffin at 50° to 60°. The reduction of potassium carbonate by carbon requires a much less degree of heat than that of sodium carbonate, and therefore many attempts have been made to reduce potassium and sodium together, under circumstances where sodium alone would not be reduced. Dumas* added some potassium car- bonate to the regular sodium mixture; and separated the sodium and potassium from each other by a slow, tedious oxi- dation. R. Wagnerf made a similar attempt. He says that not only does the reduction of both metals from a mixture of their carbonates with carbon work easier than sodium carbonate alone with carbon, but even caustic soda may be used with potassium carbonate and carbon. Also, the melting point of potassium and sodium alloyed is much lower than that of either one alone, in consequence of which their boiling point and the temperature required for reduction are lower. J. B. Thompson and W. WhiteJ specify mixing dry sodium carbonate with a liquid carbonaceous material, preferably tar, driving off all volatile matter in iron pots at a low heat, and then distilling in a tubular fire-clay retort connected with a tightly-closed receiver containing a little paraffin oil to ensure a non-oxiding atmosphere, and also provided with a small escape pipe for carbonic oxide. This process gave great prospects of success when tried in the laboratory, but on a manufacturing scale it failed for the reason (assigned by Mr. Thompson) that the sheet-iron tray, designed to keep the material from attack- ing the retort, absorbed carbon at about 1000° C. and fused, after which no sodium was produced, since the material took * Handbuch der Angewandten Chemie, 1830, ii. 345. t Dingier, 143, 343- J English Patent 8426, June 11, 1887. THE MANUFACTURE OF SODIUM. 203 up silica from the retort, absorbing so much that the carbon no longer decomposed it. H. S. Blackmore,* of Mount Vernon, U. S. A., patents the following process of obtaining sodium: — Calcium hydrate 273^ parts. B erric oxide 31 " Dry sodium carbonate 31 " Charcoal loj!^ " are intimately mixed and subjected to a red heat for 20 min- utes, afterwards to a white heat. Caustic soda is first produced, the carbon reduces the ferric oxide, producing iron, which in its turn reduces the caustic soda, and sodium vapors distil. The residue consists of ferric oxide and lime, and is slaked and used over. O. M. Thowlessf of Newark, N. J., claims to place a retort in a furnace, providing it on one side with an arm through which carboniferous material can be supplied, on the other side with a similar arm (surrounded by flues), into which caustic soda or sodium carbonate is charged — a valve controlling their flow into the retort. Outside the furnace and on top of it is a flat con- denser into which the sodium vapor passes. G. A. JarvisI patents the replacement of the iron tubes or crucibles used in the manufacture of sodium, by fire-clay ap- paratus lined with basic material, such as strongly burnt mag- nesia with 10 per cent, of fluorspar. Castner's Process (1886). The first public announcement of this process was through one of the New York daily journals,^ and as the tone of the article is above that of the usual newspaper reports, and the expectations contained in it were subsequently more than realized, we cannot better introduce a description of this process than by quoting the paragraph referred to : — ♦English Patent 15 156, Oct. 22, 1888. f English Patent 12486 (1887). X English Patent 4842, March 31, 1888. § New York World, May 16, 1886. 204 ALUMINIUM. "When sodium was reduced in cost to $1.50 per lb. it was thought to have touched a bottom figure, and all hope of mak- ing it any cheaper seemed fruitless. This cheapening was not brought about by any improved or new process of reduction, but was owing simply to the fact that the aluminium industry required sodium, and by making it in large quantities its cost does not exceed the above-mentioned price. The retail price is now $4.00 per lb. The process now used was invented by Briinner, in 1808, and up to the present time nothing new or original has been patented except three or four modifications of his process which have been adopted to meet the requirements of using it on a large scale. Mr. H. Y. Castner, whose labora- tory is at 218 West Twentieth Street, New York, has the first patent ever granted on this subject in the United States, and the only one taken out in the world since 1808. Owing to negotiations being carried on, Mr. Castner having filed appli- cations for patents in various foreign countries, but not having the patents granted there yet, we are not at liberty to state his process fully. The metal is reduced and distilled in large iron crucibles, which are raised automatically through apertures in the bottom of the furnace, where they remain until the reduc- tion is completed and the sodium distilled. Then the crucible is lowered, a new one containing a fresh charge is substituted and raised into the furnace, while the one just used is cleaned and made ready for use again. The temperature required is very moderate, the sodium distillling as easy as zinc does when being reduced. Whereas by previous processes only one-third of the sodium in the charge is obtained, Mr. Castner gets nearly all, for the pots are nearly entirely empty when with- drawn from the furnace. Thus the great items of saving are two or three times as much metal extracted from a given amount of salt, and cheap cast iron crucibles used instead of expensive wrought-iron retorts. Mr. Castner expects to pro- duce sodium at 25 cents per lb., thus solving the problem of cheap aluminium, and with it magnesium, silicon, and boron, all of which depend on sodium for their manufacture. Thus THE MANUFACTURE OF SODIUM. 205 the production of cheap sodium means much more than cheap aluminium. Mr. Castner is well known in New York as a chemist of good standing, and has associated with him Mr. J. H. Booth and Mr. Henry Booth, both well known as gentlemen of means and integrity." The following are the claims which Mr. Castner makes in his patent:* 1. In a process for manufacturing potassium or sodium, per- forming the reduction by diffusing carbon in a body of alkali in a state of fusion at moderate temperatures. 2. Performing the reduction by means of the carbide of. a metal or its equivalent. 3. Mechanically combining a metal and carbon to increase the weight of the reducing material, and then mixing this pro- duct with the alkali and fusing the latter, whereby the reducing material is held in suspension throughout the mass of fused alkali. 4. Performing the deoxidation by the carbide of a metal or its equivalent. For an explanation of the principles made use of in the above outlined process we will quote from a lecture delivered by Mr. Castner at the Franklin Institute, Philadelphia, October 1 2th, 1886. That Institution has since bestowed on Mr. Cast- ner one of its gold medals as a recognition of the benefit to science accruing from his invention. " In the ordinary sodium process, lime is added to the reduc- ing mixture to make the mass refractory, otherwise the alkali would fuse when the charge is highly heated, and separate from the light, infusible carbon. The carbon must be in the propor- tion to the sodium carbonate as four is to nine, as is found needful in practice, so as to assure each particle of soda in the refractory charge having an excess of carbon directly adjacent or in actual contact. Notwithstanding the well-known fact that sodium is reduced from its oxide at a degree of heat but slightly exceeding the reducing point of zinc oxide, the heat necessary * U. S. Pat. No. 342,897, June i, 1886. Hamilton Y. Castner, New York, 206 ALUMINIUM. to accomplish reduction by this process and to obtain even one-third of the metal in the chai-ge, closely approaches the melting point of wrought-iron. " In my process, the reducing substance, owing to its com- position and gravity, remains below the surface of the molten salt, and is, therefore, in direct contact with fused alkali. The metallic coke of iron and carbon contains about 30 per cent, carbon and 70 per cent, iron, equivalent to the formula FeCj. I prefer to use caustic soda, on account of its fusibility, and mix with it such quantity of so-called ' carbide ' that the carbon contained in the mixture shall not be in excess of the amount theoretically required by the following reaction: — 3NaOHf FeC,=--3Na4-Fe + CO f CO.+sH ; or, to every 100 lbs. of pure caustic soda, 75 lbs. of 'carbide,' containing about 22 lbs. of carbon. " The necessary cover for the crucible is fixed stationary in each chamber, and from this cover a tube projects into the con- denser outside the furnace. The edges of the cover are convex, those of the crucible concave, so that when the crucible is raised into position and held there, the tight joint thus made prevents all leaking of gas or vapor. Gas is used as fuel, and the re- duction begins towards 1000° C. As the dharge is fused, the alkali and reducing material are in direct contact, and this fact, together with the aid rendered the carbon by the fine iron, in withdrawing oxygen from the soda, explains why the reduction is accomplished at a moderate temperature. Furthermore, by reducing from a fused mass, in which the reducing agent re- mains in suspension, the operation can be carried on in crucibles of large diameter, the reduction taking place at the edges of the mass, where the heat is greatest, the charge flowing thereto from the centre to take the place of that reduced. " I am enabled to obtain fully 90 per cent, of the metal in the charge, instead of 30 per cent, as formerly. The crucibles, after treatment, contain a little carbonate of soda, and all the iron of the 'carbide' still in a fine state of division, together THE MANUFACTURE OF SODIUM. 207 with a small percentage of carbon. These residues are treated with warm water, the solution evaporated to recover the car- bonate of soda, while the fine iron is dried, and used over again for 'carbide.' " Mr. Castner having demonstrated in his New York laboratory the success of his process, went to England, and for several months during the winter of 1886-7 was engaged in building and working a large sodium furnace. This was successfully car- ried out near London, the inventor being assisted by Mr. J. MacTear, F. C. S., who, in March, 1887, read a description of this furnace and the results obtained before the Society of Chemical Industry. During the working of this furnace it was inspected by many chemical and metallurgical authorities, who were completely satisfied as to its success. As the furnace then described differed in a few details from the one just re- ferred to, it may be well to extract the essential particulars from Mr. MacTear's paper — on the ground that the importance of this invention justifies a complete discussion of its develop- ment: — " Since Mr. Castner's paper upon his process, which was read before the Franklin Institute of Philadelphia, October 12, 1886, several slight changes in the mode of carrying on this process have been made. These have been brought about by the experience gained from the actual working of the process upon a commercially large scale. "The reactions by which the sodium is produced are some- what difficult to describe, as they vary somewhat according to the mixture of materials and temperature employed in the re- duction. The mixture and temperature which it is now pre- ferred to use is represented by the reaction : — 6NaH0 + FeC2= 2Na2CO, + 6H + Fe + zNa. " In place of using an actual chemical compound of iron and carbon, as expressed by the above reaction, a substitute or equivalent is prepared as follows : To a given quantity of melted pitch is added a definite proportion of iron in a fine state of 208 ALUMINIUM. division. The mixture is cooled, broken up into lumps, and cooked in large crucibles, giving a metallic coke consisting of carbon and iron, the proportions of each depending upon the relative quantities of pitch and iron used. This metallic coke, after being finely ground, provides a substance having the iron and carbon in a like proportion to an iron carbide, and from which neither the iron nor carbon can be separated by mechan- ical means. The fine iron is conveniently prepared by passing carbonic oxide and hydrogen in a heated state, as obtained from an ordinary gas producer, over a mass of oxide of iron commercially known as 'purple ore,' heated to a temperature of about 500° C. " In producing sodium, caustic soda of the highest obtain- able strength is used, and there is mixed with it a weighed quantity of the so-called ' carbide,' sufficient to furnish the proper amount of carbon to carry out the reaction indicated above. The crucibles in which this mixture is treated are made of cast-steel, and are capable of containing a charge of 15 lbs. of caustic soda, together with the proper proportion of the • carbide.' "After charging a crucible with the above mixture, it is placed in a small furnace where it is kept at a low heat for about thirty minutes, during which time the mass fuses, boils violently, and a large part of the hydrogen is expelled by the combined action of the iron and carbon, the ' carbide,' owing to its gravity, remaining in suspension throughout the fused soda. At the end of the time stated, the contents of the cru- cible have subsided to a quiet fusion. The crucible is then lifted by a pair of tongs on wheels and placed upon the plat- form of the elevating gear, as shown in the drawing, (Fig. 18) and raised to its position in the heating chamber of the main dis- tilling furnace. The cover which remains stationary in the fur- nace has a convex edge, while the crucible has a groove round the edge into which the edge of the cover fits. A little powdered lime is placed in the crucible groove just before it is raised, so that when the edges of the cover and crucible come together THE MANUFACTURE OF SODIUM. 209 they form a tight joint, and at the same time will allow the crucible to be lowered easily from the chamber when the ope- ration is finished, to give place to another containing a fresh charge. From the cover projects a slanting tube (see Fig. 18), connected with the condenser. The condenser is provided with a small opening at the further end to allow the escape of hydrogen, and has also a rod fixed (as shown), by means of which any obstruction which may form in the tube during dis- FlG. 18. tillation may be removed. After raising a crucible in its place in the furnace, the hydrogen escaping from the condenser is lighted, and serves to show by the size of the flame how the operation is progressing in the crucible, the sodium actually distilling soon after the crucible is in its place. The temper- ature of the reduction and distillation has been found to be about 823° C. The gas coming off during the first part of the distillation has been analyzed and found to consist of pure hydrogen. Analysis of the gas disengaged when the ope- 14 2IO ALUMINIUM. ration was almost completed, gave as a result, hydrogen 95 per cent., carbonic oxide 5 per cent. It has been found advisable to use a little more 'carbide' than the reaction absolutely re- quires, and this accounts for the presence of the small quantity of carbonic oxide in the expelled gas, the free carbon acting upon the carbonate formed by the reaction, thus giving off car- bonic oxide and leaving a very small percentage of the residue in the form of peroxide of sodium. This small amount of car- bonic oxide rarely combines with any of the sodium in the tube, and so the metal obtained in the condensers is pure, and the tubes never become choked with the black compound. In the preparation of potassium a little less ' carbide' is used than the reaction requires ; thus no carbonic oxide is given off, and all danger attached to the making of potassium is removed. After the reduction and distillation the crucible is lowered from the furnace and the contents poured out, leaving the crucible ready to be recharged. The average analyses of the residues show their composition to be as follows: — Carbonate of soda 77 per cent. Peroxide of sodium 2 " Carbon 2 " Iron 19 " " The average weight of these residues from operating upon charges of 15 lbs. caustic soda and 5^ lbs. of carbide is 16 lbs. These residues are treated either to produce pure crystal lized carbonate of soda or caustic soda, and the iron is recov- ered and used again with pitch in the formation of the ' car- bide.' From this residue weighing 16 lbs., is obtained 13 lbs. of anhydrous carbonate of soda, equivalent to 9.4 lbs. caustic soda of 76 per cent. " Operating upon charges as above mentioned the yield- has been — Sodium, actual 2.50 lbs. Theory 2.85 lbs. Soda carbonate, actual 13.00 lbs. " 13.25 lbs. " The average time of distillation in the large furnace has THE MANUFACTURE OF SODIUM. 2 1 I been i hour 30 minutes, and as the furnace is arranged for three crucibles, 45 lbs. of caustic soda are treated every 90 minutes, producing 7^ lbs. of sodium and 39 lbs. of carbonate of soda. The furnace is capable of treating 720 lbs. of caustic soda daily, giving a yield in 24 hours of 120 lbs. of sodium and 624 lbs. of anhydrous carbonate of soda. The furnace is heated by gas which is supplied by a Wilson Gas Producer, consuming I cwt. of fuel per hour. The small furnace in which the crucibles are first heated requires about J^ cwt. per hour. The following estimate of cost, etc., is given from the actual running of the furnace working with the above charges for 24 hours : — £ ^. d. 720 lbs. of caustic soda @ ;^i i per ton 3 10 10 1 50 lbs. of " carbide " @ yd^d. per lb o 6 4 Labor I o o Fuel o 17 o Re-converting 624 lbs. of carbonate into caustic, at a cost of about £^ per ton on the caustic produced, say ... I o o Total 6 14 2 Deducting value of 475 lbs. of caustic recovered 2 6 8 Cost of 120 lbs. of sodium ^4 7 6 Cost per pound, 83^T«" tion of sodium and chlorine (4247 calories per kilo of sodium) there is enough potential energy in a pound of coal to separate nearly two pounds of sodium, if any mode of applying the com- bustion of the coal to this end without loss could be devised. If, however, this energy is converted into mechanical work, this again into electrical energy, and this latter used to decompose sodium chloride, we can easily compute the amount of coal to be used in a steam boiler to produce a given amount of sodium by electrolysis. Now, if the electric current could be applied without loss in decomposing sodium chloride, i electric horse- power (746 Watts) would produce about 8 lbs. of sodium in 24 hours. But as in practice one mechanical horse-power ap- plied to a dynamo yields only 80 or 90 per cent, of an electric horse-power, and as about 4 lbs. of coal are used per indicated THE MANUFACTURE OF SODIUM. 221 horse-power per hour, from 105 to 120 lbs. of coal would be required per day to produce this result, or about 15 lbs. per lb. of sodium. Since, however, there is a transfer resistance in the passage of the electric current through the molten electrolyte, more than this will be required, in proportion to the amount of current thus absorbed. The temperature of fusion of sodium chloride is given by Carnelly as Tj6° C, but Prof. Rogers remarks that the fusing point may be lowered considerably by the presence of other salts ; for instance, it melts about 200° lower if a small amount of calcium chloride or potassium chloride is present. We will quote the results of some experiments as given by Prof. Rogers.* "The following results were obtained among many others by using a Grove battery, a Battersea crucible to hold the sodium chloride, a carbon anode and an iron cathode terminating in a tube of lime placed in the melted salt. As soon as metallic sodium escaped and burnt at the surface of the liquid the cur- rent was stopped. A little sodium was oxidized, but a consid- erable amount was found in the tube in the metallic state. In six experiments the amount of sodium obtained was from 50 to 85 per cent, of the theoretical amount, averaging 65 per cent. It thus seemed that, with suitable apparatus, from 5 to 6 lbs. of sodium could be obtained in 24 hours per electric horse-power. Thus, if there were no practical difficulties in the construction of the crucibles and other apparatus involved, nor in working continuously on a large scale, the metal could be obtained at small cost. Various forms of crucibles were used and attempts made to distil the metal when formed at the negative electrode (sodium volatilizing at about 900° C), but the sodium vapor carries with it a large amount of sodium chloride as vapor, and the distillation is attended with difficulty. " During the last three years I have experimented on the reduction of sodium chloride, using molten negative electrodes and especially lead. Lead, tin, zinc, cadmium and antimony * Proceedings of the Wisconsin Natural History Society, April, 1889. 222 ALUMINIUM. all readily .alloy, with sodium, a large part of which can be re- covered from the alloys by distillation in an iron crucible. They can be heated to a higher temperature than pure sodium in acid crucibles without the sodium attacking the crucible. In the following experiments a dynamo machine was used to sup- ply the current. "Experiment i. A current averaging 72 amperes and 33 volts was passed through molten sodium chloride contained in two crucibles arranged in series, for two hours. Each con- tained 30 lbs. of salt; in the first was put 104 grammes of tin, in the second 470 grammes of lead, each serving as cathode, and connection being made through the bottom of the crucible. A carbon anode passed through the cover and extended to within three inches of the molten cathode. The crucible con- taining the tin was nearer the fire and consequently hotter, and had an average potential across the electrodes of 12 volts, while that containing the lead cathode was 21 volts. When at the end of two hours the carbons were removed and the cru- cibles cooled and broken open, the lead alloy was found to contain 96 grammes of sodium, or 17 per cent. There was about 90 grammes of sodium found in the tin alloy, or between 45 and 50 per cent. Both these alloys rapidly oxidized in the air, and when thrown into water the action was very energetic, in the case of the tin alloy the liberated hydrogen being ignited, and after the reaction the metals were found at the bottom of the vessel in a finely divided state. Both these alloys reduce cryolite or aluminium chloride." In Prof. Rogers' further experiments cryoHte was added to the bath, so that sodium was produced and aluminium formed in one operation. (See under "Electrolytic Processes," Chap. XI.) L. Grabau, of the " Aluminium Werke zu Trotha," has made the following observations on the electrolysis of molten sodium chloride. When the melted, salt is subjected to the electric current, the resistance of the bath quickly rises and it becomes almost inipossible to force the current through, This THE MANUFACTURE OF SODIUM. 223 is probably due to the formation of a non-conducting sub- chloride. The formation of this salt can be prevented by the addition of some potassium chloride and the chloride of an alkaHne-earth metal to the bath. In his patents,* Grabau recommends the use of a mixture of sodium, potassium and strontium chlorides, in the proportion of 88 sodium chloride, 112 potassium chloride, and 159 strontium chloride. With this mixture, Grabau claims to obtain almost pure sodium, contain- ing only about 3 per cent, of potassium and no trace of strontium, while at the same time 95 per cent, of the metal which the current should theoretically give is obtained. For all the purposes to which sodium is now applied the presence of the potassium is not in the least prejudicial. Borchers sub- stantiates the fact that from a mixture of potassium and sodium chlorides, which is very fluid, only sodium is liberated by the current if it is not too strong and if the sodium chloride de- composed is at once replaced. For carrying on his process, Grabau uses the apparatus shown in Fig. 22. The positive poles are carbon rods (C), the negative an iron pipe E, slit in its lower part and surrounded by a bell-shaped porcelain cover B. As the molten sodium is lighter than the bath material, it rises into the pipe £ and passes away through the branch a into a condenser where it collects under petroleum. The screw H can be turned downwards to clean out the tube E in case it stops up. It is intended that the vessel should be heated by hot gases passing through the flues G G, and its temperature so regulated that the sodium passes off in the liquid state. The chlorine generated passes off by the tube d. In order to pre- vent the corrosion of the cover B, Grabau has even con- structed an apparatus in which it contained an iron lining and was water-cooled. The method now used by Castner .consists in electrolyzing molten caustic soda at the lowest possible temperature. Pure caustic soda melts below redness, and if kept at a temperature ♦German Patents (D. R. P.) Nos. 51898 and 56230 (1890). 224 ALUMINIUM. not more than 20° above its melting point (310° C), it can be easily and continuously electrolyzed. Arrangements must therefore be provided for keeping the temperature of the bath very constant, and for removing the sodium quickly from the bath in order to prevent loss by corrosion. The apparatus consists of an iron crucible, embedded in brickwork, in which Fig. 22. the caustic soda is melted by the heat of a circular gas burner surrounding the pot (Fig. 23). The negative electrode passes up through the bottom of the pot, the space between it and the sides of the hole being allowed to fill up with solid caustic. A tubular sleeve of iron descends from the cover and envelopes the top of this electrode. Outside of this are the positive elec- trodes. An opening is provided in the cover for the escape of THE MANUFACTURE OF SODIUM. 225 gas and introduction of a thermometer. In operation, the heat caused by the passage of the current is sufificient to keep the bath melted. The free sodium floats on the surface of the bath inside the iron sleeve surrounding the negative electrode, and is skimmed off with a small ladle having fine perforations. The operation is continuous, and afifords sodium at a cost probably not greater than 15 cents per pound. IS CHAPTER VIII. THE REDUCTION OF ALUMINIUM COMPOUNDS FROM THE STANDPOINT OF THERMAL CHEMISTRY. The branch of chemical science called thermal chemistry may be said to be yet in its infancy. Although an immense mass of thermal data has been accumulated, yet the era of great generalizations in this subject has not yet been reached ; and although we know with a fair degree of accuracy the heat of combination of thousands of chemical compounds, including nearly all the common ones, yet the proper way to use these data in predicting the possibility of any proposed reaction re- mains almost unknown. The principal barriers in the way are two: 1st, the unknown quantities entering into almost every chemical reaetion thermally considered, i. e., the heat of com- bination of elementary atoms to form molecules of the ele- ments ; 2d, the uncertainty as regards the critical temperature at which a given exchange of atoms and consequent reaction will take place. We will explain what is meant by these state- ments. To illustrate, let us consider the case of hydrogen uniting with oxygen to form water according to the formula — 2(H— H) -I- (0= 0)= 2H,0 where (H — H) and (O ^ O) represent respectively molecules of hydrogen and oxygen. Now, as i kilo of hydrogen unites with 8 of oxygen to form 9 of water, setting free 34,462 units of heat (calories), if we take the atomic weights in the above reaction as representing kilos, we shall have the thermal value of the reaction 4 X 34,462 = -|- 137,848 calories. But this' quantity is evidently the algebraic sum of the heat evolved in (226) REDUCTION OF ALUMINIUM COMPOUNDS. 22/ the union of 4 kilos of hydrogen atoms with 32 kilos of oxygen atoms, and the heat absorbed in decomposing 4 kilos of hydro- gen gas into atoms! and 32 kilos of oxygen gas into atoms. These two latter quantities are unknown, though a few chem- ists have concluded from studies on this question that they are probably very large. It has been calculated that the reaction H -|- H = (H — H) sets free 240,000 calories, and 4-0^ (O = O) sets free 147,200 calories ; If these numbers are approximately true, then 4H + 20^ 2H2O would set free about 773,000 calories. If these quantities are really anything like so large, and if they are at sometime determined with precision, thermo-chem- ical principles and conclusions will be greatly modified. Mean- while, predictions based on the data we have, lose all possibility of certainty, and so we need to keep in mind in our further discussion that our deductions at the best are only probabil- ities. Further, suppose that we mix i kilo of hydrogen gas and 8 kilos of oxygen gas, put them in a tight vessel and keep them at the ordinary temperature. No reaction will take place in any length of time, even though 34,462 calories would be set free thereby. The explanation of this is that the atoms of hydrogen and oxygen are so firmly bound to each other in the molecules, that the dissimilar atoms have not strength of afiSnity sufiScient to break away in order to combine. It is well known that a spark only is necessary to cause an explosive combina- tion of the gases under the above conditions, the temperature of the spark expanding the gases coming in contact with it, causing the atoms to swing with more freedom in the molecules ; and as soon as two atoms of hydrogen come within the .sphere of attraction of an atom of oxygen and form a molecule of water, the heat liberated is immediately communicated to the adjacent atoms, and almost instantaneously the entire gases have combined. The same principle undoubtedly holds true 228 ALUMINIUM. in cases of reduction. Carbon may be mixed with litharge and the mixture left in the cold forever without reacting, but at a certain temperature the carbon will abstract the oxygen. The temperatures at which reactions of this nature will take place are often determined experimentally. There are other points which are somewhat indeterminate in these discussions, such as the influence of the relative masses of the reacting bodies, their physical states, i. e., solid, liquid or gaseous, also the influence of the physical conditions favor- ing the formation of a certain compound ; but the nature of the subject and the meagreness of data in the particular pheno- menon of reduction, render it inexpedient if not impracticable to take these points into consideration. Starting with the above remarks in view, we will consider the heat generated by the combination of aluminium with certain other elements, as has been determined experimentally, and study, from a comparison with the corresponding thermal data for other elements, what possibilities are shown for reducing these aluminium compounds. The heat generated by the combination of aluminium with the different elements is given as follows : the first column giv- ing the heat developed by 54 kilos of aluminium (representing AI2), and the second the heat per atomic weight of the other element, e. g., per 16 kilos of oxygen. Element. Compound. Calories. Calorie.s. Authority. Oxygen * Al^Oj 391,600 130,500 Berthelot. 392,600 130,900 Bailie & F^ry. Fluorine 2AIF3 552,000 92,000 Berthelot. Chlorine 2AICI3 321,960 53,66o Thomsen. Bromine 2AlBr3 239,440 39,900 " Iodine 2AU3 140,780 23,460 " Sulphur AI2S3 124,400 41,467 Sabatier. * Berthelot's number represented the formation of the hydrated oxide, AIJO3.3H2O, and, for want of knowing the heat of hydration, has been generally used as the heat of formation of AljOj. Recently, J. B. Bailie and C. F4ry (Ann. de Chim. et de Phys., June, 1889, p. 250) have, by oxidizing aluminium amalgam, obtained the above figure for the heat of formation of AI2O3, and determined that the beat of hydration is 3000 calories, which would make the heat of formation of the hydrated oxide 395,600. REDUCTION OF ALUMINIUM COMPOUNDS. 229 Let US consider the theoretical aspect of the reduction of alumina. The heat given out by other elements or com- pounds which unite energetically with oxygen is as follows, the quantity given being that developed by combination with 16 kilos (representing one atomic weight) of oxygen. Element. Compound. Calories. AlTiminlum AljOj 130,500 Sodium Na.p 99, 760 Potassium Kfi 100,000 ( ?) Barium BaO 124,240 Strontium SrO 1 28,440 Calcium CaO 130,930 Magnesium MgO 145,860 Manganese MnO 95,ooo ( ?) Silicon SiOj 1 10,000 Zinc ZnO 85,430 Iron FejOj 63,700 Lead PbO 50,300 Copper CuO 37>i6o " CU2O 40,810 Sulphur SO2 35.540 Hydrogen H^O 68,360 Carbon CO 29,000 " COj 48,480 Carbonic anhydride CO^ 67,960 Potassium cyanide KCyO 72,000 On inspecting this list we find magnesium to be the only metal surpassing aluminium, while calcium is about the same. This would indicate that the reaction AlA + 3Mg = Al, + 3MgO would, if it were possible to bring the alumina and magnesium in the proper conditions for reacting, develop about (145,860 — 130,500) X 3 = 46,080 calories, and points to the possibility of reducing alumina by nascent, molten, or vaporized magnesium, under certain conditions. In fact, since this paragraph was first written, in 1890, Dr. Clemens Winkler has succeeded in performing the reduction in part.* * Berliner Berichte, 1890, p. 772. 230 ALUMINIUM. He found that when alumina was heated with magnesium pow- der in a current of hydrogen, a nearly black powder resulted, containing a lower oxide of aluminium, AlO, the reaction being 2AI2O, + Mg = MgO.AljO, + 2AIO ; the magnesia formed uniting with alumina to form an alum- inate. We notice further the fact that sodium or potassium could not reduce alumina without heat being absorbed in large quantity, and it is interesting to remember that some of the first attempts at isolating aluminium by using potassium were made on alumina, and were unsuccessful, so that it is practi- cally acknowledged that while these metals easily reduce other aluminium compounds (according to reactions which are ther- mally possible, as we shall see later on) yet they cannot reduce alumina, under any conditions so far tried. When we consider the case of reduction by the ordinary re- ducing agents, hydrogen, carbon, or potassium cyanide, we are confronted in every case with large negative quantities of heat, i. e., deficits of heat. So large do these quantities appear that it is very small wonder that the impossibility of these reduc- tions occurring under any conditions has been strongly affirmed, For instance Al203-f-6H=AU-|-3H,0 would require (130,500 — 68,360) X 3 = 186,420 calories. AI2O3 + 3C =Alj -I-3CO 304,500 calories. AI2O3 + i>^C = AI2 -h ii^COa 246,060 calories. Al,03 -I- 3KCy = Al, + 3KCyO 175,500 calories. AlA +3CO =h\ + 7,C0, 187,620 calories. The above quantities represent the differences between the heats of formation of alumina and the product of the reduc- tion, assuming the reaction to take place at ordinary temper- atures. At high temperatures these heats of formation are in REDUCTION OF ALUMINIUM COMPOUNDS. 23 1 general less than they would be at low heats, and if the heat of formation of alumina decreases faster than .the heat of combi- nation of the reducing agent with oxygen, the dififerences noted above would be less and the reaction easier to produce. This must be what actually takes place. For instance, at the heat of an electric furnace, say 2500° to 3000°C., molten alumina is reduced by carbon present in large quantity, that is, the dif- ference beiween the heats of formation of AI2O3 and 3 CO has become so small that the reaction takes place. Similarly, Warren has recently reduced alumina by heating it in a lime tube by an oxy-hydrogen blow-pipe, passing hydrogen through the tube. We here have a reaction which is negative by 186,- 000 calories at ordinary temperatures, taking place at a tem- perature probably not over 2000°C. The conditions which render the carrying out of these diffi- cult reductions possible are therefore : 1 . A high temperature, which weakens the heat of formation of alumina. 2. An excess of the reducing agent, which is thus assisted simply by the overpowering influence of its mass. 3. Fluidity of the substance to be reduced. 4. Intimate contact with the reducing agent. 5. Favorable conditions for the formation and removal of the gaseous products of the reduction. Concerning these, I would remark that the fluidity of the sub- stance to be reduced may be attained by other means than a high temperature. The alumina may, for instance, be liquefied by solution in a bath of molten cryolite. If we dissolve it in molten caustic soda we get a combination of alumina and soda which will remain fluid if too much alumina is not added. Such fluidity also allows much more intimate contact with the reducing agent if it is a solid. . If the reducing agent is a gas, most intimate contact is obtalined by finely pulverizing the alu- mina. If the reducing agent is a solid and the product of the reduction would be a gas, its formation would be accel- erated by reducing the pressure in the apparatus. In other 232 ALUMINIUM. words, a partial vacuum would undoubtedly aid in bringing about the reduction, and would help to keep the aluminium in the metallic state by removing quickly the product of reduction and so preventing re-oxidation. I have no hesitation in affirm- ing that since we now know that carbon does reduce molten alumina below 3000°, and hydrogen reduces solid alumina at 2000°, the application of correct principles by intelligent inves- tigators, with properly constructed apparatus, would undoubt- edly result in discovering methods of producing the same reac- tions at lower temperatures and on a larger scale. Whether these methods of producing aluminium could compete with the present electrolytic ones is another question, but it is certainly interesting to mark the possibility of processes which some future investigator may bring to commercial success. As the basis of our discussion of the reduction of aluminium chloride, bromide, or iodide, we give a table of heat developed by the combination of some of the elements with one atomic weight (in kilos) of each of these haloids. Element. Com- pound. Calories. Com- pound. Calories. Com- pound. 53>66o AlBrj 40,000 AII3 105,600 KBr 95.300 KI 97,690 NaBr 85,700 NaT 93.810 BaBr^ 97.37° SrBr^ 85,000 92,270 CaBr^ 78,900 84,910 70,400 75.5°° 56,000 f 5o,6oot 1 48,600* jZnBr, f43.ioot ] 40,640t I 37.500* [znP 41,380 PbBrj 32,200 Pblj 41.275 H&Br, 34.150 Hg,I, 40,400 41,000 FeBrj 24,000 Felj 32.87s Cu^Br^ 25,000 C%I, 22,000 HBt 8,400 HI Calories. Aluminium Potassium . . Sodium Lithium .... Barium .... Strontium . . Calcium .... Magnesium. Manganese . Zinc Lead Mercury . . . • Tin Iron Copper . . . . Hydrogen. . AlCl, KCl NaCl LiCl BaClj SrClj CaClj MgCL, MnCL, ZnClj PbCl^ Hg,Cl, SnCL, FeCl., CuoCl.^ HCl 23,460 80,100 69,000 f 30,coot ■j 26,600 (. 24,500 20,000 24,200 8,ooot 16,000 — 6,000 *Thomsen. t Andrews. J Jahresbericht der Chemie, 1878, p. 102, On inspecting this table we notice that, in general, all the REDUCTION OF ALUMINIUM COMPOUNDS. 233 metals down to zinc develop more heat in forming chlorides, and very probably also in forming bromides and iodides, A re- action, then, between aluminium chloride and any of these metals, forming aluminium and a chloride of the metal, would be exothermic, which means, generally speaking, that if alu- minium chloride and any one of these metals were heated to- gether to the critical point at which the reaction could begin, the reaction would then proceed of itself, being continued by the heat given out by the first portions which reacted. Zinc seems to lie on the border line, and the evidence as to whether zinc will practically reduce these aluminium compounds is still con- tradictory, as may be seen by examining the paragraphs under " Reduction by Zinc." (Chap. XII.) Of the first six metals mentioned in the table after aluminium, only potassium and sodium are practically available. The re- action AlCl3 + 3K = AH-3KCl develops 155,820 cal. AlCls-F 3Na = Al-f- 3NaCl develops 132,090 cal. and the result of this strong disengagement of heat is seen when, on warming these ingredients together, the reaction once commenced at a single spot all external heat can be cut off, and the resulting fusion will become almost white hot with the heat developed. In fact, the heat developed in the second reaction would theoretically be sufficient to heat the aluminium and sodium chloride produced to a temperature between 3000° and 4000°. Magnesia should act in a similar manner, though not so vio- lently, since 2AlCl3 + 3Mg=Al2 + 3MgCl2 develops 131,000 cal. And manganese possibly also, since 2AICI3 + 3Mn = Ala -f- 3MnCl develops 14,040 cal. The reduction of aluminium chloride, bromide, or iodide by hydrogen is thermally strongly negative, which would indicate a very small possibility of the conditions ever being arranged so 234 AXUMINIUM. as to render the reaction possible. For instance, taking the most probable case, AICI3 + 3H = Al + 3HCI requires 94,980 calories. The only probable substitutes for sodium in reducing alumin- ium chloride are thus seen to be magnesium (whose cost will probably be always greater than that of aluminium), manganese (which may sometime be used in the form of ferro-manganese for producing ferro-aluminium), and zinc (whose successful application to this purpose would be a most promising advance in the metallurgy of aluminium). In 1886 Moissan isolated fluorine, and in 1889 he and Berthe- lot measured the heat of formation of hydrofluoric acid. With this datum, it became possible to calculate a table of the heat of formation of the fluorides.* These can now be given as follows, stating the heat evolved by combination with one atomic weight (19 kilos) of fluorine. Element. Compound, Heat evolved. Potassium KF 1 10,000 Sodium NaF 109,700 Barium BaF^ 112,000 Strontium SrFj 112,000 Calcium CaF, 108,000 Magnesium MgFj 105,000 Aluminium AIF3 92,000 Manganese MnFj 72,000 Zinc ZnFg 69,000 Cadmium CdF^ 61,000 Iron FeF^ 63,000 Cobalt C0F2 60,000 Nickel NiFj 59,500 Copper CuFj 44,000 Silver AgF 25,500 Hydrogen HF (gas) 37,6oo " " (in solution) 49,400 It follows from an inspection of these quantities that the fluorides are stronger compounds than either the oxides, chlor- ides, bromides or iodides. It is also seen that aluminium * See a paper on this subject, by the author, in the Journal of the Franklin Insti- tute, June, 1891. REDUCTION OF ALUMINIUM COMPOUNDS. 235 stands in the same relative position as in the chlorides, except that it is here stronger than manganese or zinc. It follows that only sodium, potassium or magnesium of the available metals wilU reduce aluminium fluoride. For such reductions the latter must be liquefied by mixture with a fusible salt not acted on by the reducing agent. Thus, we* would have 2AIF3 + 6Na= 6NaF+ 2AI, evolving 106,200 calories. 2A1F3 + 3Mg = 3MgF2 + 2AI, evolving 78,000 calories. The reaction with zinc would absorb heat as follows : 2AIF3 + 2Zn= 2ZnF2 + 2 Al, absorbing 138,000 calories. While the first two reactions take place easily, at a red heat, the latter is nearly impracticable. The writer brought zinc into contact with highly heated cryolite (AlFj.sNaF), and obtained 0.6 per cent, of aluminium in the zinc* The temperature was a bright red, and this small amount of reduction shows that an excess of zinc at a high temperature will to a small extent over- come the affinity of aluminium for fluorine. Manganese in the form of ferro-manganese, might take up even a larger percent- age of aluminium than the above, yet no substantial amount of reduction can be looked for from these elements. In order to discuss the thermal relations of aluminium sul- phide, we will make use of the following data, the heat devel- oped being per atomic weight (32 kilos) of sulphur combining: Element. Compound. Calories. Alumlnitiin AI283 41,467 Potassium KjS 103,700 Sodium Na^S 88,200 Calcium CaS 92,000 Strontium SrS 99,200 Magnesium MgS 79,600 Manganese MnS 46,400 Zinc ZnS 41.326 Iron FeS 23,576 Copper Cu^S 20,270 Lead • PbS 20,430 Hydrogen HjS 4>740 Carbon CSj —14,500 * See details in Chapter XII. 236 ALUMINIUM. These figures point to the easy reduction of aluminium sul- phide by potassium, sOdium, or magnesium, and its possible reduction by manganese and zinc. The other metals would require exceptional conditions, perhaps, of temperature, for their action. It is interesting to note that two observers have determined from the deposition -of the metals from solution by hydrogen sulphide, that the order of the afifiinity of the metals for sulphur is first the alkaline metals, then the others in the following order: copper, lead, zinc, iron, manganese, and then aluminium and magnesium — with the remark that the affiinities of the latter two for sulphur appear quite insignificant. The explanation of this difference is that the metals last mentioned form sulphides which are not stable in water, but are immedi- ately decomposed according to the reaction 3 AI2S3 + 3 H2O = AI2O3 + 3H2S, evolving 77,840 calories, while the alumina produced is immediately soluble in the weak acid solution and at once disappears. It follows that these ele- ments are not precipitated as easily from solution as those whose sulphides are not thus decomposed by water. The reduction of aluminium sulphide by copper, tin and iron is in a measure possible when the operation is conducted at a high temperature and there is an excess of reducing metal present. Under these conditions, a part of the aluminium sul- phide is reduced and an alloy formed, but such reactions can- not approach in completeness those reactions which are strongly endothermic. The reduction by hydrogen is seen to be highly improbable, and by carbon still more so. The question of reducing aluminium compounds by the use of electricity is a very different question. Looked at as a reduc- ing or decomposing agent, the electric current is almighty. A current with a tension of i volt will decompose any fluoride, chloride, bromide or iodide whose heat of combination with one atom weight of fluorine is less than 23,000 calories ; at a tension of two volts, any less than 46,000 calories ; and therefore at a tension of five volts would decompose the strongest of any of REDUCTION OF ALUMINIUM COMPOUNDS. 237 these salts. Such a current only means half a dozen ordinary copper sulphate batteries connected in tension. For oxides and sulphides, the heat of combination with one-half an atomic weight must be used, which quantity is equal in combining power to one whole atomic weight of the above elements, and then the same rule applies. We can thus calculate the voltage required to decompose the following anhydrous molten com- pounds — » Element. Fluoride. Chloride. Oxide. Sulphide. Potassium 4.8 4.6 2.2 2.3 Sodium 4.7 4.3 2.2 1 .9 Barium 4.9 4.3 2.7 2.2 Strontium 4.9 4.0 2.75 2.2 Calcium 4.7 3.7 2.85 2.0 Magnesium 4.6 3.3 3.2 1.7 Aluminiuin 4.0 2.3 2.8 0.9 Manganese 3.1 2.4 2.1 l.o Zinc 3.0 2.3 1 .9 0.9 Iron 2.7 1.8 1.5 0.5 Nickel 2.5 1.6 1.3 0.4 Copper 1.9 1.4 0.9 0.4 Silver i.i 1.3 o.l o.i Hydrogen 1.6 i.o 1.5 0.1 A critical comparison of these figures leads to some very in- teresting conclusions. We notice, in the first place, that in the fluorides there is a very sharp drop after aluminium ; in these salts aluminium has closer resemblance to the alkaline earth fluorides, while manganese and zinc resemble the ordinary metals. In the chlorides, there is a sharp drop before alumin- ium, leaving it in stronger resemblance to the zinc, manganese and lower metallic salts. In the oxides, aluminium is again classed with the alkaline earth metals, and sharply separated from the lower metallic oxides. Attention is particularly called to the irregularity of the alkaline metals, whose oxides are as easily decomposed as those of the metals below aluminium. This explains why we can reduce these alkaline metals more easily by carbon than we can alumina, and yet we can use the alkaline metal to react on a salt of aluminium and get metallic 238 ALUMINIUM. aluminium. The high voltage required to decompose mag- nesium oxide also explains the wonderful efficiency of mag- nesium as a reducing a:gent when acting on the oxides. In the list of sulphides, we again notice a sharp drop before alumin- ium, leaving it in close correspondance with manganese and zinc. The very low voltage required is also noticeable ; a single Daniell cell should be able to produce decomposition. Take a bath, for instance, in which alumina is being decom- posed using a tension of 5 volts, of which 2.8 is absorbed in decomposition and 2.2 in overcoming other resistances. If aluminium sulphide were the material decomposed, assuming other resistances the same as before, the total resistance of the bath would be overcome by 3.1 volts; or, in other words, it would require only 62 per cent, of the power to produce the same weight of aluminium. The sulphide thus presents great advantage in respect to ease of decomposition. Next to the sulphide, the chloride is the easiest to decom- pose, but both these salts are difficult to produce, and herein lies their chief disadvantage. It can be furthermore observed, that if we mix these various salts into one bath, and use an electric current carefully regu- lated as to tension, we can act on pne ingredient without dis- turbing to any extent the others present. We could, for instance, mix aluminium chloride with any fluoride down to that of zinc, and by a tension of 2.5 volts or a little over sepa- rate out only alumininum. We could mix alumina with any fluoride or chloride above aluminium in the list, and get only aluminium from the bath. The fact is, however, that alumina is not dissolved by the chlorides, but only by the fluorides. These latter are therefore available, and are the principal salts used at present in the aluminium industry. Thus, in Hall's process we have present in the bath Alumina requiring 2.8 volts for decomposition. Aluminiunl fluoride " 4.0 " " Sodium '■ " 4.7 . " , •' When the current is passed through such a mixture, and its REDUCTION OF ALUMINIUM COMPOUNDS. 239 tension does not rise abnormally high,' the bath being kept sat- urated with all the aluimina it can dissolve, the only ingredient decomposed is the alumina. In Minet's process there are present : Alumina, requiring 2.8 volts. Aluminium fluoride, " 4.0 " Sodium fluoride, " 4^7 " Sodium chloride, " 4.3 " The minimum electro-motive force required to decompose this bath at 900° is 2.4 volts; at 1100°, 2.17 volts. The elec- tro-motive force of carbon burning to carbonic oxide at those temperatures is, however, 0.65 volts, so that the voltage re- required to decompose liquid alumina at these temperatures is 0.65 volts higher than the figure given. We therefore have these data for the decomposition of alumina : Voltage for Temperature. Decomposition. Heat of Formation. 0° 2.82 392,600 (solid aluminium.) 0° 2.78 387,200 (liquid aluminium). 900° 3-05 424,600 (liquid aluminium). 1100° 2.82 392,600 (liquid aluminium). The equation for the voltage required to decompose alumina producing liquid aluminium is therefore : V^ 2.78 + 0.00129 t — 0.00000128 1'', and the heat required to decompose the molecule of alumina is Q = 387,200+ 192 t — 0.1766 1^ This formula is extremely interesting from a thermo-chemi- cal point of view in enabling us to calculate theoretically the temperature at which hydrogen or carbon begins to reduce alu- mina. The heat of formation of gaseous water ,at zero is accu- rately known, and the experiments of Mallard and Le Chatelier on the specific heats of hydrogen, oxygen and water vapor enable us to calculate the heat of formation at any desired tern- 240 ALUMINIUM. perature. From these data we calculate the heat of formation of 3HjO to be represented by the formula: Q = 174,300+ 7.71 t — 0.0072 t\ Now to find the temperature at which hydrogen gas would be- gin to reduce alumina, we equate this formula with the one given for the heat of the formation of alumina, and have 387,200 + 192 t — 0.1766 t''= 174,300+ 7.71 t— 0.0072 t'' from which t = i785°C. This will be the temperature at which the heat of formation of 3H2O will be exactly equal to the heat of formation of Al^Oj, and consequently immediately above this temperature reduc- tion will begin if the physical conditions are favorable for the reaction taking place. On a similar principle we can calculate the temperature at which carbon will begin to reduce aluminium, except that the operation is more difficult because of the variable specific heat of carbon. I have calculated from Weber's results that the heat in carbon from zero to high temperatures may be expressed as Q = o.5 t — 120. Taking this quantity, in connection with the specific heats of oxygen and carbonic oxide as determined by Mallard and Le Chatelier at high temperatures, we have for the heat of forma- tion of 3CO at any temperature t above 1000°, the expression Q = 83.35s + 8.6472 t - 0.0009 t^ For finding the temperature at which reduction begins we have 387,200 + 192 t — 0.1716 t'' = 83,355 + 8.6472 t — 0.0009 ^^ from which t = 1980°. REDUCTION OF ALUMINIUM COMPOUNDS. 24 1 The temperatures above calculated appear much lower than has heretofore been deemed possible, but they are supported by experimental evidence ; viz., the reduction of alumina by hydrogen performed by Warren, at a temperature which it is hardly possible could have been higher than 2000° ; and the production of pig-iron containing over i per cent, of aluminium in a Pennsylvania blast furnace. The highest temperature at- tained in this furnace, not of very modern construction, could not have exceed 2000° C. (For details, see Chapter XII.) If in place of free hydrogen gas or free carbon we use as a reducing agent a combination of these two which gives out heat in its dissociation into carbon and hydrogen, we would have a more efficient reducing agent than if the constituents were used separately. Such a compound is Acetylene, CjHj, which ab- sorbs heat in its formation and therefore gives out heat in its decomposition. At ordinary temperatures, Berthelot has found that C2 + H2 = C.2H.2 absorbs 5 1,500 calories. We do not know exactly how this number varies with the tem- perature, as we lack the specific heat of CJ-Ij, but we know that it does not change very much. We would therefore have the reduction equation as follows — AI2O3 + C.,H2 = 2AI + 2CO -I- H,0 and the heat requirements as follows — Reducing AljOa ■• 387,200 -|- 192.61— 0.17161'' (l) Developed in forming 2CO 55.57° -f- S-76t — o.ooo6t'' (2) " " « HjO 58,000-1- 2.571— 0.00251^ C3> " " decomposing CijHj. 51,500 (4) If we put (i) = (2) + (3) + (4) and solve for t, we obtain the theoretical temperature at which Acetylene should begin to reduce alumina as t=-i87o°C. This temperature, it will be observed, is not so low as that 16 242 ALUMINIUM. calculated for pure hydrogen. Six months ago, this calculation would have been of purely scientific interest, because pure acetylene was a difiScult substance to procure ; but a very prac- tical interest has been given it by the recent invention of Mr. Thomas L. Willson of Brooklyn*, whereby pure acetylene can be manufactured at a cost approximating 2 cents per pound. Since the gas should theoretically reduce double its weight of aluminium, if perfectly utilized for reduction, the cost of the re- ducing agent per pound of aluminium would be very small. It is to be hoped that the possibility of the above reaction may be tested with this powerful reducing agent. Before closing this subject of the thermal aspect of the reduc- tion of aluminium compounds, it may be interesting to notice some of the reactions which are of use in the aluminium indus- try. It is well known that while chlorine gas can be passed over ignited alumina without forming aluminium chloride, and while carbon can be in contact with alumina at a white heat without reducing it, yet the concurrent action of chlorine and carbon will change the alumina into its chloride, a compound with a lower heat of formation. Thus — AL^Os -f- 3C = AI2 4- 3CO requires 304,500 cal. But AI2O3 + 3C + 6C1 = 2AICI2 + 3CO requires a quantity of heat equal to the 304,500 cal. minus 321,960, the heat of for- mation of aluminium chloride, or in other words, 17,360 cal. is evolved, showing that the reaction is one of easy practicability. If it be inquired whether there is not some chloride which would act on alumina to convert it into chloride, we would re- mark that if we can find a chloride whose heat of formation is as much greater than the heat of formation of the correspond- ing oxide as the heat of formation of aluminium chloride is greater than that of alumina, then such a chloride might react. * See description in Engineering and Mining Journal, Dec. 15, 1894. REDUCTION OF ALUMINIUM COMPOUNDS. 243 To be more particular, to convert alumina into aluminium chloride, a deficit of 391,600 — 321,960 = 69,640 calories must be made up. If we know of an element which in uniting with 3 atom weights (48 kilos) of oxygen gives out 69,640 calories more heat, or a still greater excess, than in uniting with 6 atom weights (213 kilos) of chlorine, then the chloride of that ele- ment might perform the reaction. Now — 6Na + 3O = sNajO evolves 299,280 cal. and 6Na + 6C1 =6NaCl evolves 586,140 cal. leaving evidently a balance of 286,860 calories in the opposite direction to what we are looking for. And so for every metal except aluminium, I find the heat of formation of its chloride greater than an equivalent quantity of its oxide. The only element which I know to possess the opposite property is hydrogen, for — 6H + 3O — 3H2O evolves 205,080 cal. and 6H + 6C1 = 6HC1 evolves 132,000 cal. and therefore the reaction — AI2O3 + 6HC1 = 2AICI3 + 3H2C would evolve according to our calculations (205, 080 — 132,000) — 69,640=3,440 calories, and would be thermally considered a pos- sible reaction. Moreover, as a secondary effect, the water formed is immediately seized by the aluminium chloride, for the reaction 2AICI3 + 3H2O = 2AICI3.3H2O evolves 153,690 cal. and thus increases the total heat developed in the decom- position of the alumina to 158, [30 calories. The result of this reaction is therefore the hydrated chloride, which is of no value for reduction by sodium, since when heated it decom- poses into alumina and hydrochloric acid again, that is, it will decompose before giving up its water, and the water if unde- composed, or the acid if it decomposes, simply unites with the 244 ALUMINIUM. sodium without affecting the alumina. The immense heat of hydration, 153,690 calories, is so much greater than any other known substance, that it is vain that we seek for any material which might abstract the water and leave anhydrous aluminium chloride. Analagous to the reaction by which aluminium chloride is formed from alumina is the reaction made use of for obtaining aluminium sulphide, yet with some thermal considerations of a different and highly interesting kind. If a mixture of alumina and carbon is ignited and, instead of chlorine, sulphur vapor is passed over it, no aluminium sulphide will be formed. An ex- planation of this fact is seen on discussing the proposed reac- tion thermally. AI2O3 + 3C -I- 3S = AI2S3 + 3CO requires 180,200 cal. It will be remembered that the similar reaction with chlorine evolved 17,360 calories; the quantity causing this difference is the heat of combination of aluminium sulphide, which is 321,960 — 124,400 = 197,560 calories less than that of aluminium chloride, changing the excess of 17,360 calories into a deficit of 180,200 calories. This large negative quantity shows a priori that the reaction could be made to occur only under excep- tional conditions, and its non-occurrence under all conditions so far tried gives evidence of the utility of the study of thermo- chemistry, at least as a guide to experiment. However, while carbon and sulphur cannot convert alumina into aluminium sul- phide, carbon bisulphide can, for a current of the latter led over ignited alumina converts it into aluminium sulphide. The re- action taking place is Al^Oa + 3CS2 = A1,S3 + 3COS. Now, since carbon and sulphur by themselves could not per- form the reaction, we should be very apt to reason that a com- pound of carbon and sulphur would be still less able to do so, since the heat absorbed in dissociating the carbon-sulphur REDUCTION OF ALUMINIUM COMPOUNDS. 245 compound would cause a still greater deficit of heat. But here -is precisely the explanation of the paradox. Carbon bisulphide is one of those compounds, not frequent, which has a negative heat of formation ( — 29,000 calories), i. e., heat is absorbed in large quantity in its formation, and therefore, per contra, heat is given out in the same quantity in its decomposition. The heat of formation of carbon oxysulphide being 37,030 calories, we can easily compute the thermal value of the reaction just given. Ifeat absorbed. Decomposition of alumina 391,600 cal. Heat developed. Decomposition of carbon bisulphide 87,000 Formation of carbon oxysulphide 1 1 1,090 " of aluminium sulphide 124,400 322,490 cal. Deficit of heat 69,1 10 " It is thus seen that the reaction with carbon bisulphide is less than one-half as strongly negative as the reaction with car- bon and sulphur alone, and we therefore have an explanation of the fact that the reaction with carbon bisulphide is easily practicable, while the other is not. We do not know enough about the variation of the heats of formation of aluminium sul- phide and carbon oxysulphide to be able to make calculations as accurately as was possible with the question of reducing alu- mina, but if all the heats of formation remained constant except that of alumina, the 69,000 calories deficit would be made up by the decrease in the heat of formation of chat substance at 975O C, which is somewhere about the temperature at which the reaction really takes place. CHAPTER IX. REDUCTION OF ALUMINIUM COMPOUNDS BY MEANS OF POTASSIUM OR SODIUM. The methods comprised under this heading may be con- veniently divided into two classes : — I. Methods based on the reduction of aluminium chloride or aluminium-sodium chloride. II. Methods based on the reduction of cryolite or aluminium fluoride. I. The methods here included can be most logically presented by taking them in chronological order. Oerstedt's Experiments (1824). After Davy's unsuccessful attempts to isolate aluminium by the battery, in 1807, the next chemist to publish an account of attempts in this direction was Oerstedt, who published a paper in 1824 in a Swedish periodical.* Oerstedt's original paper is thus translated into Berzelius's " Jahresbericht :"f " Oerstedt mixes calcined and pure alumina, quite freshly prepared, with powdered charcoal, puts it in a porcelain retort, ignites and leads chlorine gas through. The coal then reduces the alumina, and there results aluminium chloride and carbonic oxide, and perhaps also some phosgene, COCI2 ; the alumin- ium chloride is caught in the condenser and the gases escape. The sublimate is white, crystalline, melts about the tempera- ture of boiling water, easily attracts moisture, and evolves heat * Oversigt over det K. Danske Videnskabemes Selkabs Forhandlingar og dets Medlemmers Arbeider. May, 1824, to May, 1825, p. 15. fBerz. Jahresb. der Chemie, 1827, vi. 1 1 8. (246) REDUCTION OF ALUMINIUM COMPOUNDS. 247 when in contact with water. If it is mixed with a concentrated potassium amalgam and heated quickly, it is transformed ; there results potassium chloride, and the aluminium unites with the mercury. The new amalgam oxidizes in the air very quickly, and gives as residue when distilled in a vacuum a lump of metal resembling tin in color and lustre. In addition, Oerstedt found many remarkable properties of the metal and of the amalgam, but he holds them for a future communication after further in- vestigation." Oerstedt did not publish any other paper, and the next ad- vance in the science is credited to Wohler, whom all agree in naming as the true discoverer of the metal. Wohler' s Experiments (1827). In the following article from Poggendorff 's Annalen,* Wohler reviews the article of Oerstedt's given above, and continues as follows : — " I have repeated this experiment of Oerstedt, but achieved no very satisfactory result. By heating potassium amalgam with aluminium chloride and distilling the product, there re- mained behind a gray, melted mass of metal, but which, by raising the heat to redness, went ofif as green vapor and distilled as pure potassium. I have therefore looked around for another method or way of conducting the operation, but, unpleasant as it is to say it, the reduction of the aluminium fails each time. Since, however, Herr Oerstedt remarks at the end of his paper that he did not regard his investigations in aluminium as yet ended, and already several years have passed since then, it looks as if I had taken up one of those researches begun aus- piciously by another (but not finished by him), because it promised new and splendid results. I must remark, however, that Herr Oerstedt has indirectly by his silence encouraged me to try to attain to further results myself. Before I give the art how one can quite easily reduce the metal, I will say a few words about aluminium chloride and its production (see p. 152). * Pogg. Ann., 1827, ii. 147. 248 ALUMINIUM. " I based the method of reducing aluminium on the reaction of aluminium chloride on potassium, and on the property of the metal not to oxidize in water. I warmed in a glass retort a small piece of the aluminium salt with some potassium, and the retort was shattered with a strong explosion. I tried then to do it in a small platinum crucible, in which it succeeded very well. The reaction is always so violent that the cover must be weighted down, or it will be blown off; and at the moment of reduction, although the crucible be only feebly heated from outside, it suddenly glows inside, and the platinum is almost torn by the sudden shocks. In order to avoid any mixture of platinum with the reduced aluminium, I next made the reduction in a porcelain crucible, and succeeded then in the following manner : Put in the bottom of the crucible a piece of potassium free from carbon and oil, and cover this with an equal volume of pieces of aluminium chloride. Cover and heat over a spirit lamp, at first gently, that the crucible be not broken by the production of heat inside, and then heat stronger, at last to redness. Cool, and when fully cold put it into a glass of cold water. A gray powder separates out, which on nearer observation, especially in sunlight, is seen to consist of little flakes of metal. After it has separated, pour off the solution, filter, wash with cold water, and dry; this is the aluminium." In reality, this powder possessed no metallic properties, and moreover, it contained potassium and aluminium chloride, which gave it the property of decomposing water at 100°. To avoid the loss of aluminium chloride by volatilization at the high heat developed during the reaction, Liebig afterwards made its vapors pass slowly over some potassium placed in a long glass tube. This device of Liebig is nearly the arrange- ment which Wohler adopted later, in 1845, ^nd which gave him much better results. Wbklcr's Experiments ( 1 845 ) . The following is Wohler's second paper published in 1845 ■* * Liebig's Annalen, 53, 422. REDUCTION OF ALUMINIUM COMPOUNDS. 249 " On account of the violent incandescence with which the reduction of aluminium chloride by potassium is accompanied, this operation requires great precautions, and can be carried out only on a small scale. I took for the operation a platinum tube, in which I placed aluminium chloride, and near it some potassium in a platinum boat. I heated the tube gently at first, then to redness. But the reduction may also be done by put- ting potassium in a small crucible, which is placed inside a larger one, and the space between the two filled with aluminium chloride. A close cover is put over the whole, and it is heated. Equal volumes ot potassium and the aluminium salt are the best proportions to employ. After cooling, the tube or cruci- ble is put in a vessel of water. The metal is obtained as a gray metallic powder, but on closer observation one can see even with the naked eye small tin-white globules, some as large as pins' heads. Under the microscope magnifying two hundred diameters, the whole powder resolves itself into small globules, several of which may sometimes be seen sticking together, showing that the metal was melted at the moment of reduction. A beaten-out globule may be again melted to a sphere in a bead of borax or salt of phosphorus, but rapidly oxidizes dur- ing the operation, and if the heat is continued, disappears entirely, seeming either to reduce boric acid in the borax bead, or phosphoric acid in the salt of phosphorus bead. I did not succeed in melting together the pulverulent aluminium in a crucibe with borax, at a temperature which would have melted cast-iron, for the metal disappeared entirely and the borax be- came a black slag. It seems probable that aluminium, being lighter than molten borax, swims on it and burns. The white metallic globules had the color and lustre of tin. It is perfectly malleable and can be hammered out to the thinnest leaves. Its specific gravity, determined with two globules weighing 32 milligrammes, was 2.50, and with three hammered- out globules weighing 34 milligrammes, 2.67. On account of their lightness these figures can only be approximate. It is not magnetic, remains white in the air, decomposes water at 100°, not at 250 ALUMINIUM. usual temperatures, and dissolves completely in caustic potash (KOH). When heated in oxygen almost to melting, it is only superficially oxidized, but it burns like zinc in a blast-lamp flame." These results of Wohler's, especially the determination of specific gravity, were singularly accurate when we consider that he established them working with microscopic bits of the metal, It was just such work that established Wohler's fame as an investigator. However, we notice that his metal differed from aluminium as we know it in several important respects, in speaking of which Deville says: "All this time the metal obtained by Wohler was far from being pure ; it was very difficultly fusible, owing, without doubt, to the fact that it contained platinum taken from the vessel in which it had been prepared. It. is well known that these two metals com- bine very easily at a gentle heat. Moreover, it decomposed water at 100°, which must be attributed either to the presence of potassium or to aluminium chloride, with which the metal might have been impregnated : for aluminium in presence of aluminium chloride in effect decomposes water with evolution of hydrogen." After Wohler's paper in 1845, the next improvement is that introduced by Deville in 1854-55, and this is really the date at which aluminium, the metal, became known and its true proper- ties established. Deville s Experiments (1854). The results of this chemist's investigations and success in obtaining pure aluminium were first made public at the seance of the French Academy, August 14, 1854, and included men- tion of an electrolytic method of reduction (see Chap. XI.), as well as of the following on reduction by sodium.* " The following is the best method for obtaining aluminium chemically pure in the laboratory. Take a large glass tube about four centimeters in diameter, and put into it 200 or 300 * Ann. de Phys. et de Chim., xliii. 24. REDUCTION OF ALUMINIUM COMPOUNDS. 2$ I grammes of pure aluminium chloride free from iron, and isolate it between two stoppers of amianthus (fine, silky asbestos). Hydrogen, well dried and free from air, is brought in at one end of the tube. The aluminium chloride is heated in this cur- rent of gas by some lumps of charcoal in order to drive ofif hydrochloric acid or sulphides of chlorine or of silicon, with which it is always impregnated. Then there are introduced into the tube porcelain boats, as large as possible, each containing several grammes of sodium, which was previously rubbed quite dry between leaves of filter paper. The tube being full of hydrogen, the sodium is melted, the aluminium chloride is heated and distils, and decomposes in contact with the sodium with incandesence, the intensity of which can be moderated at pleasure. The operation is ended when all the sodium has dis- appeared, and when the sodium chloride formed has absorbed so much aluminium chloride as to be saturated with it. The aluminium which has been formed is held in the double chloride of sodium and aluminium, AlClg.NaCl, a compound very fusible and very volatile. The boats are then taken from the glass tube, and their entire contents put in boats made of retort car- bon, which have been previously heated in dry chlorine in order to remove all siliceous and ferruginous matter. These are then introduced into a large porcelain tube, furnished with a pro- longation and traversed by a current of hydrogen, dry and free from air. This tube being then heated to bright redness, the aluminium-sodium chloride distils without decomposition and condenses in the prolongation. There is found in the boats, after the operation, all the aluminium which had been reduced, collected in at most one or two small buttons. The boats when taken from the tube should be nearly free from aluminium- sodium chloride, and also from sodium chloride. The buttons of aluminium are united in a small earthenware crucible, which is heated as gently as possible, just sufificient to melt the metal. The latter is pressed together and skimmed clean by a small rod or tube of clay. The metal thus collected may be very suitably cast in an ingot mould." 252 ALUMINIUM. The later precautions added to the above given process were principally directed towards avoiding the attacking of the cruci- ble, which always takes place when the metal is melted with a flux, and the aluminium thereby made more or less siliceous. The year following the publication of these results, this labora- tory method was carried out on a large scale at the chemical works at Javel. Deville's Methods (1855). The methods about to be given are those which were devised in Deville's laboratory at the Ecole Normale, during the winter of 1854-55, and applied on a large scale at Javel, during the spring of 1855 (March-July). The Emperor Napoleon III. defrayed the expenses of this installation. Descriptions of the methods used for producing alumina, aluminium chloride and sodium at Javel can be found under their respective headings (pp. 134, 153, 180), We here confine our description to the mode of reducing the aluminium chloride by sodium, and the remarks incident thereto. The process has at present only an historic interest, as it was soon modified in its details so as to be almost entirely changed. The following is Deville's description : — " Perfectly pure aluminium. — To obtain aluminium perfectly pure it is necessary to employ materials of absolute purity, to reduce the metal in presence of a completely volatile flux, and finally never to heat, especially with a flux, in a siliceous vessel to a high temperature. " Pure materials. — The necessity of using absolutely pure materials is easy to understand ; all the metallic impurities are concentrated in the aluminium, and unfortunately I know no absolute method of purifying the metal. Thus, suppose we take an alum containing o.i per cent, of iron and 11 per cent, of alumina; the alumina derived from it will contain i per cent, of iron, and supposing the alumina to give up all the alu- minium in it, the metal will be contaminated with 2 per cent, of iron. REDUCTION OF ALUMINIUM COMPOUNDS. 253 '^Influence of flux or slag. — The flux, or the product of the reaction of the sodium on the aluminous material, ought to be volatile, that one may separate the aluminium by heat from the material with which it has been in contact, and with which it remains obstinately impregnated because of its small specific gravity. " Influence of the vessel. — The siliceous vessels in which aluminium is received or melted give it necessarily a large quantity of silicon, a very injurious impurity. Silicon cannot be separated from aluminium by any means, and the siliceous aluminium seems to have a greater tendency to take up more silicon than pure aluminium, so that after a small number of remeltings in siliceous vessels the metal becomes so impure as to be almost infusible. In order to avoid the dangers pointed out above, Deville re- commended following scrupulously the following details in order to get pure aluminium. " Reduction of solid sodium. — The crude aluminium chloride placed in the cyHnder A (Fig. 23), is vaporized by the fire and ,-JL, Fig. 24. r 1 I to.»»iaa Y^s;^ teMaa "T passes through the tube to the cylinder B, containing 60 to 80 kilos of iron nails heated to a dull-red heat. The iron retains as relatively fixed ferrous chloride, the ferric chloride and hydrochloric acid which contaminate the aluminium chloride, and likewise transforms any sulphur dichloride (SCl^) in it into ferrous chloride and sulphide of iron. The vapors on passing out of B through the tube, which is kept at about 300°, deposit 254 ALUMINIUM. spangles of ferrous chloride, which is without sensible tension at that temperature. The vapors then enter D, a cast-iron cylinder in which are three cast-iron boats each containing 500 grms. of sodium. It is sufficient to heat this cylinder barely to a dull-red heat in its lower part, for the reaction once com- menced disengages enough heat to complete itself, and it is often necessary to take awav all the fire from it. There is at first produced in the first boat some aluminium and some sod- ium chloride, which latter combines with the excess of alumin- ium chloride to form the volatile aluminium-sodium chloride, AlClj.NaCl. These vapors of double chloride condense on the second boat and are decomposed by the sodium into alumin- ium and sodium chloride. A similar reaction takes place in the third boat when all the sodium of the second has disap- peared. When on raising the cover it is seen that the sodium of the last boat is entirely transformed into a lumpy black material, and that the reactions are over, the boats are taken out, immediately replaced by others, and are al- lowed to cool covered by empty boats. In this first opera- tion the reaction is rarely complete, for the sodium is protected by the layer of sodium chloride formed at its ex- pense. To make this disappear, the contents of the boats are put into cast-iron pots or earthen crucibles, which are heated until the aluminium chloride begins to volatilize, when the so- dium will be entirely absorbed and the aluminium finally re- mains in contact with a large excess of its chloride, which is indispensable for the success of the operation. Then the pots or crucibles are cooled, and there is taken from the upper part of their contents a layer of sodium chloride almost pure, while underneath are found globules of aluminium which are sepa- rated from the residue by washing with water. Unfortunately the water in dissolving the aluminium chloride of the flux exer- cises on the metal a very rapid destructive action, and only the globules larger than the head of a pin are saved from this washing. These are gathered together, dried, melted in an earthen crucible, and pressed together with a clay rod. REDUCTION OF ALUMINIUM COMPOUNDS. 255 The button is then cast in an ingot mould. It is important in this operation to employ only well-purified sodium, and not to melt the aluminium if it still contains any sodium, for in this case the metal takes fire and burns as long as any of the alka- line metal remains in it. In such a case it is necessary to re- melt in presence of a little aluminium-sodium chloride. " Such is the detestable process by means of which were made the ingots of aluminium sent to the Exhibition (1855). To complete my dissatisfaction at the processs, pressed by time and ignorant of the action of copper on aluminium, I employed in almost all my experiments reaction cylinders and boats of cop- per, so that the aluminium I took from them contained such quantities of this metal as to form a veritable alloy. Moreover, it had lost almost all ductility and malleability, had a disagreeable gray tint, and finally at the end of two months it tarnished by becoming covered with a black layer of oxide or sulphide of copper, which could only be removed by dipping in nitric acid. But, singular to relate, an ingot of virgin silver which had been put alongside the aluminium that the public might note easily the difference in color and weight of the two metals, was blackened still worse than the impure aluminium. Only one of the bars exhibited, which contained no copper, remained un- altered from the day of its manufacture till now (1859). It was some of this cupreous aluminium that I sent to M. Regnault, who had asked me for some in order to determine its specific heat. I had cautioned him at the time of the number and nature of the impurities which it might contain, and the analysis of M. Salvetat, which is cited in the memoir of Regnault, accords with the mean composition of the specimens that I had produced and analyzed at that time (see p. 54, Analysis i). It is to be regretted that I gave such impure material to serve for determinations of such splendid precision. I was persuaded to do so only by the entreaties of M. Regnault, who could not wait until I prepared him better. It is also this cupreous aluminium which M. Hulot has called ' hard aluminium,' in a note on the physical properties of this metal 256 ALUMINIUM. which he addressed to the Academy. Hulot has remarked that this impure metal, which is crystalline in structure, after having been compressed between the dies of the coining press may lose its crystalline structure, to which it owes its brittle- ness, and become very malleable. It possesses then such strength that it works well in the rolls of a steel rolling mill. Further, this 'hard aluminium' becomes quite unalterable when it has thus lost its texture. "Reduction by sodium vapor. — This process, which I have not perfected, is very easy to operate, and gave me very pure metal at the first attempt. I operate as follows : I fill a mercury bot- tle with a mixture of chalk, carbon, and carbonate of soda, in the proportions best for generating sodium. An iron tube about ten centimetres long is screwed to the bottle, and the whole placed in a wind furnace, so that the bottle is heated to red-white and the tube is red to its end. The end of the tube is then introduced into a hole made in a large earthen crucible about one-fourth way from the bottom, so that the end of the tube just reaches the inside surface of the crucible. The car- bonic oxide (CO) disengaged burns in the bottom of the cru- cible, heating and drying it ; afterwards the sodium flame appears, and then pieces of aluminium chloride are thrown into the crucible from time to time. The salt volatilizes and de- composes before this sort of tuyere, from which issues the reducing vapor. More aluminium salt is added when the vapors coming from the crucible cease to be acid, and when the flame of sodium burning in the atmosphere of aluminium chloride loses its brightness. When the operation is finished, the crucible is broken and there is taken from the walls below the entrance of the tube a saline mass composed of sodium chloride, a considerable quantity of globules of aluminium, and some sodium carbonate, which latter is in larger quantity the slower the operation was performed. The globules are de- tached by plunging the saline mass into water, when it be- comes necessary to notice the reaction of the water on litmus. If the water becomes acid, it is renewed often ; if alkaline, the REDUCTION OF ALUMINIUM COMPOUNDS. 257 mass, impregnated with metal, must be digested in nitric acid, diluted with three or four volumes of water, and so the metal is left intact. The globules are reunited by melting with the precautions before given." Deville's Process (1859). The process then in use at Nanterre was based on the use of aluminium-sodium chloride, which was reduced by sodium, with cryolite or fluorspar as a flux. The methods of preparing each of these materials were carefully studied out at the chem- ical works of La Glaciere, where, from April, 1856, to April, 1857, the manufacture of aluminium was carried on by a com- pany formed by Deville and a few friends, and from thence proceeded the actual system which was established at Nanterre under the direction of M. Paul Morin when the works at La Glaciere were closed. The methods of preparation of alumina, aluminium-sodium chloride and sodium used at Nanterre are placed under their respective, headings (pp. 137, 154, 190). In the first year that the works at Nanterre were in opera- tion there were made : Aluminium-sodium chloride 10,000 kilos. Sodium 2,000 " Aluminium 600 " The metal prepared improved constantly in quality, M. Morin profiting continually by his experience and improving the practical details constantly, so that the aluminium averaged, in 1859, gj per cent. pure. (See Analysis 9, p. 54.) As to the rationale of the process used, aluminium chloride was replaced by aluminium-sodium chloride because the latter is less deliquescent and less difficult of preservation ; but the. small amount of moisture absorbed by the double chloride is held very energetically, at a high temperature giving rise to some alumina, which encloses the globules of metal with a thin coating, and so hinders their easy reunion to a button. Deville remarked that the presence of fluorides facilitated the reunion 17 258 ALUMINIUM. of these globules, which fact he attributed to their dissolving the thin coat of alumina ; so that the employment of a fluoride as a flux became necessary to overcome the effect produced primarily by the aluminium-sodium chloride holding moisture so energetically. Deville gives the following account of the development of these improvements : "The facility with which aluminium unites in fluorides is due without doubt to the prop- erty which these possess of dissolving the alumina on the sur- face of the globules at the moment of their formation, and which the sodium is unable to reduce. I had experienced great difificulty by obtaining small quantities of metal poorly united, when I reduced the aluminium-sodium chloride by sodium ; M. Rammelsberg, who often made the same attempts, tells me he has had a Hke experience. But I am assured by a scrupu- lous analysis that the quantity of metal reduced by the sodium is exactly that which theory indicates, although after many operations there is found only a gray powder, resolving itself under the microscope into a multitude of small globules. The fact is simply that aluminium-sodium chloride is a very poor flux for aluminium. MM. Morin, Debray, and myself have undertaken to correct this bad effect by the introduction of a solvent for the alumina into the saline slag which accompanies the aluminium at the moment of its formation. At first, we found it an improvement to condense the vapors of aluminium chloride, previously purified by iron, directly in sodium chloride, placed for this purpose in a crucible and kept at a red heat. We produced in this way, from highly colored material, a double chloride very white and free from moisture, and furnishing on reduction a metal of fine appearance. We then introduced fluorspar (CaF^) into the composition of the mixture to be reduced, and we obtained good results with the following pro- portions : Aluminium-sodium chloride 400 grammes. Sodium chloride 200 " Calcium fluoride 200 " Sodium 75 to 80 " REDUCTION OF ALUMINIUM COMPOUNDS. 259 " The double chloride ought to be melted and heated almost to low red heat at the moment it is employed, the sodium chloride calcined and at a red heat or melted, and the fluorspar pulverized and well dried. The double chldride, sodium chlor- ide and calcium fluoride are mixed and alternated in layers in the crucible with sodium. The top layer is of the mixture, and the cover is sodium chloride. Heat gently, at first, until the reaction ends, and then to a heat about sufficient to melt silver. The crucible, or at least that part of it which contains the mix- ture, ought to be of a uniform red tint, and the material per- fectly liquid. It is stirred a long time and cast on a well dried, chalked plate. There flows out first a very limpid liquid, col- orless and very fluid ; then a gray material, a little more pasty, which contains aluminium in little grains, and is set aside ; and finally a button with small, metallic masses which of them- selves ought to weigh 20 grms. if the operation has succeeded well. On pulverizing and sieving the gray slag, 5 or 6 grms. of small globules are obtained, which may be pressed together by an earthen rod in an ordinary crucible heated to redness. The globules are thus reunited, and when a sufficient quantity is collected the metal is cast into ingots. In a well-conducted operation, 75 grms. of sodium ought to give a button of 20 grms. and S grms. in grains, making a return of one part alu- minium from three of sodium. Theory indicates one to two and a half, or 30 grms. of aluminium from 75 of sodium. But all the efforts which have been made to recover from the inso- luble slag the 4 or 5 grms. of metal not united, but easily vis- ible with a glass, have been so far unsuccessful. There is, without doubt, a knack, a particular manipulation, on which de- pends the success of an operation which would render the theoretical amount of metal, but we lack it yet. These opera- tions take place, in general, with more facility on a large scale, so that we may consider fluorspar as being suitable for serving in the manufacture of aluminium in crucibles. We employed very pure fluorspar, and our metal was quite exempt from silicon. It is true that we took a precaution which is necessary 260 ALUMINIUM. to adopt in operations of this kind ; we plastered our crucibles inside with a layer of aluminous paste, the composition of which has been given in 'Ann. de Chim. et de Phys.' xlvi. 195. This paste is made of calcined alumina and an aluminate of lime, the latter obtained by heating together equal parts of chalk and alumina to a high heat. By taking about four parts calcined alumina and one of aluminate of lime well pulverized and sieved, moistening with a little water, there is obtained a paste with which the inside of an earthen crucible is quickly and easily coated. The paste is spread evenly with a porcelain spatula, and compressed strongly until its surface has become well polished. It is allowed to dry, and then heated to bright redness to season the coating, which does not melt, and pro- tects the crucible completely against the action of the alumin- ium and fluorspar. A crucible will serve several times in suc- cession, provided that the new material is put in as soon as the previous charge is cast. The advantages of doing this are that the mixture and the sodium are put into a crucible al- ready heated up, and so lose less by volatilization because the heating is done more quickly, and the crucible is drier than if a new one had been used or than if it had been let cool. A new crucible should be heated to at least 300° or 400° before being used. The saline slag contains a large quantity of cal- cium chloride, which can be washed away by water, and an in- soluble material from which aluminium fluoride can be volatil- ized. " Yet the operation just described, which was a great im- provement on previous ones, requires many precautions and a certain skill of manipulation to succeed every time. But nothing is more easy or simple than to substitute cryolite for the fluorspar. Then the operation is much easier. The amount of metal produced is not much larger, although the button often weighs 22 grammes, yet if cryolite can only be ob- tained in abundance in a continuous supply, the process which I will describe will become most economical. The charge is made up as before, except introducing cryolite for fluorspar. REDUCTION OF ALUMINIUM COMPOUNDS. 26 1 In one of our operations we obtained, with -j^ grms. of sodium, a button weighing 22 grms. and 4 grms. in globules, giving a yield of one part aluminium to two and eight-tenths parts sodium, which is very near to that indicated by theory. The metal obtained was of excellent quality. However, it con- tained a little iron coming from the aluminium chloride, which had not been purified perfectly. But iron does not injure the properties of the metal as copper does ; and, save a little bluish coloration, it does not alter its appearance or its resistance to physical and chemical agencies. " After these attempts we tried performing the reduction sim- ply on the bed of a reverberatory furnace, relying on the imme- diate reaction of sodium on the double chloride to use up these materials before they could be perceptibly wasted by the fur- nace gases. This condition was realized in practice with unlooked-for success. The reduction is now made on a some- what considerable scale at the Nanterre works, and never, since commencing to operate in this way, has a reduction failed, the results obtained being always uniform. The furnace now used has all the relative dimensions of a soda furnace. In fact, almost the temperature of an ordinary soda furnace is required that the operation may succeed perfectly. The absolute dimen- sions of the furnace, however, may vary with the quantity of alu- minium to be made in one operation, and are not limited. With a bed of one square metre surface, 6 to 10 kilos of aluminium can be reduced at once ; and since each operation lasts about four hours, and the furnace may be recharged immediately after emptying it of the materials just treated, it is seen that, with so small a bed, 60 to lOO kilos of aluminium can be made in twenty-four hours without any difficulty. In this respect, I think the industrial problem perfectly solved. The proportions which we employed at first were — Aluminium-sodium chloride (crushed) 10 parts. Fluorspar 5 " Sodium (in ingots) 2 " " As aluminium is still very dear, it is necessary to direct 262 ALUMINIUM. great attention to the return from the materials used, and on this point there is yet much progress to be made. We ascer- tained many times that the return was always a little better, and the reunion of the metal to a single ingot a little easier, when cryolite was substituted for fluorspar, the price of the former, after having been high, being now lowered to 350 francs per tonne (about $75 per long ton). For this reason we can now use cryolite instead of fluorspar, and in the same proportions. We can also recover alumina from this cryolite by treating the slags (see p. 148). The double chloride and pulverized cryo- lite are now mixed with the sodium in small ingots, and the mixture thrown on to the bed of the heated-up furnace. The dampers are then shut, to prevent as much as possible access of air. Very soon a lively reaction begins, with the production of such heat that the brick sides of the furnace, as well as the materials on the hearth, are made bright red-hot. At this heat the mixture is almost completely fused. Then it is necessary to open the damper and direct the flame on the bed in such manner as to heat the bath equally all over and unite the re- duced aluminium. When the operation is considered ended, a casting is made by an opening in the back of the furnace and the slag is received in cast-iron pots. At the end of the cast the aluminium arrives in a single jet, which unites into a single lump at the bottom of the still-liquid slag. The gray slag flow- ing out last should be pulverized and sieved, to extract the divided globules of aluminium, 200 to 300 grammes of which can sometimes be extracted from one kilo of gray slag. The pulverization of the slag is in all cases indispensable in its sub- sequent treatment for extracting its alumina. The slag is of two kinds, one fluid and light, which covered the bath, and is rich in sodium chloride ; the other less fusible and pasty, gray in color, which is more dense and lies in contact with the alu- minium. The coloring material producing the grayness is car- bon, coming either from the sodium or from the oil which im- pregnated it, or finally from the vapor of the oil. I attribute the slight pastiness of this slag to a little alumina dissolved by the fluorides. This slag contains about: REDUCTION OF ALUMINIUM COMPOUNDS. 263 Sodium chloride 60 parts. Aluminium fluoride 40 " and on washing it the former dissolves while the latter remains, mixed with a little cryolite or alumina. This is the alumina which had been dissolved or retained in the bath of fluoride. It will be remarked that the bath of slag contains no other fluoride than aluminium fluoride, which does not attack earthen crucibles or siliceous materials in general except at a very high temperature. It is for this reason that the hearth and other parts of the furnace resist easily a fluoride slag containing only alu- minium fluoride, which has not the property of combining with silicon fluoride at the expense of the silica of the bricks — as sodium fluoride does in like circumstances. In our operations, cryolite is used only as a flux. In the process of reduction based on cryolite alone, the sodium fluoride resulting is, on the contrary, very dangerous to crucibles, and it is due to that fact especially that the aluminium absorbs a large quantity of silicon, which always happens with this method. In fact, it is well known that metallic silicon can be prepared in this way by prolonging the operation a little." Deville closes his account of the aluminium industry in 1859 with these words : " Many things yet remain to us to do, and we can scarcely say now that we know the true qualities of the substances we employ. But the matter is so new, is harassed with so many difiSculties even after all that has been done, that our young enterprise may hope everything from the future when it shall have acquired experience. I ought to say, however, that the aluminium industry is now at such a point that if the uses of the metal are rapidly extended it may change its aspect with great rapidity. One may ask to-day how much a kilo of iron would cost if a works made only 60 to 100 kilos of it a month, if large apparatus were excluded from this industry, and iron obtained by laboratory processes which would permit it to become useful only by tedious after-treatment. Such will not be the case with aluminium, at least with the processes just de- scribed. In fact in all I undertook, either alone or with my 264 ALUMINIUM. friends, I have always been guided by this thought — that we ought to adopt only such apparatus as is susceptible of being immediately enlarged, and to use only materials almost as com- mon as clay itself for the source of the aluminium." The Deville Process (1882). The process just described reached a fair degree of perfec- tion at Nanterre, under the direction of M. Paul Morin. After- wards, some of the chemical operations incidental to the process were carried on at the works of the Chemical Manufac- turing Company of Alais and Carmargue, at Salindres (Gard), owned by H. Merle & Co. At a later date the whole manufac- ture was removed to this place, while the Societe Anonyme de 1' Aluminium, at Nanterre, worked up the metal, and placed it on the market. The Salindres works, about 1880, went under the management of A. R. Pechiney & Co., and under the per- sonal attention of M. Pechiney, the Deville process reached its perfection. The following account is taken mostly from M. Margottet's article on aluminium in Fremy's Encyclopedic Chimique. An outline of the process, as it was prepared, may very appropriately be given at this place, although detailed descrip- tions of the preliminary processes for preparing the materials for reduction are given under the appropriate headings (see pp. 137, 154, 190). The primary material to furnish the aluminium is bauxite. To obtain the metal it is necessary to proceed successively through the following operations: — I. Preparation of the aluminate of soda, and solution of this salt to separate it from the ferric oxide contained in the bauxite. II. Precipitation of hydrated alumina from the aluminate of soda by a current of carbon dioxide ; washing the precipitate. III. Preparation of a mixture of alumina, carbon, and salt, drying it, and then treating with gaseous chlorine to obtain the double chloride of aluminium and sodium. REDUCTION OF ALUMINIUM COMPOUNDS. 265 IV. Lastly, treatment of this chloride by sodium to obtain aluminium. The principal chemical reactions on which this process rests are the following: — Formation of aluminate of soda by calcining bauxite with sodium carbonate — (AlFe) A.2H,0 + 3Na,C03=-Al,03-3Na,0 + Fe.Oa + 2H,0 + 3CO,. Formation of alumina by precipitating the aluminate of soda with a current of carbon dioxide — Al,03-3Na,0 + 3CO, + 3H,0 = Al.Os.sH.O + 3Na,C03. Formation of aluminium-sodium chloride by the action of chlorine on a mixture of alumina, carbon, and sodium chloride — AI2O3 + 3C + 2NaCl + 6C1 = 2 (AlCla.NaCl) + 3CO. Reduction of this double chloride by sodium — AlCIs.NaCl + 3Na = Al + 4NaCl. As observed before, we will here consider only the last oper- ation. The advances made since 1859 are mostly in matters of detail, which every one knows are generally the most import- ant part of a process ; and so, although a few of the details may be repeated, yet we think it best not to break the contin- uity of this description by excising those few sentences which are nearly identical in the two accounts. The difiSculty of this operation, at least from an industrial point of view, is to get a slag fusible enough and light enough to let the reduced metal easily sink through it and unite. This result has been reached by using cryolite. This material iorms with the sodium chloride resulting from the reaction a very fusible slag, in the midst of which the aluminium collects well, and falls to the bottom. In one operation the charge is now composed of — 266 ALUMINIUM. 100 kilos Aluminium-sodium chloride. 45 " Cryolite. 35 " Sodium. The double chloride and cryolite are pulverized, the sodium^ cut into small pieces a little larger than the thumb, is divided into three equal parts, each part being put into a sheet-iron basket. The mixture of double chloride and cryolite, being pulverized, is divided into four equal parts, three of these are respectively put in each basket with the sodium, the fourth being placed in a basket by itself. The reduction furnace (see Fig. 25. r a. Fig. 25) is a little furnace of refractory brick, with an inclined hearth and a vaulted roof. This furnace is strongly braced by iron tie-rods, because of the concussions caused by the reac- tion. The flame may at any given moment be directed into a. flue outside of the hearth. At the back part of the furnace,, that is to say, on that side towards which the bed slopes, is a little brick wah which is built up for each reduction and is. taken away in operating the running out of the metal and slag> A gutter of cast-iron is placed immediately in front of the wall to facilitate running out the materials. All this side of the fur- nace ought to be opened or closed at pleasure by means of a damper. Lastly, there is an opening for charging in the roof, closed by a lid. At the time of an operation the furnace should be heated to low redness, then are introduced in rapid REDUCTION OF ALUMINIUM COMPOUNDS. 267 succession the contents of the three baskets containing sodium, etc., and lastly the fourth containing only double chloride and no sodium. Then all the openings of the furnace are closed, and a very vivid reaction accompanied by dull concussions im- mediately takes place. At the end of fifteen minutes, the ac- tion subsides, the dampers are opened and the heat continued, meanwhile stirring the mass from time to time with an iron poker. At the end of three hours the reduction is ended, and the metal collects at the bottom of the liquid bath. Then the running out is proceeded with in three phases : First — Running off the upper part of the bath, which consists of a fluid material completely free from reduced aluminium and constituting the white slag. To run this out a brick is taken away from the upper course of the little wall which terminates the hearth. These slags are received in an iron wagon. Second — Running out the aluminium. This is done by opening a small orifice left in the bottom of the brick wall, which was temporarily plugged up. The liquid metal is received in a cast-iron melt- ing pot, the bottom of which has been previously heated to redness. The aluminium is immediately cast in a series of small rectangular cast-iron moulds. Third — Running out of the rest of the bath, which constitutes the gray slags. These were, like the white slags, formed by the sodium chloride and cryolite, but they contain, in addition, isolated globules of alu- minium. To run these out, all the bricks of the little wall are taken away.. , This slag is received in the same melting pot into which the aluminium was run, the latter having been already moulded. Here it cools gradually, and after cooling there are always found at the bottom of the pot several grains of metal. In a good operation there are taken from one casting 10.5 kilos of aluminium, which is sold directly as commercial metal. The following data as to the expense of this process may be very appropriately inserted here, giving the cost at Salindres in 1873, in which year 3600 kilos are said to have been made. * Manufacture of one kilo of aluminium. * A. Wurtz, Wagner's Jahresb., 1874, vol. xxi. 268 ALUMINIUM. Sodium 3.44 kilos @ 11.32 fr. per kilo = 38 fr. 90 cent. Aluminium-sodium chloride. . . . 10.04 " 2.48 " " = 24 " 90 " Cryolite 3.87 " 61.0 " 100 kilos ^ 2 " 36 " Coal 29.17 " 1.40 " " = o " 41 " Wages I " 80 " Costs o " 88 " Total 69 " 25 " This must be increased ten per cent, for losses and other ex- penses, making the cost of aluminium 80 fr. per kilo, and it is sold for 100. ($9.00 per lb.) According to a statement in the ' Bull, de la Soc. de I'lndustrie Minerale,' ii. 451, made in 1882, Salindres was then the only place in which aluminium was being manufactured. The Deville process was finally driven out of the market, and the manufacture at Salindres suspended, in 1890. Niewerth's Process (1883). This method can be regarded as little more than a suggestion, since it follows exactly the lines of some of Deville's earlier ex- periments. Although theoretically very advantageous, yet in practice it has probably been found far inferior in point of yield of metal and expense to the ordinary sodium processes. The patent is taken out in the United States and other countries in the name of H. Niewerth, of Hanover, and is thus summarized : *A compound of aluminium, with chlorine or fluorine, is brought by any means into the form of vapor, and conducted, strongly heated, into contact with a mixture of 62 parts sodium carbonate, 28 coal, and 10 chalk, which is also in a highly heated condition. This mixture disengages sodium, which reduces the gaseous chloride or fluoride of aluminium, the nascent sodium being the reducing agent. In place of the above mixture other suitable mixtures which generate sodium may be employed, or mixtures may also advantageously be used from which potassium is generated. * Sci. Am. Supple., Nov. 17, 1883. REDUCTION OF ALUMINIUM COMPOUNDS. 269 Gadsden's Patent (1883). H. A. Gadsden, of London, and E. Foote,* of New York, were granted a patent based on the principle of heating in a retort sodium carbonate and carbonaceous matter, or any suit- able mixture for generating sodium, and conducting the vapor of sodium produced into another retort, lined with carbon, in which aluminium chloride, or aluminium-sodium chloride or cryolite, has been placed and heated. The second English pat- ent claims to heat a mixture which will generate sodium in one retort, and pass chlorine over a mixture of carbon and alum- ina, thus generating aluminium chloride, in another retort, and then mixing the two vapors in a third retort or reaction chamber. Friskmuth's Process (1884). This was patented in the United States in 1884 (U. S. Pat. 308,152, Nov. 1884). In what the originality of the process consists, in view of Deville's publications and even in view of the processes just mentioned, we cannot see. Col. Frishmuth himself admitted, in 1887, having abandoned the sodium process, as the difficulties of the method did not permit its competing with the more roundabout but more easily-conducted operation with solid sodium. A simple transcript of the claims in his patent will give a sufficiently extended idea of the reactions proposed to be used. 1. The simultaneous generation of sodium vapor and a vola- tile compound of aluminium in two separate vessels or retorts, and mingling the vapors thus obtained in a nascent ( ! ) state in a third vessel, wherein they react on each other. 2. The sodium vapor is produced from a mixture of a sodium compound and carbon, or some other reducing agent; and the aluminous vapor from aluminous material. 3. The simultaneous generation of sodium vapor and vapor of aluminium chloride or aluminium fluoride; or of sodium vapor and aluminium-sodium chloride. * English patents 1995 and 493° (1883); German patent 27,572 (1884). 2 70 ALUMINIUM. 4. Converting the aluminous material to a vapor by heating it in a retort with sodium chloride, and subjecting it at the same time to chlorine gas ; mingling the vapor of aluminium- sodium chloride thus obtained with vapor simultaneously gen- erated from sodium carbonate and carbon. H. von Grousillier' s Improvement (1885)- This suggestion as to the way of performing the reduction by sodium is the subject of the English patent 7858, June 29, 18B5. Dr. Fischer remarks on it, in " Wagner's Jahresbericht" for 1885, that "it is apparently wholly worked out at the writing-table," The patentee. Hector von Grousillier, Springe, Hanover, thus describes his invention : " In order to avoid the difficulties ordinarily met with in the use of aluminium-sodium chloride to obtain aluminium, I raise the volatilizing point of aluminium chloride by performing its reduction, either chemically or electrolytically, under pressure in a strong hermetically-closed vessel, lined with clay or mag- nesia, and provided with a safety valve." The Deville-Castner Process (1886). This last development of the old Deville process was ope- rated by the Aluminium Company, Limited, at their large new works at Oldbury, near Birmingham, England. The plant covered nearly five acres of ground, and adjoined Chance Bros.' large chemical works, from which the hydrochloric acid used was obtained and the waste soda-liquors returned, by means of large pipes connecting the two plants. The company was thus in position to obtain acid and dispose of its by-products to very good advantage. The principle on which the process was worked is similar to its predecessor, in being the reduction of aluminium-sodium chloride by sodium, but it improves on the other in the cheaper production of both these materials. For instance, the alumina used is obtained and converted into double chloride by Mr. Webster's processes, by which the cost of this salt is not over 3^. per lb. (see p. 164), as against i2d.. REDUCTION OF ALUMINIUM COMPOUNDS. 2/1 the cost at Salindres ; further, by Mr. Castner's sodium process it is acknowledged that the sodium cost only about ^d. per lb., as against 48^^., or $1, as formerly. Since 10 lbs. of the chlo- ride and 3 lbs. of sodium are required to produce i lb. of alu- minium, the average saving in these two items, over the old process, is somewhere about 75 per cent. The works contain a sodium building, in which are four large sodium furnaces, each capable of producing over 500 lbs. of that metal in twenty-four hours ; the sodium is also remelted and stored in the same building (see p. 215). The double chloride furnaces are in a building 250 feet by 50 feet wide, there being 12 furnaces, each containing 5 retorts. The total output of double chloride is an average of 5000 lbs. per day. (See. p. 162). Connected with this building is a chlorine plant of the largest size, capable of supplying about a ton and a half of chlorine a day. In a separate building are two reverberatory furnaces, in which the final reduction takes place and the alu- minium is produced. Besides these there are a rolling mill, wire mill, and foundry on the grounds. From the quantity of sodium and double chloride produced, we can see that the works can produce about 500 lbs. of aluminium a day, or 150,000 lbs. a year, with some sodium left over for sale or other purposes. The mode of conducting the reduction is not very different from that practiced at Salindres. There are two regenerative reverberatory furnaces used, one about twice as large as the other. The larger furnace has a bed about six feet square, slop- ing towards the front of the furnace, through which are several openings at different heights. The charge for this furnace con- sists of 1200 lbs. of double chloride, 350 lbs. of sodium, and 600 lbs. of cryolite for a flux. The chloride is in small pieces, the cryolite is in powder, and the sodium is cut into thin slices by a machine. These ingredients are put into a revolving wooden drum placed on a staging over the furnace, and are there thoroughly mixed. The drum is then opened and turned, when the contents fall into a small wagon beneath. 272 ALUMINIUM. The furnace having been raised to the required temperature, all the dampers are shut and the car is moved on a track immedi- ately over a. large hopper placed in the roof of the furnace. The hopper being opened, the charge is dumped in and drops on to the centre of the hearth. The reaction is immediate, and the whole charge becomes liquid in a very short time. After a few minutes, heating gas is again turned on, and the furnace kept moderately hot for two or three hours. The reac- tion has been AlCla.NaCl + 3Na = Al + 4NaCl and the aluminium gathers under the bath of cryolite and sod- ium chloride. One of the lower tap-holes is then opened with a bar, and the aluminium run out into moulds. When the metal has all run out it is followed by slag, which flows into iron wagons. The openings are then plugged up and the fur- nace is ready for another charge. The charge given produces usually 115 to 120 lbs. of aluminium, the whole operation last- ing about 4 hours. The large furnace could thus produce 840- lbs. in 24 hours, and the smaller one half that quantity. The first portion of metal running out is the purest, the latter por- tions, and especially that entangled in the slag on the hearth, and which has to be scraped out, containing more foreign sub- stances. This impure metal is about one-fourth of all the aluminium in the charge. The purity of the metal run out depends directly on the purity of the chloride used. If the double chloride contains 0.2 per cent, of iron, the metal produced will very probably contain all of it, or 2 per cent. Using the double chloride purified by Mr. Castner's new method (see p. 163), by which the content of iron is reduced to 0.05 per cent, or less, alu- minium can be made containing less than 0.5 per cent, of iron and from 99 to 99.5 per cent, of aluminium. Professor Roscoe exhibited at one of his lectures a mass of metal weighing 116' lbs., being one single running from the furnace, and which con- tained only 0.3 per cent, of silicon and 0.5 per cent. iron. In. REDUCTION OF ALUMINIUM COMPOUNDS. 273 practice, the metal from 8 or 10 runnings is melted down to- gether to make a uniform quality. Taking the figures given, it appears that the metal run out represents 70 per cent, of the aluminium in the charge, and 80 percent, of the weight which the sodium put in should reduce; but since an indeterminate weight is sifted and picked from the slag, it is probable that the utilization of the materials is more perfect than the above percentages. However, this seems to be the part of the old Deville process least improved upon in these new works, for there seems to be plenty of room for im- provement in perfecting the utilization of materials, especially in regard to loss of sodium by volatilization, which undoubt- edly takes place and which can possibly be altogether pre- vented. The above description, written in 1890, was followed only one year later by the closing of this splendid works. The very lowest point to which the Deville-Castner process could reduce the cost of producing aluminium was between 4 and S shillings per pound ; and when the metal was put on the market by users of the electrolytic process at $1.50 per pound, in 1891, there was nothing left for the sodium process except to give up the business. The company, however, continues to run the works, making and selling large quantities of sodium. i8 CHAPTER X. REDUCTION OF ALUMINIUM COMPOUNDS BY MEANS OF POTASSIUM OR SODIUM {Continued). II. Methods based on the reduction of cryolite. These can be most conveniently presented in chronological order. Rose's Experiments (1855). We will here give H. Rose's entire paper, as an account of this eminent chemist's investigations written out by himself with great detail, describing failures as well as successes, cannot but be of value to all interested in the production of aluminium:* " Since the discovery of aluminium by Wohler, Deville has recently devised the means of procuring the metal in large, solid masses, in which condition it exhibits properties with which we were previously unacquainted in its more pulverulent form as procured by Wohler's method. While, for instance, in the lat- ter state it burns vividly to white earthy alumina on being ig- nited, the fused globules may be heated to redness without perceptibly oxidizing. These differences may be ascribed to the greater amount of division on the one hand and of density on the other. According to Deville, however, Wohler's metal contains platinum, by which he explains its difficulty of fusion, although it affords white alumina by combustion. Upon the publication of Deville's researches, I also tried to produce aluminium by the decomposition of aluminium-sodium chloride by means of sodium. I did not, however, obtain satisfactory * Pogg. Annalen, Sept., 1855. (274) REDUCTION OF ALUMINIUM COMPOUNDS. 2/5 results. Moreover, Prof. Rammelsberg, who followed exactly the method of Deville, obtained but a very small product, and found it very difficult to prevent the cracking of the glass tube in which the experiment was conducted, by the action of the vapor of sodium on aluminium chloride. It appeared to me that a great amount of time, trouble and expense, as well as long practice, was necessary to obtain even small quantities of this remarkable metal. " The employment of aluminium chloride and its compounds with alkali chlorides is particularly inconvenient, owing to their volatility, deliquescence, and to the necessity of preventing all access of air during their treatment with sodium. It very soon occurred to me that it would be better to use the fluoride of aluminium instead of the chloride ; or rather the combination of the fluoride with alkaline fluorides, such as we know them through the investigations of Berzelius, who pointed out the strong affinity of aluminium fluoride for sodium fluoride and potassium fluoride, and that the mineral occurring in nature under the name of cryolite was a pure compound of aluminium fluoride and sodium fluoride. " This compound is as well fitted for the preparation of aluminium by means of sodium as aluminium chloride or aluminium-sodium chloride. Moreover, as cryolite is not vola- tile, is readily reduced to the most minute state of division, is free from water and does not attract moisture from the air, it affords peculiar advantages over the above-mentioned com- pounds. In fact, I succeeded with much less trouble in pre- paring aluminium by exposing cryolite together with sodium to a strong red heat in an iron crucible, than by using alu- minium chloride and its compounds. But the scarcity of cryo- lite prevented my pursuing the experiments. In consequence of receiving, however, from Prof. Krantz, of Bonn, a consider- able quantity of the purest cryolite at a very moderate price ($2 per kilo), I was enabled to renew the investigation. " I was particularly stimulated by finding, most unexpect- edly, that cryolite was to be obtained here in Berlin commer- 2/6 ALUMINIUM. cially at an inconceivably low price. Prof. Krantz had already informed me that cryolite occurred in commerce in bulk, but could not learn where. Shortly after, M. Rudel, the manager of the chemical works of H. Kunheim, gave me a sample of a coarse white powder, large quantities of which were brought from Greenland by way of Copenhagen to Stettin, under the name of mineral soda, and at the price of $3 per centner. Samples had been sent to the soap boilers, and a soda-lye had been extracted from it by means of quicklime, especially adapted to the preparation of many kinds of soap, probably from its containing alumina. It is a fact, that powdered cryolite is completely decomposed by quicklime and water. The fluoride of lime formed contains no alumina, which is all dissolved by the caustic soda solution ; and this, on its side, is free from fluor- ine, or only contains a minute trace. I found this powder to be of equal purity to that received from Prof. Krantz. It dis- solved without residue in hydrochloric acid (in platinum ves- sels) ; the solution evaporated to dryness with sulphuric acid, and heated till excess of acid was dissipated, gave a residue which dissolved completely in water, with the aid of a little hydrochloric acid. From this solution, ammonia precipitated a considerable quantity of alumina. The solution filtered from the precipitate furnished, on evaporation, a residue of sulphate of soda, free from potash. Moreover, the powder gave the well-known reactions of fluorine in a marked degree. This powder was cryolite of great purity : therefore the coarse pow- der I first obtained was not the form in which it was originally produced. It is now obtainable in Berlin in great masses ; for the preparation of aluminium it must, however, be reduced to a very fine powder. " In my experiments on the preparatipn of aluminium, which were performed in company with M. Weber, and with his most zealous assistance, I made use of small iron crucibles, i ^ inches high and i^ inches upper diameter, which I had cast here. In these I placed the finely divided cryolite between thin layers of sodium, pressed it down tight, covered it with a REDUCTION OF ALUMINIUM COMPOUNDS. 277 good layer of potassium chloride (KCl), and closed the cruc- ible with a well-fitting porcelain cover. I found potassium chloride the most advantageous flux to employ ; it has the low- est specific gravity of any which could be used, an important point when the slight density of the metal is taken into consid- eration. It also increases the fusibility of the sodium fluoride. I usually employed equal weights of cryolite and potassium chloride, and for every five parts of cryolite two parts of so- dium. The most fitting quantity for the crucible was found to be ten grammes of powdered cryolite. The whole was raised to a strong red heat by means of a gas-air blowpipe. It was found most advantageous to maintain the heat for about half an hour, and not longer, the crucible being kept closely covered the whole time ; the contents were then found to be well fused. When quite cold the melted mass is removed from the crucible by means of a spatula ; this is facilitated by striking the outside with a hammer. The crucible may be employed several times, at last it is broken by the hammer blows. The melted mass is treated with water, when at times only a very minute evolution of hydrogen gas is observed, which has the same unpleasant odor as the gas evolved during solution of iron in hydrochloric acid. The carbon contained in this gas is derived from a very slight trace of naphtha adhering to the sodium after drying it. On account of the difficult solubility of sodium fluoride, the mass is very slowly acted on by water, although the insolubility is somewhat diminished by the presence of the potassium chlo- ride. After twelve hours the mass is softened so far that it may be removed from the liquid and broken down in a porce- lain mortar. Large globules of aluminium are then discovered, weighing from 0.3 to 0.4 or even 0.5 grammes, which may be separated out. The smaller globules cannot well be separated from the undecomposed cryolite and the alumina always pro- duced by washing, owing to their being specifically lighter than the latter. The whole is treated with nitric acid in the cold. The alumina is not dissolved thereby, but the little globules then first assume their true metallic lustre. They are dried and 278 ALUMINIUM. rubbed on fine silk muslin ; the finely powdered, undecom- posed cryolite and alumina pass through, while the globules remain on the gauze. The mass should be treated in a plati- num or silver vessel; a porcelain vessel would be powerfully acted on by the sodium fluoride. The solution, after standing till clear, may be evaporated to dryness in a platinum capsule, in order to obtain the sodium fluoride, mixed however with much potassium chloride. The small globules may be united by fusion in a small well-covered porcelain crucible, under a layer of potassium chloride. They cannot be united without a flux. They cannot be united by mere fusion, like globules of silver, for instance, for though they do not appear to oxidize on ignition in the air, yet they become coated with a scarcely perceptible film of oxide, which prevents their running together into a mass. This fusion with potassium chloride is always at- tended with a loss of aluminium. Buttons weighing 0.85 gramme lost, when so treated, 0.05 gramme. The potassium chloride when dissolved in water left a small quantity of alu- mina undissolved, but the solution contained none. Another portion of the metal had undoubtedly decomposed the potas- sium chloride ; and a portion of this salt and aluminium chlo- ride must have been volatilized during fusion (other metals, as copper and silver, behave in a similar manner — Pogg. Ixviii. 287). I therefore followed the instructions of Deville, and melted the globules under a stratum of aluminium-sodium chlo- ride in a covered porcelain crucible. The salt was melted first, and 'then the globules of metal added to the melted mass. There is no loss, or a very trifling one of a few milligrammes of metal, by this proceeding. When the aluminium is fused under potassium chloride its surface is not perfectly smooth, but exhibits minute concavities ; with aluminium-sodium chlo- ride this is not the case. The readiest method of preparing the double chloride for this purpose is by placing a mixture of alumina and carbon in a glass tube, as wide as possible, and inside this a tube of less diameter, open at both ends, and con- taining sodium chloride. If the spot where the mixture is REDUCTION OF ALUMINIUM COMPOUNDS. 279 placed be very strongly heated, and that where the sodium chloride is situated, more moderately, while a current of chlo- rine is passed through the tube, the vapor of aluminium chlo- lide is so eagerly absorbed by the sodium chloride that none or at most a trace is deposited in any other part of the tube. If the smaller tube be weighed before the operation, the amount absorbed is readily determined. It is not uniformly combined with the sodium chloride, for that part which is near- est to the mixture of charcoal and alumina will be found to have absorbed the most. " I have varied in many ways the process for the preparation of aluminium, but in the end have returned to the one just de- scribed. I often placed the sodium in the bottom of the cruci- ble, the powdered cryolite above it, and the potassium chloride above all. On proceeding in this manner, it was observed that much sodium was volatilzed, burning with a strong yellow flame, which never occurred when it was cut into thin slices and placed in alternate layers with the cryolite, in which case the process goes on quietly. When the crucible begins to get red hot, the temperature suddenly rises, owing to the commence- ment of the decomposition of the compound ; no lowering of the temperature should be allowed, but the heat should be steadily maintained, not longer, however, than half an hour. By pro- longing the process a loss would be sustained, owing to the action of the potassium chloride on the aluminium. Nor does the size of the globules increase on extending the time even to two hours : this efifect can only be produced by obtaining the highest possible temperature. If the process be stopped, how- ever, after five or ten minutes of very strong heat, the produc- tion is very small, as the metal has not had sufficient time to conglomerate into globules, but is in a pulverulent form and burns to alumina during the cooling of the crucible. No ad- vantage is gained by mixing the cryolite with a portion of chloride before placing it between the layers of sodium, neither did I increase the production by using aluminium sodium chloride to cover the mixture instead of potassium chloride. I 28o ALUMINIUM. repeatedly employed decrepitated sodium chloride as a flux in the absence of potassium chloride, without remarking any important difference in the amount of metal produced, although a higher temperature is in this case required. The operations may also be conducted in refractory unglazed crucibles made of stone- ware, and of the same dimensions, although they do not resist so well the action of the sodium fluoride at any high heats, but fuse in one or more places. The iron crucibles fuse, however, when exposed to a very high temperature in a charcoal fire. The product of metal was found to vary very much, even when operating exactly in the manner recommended, and with the same quantities of materials. I never succeeded in reducing the whole amount of metal contained in the cryolite (which con- tains 13 per cent, of aluminium). By operating on 10 grammes of cryolite, the quantity I always employed in the small iron crucible, the most successful result was 0.8 grm. But 0.5 or even 0.4 grm. may be considered favorable ; many times I obtained only 0.3 grm., or even less. These very different results depend on various causes, more particularly, however, on the degree of heat obtained. The greater the heat, the greater the amount of large globules, and the less amount of minutely divided metal to oxidize during the cooling of the crucible. I succeeded once or twice in reducing nearly the whole of the metal to one single button weighing 0.5 grm., at a very high heat in a stoneware crucible. I could not always obtain the same heat with the blowpipe, as it depended in some degree on the pressure in the gasometer in the gas-works, which varies at different hours of. the day. The following ex- periment will show how great the loss of metal may be owing to oxidation during the slow cooling of the crucible and its con- tents : In a large iron crucible were placed 35 grms. of cryolite in alternate layers with 14 grms. of sodium, and the whole cov- ered with a thick stratum of potassium chloride. The crucible, covered by a porcelain cover, was placed in a larger earthen one also covered, and the whole exposed to a good heat in a draft furnace for one hour, and cooled as slowly as possible. REDUCTION OF ALUMINIUM COMPOUNDS. 28 1 The product in this case was remarkably small, for O.135 grm. of aluminium was all that could be obtained in globules. The differences in the amounts reduced depend also in some degree on the more or less successful stratification of the sodium with the powdered cryolite, as much of the latter sometimes escapes decomposition. The greater the amount of sodium employed, the less likely is this to be the case ; however, owing to the great difference in their prices, I never employed more than 4 grms. of sodium to 10 grms. of cryolite. In order to avoid this loss by oxidation I tried another method of prepara- tion : Twenty grms. of cryolite were heated intensely in a gun- barrel in a current of hydrogen, and then the vapor of 8 grms. of sodium passed over it. This was effected simply by placing the sodium in a little iron tray in a part of a gun-barrel without the fire, and pushing it forward when the cryolite had attained a maximum temperature. The operation went on very well, the whole being allowed to cool in a current of hydrogen. After the treatment with water, in which the sodium fluoride dissolved very slowly, I obtained a black powder consisting for the most part of iron. Its solution in hydrochloric acid gave small evidence of aluminium. The small amounts I obtained, however, should not deter others from making these experi- ments. These are the results of first experiments, on which I have not been able to expend much time. Now that cryolite can be procured at so moderate a price, and sodium by De- ville's improvements will in future become so much cheaper, it is in the power of every chemist to engage in the preparation of aluminium, and I have no doubt that in a short time methods M'ill be found affording a much more profitable result. " To conclude, I am of opinion that cryolite is the best adapted of all the compounds of aluminium for the preparation of this metal. It deserves the preference over aluminium-sodium chloride or aluminium chloride, and it might still be employed with great advantage even if its price were to rise considerably. The attempts at preparing aluminium direct from alumina have as yet been unattended with success. Potassium and sodium 282 ALUMINIUM. appear only to reduce metallic oxides when the potash and soda produced are capable of forming compounds with a por- tion of the oxide remaining as such. Pure potash and soda, with whose properties we are very slightly acquainted, do not appear to be formed in this case. Since, however, alumina combines so readily with the alkalies to form aluminates, one would be inclined to believe that the reduction of alumina by^ the alkali metals should succeed. But even were it possible to^ obtain the metal directly from alumina, it is very probable that cryolite would long be preferred should it remain at a moderate price, for it is furnished by nature in a rare state of purity, and the aluminium is combined in it with sodium and fluorine only, which exercise no prejudicial influence on the properties of the metal, whereas alumina is rarely found in nature in a pure state and in a dense, compact condition, and to prepare it on a large scale, freeing it from those substances which would act injuri- ously on the properties of the metal, would be attended with great difficulty. " The buttons of aluminium which I have prepared are so malleable that they may be beaten and rolled out into the finest foil without cracking on the edges. They have a strong metallic lustre. Some small pieces, not globular, however, were found in the bottom of the crucible, and occasionally ad- hering to it, which cracked on being hammered, and were dif- ferent in color and lustre from the others. They were evi- dently not so pure as the greater number of globules, and con- tained iron. On sawing through a large button weighing 3.8 grammes, it could readily be observed that the metal for abotit half a line from the exterior was brittle, while in the interior it was soft and malleable. Sometimes the interior of a globule contained cavities. With Deville, I have occasionally observed aluminium crystallized. A large button became striated and crystalline on cooling. Deville believes he has observed reg- ular octahedra, but does not state this positively. According to my brother's examination, the crystals do not belong to any of the regular forms. As I chanced on one occasion to attempt REDUCTION OF ALUMINIUM COMPOUNDS. 283 the fusion of a large, flattened- out button of rather impure aluminium, without a flux, I observed, before the heat was suffi- cient to fuse the mass, small globules sweating out from the surface. The impure metal being less fusible than pure metal, the latter expands in fusing and comes to the surface." Experiments of Percy and Dick (1855). After the publication of Rose's results, widespread attention was directed toward this field, and it was discovered that some six months previously Dr. Percy, in England, had accomplished almost similar results, and had even shown a specimen of the metal to the Royal Institution, but with the singular fact of ex- citing very little attention. These facts are stated at length in the following paper written by Allan Dick, Esq., which ap- peared in November, 1855, two months after the publication of H. Rose's paper: — * " In the last number of this magazine was the translation of a paper by H. Rose, of Berlin, describing a method of preparing aluminium from cryolite. Previously, at the suggestion of Dr. Percy, I had made some experiments on the same subject in the metallurgical laboratory of the School of Mines ; and as the results obtained agree very closely with those of Mr. Rose, it may be interesting to give a short account of them now, though no detailed description was published at the time, a small piece of metal prepared from cryolite having simply been shown at the weekly meeting of the Royal Institution, March 30, 1855, accompanied by a few words of explanation by Faraday. " Shortly after the publication of Mr. Deville's process for preparing aluminium from aluminium chloride, I tried along with Mr. Smith to make a specimen of the metal, but we found it much more difficult to do than Deville's paper had led us to anticipate, and had to remain contented with a much smaller piece of metal than we had hoped to obtain. It is, however, undoubtedly only a matter of time, skill, and expense to join * Phil. Mag., Nov. 1855. 284 ALUMINIUM. successful practice with the details given by Deville. Whilst making these experiments, Dr. Percy had often requested us to try whether cryolite could be used instead of the chlorides, but some time elapsed before we could obtain a specimen of the mineral. The first experiments were made in glass tubes sealed at one end, into which alternate layers of finely powdered cryolite and sodium cut into small pieces were introduced, and covered in some instances with a layer of cryolite, in others by sodium chloride. The tube was then heated over a gas blow- pipe for a few minutes till decomposition had taken place, and the product was melted. When cold, on breaking the tube, it was found that the mass was full of small globules of aluminium, but owing to the specific gravity of the metal and flux being nearly alike, the globules had not collected into a button at the bottom. To effect this, long-continued heat would be required, which cannot be given in glass tubes owing to the powerful action of the melted fluoride on them. To obviate this difficulty, a platinum crucible was lined with magnesia by ramming it in hard and subsequently cutting out all but a lining. In this, alternate layers of cryolite and sodium were placed, with a thickish layer of cryolite on top. The cruci- ble was covered with a tight-fitting lid, and heated to redness for about half an hour over a gas blowpipe. When cold it was placed in water, and after soaking for some time the contents were dug out, gently crushed in a mortar, and washed by de- cantation. Two or three globules of aluminium, tolerably large considering the size of the experiment, were obtained, along with a large number of very small ones. The larger ones were melted together under potassium chloride. Some experiments made in iron crucibles were not attended with the same success as those of Rose : no globules of any considerable size re- mained in the melted fluorides ; the metal seemed to alloy on the sides of the crucible, which acquired a color like zinc. It is possible that this difference may have arisen from using a higher temperature than Rose, as we made these experiments in a furnace, not over the blowpipe. Porcelain and clay cru- REDUCTION OF ALUMINIUM COMPOUNDS. 285 cibles were also tried, but laid aside after a few experiments, owing to the action of the fluorides upon them, which in most cases was sufificient to perforate them completely." Deville's Methods (1856-8). * " I have repeated and confirmed all the experiments of Dr. Percy and H. Rose, using the specimens of cryolite which I obtained from London through the kindness of MM. Rose and Hofmann. I have, furthermore, reduced cryolite mixed with sodium chloride by the battery, and I believe that this will be an excellent method of covering with aluminium all the other metals, copper in particular. Anyhow, its fusibility is consid- erably increased by mixing it with aluminium-sodium chloride. Cryolite is a double fluoride of aluminium and sodium, con- taining 13 per cent, of aluminium and having the formula AlFj.sNaF. I have verified these facts myself by many analyses. " In reducing the cryolite I placed the finely pulverized mix- ture of cryolite and sodium chloride in alternate layers with sodium in a porcelain crucible. The uppermost layer is of pure cryolite, covered with salt. The mixture is heated just to complete fusion, and after stirring with a pipe-stem, is let cool. On breaking the crucible, the aluminium is often found united in large globules, easy to separate from the mass. The metal always contains silicon, which increases the depth of its natural blue tint and hinders the whitening of metal by nitric acid, be- cause of the insolubility of the silicon in that acid. M. Rose's metal is very ferruginous. I have verified all M. Rose's ob- servations, and I agree with him concerning the return of metal, which I have always found very small. There are al- ways produced in these operations brilliant flames, which are observed in the scoria floating on the aluminium, and which are due to the gas burning and exhaling a very marked odor of phosphorus. In fact, phosphoric acid exists in cryolite, as * Ann. de Chim. et de Phys. [3], xlvi. 451. 286 ALUMINIUM. one may find by treating a solution of the mineral in sulphuric acid with molybdate of ammonia, according to H. Rose's re- action. " M. Rose has recommended iron vessels for this operation, because of the rapidity with which alkaline fluorides attack earthen crucibles and so introduce considerable silicon into the metal. Unfortunately, these iron crucibles introduce iron into the metal. This is an evil inherent in this method, at least in the present state of the industry. The inconveniences of this method result in part from the high temperature required to complete the operation, and from the crucible being in direct contact with the fire, by which its sides are heated hotter than the metal in the crucible. The metal itself, placed in the lower part of the fire, is hotter than the slag. This, according to my observations, is an essentially injurious condition. The slag ought to be cool, the metal still less heated, and the sides of the vessel where the fusion occurs ought to be as cold as pos- sible. The yield from cryolite, according to Rose's and my own observations, is also very small. M. Rose obtained from lo of cryolite and 4 of sodium about 0.5 of aluminium. This is due to the affinity of fluorine for aluminium, which must be very strong not only with relation to its affinity for sodium, but even for calcium, and this affinity appears to increase with the tem- perature, as was found in my laboratory. Cryolite is most convenient to employ as a flux to add to the mixture which is fused, especially when operating on a small scale. "The argument which decided the company at Nanterre not to adopt the method of manufacture exclusively from cryolite was the report of M. de Chancourtois, mining engineer, who had just returned from a voyage to Greenland. According to the verbal statements of this gentleman, the gite at Evigtok is accessible only during a very short interval of time each year, and, because of the ice fields, can only be reached then by a steamboat. The workmen sent from Europe to blast and load up the rock have scarcely one or two months of work possible. The local workmen remain almost a whole year deprived of all REDUCTION OF ALUMINIUM COMPOUNDS. 287 communication with the rest of the world, without fresh provi- sions or fuel other than that brought from Europe in the short interval that navigation is open. The deposit itself, which is scarcely above sea-level, can be easily worked with open roof, but the neighborhood of the sea in direct contact with the vein, the unorganized manner of working, and the lack of care in keeping separate the metalliferous portions of the ore — all com- bine to render the mineral very costly, and further developments underground almost impossible. " It is therefore fortunate that cryolite is not indispensable, for no one would wish to establish an industry based on the employment of a material which is of such uncertain supply." Tissier Bros.' Method (1857). The process adopted in the works at Amfreville, near Rouen, directed by Tissier Bros., is essentially that described by Percy and Rose. The method of operating is given by the Tissier Bros, themselves in their book as follows : "After having finely powdered the cryolite, it is mixed with a certain quantity of sodium chloride (sea salt), then placed be- tweeen layers of sodium used in the proportions given by M. Rose, in large refractory crucibles. These are heated either in a reverberatory furnace or in a wind furnace capable of giving a temperature high enough to melt the fluoride of sodium pro- duced by the reaction. As the sodium fluoride requires a pretty high temperature to fuse it, the heat will necessarily be higher than that required in the reduction of the double chloride of aluminium and sodium. When the contents of the crucible are melted, so as to be quite liquid, the fusion is poured into cast-iron pots, at the bottom of which the aluminium col- lects in one or several lumps." Tissier Bros, claimed the following advantages for the use of cryolite : " Cryolite comes to us of a purity difficult to obtain with the double chloride of aluminium and sodium, to which it exactly corresponds ; and since, thanks to the perfection we have at- 288 ALUMINIUM. tained in using it, the return of aluminium is exactly correspon- dent to the amount of sodium used in reduction, it is easily seen what immense advantages result from its employment. The double chloride deteriorates in the air, it gives rise in the works to vapors more or less deleterious and corrosive, and its price is always high. Cryolite can be imported into France at a price so low that we have utilized it economically for making commercial carbonate of soda ; it remains unaltered in the air, emits no deleterious vapors, and its management is much more easy than that of the double chloride. Moreover, on compar- ing the residues of the two methods of reduction, the manufac- ture from double chloride leaves sodium chloride, almost with- out value, while the manufacture from cryolite leaves sodium fluoride, which may be converted for almost nothing into caustic soda or carbonate, and so completely cancels the cost of the cryolite from the cost of aluminium. The most serious objection which can be made to using cryolite is that the sources of the mineral being up to the present very limited, the future prospect of aluminium Hes necessarily in the utilization of clays and their transformation into aluminium chloride ; but, admitting that other sources of cryolite may not be discov- ered hereafter, the abundance of those which exist in Greenland will for a long time to come give this mineral the preference in the manufacture of aluminium." The most serious difhculty which this process had to meet, and which it could not overcome, was the high content of sili- con in the metal produced. A specimen of their aluminium made in 1859 contained 4.4 per cent, of silicon alone (see p. 54, Analysis 7). The firm at Rouen went out of business about 1863 or 1865 — I am unable to give the exact date. From that time until quite recently, it has been considered that the best use of cryolite is as a flux in the preparation of aluminium from aluminium-sodium chloride, in which case the slag is not sodium fluoride, but aluminium fluoride, which acts but slightly on the containing vessel. REDUCTION OF ALUMINIUM COMPOUNDS. 289 Wohler' s Modifications (1856). Wohler suggested the following modifications of Deville's process of reducing cryolite in crucibles, by means of which the reduction can be performed in an earthen crucible without the metal produced taking up silicon. *"The finely pulverized cryolite is mixed with an equal weight of a flux containing 7 parts sodium chloride to 9 parts potassium chloride. This mixture is then placed in alternate layers with sodium in the crucible, 50 parts of the mixture to 10 of sodium, and heated gradually just to its fusing point. The metal thus obtained is free from silicon, but only one-third of the aluminium in the cryolite is obtained." In spite of the small yield, this method was used for some time by Tissier Bros. Gerhard's Furnace (1858). This furnace was devised for the reduction of aluminium either from aluminium-sodium chloride or from cryolite, the object being to prevent loss of sodium by ignition. It was in- vented and patented by W. F. Gerhard. | " It consists of a reverberatory furnace having two hearths, or of two crucibles, or of two reverberatory furnaces, placed one above the other and communicating by an iron pipe. In the lower is placed a mixture of sodium with the aluminium compound, and in the upper a stratum of sodium chloride, or of a mixture of this salt and cryolite, or of the slag obtained in a previous ope- ration. This charge, when melted, is made to run into the lower furnace in quantity sufficient to completely cover the mixture contained therein, and so to protect it from the air. The mixture thus covered is reduced as by the usual operation." Whether a furnace was ever put up and operated on this principle, the author cannot say. It is possible that it may have been used in the English manufactory started in 1859 at Battersea near London. (See p. 18.) * Ann. der Chem. und Pharm. 99,255. t Eng. Pat., 1858, No. 2247. 19 290 ALUMINIUM. Thompson and White's Patent (1887). * J. B. Thompson and W. White recommend heating a mix- ture of 3 parts sodium and 4 parts cryolite to 100°, whereby the sodium becomes pasty and the whole can be well kneaded together with an iron spatula. When cold, 4 parts of alumin- ium chloride are added, and the mixture put into a hopper on top of a well-heated reverberatory furnace, with a cup-shaped hearth. The charge is dropped into the furnace and the reaction takes place at once. To produce alloys, this patent claims 16 parts of cryolite are mixed with 5 parts of sodium, the metal added before reduction and the mixture treated as above, by which means explosions are avoided. The pre- liminary heating to 100° is effected in a jacketed cast-iron pot connected with a circulating boiler. Hampe's Experiment (1888). t Dr. W. Hampe failed to produce aluminium bronze by treat- ing cryolite with sodium in the presence of copper. A mixture of Finely divided copper 44 grammes, Sodium, in small pieces, 15 " Finely powdered cryolite 100 " was melted rapidly in a carbon-lined crucible. There were no sounds given out such as usually accompany other reductions by sodium, but much sodium vapor was given off. The copper button contained only traces of aluminium. Netto's Process (1887). Dr. Curt Netto, of Dresden, patented in England and Ger- many, in spring and autumn of 1887, processes for producing sodium and potassium and methods of using them in producing aluminium. His experiments were made in conjunction with Dr. Salomon, of Essen, and the fact that the experimental ap- * English patent 8427, June 11, 1887. tChemiker Zeitung, (Cothen), xii, p. 391. REDUCTION OF ALUMINIUM COMPOUNDS. 29 1 paratus was put up in Krupp's large steel works at Essen gave rise to reports that the latter had taken up the manufacture of aluminium by some new and very successful process, intending to use it for alloys in making cannon. * In the latter part of 1888 was formed the Alliance Aluminium Co. of London, England, capitalized at ;£'5oo,ooo, purposing to manufacture sodium and aluminium, and owning the English, French, German, and Belgian patents of Dr. Netto for the pro- duction of those metals, also the processes of a Mr. Cunning- ham for the same purpose, also a process for the production of artificial cryolite by the regeneration of slag (provisionally pro- tected by its inventor, Mr. Forster, of the Lonesome Chemical Works, Streatham), and, lastly, a process invented by Drs. Netto and Salomon by which aluminium can be raised to the highest standards of purity on a commercial scale. A note accompanying the above announcement stated that the exhaust- ive experiments made at Essen had satisfactorily demonstrated the practicability of the processes, and that the company had already contracted with the cryolite mines of Greenland for all the cryolite they would need. In June, i888,t the Alliance Aluminium Company had in operation a small aluminium plant at King's Head Yard, Lon- don, E. C, and when the process was in continuous opera- tion the cost of the metal was set down at 6 shillings per pound. It is probable that the metal exhibited in the Paris Exposition of 1889 was produced at this place. In April, 1889,! ten acres of ground had been leased at Hepburn on which to produce sodium by Capt. Cunningham's process. The sodium produced was to be sent to Wallsend to be used by the Alliance Aluminium Company, who were erect- ing a large works at that place. As for Capt. Cunningham's sodium processes, they are ap- parently identical with Dr. Netto's. Cunningham's aluminium ♦American Register, Paris, August, 1888. t Engineering, June i, 1888. X E. and M. J., April 27, 1889. 292 ALUMINIUM. process* consists in melting the sodium to be used with lead, in order to facihtate the submerging of the sodium under the molten aluminium salt. The alloy is cast into bars and added piece by piece to the bath of molten aluminium salt on the hearth of a reverberatory furnace. After the reaction the mix- ture separates by specific gravity into lead, containing a little aluminium, and aluminium containing a little lead, the slag floating on top of all. Aluminium is known to have so small an attraction for lead that this result becomes possible. Fig. 26. Dr. Netto recommends several processes, the one used at London being the following: — | One hundred parts of cryolite and 30 to 100 parts of sintered sodium chloride are melted at a red heat in a well-covered clay crucible. (Another arrangement, and apparently a better, is to melt this mixture on the hearth of a reverberatory furnace and tap it into a deep, conical ladle, in which the succeeding opera- tions proceed as about to be described. See Fig. 26.) As soon as the bath is well fused, 35 parts of sodium at the end of a rod, and * English Patent, 16727, Dec. 5, 1887. t German Patent (D. R. P.), 45198, March 26, 1887. REDUCTION OF ALUMINIUM COMPOUNDS. 293 covered over by a perforated concave plate is pushed quickly down to the bottom of the crucible. The plate mentioned fits across the whole section of the crucible at its lower part, so that the fusible, easily volatile sodium, being vaporized, is divided into very fine streams as it passes upwards through the bath, and is all utilized before it reaches the surface. In this way the re- action is almost instantaneous, and the contents can be poured out at once into iron pots, where, on cooling, the metal is found as a large lump at the bottom. It is further observed that to avoid explosions on introducing the sodium it should have in it no cavities which might contain moisture or hydrocarbons. In consequence of the reaction be- ing over so quickly, and the heat set free in the reduction, the syrupy fusion becomes thin as water, and the aluminium dis- seminated through the mass collects together completely, so that the slag contains no particles visible to the eye. Since the reduction, pouring, and cooling take place so quickly, the alu- minium is not noticeably redissolved by the bath, thus insuring a high return of metal. By using 35 parts of sodium to 100 parts of cryolite, 10 parts of aluminium are obtained. Since the cryolite contains 13 per cent, of aluminium, the return is yy per cent, of the amount of metal in the cryolite; since 35 parts of sodium should theoretically displace 14 parts of alu- minium, the return is 71 per cent, of the amount which the sodium should produce. Dr. Netto claims that this is double the return formerly obtained from cryolite. The metal pro- duced is said to be from 98.5 to 99 per cent. pure. The apparatus erected at Krupp's works at Essen, which was described by the newspapers as similar to a Bessemer converter, was constructed and operated as follows : A large iron cylinder is pivoted at the centre in a manner similar to a Bessemer con- verter. Passing through the centre of the cylinder, longitudi- nally, is a large iron tube in which generator gas is burnt to heat the vessel.. To heat it up, it is placed erect, connection made with the gas-main, while a hood above connects with the chimney. On top of the cylinder, a close valve communicates 294 ALUMINIUM. with the interior, for charging, and at the other end is a tap- hole. The charge of cryoHte being put in, the flame is passed through the central tube until the mineral is well fused. Then soHd or melted sodium is passed in at the top, the valve is screwed tight, the gas shut off, and the whole cylinder is rotated several times until reduction is complete, when it is brought upright, the tap-hole opened and slag and metal tapped into a deep iron pot, where they separate and cool. Aluminium thus made could not but contain much iron, even up to 14 per cent., it is said, which would prevent its use for any purpose ex- cept alloying with iron. To procure pure aluminium, the ves- sel would have to be properly fettled. Dr. Netto also devised an arrangement similar to Heaton's apparatus for making steel. It consisted of a large, well-lined vessel on trunnions, the bottom of which was filled to a certain depth with sodium, then a perforated aluminium plate placed like a false bottom over it. On pouring molten cryolite into the vessel, the aluminium plate prevented the sodium from rising en masse to the surface of the cryolite. After the reaction was over, the vessel was tilted and the slag and metal poured out into iron pots. The modification of the crucible method appears to have been the most feasible of Netto's processes, and was probably that used at Wallsend by the Alliance Aluminium Com- pany. Outside estimates of the cost of aluminium to this com- pany placed it at $1.50 to $2 per pound. They were selling in the latter part of 1889 at 11, 13, and 15 shillings per pound, according to quality, but were forced out of the business by the electrolytic processes in 189 1. Grabau's Process (1887). There is only one patentee claiming particularly the reduc- tion of aluminium fluoride by sodium — Ludwig Grabau, of Hannover, Germany. His patents on this subject are im- mediately preceded by others on a method of producing the aluminium fluoride cheaply, which are described on p. 171, and REDUCTION OF ALUMINIUM COMPOUNDS. 295 the inventor has patented a process which will furnish him with cheap sodium. Mr. Alexander Siemens is authority for the statement that a plant was in operation in the spring of 1889, in Hannover, producing aluminium by this process on a com- mercial scale. The principal object of Mr. Grabau's endeavors has been to produce metal of a very high degree of purity. To this end every precaution is taken to procure pure materials and to prevent contamination during reduction. We will quote from a paper written by Mr. Grabau* and also from his speci- fications, f the following explanation of the process : " The purifying of impure aluminium is accompanied by so many difficulties that it appears almost impossible. It is there- fore of the greatest importance to so conduct the operation that every impurity is excluded from the start. Molten aluminium compounds, whether a flux is added or not, attack any kind of refractory vessels and become siliceous if these vessels are made of chamotte or like materials, or if made of iron they become ferruginous. These impurities are reduced in the further pro- cesses and pass immediately into the aluminium as iron, silicon, etc. Evidently the case is altered if an aluminium compound which is infusible can be used advantageously. Aluminium fluoride is infusible and also retains its pulverized condition when heated up to the temperature needed for its use ; it can therefore be heated in a vessel of any kind of refractory mater- ial, or even in a metallic retort, without danger of taking up any impurity. " Further, it is necessary for succeeding in producing alu- minium that the reduced metal thall unite to a large body after the reduction. For this purpose all previous processes use fluxes, and usually cryolite. But cryolite is impure, and there- fore here is a source of many of the impurities in commercial aluminium. Dr. K. Kraut, of Hannover, has observed that, according to the recent analyses of Fresenius and Hintz, com- * Zeitschrift fur angewandte, Chemie, 1889, vol. 6. t German Pat. (D. R. P.) 47°3'. Nov. 15, 1887. English Pat. 15593, Nov. 14, 1887. U. S. Patents 386704, July 24, l888; and 400449, April 2, 1889. 296 ALUMINIUM. mercial cryolite contains 0.80 to 1.39 per cent, of silicon, and o.ii to 0.88 per cent, of iron, and that these impurities inter- penetrate the mineral in such a manner as to be often only vis- ible under the microscope, and therefore totally impossible of removal by mechanical means. It is thus seen that the avoid- ance of the use of any Rux is of great importance as far as producing pure metal is concerned, as well as from an eco- nomic standpoint. " By the following process it is also possible to reduce alu- minium fluoride by ?odium without the vessel in which reduc- tion takes place being attacked either by the aluminium-sodium fluoride formed or by the reduced aluminium. For this pur- pose the aluminium fluoride and sodium are brought together in such proportions that after the reaction there is still suffi- cient aluminium fluoride present to form with the sodium flu- oride resulting from the reaction a compound having the com- position of cryolite. The reaction, therefore, will be 2AlF3-h3Na=Al-l-AlF3.3NaF. " Using these proportions, the aluminium fluoride must be previously warmed up to about 600° C, in order that when it is showered down upon the melted sodium the reaction may com- mence without further application of heat. The aluminium fluoride remains granular at this temperature and therefore re- mains on top of the melted sodium, like saw-dust or meal upon water, and under its protection the reaction proceeds from below upwards — an important advantage over the usual method of pouring molten aluminium compounds on to sodium, in which the lighter sodium floats to the top and burns to waste. If solid sodium is used in my process the aluminium fluoride must be somewhat hotter on being poured into the reduction vessel, or about 700° C. For carrying out the process the re- duction vessel must be artificially cooled, so as to form a lining by chilling some of the aluminium-sodium fluoride formed by the reaction, on the inner walls. This lining is in no wise further attacked by the contents of the vessel, nor can it evi- dently supply to them any impurity. REDUCTION OF ALUMINIUM COMPOUNDS. 297 Fig. 27. 298 ALUMINIUM. "The furnace A (Fig. 27) with grate B and chimney C, serves for heating the iron retorts D and E, which are coated with chamotte and protected from the direct action of the flame by brick work. The vessel D serves for heating the aluminium fluoride, and is provided with a damper or sliding valve be- neath. The sodium is melted in E, and can be emptied out by turning the cock k. The water-jacketed reduction vessel is mounted on trunnions to facilitate emptying it. The retorts are first heated dark red-hot, and D is filled with the conven- ient quantity of aluminium fluoride. When this has become red hot, as is shown by a small quantity of white vapor is- suing from it, the required quantity of sodium is put into E. This melts very quickly, and is then immediately run into the reduction vessel by opening the stop-cock k. As soon as it is transferred, the slide at the base of the retort D is pulled out and the whole quantitity of aluminium fluoride falls at once upon the sodium, and the reaction begins. As before re- marked, the granular form of the aluminium fluoride keeps it on top of the sodium, so that the latter is completely covered during the whole reaction. This prevents almost altogether any waste of sodium by volatilization. Dr. K. Kraut testifies to an operation which he witnessed in which the return showed 83 per cent, of the sodium to have been utilized. An efficiency in this respect of over 90 per cent, has been occasionally reached, while the average is 80 to 90. Ad. Wurtz states that the average for several years' working of the Deville process showed only 74.3 per cent, of the quantity of aluminium pro- duced which the sodium used could have given. "During the reaction a very high temperature is developed, so that the cryolite formed becomes very fluid, but is chilled against the sides of the vessel to a thickness of a centimetre or more. This crust is a poor conductor of heat, and is neither attacked by the fluid cryolite nor by the aluminium. In con- sequence of the great fluidity of the bath, it is possible for the aluminium to unite into a body without the use of any flux, The reaction being over, which is accomplished with the above REDUCTION OF ALUMINIUM COMPOUNDS. 299 proportions of materials in a few seconds, and the vessel hav- ing been shaken briskly backwards and forwards a few times to facilitate the settling of the aluminium, the whole is turned on the trunnions and emptied into a water-jacketed iron pot, where it cools. The crust of cryolite inside the reduction vessel is left there, and the apparatus is ready for another operation." M. Grabau, in a private communication to the author, sums up the advantages of his process, including the production of the aluminium fluoride, as follows : — 1. The process is not dependent on natural cryolite, which is expensive, impure and not easily purified. 2. The raw material — aluminium sulphate — can be procured in large quantities and of perfect purity. 3. The aluminium fluoride is produced by a wet process, which offers no difficulties to production on a large scale. 4. The fluorspar may be completely freed from foreign metals by washing with dilute acid ; any silica present is not injurious, as it remains undissolved in the residue during the reactions. 5. The cryolite formed in each reduction contains no impur- ities, and an excess of it is produced which can be sold. 6. The reduction of aluminium fluoride by my method gives a utilization of 80 to 90 per cent, of the sodium used, which is much more than can be obtained by other processes. 7. Aluminium fluoride is infusible, and can therefore be heated in a vessel of any refractory material without taking up any impurities. It is also unchanged in the air, and can be kept unsealed for any length of time without deteriorating in the least. 8. No flux has to be added for reduction, the use of impure flux being a frequent cause of impurity of the metal. In point of fact, M. Grabau has succeeded in producing sev- eral hundred pounds of aluminium averaging over 99^ per cent. pure. Dr. Kraut reports an analysis of an average speci- men with 99.62 per cent, of aluminium (see Analysis 20, p. 54), and metal has been made as pure as 99.8 per cent., a piece of 300 ALUMINIUM. which has been kindly forwarded the author by M. Grabau, and I freely admit it to be as fine a specimen of aluminium as I have ever seen. Metal of such purity and fineness can only be made by the electrolytic processes at considerable expense over ordi- nary best commercial metal, since they must use chemically pure alumina and extra precautions as to the purity of the electrodes. It therefore appears possible that M. Grabau may yet be able to manufacture and sell this extra quality aluminium, if he can bring its price anywhere near that of the electrolytic aluminium. The Grabau Aluminium Werke, Trotha, Germany, operates the Grabau processes, and does a business in manufacturing and selling sodium. CHAPTER XI. REDUCTION OF ALUMINIUM COMPOUNDS BY THE USE OF ELECTRICITY. As preliminary to the presentation of the various electrolytic methods which have been proposed or , used, it may be profit- able to review briefly the principles of electro-metallurgy as they apply to the decomposition of aluminium compounds. Some additional observations have been already included in Chapter VIII. The atomic weight of aluminium being 27, its chemical equivalent, or the weight of it equal in consbining power to one part of hydrogen, is 9. Therefore a current of quantity sufiS- cient to liberate i part of hydrogen in a certain time would produce 9 parts of aluminium in the same time, according to the fundamental law of electric decomposition. It has been determined that a current of i ampere acting for one second, liberates 0.00001035 grammes of hydrogen; therefore it will produce or set free from combination in the same time, 0.00009315 grammes of aluminium. This is the electro-chemical equivalent of aluminium. Now, from thermo-chemical data we know that the amount of energy required to set free a certain weight of aluminium will vary with the compound from which it is produced ; but the above equivalent is independent of the compound decomposed, therefore there must be some varying factor connected with the quantity of the current to account for the different amounts of work which the current does in decomposing diflferent compounds of the same element. This is exactly in accordance with the principles of the mechanical or thermal equivalent of the electric current, for the statement " a current of one ampere," while it expresses a definite quan- (301) 302 ALUMINIUM. tity of electricity, yet carries no idea of the energy represented by that current; we must know against what resistance or with what electro- motive force that quantity is moved, and then we can calculate its mechanical equivalent. Now, a current of i ampere flowing against a resistance of i ohm, or in other words, with a moving force or intensity of i volt, represents a quantity of energy in one second equal to 0.00024 calories of heat or to O.I kilogrammetre of work, and is therefore nearly ^ijf of a horse power. Therefore we can calculate the theoreti- cal intensity of current necessary to overcome the affinities of any aluminium compound for which we know the appropriate thermal data. For instance, when aluminium forms its chlo- ride (see p. 228) ^ — — — =5,960 calories are developed per 54 kilo of aluminium combining ; consequently the liberating of 0.00009315 grammes of aluminium (its electro-chemical equiva- lent), requires the expenditure of an amount of energy equal to 0.00009315 X 5.960 = 0.000555 calories. Since a current of I ampere at an intensity of i volt represents only 0.00024 cal- ories, the intensity of current necessary to decompose alumin- ium chloride is theoretically — '- — ^= 2.3 volts. In a simi- 0.00024 lar manner we can calculate that to decompose alumina would , . ^. , , 391600 0.00000009315 require an electro-motive force of x Z^-^ = 54 0.00024 2.8 volts. These data would apply only to the substances named, in a fused anhydrous state ; with hydrated aluminium chloride in solution, a far. greater electro-motive force would be necessary. If we had the thermal data we could also calculate the intensity of current necessary to decompose the sulphate, nitrate, acetate, etc., in aqueous solution; but failing these, we can reason from analogy that it would be several volts in each case. It must be noted also, that these heats of combination are those observed at ordinary temperatures. To find the voltage required at high temperatures we must make allowance for the REDUCTION OF ALUMINIUM COMPOUNDS. 303 weakening of the affinities, that is, for the decrease in heat of combination as the temperature rises. When the rate of this decrease is known, the true voltage required at any temperature can be calculated. Often the operation is reversed ; that is, the minimum electro-motive force required to effect decomposition is accurately measured at different temperatures, and from these data the variation in the heat of formation with the tem- perature can be calculated by reversing the above calculations. For example of this see p. 239. To utilize such calculations, we must bear in mind exactly what they represent. To decompose fused aluminium chloride, for instance, not only must the current possess an intensity of 2.3 volts, but it must in addition have power enough above this to overcome the transfer resistance of the electrolyte ; i. e., to force the current through the bath from one pole to the other. So, then, 2.3 volts would be the absolute minimum of intensity which would produce decomposition, and the actual intensity practically required would be greater than this, varying with the distance of the poles apart and the temperature of the bath as far as it affects the conducting power of the electrolyte. From this it would immediately follow that if the substance to be decomposed is an absolute non-conductor of electricity, no intensity of current will be able to decompose it. If, on the other hand, the substance is a conductor and the poles are within reasonable distance, a current of a certain intensity will always produce decomposition. The objection is immediately made that in most cases no metal is obtained at all, which is true not because none is produced, but because it is often dis- solved by secondary actions as quickly as it is produced. I need but refer to the historic explanation of the decomposition of caustic soda in aqueous solution, although we have cases hardly parallel to this in which the electrolyte itself dissolves the separated metal. How about the case of aqueous solutions ? Water requires a minimum electro-motive force of 1.5 volts to decompose it, and hence a prominent electrician remarked of a compound 304 ALUMINIUM. which theoretically required over 2 volts that its decomposition in aqueous solution would involve the decomposition of the water and therefore was impossible. This remark is only partly true ; for caustic soda requres over 2 volts, yet if mercury is present to absorb the sodium as it is set free and protect it from the water, we will obtain sodium, while the water is decomposed at the same time. The truth seems to be that if two substances are present which require different electro-motive forces to de- compose them, a current of a certain intensity will decompose the one requiring the least force, without affecting the other at all; but, if it is of an intensity sufficient to decompose the higher compound, then the current will be divided in some ratio between the two, decomposing them both. This theory would render theoretically possible the decomposition of aluminium salts in aqueous solution, with a waste of power proportional to the amount of water decomposed at the same time ; but whether any aluminium would be obtained would be contingent on the secondary action of the water on the aluminium. Pure aluminium in mass is not acted upon by water, but the foil is rapidly eaten away by boihng water. The state of division of the metal, then, determines the action of water on it, and it is altogether probable that the reason why aluminium is not easily deposited from aqueous solution is that, like sodium, it is attacked as soon as isolated, the acidity of the solution convert- ing the hydrate formed back into the salt, or else simply the hydrate remaining. Unfortunately, mercury does not exercise the same function with aluminium as with sodium, for water at- tacks its amalgam with aluminium, and so destroys the metal. It is possible that if some analogous solvent could be found which protected the aluminium from the action of water, the deposi- tion from aqueous solution could be performed quite easily. The electro-deposition of a metal using a soluble anode is entirely a different affair. In this case, while the salt in solu- tion is decomposed, yet it is immediately regenerated by the acid radical set free dissolving from the anode just the same quantity of metal as was deposited at the cathode. This action REDUCTION OF ALUMINIUM COMPOUNDS. 3OS exactly counterbalances the electromotive force required for decomposition, and leaves only the conduction resistance of the bath to be overcome. If this resistance is kept down so that the tension required to operate the bath is less than or not much greater than 1.5 volts, and the bath is well supplied with salt, there will be no water decomposed and a good plating may be obtained. This has been already practised on a large scale with aluminium. With anodes, however, which do not dissolve, the decom- position of the salt necessarily involves that of the water, if over 1.5 volts are required to decompose it. The result of this is that hydrogen gas is set free liberally at the cathode along with the metal, and prevents the latter from depositing as a smooth, dense metal, causing, in fact, the production of "sponge." This finely-divided spongy metal is in the very best condition to decompose water, and the result is its oxidation. However, the metal can only decompose water at a certain rate ; the oxi- dation does not take place instantaneously. If then we de- posit the metal faster than it can waste away by oxidation, by using a current of large quantity, we may succeed in gaining metal and thus secure a deposit. This way of overcoming the difficulty is assisted by using a very strong solution, which al- lows a current of large quantity to pass with less resistance, and also leaves less water uncombined to act on the metal. By using these devices, Bunsen was enabled to obtain even metallic calcium from a solution of its chloride. By the density of the current we mean the number of am- peres passing through each unit of surface of cathode or de- positing surface. If the density is very great, it is necessary that a brisk circulation be kept up in the solution to bring fresh quantities of salt into the sphere of action and to remove the impoverished solution ; otherwise, if a deficiency of salt occurs, the solvent is attacked. Rapid circulation therefore favors regular working. In any electrolytic bath, the tension and density of the cur- rent determine which of the several ingredients present will be 2,06 ALUMINIUM. decomposed. Let us assume two compounds present, A and B, of which ^ is a weaker compound than By either one of them may be water, or they may both be anhydrous salts. In such a liquid bath, a current just strong enough to decompose A will not afifect B. When the current is just strong enough to decompose B, the product will be the elements of A with a trace of those of B/ but since the base in B is supposed to be a stronger one than that in A, there will be a secondary action, and the base of B will displace the base of A in the still unde- composed compound, and B will be re-formed. This will be the direct effect of increasing the tension of the current. How- ever, if the density of the current is increased at the same time, another principle comes into play. The base of B may be de- posited so quickly that it has not time to react on A, and in that case the deposit will contain the base of B. Also, if there is a much larger proportion of B than of A present, a larger proportion of its base will be deposited than before and escape re-solution. Also, other things being equal, if the compound B is more fluid or rather diffuses quicker in the bath than A, more of it will get to the electrodes and a larger proportion be decomposed. We therefore see that when two or more compounds are present, the relative amounts of each to be decomposed depend 1. Primarily, on the electro-motive force of the current, which may be so regulated as to decompose them one after the " other in the order of their electromotive force of decomposition. 2. On the density of the current at the electrodes. That is, provided the tension of the current is sufficient to decompose the stronger compound, the greater the density of the current the greater the proportion of the stronger compound which will be decomposed, other conditions being equal. 3. On the relative amounts of each present. Other condi- tions being equal, the relative amount of a compound decom- posed will increase as its proportion in the bath is increased. 4. On the relative rates of diffusion, or the rapidity with which elements of the different compounds move towards the electrodes. REDUCTION OF ALUMINIUM COMPOUNDS. 307 The consideration of the electrolytic processes falls naturally under two heads : — I. Deposition from aqueous solution. II. Non-aqueous electric processes. I. Deposition of Aluminium from Aqueovs Solution. The status of this question is one of the curiosities of electro- metallurgic science. Evidently attracted by the great reward to be earned by success, many experimenters have labored in this field, have recommended all sorts of processes, and pat- ented all kinds of methods. We have inventors afiSrming in the strongest manner the successful working of their methods, while other experimenters have followed these recipes, and tried almost every conceivable arrangement, yet report negative results. To show that it is quite possible that many strong af- firmations may be made in good faith, I have only to mention the fact that in March, 1863, Mr. George Gore described in the Philosophical Magazine some experiments by which he de- posited coatings of aluminium from aqueous solutions, and afterwards, in his text book of Electro-metallurgy, asserts that he knows of no successful method of doing this thing. We infer that Mr. Gore found that he was in error the first time. So, if we take the position that aluminium cannot by any methods so far advanced be deposited from aqueous solution without using a soluble aluminium anode, we will have to ad- mit that the proposers of many of the following processes are probably misled by their enthusiasm in affirming so strongly that they can do this thing. Yet the problem is not impossible of solution. Messrs. Thomas and Tilly* coat metals with aluminium and its alloys by using a galvanic current and a solution of freshly precipitated alumina dissolved in boihng water containing po- tassium cyanide, or a solution of freshly calcined alum in * English Patent, 1855, No. 2756. 308 ALUMINIUM. aqueous potassium cyanide; also from several other liquids. Their patent covers the deposition of the alloys of aluminium with silver, tin, copper, iron, silver and copper, silver, and tin, etc. etc., the positive electrode being of this metal or alloy. M. Corbelli, of Florence,* deposits aluminium by electroylz- ing a mixture of rock alum or sulphate of alumina (2 parts) with calcium chloride or sodium chloride (i part) in aqueous solution (7 parts), the anode being mercury placed at the bottom of the solution and connected to the battery by an iron wire coated with insulating material and dipping its uncovered end into the mercury. The zinc cathode is immersed in the solution. Aluminium is deposited on the zinc, as a blackish powder or as a thin, compact sheet, and the chlorine which is liberated at the anode unites with the mercury, forming calomel. J. B. Thompsonf reports that he has for over two years been depositing aluminium on iron, steel, and other metals, and driving it into their surfaces at a heat of 500° F., and also de- positing aluminium bronze of various tints, but declines to state his process. George Gore, Jthe noted electrician, recommended the fol- lowing procedure for depositing aluminium on copper, brass, or German silver: — " Take equal measures of sulphuric acid and water, or one part sulphuric acid, one part hydrochloric acid and two parts of water, put into it half an ounce of pipe clay to the pint of dilute acid, and boil for an hour. Take the clear, hot liquid and immerse in it an earthen porous cell containing sulphuric acid diluted with ten times its bulk of water, together with a rod or plate of amalgamated zinc. Connect the zinc with the positive wire of a Smee battery of three or four elements con- nected for intensity. The article to be coated, well cleaned, is connected with the negative pole and immersed in the hot clay solution. In a few minutes a fine, white deposit of aluminium * English Patent, 1858, No. 507. fChem. News, xxiv. 194 (1871). t Philosophical Magazine, March, 1863. REDUCTION OF ALUMINIUM COMPOUNDS. 309 will appear all over its surface. It may then be taken out, washed quickly in clean water, wiped dry, and polished. If a thicker coating is required, it must be taken out as soon as the deposit becomes dull, washed, dried, polished, and re-immersed, and this must be repeated at intervals as often as it becomes dull, until the required thickness is obtained. It is necessary to have the acid well saturated by boiling, or no deposit will be obtained." Mierzinski asserts that Dr. Gore was mistaken when he sup- posed this deposit to be aluminium, and in Gore's Text Book of Electro-metallurgy no mention is made of these experi- ments, the author thereby acknowledging the error. As to what the deposit could have been, we are left to conjecture, since no explanation has been advanced by Dr. Gore ; it may possibly have been silicon, mercury, or zinc, as all three of these were present besides aluminium. J. A. Jeanfon* has patented a process for depositing alumin- ium from an aqueous solution of a double salt of aluminium and potassium of specific gravity 1.161 ; or from any solution of an aluminium salt, such as sulphate, nitrate, cyanide, etc., concentrated to 20° B. at 50° F. He uses a battery of four pairs of Smee's or three Bunsen's cells, with elements arranged for intensity, and electrolyzes the solutions at 140° F. The first solution will decompose without an aluminium anode, but the others require such an anode on the negative pole. The solution must be acidulated slightly with acid corresponding to the salt used, the temperature being kept at 140° F. constantly. More recently!, Jeangon has obtained a patent for the fol- lowing process : " Subjecting a supersaturated acid solution of a salt of aluminium to the action of a current passed from an anode of aluminium in a state of division or porosity, pre- senting a relatively large exposure of surface within a given field of electric force, and a suitable metallic cathode." Further * Annual Record of Science and Industry, 1875. tU. S. Patent, 436,895; Sept. 23, i8go. (Specimens.) 3IO ALUMINIUM. details state that the anode is to be prepared by melting alu- minium iri a crucible and stirring in about 30 per cent, of car- bon or a similar substance, and then moulding into shape. The electrolyte is to be maintained at a high temperature, preferably 180° to 200° F., under which conditions a dense deposit is obtained. The writer has already stated that aluminium is being suc- cessfully electro-plated from solution using aluminium anodes; and, if the above process is the one which has been used in Philadelphia by the Harvey Filley Plating Co., then I can cer- tify to it having been successfully operated. The company mentioned refuse to say anything about the process they use, but I have been informed by outside parties that the above is the one. It is certain, however, that very good specimens of aluminium-plated ware have been made and sold by this firm, several having been examined and tested by the writer person- ally. A thin deposit on sheet-iron, which has been in my pos- session over two years, shows no sign of rust or deterioration, and suggests the practicability of thus making a substitute for tin-plate of greater durability and which will not rust. M. A. Bertrand * states that he deposited aluminium on a plate of copper from a solution of double chloride of aluminium and ammonia, by using a strong current, and the deposit was capable of receiving a brilliant polish. Jas. S. Haurd,t of Springfield, Mass., patented the elec- trolysis of an aqueous solution formed by dissolving cryolite in a solution of magnesium and manganous chlorides. John Braun { decomposes a solution of alum, of specific gravity 1.03 to 1.07, at the usual temperature, using an insolu- ble anode. In the course of the operation, the sulphuric acid set free is neutralized by the continual addition of alkali ; and, afterwards, to avoid the precipitation of alumina, a non-volatile organic acid, such as tartaric, is added to the solution. The * Chem. News, xxiv. 227. t U. S. Patent, 228,900, June 15, 1880. X German Patent, No. 28,760 (1883'!. REDUCTION OF ALUMINIUM COMPOUNDS. 3 II intensity of the current is to be so regulated that for a bath of lO to 20 Htres two Bunsen elements (about 20 centimetres high) are used. Dr. Fred. Fischer* stated that Braun's proposition was con- trary to his experience. By passing a current of 8 to 9 volts and 50 amperes, using from o.i to 10 amperes per sq. centi- metre of cathode, with various neutral and basic aluminium sulphate solutions, with and without organic acids, he obtained no aluminium. He obtained a black deposit of copper sul- phide on the copper anode, which had apparently been mis- taken by Braun for aluminium. Moses G. Farmer | has patented an apparatus for obtaining aluminium electrically, consisting of a series of conducting cells in the form of ladles, each ladle having a handle of conducting material extending upwards above the bowl of the next suc- ceeding ladle ; each ladle can be heated separately from the rest ; the anodes are hung in the ladles, being suspended from the handles of the preceding ladles, the ladles themselves being the cathodes. M. L. Senet X electrolyzes a saturated solution of aluminium sulphate, separated by a porous septum from a solution of sodium chloride. A current is used of 6 to 7 volts and 4 amperes. The double chloride, AlCl'.NaCl, is formed, then decomposed, and the aluminium liberated deposited on the negative electrode. It has later been remarked of this process that it has not had the wished-for success on a large scale. Col. Frismuth, of Philadelphia, purported to plate an alloy of nickel and aluminium. He used an ammoniacal solution, prob- ably of their sulphates. The plating certainly resembled nickel, but that it contained aluminium the writer is not pre- pared to assert. Baron Overbeck and H. Neiwerth, of Hannover, § have * Zeitschrift des Vereins Deutsche Ingenieurs, 1884, p. 557. t U. S. Patent, No. 315,266, April, 1885. t Cosmos les Mondes, Aug. 10, 1885. § English Pat., Dec. 15, 1883, No. 5756: 3 1 2 ALUMINIUM. patented the following process : An aqueous or other solu- tion of an organic salt of aluminium is used, or a mixture of solutions which by double decomposition will yield such salt. Or a mixture of a metallic chloride and aluminium sulphate may be used, this yielding nascent aluminium chloride, which the current splits up immediately into aluminium and chlorine. Herman Reinbold* gives the following recipe, stating that it furnishes excellent results : 50 parts of potash alum are dis- solved in 300 parts of water, and to this are added 10 parts of aluminium chloride. The whole is then heated to 200° F., cooled, and then 39 parts of potassium cyanide added. A weak current should be used. It is stated that the plating, when polished, will be found equal to the best silver plating. " Iron," noticing this process, remarks, " there are a number of formulae for electro-plating with aluminium, but few appear to have attained to practical utility in the arts, for the reason that there is no special demand for such processes. All the quali- ties that are possessed by an electro-deposit of aluminium are possessed to an equal or superior degree by other metals, silver, nickel, platinum, etc. Furthermore, it obstinately refuses to take and to retain a high lustre." This criticism is a little overdrawn, since the one quality in which aluminium is super- ior to silver — not blackening by contact with sulphurous vapor — is not mentioned. Under the name of Count R. de Montegelas, of Philadelphia, several patents have been taken out in England for the elec- trolysis of aqueous solutions, which may be summarized as follows : — f Alumina is treated with hydrochloric acid, and aluminium chloride obtained in solution. The liquid is then placed in a vessel into which dip a suitable anode and a cathode of brass or copper. On passing an electric current through the bath the iron present in the liquid is first deposited, and as soon as this deposition ceases (as is apparent by the change of color of the * Jeweler's Journal, September, 1887. t English Patent, Aug. 18, 1886, No. 10607. REDUCTION OF ALUMINIUM COMPOUNDS. 313 deposit) the liquid is decanted into another similar bath, and to it is added about fifty per cent, by weight of the oxide of either lead, tin or zinc. On sending a current through this bath, aluminium together with the metal of the added oxide is said to be deposited on the cathode. * A rectangular vessel is divided into two unequal compart- ments by a vertical porous partition, into the smaller of which is placed a saturated solution of common salt, in which is im- mersed a brass or copper electrode ; into the larger is put a so- lution of aluminium chloride, immersed in which is an alumin- ium electrode. On passing the current the latter solution, which is normally yellow, is gradually decolorized and con- verted into a solution of aluminium-sodium chloride. When colorless, this solution is taken out and the aluminium deposited in a similarly arranged vessel. The double chloride solution is placed in the larger compartment, with an electrode of brass, copper, or a thin plate of aluminium, while the smaller com- partment contains a carbon electrode dipping into a solution of salt and surrounded by fragments of a mixture of salt and double chloride, fused together in equal parts. The author has been given several ounces of a very fine me- tallic powder said to have been made by these processes, and which is certainly aluminium. As I am not satisfied, however, that the specimen is really authentic, I feel justified in suspend- ing a final expression of opinion on the process. A Walker, of Tarnowitz, has patented the following methods of procedure : j a. Pure commercial hydrate is dissolved in nitric acid free from chlorine, in slight excess, and tartaric acid added. The Hquid is let clear for some time, any potassium bi-tartrate, which may be formed from small quantities of potassium ad- hering to the hydrate, filtered out, and the clear solution electrolyzed. There is added to the solution during electrolysis * English Patent, Feb. 3, 1887, No. 1751. t German Pat. (D. R. P.) 40,626 (1887). 3 1 4 ALUMINIUM. organic acid — as formic, acetic, citric, oxalic — or, better, ab- solute alcohol. b. A solution of aluminium nitrate, as far as possible free from alkalies and sulphuric acid, is decomposed by a strong dynamic current in baths arranged in series, using platinized plates as anode and cathode. With a weak current of 0.02 to 0.05 amperes to a square centimetre, the aluminium separates out on the cathode as a deep black deposit, sticking close to the copper. The cathode is lifted from the solution, freed from small quantities of alumina coating it by gentle rinsing, and then the deposit washed off by a strong jet of water. The powder obtained is washed further with clear, cold water, par- ticularly free from sodium chloride, and dried by gentle heat- ing in the air. H. C. Bull* proposes to manufacture aluminium alloys by using the metal to be alloyed with aluminium as a cathode in a bath of aluminium sulphate, the anode being either of alumin- ium or of an insoluble substance. When enough aluminium is deposited, the cathode is taken out and melted down. C. A. Burghardt and W. J. Twining, of Manchester, England, have patented the following methods : fTo a solution of sodium or potassium aluminate containing about 7.2 oz. of aluminium per gallon are added 4 pounds of 95 per cent, potassium cyanide dissolved in a quart of water, and then gradually 2j^ pounds of potassium bi-carbonate. The whole is boiled 12 hours and made up to a gallon. The bath is used at 175° F. with aluminium or platinum anode and carbon or copper cathode. The addition of a little free hydro- cyanic acid insures a bright deposit when articles are being plated. % Two and one-half kilos of aluminium sulphate in solution is precipitated by ammonia, and then re-dissolved by adding \yi kilos of caustic soda dissolved in a litre of water; the alumina ♦English Pat., 10,199 A. (1887). t English Pat., July 2, 1887, No. 9389. I German Pat. (D. R. P.), 45,020 (1887). REDUCTION OF ALUMINIUM COMPOUNDS. 3x5 is thus slightly in excess. The hydrocyanic acid is added until a slight precipitate appears. This solution, warmed to 80°, is used as a bath from which aluminium is to be deposited. *The bath is prepared by dissolving alumina in a solution of chloride of copper, and treating further with caustic soda or potash for the purpose of causing the aluminium and copper to combine together. The precipitate, dissolved in hydrocyanic acid and diluted, forms a bath of double cyanide, which when electrolyzed deposits an alloy of aluminium and copper. Besides the processes so far described, patents have been taken out in England by Gerhard and Smith,f Taylor,| and Coulson,§ the details of which have not been accessible to the author. Over against these statements of enthusiastic inventors, let me place a few extracts from authorities who have given much time and attention to the subject of electro-depositing alumin- ium from solution without the use of an aluminium anode. Sprague|| states his inability to deposit aluminium electric- ally from solution. Dr. Clemens Winckler IT states that he has spent much time in trying all methods so far proposed, and comes to the conclu- sion that aluminium cannot be deposited by electricity in the wet way. Dr. Geo. Gore** although having once proposed a method which he said attained this end, yet in his later work on Elec- tro-metallurgy does not mention his former proposition, and quotes, apparently as coinciding with his own opinion, the words of Sprague and Winckler given above. * English Pat., Oct. 28, 1887, No. 2602. tNo. 16,653 (1884). J No. 1991 (1855). § No. 207s (1857). II Sprague's Electricity, p. 309. t Journal of the Chem. Soc, X. 1 134. ** Text-book of Electto- metallurgy. 3l6 ALUMINIUM. Dr. S. Mierzinski* states, in 1883, that "the deposition of aluminium from an aqueous solution of its salt has not yet been accomplished." Dr. W. Hampef claims to have shown that the electrolysis of aqueous aluminous solutions, although frequently patented, is not to be expected. From which we would infer that he could not testify to it ever having been done. Alexander Watt| holds that the electrolytic production of aluminium ,from solution is very improbable. He tried acid solutions, alkaline solutions, cyanide combinations, etc., under most varied conditions, without any result. Finally, I will quote from a letter of my good friend Dr. Justin D. Lisle, of Springfield, O., who with ample means at his disposal, an enthusiasm bred of love tor scientific truth, and talent to guide him in his work, has reached the following re- sults : " I have tried in almost every conceivable way to de- posit it (aluminium) from aqueous solution by electricity, using from i pint cells to 60 gallon cells successively ; the cells were connected for quantity and for intensity; acid and neutral solutions were used; carbon, platinum, and copper electrodes, porous cups and diaphragms, were all thoroughly tried, without the slightest deposit of metal. In some cases alumina was de- posited, which has led me to think that aluminium was pri- marily deposited, and owing to the fine state in which it existed was promptly oxidized." The following details of the operation of the electric plant of the Tacony Metal Company, near Philadelphia, under the supervision of Mr. J. D. Darling, are all that the writer has been able to gather respecting their process. This company had the contract to electroplate the exterior ironwork of the tower of the Philadelphia Public Buildings, there being alto- gether about 50,000 square feet to be plated, on which was to be deposited 20,000 pounds of aluminium, or a little over six * Die Fabrikation des Aluminiums. tChem. Zeit. (Cothen), XI. 935. I London Electrical Review, July, 1887. REDUCTION OF ALUMINIUM COMPOUNDS. 317 ounces to the foot. This would give a smooth coating j\ inch thick. The cast-iron work is first given a coating of copper, and the aluminium deposited on it, but it is stated that good platings have been obtained directly on the cast-iron. The largest pieces plated were columns 26 feet long and 3 feet in diameter. The whole operation of treating such a col- umn lasted 1 1 days, while the plant could turn out one every 4 days. The operations were as follows : (i) Boiling 24 hours in a strong solution of caustic soda, after which well washed. (2) Pickled in dilute sulphuric acid 24 hours, brushed vig- orously and washed. (3) Copper-plated by immersion 40 hours in a copper cyanide(?) solution. The column was then brushed with par- affine wax inside, any flaws soldered up, and — (4) Copper-plated again in an ordinary copper-plating so- lution for 72 hours, until 16 ounces of copper to the square foot had been deposited. (5 ) Put into the aluminium-plating tank, and 3 ounces of aluminium per square foot deposited on it. Time, 72 hours. Column then well washed in the sixth tank. The dynamo used for operation 3 gives a current of 1000 amperes at 6 volts tension ; for operation 4, 4000 amperes at 2.5 volts tension; for operation 5, 2000 amperes at 8 volts tension. In the latter case, the current density at the depos- iting surface was 8 amperes per square foot (86 amperes per square metre). In this depositing tank, aluminium anodes 4 feet long, 12 inches wide and }( inch thick were used. Sixty of these plates, weighing 35 pounds each, were hung around the inside of the tank. ■ The company will give no information regarding the compo- sition of the electrolyte. Concerning the conducting of thS operation, Mr. Darling has stated that " Aluminium is more difficult to deposit than any of the common metals, because of its tendency to re-dissolve after being deposited. I find that by using a solution of aluminium salt that has but a slight dis- 3l8 ALUMINIUM. solving effect on aluminium, with a density of current of 8 amperes per square foot, and with sufficiently high voltage, aluminium can be deposited at the rate of i gramme per hour per square foot in a reguline state. With much higher cur- rents it can be deposited quicker, but will be in a pulverulent state, which does not adhere." II. Non-aqueous Electric Processes. The above heading was originally written, "The electrolytic decomposition of fused aluminium compounds," but I have changed it to this form because it is doubtful, in several cases, whether electrolytic decomposition really plays much of a role in the isolation of the aluminium. In some processes a pow- erful current is used and largely converted into heat, producing temperatures never before used in industrial operations. In such cases, chemical reactions, rendered possible by the very high temperature, come into play and may even be the prin- cipal means of reducing the aluminium compound. It has been suggested that such processes should be classed apart as "electro-thermal methods;" but such a division does not ap- pear satisfactory to me, because in most cases we cannot say positively that electrolysis does not play some part, and in others it is simply impossible to decide which of the two agents of reduction, electrolysis or chemical affinity, is the most active. It has been suggested also that those processes in which high voltage is used cannot be electrolytic, but must be electro-ther- mal ; but such a division is not logical. If a bath is taking a high voltage to work it, it may be solely from poor conductivity in the electrolyte, and not because an arc is formed in the bath, and true electrolysis may be going on to the full extent of the power of the current. If we knew definitely, for each process, which action played the principal part in the reduction, we might classify the processes, but such a classification would not be of much use. If it was absolutely necessary to make some REDUCTION OF ALUMINIUM COMPOUNDS. 319 such division, I should consider as electro-thermal those pro- cesses in which the parts of the apparatus used are not ar- ranged as they should be to secure the maximum electrolytic decomposition. We could thus, in such cases, say at once, from a consideration of the apparatus and its manner of work- ing, that electrolysis was evidently not contemplated in its con- struction and could only play a minor part in its operation. In conclusion, I regard it impossible to make an exact clas- sification of these processes such as would be of any value to the metallurgist or aid the general reader to a better under- standing of them, and I therefore take them up in chronolog- ical order. Davy's Experiment (1810). Sir Humphry Davy, in his Brompton Lecture before the Royal Philosophical Society,* described the following attempt to decompose alumina and obtain the metal of this earth. He connected an iron wire with the negative pole of a battery con- sisting of 1000 double plates. The wire was heated to white- ness and then fused in contact with some moistened alumina, the operation being performed in an atmosphere of hydrogen. The iron became brittle, whiter, and on being dissolved in acid gave a solution from which was precipitated alumina, identical with that used. It is evident that the alumina had been reduced by the chemical action of the hydrogen gas, a reaction which we now know takes place below the fusing point of alumina, 2200°, and probably begins as low as 1700°. Duvivier's Experiment (1854). M. Duvivier f states that by passing an electric current from eighty Bunsen cells through a small piece of laminated disthene between two carbon points, the disthene melted entirely in two or three minutes ; the elements which composed it were partly * Philosophical Transactions, 1810. fThe Chemist, Aug., 1854. 320 ALUMINIUM. disunited by the power of the electric current, and some alu- minium freed from its oxygen. Several globules of the metal separated, one of which was as white and as hard as silver. Since disthene is aluminium silicate, formula Al^Os.SiOj, it is most likely that the metal obtained was highly siliceous aluminium, since complete reduction of this compound would give 54 parts of aluminium to 28 parts of silicon. The highly- heated carbon particles of the electric arc were most probably the reducing agent. Bunsen's and Deville's Methods (1854). A method of decomposing aluminium-sodium chloride by the battery was discovered simultaneously by Deville in France and Bunsen in Germany, in 1854, and is nothing else but an appli- cation of the process already announced by Bunsen of decom- posing magnesium chloride by the battery. Deville gives the more minute account, and we therefore quote his description of the process. f " It appears to me impossible to obtain aluminium by the battery in aqueous solutions. I should believe this to be an absolute impossibility if the brilliant experiments of M. Bunsen in the preparation of barium, chromium and manganese did not shake my convictions. Still I must say that all the processes of this description which have recently been published for the preparation of aluminium have failed to give me any results. Every one knows the elegant process by means of which M. Bunsen has lately produced magnesium, decomposing fused mag- nesium chloride by an electric current. The illustrious profes- sor at Heidelberg has opened up a method which may lead to very interesting results. However, the battery cannot be used for decomposing aluminium chloride directly, which does not melt, but volatilizes at a low temperature ; it is, therefore, neces- sary to use some other material which is fusible and in which *Tbe Chemist, Aug. 1854. t Ann. de Chem. et de Phys. [3], 46, 452; Deville's " de rAluminium." REDUCTION OF ALUMINIUM COMPOUNDS. 321 aluminium alone will be displaced by the current. I have found this salt in the double chloride of aluminium and sodium, which melts towards 185° C, is fixed at a somewhat high temperature, although volatile below the fusing point of aluminium, and thus unites all the desirable conditions. " I put some of this double chloride into a porcelain crucible separated imperfectly into two compartments by a thin leaf of porcelain, and decomposed it by means of a battery of five ele- ments and carbon electrodes. The crucible was heated more and more as the operation progressed, for the contents became less and less fusible, but the heat was not carried past the melt- ing point of aluminium. Arrived at this point, after having lifted out the diaphragm and electrodes, I heated the crucible to bright redness, and found at the bottom a button of alumin- ium, which was flattened out and shown to the Academy in the S6ance of March 20, 1854. The button was accompanied by a considerable quantity of carbon, which prevented the union of a considerable mass of shot-metal. This carbon came from the disintegration of the very dense gas-retort carbon electrodes; in fact, the positive electrode was entirely eaten away in spite of its considerable thickness. It was evident, then, that this appa- ratus, although similar to that adopted by Bunsen for manufac- turing magnesium, would not suit here, and the following is the process which after many experiments I hold as best. " To prepare the bath for decomposition, I heat a mixture of 2 parts aluminium chloride and i part sodium chloride, dry and pulverized, to about 200° in a porcelain capsule. They com- bine with disengagement of heat, and the resulting bath is very fluid. The apparatus which I use for the decomposition com- prises a glazed porcelain crucible, which as a precaution is placed inside a larger one of clay. The whole is covered by a porcelain cover pierced by a slit to give passage to a large thick leaf of platinum, which serves as the negative electrode ; the lid has also a hole through which is introduced, fitting closely, a well-dried porous cylinder, the bottom of which is kept at some distance from the inside of the porcelain crucible. This porous 322 ALUMINIUM. vessel encloses a pencil of retort carbon, which serves as the positive electrode. Melted double chloride is poured into the porous jar and into the crucible so as to stand at the same height in both vessels ; the whole is heated just enough to keep the bath in fusion, and there is passed through it the current from several Bunsen cells, two cells being strictly sufficient. The annexed diagram shows the crucibles in section. Fig. 28. "The aluminium deposits with some sodium chloride on the platinum leaf; the chlorine, with a little aluminium chloride, is disengaged in the porous jar and forms white fumes, which are prevented from rising by throwing into the jar from time to time some dry, pulverized sodium chloride. To collect the aluminium, the platinum leaf is removed when sufficiently charged with the saline and metallic deposit; after letting it cool, the deposit is rubbed off and the leaf placed in its former position. The material thus detached, melted in a porcelain crucible, and after cooling washed with water, yields a gray, metallic powder, which by melting several times under a layer of the double chloride is reunited into a button." Bunsen* adopted a similar arrangement. The porcelain cru- * Pogg. Annalen, 97, 648. REDUCTION OF ALUMINIUM COMPOUNDS. 323 cible containing the bath of aluminium-sodium chloride kept in fusion was divided into two compartments in its upper part by a partition, in order to separate the chlorine liberated from the alu- minium reduced. He made the two electrodes of retort carbon. To reunite the pulverulent aluminium, Bunsen melted it in a bath of the double chloride, continually throwing in enough sodium chloride to keep the temperature of the bath about the fusing point of silver. As we have seen, Deville, without being acquainted with Bun- sen's investigations, employed the same arrangement, but he abandoned it because the retort carbon slowly disintegrated in the bath, and a considerable quantity of double chloride was lost by the higher heat necessary to reunite the globules of alumin- ium after the electrolysis. Deville also observed that by working at a higher temperature, as Bunsen had done, he obtained purer metal, but in less quantity. The effect of the high heat is that silicon chloride is formed and volatilizes, and the iron which would have been reduced with the aluminium is transformed into ferrous chloride by the aluminium chloride, and thus the aluminium is purified of silicon and iron. Plating aluminium on copper. — The same bath of double chlor- ide of aluminium and sodium may be used for plating alumin- ium in particular on copper, on which Capt. Caron experimented with Deville. Deville says : " To succeed well, it is necessary to use a bath of double chloride which has been entirely purified from foreign metallic matter by the action of the battery itself. When aluminium is being deposited at the negative pole, the first portions of metal obtained are always brittle, the impurities in the bath being removed in the first metal thrown down; so, when the metal deposited appears pure, the piece of copper to be plated is attached to this pole and a bar of pure aluminium to the positive pole. However, a compact mixture of carbon and alumina can be used instead of the aluminium anode, which acts similarly to it and keeps the composition of the bath con- stant. The temperature ought to be kept a little lower than the fusing point of aluminium. The deposit takes place readily 324 ALUMINIUM. and is very adherent, but it is difficult to prevent it being im- pregnated with double chloride, which attacks it the moment the piece is washed. The washing ought to be done in a large quantity of water Cryolite might equally as well be used for this operation, but its fiisibility should be increased by mixing with it a little double chloride of aluminium and sodium and some potassium chloride." During a recent law-suit for infringement of the Hall process, it was held by the defendants that Deville electrolyzed a fluoride bath, (cryolite) in which alumina was present and therefore would be dissolved. It appears quite evident, however, that Deville did not use cryolite, because it would have destroyed the porcelain crucibles and necessitated the use of special ap- paratus which Deville does not even hint at. It is, moreover, true that when alumina is mixed with carbon the latter prevents the cryoHte from wetting or coming into actual contact with it. In an experiment by the writer, a large cylinder of carbon into which had been incorporated over 50 per cent, of alumina was kept in molten cryolite for several hours, and on being taken out showed not the slightest sign of corrosion. Judges Taft and Ricks of Ohio very properly ruled that Deville's ex- periments did not in any way disclose or operate on the princi- ple utilized by Mr. Hall. Le Chatellier's Method (1861). The subject of this patent* was the decomposition of the fused double chloride of aluminium and sodium, with the par- ticular object of coating or plating other metals, the articles being attached to the negative pole. About the only novelty claimed in this patent was the use of a mixture of alumina and carbon for the anode, but we see from the previous paragraph that this was suggested by Deville several years before ; the only real improvement was the placing of this anode inside a porous cup, in order to prevent the disintegrated carbon from * English Patent, 1861, No. 1214. REDUCTION OF ALUMINIUM COMPOUNDS. 325 falling into the bath. This was really only the Deville process, patented in England. Monckton's Patent (1862). Monckton* proposes to pass an electric current through a reduction chamber, and in this way to raise the temperature to such a point that alumina will be reduced by the carbon present. We clearly see in this the germ of several more- recently patented processes. Gaudin's Process (1869). Gaudin f reduces aluminium by a process to which he ap- plies the somewhat doubtful title of economic. He melts to- gether equal parts of cryolite and sodium chloride, and traverses the fused mass by a galvanic current. Fluorine is evolved at the positive pole, while aluminium accumulates at the negative. The great difficulties in such a process are the obtaining of suitable vessels to withstand the corrosion of the bath, the great inconvenience of the escaping fluoride gas, and the increase of resistance due to the change of composition of the bath. It would need several additional patents to render this process operative, without mentioning economy. Kagensbusch' s Process (1872). Kagensbusch,! of Leeds, proposes to melt clay with fluxes, then adding zinc or a like metal to pass an electric current through the fused mass, isolating an alloy of aluminium and the metal, from which the foreign metal may be removed by distillation, sublimation, or cupellation. If the patentee had used pure alumina instead of clay, he might have produced some aluminium by his process, but the silicon in the clay would get into the zinc in larger proportion * English Patent, 1862, No. 264. t Moniteur Scientifique, xi., 62. X English Patent, 1872, No. 481 1. 326 ALUMINIUM. than the aluminium, rendering the succeeding operations for obtaining pure aluminium impossible. Berthaut's Proposition (1879). Up to this time all the proposed electric processes were confined to the use of a galvanic current, the cost of obtaining which was a summary bar to all ideas of economical produc- tion. About this period dynamo-electric machines were being introduced into metallurgical practice, and Berthaut is the first we can find who proposes their use in producing aluminium. The process which he patented * is otherwise almost identical with Le Chatellier's, Grdtzel's Process (1883). This process f has little claim to originality, except in the details of the apparatus. A dynamo-electric current is used, the electrolyte is fused cryolite or double chloride of aluminium and sodium, and the anodes are of pressed carbon and alumina — none of which points are new. However, the use of melting pots of porcelain, alumina, or aluminium, and making them the negative electrode, are points in which innovations are made. In a furnace are put two to five pots, according to the power of the dynamo used, each pot having a separate grate. The pots are preferably of metal, cast-steel is used, and form the negative electrodes. The positive electrode, K (Fig. 29), can be made of a mixture of anhydrous alumina and carbon pressed into shape and ignited. A mixture of alumina and gas-tar answers very well ; or it can even be made of gas-tar and gas- retort carbon. During the operation little pieces of carbon fall from it and would contaminate the bath, but are kept from doing so by the mantle G. This isolated vessel, G, is perforated around the lower part at g, so that the molten electrolyte may circulate through. The tube O' conducts reducing gas into the * English Patent, 1879, No. 4087. t German Patent (D. R. P.), No. 26962 (1883). REDUCTION OF ALUMINIUM COMPOUNDS. 327 crucible, which leaves by the tube 0\ This reducing atmos- phere is important, in order to protect from burning any metal rising to the surface of the bath. The chlorine set free at the electrode, K, partly combines with the alumina in it, regenera- ting the bath, but some escapes, and, collecting in the upper part of the surrounding mantle, G, is led away by a tube con- FlG. 29. necting with it. Instead of making the electrode K of carbon and alumina, it may simply be of carbon, and then plates of pressed alumina and carbon are placed in the bath close to the electrode, K, but not connected with it. Also, in place of making the crucible of metal and connecting it with the nega- tive pole, it may be made of a non-conducting material, clay or the like, and a metallic electrode — as, for instance, of alu- minium — plunged into the bath. In a later patent,* Gratzel states that the bath is decomposed * English Patent; 14325, Nov. 23, 1885. U. S. Patent, 362441, May 3, 1887. 328 ALUMINIUM. by a current of comparatively low tension if magnesium chloride be present ; the chlorides of barium, strontium or calcium act similarly. Prof. F. Fischer* maintains as impracticable the use of plates of pressed alumina and carbon, which can, further, only be operative when they are made the positive electrode, and then their electric resistance is too great. The incorporation into them of copper filings, saturation with mercury, etc., give no more practical results. There are also volatilized at the anodes considerable quantities of aluminium chloride, varying in amount with the strength of the current. Large works were erected near Bremen by the Aluminium und Magnesiumfabrik Pt. Gratzel, zu Hemelingen, in which this process was installed. License was also granted to the large chemical works of Schering, at Berlin, to operate it. R. Biedermann, in commenting on the process in i886,f stated that the results obtained so far were not fully satisfactory, but the difficulties which had been met were of a kind which would certainly be overcome. They were principally in the polariza- tion of the cathode, by which a large part of the current was neutralized. By using proper depolarizing substances this dif- ficulty would be removed. The utilization of the chlorine evolved would also very much decrease the expenses. A more suitable slag, which collected the aluminium together better, was also desirable. Finally, the metal produced was somewhat impure, taking up iron from the iron pots and silicon from the clay ones, to obviate which Biedermann recommended the use of lime or magnesia vessels. Prof. Fischer, as we have seen, maintained the uselessness of Gratzel's patent claims, and his later expression of this opinion in 1887 drew a reply from A. Saarburger, Jdirectorof the works at Hemehngen, to the effect that since October, 1887, they had * Wagner's Jahresbericht, 1884, p. 1319; 1887, p. 376. fKerl und Stohman, 4th ed., p. 725. { Verein der Deutsche Ingenieure, Jan. 26, 1889. REDUCTION OF ALUMINIUM COMPOUNDS. 329 abandoned the Gratzel process, and were making aluminium at present by methods devised by Herr Saarburger; in conse- quence of which fact the directors of the company decided in January, 1888, to drop the addition Pt. Gratzel from the firm name. The methods then in use at Hemelingen were kept secret, but the author was informed by a friend in Hamburg that they were using a modified Deville sodium process. Herr Saarbur- ger informed me in October, 1888, that they were producing pure aluminiuin at the rate of 12 tons a year, besides a large quantity sold in alloys. An attractive pamphlet issued by this firm set forth precautions to be used in making aluminium alloys, together with a digest of their most important properties, which we shall have occasion to quote from later in considering those alloys. The sharp decline in the price of aluminium in 1890 forced this company out of the aluminium business. Cowles Bros! Process. Messrs. E. H. and A. H. Cowles patented in the United States and Europe * an electric furnace and its application for producing aluminium. Their patent claims " reducing an alu- minium compound in company with a metal in presence of car- bon in a furnace heated by electricity ; the alloy of aluminium and the metal formed being further treated to separate out the aluminium." The history of the development of this process having already been sketched, we will proceed to describe the details of its operation. The first public description was given in two papers, one read before the American Association for the Advancement of Science f by Prof. Chas. F. Mabery of the Case School of Applied Science, Cleveland, the other before the American Institute of Mining Engineers % by Dr. T. Sterry Hunt, of Montreal. * U. S. Patents 324658, 324659, Aug. 18, 1885; English Patent 9781, same date; German Patent 33672. t Ann Arbor Meeting, Aug. 28, 1885. X Halifax Meeting, Sept. 16, 1885. 330 ALUMINIUM. Prof. Mabery said in his paper : " Some time since, the Messrs. Cowles conceived the idea of obtaining a continuous high tem- perature on an extended scale by introducing into the path of an electric current some material that would afford the requi- site resistance, thereby producing a corresponding increase in the temperature. After numerous experiments, coarsely pul- verized carbon was selected as the best means for maintaining an invariable resistance, and at the same time as the most available substance for the reduction of oxides. When this material, mixed with the oxide to be reduced, was made a part of the electric circuit, inclosed in a fire-clay retort, and sub- jected to the action of a current from a powerful dynamo, not only was the oxide reduced, but the temperature increased to such an extent that the whole interior of the retort fused com- pletely. In other experiments lumps of lime, sand, and corun- dum were fused, with a reduction of the corresponding metal ; on cooling, the lime formed large, well-defined crystals, the corundum beautiful red-green and blue octahedral crystals. Following up these results, it was soon found that the intense heat thus produced could be utilized for the reduction of oxides in large quantities, and experiments were next tried on a large scale with the current from a fifty horse-power dyamo. For the protection of the walls of the furnace, which were of fire- brick, a mixture of ore and coarsely pulverized gas-carbon was made a central core, and was surrounded on the side and bot- tom by fine charcoal, the current following the lesser resistance of the core from carbon electrodes inserted in the ends of the furnace in contact with the core. The furnace was charged by first filling it with charcoal, making a trough in the centre, and filling this with the ore mixture, the whole being covered with a layer of coarse charcoal. The furnace was closed on top with fire-brick slabs containing tivo or three holes for the escape of the gaseous products of the reduction, and the whole furnace was made air-tight by luting with fire-clay. Within a few minutes after starting the dynamo, a stream of carbonic oxide issued through the openings, burning usually with a flame REDUCTION OF ALUMINIUM COMPOUNDS. 33 1 eighteen inches high. The time required for complete reduc- tion was ordinarily about an hour. Experience has already shown that aluminium, silicon, boron, manganese, sodium and potassium can be reduced from their oxides with ease. In fact, there is no oxide that can withstand the temperature attainable in this furnace. Charcoal is changed to graphite; does this indicate fusion? As to what can be accomplished by convert- ing enormous electrical energy into heat within narrow limits, it can only be said that it opens the way into an extensive field of pure and applied chemistry. It is not difficult to conceive of temperature limited only by the power of carbon to resist fusion. " Since the motive power is the chief expense in accomplish- ing reductions by this method, its commercial success is closely connected with obtaining power cheaply. Realizing the importance of this point, Messrs. Cowles have purchased at Lockport, N. Y., a water-power where they can utilize I200 horse-power. An important feature in the use of these furnaces from a commercial standpoint is the slight technical skill re- quired in their manipulation. The four furnaces operated in the experimental laboratory at Cleveland are in charge of two young men, who six months ago knew absolutely nothing of electricity. The products at present manufactured are the various grades of aluminium bronze, made from a rich furnace product obtained by adding copper to the charge of ore. Aluminium silver is also made ; and a boron bronze may be prepared by the reduction of boracic acid in contact with copper, while silicon bronze is made by reducing silica in con- tact with copper. As commercial results may be mentioned the production in the experimental laboratory, which averages 50 lbs. of 10 per cent, aluminium bronze daily, which can be supplied to the trade in large quantities on the basis of $5 per lb. for the aluminium contained, the lowest market quotation of aluminium being now $15 per lb." Dr. Hunt stated further that if the mixture consisted of alu- mina and carbon only, the reduced metal volatilized, part es- 332 ALUMINIUM. caping into the air and burning to alumina, part condensing in the upper layer of charcoal, affording thus crystalline masses of nearly pure aluminium and yellow crystals supposed to be a compound of aluminium with carbon. Great loss was met in collecting this divided metal into an ingot, so that only small quantities were really obtained. To gather all the aluminium together, a metal such as copper was added, thus producing an alloy with 15 to 20 per cent, of aluminium ; on substituting this alloy for pure copper in another operation, an alloy with over 30 per cent, of aluminium was obtained. Dr. Hunt, in a later paper,* stated that pure aluminium has been obtained in this process by first producing in the furnace an alloy of aluminium and tin, then melting this with lead, when the latter takes up the tin and sinks with it beneath the aluminium. He also stated that in the early experiments a dynamo driven by a 30 horse-power engine yielded a daily out- put of 50 lbs. of 10 per cent, aluminium bronze, but with a larger machine the output was proportionally much greater. In the latest practice, one-half cent per horse-power per hour is said to cover the expense of working, making the 10 per cent, bronze cost about 5 cents per lb. over the copper used. Various shapes of furnaces have been used by the Cowles Bros., the first described being a rectangular box, lined with carbon, with the electrodes passing through the ends. Al- though two other forms have been patented, we understand that the kind now used, aad which is described at length in Mr. Thompson's paper, is also of the oblong, horizontal style. Chas. S. Bradley and Francis B. Crocker, of New York, patented and assigned to the Cowles Electric Smelting Company,f the use of a retort, composed of conducting material, surrounded by a substance which is a poor conductor of heat, and having inside a mixture of charcoal and the ore to be heated. Electric connection being made with the ends of the retort, the walls of ♦National Academy of Science, Washington Meeting, April 30, 1886. tU. S. Patent 335499, Feb. j., 1886. REDUCTION OF ALUMINIUM COMPOUNDS. 333 the retort and the material in it are included in the circuit and constitute the greater part of the resistance. The retort may be stoppered at each end during the operation, and the heating thus performed in a reducing atmosphere. Mr. A. H. Cowles devised a style of furnace adapted for continuous working and utilizing the full current of a dynamo of the largest size.f The electrodes are tube-shaped and placed vertically. The positive pole is above, and is surmounted by a funnel in which the mixture for reduction is placed. The regular delivery of the mixture is facilitated by a carbon rod, passing through the cover of the funnel, which is serrated on the end and can be worked up and down. The melted alloy produced, with any slag, passes down through the negative electrode. The dis- tance between the poles can be regulated by moving the upper one, and the whole is inclosed in a fire-brick chamber. The space between the electrodes and the walls is filled with an iso- lating material, which is compact around the lower electrode but coarse grained around the upper to facilitate the escape of the gases produced. The chamber is tightly closed excepting a small tube for the escape of gas. A very complete description of the Cowles process was given by Mr, W. P. Thompson (agent for the Cowles Co. in England) in a paper read before the Liverpool Section of the Society of Chemical Industry. f He describes the process as then carried on in Lockport, the dynamo used being a large Brush machine weighing 2J^ tons and consuming about lOO horse-power in being driven at 900 revolutions per minute. " Conduction of the current of the large dynamo to the furnace and back is accompHshed by a complete metallic circuit, except where it is broken by the interposition of the carbon electrodes and the mass of pulverized carbon in which the reduction takes place. The circuit is of 13 copper wires, each 0.3 inch in dia- meter. There is likewise in the circuit an ampere meter, or am- * English Patent 4664 (1887). .f Journal of the Society of Chemical Industry, April 29, 1886. 334 ALUMINIUM. meter, through whose helix the whole current flows, indicating the total strength of the current being used. This is an import- ant element in the management of the furnace, for, by the posi- tion of the finger on the dial, the furnace attendant can tell to a nicety what is being done by the current in the furnace. Be- tween the ammeter and the furnace is a resistance coil of Ger- man silver kept in water, throwing more or less resistance into the circuit as desired. This is a safety appliance used in changing the current from one furnace to another, or to choke off the current before breaking it by a switch. "The furnace (see Figs. 30, 31, 32) is simply a rectangular Fig. 30. box. A, one foot wide, five feet long inside, and fifteen inches deep, made of fire-brick. From the opposite ends through the pipes BB the two electrodes CC pass. The electrodes are im- mense electric-light carbons three inches in diameter and thirty Fig. 31. LONGITUDINAL SECTION. inches long. If larger electrodes are required, a series this size must be used instead, as so far all attempts to make larger car- bons that will not disintegrate on becoming incandescent have failed. The ends of the carbons are placed within a few inches REDUCTION OF ALUMINIUM COMPOUNDS. 335 of each other in the middle of the furnace, and the resistance coil and ammeter are placed in the circuit. The ammeter regis- ters 50 to 2000 amperes. These connections made, the furnace is ready for charging. " The walls of the furnace must first be protected, or the in- tense heat would melt the fire-brick. The question arose, what would be the best substance to line the walls. Finely powdered charcoal is a poor conductor of electricity, is considered infusi- ble and the best non-conductor of heat of all solids. From these properties it would seem the best material. As long as Fig. 32. TRANSVERSE SECTION. air is excluded it will not burn. But it is found that after using pure charcoal a few times it becomes valueless ; it retains its woody structure, as is shown in larger pieces, but is changed to graphite, a good conductor of electricity, and thereby tends to diffuse the current through the lining, heating it and the walls. The fine charcoal is therefore washed in a solution of Hme- water, and after drying each particle is insulated by a fine coating of lime. The bottom of the furnace is now filled with this lining about two or three inches deep. A sheet-iron gauge is then placed along the sides of the electrodes, leaving about two inches between them and the side walls, in which space more of the charcoal is placed. The charge E, consisting of about 25 pounds of alumina, iii its native form as corundum, 12 336 ALUMINIUM. pounds of charcoal and carbon, and 50 pounds of granulated copper, is now placed within the gauge and spread around the electrodes to within a foot of each end of the furnace. For making iron alloy where silicon also is not harmful, bauxite or various clays containing iron and silica may be used instead of the pure alumina or corundum. In place of granulated cop- per, a series of short copper wires or bars can be placed parallel to each other and transverse to the furnace, among the alumina and carbon, it being found that where grains are used they sometimes fuse together in such a way as to short-circuit the current. After this, a bed of charcoal, F, the granules of which vary in size from a chestnut to a hickory, is spread over all, and the gauge drawn out. This coarse bed of charcoal above the charge allows free escape of the carbonic oxide generated in the reduction. The charge being in place, an iron top, G, lined with fire-brick, is placed over the whole furnace and the crevices luted to prevent access of air. The brick of the walls insulate the cover from the current. " Now that the furnace is charged, and the cover luted down, it is started. The ends of the electrodes were in the beginning placed close together, as shown in the longitudinal section, and for this cause the internal resistance of the furnace may be too low for the dynamo, and cause a short circuit. The operator, therefore, puts sufficient resistance into the circuit, and by watching the ammeter, and now and then moving one of the electrodes out a trifle, he can prevent undue short-circuiting in the beginning of the operation. In about ten minutes, the cop- per between the electrodes has been melted and the latter are moved far enough apart so that the current becomes steady. The current is now increased till 1300 amperes are going through, driven by 50 volts. Carbonic oxide has already com- menced to escape through the two orifices in the top, where it burns with a white flame. By slight movements outward of the electrodes during the coming five hours, the internal resistance in the furnace is kept constant, and at the same time all the different parts of the charge are brought in turn into the zone REDUCTION OF ALUMINIUM COMPOUNDS. 337 of reduction. At the close of the run the electrodes are in the position shown in the plan, the furnace is shut down by placing a resistance in the circuit, and then the current is switched into another furnace charged in a similar manner. It is found that the product is larger if the carbons are inclined at angles of 30° to the horizontal plane, as in Fig. 33. Fig. 33- SECTION OF THE COWLES FURNACE. " This regulating of the furnace by hand is rather costly and unsatisfactory. Several experiments have therefore been tried to make it self-regulating, and on January 26, 1886, a British patent was applied for by Cowles Bros, covering an arrange- ment for operating the electrodes by means of a shunt circuit, electro-magnet, and vibrating armature. Moreover, if the elec- trodes were drawn back and exposed to the air in their highly heated state, they would be rapidly wasted away. To obviate this, Messrs. Cowles placed what may be called a stufifiing-box around them, consisting of a copper box filled with copper shot. The wires are attached to the boxes instead of the electrodes. The hot electrodes as they emerge from the furnace first en- counter the shot, which rapidly carry off the heat, and by the time they emerge from the box they are too cool to be oxidized by contact with the air. " Ninety horse-power have been pumped into the furnace for five hours. At the beginning of the operation the copper first melted in the centre of the furnace. There was no escape for the heat continually generated, and the temperature increased until the refractory corundum melted, and being surrounded on all sides by carbon, gave up its oxygen. This oxygen, uniting with the carbon to form carbonic oxide, has generated heat 338 ALUMINIUM. which certainly aids in the process. The copper has had noth- ing to do with the reaction, as it will take place in its absence. Whether the reaction is due to the intense heat or to electric action it is difficult to say. If it be electric, it is Messrs. Cowles' impression that we have here a case where electrolysis can be accomplished by an alternating current, although it has not been tried as yet. Were the copper absent, the aluminium set free would now absorb carbon, and become a yellow crystal- line carbide of aluminium ; but, instead of that, the copper has become a boiling, seething mass, and the bubblings of its vapors may distinctly be heard. The vapors probably rise an inch or two, condense, and fall back, carrying with them the freed alu- minium. This continues until the current is taken ofif the fur- nace, when we have the copper charged with 1 5 to 30 per cent., and in some cases as high as 40 per cent, of its weight of alu- minium, and a little silicon. After cooling the furnace this rich alloy is removed. A valuable property of the fine charcoal is that the metal does not spread and run through the inter- stices, but remains as a liquid mass, surrounded below and on the sides by fine charcoal, which sustains it just as flour or other fine dust will sustain drops of water for considerable periods, without allowing them to sink in. The alloy is white and brittle. This metal is then melted in an ordinary crucible furnace, poured into large ingots, the amount of aluminium in it determined by analysis, again melted, and the requisite amount of copper added to make the bronze desired. "Two runs produce in ten hours' average work 100 pounds of white metal, from which it is estimated that Cowles Bros., at Lockport are producing aluminium in its alloys at a cost of about 40 cents per lb. The Cowles Company will shortly have 1200 horse-power furnaces. With a larger furnace there is no reason why it should not be made to run continuously, like the ordinary blast furnace. " In place of the copper any non-volatile metal may be used as a condenser to unite with any metal it may be desired to reduce, provided, of course, that the two metals are of such a REDUCTION OF ALUMINIUM COMPOUNDS. 339 nature that they will unite at this high temperature. In this way aluminium may be alloyed with iron, nickel, silver, tin or cobalt. Messrs. Cowles have made alloys containing 50 alu- minium to 50 of iron, 30 aluminium to 70 of copper, and 25 aluminium to 75 of nickel. Silicon or boron or other rare metals may be combined in the same way, or tertiary alloys may be produced ; as, for instance, where fire- clay is reduced in presence of copper we obtain an alloy of aluminium, silicon and copper." Soon after Mr. Thompson's description, the plant at Lock- port was increased by the addition of the largest dynamo up to that time constructed, built by the Brush Electric Company, and dubbed the " Colossus." This machine weighs almost ten tons, and when driven at 423 revolutions per minute it pro- duced a useful current of 3400 amperes at a tension of 68 volts, or at 405 revolutions produced a current of 3200 amperes with 83 volts electro-motive force, indicating 249,000 Watts or 334 electric horse-power. The steam engine was, in the latter case, developing nearly 400 horse-power, and could not supply more ; it was judged that the dynamo could have been driven to 300,000 Watts with safety. The first run with this machine was made in September, 1886. The furnaces used for this cur- rent are of the same style as that described by Mr. Thompson, but are larger, the charge being 60 lbs. of corundum, 60 lbs. of granulated copper, 30 lbs. of coarse charcoal besides the pulver- ized lime-coated charcoal used in packing. The operation of reducing this charge takes about two hours. As soon as the operation is finished the current is switched off into another furnace prepared and charged, so that the dynamo is kept work- ing continuously. In 1888, the Cowles Company had two of these large dynamos in operation, and eight furnaces in use. With two-hour runs a furnace is tapped every hour, producing about 80 lbs. of bronze averaging 18 per cent, of aluminium. The capacity of the plant is, therefore, about i}i tons of 10 per cent, bronze per day. Their alloys were sold in 1890 on the basis of $2.50 per lb. for the contained aluminium. 340 ALUMINIUM. The Cowles Syndicate Company, of England, located at Stoke-on-Trent, have set up a large plant at Milton, where, pro- fiting by the experience of the parent concern in America, still larger electric currents are used, these being found more eco- nomical. The dynamo in use at this works was built by Cromp- ton, and supplies a current of 5000-6000 amperes at 50 to 60 volts. There are two furnace-rooms, each containing six fur- naces, aluminium and silicon bronze being produced in one room, and ferro-aluminium in the other. The furnaces used measure 60 by 20 by 36 inches, inside dimensions, and differ from those previously shown by having the electrodes inclined at an angle of about 30°. (See Figs. 33, 34). The electrodes COWLES' ELECTRIC SMELTING FURNACES AT STOKE-ON-TRENT, ENGLAND. used are formed by bundling together 9 carbon rods, each 2^^ inches in diameter, each electrode weighing 20 lbs. More re- cently larger carbons have been obtained, 3 inches in diameter, and an electrode formed of five of these weighs 36 lbs. The furnace is charge^ as previously described. The current is started at 3000 amperes, gradually increasing to 5000 during the first half hour, and then keeping steady until the run is ended, which is about one and a half hours from starting. The product of each run is about 100 lbs. of raw bronze containing 15 to 20 per cent, of aluminium. The return is said to average i lb. of contained aluminium per 18 REDUCTION OF ALUMINIUM COMPOUNDS, 34I electric horse-power hours, or ij^ lbs. per electric horse- power per day. The works produce about 200 lbs. of alumin- ium contained in alloys per day. The raw bronze is stacked until several runs have accumulated, then a large batch is melted at once in a reverberatory furnace, refined and diluted to the proportion of aluminium required by adding pure copper. The Cowles Company, both in England and America, pro- duce six standard grades of bronze as follows : 'Special" A. A B C D E 11 per cent, of aluminium 10 ( it TA it It S-SV2 t ti t it i ti Their ferro-aluminium is sold with usually 5 to 7 per cent. of aluminium, but 10, 13, and 15 per cent, is furnished if asked for. Products of the Cowles furnace. — Dr. W.. Hampe obtained the following results on analyzing a sample of Cowles Bros.' 10 per cent, bronze : Copper 90.058 Aluminium 8.236 Silicon 1.596 Carbon. 0.104 Magnesium 0.019 Iron trace. 100.013 A sample of 10 per cent, bronze, made in the early part of 1886, and analyzed in the laboratory of the Stevens Institute, showed — Copper 88.0 Aluminium 6.3 Silicon 6.5 but it is evident that the percentage of silicon has since then been lowered. 342 ALUMINIUM. The ferro-aluminium used by Mr. Keep in his tests on cast- iron was furnished by the Cowles Company, and analyzed — Aluminium I ^4^ Silicon , 3'86 A sample shipped to England in December, 1886, contained — Iron 86.69 Combined carbon I.oi Graphitic carbon 1.9' Total 2.92 Silicon 2.40 Manganese 0.31 Aluminium 6.50 Copper 1.05 Sulphur 0.00 Phosphorus 0.13 85.46 86.04 86.00 84.00 8.65 9.00 9.25 10.50 2.20 2.52 2.3s 2.40 3-77 2.41 2.50 The copper in this alloy was present by accident, the alloy regularly made containing none, but the rest of the analysis gives a correct idea of the constitution of the alloy. Prof. Mabery gives several analyses of Cowles' ferro-aluminium : — * Iron 85.17 Aluminium 8.02 Silicon 2.36 Carbon The slags formed in the furnace in producing this alloy were analyzed as follows : — Silica 0.78 4.10 Alumina (insoluble) 0.20 — Lime 28.50 14.00 Iron 1.50 29.16 Alumina (soluble) -(- aluminium 38.00 48.70 Sulphur 0.50 — Graphite 5.00 2.60 Combined carbon 0.90 0.48 The slags formed when producing bronze vary in composition, "American Chemical Journal, 1887, p. 11. REDUCTION OF ALUMINIUM COMPOUNDS. 343 and are usually crystalline, with a shining, vitreous lustre. Their analysis shows — Alumina (insoluble) 55.30 66.84 — Alumina (soluble) + aluminium 21.80 14.20 — Lime 3.70 1.44 6.77 Copper — 3.32 i.oo Carbon 0.65 The lime present probably existed as calcium aluminate. These slags contained only a small amount of aluminium, rarely any iron, and were usually free from silica. The same chemist analyzed a peculiar product sometimes formed in the furnace when smelting for bronze, in the shape of crystalline masses, steel-gray to bright yellow in color, semi- transparent and with a resinous lustre. These all contained aluminium, copper, silicon and calcium in various proportions, and when exposed to the air fell to powder. Analyses gave Copper 26.70 35-0° 20.00 — Aluminium 66.20 53-30 74.32 15.23 Silicon 5.00 12.30 2.86 20.55 Calcium 2.00 0.20 2.86 ^ Tin _ _ _ 49.26 99.90 100.80 100.04 85.04 The latter product was formed in smelting for aluminium-tin. Prof. Mabery also found that the soot collecting at the ori- fices on top of the furnace contained 10 to 12 per cent, of alu- minium ; also that when alumina and carbon alone were heated and silica was present, the aluminium formed dissolved up to 10 per cent, of silicon, which, on dissolving the aluminium in hydrochloric acid, was left as crystalline or graphitic silicon. Reactions in Cowles' process. — The inventors, themselves, claim " reduction in a furnace heated by electricity in presence of carbon and a metal." In their first pamphlet they say that " the Cowles process accomplishes the reduction of alumina by carbon and heat." Professor Mabery and Dr. Hunt, already 344 ALUMINIUM. quoted, and Dr. Kosman * look at the process in no other light than that the electric current is utilized simply by its conver- sion into heat by the resistance offered, and that pure elec- trolysis is either absent or occurs to so small an extent as to be inappreciable. Indeed, if we consider the arrangement of the parts in the Cowles furnace we see every effort made to oppose a uniform, high resistance to the passage of the current and so convert its energy into heat, and an entire absence of any of the usual arrangements for electrolysis. For instance, elec- trolysis requires a fluid bath in circulation, so that each ele- ment of the electrolyte may be continuously liberated at one of the poles and the presence of any foreign material, as bits of carbon, between the poles is to be avoided if possible, since they short-circuit the current and hinder electrolysis proper. I think the arrangement of the furnace shows no attempt to fulfil any of the usual conditions for electrolysis, but is one of the best arrangements for converting the energy of the current entirely into heat. Dr. Hampe, however, in spite of these evident facts, draws the conclusion that because he was unable to reduce alumina by carbon in presence of copper at the tem- perature of a Deville lime-furnace, that it was therefore to be assumed that even the somewhat higher temperature of the electric furnace alone would be insufficient to accomplish the desired reaction, and hence the effect of the electric arc must be not only electro-thermic in supplying heat, but afterwards electrolytic, in decomposing the fused alumina. If we figure out the useful effect of the current, i. e., the pro- portion of its energy utilized for the purpose of reducing alumina, we find a low figure ; but it is well to note that although the power required is one of the main features of this way of reduction, yet this item is so cheap at the firm's works that it becomes a secondary consideration in the economy of the process. A 300 horse-power current is equivalent to an expenditure of 300 7 — ?__ jg J 000 calories of heat per hour. Theoretically, 424 * Stahl und Eisen, Jan. I REDUCTION OF ALUMINIUM COMPOUNDS. 345 this amount of heat would produce i^i^ = 261^ kilos or 58 pounds of aluminium. However, about 7 pounds are obtained in an hour's working, which would show a useful effect of 12 per cent. This should even be diminished, since no account has been taken of the combustion of carbon in the furnace to carbonic oxide. The remainder of the heat account, probably 90 per cent, of the whole, is partly accounted for by the heat contained in the gases escaping and the materials withdrawn from the furnace (of which no resonable estimate can be made, since the question of temperatures is so uncertain) and the large remainder must be put down as lost by radiation and conduction. As before remarked, water power is obtained by this company very cheaply, and even this large loss does not make much show in the cost of the alloy, yet the figures show that a much larger useful effect should be possible, and it is not at all improbable that the prospect of getting double or triple the present output from the same plant is at present inciting the managers to fresh exertions in utilizing the power to better advantage. Mr. H. T. Dagger's paper* on the Cowles process in Eng- land, states that the product at their Milton works is i lb. of aluminium to 18 electric horse-power per hour, which would show that the dissociation of the alumina represented nearly 30 per cent, of the energy of the current ; but the data given in the body of this gentleman's paper (p. 303 ) do not seem to indi- cate so large a return as is stated above. Mr. Dagger, more- over, maintains the purely electro-thermic action of the current, denying that any electrolysis takes place at all, citing an ex- periment with the alternating current in one of these furnaces, which produced as much aluminium per horse-power as did the direct current. In such an experiment electrolysis must neces- sarily be absent. In the discussion of Heroult's alloy process it will be shown that in both it and Cowles' process the largest part of the re- * British Association for Advancement of Science, Newcastle, 1889. 346 ALUMINIUM. duction must necessarily be performed by chemical and not by electrolytic action. I do not introduce this discussion here, since the two processes resemble each other so closely in the reaction involved that they can best be considered together. Since 1892 no aluminium has been made in England by this process, as the low price of pure aluminium killed the market for ready-made aluminium alloys. I cannot say exactly to what extent the Lockport works is running at the present time, but it is probable that the death of one of the Cowles brothers in 1893 and the sharp competition from pure aluminium have seriously hampered the business of the American company. At least, their products are not frequently seen on the market. It may be proper to interject here mention of an unfortunate occurrence in the history of the Cowles Company. They sold only aluminium alloys until January, 1891, when they began to advertise and sell pure aluminium made, it was said, by a new process. The Pittsburgh Reduction Company working the Hall process were then selling pure aluminium as low as $1.50 per pound, while the Cowles Company commenced sell- ing as cheap as $1.00. Inside of two months the Pittsburgh Reduction Company instituted suit for infringement of the Hall patents, asking the courts meanwhile for a preliminary injunction. Judge Ricks, of Ohio, denied a complete injunc- tion, but restrained the defendants from increasing the output of their plant during the trial of the suit, or from selling alu- minium below a price to be named by the complainants. The latter named $1.50 per pound, and this fixed the market price for some months. Several metallurgical experts of wide repu- tation were engaged by both sides, and very voluminous testi- mony was taken. While the suit was pending, the price of aluminium was reduced by the European makers to 5 marks a kilo (56 cents a pound), at which price important quantities began to be imported, and the domestic makers could sell very Httle at $1.50. In consequence, the Pittsburgh Reduction Company notified the court that it would sell as low as $0.50 per pound. At this price, which was very nearly the cost of REDUCTION OF ALUMINIUM COMPOUNDS. 347 production, aluminium continued until the suit was finally de- cided, in February, 1893, in favor of the Hall process. Judges Taft and Ricks decided that the Cowles Company were using the Hall process when they electrolyzed a bath of molten cryolite in which alumina was dissolved, and they were ordered to stop the infringement and to pay the damages which it might be estimated that their infringement had caused the complainants' business. Menges' Patent. * This inventor proposes to produce aluminium or aluminium bronze by mixing aluminous material with suitable conducting material, such as coal, and a cohesive material, then pressing into cylinders and baking hard. These strong, compact bars conduct electricity, and are to be used like the carbon elec- trodes of electric lamps in a suitably inclosed space. Farmer's Patent. M. G. Farmer f mixes aluminous material with molasses or pitch, making a paste which is moulded into sticks, burned, and used as electrodes, inclosed in a furnace. Aluminium is produced by the arc, and drops into a crucible placed imme- diately beneath. Several other persons have patented exactly the same method of procedure as that indicated by Menges and Farmer, with the modification in some cases of mixing iron or copper turnings with the aluminous material, and having the melted material drop into a furnace kept hot by burning ordinary fuel. Such a method of reducing refractory ores was even suggested as far back as 1853. None of such processes are likely to give results sufficiently economical for commercial use. Kleiner's Process (1886). This was devised by Dr. Ed. Kleiner of Zurich, Switzerland, * German Patent, 40354 (1887). t English Patent, 10815, Aug. 6, 1887. 348 ALUMINIUM. and was patented in most of the European States. The Eng- lish patent is dated 1886.* The first attempts to operate it were at the Rhine Falls, Schaffhausen, and were promising enough to induce Messrs. J. G. Nethers, Sons & Co., pro- prietors of an iron works there, to try to obtain water rights for 1500 horse power, announcing that a company (the Kleiner Gesellschaft) with a capital of 12,000,000 francs, was prepared to undertake the enterprise and build large works. The pro- position is said to have met with strong opposition from the hotel-keepers and those interested in the falls as an attraction for tourists, and the government declined the grant, consider- ing that the picturesqueness of the falls would be seriously afifected. This is the reason given by those interested in the process for its not being carried out in Switzerland, it being then determined to start a works in some part of England where cheap coal could be obtained, and test the process on a large scale. A small experimental plant was then set up in the early part of 1887 on Farrington Road, London, where it was inspected by many scientific men, among them Dr. John Hop- kinson, F. R. S., who reported on the quantitative results obtained ; a description of the process as here operated was also written up for " Engineering." With the co-operation of Major Ricarde-Seaver a larger plant was put up at Hope Mills, Tydesley, in Lancashire, where the process was inspected and reported on by Dr. George Gore, the electrician. After his report we learn that the patents were acquired by the Alumin- ium Syndicate, Limited, of London, a combination of capitalists among whom are said to be the Rothschilds. The aluminium compound used is commercial cryolite. It is stated that the native mineral from Greenland contains on an average, according to Dr. Kleiner's analysis, 96 per cent, of pure cryolite, the remainder being moisture, silica, oxides of iron and manganese. As pure cryolite contains 13 per cent, of aluminium, the native mineral will contain 12^ per cent., ♦English Patents, 8531, June 29, 1886, and 15322, Nov. 24, 1886. REDUCTION OF ALUMINIUM COMPOUNDS. 349 all of which Dr. Kleiner claims to be able to extract. It is further remarked that as soon as sufificient demand arises, an artificial cryolite can be made at much less cost than that of the native mineral, which now sells at ;^i8 to ;^20 a ton. The rationale of the process consists in applying the electric current in such a way that a small quantity of it generates heat and keeps the electrolyte in fusion, while the larger quantity acts electrolytically. Dry, powdered cryolite is packed around and between carbon electrodes in a bauxite-lined iron crucible ; on Fig. 35. passing a current of high tension (80 to 100 volts) through the electrodes, the cryolite is quickly fused by the heat of the arc and becomes a conductor. As soon as the electrolyte is in good fusion the tension is lowered to 50 volts, the quantity being about 150 amperes, the arc ceases and the decomposi- tion proceeds regularly for two or three hours until the bath is 35° ALUMINIUM. nearly exhausted. The evolved fluorine is said to attack the bauxite, and by thus supplying aluminium to the bath extends the time of an operation. In the first patent the negative car- bon was inserted through the bottom of the melting cavity, the positive dipping into the bath from above, (Fig. 35) but it was found that while the ends of the positive carbon immersed in the cryolite were unattacked, the part immediately over the bath was rapidly corroded. In the second patent, therefore, the positive electrode was circular and entirely immersed in the cryolite, connection being made by ears which projected through the side of the vessel. (Fig. 36.) As the carbons Fig. 36. are thus fixed, the preliminary fusion is accomplished by a movable carbon rod suspended from above, passing through the circular anode and used only for this purpose. The bath being well fused and the current flowing freely between the fixed carbons, the rod is withdrawn. The carbons are said to be thus perfectly protected from corrosion, and able to serve almost indefinitely. The melting pots finally used were or- dinary black-lead crucibles, which are not usually injured at all, since the fused part of the cryolite does not touch them, and they last as many as 300 fusions. After the operation, the carbons are lifted out of the bath and the contents cooled. REDUCTION OF ALUMINIUM COMPOUNDS. 35 I When solid, the crucibles are inverted and the contents fall out. This residue is broken to coarse powder, the nodules of aluminium picked out, melted in a crucible and cast into bars. The coarse powder is then ground to fine dust. This powder is more or less alkaline and contains a greater or less excess of fluoride of sodium in proportion to the amount of aluminium which has been taken out. If only a small proportion of the metal has been extracted and the powder contains only a small excess of sodium fluoride, it is used again without any pre- paration in charging the crucibles ; but if as much as 5 or 6 per cent, of aluminium has been removed and the powder, therefore, contains a large excess of sodium fluoride, it is washed with water for a long time to remove that salt, which slowly dissolves. The solution is reserved, while the powder remaining is unchanged cryolite, and is used over. Dr. Gore states that if the powder, electrodes and crucible are perfectly dry, there is no escape of gas or vapor during the process ; but if moisture is present, a small amount only of fumes of hydrofluoric acid appear, and that there is no escape of fluorine gas at any time. Dr. Kleiner hopes to soon dispense with the interruption of the process, washing, etc., by regenerating cryoHte in the crucible itself and so making the process con- tinuous. One of the great advantages claimed is that the aluminium is obtained in nodules, and not in fine powder; if it was, it could not all be collected because it is so light, some of it would float upon the water during the washing process and be lost, and even when collected it could not be dried and melted without considerable loss. It has been found impossible in practice to obtain all the aluminium from a given quantity of cryolite in less than two fusions, for the sodium fluoride collecting in the bath hinders the production of the metal. The proportion extracted by a single fusion depends upon its duration. In the operations at Tydesley, a fusion lasting 24 hours separated only 2^ per cent, of aluminium, whereas the cryolite contained 12^ per cent. At this rate, to extract the whole in two operations would 352 ALUMINIUM. require two fusions of 6o hours each. As to the output, on an average a current of 38 electric horse-power deposited 150 grammes of aluminium per hour, being a little over 3 grammes per horse-power. Since a current of 50 volts and 150 amperes, such as was stated above as the current in each pot, is equal to 50x^50 ^^ j^ electric H. P., it is probable that the 38 H. P. cur- rent mentioned must have been used for four crucibles. Now, the output of four crucibles, each with a current of 150 amperes, should have been 0.00009135X150X4=0.0548 gramme per second, or 197.3 grammes per hour; the difference between this and the amount actually obtained, or 47.3 grammes, is the amount of aluminium which was produced and then afterwards lost either as fine shot-metal or powder, or dissolved again by corroding elements in the bath. To calculate how the output of 3 grammes per electric H. P. per hour compares with the quantity of metal which this amount of energy should be able to produce, we can assume that since it takes at most 4 volts to decompose the aluminium fluoride, the four crucibles would consume 16 volts in decomposition, being sixteen-fiftieths of the total voltage employed. Since the amperes only produced 150 grammes out of 197.3 theoretically possible, the efhciency over all is only 16 150 1 As to the purity of the metal obtained, the process is met at the outset by the silica and iron oxide in the cryolite, which are probably all reduced with the first few grammes of aluminium thrown down. This can possibly be remedied by using a purer artificial cryolite ; the impurities cannot generally be separated from the natural mineral. Then there are impurities of a simi- lar nature coming from the carbons used, and which are gene- rally present if especial pains are not taken to get very pure ma- terials for making them. Dr. Kleiner's early attempts produced metal of 85 to 95 per cent, purity, but he stated in 1889 that it was uniformly 95 to 98 per cent., and being put on the market in REDUCTION OF ALUMINIUM COMPOUNDS. 353 competition with other commercial brands. It appears, how- ever, from a consideration of the preceding data, that the pro- cess could not produce aluminium much cheaper than 12 shil- lings a pound, and it was therefore abandoned in 1890. It may be observed that the mechanical arrangements for carrying on this process, as above outlined, could not stand comparison with the present forms of apparatus in use by the Hall and Heroult processes. Lossier's Method. * This is a device for decomposing the natural silicates by electricity and obtaining their aluminium. The bath is com- posed of pure aluminium fluoride or of a mixture of this salt and an alkaline chloride, and is kept molten in a round bot- tomed crucible placed in a furnace. The electrodes are of dense carbon and are separated in the crucible by a partition reach- ing beneath the surface of the bath. The positive electrode is furnished with a jacket or thick coating of some aluminium sili- cate plastered on moist and well dried before use. When the current is passed, the aluminium fluoride yields up its fluorine at this pole and its aluminium at the other. The fluorine com- bines with the aluminium silicate, forming on the one hand alu- minium fluoride, which regenerates the bath, on the other silicon fluoride and carbonic oxide, which escape as gases. The metal liberated at the negative pole is lighter than the fused bath, and therefore rises to the surface. M. Grabau cites as one of the recommendations of aluminium fluoride for use in his process (p. 295), that it is quite infusible, so it would appear that Lossier has made a mistake in suppos- ing that it could be melted alone in a crucible. It would, how- ever, make a very fusible bath when the alkali chloride was added. It is probable that the carrying out of this method would develop great trouble from the attacking of the crucible by the very corrosive bath, the disintegration of the carbons, which would cause much trouble at the negative pole especially, * German Patent (D. R. P.), No. 31089. 23 354 ALUMINIUM. and the oxidation of the fluid aluminium on the surface of the bath. The process has never been attempted on a large scale, and it is very unlikely that it ever will be. OmhoKs Furnace. I. Omholt and the firm Bottiger and Seidler, of Gossnitz, have patented the following apparatus for the continuous electrolysis of aluminium chloride:* — The bed of a reverberatory furnace is divided by transverse partitions into two compartments, in each of which are two re- torts semi-circular in section, lying side by side horizontally across the furnace, with the circular part up. They are sup- ported on refractory pillars so that their open side is a small distance above the floor of the furnace. The aluminium com- pound being melted on the hearth, it stands to the same depth in both retorts, and if the electrodes are passed through the bottom of the hearth they may remain entirely submerged in molten salt and each under its own retort cover. The metal therefore collects in a liquid state under one retort and the chlorine under the other, both being preserved from contact or mixture with the furnace gases by the lock of molten salt. The chlorine can thus be led away by a pipe, and utilized, while the aluminium collects without loss, and is removed at convenient intervals. The great cost of making aluminium chloride will probably prevent it ever being used again in the metallurgy of alumin- ium, but the form of furnace described above may possibly be utilized in operating the decomposition of some other aluminium salt, such as the double sulphide with soda. Minefs Process (1887). This consists, according to the patent specification, f in the electrolysis of a mixture of sodium chloride with aluminium fluoride or with the separate or double fluorides of aluminium * German Patent (D. R. P.), No. 34728. t English Patent, No. 10057, July r8, 1887. REDUCTION OF ALUMINIUM COMPOUNDS. 355 1 and sodium, melted in a non-metallic crucible or in a metallic one inclosed in a thin refractory jacket to avoid filtration, the aluminium fluoride decomposed being regenerated by causing the fluorine vapors evolved to act on bauxite or alumina placed somewhere about the anode. The details of the appar- atus and bath are as follows : — Disposition of the Apparatus. — The pots or crucibles used may be of refractory earth, plumbago, or of metal, and in cases where an alloy is required the crucible itself serves as an elec- trode. None of these, however, resist the corrosive power of the electrolyte and would under ordinary conditions be quickly destroyed. To overcome this difficulty two special devices are employed. When alloys are to be made directly, the pot is cast of the metal with which the aluminium is to be combined. It is shaped with a sloping bottom and provided with a tap hole. The pot is encased in thin brickwork and is then made the negative electrode, the positive being two carbon rods dipped into the bath. As soon as the current is passed alu- minium is deposited on the walls of the pot, forming a rich alloy with the metal of which the pot is made (iron or copper). When this coating becomes sufficiently rich in aluminium, the heat of the bath melts it and it trickles down and collects at the bottom. After a certain time, the alloy can be tapped out regularly at intervals without interrupting the electrolysis. The metal thus obtained is principally aluminium containing a few per cent, of the metal of the pot, which is of no consequence, since the end to be finally attained is the production of an alloy with a smaller quantity of aluminium. When pure aluminium is to be obtained, an ingenious device is used to protect the metal from contamination by the metal of the pot. Carbon plates, A and C (Fig. 37), serve as anode and cathode, the cathode stand- ing upright in a small crucible placed upon a plate resting on the bottom of the pot. This crucible and plate are made from 'carbon blocks or from fused alumina or fluorspar moulded into the shape desired. As the metal is set free it trickles down the cathode and is caught in the crucible or cup, thus being 356 ALUMINIUM. prevented from spreading out over the bottom of the pot. To prevent the bath from corroding the pot, the wire R is passed from the latter to the negative pole of the circuit. The pot is thus made part of the negative electrode, but it is not intended that much of the current should pass through it, so a resistance coil is interposed between it and the battery or dynamo, so that Fig. 37. the derived current passing through the sides of the pot is only 5 to 10 per cent, of the whole current. The effect of this is that a small amount of aluminium is deposited on and alloys with the sides of the vessel, which protects the latter from cor- rosion and is only feebly acted upon by the bath. The metal deposited in the crucible is thus kept nearly pure, while a small amount of alloy falls to the bottom of the pot and is poured out after the crucible has been removed. When it is wished to obtain the purest aluminium, the intensity of the derived cur- rent passing through the pot is increased by removing part of the resistance interposed between it and the negative wire, thus also decreasing the intensity of the principal current. The REDUCTION OF ALUMINIUM COMPOUNDS. 357 nature of the electrodes proper may be varied. For producing pure aluminium the anode is carbon, the cathode carbon, and the pot either of copper or iron ; for producing copper alloys the anode may be either carbon or bright copper, and the cathode (pot) of carbon or copper; for producing iron alloys the anode may be either carbon or iron, while the vessel used as cathode is either of cast-iron or plumbago. Composition and properties of the baths. — Minet has made more careful electrical measurements on these fused baths than any other metallurgist, a point of particular importance in his experiments being the accurate measurement of the tempera- tures by means of a Le Chatellier electric pyrometer. On this account his result^re a valuable contribution to the knowledge of the present electrolytic processes, and are therefore worth repeating in extenso. Minet first experimented with a bath of Aluminium-sodium chloride 40 parts. Sodium chloride 60 " He says of the working of this mixture that it gives rise to abundant vapors, which are very disagreeable. In consequence, the bath becomes quickly impoverished in aluminium chloride, it becomes pasty, and can only be liquefied by raising the tem- perature almost to the melting point of sodium chloride. It is difficult under these conditions to produce regular and continu- ous electrolysis. Minet obtained much better results with aluminium fluoride. He mixed cryolite with common salt in the following propor- tions : Cryolite 37-5 parts. Sodium chloride 62.5 " giving a mixture whose formula would be AlFgSNaF + 6NaCl. This mixture has the following properties : Melting point 675° C. Vapors given off at 1056° C. Specific gravity at 829° C 1.76 Specific resistance at 870° C 0.32 ohms. 3S8 ALUMINIUM. The last datum means that a column of the electrolyte i centimetre square and i centimetre long would give 0.32 ohms resistance to the passage of the current. If the section of the electrolyte through which the current passed averaged 750 square centimetres, and the electrodes averaged 6 centimetres apart, the total resistance of the bath would be 0.32 X ^0.0026 ohms: 750 and if the current was 1 500 amperes, the voltage absorbed by the electrical conduction-resistance of the bath would be 0.0026 X 1500 = 3.9 volts. The specific resistance was found to decrease about 0.07 per cent, for every degree rise of temperature above 870°, or 7 per cent, for every lOO degrees. If this bath were simply electrolyzed, fluorine would be dis- engaged, escaping into the air as carbon fluoride, CF4, while the bath would become poorer in aluminium fluoride. If cryo- lite alone were added during the process, sodium fluoride would accumulate in the bath, and after a certain time sodium would be set free. If the bath is renewed by adding aluminium fluor- ide, this inconvenience is obviated, but there still remains the question of suppressing the noxious fluoride vapors set free. If the bath is renewed by placing alumina in the state of fine pow- der in the bath, dropping it especially around the anode, the fluorine set free may reform aluminium fluoride by attacking the alumina, setting free oxygen, which combines with the car- bon anode to form carbonic oxide. If the fluorine were not completely absorbed by the alumina, the amount escaping would have to be made up for by adding aluminium fluoride to the bath. The bath should therefore be fed by both alumina and aluminium fluoride. The above contains Minet's views of what takes place when alumina is added to the fluoride bath. He does not admit that any alumina can be really dissolved in the bath and be electro- REDUCTION OF ALUMINIUM COMPOUNDS. 359 lyzed as alumina (the view taken by Hall). Minet, in fact, maintains that when alumina is added to molten cryolite it sinks through it and remains undissolved, as, for instance, very fine marble dust would in water. Such, however, is not the experience of other investigators. According to numerous experiments by Hall and others using the present electrolytic processes, as well as some made by the writer, finely-divided alumina appears to dissolve in molten cryolite exactly as sugar does in water, and there is even a saturation point, at about 30 per cent., above which no more dissolves. The bath containing alumina forms to all appearances a homogeneous liquid. Driven from their first position, the adherents to Minet's views, having allowed that a homogeneous liquid bath does result, as- sert that the alumina is only mechanically suspended, like clay in muddy water, and that in this condition it is carried to the anode and unites with the fluorine set free. Such a view, however, is also erroneous, because regeneration in such a man- ner could not be anything like complete, and considerable amounts of fluorine would escape ; yet in the Hall process, when the operation is properly conducted, not a trace of fluoride gas escapes. Regeneration by mechanically-suspended alu- mina could not possibly be so complete. We shall continue describing Minet's experiments, asking that it be remembered, however, that we regard as erroneous his view that aluminium fluoride is the substance immediately de- composed by the current when alumina is present. Taking the bath already described, with electrodes of such size and distance apart that the conduction-resistance at 900° was 0.0044 ohms, the following results were obtained : — Temperature. Electromotive force Conduction-resistance for decomposition. of the bath. 900° 2.4 volts .0044 ohms 1000° 2.34 " .0033 " 1100° 2.17 " .0025 " If V' = the voltage required for decomposition, V° = the voltage required for conduction, V = the total voltage absorbed by the bath, A =; the amperage of the current. then [V = VI -(- AV".] 36o ALUMINIUM. We can thus calculate the voltage required to send through this bath any number of amperes at a given temperature. Thus, for lOO or looo amperes the voltage absorbed per bath would be as follows : Temperature. Amperes. Voltage for decomposition. 900" I0CX3° 1 100" 100 2.4 1000 2.4 100 2.34 1000 2-34 100 2.17 1000 2.17 iltage for Total Per cent, of total aduction iistance. voltage. voltage absorbed in conduction re- sistance. 0.44 2.88 «5 4.40 6.80 65 0-33 2.67 12 3-30 5.64 59 0.25 2.42 13 2.50 4.67 54 It thus appears that, using a bath of a given size, the voltage required to send lOOO amperes through it is only 2 to 2.5 times that required for 100 amperes. Since the power required is just in the same ratio, it follows that it is economical to send as large a current as practicable through a bath of a given size. The last column shows us the percentage of the energy of the current which will be converted into heat. It follows from these figures that the heating effect of the current increases very rapidly with its quantity, so that a given number of amperes will supply enough heat to keep the bath molten with- out exterior heat; more than this number would, in fact, raise the temperature of the bath too high, and this limits the size of the current which it is practicable to send through a bath of a given size. Minet also found that when such a bath contained salts of iron and silicon, which are weaker compounds than aluminium or sodium salts, a current of carefully regulated low voltage, and consequently of low density, would first separate these com- pletely. An experiment made with a bath in which the anode surface was 500 square centimetres, and gradually increasing the voltage, gave the following successive results : REDUCTION OF ALUMINIUM COMPOUNDS. 36 1 Total Amperes Amperes per Electro-motive Nature of the voltage passing. sq. c. m. of force of decom- metal deposited. used. anode. position (volts). I.2I 75 o.is 0.54 Iron. 1.68 100 0.20 0.7s Iron ( traces of silicon) . 2.48 125 0.25 1-37 Ferro-silicon. 2.89 150 0.30 1.54 Ferro-silicon (traces of aluminium) 2.94 15° 0.30 1.74 Silicon-aluminium (traces of iron) . 4.27 250 0.50 2.IS Aluminium (traces of silicon) . 6.85 500 1. 00 2.50 Aluminium (traces of sodium). The conduction-resistance of the bath remained very nearly constant throughout. In a large number of experiments, the amount of metal actu- ally obtained was 50 to 80 per cent, of the amount which the amperage of the current could theoretically produce, on an average about 60 per cent. As for the power required, an experiment lasting 24 hours, at a temperature of 1 160°, voltage 5.75, and amperes 1500, showed 21.5 grammes of aluminium deposited per hour per electric horse-power used. Another similar experiment, but with the electrodes closer together, the voltage consequently less, and at a lower temperature, gave 31.9 grammes per horse-power-hour, which would be 0.765 kilos (1.685 pounds) per electric horse-power per day. As the en- ergy of one horse-power-day is equivalent to the energy of oxi- dation of 2.1 kilos (4.63 pounds) of aluminium, the useful efifect over all is 36.5 per cent. Quality of metal. — When working for pure aluminium, about three-fourths of the metal produced is taken from the crucible in which the cathode stands, and is 98 to 99 per cent, pure ; the other one-fourth has been deposited on the sides of the cast-iron pot, and contains 10 to 20 per cent, of iron. It is poured out and used for making ferro-aluminium. Installations of the process. — Minet conducted his work at the expense of Messrs. Bernard Bros. The first experiments were made on the road Moulin Joli, in Paris, from March, 1887, to March, 1888. This plant consisted of a 6 horse-power engine and a Gramme dynamo capable of giving a current of 250 amperes at 12 volts tension. In the year named, this plant pro- 362 ALUMINIUM. duced about 500 kilogrammes of pure aluminium and 1500 kilogrammes of ferro-aluminium or aluminium bronze. The second installation was put up at Creil (Oise), com- menced operations in April, 1888, and continued working until October, 1891. This plant had a 40 horse-power engine, and an Edison dynamo giving a current of 1200 amperes and 27.5 volts. Regularly it was run at only 16 volts, operating three baths in tension, and at looo amperes. There were made here daily about 10 kilos of pure aluminium and 5 to 6 kilos of alu- minium in alloys. At the first location, Minet was enabled to study experiment- ally the purely scientific part of his processes ; the plant at Creil enabled him to solve the practical details of the process. In 1889, the Messrs. Bernard Bros, determined to work the process on a large, industrial scale, and cast around for a loca- tion having abundant water-power. It was decided to locate at Saint Michel in Savoy. The stream utihzed is the Valoirette, giving a volume of 3.5 cubic metres per second with a fall of 133 metres. This gives theoretically 6000 horse-power, and should produce 4000 electric horse-power. At this place were put up a turbine of 300 horse-power by Bouvier of Grenoble, and a dynamo of 275 horse-power by Hillairet-Huguet of Paris. The latter gives a current of 4000 amperes at 50 volts tension, aiid produces regularly about 150 kilos (330 pounds) of aluminium. It is stated that a 600 horse- power dynamo, actuated by a lOOO horse-power turbine, was started during 1894. Latest advices state that this estabUsh- ment has been acquired by a French company formed to work under the Hall patents. Feldman's Method (1887). A. Feldman, of Linden, Hannover, patented the following electrolytic process : * — A double fluoride of aluminium and an alkaline earth metal, * English Patent, No. 12575, Sept. 16, 1887. REDUCTION OF ALUMINIUM COMPOUNDS. 363 mixed with an excess of a chloride of the latter group, is either electrolyzed or reduced by sodium. The proportions of these substances to be used are such as take place in the following reactions : — 1. (AUF6+2SrF2) + 6SrCI.,=2Al+5SrF2+3SrCl2+6Cl. 2. (AljF6+2SrF2)+6SrCl2+6Na=2AH-sSrF2+3SrCl2+6NaCl. The three equivalents of strontium chloride are found in prac- tice to be most suitable. Potassium chloride may also be added to increase the fluidity, but in this case the strontium chloride must be in still greater excess. Even if the above reactions and transpositions do take place, the use of so much costly strontium salts would appear to ren- der the process uneconomical. Warren's Experiments (1887). Mr. H. Warren, of the Everton Research Laboratory, has outlined the following methods or suggestions, some of which had already been carried out, and probably others have since given useful ideas to workers in this line. The principle can hardly be called new, since suggestions almost identical with Mr. Warren's were made previously to his, but the latter's re- sults are the first recorded in this particular direction:* "This method of preparing alloys differs only slightly from the man- ner in which amalgams of different metals are prepared, substi- tuting for mercury the metals iron, copper, or zinc made liquid by heat. These metals are melted, connected with the negative pole of a battery, and the positive pole immersed in a bath of molten salt floating on top of the melted metal. The apparatus used is a deep, conical crucible, through the bottom of which is inserted a graphite rod, projecting about one inch within, the part outside being protected by an iron tube coated with borax. As an example of the method, to prepare silicon bronze, copper is melted in the crucible, a bath of potassium silico-fluoride is * Chemical News, Oct. 7, 1887. 364 ALUMINIUM. fused on top to a depth of about two inches. A thick platinum wire dips into this salt, and on passing the electric current an instantaneous action is seen, dense white vapors are evolved, and all the silicon, as it is produced, unites with the copper, forming a brittle alloy. Cryolite may be decomposed in like manner if melted over zinc, forming an alloy of zinc and alu- minium, from which the zinc can be distilled, leaving pure aluminium." Mr. Warren does not affirm that he has actually performed the decomposition of cryolite in the way recommended, but states that it may be done ; from which we would infer that he simply supposed it could. A well-recorded experiment, then, is needed to establish the truth of this statement. Neither does he propose to make aluminium bronze in this way; it may be that it was attempted and did not succeed, for Hampe states that an experiment thus conducted did not furnish him alu- minium bronze (p. 368). Zdziarski' s Patent. A. Zdziarski,* of Brest-Litowsk, Russia, appears to have patented the above principle in 1884, for in his patent he states that the metal to be alloyed with aluminium is melted in a crucible, covered with a fusible compound of aluminium for a flux (alumina and potassium carbonate may be used) and made the negative pole of an electric current, the positive pole being a carbon rod dipping in the flux. Grabau's Apparatus. LudwigGrabaUjf of Hannover, Germany, proposes to electro- lyze a molten bath of cryolite mixed with sodium chloride. The features of the apparatus used are an iron pot, in which the bath is melted, and water-cooled cylinders surrounding both electrodes, the jacket surrounding the negative one having a * English Patent 3090, Feb. 11, 1884. t German Patent (D. R. P.), No. 45012. REDUCTION OF ALUMINIUM COMPOUNDS. 365 bottom, the other not. The object of these cylinders is, at the positive electrode, to keep the liberated fluorine from attacking the iron pot and so contaminating the bath, at the other pole the liberated aluminium is kept from dropping to the bottom of the pot, where it might take up iron, and can be removed from the bath by simply lifting out the water-cooled cylinders and carbon electrode. Mr. Grabau states that he has abandoned this process because the inseparable impurities in the cryolite produced impurities in the metal; it may be that with the pure artificial cryolite, which he makes by his other processes (see p. 171), this electrolytic process may again be taken up. (See also p. 294.) Rogers' Process (1887). In July, 1887, the American Aluminium Company, of Mil- waukee, was incorporated, with a capital stock of $1,000,000, for the purpose of extracting aluminium by methods devised by Prof. A. J. Rogers, a professor of chemistry in that city. This gentleman had been working at the subject for three or four years previous to that time, but it has not been until re- cently that patents have been applied for, and they are still pending. The principle made use of has already been suggested in con- nection with the production of sodium (p. 219). It is briefly, that if molten sodium chloride is electrolyzed, using a molten lead cathode, a lead-sodium alloy is produced. This alloy is capable of reacting on molten cryolite, setting free aluminium, which does not combine with the lead remaining because of its weak affinity for that metal. If, then, cryolite is placed in the bath with the sodium chloride, the two reactions take place at once, and aluminium is produced. In the early part of 1888, the company erected a small experimental plant, with a ten- horse-power engine, with which the following experiments, among many others, were made: — I. *A current of 60 to 80 amperes was passed for several * Proceedings of the Wisconsin Nat. His. Soc, April, 1889. 366 ALUMINIUM. hours through a bath of cryolite melted in a crucible lined with alumina, and using carbon rods 2^ inches in diameter as electrodes, one dipping into the bath from above, the other passing through the bottom of the crucible into the bath. Only I or 2 grammes of aluminium were obtained, showing that the separated metal was almost all redissolved or reunited with fluorine. With the temperature very high, it was found that sodium passed away from the bath without reducing the cryolite. 2. A current averaging 54 amperes and 10 volts was passed for five and a half hours through a mixture of I part cryolite and 5 parts sodium chloride placed in a crucible with 3 70 grammes of molten lead in the bottom as the cathode. After the experiment, 25 grammes of aluminium were found in globules on top of the lead-sodium alloy. This latter alloy contained some aluminium. The globules were about as pure as ordinary commercial aluminium, and contained no lead or sodium. From another experiment it was determined that the lead-sodium alloy must first acquire a certain richness in sodium before it will part with any of that metal to perform the reduction of the cryolite. It was also found that a certain temperature was necessary in order that aluminium be pro- diiced at all. 3. A current of 75 amperes and about 5 volts suflficed to de- compose the bath and to produce 105 grammes of aluminium in seven hours. This would be nearly 30 grammes per hour for each electric horse-power. 4. A current of 80 amperes and 24 volts was passed through four crucibles connected in series for six hours, using a bath of I part cryolite and 3 parts sodium chloride with 450 grammes of lead in each crucible. The crucibles were heated regularly to a moderate temperature. There were obtained altogether 250 grammes of quite pure aluminium. This would be equal to 16 grammes per electric horse-power-hour. " A large number of similar experiments afforded a return of ^ to I ^ lbs. of aluminium per electric horse-power per day. REDUCTION OF ALUMINIUM COMPOUNDS. 367 The experimental plant now in operation consists of a 40 volt — TOO ampere — dynamo, the current being sent through six pots connected in series. When the bath is completely electrolyzed the contents of the crucible are tapped ofif at the bottom and a fresh supply of melted salt poured in quickly. The lead- sodium alloy run off is put back into the crucibles, thus keep- ing approximately constant in composition and going the rounds continuously. With this apparatus, 3 to 4 lbs. of alu- minium are produced regularly per day of 12 hours. As soon as patents are obtained, it is the intention of the company to put up a plant of 50 lbs. daily capacity, which can be easily increased to any extent desired as the business expands." Professor Rogers observes in regard to the apparatus that he has tried various basic linings for his clay crucibles, but a paste of hydrated alumina, well fired, has succeeded best. Some "shrunk" magnesia lining, such as is used in basic steel fur- naces, answered well, but could not be used because of the amount of iron in it. Lime could not be used, as it fluxed readily. The carbon rods lasted 48 hours without much cor- rosion if protected from the air during electrolysis. Carbon plates and cylinders were tried, but the solid rods gave the best results. About 8 to 10 per cent, of aluminium can be extracted from cryolite containing 12.85 P^r cent. The min- eral used was obtained from the Pennsylvania Salt Company, and was called pure, but it contained 2 per cent, of silica and I per cent, of iron. These impurities pass largely into the aluminium produced, but the company hoped to be able to manufacture an artificial aluminium fluoride which will not only be purer but less costly than this commercial cryolite. Professor Rogers infers that pure aluminium fluoride would not be an electrolyte, since the resistance of the bath increases as the amount of other salts present decreases. It is useless to base any accurate estimation of the cost of aluminium by this process on the data given above, since they were only for a small experimental plant. If, however, 75 per cent, of the aluminium in cryolite can be extracted at the rate 368 ALUMINIUM. of I lb. of metal per day per electric horse-power, and the metal is free from lead and sodium, (a sample sent me was of very fair quality,) it would seem that the process was in a fair way to compete on an equal footing with the other electro- lytic processes as operated in 1889, but it has been entirely distanced by more recent developments. Dr. Hampe on the Electrolysis of Cryolite. Prof. W. Hampe, of Clausthal, whose name is a guarantee of careful and exact observations, has written the following val- uable information on this subject, in presenting which we will also give the remarks of Dr. O. Schmidt, called forth by Hampe's first article. *" The electrolysis of a bath of cryolite mixed with sodium and potassium chlorides, using a layer of melted copper in the bottom of the crucible as cathode and a carbon rod as anode, gave balls of melted sodium which floated on the surface and burnt, but scarcely a trace of aluminium. Yet here the condi- tions were most favorable to the production of the bronze. The battery used consisted of twelve large zinc-iron elements.'' fDr. O. Schmidt, referring to this statement of Hampe's, quotes an opposite experience. He fused cryolite and sodium chloride together in a well-brasqued crucible in the proportions indicated by the reaction AUF6.6NaF+6NaCl=Al2Cle+i 2NaF. At a clear red heat the bath becomes perfectly fluid and trans- parent, and an anode of gas carbon and a cathode of sheet cop- per are introduced. On passing the current the copper did not melt but became covered with a film of deposited aluminium, which in part penetrated the electrode and in part adhered to the surface as a rich alloy which ultimately fused ofif and sank to the bottom of the crucible. With a plate i to i ^ millimetres thick, 10 per cent of its weight of aluminium could thus be de- * Ghemiker Zeitung, xii., 391 (1888). fldem, xii., 457 (i REDUCTION OF ALUMINIUM COMPOUNDS. 369 posited ; with one 3 millimetres thick, about 5 per cent. The metal could be made perfectly homogeneous by subsequent fusion in a graphite crucible. Dr. Schmidt further remarks (evidently on the supposition that the reaction he gives actually takes place) that on thermo-chemical grounds sodium would not here be reduced, because while the molecule of sodium chloride requires 97.3 calories for its decomposition, that of aluminium chloride, — ^, requires only 80.4, and the current would attack first the most easily decomposed. He also states that the cal- culated difference of potential for the dissociation of aluminium chloride which is ^'^ = 3.5 volts, was actually observed, and the tension of the current must have been increased to about 4.5 volts to bring about the decomposition of the sodium chloride.* Dr. Hampe's statement occasioned several other communica- tions, which he considers and replies to in the following article : f — " Dr. O (whose name I withhold at his own request) writes to me that by electrolyzing pure cryolite, using a nega- ative pole of molten copper, he never obtained aluminium bronze ; but, on the other hand, always obtained it if he used the mixture of cryolite and sodium chloride mentioned by Dr. Schmidt, and in place of the molten copper a thick stick of the unfused metal. A letter from R. Gratzel, Hannover, contains a similar confirmation of the latter observation. By electrolyzing a mixture of 100 parts cryolite with 150 of sodium chloride in * Aside from Hampe's subsequent remarks as to no aluminium chloride being formed, we would further point out the fact that the decomposition of a chemically equivalent quantity of aluminium chloride requires not — ^ = 80.4 calories, but ^"' °° or 53.6 calories, and the calculated difference of potential is properly -^^ or 2.3 volts. The fact that the observed tension was 3.5 volts shows that the current was not strong enough to decompose the sodium chloride, as Schmidt observes, and the fact that this current deposited aluminium would show that the heat of formation of aluminium fluoride at this temperature cannot be greater than 23X3.5X6^483 (thousand) calories. tChemiker Zeitung (Cothen), xiii., 29 and 49. 24 370 ALUMINIUM. a graphite crucible holding 30 kilogrammes, aluminium bronze dripped down from the ring-shaped copper cathode used, while chlorine was freely disengaged at the carbon anode. But after a time, long before the complete decomposition of the cryolite, the formation of bronze stopped — even an attacking of that already formed sometimes taking place. Pellets of an alloy of sodium and aluminium appear on the surface and burn with a white light. " These comments excited me to further research in the mat- ter. At first, it was necessary to consider or prove whether by melting sodium chloride with cryolite a true chemical decom- position took place, such as Dr. Schmidt supposed. If this were the case, the very volatile aluminium chloride must neces- sarily be mostly driven off on melting the mixture, and at a temperature of 700° to 1000° C. there could not be any left in it. But an experiment in a platinum retort showed that such a reaction positively does not occur ; for neither was any alu- minium chloride volatilized, nor did the residue contain any, for on treatment with water, it gave up no trace of a soluble aluminium compound. During the melting of the mixture, acid vapors proceeded from the retort, and a small quantity of cryo- lite was volatilized into the neck of the retort. Dr. Klochman has shown that cryolite always contains quartz, even colorless, transparent pieces, which to the naked eye appear perfectly homogeneous, showing it when examined in thin sections under the microscope, and on melting the mineral opportunity is given for the following reactions : SiOa 4- 4NaF = SiF, + 2Na20, sNa^O + Al^Fe = 6NaF + AUO,, as is rendered probable by the appearance of delicate crystals of alumina on the inner surface of the retort just above the fusion. The silicon fluoride probably passes away as silico- fluoride of sodium. " If cryolite is fused with such metallic chlorides that really do REDUCTION OF ALUMINIUM COMPOUNDS. 37 1 bring about a decomposition, there is never any aluminium chloride formed in these cases, but the sodium of the cryolite is exchanged for the other metal. Dr. O , to whom I owe this observation, fused cryolite with calcium chloride, hoping that aluminium chloride would distil, but obtained instead crystals of the calcium salt of alumina-fluoric acid ; thus, NaeAljFi, + aCaClj = 6NaCl + CajAl^Fi^, and in like manner can be obtained the analogous strontium or barium compounds. " Just as erroneous as the supposed production of aluminium chloride are the other arguments advanced by Dr. Schmidt, re- garding the reasons why sodium could not be set free. The self-evident premises for the propositions are lacking, viz. : that the two bodies compared are conductors. On the contrary, I have previously shown* that aluminium chloride and bromide, and more certainly its fluoride, belong to the non-conductors. It follows, then, that there can remain no doubt that on elec- trolyzing pure cryolite, or a mixture of it, with sodium chloride, only sodium will be set free at first, either from sodium fluoride or the more easily decomposable sodium chloride. The pres- ence or absence of sodium chloride is consequently, chemically, without significance. " Since the experiments with solid cathodes gave aluminium, while those with molten copper did not, these results being independent of the presence or absence of sodium chloride, the next attempt made was to seek for the cause of the different re- sults in the differences of temperature. It was found that when the electrolysis takes place at a temperature about the melting point of copper, bubbles of sodium vapor rise and burn, and any aluminium set free is so finely divided that it is attacked and dissolved by the cryolite. To explain this action of the cryo- lite it is necessary to admit the formation of a lower fluoride of aluminium and sodium, such as I have recently proven the exist- * Chemiker Zeitung (Cothen), xi., p. 934 (1887). 372 ALUMINIUM. ence of.* The solution of the aluminium takes place according to the following reaction: Al^Fe.eNaF + Al = 3 (AlF2.2NaF) . If the electrolysis takes place at a temperature so low that the sodium separates out as a liquid (its volatilizing point is about 900°), large globules of aluminium will be produced, on which the cryolite seems to exert no appreciable action. Nevertheless, the yield of aluminium is much below the theoretical quantity set free. Since pure copper melts at 1050°, and aluminium bronze at 800°, the copper electrodes can remain unfused in the bath while the bronze melts off as it forms, while the tempera- ture can be low enough to keep the sodium in the liquid state. By mixing sodium or potassium chlorides with the cryolite, the melting point is lowered, or at a given temperature the bath is more fluid, and so easier to work. When there is not enough aluminium fluoride present in the bath to utilize all the sodium liberated, the excess of sodium may form an alloy with some aluminium, and rising to the surface, burn to waste. Since cry- olite always contains silica, as previously explained, the bronze thus obtained is always rendered hard with silicon, and is not of much value commercially.'' Hall's Process. Although Hall's patents were not issued by the patent office until 1889, yet they were applied for in the middle of 1886, and a commercial-sized plant was put up to work the process in 1888. Mr. Hall really discovered the principle on which his process is based, and made some aluminium by it, on a small scale, in February, 1886. *Chem. Zeit. (Cothen), xiii., p. I (1879). Hampe melted together aluminium and sodium fluorides in the proportions of one molecule of the first to four of the second, and obtained what is apparently a lower fluoride than cryolite, in which aluminium cannot be otherwise than diatomic, since analysis gives it the formula AlF2.2NaF. This salt is similar in appearance and properties to cryolite. As there are still some doubts, however, about this compound, the above explanation of the solution of alu- minium by the cryolite need not be accepted as final. REDUCTION OF AI,UMINIUM COMPOUNDS. 373 The inventor of this process, Charles M. Hall, of Oberlin, Ohio, born in 1863, is a graduate of Oberlin College, and while yet a student spent considerable time in experimenting on iso- lating aluminium with the electric current. Less than a year after leaving college, he conceived the following idea, which I quote in his own words : " It occurred to me that if I could find some stable solvent for alumina itself, which at a reasonable and practicable temperature would dissolve the alumina by the mere mingling of it with the solvent and allow the alumina so dissolved to be electrolyzed out of it, leaving the solvent unaf- fected, this would possibly be the best process which could be devised for the manufacture of aluminium by electrolysis." Many different salts were tried, to see if they possessed the property required, among them the fluorides of calcium, mag- nesium, sodium and potassium. These latter salts were the only ones which gave any encouraging results, but the first two were too hard to fuse, and they all dissolved only small quan- tities of alumina. Hall next tried cryolite, the natural com- pound of aluminium and sodium fluorides, and found that it melted at a red heat and readily dissolved considerable alumina. This was on February 10, 1886. On applying the electric cur- rent to this bath he was not immediately successful ; but, at- tributing the failure to the presence of silica in the crucible lining, he tried a crucible with a carbon lining, and the experi- ment was entirely successful. This was February 23, 1886, and on July 9, of the same year. Hall applied for patents covering his invention. P. L. V. Heroult, of Paris, France, had, however, apphed for a United States patent for substantially the same process on May 22, 1886, and the patent ofifice declared an interference and ordered both parties to give evidence as to the date of invention and putting into practice. Hall was able to name February 23, 1886, as the date on which he had put his inven- tion into practical operation, while Heroult named only the date of his French patent for the same invention, April 23, 1886. (See p. 386.) The result of these proceedings was 374 ALUMINIUM. that a patent covering the process was issued to Hall on April 2, 1889. (Number 400,766.) This patent has claims cover- ing the use of the following process : 1. Dissolving alumina in a fused bath composed of the fluorides of aluminium and a metal more electropositive than aluminium, and then passing an electric current through the fused mass. 2. Dissolving alumina in a fused bath composed of the fluorides of aluminium and sodium, and then passing an electric current, by means of a carbonaceous anode, through the fused mass. In the specification of the patent, it is stated that the bath preferred as a solvent contains : Sodium fluoride 33.2 per cent. Aluminium fluoride 66.8 per cent. represented by the formula AlFj.NaF. A convenient method of forming this bath consists in adding to the mineral cryolite 80.3 per cent, of its weight of aluminium fluoride, according to the formula : AlFs.sNaF + 2AIF3 = sCAlFs.NaF). It is further stated that the bath may be fused in a crucible or melting pot of iron or steel having a carbon lining, that the positive electrode may be of carbon, copper, platinum or any other suitable material, and the negative electrode a carbon rod or the carbon lining of the bath. When the positive electrode is carbon it is gradually consumed by the oxygen liberated, but when copper is used a coating of copper oxide is at once formed on it, which protects it from further oxidation and causes free oxygen to be liberated. The tension required to operate a bath is stated as 4 to 6 volts. The above description may be taken as summarizing Hall's process as developed by him at the date of application for his patent, July, 1886. It is the writer's opinion that credit should be given to both Hall and Heroult for originating this inven- REDUCTION OF ALUMINIUM COMPOUNDS. 375 tion, as the principle was discovered independently by each at very nearly the same time ; but in the subsequent development and practical application of the invention, Hall in America clearly outstripped Heroult in Europe. Several other patents were subsequently applied for by Hall, covering modifications of the original process, and these were all issued with the original patent in 1889.* One covers the use of a potassium-aluminium fluoride, AIF3.KF, instead of the corresponding sodium salt, since it is much more fusible. Also the addition of lithium fluoride to this salt. Another covers the use of calcium and aluminium fluorides to form the bath, such as 2AlF3.CaF2 or 2AlF3.3CaF2. Since this bath is of higher specific gravity than molten aluminium, it is recom- mended to add to it enough of the salt AIF3.KF to lower the specific gravity below that of the aluminium. This is unneces- sary if alloys of aluminium are to be made, in which case the metal to be alloyed is made the negative electrode and the alloy formed will be sufficiently heavy to sink. For making alloys, the addition of barium fluoride to the bath is recom- mended, as its high specific gravity is no inconvenience and it is more fusible than the calcium or strontium fluorides. In another of these patents, the bath specified has the formula 2(AlF3.3NaF) + aAlFj-CaFj, being made by melting together cryolite, aluminium fluoride and fluorspar. When the bath becomes clogged, by the settling out of a mushy deposit which stops the current, the addition of 3 or 4 per cent, of anhydrous calcium chloride is recommended as clearing or liquefying the bath ; this addition is also said to lessen the disintegration of the carbon anodes used. As at present conducted, the process is worked according to the original patent applied for in 1886, it having been found that almost all the difficulties which the subsequent modifica- tions were designed to overcome are entirely obviated by regu- lar working on a large scale. It has been concluded from * Numbers 400,664; 400,665; 400,666; 400,667; 400,766. 376 ALUMINIUM. subsequent experience that almost all the difficulties met at first were the results of the varying composition of the bath and its irregular temperature, and were inherent in attempts to work on a small scale. From June, 1887, to the middle of 1888, Mr. Hall experi- mented on his process at the Cowles' Bros, works at Lockport, N. Y. His results here, working on a small scale, were not sufficiently economical to induce that company to continue the work. Mr. Hall, however, was confident that if the process could be started on a large scale, aluminium could be made at a cost very much below its selling price at that time. Leaving Lockport, Mr. Hall went to Pittsburgh, and there, through the influence of Mr. Romaine C. Cole, was successful in interesting several capitalists, who contributed $20,000 in cash to put up a works, and in September, 1888, organized the Pittsburgh Reduc- tion Company, with a capital stock of $1,000,000. The con- struction of the plant was immediately begun, and in Novem- ber, 1888, aluminium was being produced at the rate of 50 pounds per day, which found a ready sale at $5 per pound, leaving a handsome profit. This plant was situated in Pittsburgh, and was operated by steam-power, using coal for fuel. The machinery consisted of two ordinary tubular boilers of sixty horse-power each, and a Westinghouse " automatic " engine of 125 horse-power, running two shunt-wound Westinghouse dynamos. These dynamos, running at 1,000 revolutions, gave each a current of 1,000 amperes at 25 volts tension, and being coupled in parallel gave a current of 2,000 amperes at full speed, or an average of 1,700 to 1,800 amperes at 16 volts on steady runs. This current was passed through two reducing pots, coupled in series. These pots were of cast-iron, 24 inches long, 16 inches wide and 20 inches deep, lined inside with a layer of hard-baked carbon 3 inches thick. From a copper bar above were suspended, by ^ inch copper rods, 6 to 10 three-inch carbon cylinders, each originally 15 inches long. Each pot. held 200 to 300 pounds of the electrolyte. REDUCTION OF ALUMINIUM COMPOUNDS. 377 It was found that with apparatus and current of this size, outside heating was not necessary; the heat generated by the passage of the current being sufficient to keep the bath fused at the proper temperature. Larger pots have since been used, which will be described later, but as the operation in them is exactly similar to that in the smaller ones, we will describe the process at once. The carbon lining of the pot forms the negative electrode, connection being made to the iron casing. The fluoride salts to form the bath are placed in the bottom of the cavity, the carbon positive electrodes lowered until they touch the carbon lining, and the current turned on. After a few minutes the salt is melted and when red-hot in the vicinity of each carbon, more salt is thrown around the carbons, or each carbon moved up a little. In an hour or two sufficient salt has been melted to form the bath, and the carbons have been brought out of direct contact with the lining. The bath is now ready to dissolve alumina, which is first sprinkled on top of the bath, and after it has become hot and perfectly dry is stirred in. The fumes which were arising from the decomposition of the fluorine salts immediately cease, the voltage absorbed by the bath falls, the number of amperes passing increases, and the electrolysis of the dissolved alumina commences at once. Powdered carbon (the stub ends of electrodes ground up) is now placed on top of the bath in a layer about an inch thick, serving to keep in the heat and so reduce the loss by radiation. The carbon electrodes are clamped to a copper bar extending the whole length of the pot (see Fig. 38), and if one part of the bath becomes cooler than it should be, the carbons are crowded together at that point and soon heat it up. In prac- tice, the ends of the carbons are kept about 0.5 to i inch from the lining, and each one carries about 250 to 300 amperes. If more current than this passes through a carbon, as might happen if it short-circuited, the copper rod becomes red-hot at its con- nection with the carbon. As soon as this is observed, the workman raises it slightly and so stops the extra current. The 378 ALUMINIUM. carbons wear down gradually until only 3 or 4 inches long (the depth of liquid bath is not over 6 inches) and must then be replaced. The consumption of carbons in regular running is less than one pound per pound of aluminium produced, show- ing that they are burnt according to the reaction AI.O, + 3C = 2AI + 3CO. in which 102 parts of alumina would require 36 parts of car- bon to combine with its oxygen, producing 54 parts of metal. Fig. 38. Theoretically, therefore, there is required || or ^ of a pound of carbon to i pound of aluminium produced. The smal'l amount over this actually used is consumed by the air with which they inevitably come in contact. In these small pots, a tension of 8 volts is required to oper- ate each, at an amperage of 1800. If the voltage rises to 10 or more, it indicates that the alumina in the bath has become exhausted, as is also shown by dense, irritating fluoride fumes. REDUCTION OF ALUMINIUM COMPOUNDS. 3/9 The workman at once stirs in some of the alumina which is always kept on top of the carbon covering, and the voltage immediately falls. A delicate electrical instrument, set to a certain voltage, gives immediate notice to the workman when the bath is " out of ore." In regular working no fumes arise, the carbon covering entirely conceals the red-hot fluid bath beneath, and one can only convince himself that the bath is really in operation by approaching and noticing the heat radiated. When aluminium has accumulated for several hours, it is ladled out with iron ladles well-rubbed with chalk or plumbago. This operation gives rise to some fumes, and also causes some of the electrolyte to be dipped out with the metal. It has been suggested that a tap-hole should be provided, but there was found great difficulty in keeping the pot tight when this was tried, and the expedient of syphoning out the metal has been found more practicable. The crude ingots thus poured are re-melted in large crucibles ; the re-melting plant is shown in Fig. 39. The alumina used in this plant was from the German manu- turer, Bergius, at Goldschmeiden, near Breslau, Silesia. As im- ported, it contained about 33 per cent, of moisture, which is driven off in a drying furnace. The cost of alumina was, in 1890, five cents a pound delivered in Pittsburgh, which would make the dried alumina cost 7.5 cents per pound plus the cost of calcining, which is not over 0.5 cent. If absolutely pure, alumina should contain 52.94 per cent, of aluminium, but as this calcined alumina usually contains about i per cent, of im- purities, chiefly silica, there is only a little over 52 per cent, of metal in it. An accurate account of several months' running showed that the Hall process extracts a fraction over 50 per cent, of metal from it. The alumina to furnish one pound of aluminium therefore cost in 1890 about 16 cents. Since then, the alumina is calcined in Germany before shipment, saving in freight and customs dues, and can probably be laid down now in New York at S cents per pound, making a cost of 10 cents per pound of aluminium. There is, besides this, a small waste 38o ALUMINIUM. of bath material, which costs in the neighborhood of 7 cents per pound to make, but since this does not in actual running amount to over 2 pounds per 100 pounds of aluminium pro- duced, this item of expense is quite small. The output of these small pots was about one pound of metal an hour from each, and they were kept in continued ope- ration for several weeks at a time. If pure alumina is used, Fig. 39. ,, "^^-^ /W''. pure aluminium is produced ; that made from Bergius' alumina averaging over 98 per cent. pure. When a bath has been put into operation, the metal first produced is contaminated with the silicon and iron present in the bath material, but in a few days these are completely elim- inated, and the bath material is almost chemically pure save for the impurities introduced in the alumina. If calcined, selected raw bauxite is used in the pots, the metal produced averages 94 to 96 per cent, pure, and is sold for REDUCTION OF ALUMINIUM COMPOUNDS. 38 1 use in iron and steel. Two analyses of such second quality- metal gave : Aluminium 94.16 9S'93 Silicon 4.36 2.01 Iron 1.48 2.06 As the material used only costs about i cent per pound ready to put into the pots, and about 2^ pounds make one of metal, this second quality metal costs about 7 cents less per pound than the first quality. An estimate of the cost of producing aluminium in this plant in 1889, at the rate of fifty pounds per day, is as follows: 100 lbs. calcined alumina @ 8 cts =. $8.00 Fluorides for bath @ 7 cts = .50 Carbons = i.oo 50 horse-power engine = 15.00 2 engineers @ $3.00 per diem = 6.00 6 workmen @ ;j2.oo " = 12.00 Superintendence, office expenses, etc .= 10.00 Interest on plant, rent, etc ^ 7.50 Cost of about 50 lbs. of aluminium $60.00 In the early part of 1890 the plant was greatly enlarged. The additions consisted of three Babcock and Wilcox boilers of 200 horse-power each, fired by natural gas ; two 200 Jiorse- power Westinghouse compound engines ; two shunt-wound Westinghouse dynamos running 325 revolutions per minute, connected in parallel and giving a total current of 5000 amperes at 50 volts tension. The conductors for this current were two copper bars, 6 inches by 0.5 inch, giving a total cross-section of 6 square inches. This gives a little over 800 amperes per square inch section. This current operated five large pots con- nected in series, averaging 9 volts to a pot. These large pots are of one-quarter inch wrought iron, 5 feet long, 2% feet wide and 2 feet deep, with a carbon lining 4 to 6 inches thick, and supported on bricks to keep the bottom cool. Above are two copper bars to which a double row of carbon electrodes are clamped, there being 10 on each row or 20 in all. Each of 382 ALUMINIUM. these pots produced 60 to 70 pounds of aluminium a day, mak- ing the production of the entire plant in 1890 about 400 pounds per day. The cost of aluminium, working on this scale, could scarcely have been over $0.75 per pound, since the metal made here was sold during 1891 for $1.00 per pound. During 1891, in order to obtain room to extend and cheapen fuel, the entire plant was moved to New Kensington, Pa., on the Allegheny River 18 miles from Pittsburgh. At this place the capacity of the plant has been greatly increased, there being ap- proximately 1500 horse-power employed, and the output having been increased to lOOO pounds per day in 1893 and to nearly 2000 pounds per day in 1894. Since the selling price has been reduced to $0.50 per pound, it is evident that the present cost cannot be much over $0.40, if so high. Captain A. E. Hunt, president of the company, is authority for saying that as the process is operated on an increasing scale, and more exper- ience is had in running it, the cost in the future will approxi- mate $0.20 per pound, the lowest limit by this process. In July, 1890, a plant to work Hall's process was put into operation at Patricoft, Lancashire, England, with a capacity of about 300 pounds of aluminium a day. This plant was in operation until 1894, when competition from Switzerland com- pelled it to close. During 1894, the United States Company have been con- structing a larger plant at Niagara Falls, being furnished power by the Niagara Falls Power Co. A contract has been made to take 6000 horse-power, and the plant, so far constructed, is as follows : * A 5000 horse-power turbine, in the Power Company's power- house, runs a 5000 horse-power, low frequency, alternating current Tesla dynamo. This machine, at full speed, gives two currents of 2500 volts by 775 amperes each, alternating 50 times per second. The exciting circuit is continuous, obtained from the main circuit by a rotary transformer, and amounts to only 0.2 per cent, of the main current. The total current of 2500 *This plant was put into operation on August 26, 1895. REDUCTION OF ALUMINIUM COMPOUNDS. 383 volts by 1550 amperes is conducted through an underground tunnel one-half mile to the aluminium works, through copper rope conductors, with a total section of 4.3 square inches, with a drop in potential of 12 volts. At the works, the current is first passed through a set of stationary transformers, each of 250 horse-power, in which the current is reduced from 2487 volts to 115 volts. The alternating current of 115 volts next passes to rotary transformers, each of 500 horse-power and taking the current from two stationary transformers. In these the alternating current of 115 volts is changed to a direct cur- rent of 160 volts, the quantity of current furnished by each rotary transformer being 2500 amperes. These currents of 2500 amperes by 160 volts are conducted to the pot room on copper bars with 1.25 square inch section, each passing through a separate switch-board, on which are shunt ammeters and vol- meters, and then passed to the pots. The buildings are all of iron, the main reduction room being 180 by 85 feet. It is not difScult to estimate what the output of the two works will be. At Pittsburgh each horse-power of electrical energy produced about 1.2 pounds of aluminium per day, at which rate a 5000 horse-power plant should make 6000 pounds, equiva- lent in round numbers to 1000 tons a year, the present value of which is $1,000,000. Reactions and efficiency of the process. — Taking the first small plant, a current of 1800 amperes in two vats should theoreti- cally produce 56.4 pounds of aluminium per day. As 50 pounds were obtained, on an average, the efficiency shown in this direction is nearly 90 percent. As only about 2.5 volts out of the 9 volts absorbed by the bath, is used in decomposing the alumina, wc have about 30 per cent, of the current thus utilized. The efficiency over all is therefore 90 per cent, of 30 per cent.=27 per cent. This means that the work of separat- ing aluminium from oxygen represents 27 per cent, of the actual energy of the current. The difference between 9 and 2.5, or 6.5 volts, is absorbed in the conduction resistance of the bath, being converted into heat. This would give a heat develop- 384 ALUMINIUM. ment of 6.25 X 1800x0.00024= 2.7 calories per second, or 9720 calories per hour. To this we may add the heat of oxidation of the carbon to carbonic oxide, and we have the total heat generated in the bath. A balance would show as follows : Heat Developed per Hour. By electrical resistances 9720 calories. Oxidation of the carbon 960 " Total 10680 " Heat Distribution per Hour. Heating 2 pounds alumina to 900° C 250 calories. Withdrawn with the aluminium 17S " Lost by radiation and conduction 10265 " Total 10680 As to the real reaction in the bath, by which aluminium is liberated, several metallurgists have taken the ground that the aluminium fluoride present is the substance primarily disso- ciated by the current, and that the fluorine set free at the anode immediately acts on the alumina present in solution and re- forms aluminium fluoride, liberating oxygen, which then unites with the carbon. According to this view the reactions are 2AIF3 + Current = 2AI + 6F. MO3 + 6F = 2AIF, + 3O. 3C + 3O = 3CO. This theory must assume either one of two things ; first, that the alumina added never becomes an integral part of the bath, but remains suspended mechanically; or, second, that if the alumina really is part of the bath, it is a stronger com- pound than aluminium fluoride, and therefore, the current decomposes the latter. This theory, however, involves several contradictions. If, for instance, alumina is really a stronger compound than aluminium fluoride, how could the gaseous REDUCTION OF ALUMINIUM COMPOUNDS. 385 fluorine decompose alumina, forming aluminium fluoride? Since gaseous fluorine can decompose alumina, as was proven by Moissan, it follows that alumina is therefore a weaker com- pound than aluminium fluoride, and that when an electric cur- rent is passed through a bath containing these two compounds the alumina is necessarily the first to be decomposed. The only refuge left for this theory is, then, to maintain that the alumina is not truly dissolved in the bath, but is only me- chanically suspended. This, however, is contrary to the way in which the bath behaves. Absorption of the fluorine could not possibly be as perfect in that case as it really is in practice. Besides, an experiment of Mr. Hall's settles the case, it seems to me, beyond question. On passing the current through an anode of clean copper, it becomes immediately coated with a layer of copper oxide. If fluorine were at all set free, it would be liberated in immediate contact with the anode, and copper fluoride must necessarily have been formed ; but no trace of that salt is observed. It thus appears impossible to me that the electric current does anything but dissociate oxygen from aluminium. It has been suggested that the alumina is dissolved in the bath by forming aluminium oxy-fluoride, and that this is the substance electrolyzed. This may or may not be true, but there is up to the present time no positive proof for the theory, and several circumstances against it. No chemist has as yet iso- lated and analyzed any such salt. If such salt is formed, the larger the proportion of aluminium fluoride in the bath, the more alumina it ought to dissolve. But cryolite contains 40 per cent, of aluminium fluoride, and dissolves at least 25 per cent, of its weight of alumina to a clear solution, while the salt AlFg.NaF, containing 66 per cent, of aluminium fluoride, and made by adding aluminum fluoride to cryolite, dissolves barely 10 per cent. Further, no evolution of heat or other signs of chemical action are observed when dissolving alumina in the bath. If such a salt exists in solution, the elements set free at the anode must be oxygen and fluorine, but it is already shown 25 386 ALUMINIUM. that no fluorine can be detected there even when using a cop- per anode. So, while the theory of an oxy-fluoride may be true, and facts unknown to us now may reconcile these appa- rent contradictions, yet at present there is no positive proof to give in its favor. In connection with this process, the following determinations by the writer of specific gravities, when cold and melted at a red heat, of the substances used in the bath, are of interest : * Cold, Molten after fusion. at a red heat. Commercial aluminium 2.66 2.54 Commercial cryolite from Greenland 2.92 2.08 Cryolite containing' all the alumina it can dissolve 2.90 2.35 Cryolite-faluminium fluoride forming the salt AlFj.NaF (Hall's preferred bath) .. . . 2.96 1 .97 Same as above, but containing all the alu- mina it can dissolve 2.98 2.14 SaltAlF3.KF 2.35 Powdered calcined alumina 3.60 H'eroiMs Processes. P. L. V. Heroult, of Paris, France, patented in 1886 the fol- lowing process, t Alumina is fluxed with cryolite, the bath be- ing contained in a carbon crucible serving as the negative electrode, which is placed inside a larger crucible and the space between filled with graphite. (Fig. 40.) The positive electrode is of carbon and dips into the fluid material. The negative elec- trode is of carbon, and connects with the graphite filling between two crucibles. A cover having holes for the electrodes is placed over the whole, and a layer of clay and loam packed on top of the cover. A current of only 3 volts will produce de- composition, and the alumina is alone decomposed, the cryolite remaining unaltered. The aluminium collects in the bottom of the crucible, and alumina is added from time to time to renew the bath. To prepare alloys, a negative electrode is made of * Journal of the Franklin Institute, July, 1894, p. 51. t French patent, 175,711; April 23, 1886. REDUCTION OF ALUMINIUM COMPOUNDS. 387 the metal to be alloyed, and dips into the bath, and as the current passes the alloy is formed and falls melted to the bottom of the crucible. A convenient strength of current for a crucible 20 centimetres deep by 14 centimetres in diameter inside, with a carbon anode 5 centimetres in diameter, is found to be 400 amperes, with an electro-motive force of 20 to 25 volts. The idea or principle involved in the above is exactly simi- FiG. 40. lar to Hall's process, and when Heroult applied for United States patents in 1886 the two claims interfered, and the evi- dence given in the patent ofHce showed Hall to be the prior in- ventor, so that the process in this country belongs entirely to Hall. (See Hall's process, p. 373.) It is evident that the pro- cess was discovered by these two inventors, on opposite sides of the ocean, at very nearly the same time, and entirely inde- pendent of each other. Hall, however, kept on improving his 388 ALUMINIUM. process until, in 1888, it was working on an industrial scale. Heroult, on the other hand, virtually abandoned his process for the time, and did not make any pure aluminium by it on a commercial scale until the end of 1889, at which time Hall had been selling aluminium for a year and Hall's patents had been issued over six months. It appears very much as if Heroult was not aware of the possibilities of his process until Hall's suc- cess showed the way. Meanwhile, Heroult had devised another method of produc- ing aluminium alloys, and successfully established it on a com- mercial scale. This process is as follows : * Pure alumina is melted by the intense heat of a powerful electric current, and then electrolyzed by the same current, using melted copper beneath the alumina as the cathode. The product is aluminium bronze. Alumina without copper or iron as a cathode cannot be electrolyzed to produce pure aluminium, as the metal produced would rise to the surface and be volatil- ized by the intense heat. The Societe Metallurgique Suisse, which acquired both of H^roult's patents, put up a plant to work the alloy process on a commercial scale in July, 1888. This firm had experimented some time with Dr. Kleiner's process, but abandoned it about the middle of 1887, to try H^roult's process, and with such successful results that the plant about to be described was de- cided on. The instalment consisted of two large dynamos con- structed especially for this work by the Oerliken Engineering Company, and directly coupled to a 300 horse-power Jonval turbine situated between them and mounted on a horizontal shaft. A separate dynamo of 300 amperes and 65 volts, driven by a belt from a pulley upon the main shaft, is used to excite the field magnets of the two large machies. These large dy- namos were originally intended to give each a current of 6000 amperes at 20 volts electro-motive force when running at 180 revolutions per minute, but sufficient margin was allowed in the * French patent, 1 70,003, April 15, 1887. English' patent, 7,426 (1887). U.S. patent, 387,876, August 14, 1888. German patent, 47,165, December 8, 1887. REDUCTION OF ALUMINIUM COMPOUNDS. 389 Strength of the field to be able to work to 30 volts. They have even worked up to 35 volts on unusual occasions without any- undue heating. It happens sometimes that the end of the anode touches the molten cathode, producing a short circuit, when the current will suddenly rise to from 20,000 to 25,000 amperes, without, however, damaging the machine. The main conductors are naked copper cables, about 10 cen- timetres diameter, and no special precautions are taken to insu- late them, since the current is of comparatively low potential, and a leakage of 100 amperes more or less in such a large cur- rent is too insignificant to take the trouble to avoid. An am- peremeter is placed in the main circuit, its dial being traversed by an index about i metre long, which is closely watched by the workman controlling the furnace. The furnace or crucible first used consisted of an iron box cast around a carbon block, the iron, on contracting by cool- ing, securely gripping the surface of the carbon on all sides, and thus insuring perfect contact and conduction of the current from the cathode inside. This method was found only suitable for small crucibles, and the next furnace was built up of carbon slabs held together by a strong wrought-iron casing. The in- terior depth of the crucible was 60 centimetres, length 50 and breadth 35 centimetres, which would permit the introduction of the carbon anode and leave a clear space of 4 centimetres all around it horizontally. At the bottom of the cavity is a passage to a tap-hole, D (Fig. 41), closed by the plug E, which is from time to time withdrawn to run ofT the alloy. The carbon anode, F, is suspended vertically above the crucible by pulleys and chains, which permit it to be raised and lowered easily and quickly. This anode is built up of large carbon slabs laid so as to break joints, and securely fastened together by car- bon pins. The whole bar is 250 centimetres long, with a section 43 by 25 centimetres, and weighs complete 255 kilos. The conductor is clamped to the anode by means of the cop- per plates, G. The crucible is covered on top by carbon slabs, H, H, 5 centimetres thick, leaving an opening just large enough 390 ALUMINIUM. for the anode to pass through. The openings, y, y, closed by the lids, K, K, serve for introducing fresh copper and alumina. The materials used have just been mentioned. Electrolytic or Lake Superior copper is used, the former being perhaps pre- ferred if from a good manufacturer. The alumina is bought as commercial hydrated alumina, costing in Europe 22 francs per 100 kilos (2 cents per lb.). This is, of course, calcined before using, each 100 kilos furnishing about 65 kilos of alumina. Corundum can be substituted for the artificial alumina ; some from North Carolina was tried, and is said to have given even more satisfactory results. Commercial bauxite has been used, but since it contains more or less iron its use is confined to the manufacture of ferro-aluminium. It is very cheap in Europe, and requires no other preparation than simple calcining. The operation is begun"! by placing copper, broken into rather small pieces, in the crucible. The carbon anode is then approached to the copper, which is quickly melted by the cur- rent. The bath of fluid copper then becomes the negative REDUCTION OF ALUMINIUM COMPOUNDS. 39 1 pole, and ore is immediately fed into the crucible. It also is soon melted and floats on top of the copper. The electrolysis now proceeds, care being taken that while the anode dips into the molten ore, it does not touch the molten cathode. Par- ticular stress is laid on the economy of keeping the distance between the electrodes small, the reason given being that "the space between, being filled with a layer of badly-conducting molten ore, offers a resistance which increases with the dis- tance ; and although resistance is necessary, in order that the current should produce heat, it is not economical to have more heat than is necessary to melt the ore — the work of separating the metal from the oxygen being chiefly done by the electro- lytic action of the current, and not by the high temperature." In practice, this intervening space is not over 3 millimetres (one-tenth of an inch). The workman in charge, by watching the indications of the amperemeter, is enabled to maintain the anode at its proper distance without any difficulty ; it is pro- posed to do this regulating automatically by means of an easily-constructed electrical device. The oxygen liberated gradually burns away the anode, it being found that about one kilo of the anode is consumed for every kilo of aluminium pro- duced. After the operation commences, the alumina and metal are introduced alternately in small quantities at frequent and regular intervals, and the alloy is tapped out about every twelve hours. The only wear to which the crucible is sub- jected is from the accidental admission of small quantities of air; this waste is scarcely appreciable. All oxygen evolved from the bath is evolved in contact with the anode and burns it. When the anode has worn down until too short for further use, it is replaced by another, the pieces of carbon left being utilized for repairing, covering or building up the crucible. The operation is kept up night and day, and it is generally more than a day after starting before the crucible is thoroughly up to its maximum heat and work. Two reliefs of five men each operate the plant, one to superintend, one to prepare 392 ALUMINIUM. and dry the alumina, a third to control the working of the cru- cible by regulating the anode, a fourth to feed ore and metal into the crucible, and the fifth to take care of the machinery, prepare anodes, crucibles, etc. All five work together to replace an anode or tap the crucible. A part of each tapping is analyzed, to determine its percentage of aluminium. It is the aim to produce as rich a bronze as possible at the first operation (over 42 per cent, of aluminium has been reached), and its subsequent dilution to any percentage desired is done in any ordinary smelting furnace. The average current supplied the crucible is 8000 amperes and 28 volts, requiring an expenditure of a little over 300 horse- power in the turbine. Starting cold it required, in one instance, 36 hours to produce 670 kilos of aluminium bronze containing 18.3 per cent, or 122.67 kilos of aluminium. Taking the cur- rent as 300 electric horse-power, this would be a return of 1 1 grammes per hour or 0.264 kilos (0.6 lbs.) per day for each electric horse-power. It is claimed by Mr. Heroult that the furnace takes several days to attain its full efficiency, and that when it does so the above charge can be worked in 12 hours, which would triple the above production per horse-power. This claim is backed by figures as to 271 hours of actual operation, during which time the crucible cooled several times, but the average over the whole period was 22^ grammes per hour or 0.544 kilo (1.2 lbs.) per day for each horse-power (163 kilos of aluminium per day, total production). During actual opera- tion at full efficiency, Mr. Heroult claims to get 35 to 40 grammes of aluminium per horse-power-hour, which would mean 11 to 15 horse-power-hours per pound of aluminium, or 1.75 to 2.1 lbs. of aluminium per horse-power per day. An idea of the percentage of the useful effect derived from the current may be had very easily by considering that i electric horse-power = 750 Watts = 644.4 calories of heat per hour. (See p. 302.) As each gramme of aluminium evolves 7.25 calories in forming alumina, the production of i electric horse- power in I hour (if its energy were utilized solely for separat- REDUCTION OF ALUMINIUM COMPOUNDS. 393 ing aluminium from oxygen) would be 88.88 grammes. Therefore the heat energy of the current is amply sufificient to account for all the alumina decomposed, leaving over the heat produced in the crucible by the union of oxygen with the car- bon anode. Looking at the other side of the question, the electrolytic action, we can easily calculate from the strength of the current what it could perform. A current of 8000 amperes can liberate 2.68 kilos of aluminium per hour,* ac- cording to the fundamental law of electro-deposition. If, then, from the figures given, there were actually produced 3.3 kilos and 6.8 kilos per hour, and 10.5 to 12 kilos are claimed when up to the full efficiency, it is impossible that more than a frac- tion of the aluminium is produced by electrolytic decomposition of alumina, and the claim that the process is essentially electro- lytic is without foundation. Similar calculations with the data given with regard to Cowles' process will lead to exactly similar conclusions, viz : that the absolute energy of the current, if converted into its heat equivalent, is many times more than sufficient to account for the decomposition of the alumina on thermal grounds, but the amount of current used will not suffice to explain the decomposition of the alumina as being electrolytic. Therefore, in both these processes, the oxygen is abstracted from alumina by carbon, the condition allowing this to take place being primarily the extremely high temperature and secondarily the fluidity of the alumina. The presence of copper is immaterial to the reduction, as is clearly shown in the Cowles process. In November, 1888, the AUgemeine Electricitat Gesellschaft of Berlin united with the Societe Electrometallurgique Suisse in purchasing the Heroult Continental patents and organizing the Aluminium Industrie Actien Gesellschaft, with a capital of 10,000,000 marks. Dr. Kiliani, the well-known electro- metallurgical expert, was made manager of the works. On his taking charge, a much larger plant was begun, including foundries and machine shops for casting and utilizing ten tons * N. B. Only one furnace was used on the circuit. 394 ALUMINIUM. of bronze which it was intended to produce daily. This plant, consisting of 8 crucibles, was put into operation in 1891, with a capacity of 1000 kilos of alloyed aluminium daily. About this time, Heroult in co-operation with Kiliani took up again his process for producing pure aluminium, stimulated thereto, no doubt, by the success of the Hall process in America. They found that by modifying slightly the shape of their crucibles .and using a bath of cryolite to dissolve the alumina, the operation could be practically carried on in their alloy type of furnace. The apparatus used for producing pure aluminium is shown in Fig. 42. It will be noticed that Fig. 42. the carbon lining is not needed so thick as in the alloy fur- naces, since the temperature' is so much lower; also that the entire lining is not taken as the negative electrode, but a nega- tive pole of carbon is inserted] through the bottom of the crucible. This is the form of apparatus now in use at the Swiss works, producing pure aluminium so cheaply that the alloy process is nearly abandoned. The plant at the Rhine Falls, as now operated, consists of- REDUCTION OF ALUMINIUM COMPOUNDS. 395 the 300 horse-power turbine used since 1888, two 600 horse- power turbines also of the Jonval type, put into operation in 1 89 1, and five other 610 horse-power turbines, four of which were put into operation in May, 1893, and the other a few months later. The water-rights obtained by the company in 1889 from the Canton Schaffhausen allowed it to take from the Rhine 20 cubic metres (700 cubic feet) of water per second, which at a fall of 20 metres gives an effect of 4000 horse- power. The combined power of the above turbines exceeds this, but one is always kept at rest and only seven regularly run. The turbines are worked with an upward current of water, and the dynamos are revolved horizontally like huge tops above the turbine-shafts. The 600 horse-power dynamos are of the Oerlikon make, and at 150 revolutions per minute give a steady current of 7500 amperes at a tension of 55 volts. The current is carried by massive copper conductors to the crucibles. This plant, working to its full capacity since the middle of 1893, turns out daily 2500 kilos (5500 pounds) of aluminium, equal to 900 metric tons, a year. It is said that this amount is not sufficient to supply the demand for the metal, and that the company contemplates acquiring a large water power at Rhein- felden, near Basle, and erecting there an even larger plant than their present one. In 1888 the Societe Electro-metallurgique Franfaise estab- lished a works at Froges (Isere), 12 miles from Grenoble, to manufacture aluminium alloys by the Heroult process. They commenced selling alloys in the early part of 1889, and soon after commenced making pure aluminium in the same manner as has been described at Neuhausen. Their plant consists of two turbines of 300 horse-power each, with two dynamos of 7000 amperes and 20 volts each, with an output estimated at 3000 kilos of alloys per day, which means 200 to 300 kilos of aluminium. There are ten crucibles, five of which are shown in Fig. 43. Each crucible requires about 10 volts to run it, and produces i to 1.2 kilos of aluminium per hour, with an ex- 396 ALUMINIUM. penditure of about 2 horse-power for each kilogramme pro- duced per day. The output during 1893 was 50,000 kilos of aluminium, over 97.5 per cent. pure. In 1893 this company acquired a large water power at La Praz, near Modane, and expected to be manufacturing alumin- ium there in 1894. The United States Aluminium Metal Co. was organized to Fig. 43. HEROULT ALLOY FURNACES AT FRI1GES, FR.ANCE. work the Heroult alloy process in this country. An experi- mental plant, under Mr. Heroult's personal direction, was started at Bridgeport, Conn., in July, 1889, but the dynamo proved inadequate, and was burnt out. A new one was ordered from the Oerlikon Works, Zurich, which arrived the following November, and was put to work early in 1890 at Boonton, N. J. This dynamo was driven by water-power, and at 220 revolutions gave a current of 3500 amperes at 35 volts tension. This current was sent through one crucible, shown in Fig. 44, producing aluminium bronzes and ferro-aluminium. This plant was only run for a few months, and no attempt has been made to enlarge it to an industrial scale. REDUCTION OF ALUMINIUM COMPOUNDS. 397 As the Neuhausen works are now (1895) selling aluminium at $0.35 per pound in large quantities, it is interesting to at- tempt to estimate what the cost is at present. They sell three quahties of aluminium, designating them as follows: — Flii. 44. A HERdULT FURNACE. CO.MrOSITION. Silicon. Iron. Aluminium. No. o 0.06 0.04 99.90 fO.lS 0.21 99.61 No. I '^ 1 0.51 0.34 99.33 N0.2 1't ''^^ ""^V 1 3-82 3.34 92.84 The above price is for No. i metal. In fact, the cost of these 398 ALUMINIUM. different grades differs only in the cost of the raw material, all other expenses being the same. Making calculations on No i grade, the cost at Neuhausen is probably as follows per kilo of aluminium : — 2 kilos calcined alumina, @ fr. 0.40 0.80 francs. 0.3 kilos cryolite, @ fr. 0.75 0.25 " 1.2 kilos carbon electrode, @ fr. 0.30 0.35 " Power — 40 H. P., hours 0.15 " Labor and superintendence o-3S " General cost, repairs, etc 0.50 " 2.40 " The cost of No. i aluminium at Neuhausen is therefore at present about 2.50 francs per kilo, or 23 cents per pound. The additional cost of alumina for making No. O metal is prob- ably 0.60 francs, and the lower cost of No. 2 metal, due to using raw bauxite, about 0.40 francs. One of the ofiScers of the company is quoted as saying that they could make No. i aluminium for 2 francs per kilo if working a plant producing 10,000 kilos per day. A plant of such a size is one of the pos- sibilities of the next five years. Faure's Proposition. Camille A. Faure, whose process of making aluminium chloride is described on p. 166, proposes to obtain the metal therefrom by electrolysis, using carbon electrodes. M. Faure states that if the process is carried out on a large scale the chlorine set free can be utilized to form bleaching powder, and will thus nearly repay the whole cost of manufacturing the alu- minium. Patents have been applied for, covering the details of the electrolytic apparatus. The inventor states that he has de- termined on a large scale that anhydrous, molten aluminium chloride can be practically decomposed at 300° C. by an electro- motive force of 5 volts, which comprises the force required for actual decomposition and also that required to overcome the resistance of the bath. At this rate, it would require an expen- diture of 840 horse-power to produce 1000 kilos of aluminium REDUCTION OF ALUMINIUM COMPOUNDS. 399 per day, which is about twice as efficient as present processes ; but Mr. Faure bases his ideas of economy entirely on the value of the bleaching powder obtained. He is sanguine of being eventually able, if working on a sufficiently large scale, to make aluminium at five cents per pound, and is still experimenting in his laboratory at Grenoble. Winkler's Patent. August Winkler,* of Gorlitz, proposes to electrolyze a fusible phosphate or borate of aluminium. This bath is made by melting alumina or kaolin with phosphoric or boracic acid, the proportions being such that the acid is saturated ; the separa- tion of aluminium will not be hindered if alumina is added continually to combine with the acid set free. Carbon elec- trodes are used. Willson's Process. Mr. Willson, organizer of the Willson Aluminium Company, of Brooklyn, N. Y., has patented the reduction of aluminium alloys in an electrical furnace, as follows : The negative elec- trode is a graphite crucible resting on a carbon slab to which connection is made. The positive electrode is a hollow carbon rod, passing through a hole in the cover. The operation is similar in every respect to Heroult's alloy process (p. 390), ex- cepting that reducing gases, as illuminating gas, are passed into the crucible through the hollow anode during the operation, and it is stated that the anode does not touch the molten material beneath. Copper and corundum are charged, and alloys with 3 to 18 per cent, of aluminium are made. It is claimed that the reducing gases perform the larger part of the reduction, and in addition prevent the wasting away of the carbon anode. A larger dynamo was constructed to work this process, and the plant erected at Spray, N. C, near the corundum deposits, but very little of the alloy has found its way into the market. * German Patent, 45,824, May 15, 1888. 400 ALUMINIUM. Grabau's Process* This process proposes the electrolysis of a bath composed of aluminium fluoride and caustic soda or potash or their carbon- ates. The particular advantages claimed are that the alumin- ium fluoride is procurable very pure by the inventor's chemical processes (see p. 172), also that the alkaline salts are easily procurable free from iron and silica, and if the operation is con- ducted in a properly-constructed crucible, very pure aluminium can be made. The electricity is supposed to break up the alu- minium fluoride, the fluorine attacking the alkali forming an alkaline fluoride, while the carbonic acid is driven off as gas. If an excess of aluminium fluoride is used, cryolite will be left in the bath, which can be sold as a by-product. It does not seem probable that this process can ever compete in cheapness with those based on the direct electrolysis of alumina, nor make purer metal than can be made by the others with a little extra care. Bucherer's Process. \ This inventor claims the electrolysis of the double sulphides of aluminium and an alkaline or alkaline-earth metal, mixed with molten halogen salts. The double sulphide is made by melting alumina with an alkaline polysulphide, sulphur and carbon according to the reaction 3Na,S + AlA + 3C + 3S = Al,S3.3Na,S4-3CO. This double sulphide dissolves easily in a fused bath of alka- line or alkaline-earth chlorides or fluorides ; for instance, molten sodium and potassium chlorides work well either alone or to- gether. The bath needs only a feeble current to electrolyze it, and produces very pure aluminium. While these claims may be all true, yet it appears that con- siderable expense would be incurred in making the sodium * German Patent, 62851, June 13, 1891. t German Patent, 63995, 1892. REDUCTION OF ALUMINIUM COMPOUNDS. 4OI polysulphide and in taking care of the sodium sulphide accum- ulating in the bath. Pure alumina would have to be provided, to start with, and the additional expense for chemicals is all in- curred to save say 50 per cent, of the electrical power used in other processes. It does not appear that the process will be as cheap as those based on the direct electrolysis of alumina. Another Sulphide Process. The Aluminium Industrie Actien-Gesellschaft of Neuhausen have taken out the German patent. No. 68909, in 1892. This patent claims the electrolysis of aluminium sulphide dissolved in a bath of alkaline or alkaHne-earth chlorides or fluorides, being kept molten during electrolysis by the electrical heat. The current needed for the bath is 2.5 to 3 volts if melted by exterior heat, 5 volts if melted by the internal heating of the current. As particular advantages are claimed^ 1 . The carbon electrode is not destroyed, it being at a lower temperature than that at which carbon and sulphur combine. 2. The small voltage required (theoretically, less than i volt is needed for decomposition). 3. The aluminium sinks readily in the bath, avoiding short circuits. 4. The sulphur set free can be condensed and used over in making the aluminium sulphide. 26 CHAPTER XII. REDUCTION OF ALUMINIUM COMPOUNDS BY OTHER MEANS THAN SODIUM OR ELECTRICITY. No very exact classification of these numerous propositions can be made, since often many reducing agents are claimed in one general process. Where such general statements are made, the method will be found under the most prominent reducing •agent named, with cross references under the other headings. Reduction by Carbon without the Presence of other Metals. About the first attempt of this nature we can find record of is the following article by M. Chapelle:* — " When I heard of the experiments of Deville I desired to repeat them, but having neither aluminium chloride nor sodium to use I operated as follows : I put natural clay, pulverized and mixed with ground sodium chloride and charcoal, into an ordi- nary earthen crucible, and heated it in a reverberatory furnace, with coke for fuel. I was not able to get a white heat. After cooling, the crucible was broken, and gave a dry pulverulent scoria, in which were disseminated a considerable quantity of small globules about one-half a millimetre in diameter, and as white as silver. They were malleable, insoluble in nitric or cold hydrochloric acid, but at 6o° C. dissolved rapidly in the latter with evolution of hydrogen ; the solution was colorless, and gave with ammonia a gelatinous precipitate of hydrated alumina. My numerous occupations did not permit me to assure myself of the purity of the metal. Moreover, the ex- periment was made under conditions which leave much to be * Compt. -Rendus, 1854, vol. xxxviii., p. 358. (402) REDUCTION OF ALUMINIUM COMPOUNDS. 403 desired, but my intention is to continue my experiments, and especially to operate at a higher temperature. In addressing this note to the Academy I but desire to call the attention of chemists to a process which is very simple and susceptible of being improved. I hope before many days to be able to ex- hibit larger globules than those which my first experiment furnished." M. Chapelle never did address any further communications to the Academy on this subject, and we must presume that further experiments did not confirm these first ones. The author was once called upon to examine a slag full of small, white metallic globules, the result of fusing slate-dust in a similar manner to M. Chapelle's treatment of clay. They proved to be globules of siliceous iron reduced from the iron oxide present in the slate. It is not impossible that Chapelle's metallic globules were something similar in composition to these. G. W. Reinar* states that the pyrophorous mass, which results from igniting potash or soda alum with carbon, contains a carboniferous alloy of aluminium with potassium or sodium, from which the alkaline metal can be removed by weak nitric acid. The manager of an aluminium company in Kentucky claims to produce pure aluminium by a process which the newspapers state consists in smelting down clay and cryolite in a water- jacketed cupola reducing furnace, it being also stated that the aluminium is reduced so freely, and gathers under the slag so well, that it is tapped from the furnace by means of an ordinary syphon-tap. These are all the particulars which have been made public. As to whether this company really does make aluminium by any such process I am unable to assert; pure aluminium has been sold by this company, but that it was made by this company, or by any such process, is very doubtful. O. M. Thowless,t of Newark, N. J., proposes to prepare a * Wagner's Jahresb., 1859, p. 4. t U. S. Patent, 370,220, Sept. 20, 1887. English Patent, 14,407 (1886). 404 ALUMINIUM. solution of aluminium chloride by dissolving precipitated alu- minium hydrate in hydrochloric acid. The solution is con- centrated and mixed with chalk, coal, soda, and cryolite, and the mass resulting heated in closed vessels to a strong, red heat. It is also stated that aluminium fluoride may be used instead of the chloride. The resulting fused mass is powdered and washed, when it is said, that aluminium is ob- tained in the residue. According to a patent granted to Messrs. Pearson, Liddon, and Pratt, of Birmingham,* an intimate mixture is made by grinding together — lOO parts cryolite. 50 " bauxite, kaolin or aluminium hydrate. 50 " calcium chloride, oxide or carbonate. 50 " coke or anthracite. These are heated to incipient fusion in a carbon-lined furnace or crucible for two hours, when the aluminium is said to be produced and to exist finely disseminated through the mass. ' A mixture of 25 parts each of potassium and sodium chlorides is then to be added and the heat raised to bright redness, when the aluminium collects in the bottom of the crucible. A better utilization of the fine powder is effected by washing it, drying, and then pouring fused zinc upon it, which alloys with the alu- minium and can be afterwards removed by distillation. If melted copper is used, a bronze is obtained. H. Bessemer, jr., of Westend,t tries to utilize the principle of combustion under pressure in order to get a temperature high enough to reduce alumina by carbon or a hydrocarbon gas, the resulting aluminium vapor being rapidly cooled by passing the products of the reaction through a small aperture into a large chamber, the expansion cooling and condensing the vapor. To conduct the process, an intimate mixture of alumina and carbon is made into briquettes and put into a * English Patent, 5,316, April 10, 1888. t English Patent, 12,033, J"ly 29, 1889. REDUCTION OF ALUMINIUM COMPOUNDS. 405 Strong iron vessel having a refractory lining and water-cooled externally. Air heated in regenerative stoves and gaseous fuel are forced into it at a pressure of three to four atmos- pheres. A very high temperature is produced, sufficient it is claimed to reduce the alumina. The products of combustion and metallic vapor pass out through a fire-clay tube of small size into a larger chamber, in which the aluminium vapor condenses. This process appears imaginary. Heating up the inside of such a large vessel, water-cooled externally, to a temperature sufficient to cause aluminium vapor to distil out of it, is ex- tremely problematical, especially with the means of heating employed. Reduction by Carbon and Carbon Dioxide. J. Morris,* of Uddington, claims to obtain aluminium by treating an intimate mixture of alumina and charcoal with car- bon dioxide. For this purpose, a solution of aluminium chloride is mixed with powdered wood-charcoal or lampblack, then evaporated till it forms a viscous mass which is shaped into balls. During the evaporation hydrochloric acid is given off. The residue consists of alumina intimately mixed with carbon. The balls are dried, then treated with steam in appro- priate vessels for the purpose of driving off all the chlorine, care being taken to keep the temperature so high that the steam is not condensed. The temperature is then raised so that the tubes are at a low red heat, and dry carbon dioxide, CO2, is then passed through. This gas is reduced by the car- bon to carbonic oxide, CO, which now, as affirmed by Mr. Morris, reduces the alumina. Although the quantity of car- bonic oxide escaping is in general a good indication of the pro- gress of the reduction, it is, nevertheless, not advisable to continue heating the tubes or vessels until the evolution of this gas has ceased, as in consequence of slight differences in the consistency of the balls some of them give up all their carbon * Dingier, 1883, vol. 259, p. 86. German Patent, No. 22,150, August 30, 1882. 406 ALUMINIUM. sooner than others. The treatment with carbon dioxide lasts about thirty hours when the substances are mixed in the pro- portion of s parts carbon to 4 parts alumina. Morris states further that the metal appears as a porous spongy mass, and is freed from the residual alumina and particles of charcoal either by smelting it, technically " burning it out," with cryolite as a flux, or by mechanical treatment. To produce any aluminium at all by such a process and at such a low temperature, appears to me impossible. Mr. P. A. Emanuel, of Aiken, S. C, had the idea of produc- ing aluminium sulphide by passing carbon bi-sulphide vapor over aluminium sulphate, and then reducing it by carbonic oxide. The reactions proposed would be A1,(S04)«-I- 4CS, - A1,S3 + 4COS + 4SO, MS, + 3CO = 2AI + 3COS. It seems to me that the first reaction would be very likely to occur, because alumina alone would form the sulphide under the same conditions. The reduction equation, however, is very problematical. We do not know that carbon oxysulphide would be produced by these substances, but even if it might be formed, the reaction is thermally negative to an extent which would render a high temperature necessary. In fact, the heat deficit of the reaction is as follows : Calories. Calories. Decomposition of AljSj 124400 Decomposition of 3CO 87000 21 1400 Formation of 3COS i 148100 Deficit 63300 The reaction may possibly occur at a high temperature, but I have no information that it has been experimentally accom- plished. Reduction by Hydrogen. F. W. Gerhard * decomposes aluminium fluoride or cryolite * Watts' Dictionary, article " Aluminium." REDUCTION OF ALUMINIUM COMPOUNDS. 4O7 by subjecting them to hydrogen at a red heat. The aluminium compound is placed in a number of shallow dishes of glazed earthenware, each of which is surrounded by a number of other dishes containing iron filings. These dishes are placed in an oven previously heated to redness, hydrogen gas is then admit- ted and the heat increased. Aluminium then separates, hydro- fluoric acid, HF, being formed, but immediately taken up by the iron filings, and thereby prevented from reacting on the aluminium. To prevent the pressure of the gas from becoming too great, an exit tube is provided, which may be opened or closed at pleasure. This process, patented in England in 1856, No. 2920, is ingenious, and some one said that it yielded good results. The inventor, however, returned to the use of the more costly reducing agent, sodium, which would seem to imply that the hydrogen method had not quite fulfilled his expec- tations. (See also Comenge's processes.) Quite recently the possibility of reducing alumina by hydro- gen has been very neatly proven by Mr. H. Warren.* He took a tube of fine-quality compressed lime and put into it alumina, made by evaporating a solution of aluminium chloride to dryness and calcining. He then passed pure, dry hydro- gen gas through the tube, heating the outside with an oxyhy- drogen blow-pipe flame, concentrating all the heat on one spot. With a slow current of hydrogen there was no reduction, but with a brisk current some water was formed, and there were found, on cooling the tube and breaking it, distinct metallic beads around the space of greatest heating. These were de- tached, and found on examination to be pure aluminium. A mixture of alumina and copper oxide readily gave under these conditions aluminium bronze. Oxides of tungsten and manga- nese were likewise reduced, but magnesia, silica and titanic oxide were not affected. * Chemical News, August 31, 1894, p. 102. 408 aluminium. Reduction by Carburetted Hydrogen. Mr. A. L. Fleury,* of Boston, mixes pure alumina with gas- tar, resin, petroleum, or some such substance, making it into a stiff paste which may be divided into pellets and dried in an oven. They are then placed in a strong retort or tube which is lined with a coating of plumbago. In this they are exposed to a cherry-red heat. The retort must be sufficiently stong to stand a pressure of from 25 to 30 lbs. per square inch, and be so arranged that by means of a safety valve the necessary amount of some hydrocarbon may be introduced into the re- tort among the heated mixture, and a pressure of 20 to 30 lbs. must be maintained. The gas is forced in by a force pump. By this process the alumina is reduced, the metal remaining as a spongy mass mixed with carbon. This mixture is remelted with metallic zinc, and when the latter has collected the alu- minium it is driven off by heat. The hydrocarbon gas under pressure is the reducing agent. The time required for reduc- ing 100 lbs. of alumina, earth, cryolite, or other compound of aluminium, should not be more than four hours. When the gas can be applied in a previously heated condition as well as being strongly compressed, the reduction takes place in a still shorter period. Nothing is now heard of this process, and it has been pre- sumably a failure. It is said that several thousand dollars were expended by Mr. Fleury and his associates without making a practical success of it. We should be glad to hear in the future that their sacrifices have not been in vain, for the pro- cess has possibilities in it which may some time be realized. Petitjean f states that aluminium sulphide, or the double sul- phide of aluminium and sodium (see p. 177), may be reduced by putting them into a crucible or retort, through the bottom of which is passed a stream of carburretted hydrogen. Some solid or liquid hydrocarbon may be placed in the bottom of the * Chemical News, June, 1869, p. 332. tPolytechnisches Central Blatt., 1858, p. 888. REDUCTION OF ALUMINIUM COMPOUNDS. 409 crucible. The aluminium is said to be thus separated from its combination with sulphur. The powder must be mixed with metallic filings, as iron, and melted in order to collect the alu- minium. Or, metallic vapor may be passed into the retort in place of carburetted hydrogen. Messrs. Reillon, Montague, and Bourgerel* patent the pro- duction of aluminium sulphide (see p. 177) and its reduction by carburetted hydrogen exactly as above. Lebedeff-f fluxes alumina in a graphite crucible with fluor- spar, adding a double fluoride of aluminium and sodium to re- duce the specific gravity of the bath, exactly as in the present electrolytic processes. A reducing gas, as hydrogen or a hydrocarbon, is then to be led into the crucible. This method of reducing alumina has appeared so promising to me, that, at my suggestion. Dr. Lisle, of Springfield, Ohio, made some experiments of this kind, using natural gas as the reducing agent. A graphite crucible was lined with carbon, and cryolite melted in it. Alumina was then dissolved in the bath until the cryolite was saturated. A current of heated natural gas (90 parts methane to 10 parts hydrogen) was then passed through for several hours, the temperature being a bright red. No evidences of reduction were observed. The experiment was also modified by passing in carbonic oxide, with a like result. Although these experiments were fruitless, yet I do not think that all the po.«sibilities have been exhausted, and I heartily recommend this as a promising field for further experiment. R. E. Green, of Southall, England, | modified the experiment by filling a retort with charcoal and then placing the alumina fluxed with cryolite on top. On heating, the molten salt trickles down over the carbon, while a reducing gas, hydrogen or a hydrocarbon, is sent upwards through the retort from an aperture below. Mr. Green, however, spoils his process and * English Patent, 4576, March 28, 1887. t German Patent, 57768 (1889). J English Patent, 5914, April 6, 1889. 410 ALUMINIUM. incidentally shows his ignorance of the properties of aluminium, by recommending the addition of silica to the alumina, or the use of some silica to make a slag. I might have been inclined to believe that some aluminium could have been produced in this retort, provided it had a carbon lining, but the addition of silica would render such" a result very unlikely, or in any event, a worthless metal would be obtained. Reduction by Cyanogen. According to Knowles' patent,* aluminium chloride is re- duced by means of potassium or sodium cyanide, the former, either fused or in the form of vapor, being brought in contact with either the melted cyanide or its vapor. The patent further states that pure alumina may be added to increase the product The proportions necessary are in general — 3 equivalents of aluminium chloride. 3 to 9 " potassium or sodium cyanide. 4 to 9 " alumina. Corbelli, of Florence,! patented the following method in England : Common clay is freed from all foreign particles by washing, then well dried. One hundred grammes of it are mixed with six times its weight of concentrated sulphuric or hydrochloric acid ; then the mixture is put in a crucible and heated to 400° or 500° C. The mass resulting is mixed with 200 grammes of dry yellow prussiate of potash and 1 50 grammes of common salt, and this mixture heated in a crucible to white- ness. After cooling, the reduced aluminium is found in the bottom of the crucible as a button. According to Deville's experiments, this process will not give any results. Watts remarks that any metal thus obtained must be very impure, consisting chiefly of iron. Lowthian Bell J attempted to obtain aluminium in his labora- * Sir Francis C. Knowles, English Patent, 1857, No. 1742. t English Patent, 1858, No. 142. J Chemical Reactions in Iron Smelting, p. 230. REDUCTION OF ALUMINIUM COMPOUNDS. 4II tory by exposing to a high heat in a graphite crucible mixtures of alumina and potassium cyanide, with and without carbon. In no case was there a trace of the metal discovered. Reduction by Double Reaction. M. Comenge,* of Paris, produces aluminium sulphide (see p. 177) and reduces it by heating it with alumina or aluminium sulphate in such proportions that sulphurous acid gas and alu- minium may be the sole products. The mixture is heated to redness on the bed of a reverberatory furnace, in an unoxidiz- ing atmosphere, the reaction being furthered by agitation. It is stated that the resulting mass may be treated in the way commonly used in puddling spongy iron, and afterwards pressed or rolled together. The reactions involved would be, if they occurred, AI2S3 + 2 AI2O3 = 6 Al + 3SO,. A\& + Al2(S04)3 = 4Al + 6S0,. It is also claimed that metallic alloys may be prepared by the action of metallic sulphides on aluminium sulphate ; as, for instance — Al,(S04)3 + 3FeS = Al2Fe3-h 6SO2. The sulphide is also reduced by hydrogen, iron, copper or zinc, the reactions being A1,S3 + 6H=2A1-|-3H2S. Al2S3 + 3Fe = 2Al + 3FeS. In the case of reduction by a metal, alloys are formed. Mr. Niewerth's f process may be operated in his newly in- vented furnace, but it may also be carried on in a crucible or other form of furnace. The furnace alluded to consists of three shaft furnaces, the outer ones well closed on top by iron covers, and connected beneath by tubes with the bottom of the middle * English Patent, 1858, No. 461, under name of J. H. Johnson. fSci. Am. Suppl., Nov. 17, 1885. 412 ALUMINIUM. one : the tubes being provided with closing valves. These side-shafts are simply water-gas furnaces, delivering hot water- gas to the central shaft, and by working the two alternately supplying it with a continuous blast. The two producers are first blown very hot by running a blast of air through them with their tops open, then the cover of one is closed, the blast shut off, steam turned on just under the cover, and water-gas immediately passes from the tube at the bottom of the furnace into the central shaft. The middle shaft has meanwhile been filled with these three mixtures in their proper order: — First: A mixture of sodium carbonate, carbon, sulphur and alumina. Second : Aluminium sulphate. Third : A flux, preferably a mixture of sodium and potassium chlorides. This central shaft must be already strongly heated to com- mence the operation ; it is best to fill it with coke before charg- ing, and as soon as that is hot to put the charges in on the coke. Coke may also be mixed with the charges, but it is not necessary. The process then continues as follows : The water- gas enters the bottom of the shaft at a very high temperature. These highly heated gases, carbonic oxide and hydrogen, act upon the charges so that the first breaks up into a combina- tion of sodium sulphide and aluminium sulphide, from which, by double reaction with the second charge of aluminium sul- phate, free aluminium is produced. As the latter passes down the shaft, it is melted and the flux assists in collecting it, but is not absolutely necessary. Instead of producing this double sulphide, pure aluminium sulphide might be used for the first charge, or a mixture which would generate it ; or again pure sulphide of sodium, potassium, copper, or any other metallic sulphide which will produce the effect alone, in which case alu- minium is obtained alloyed with the metal of the sulphide. Instead of the first charge, a mixture of alumina, sulphur and carbon might be introduced. Or the aluminium sulphate of the second charge might be replaced by alumina. So one REDUCTION OF ALUMINIUM COMPOUNDS. 413 charge may be sulphide of sodium, potassium or any other metallic sulphide, and the second charge may be either alumina or aluminium sulphate. Messrs. Pearson, Turner, and Andrews* claim to produce aluminium by heating silicate of alumina or compound sili- cates of alumina and other bases with calcium fluoride and sodium or potassium carbonate or hydrate, or all of these to- gether. If other metals are added, alloys are obtained. G. A. Faurie,f of St. Denis, France, claims that by making an intimate mixture of alumina with carbon, moistening with sulphuric acid (thereby producing some sulphate) and in- tensely igniting the mass, aluminium is reduced, and globules of aluminium picked out of the resulting powder. Another metal may be added to produce an alloy. Reduction in Presence of or by Copper. Calvert and Johnson f obtained copper alloyed with alu- minium by recourse to a similar chemical reaction to that em- ployed to get their iron-aluminium alloy. Their mixture was composed of — 20 equivalents of copper 640 parts. 8 (24) " aluminium chloride 1076 " 10 " lime 280 " "We mixed these substances intimately together, and after having subjected them to a high heat for one hour we found at the bottom of the crucible a melted mass covered with cuprous chloride, Cu^Clj, and in this mass small globules, which on analysis contained 8.47 per cent, aluminium, corresponding to the formula — 5 equivalents of copper 160 9i'96 per cent. 1 " " aluminium 14 8.04 " 100.00 ♦English Patent, 12332, Sept. 12, 1887. tU. S. Patent, July 22, 1890. X Phil. Mag. 1855, X. 242. 414 ALUMINIUM. " We made another mixture of aluminium chloride and cop- per in the same proportions as above, but left out the lime. We obtained an alloy in this case also, which contained 12.82 per cent, aluminium, corresponding to the formula — 3 equivalents of copper 96 87.27 per cent. I " "aluminium 14 12.73 " M. Evrard,* in order to make aluminium bronze, makes use of an aluminous pig-iron. (It is not stated how this alumin- ous pig-iron is made.) This is slowly heated to fusion, and copper is added to the melted mass. Aluminium, having more affinity for copper than for iron, abandons the latter and com- bines with the copper. After the entire mass has been well stirred, it is allowed to cool slowly so as to permit the bronze, which is heavier than iron, to find its way to the bottom of the crucible. M. Evrard makes silicon bronze in the same way by using siliceous iron. Benzont has patented the reduction of aluminium with cop- per, forming an aluminium-copper-alloy. He mixes copper, or oxidized copper, or cupric oxide, in the finest possible state, with fine, powdered, pure alumina and charcoal, preferably animal charcoal. The alumina and copper or copper oxide are mixed in equivalent proportions, but an excess of charcoal is used. The mixture is put in a crucible such as is used for melting cast-steel, which is lined inside with charcoal. The charge is covered with charcoal, and the crucible subjected first to a temperature near the melting point of copper, until the alumina is reduced, and then the heat is raised high enough to melt down the alloy. In this way can be obtained a succession of alloys, whose hardness and other qualities depend on the percentage of aluminium in them. In order to obtain alloys of a certain composition, it is best to produce first an alloy of the highest attainable content of aluminium, to analyze it, and then * Annales du Genie Civil, Mars, 1867, p. 189. t Eng. Pat. 1858, No. 2753. REDUCTION OF ALUMINIUM COMPOUNDS. 415 melt it with the required quantity of copper. The same pro- cess can be used for the reduction of alumina with iron or ferric oxide, only the carbon must in this case be in greater excess, and a stronger heat kept up longer must be used than when producing the copper-aluminium alloy. In contact with ferric oxide the alumina is more easily reduced than with the metallic iron. Benzon further remarks that some of these alloys, as the ferro-aluminium, may be subsequently treated so as to separate out the metallic aluminium ; also that the iron alloy may be mixed with steel in the melting pot, or suitable proportions of alumina and carbon may be put into the melting pot. The iron alloy may be useful for many purposes, especially in the manu- facture of cast-steel. The question opened up by Benzon's statements is whether carbon reduces alumina in presence of copper. This has been the subject of many careful experiments, and the verdict of the most reliable observers is that at ordinary furnace temperatures it does not. This principle has been the subject of numerous patents, and before presenting the negative evidence on this point we will review the claims made in these patents. G. A. Faurie * states that he has succeeded in obtaining alu- minium bronze by taking two parts of pure, finely-powdered alumina, making it into a paste with one part of petroleum, and then adding one part of sulphuric acid. When the yellow color is uniform and the mass homogeneous, sulphur dioxide begins to escape. The paste is then wrapped up in paper and thrown into a crucible heated to full redness, where the petro- leum is decomposed. The calcined product is cooled, powdered and mixed with an equal weight of a metal in powder, e. g., copper. This mixture is put into a graphite crucible and heated to whiteness in a furnace supplied with blast. Amidst the black, metallic powder are found buttons of aluminium alloy. In an English patent,! by Mr. Faurie, it is further ♦Comptes Rendus, 105, 494; Sept. 19, 1887. t English patent 10,043, -^"g- '^i J887. 41 6 ALUMINIUM. claimed that by making bricks out of the calcined alumina mixture and alloying metal, and using similar bricks of lixi- viated soda ashes mixed with tar for flux, the reduction can be effected in a cupola. Bolley,* at his laboratory in Zurich, and List.f at the royal foundry at Augsburg, have shown that by following the process claimed by Benzon the resulting copper contained either no aluminium, or at most a trace. In an experiment made by the author to test this point — 40 grammes of copper oxide and copper, 5 " alumina, 5 " charcoal, were intimately mixed and finely powdered, put in a white-clay crucible and covered with cryolite. The whole was slowly heated to bright redness, and kept there for two hours. A bright button was found at the bottom of the crucible. This button was of the same specific gravity as pure copper, and a qualitative test showed no trace of aluminium in it. A friend of mine. Dr. Lisle, has repeated this experiment, taking the metal produced and returning it to another operation and re- peating this four times, but the resulting button scarcely showed a trace of aluminium. Dr. W. Hampe has also made an experimental test of this subject with the following conclusions: J — "The reduction of alumina by carbon, although often patented, is on thermo-chemical grounds highly improbable ; but since aluminium in alloying with copper, especially in the proportions 9.7 parts of the former to 90.3 parts of the latter (AlCu,), evolves much heat, it might be possible that the re- action AI.O3 + 3C + 8Cu - 2AlCu^ + 3CO is exothermic. I therefore mixed alumina with the necessary * Schweizer Polytechnisches Zeitschrift, i860, p. 16. t Wagner's Jahresbericht, 1865, p, 23. I Chemiker Zeitung (Cothen), xii. p. 391 C1888). REDUCTION OF ALUMINIUM COMPOUNDS. 417 quantity of lamp-black and copper, in other cases evaporated together to dryness solutions of aluminium and copper nitrates, afterwards igniting them to oxides and adding the necessary amount of carbon. These mixtures were put into gas-carbon crucibles contained within plumbago pots with well-luted covers, and heated in a Deville blast-furnace to a temperature sufficient to frit together the quartz sand with which the space between the two crucibles had been filled. In no case was there a trace of aluminium produced, nor did the addition of any flux for the alumina affect the result in any way." The possibility of reducing aluminium sulphide by copper has been generally decided affirmatively. M. Comenge claimed that it was possible (see p. 411), Reichel * also stated unreservedly that copper fillings performed the reduction at a high temperature. In an experiment by the author, copper foil was used instead of copper filings, the latter not being im- mediately at hand, and the result was negative. As a similar test with iron filings gave a good result, it seems quite probable that copper would have performed the reduction under proper conditions. Andrew Mann,f of Twickenham, patents a process which may be stated briefly as follows : Aluminium sulphate is mixed with sodium chloride and heated until a reaction be- gins to take place. The mass is mixed intimately with lime, and to this mixture aluminium sulphate and ground coke added. This is calcined, the powder mixed with a metal; as copper, and melted down. In this case the slags are calcium sulphide and copper chloride, while aluminium bronze is ob- tained. L. Q. Brin, of Paris,} claims to produce aluminium bronze by the following process : Sheet copper is cleaned by pickling and then covered with a mixture of 2 parts borax, 2 parts common salt, and i part sodium carbonate, made into paste ♦ Journal fiir Pr. Chemie, xi. p. 55. t English Patent, 9313, June 30, 1887; German Patent, 457SS' J^ec. 20, 18S7. J English Patents, 3547-8-9, March 7, 1888; U. S. Patent, 410574, Sept. 10, 1889. 27 41 8 ALUMINIUM. with water. The metal is then put into a reverberatory fur- nace, heated to bright redness, and vapors of aluminium chlo- ride led over it, carried in by a current of inert gas. (It is stated that the vapors of aluminium chloride are produced by heating in a retort a mixture of clay, salt and fluorspar.) The aluminium compound is said to be decomposed, and the nas- cent aluminium to combine with the copper, forming ij4 to 2 per cent, bronze at one operation, and by using this over it may be enriched to any extent desired. In a modification of this method, the coating put on the metal contains clay or other earth rich in alumina. It is also stated that the metal thus coated can be put into a cupola with alternate layers of fuel and run down to an alloy. Reduction by or in Presence of Iron. M. Comenge claims that aluminium sulphide is reduced by iron (see p. 41 1 ) ; the statement is repeated by a writer in the " Chemical News," i860; F. Lauterborn* states that the reduc- tion takes place at a red heat; Reichelj also records his success in this reaction ; finally, the author has obtained encouraging results.! I used a product containing 32.3 per cent, of alu- minium sulphide. On mixing this intimately with fine iron filings, and subjecting to a high heat for one and a half hours, the product was a loose powder in which were small buttons of metal. They were bright, yellower than iron, and contained by- analysis 9.66 per cent, of aluminium. H. Niewerth§ has patented the following process : " Ferro- silicon is mixed with aluminium fluoride in proper proportions and the mixture submitted to a suitable red or melting heat by which the charge is decomposed into volatile silicon fluoride (SiFi), iron and aluminium, the two latter forming an alloy. In order to obtain the valuable alloy of aluminium and copper * Dingier, 242, 70. t Jrnl. fur Pr. Chemie, xi. 55. I Graduating Thesis, Lehigh University, June, 1886. § Sci. Am. Suppl., Nov. 17, 1883. REDUCTION OF ALUMINIUM COMPOUNDS. 419 from this iron aluminium alloy, the latter is melted with metallic copper, which will then by reason of greater affinity unite with the aluminium, while the iron will retain but an insignificant amount of it. On cooling the bath, the bronze and iron sepa- rate in such a manner that they can readily be kept apart. In place of pure aluminium fluoride, cryolite may advantageously be employed, or aluminium chloride may also be used, in which case silicon chloride volatilizes instead of the fluoride. Or again, pure silicon may be used with aluminium fluoride, cryo- lite, or aluminium chloride, in which case pure aluminium is obtained." Mr. W. P. Thompson* has taken out a patent in England| for the manufacture of aluminium and similar metals, which is carried out as follows : " The inventor employs as a reducing agent iron, either alone or conjointly with carbon or hydrogen. The operation is effected in an apparatus similar to a Bessemer converter, divided into two compartments. In one of these compartments is placed melted iron, or an alloy of iron, which is made to run into the second by turning the converter. This last compartment has two tuyeres, one of which serves to in- troduce hydrogen, while by the other is introduced either alu- minium chloride, fluoride, double chloride or double fluoride, with sodium, in liquid or gaseous state. In the presence of the hydrogen, the iron takes up chlorine or fluorine, chloride or fluoride of iron is disengaged, and aluminium mixed with car- bon remains as a residue. Then this mixture of iron, alumin- ium and carbon is returned to the other compartment, where the carbon is burnt out by means of a current of air. The mass being then returned to the chamber of reduction, the operation described is repeated. When almost all the iron has been consumed, the reduction is terminated by hydrogen alone. There is thus obtained an alloy of iron and aluminium. (The preparation of sodium does not require the intervention of hydrogen. A mixture of iron with an excess of carbon and * Bull, de la Soc. Chem. de Paris, 1880, xxiv. 719. t March 27, 1879, No. 2101. 420 ALUMINIUM. caustic soda (NaOH) is heated in the converter, when the so- dium distils off. When all the carbon has been burnt, the iron remaining as a residue may be converted into Bessemer steel. As iron forms an alloy with potassium, the method would scarcely serve for the production of that metal.) To obtain the pure aluminium, sodium is first prepared by the process in- dicated, the chloride or fluoride of aluminium is introduced into the apparatus in the other chamber, when the metal is reduced by the vapor of sodium. The chambers ought to be slightly inclined, and an agitator favors the reaction. The inventor intends to apply his process to the manufacture of magnesium, strontium, calcium and barium." That aluminium could be produced at all by the above re- actions is very improbable ; it is not likely that the reactions were even seriously tested. Calvert and Johnson * made experiments on the reduction of aluminium by iron, and the production thereby of iron- aluminium alloys. We give the report in their own words: — "We shall not describe all the fruitless efforts we made, but confine ourselves only to those which gave satisfactory results. The first alloy we obtained was by heating to a white heat for two hours the following mixture : — 8 equivalents of aluminium chloride 1076 parts. 40 " iron filings 1 120 " 8 " lime 224 " "The lime was added to the mixture with the view of remov-. ing the chlorine from the aluminium chloride, so as to liberate the metal and form fusible calcium chloride, CaClj. Subtract- ing the lime from the above proportion, we ought to have obtained an alloy having the composition of i equivalent of aluminium to 5 equivalents of iron, or with 9.09 per cent, of aluminium. The alloy we obtained contained 12 per cent., which leads to the formula AlFe^. This alloy, it will be noticed, has an analogous composition to the one we made of iron and *Phil. Mag., 1855, A. 240. REDUCTION OF ALUMINIUM COMPOUNDS. 42 1 potassium, and like it was extremely hard, and rusted when exposed to a damp atmosphere. Still it could be forged and welded. We obtained a similar alloy by adding to the above mixture some very finely pulverized charcoal and subjecting it to a high heat in a forge furnace for two hours. This alloy gave on analysis 12.09 per cent.* But, in the mass of calcium chloride and carbon remaining in the crucible there was a large amount of globules varying in size from a pin-head to a pea, as white as silver and extremely hard, which did not rust in the air or in hyponitric fumes. Its analysis gave 24.55 P^"" cent, aluminium ; the formula AljFej would give 25 percent. Therefore this alloy has an analogous composition to alumina, iron ifeplacing oxygen. We treated these globules with weak sulphuric acid, which removed the iron and left the aluminium, the globules retaining their form, and the metal thus obtained had all the properties of the pure aluminium. "We have made trials with the following mixtures, but al- though they have yielded results, still they are not sufiSciently satisfactory to describe in this paper, which is the first of a series we intend publishing on alloys. This mixture was: — Kaolin 1 750 parts. Sodium chloride 1 200 " Iron 87s " "From this we obtained a metallic mass and a few globules which we have not yet analyzed." (See also Benzon's process, p. 414.) M. Chenot,t on the occasion of Deville's first paper on alu- minium being read to the French Academy, Feb. 6, 1854, an- nounced that in 1847, by reducing earthy oxides by means of metallic sponges, he had obtained a series of alloys containing up to 40 per cent, of the earth metals. He cited from a * In the original paper it is given as 1 2.09 per cent. iron. The inference is un- avoidable that this was a misprint, but it is not corrected in the Errata at the end of the volume. tComptes Rendus, xxxviii^4i5. 422 ALUMINIUM. memoir presented by him to the " Societe d'Encouragement," in 1849, in which he had said, "on taking precipitates of the earths, they are all reduced by the metallic sponge {e. g., that formed by reducing iron oxide in a current of carbonic oxide gas). In this manner I have made barides, silicides, aluminides, etc., all of which are beautiful silver-white, very hard and un- oxidizable in air or in contact with acid vapors. They are fusible, can be cast, and work perfectly under the hammer." Faraday and Stodart* made an exhaustive investigation on the preparation of iron-aluminium alloys, being started on this line by finding that Bombay " wootz" steel contained O.O128 to 0.0695 psi" cent, of aluminium, while no metals of the earths were to be found in the best English steels. This led to the conclusion that the peculiar properties of the former, especially the " damasceening," were due to the small amount of alumin- ium. These scientists commenced by taking pure steel or sometimes good soft iron and intensely heating it for a long time imbedded in charcoal powder. Carbides were thus formed, having a very dark gray color, and highly crystalline. Average analysis of this product gave 5.64 per cent, carbon. This was broken and powdered in a mortar, mixed intimately with pure alumina, and heated in a closed crucible for a long time at a high temperature. An alloy was obtained of a white color, close granular texture and very brittle, containing 3.41 per cent, of aluminium, with some carbon. When 40 parts of this alloy were melted with 700 parts of good steel (introducing O.184 per cent, of aluminium) a malle- able button was obtained which gave a beautiful damask on treatment with acids ; while 6"] parts of the alloy with 500 of steel (introducing 0.4 per cent of aluminium) gave a product which forged well, gave the damask and " had all the appreci- able characters of the best Bombay wootz." This appears to be very strong synthetic evidence that alumina is reduced to a small extent even in the rude hearths in which the Indian steel is manufactured. Karsten, however, could not find weighable * Quarterly Journal, ix. 320. REDUCTION OF ALUMINIUM COMPOUNDS. 423 quantities of aluminium in specimens of wootz, nor could Henry, a very expert analyst. The latter suggested that Fara- day was misled by the alumina contained in intermingled slag, yet the latter obtained alumina without silica in his analyses. In the light of more recent developments we would accept Faraday's results as being very near the truth in the matter. Ledebuhr* quotes an analysis made by Griiner in which 0.50 per cent, of aluminium was found in cast-iron containing be- sides 2.30 per cent, of carbon and 2.26 per cent, of silicon. This would tend to show that under certain conditions iron takes up aluminium in the blast-furnace. Karsten, however, in his many analyses of malleable iron, steel and cast-iron, only found aluminium in unweighable quantities. Griiner and Lauf stated that aluminium is reduced in small quantities in the blast furnace if the temperature is high and the slag basic; a large addition of lime thus increases the reduction of alumina and hinders that of silica. Most pig irons contain very small amounts of aluminium, but some English varieties contain 0.5 to i.o per cent, and several Swedish pig irons 0.75 per cent. Schafhautl:j: found as much as i.oi per cent of aluminium in a gray iron, and was led to consider silicide of iron and aluminide of iron as characteristic components of gray iron. Lohage§ states that adding alumina in the manufacture of cast-steel has a great influence on the grain and lustre of the steel, the effect being doubtless due to a minute quantity of aluminium taken up. Silicates of magnesium and aluminium are formed at the same time, and separating out, float on the surface of the molten steel. Corbinjl reports 2.38 per cent, of aluminium in chrome steel ; but Blair,ir of Philadelphia, found no more aluminium in chrome than in other steels. This chemist has examined many * Handbuch der Eisenhiittenkunde, p. 265. t Berg u. Hiittenmannische Zeitung, 1862, p. 254. X Erdman's Journal fr. Pr. Chemie, Ixvii. 257. § Berg u. Huttenmannische Zeitung, 1861, p. 160. II Silliman's Journal, 1869, p. 348. t H. M. Howe, E. and M. J., Oct. 29, 1887. 424 ALUMINIUM. irons and steels particularly for aluminium, and reports that nearly always it exists as such in steel, but never more than a few thousandths of i per cent., say 0.032 per cent as a maxi- mum. He has further been unable to connect its presence with any peculiarity in the properties of the metal or its mode of manufacture. G. H. Bilhngs,* of the Norway Iron Works, Boston, made the following experiment on reducing alumina in contact with iron : — A soft iron was used containing a trace of sulphur and phosphorus, no manganese and only 0.08 per cent, of carbon. The mixture was made of 12 parts emery. 18 " alumina. I " pulverized charcoal. 36 " fine iron turnings. These were mixed thoroughly, and heated to whiteness for 48 hours. The melting resulting showed a solid, homogeneous fracture with a fine crystalline structure resembling steel with i per cent, of carbon, and contained on analysis 0.20 per cent, of carbon. 0.50 " aluminium. It was also found that if this quantity of aluminium was added to a pot of molten iron, the product obtained exhibited the same characteristics as the above. Another attempt to produce iron-aluminium alloys directly is stated in E. Cleaver's patent specifications as follows : f Four parts of aluminium sulphate in solution are mixed with one part of lamp-black, the mixture dried and heated to the highest temperature attainable by using coal-gas and oxygen in a lime-lined furnace similar to those used for melting plati- num. Excess of reducing gas is maintained. The charge is cooled in the furnace, removed, mixed with twenty-times its weight of finely-divided cast-iron, and fused in a steel melting * Transactions American Inst. Mining Engineers, 1877, p. 452. t English Patent, 1276, Jan. 26, 1887. REDUCTION OF ALUMINIUM COMPOUNDS. 425 furnace. If copper is used, a bronze results. The alloying metal may be added in the gas furnace, but this is not recom- mended as economical. This inventor also claims that alu- minium ferrocyanide, either alone or with carbon, can be decomposed in the above-described gas furnace, yielding a rich iron-aluminium alloy. As a higher heat than before is needed, it is recommended that the oxygen be previously heated. The principal difficulty in this latter process would apparently be to procure the aluminium ferrocyanide to operate on. Mr. Ostberg,* connected with the Mitis process for making wrought-iron castings, stated that the ferro-aluminium used in that process in Sweden was made by adding clays to iron in process of smelting, that it contained 7 to 8 per cent, of alu- minium, and could be made very cheaply. Inquiries made for further particulars about this process have received no satisfac- tory reply, and there is no outside confirmation of the above statement to be found. Brin Bros, claim that they can alloy aluminium in small quantities with iron (see p. 417). Besides the processes de- scribed as most suitable for producing bronze, they also state that if soft strap-iron is coated with the flux composed of clay and salt and heated to over 1000° C. in a mufHe or a blowpipe flame, the iron absorbs aluminium and becomes tough and springy, having many of the properties of steel. They also claim that by simply charging broken lumps of cast-iron into a cupola with alternate layers of common clay and a flux, the metal run down contains as much as 1.75 per cent, of alumin- ium, yielding a very fluid, strong iron, which runs into the thinnest castings. The London papers state that the alloys thus produced assuredly contain aluminium, and that the con- tained aluminium does not cost over 25 cents per lb. A newspaper report speaks of exactly similar processes be- ing operated by an aluminium company in Kentucky. (See also p. 403.) It is said that they charge a cupola with scrap- iron, pig-iron, coke, clay, and a flux,- and that on melting the * Engineering and Mining Journal, May 15, 1886. 426 ALUMINIUM. charge down and pouring, the castings produced are similar to the best steel, the fracture of the metal being white, slightly- fibrous, and free from blow-holes. It is stated, further, that the castings, on analysis, contained 1.7 per cent, of aluminium. Scrap-iron is also treated in the same way as reported by Brin Bros., being simply coated with a pasty mixture of clay and a flux and heated almost white-hot, when the iron absorbs alu- minium. The Aluminium Process Company of Washington, D. C, own several patents granted to W. A. Baldwin, of Chicago, 111. In one of these,* a bath is formed by fusing together 4 parts of ground clay, 12 parts of common salt and i part of charcoal powder. The metal to be alloyed, e. g., an iron bar, is thrust into the bath, which is not hot enough to melt it, and allowed to remain some time, with occasional stirring, until the alloying is complete. In the case of metals with low fusing points the metal may be melted with the mixture. It is claimed that the metal takes up a small percentage of aluminium. With a more highly aluminous material than clay, the proportions of salt and carbon are to be increased proportionately. In a modification of this process adopted for foundry practice,! a mixture of clay, salt and carbon, similar to the above, is put into a large ladle and the molten iron tapped directly from the cupola on to it. A brisk stirring up of the iron takes place, much scum rises to the surface, and the resulting iron is more fluid, can be carried further before setting, and makes sounder and stronger castings than similar iron not treated. The resulting iron does not contain enough aluminium to be detected by quantitative analysis. Old-fashioned fluxes used long ago in foundries were similar in composition to this mixture used by Baldwin, and were found efficacious in freeing dirty iron from slag and other impurities. It is hard to see how this latter process is anything but the use of a common flux, with a different explanation as to how it acts — the explanation being probably the most ques- * English Patent, 2584, Feb. 21, 1888. tU. S. Patent, 380161, March 27, 1888. REDUCTION OF ALUMINIUM COMPOUNDS. 427 tionable part of the whole. The first-mentioned process, how- ever, has the merit of novelty, and pieces of poor iron treated by it are made springy and much like steel, but whether this is due to absorption of aluminium is doubtful. The Williams Aluminium Company, of New York City (works at Newark, N. J.), manufacture an alloy which they call aluminium-ferro-silicon and sell for foundry use. When first introduced, this alloy was represented to contain 10 per cent, of aluminium, but several analyses disproved this, and afterwards the alloy was sold simply on the guarantee of what it would accomplish. The metal since sold by this company does contain a small amount of aluminium, and its action on poor foundry iron is similar to that of other brands of ferro-alumin- ium ; therefore, as long as no certain percentage of aluminium is now claimed, the company is certainly doing a legitimate business. (For method of using, etc., see Chap. XVI.) The alloy is made by melting down a mixture of iron filings, clay, salt,' charcoal, and another flux whose composition is not divulged. This is put into cast-iron pots and the whole charge, crucibles and all, run down in a furnace of peculiar design constructed by Mr. Williams. The capacity of the plant is about 1000 lbs. of alloy a day, which is broken by small stamps into pieces of about an inch diameter and sold at 10 cents per lb. Mr. Williams also experimented on manufactur- ing aluminium bronze by the same methods, and a sample piece forwarded the author contained a small percentage of aluminium. G. Bamberg, London,* claims to produce alloys of alumin- ium by taking iron or copper rich in silicon, putting them molten into a Bessemer converter, raising the temperature by blowing air through in the usual way, and then passing in vapors of aluminium chloride or aluminium-sodium double chloride. Mr. Chas. T. Holbrook, connected with the well-known * English Patent, 7666, May 8, 1889. 428 ALUMINIUM. iron-masters Marshall Brothers, of Philadelphia, has reported the existence of aluminium in the pig-iron made at the Marshall furnace, Newport, Perry county. Pa. Mr. Holbrook has made many tests on the efTect of adding aluminium to cast-iron, and on one occasion, happening to see pig-iron being tapped from this furnace, he remarked that it flowed as if it contained alu- minium, judging by its bright, silvery appearance. An analy- sis of the pig-iron was at once made, and confirmed this opin- ion by showing 0.267 per cent. Since then, numerous analyses have shown an average of 0.20 to 0.50 per cent., while for a short period, when the furnace was working much hotter than usual, over one per cent, has been obtained. The question as to what circumstances favor this considerable reduction of alu- mina is probably to be referred to the nature of the combina- tion in which it occurs in the ores. It is found, for instance, that when using ores from the Juniata Valley, the iron was richer in aluminium than when a larger amount of ore from a distance was used. The composition of the local ores is there- fore of interest, and the following are copied from a letter of Mr. Holbrook's : * Grafton Fossil Ore. Juniata Hematite (Dried at ioo° C.) (Dried at ioo° C.) Silica 10.680 17.580 Alumina 12.469 5-692 Ferric oxide 73.481 6l-l33 Manganese oxide 0.431 0.700 Fhosphoric acid i .1 70 0.895 Sulphuric acid none none Lime trace trace Magnesia none none Combined water and organic matter 2.700 10.700 100.931 96.700 The pig-iron made contains 3 to 5 per cent of silicon, and is a first-class foundry iron. Most aluminium was reduced when using the Grafton ore, and it appears in this ore the alumina is present in a much * Iron Age, June II, 1891. REDUCTION OF ALUMINIUM COMPOUNDS. 429 larger proportion than it could be if combined with silica alone. In other words, if the siKca were all present as ordinary clay, it could not be combined with over 9 per cent, of alumina. It is to me a very probable conclusion that the ore either con- tains free alumina, or possibly, some Hercynite, the aluminate of iron, FeO.AljOs. This compound would evidently reduce to an iron-aluminium alloy. Whatever be the real reason for it, the fact remains that this is a real instance of aluminium being re- duced from alumina in the presence of iron, at the temperature of a blast furnace of moderate size. This temperature prob- ably never exceeds 2000° C. Pearson and Pratt* have patented the following means for facilitating the reduction of aluminium in the iron blast-fur- nace. Calcined iron ore is mixed with a considerable quantity of clay and the necessary amount of coke, and charged into a blast-furnace with fluorspar for a flux instead of limestone. Cast-iron containing aluminium results. Reduction by or in Presence of Zinc. M. Beketoff,! was not able to reduce vapor of aluminium chloride by vapor of zinc, although silicon chloride under the same conditions was readily reduced. M. Dullo| observes that the double chloride of aluminium and sodium, which he makes directly from clay, may be re- duced by zinc. He says, " The reduction by zinc presents no difificulties, but it is less easy than with sodium. An excess of zinc should be employed, which may be got rid of after- wards by distillation. The, metal thus prepared possesses all the characteristics and all the properties of that obtained from bauxite with sodium." M. N. Basset,§ a chemist in Paris, patented a somewhat sim- * English Patent, 18048, Nov. 12, 1889. t Bulletin de la Societe Chemique, 1857, p. 22. J Bull, de la Soc. Chem., i860, v, 472. §Le Genie Industriel, 1862, p. 152. 430 ALUMINIUM. ilar process for obtaining aluminium. If the statements are correct they are of great value. The paper is as follows : " All the metalloids and the metals which form by double de- composition proto-chlorides or sesqui-chlorides more fusible or more soluble than aluminium chloride may reduce it or even aluminium-sodium chloride. Thus, arsenic, bismuth, copper, zinc, antimony, mercury, or even tin or amalgam of zinc, tin, or antimony may be employed to reduce the single or double chloride. The author employs zinc in preference to the others in consequence of its low price, the facility of its employment, its volatility, and the property which it has of metallizing easily the aluminium as it is set free. When metallic zinc is put in the presence of aluminium-sodium chloride, at 250° C. to 300° C, zinc chloride, ZnCl^, is formed and aluminium is set free. This dissolves in the zinc present in excess, the zinc chloride combines with the sodium chloride, and the mass becomes lit- tle by little pasty, then solid, while the alloy remains fluid. If the heat is now raised, the mass melts anew, the zinc reduces a new portion of the double chloride and the excess of zinc en- riches itself in aluminium proportionately. These facts consti- tute the basis of the following general process : One equiva- lent of aluminium chloride is melted, two of sodium chloride added, and when the vapors of hydrochloric acid are dissipated, four equivalents of zinc, in powder or grain, are introduced. The zinc melts rapidly, and by agitation the mass of chloride thickens and solidifies. The mass is now composed of the chlorides of aluminium, zinc and sodium, and remains in a pasty condition on top of the fluid zinc containing aluminium. This pasty mass is removed, piled up in a crucible or in a fur- nace, and bars of the fluid alloy of zinc and aluminium ob- tained from a previous operation are placed on top of it. This is gradually heated to bright redness, and kept there for an hour. The melted mass is then stirred with a rake and poured out. It is an alloy of the two metals in pretty nearly equal proportions. This alloy, melted with some chloride from the first operation, furnishes aluminium containing only a small REDUCTION OF ALUMINIUM COMPOUNDS. 43 1 per cent, of zinc, which disappears by a new fusion under alu- minium chloride mixed with a little fluoride, providing the temperature is raised to a white heat and maintained till the cessation of the vapors of zinc, air being excluded. " The metal is pure if the zinc employed contained no foreign materials or metals. In case the zinc contains iron, or even if the aluminium chloride contains some, the metallic product of the second operation may be treated with dilute sulphuric acid to remove it. The insoluble residue is washed and melted layer by layer with fluorspar or cryolite and a small quantity of aluminium-sodium chloride, intended solely to help the fusion." Mr. Wedding,* makes the following remarks on this process : " It is some time since Mr. Basset established the possibility of replacing sodium by zinc in the manufacture of aluminium. Operating on aluminium-sodium chloride with granulated zinc, the reduction takes place towards 300°. The reduced alumin- ium dissolves in the excess of zinc, while the zinc chloride formed combines with the sodium chloride, forming a pasty mass if the heat is not raised. Under the action of heat the alloy enriches itself in aluminium, because the zinc volatilizes. The zinc retained by this alloy is completely eliminated by fus- ion with double chloride and a little fluorspar. The tempera- ture ought' to be pushed at least to a white heat, and main- tained till no vapor of zinc escapes, air being excluded during the operation. These results I have confirmed, having sub- mitted the experiments of Mr. Basset to an attentive examina- tion, and I recommend its use. However, the process de- mands very much precaution, because of the high temperature which it necessitates. Another chemist, Mr. Specht, even in i860 decomposed aluminium chloride by zinc, and has the same report to make — that he thinks the process will be some- time advantageously practised on a large scale." The author made the following experiment to determine if cryolite would be reduced by zinc : One pound of finely pow- * Journal de Pharm. [4] iii. p. 155 (1866.) 432 ALUMINIUM. dered cryolite was melted in a graphite crucible, and 6 ounces of granulated zinc dropped into it. No perceptible reaction took place except the volatilization of zinc when the crucible was uncovered, and the metal obtained after 15 minutes' treat- ment contained on analysis 0.6 per cent, of aluminium. Mr. Fred J. Seymour * patented the reduction of aluminium by zinc, making the following claim : An improvement in ex- tracting aluminium from aluminous earths and ores by mixing them with an ore of zinc, carboniferous material and a flux, and subjecting the mixture to heat in a closed resort, whereby the zinc is liberated, is caused to assist in bringing or casting down the aluminium in a metallic state, and the alloy of alu- minium and zinc is obtained. A furnace was put up in the early part of 1884, somewhere in the vicinity of Cleveland, in a description of which by a newspaper correspondent we are told that steel retorts were charged with a mixture of zinc ore 100 parts, kaolin 50, carbon (either anthracite coal or its equivalent of some hydrocarbon) 125, pearlash 15, common salt 10: the heat necessary being about 1400° C. In a second patent, f Mr. Seymour claimed that by heating the same mixture in a retort and introducing air he volatilized oxides of aluminium and zinc, which were caught in a condenser, mixed with carbon, and reduced in a crucible. Immediately after the issue of this patent, the Amer- ican Aluminium Company was organized in Detroit with a cap*- ital stock of $2,500,000 to operate the patents of a Dr. Smith, under whose name processes similar to the above had been patented in Great Britain and France. A works was then started at Findlay, Ohio, using natural gas for fuel. A gentle- man who saw the plant described it as a reverberatory furnace into which a charge of 800 lbs. of zinc ore, 900 of native alum, and 300 of charcoal was put. On heating very strongly by gas with plenty of air admitted, zinc oxide was volatilized (Mr. Sey- *U. S. Pat., No. 291631, Jan. 8, 1884. tU: S. Patent, 337,996, March 16, 1886. REDUCTION OF ALUMINIUM COMPOUNDS. 433 mour claimed that it carried alumina with it), and was con- densed by passing the gases through large copper condensers. This fume was then collected, mixed with carbon and a metal, and run down in a crucible to an alloy. It was clairiied that the plant had a capacity of 600 lbs. of pure aluminium a day, and had presumably been in operation over a year, yet there was not over 20 lbs. of alloys or j^ lb. of pure aluminium to show for it. On closer inspection so plain indications of fraud were visible in the last part of the operation that, although ver- itable aluminium alloys were taken out of the crucible, the gen- tlemen referred to refused to believe that the aluminium was produced in the process. As the sequel to this it can be stated that in the middle of 1889 the executive committee for the stockholders, being fully satisfied of the worthlessness of the process, called for a meeting to wind up the company. One month later Mr. Seymour died. The story went the rounds of the daily press that the one metallurgist who com- manded the secret of obtaining cheap aluminium had died, tak- ing the talisman with him, and a vivid picture was drawn of the manner in which the secret had been preserved by means of twelve-foot palisades, double-bolted doors, and by working at the midnight hour. Alas, the secret was out one month before he died ! A method of reducing cyanide of aluminium by means of zinc is the subject of a patent granted F. Lauterborn.* Four- teen parts of aluminium sulphate dissolved in twice its weight of water is precipitated by thirteen parts of ferro-cyanide of potassium dissolved in four times its weight of water ; the pre- cipitate of ferro-cyanide of aluminium is collected and dried. This substance is then mixed with slightly less than one-half its weight of dry, anhydrous sodium carbonate, put in a crucible and ignited with as little admission of air as possible. The ferro-cryanide is decomposed, iron carbide separates out, and besides sodium cyanate, the double cyanide of aluminium and * German Patent, 39915 (1887), 28 434 ALUMINIUM. sodium (Al2Cy6+3NaCy) is obtained as a melted mass which is poured away from the heavier iron carbide at the bottom of the crucible. If two parts of this salt are then ignited with one part of zinc in a covered crucible, aluminium separates as a regulus, while double cyanide of sodium and zinc remains as slag. The slag is dissolved in water and treated with metallic iron, whereby metallic zinc is precipitated out and a solution of ferro-cyanide of soda remains and can be used over in the pro- cess. I do not know whether Lauterborn has ever succeeded in carrying out this process ; it would appear at the very begin- ning that the precipitation of aluminium ferro-cyanide, although appearing a priori possible, has always been found impractic- able, alumina being precipitated. J. Clark, of Birmingham, England, has taken out several pat- ents in England and one in Germany. In the first,* hydrated aluminium chloride is to be mixed with lime, iron, zinc, am- monia, or any other substance which combines readily with chlorine, and finely divided coke. After drying the mixture it is introduced into the iron blast furnace or blown into the Bes- semer converter, an iron-aluminium alloy being thus produced. In a second patent,! hydrated aluminium chloride is to be mixed with 2 ^2 parts of granulated zinc and i part of iron turnings or borings, or the alloy of the zinc and iron known as "zinc dross" might be used. The mass is let stand 24 hours and dried. The orange-colored powder resulting is mixed with borax (!) or any suitable flux, and put in a crucible with 20 parts of fine granulated copper and melted down. After about an hour the zinc and iron present have probably volatil- ized as chlorides, while aluminium bronze remains. When the copper is to be alloyed in large quantities, it may be melted on the hearth of a reverberatory furnace and the prepared powder stirred into it. * English Patent, 15946, Dec. 6, 1886. t English Patent, 10594, Aug. 18, 1886; German Patent, 40205, (1887). REDUCTION OF ALUMINIUM COMPOUNDS. 435 Dr. J. D. Lisle, of Springfield, Ohio, made the following ex- periments in reducing aluminium sulphide by zinc. The sul- phide was made in a crucible, mounted on trunnions to keep the contents agitated, in which alumina was placed and treated with superheated carbon bi-sulphide vapor. While the con- tents were still hot, solid or melted zinc was put into it, the heating continued, the crucible constantly agitated and a cur- rent of hydrocarbon gas led into the crucible through a hole in the cover. The outcoming gas contained some sulphuretted hydrogen, seeming to show that reduction was accomplished partially, at least, by the hydrocarbon. After heating about half an hour the openings were sealed up and the apparatus cooled. The product was analyzed, and the result of nine ex- periments gave results varying from 1.06 to 10 per cent, of aluminium present in the zinc. The richest alloy was distilled carefully, leaving aluminium which analyzed 98 per cent, pure and contained only a trace of zinc. It is difficult, however, to see any possibility of a commerical process being worked up on these lines which could compete with the present methods of extraction. G. Bamberg, of London,* claims that if metallic zinc is vapor- ized it will reduce the vapor of aluminium chloride. He puts metallic zinc in a retort heated sufficiently to distil off zinc vapor, and in another retort is placed aluminium chloride or aluminium-sodium chloride. The vapors mix in a third highly heated chamber, in which they react, and there is condensed an alloy rich in aluminium. This is heated to whiteness in an- other retort to distil off the zinc. Reduction by Lead. According to the invention of Mr. A. E. Wilde, f of Notting Hill, lead or sulphide of lead, or a mixture of the two, is melted, and in a molten state poured upon dried or burnt alum. The * English Patent, 7667, May 8, 1889. t Sci. Am. Suppl., Aug. 11, 1887. 436 ALUMINIUM. crucible in which the mass is contained is then placed in a fur- nace and heated, with suitable fluxes. The metal, when poured out of the crucible, will be found to contain aluminium. The aluminium and lead can be subsequently separated from each other by any known means, or the alloy or mixture of the two metals can be employed for the various useful purposes for which lead alone is more or less unsuited. Reduction by Manganese. Walter Weldon * claimed to melt together cryolite with cal- cium chloride or some other non-metallic chloride or sulphide, and then to reduce the aluminium chloride or sulphide pro- duced by manganese, also adding metallic sodium to promote the reaction. Of course, the manganese would be used as ferro- manganese or spiegeleisen, and an iron alloy produced. Dr. Green, of Philadelphia, mixed powdered spiegeleisen with cryo- lite, placed the mixture in a graphite crucible, and heated it close to the ports of an open-hearth steel furnace until it soft- ened, yet the iron contained afterwards only 0.3 per cent, of aluminium. When we examine closely the heat of combination of man- ganese and aluminium compounds (Chapter VIII.) we see that in the combinations with chlorine and sulphur manganese is the stronger element, and we should therefore be led to expect that manganese would reduce aluminium chloride or sulphide. On the other hand, in the oxides, and particularly in the flu- orides, aluminium is the stronger element. We should there- fore expect aluminium to reduce manganese oxide and fluoride. This is, in fact, just what occurs. Drs. Green and Wahl, of Philadelphia, are, in fact, producing pure manganese on a com- mercial scale by dissolving manganese oxide in melted cryolite and adding metallic aluminium, f * English Patent, No. 97 (1883). t See Journal of the Franklin Institute, March, 1893, P- 218. reduction of aluminium compounds. 437 Reduction by Magnesium. Magnesium develops more heat in forming compounds than aluminium does (see p. 229), which would indicate that it would reduce aluminium compounds easily. Only one or two statements on this point can be found. Margottet * states that magnesium will decompose molten cryolite, setting the alu- minium at liberty. R. Gratzel f patents the reduction of a double fluoride of aluminium and potassium or sodium by metallic magnesium, or by conducting magnesium vapor into the liquid compound. Roussin I states that magnesium does not precipitate alu- minium in a metallic state from its solutions. To test this point I placed a strip of magnesium in solution of aluminium sulphate, when magnesium sulphate went into solution and a precipitate of alumina was formed. It is apparent that the aluminium is first precipitated in the metallic state and promptly oxidized by the water as fast as set free, in a manner strictly analogous to the production of alumina at the negative pole when electrolyzing aqueous aluminium solutions. In a patent awarded Count R. de Montgelas, of Philadel- phia,§ it is stated that aluminium chloride is mixed with litharge, charcoal and common salt ; fused and crushed. It is then re- melted with magnesium filings and potassium chloride. After cooling it is again crushed, mixed with more potassium chloride and nitrate of potash, fused, poured into water, and the globules of aluminium separated out. Clemens Winkler || states that when alumina is heated with powdered magnesium, in a current of hydrogen gas, it gives a nearly black powder containing over 40 per cent, of a sub-oxide of aluminium to which he assigns the formula AlO, together * Fremy's Ency. Chim. t English Patent, 14325, Nov. 25, 1885. { Jrnl. de Pharm. et de Chimie, iii., 413. § English Patent, 10606, August 18, 1886. II Berliner Berichte, xxiii. p. 772. 438 ALUMINIUM. with magnesium oxide and unaltered alumina. The last two are partly combined to magnesium aluminate. No metallic aluminium was obtained. Reduction by Antimony. F. Lauterborn * proposes to decompose aluminium sulphide by means of antimony and carbon. One hundred parts of dried aluminium sulphate is mixed with 50 parts of charcoal and 72 parts of metallic antimony ; some sodium carbonate and fluorspar is then added, and the mixture melted. It is claimed that antimony sulphide and aluminium are found in the pro- duct, the former being in the bottom of the crucible. In a modification of this process it is claimed t that if a mixture of dried aluminium sulphate, sodium carbonate, and antimony sulphide (stibnite) is put into a shaft filled with incandescent coke, antimony will be first set free by the reaction 2Sb2S3+6Na2C03+3C=6Na,S+9CO,+4Sb, and that these products act further on the aluminium sulphate, setting free aluminium by the reaction 2 Al, (SO*) 3+ 6Na,S+4Sb+ 1 2C=4Na2SbS3f4Al-|- 1 2CO,. The sodium sulph-antimonide can be smelted over with soda and antimony regained. These extraordinary formulas have little or no basis in chem- ical science. Dr. Fischer J says plainly that they are false. The author tried by direct experiment to reduce aluminium sulphide by antimony, fusing down a mixture of powdered antimony with aluminium sulphide, but the button of metal obtained did not contain a trace of aluminium. * German Patent, 32126(1885). t Dingier, 256, 226 and 233. I Wagner's Jahresbericht, 1885. reduction of aluminium compounds. 439 Reduction by Tin. J. S. Howard and F. M. Hill, assignors to the Aluminium Product Company, of New York, make the following statements in their patent specifications:* "Some aluminous material is boiled in muriatic acid, cooled, mixed with Spianish white or lime, the free acid evaporated off at a high temperature, and the heat finally increased to about 1000° F., thereby volatiliz- ing any iron present as chloride. The product thus obtained is put into a lime-lined crucible along with lime, charcoal, fluor- spar, cryolite and potassium bisulphate, the whole covered with chloride of tin, and finally by common salt. This is subjected to a smelting temperature, when on cooling it is claimed that an alloy of tin and aluminium is obtained. To separate the aluminium the alloy is melted with lead or bismuth, which alloy with the tin, letting the aluminium float on the surface along with oxides and other impurities. This is skimmed off and purified by exposure to heat on a bed of porous material." While we cannot altogether deny the possibility of metallic tin reducing aluminium chloride, yet it is not at all probable that this salt remains after the first ignition. It is also improb- able that tin would reduce cryolite in the latter operation, but there is no direct evidence to contradict the above statement. In an experiment made by the author, aluminium sulphide was heated with tinfoil for a short time at a red heat. The resulting metal contained 0.52 per cent, of aluminium, and from the proportions of tin and sulphide used, it was evident that a large part of the aluminium sulphide present had been reduced. Dr. J. D. Lisle, of Springfield, Ohio, has made experiments of the same nature on a more extensive scale. Aluminium sulphide was put in a crucible placed on trunnions, so as to permit agitating the contents, and metallic tin in flakes was put in with it. The crucible was closed, and when at a bright-red heat a stream of super-heated gasoline vapor led into the cru- * U. S. Patent, 378,136, Feb. 21, 1888. 440 ALUMINIUM. cible. Hydrogen sulphide was copiously formed, but an ex- plosion of gasoline vapor terminated the experiment. The crucible was not broken, and when cool was opened. It con- tained some shot-metal, which was collected and melted into a button. This was the color of steel, very hard and tough, and upon analysis gave 19.32 per cent, of aluminium. In another experiment equal parts of aluminium sulphide and tin, in flakes, were mixed together, placed in a graphite crucible, covered with powdered charcoal, and kept at a red-heat for one-half hour. The resulting button contained 9.8 per cent, of alu- minium. While such experiments are interesting as showing the pos- sibility of tin reducing an aluminium compound, yet pure aluminium cannot be made from the tin alloy, and metallic tin is so costly a reducing agent, being worth about 1 5 cents per pound, that this means of reduction can never be commercially applied, since aluminium itself is selling so cheaply. Reduction by Phosphorus. L. Grabau * patented the following process, in 1883, but has since virtually admitted that this method was not successful. The proposition was as follows : A rich alloy of aluminium and phosphorus is made by melting the two elements together or by fusing aluminium with phosphor salts and a reducing agent. The alloy is crushed, mixed with alumina or clay or aluminous fluorides, covered with coal dust and heated to in- candescence in a crucible. It was claimed that the phosphorus combined with the oxygen or fluorine of the aluminous com- pound, the metal produced uniting with the aluminium already present. To produce any given alloy, the phosphide of the required metal is substituted for the aluminium-phosphorus alloy. Mr. Grabau broadens out his specifications into more probable fields by adding that " manganesic or carburetted metals may be used instead of the phosphide alloys, as reducing * English Patent, 5798, Dec. 18, 1883. REDUCTION OF ALUMINIUM COMPOUNDS. 44I agents." It is almost needless to say that the generally small heat of combination of phosphorus compounds would show that the reactions proposed are in a high degree improbable. Reduction by Silicon. M. Wanner * makes the following general claims : The pro- duction of aluminium by treating a fused bath of aluminium fluoride or aluminous fluorides, while in a molten metallic bath and protected from oxidizing agents, with a reagent whose elements dissociate below the fusing point of the aluminium fluoride or the aluminous fluorides, and having one element of such affinity that it displaces the aluminium in the fluoride compound, but having no element capable of combining with the reduced aluminium. More specifically, sulphide of silicon or an equivalent reagent is mentioned, and the reaction takes place on the hearth of a short reverberatory furnace, the metallic bath mentioned being preferably metallic iron or cop- per, which are able to combine with the resulting aluminium. The reaction proposed is so far out of the usual run of specu- lations that no opinion can be hazarded as to its probability. Further, silicon sulphide is an almost unknown compound, and it would be very interesting to know how it is to be prepared ; it would probably be a more difficult feat to get the reagent alone than to produce aluminium by many well-known methods. * U. S. Patent, 410568, Sept. 3, 1889. CHAPTER XIII. working in aluminium. Melting Aluminium. DevillE: "To melt aluminium it is necessary to use an ordinary earthen crucible and no flux. Fluxes are always use- less and almost always harmful. The extraordinary chemical properties of the metal are the cause of this ; it attacks very actively borax or glass with which one might cover it to pre- vent its oxidation. Fortunately this oxidation does not take place even at a high temperature. When its surface has been skimmed of all impurities it does not tarnish. Aluminium is very slow to melt, not only because its specific heat is consid- erable, but its latent heat appears very large. It is best to make a small fire and then wait patiently till it melts. One can very well work with an uncovered crucible." " In the fusion of impure aluminium very different phenomena are observed, according to the nature of the foreign metal which contaminates it. Ferruginous material often leaves a skeleton less fusible and pretty rich in iron ; a liquation has taken plafte, increasing the purity of the melted material. When the alu- minium contains silicon this liquation is no longer possible, or at least it is very difficult, and I have sometimes seen some commercial aluminium so siliceous that the workmen were unable to remelt it. When it is desired to melt pieces together they can be united by agitating the crucible or compressing the mass with a well-cleaned cylindrical bar of iron. Clippings, filings, etc., are melted thus : Separate out first, as far as possi- ble, foreign metals, and to avoid their combining with the alu- minium heat the divided metal to as low a heat as possible, just sufficient to melt it. The oil and organic matters will burn, (442) WORKING IN ALUMINIUM. 443 leaving a cinder, which hinders the reunion of the metal if one does not pre§s firmly with the iron bar. The metal may then be cast very easily, and there is found at the bottom of the crucible a little cinder, which still contains a quantity of alu- minium in globules. These may be easily separated by rubbing in a mortar and then passing through a sieve, which retains the flattened globules." Biederman gives the following directions : " The whole quan- tity of metal which is to be melted must not be put into the crucible at once, but little by little, so increasing the mass from time to time as the contents become fully melted. The neces- sary knack for attaining a good clean melt consists in dipping the pieces which are to be melted together in benzine before putting in the crucible. Mourey even pours a small quantity of benzine into the crucible after the full melting of the metal, and he recommends the employment of benzine in the melting of all the noble metals. To utilize the scrap pieces produced in working aluminium into various useful articles, one must as far as possible separate out first the pieces which have been soldered, in order that the newly melted aluminium may not be contaminated by the solder. The solder adhering to these pieces can be removed by treating them with nitric acid, by which the aluminium is not attacked." Aluminium can be melted with perfect safety in common clay or sand crucibles if they are lined with carbon. This can be done by mixing lamp-black to a paste with molasses, plaster- ing the inside of the crucible evenly and drying slowly for several days at a moderate temperature. A means of getting a more perfect lining is to ram the crucible full of this paste, dry- ing slowly and then hollowing out a cavity of the required size leaving a uniform lining of sufficient thickness. In using these carbon-lined crucibles they should be kept well-covered, in order that the carbon may not burn away too quickly, taking particular care to place the cover on when the metal has been poured out and the crucible is cooling in the air. Small crucibles may be made of a single block of soapstone, and seem 444 ALUMINIUM. to last a long while, the aluminium apparently having no action on this mineral at a temperature a good deal higher than its melting point. With extra care, heating in a furnace where the heat is under exact control, aluminium may be melted in sand crucibles or in cast-iron ones. In using sand or Hessian crucibles no flux must be added, and if the metal is heated slowly to a tempera- ture only enough above its melting point to admit of pouring quickly, it will be found that the crucible is unattacked. If, however, the crucible is heated to a bright-red heat at any part, it will be found that at that place the aluminium has attacked the crucible, and on pouring out the metal a thin, tough skin will be left adhering to the spot attacked and generally taking with it bits of the wall when it is forcibly detached. This thin sheet is hard, tough, and rich in silicon, while the rest of the metal poured out has also absorbed a little silicon. An iron crucible acts in precisely the same way ; if the heat is kept close to the melting point of aluminium the latter does not " wet" the iron, but at a bright- red heat it attacks it and ad- heres, as in the case of the sarid crucible. I will repeat, that if the temperature is kept as low as it is possible to melt and cast the metal, and if no fluxes are used, neither the iron nor sand crucibles are attacked. In the large European works, where 500 or looo lbs. of alu- minium are melted at once on the bed of a reverberatory fur- nace, the hearth was formerly protected by pure bauxite, closely rammed in and strongly fired before using, but basic magnesia bricks have now been substituted, similar to those used in basic open-hearth furnaces but of purer materials, and they are reported as being all that can be desired in their capa- city for resisting corrosion. A very good lining for any kind of crucible is made by using calcined magnesite, for which I recommend the white, Grecian mineral, fully shrunk by calcining at the highest heat of a fire- brick or porcelain kiln and then ground fine and made into a stiff paste with sugar syrup or molasses. The crucible is care- WORKING IN ALUMINIUM. 445 fully lined and then heated slowly to redness. On cooling, any cracks are carefully filled with more paste, and the crucible is baked again ; when properly prepared, however, one baking is sufiScient, and the linings do not shrink from the walls of the crucible. This lining is a very serviceable one, not only for melting aluminium by itself, but also for using flux, for it re- sists cryolite, fluorspar or even a siliceous slag perfectly. Since experiment has shown that aluminium will take up about 0.25 per cent, of silicon from one re-melting at a red heat in a best- quality graphite crucible, it is very important that such deteri- oration be avoided if possible, and I earnestly advise all melt- ers and casters of aluminium to take the trouble to prepare these magnesite lined crucibles if they wish to get the best re- sults. This magnesite can be procured from the importers of chemicals in New York city, at a cost of about $0.02 per pound for the burnt and ground material. Casting Aluminium. Deville: "Aluminium can be cast very easily in metallic moulds, but better in sand for comphcated objects. The mould ought to be very dry, made of a porous sand, and should allow free exit to the air expelled by the metal, which is vis- cous when melted. The number of vents ought to be very large, and a long, perfectly round git should be provided. The aluminium, heated to redness, ought to be poured rather quickly, letting a little melted metal remain in the git till it is full, to provide for the contraction of the metal as it solidifies. In general, this precaution ought to be taken even when alu- minium is cast in iron ingot moulds or moulds of any other metal. The closed ingot moulds give the best metal for roll- ing or hammering. By following these precautions, castings of great beauty may be obtained, but it is not advisable to con- ceal the fact that to be able to succeed completely in all these various operations requires for aluminium, as for all other metals, a special familiarity with the material which practice alone is able to give." 446 ALUMINIUM. The peculiarity of molten aluminium which a metal caster would first notice is its viscousness, that is, it runs thick. When about to pour, a thick edge or lip of metal forms, which must in many cases be punctured in order to start the metal flowing. On account of this property it does not run sharply in the moulds except where a head of metal puts it under pres- sure. To obtain sharp castings there must be a " gate" to give pressure to the metal, and when we remember that the gravity of aluminium is only 2.6 and that, besides, it does not flow thinly, it will be seen that a much higher head of metal is necessary to ensure sharp castings than is needed for iron, brass, etc. A small slab of» aluminium two inches high run in a closed iron mould with very little gate was quite sharp at the lower end but had rounded corners at the top. For casting in closed moulds, the best results as to sharp castings free from cavities are obtained if a slight artificial pressure can be ap- plied to the still liquid metal in the mould immediately after pouring. This is accomplished by Dr. C. C. Carroll, of New York, an expert in making cast-aluminium dental plates, by closing in tightly the top of the crucible containing the molten aluminium, and then by air pressure from a rubber bulb forcing the metal through a syphon-shaped tube terminating under- neath the metal and connecting tightly with the pouring gate of the mould. The mould is previously heated, in order not to chill the metal too quickly, and when the metal has been forcfed out of the crucible by squeezing the bulb the pressure is con- tinued for a short time in order to force the metal into every crevice of the mould and allow the casting to set under pres- sure. The idea is undoubtedly correct, and the excellently sound and extremely sharp castings obtained by Dr. Carroll attest its success in practice. The Passaic Art Casting Company, of Passaic, N. J., make very fine castings in aluminium by the Smith pressure-casting process, by which the finest details of engraved, chased or re- poussee work are brought out with a finish equal to electro- WORKING IN ALUMINIUM. 447 types. Moulds, either of sand or of a liquid plaster-of-paris composition, are made in as flat a shape as possible so that they may be piled on top of each other, the gates from each mould leading to a central feeder. The entire charge of molten metal is kept in a suitable holder above the moulds. The moulds being air-tight, an air-pump is connected with the bottom of the molds while pressure is put on the molten metal above. A thin diaphragm used to keep the molten metal in the receiver is burst by the pressure, allowing the aluminium to flow quickly into the moulds, where it fills every minute cavity. Extremely light and sharp castings, having remarkable solidity and free from blow-holes, are thus obtained. Aluminium can be cast in dry sand moulds, which are best lined with powdered plumbago. The metal should be poured fast, and not be far above its melting point, or the castings will not be sound. The shrinkage to be allowed for is very nearly one-quarter of an inch to the foot. Quite recently a large amount of cast aluminium hollow-ware has been made for culinary use. Tea-kettles have been cast in one piece with walls only one-sixteenth of an inch thick. These castings possess the advantage that they are more malleable than any other cast metal. Thin castings of tea-kettles have been hammered in and bent almost double before breaking, Mr. W. S. Cooper, of Philadelphia, makes some remarkably large sand-castings, adding a little copper to reduce the shrink- age. Full-sized bath-tubs, 6 feet long, 2 feet wide, 2 feet deep, and three-eighths inch thick, with a roll rim, and weighing com- plete 140 lbs., are worthy of special mention, for such a cast- ing would not be easy to make in the best-flowing metal. Purification of Aluminium. Freeing from slag. — Deville gives the following information on this important subject : " It is of great importance not to sell any aluminium except that which is entirely free from the slag with which it was pro- duced and with which its whole mass may become impregnated. 448 ALUMINIUM. We have tried all sorts of ways of attaining this end, so as to ob- tain a metal which would not give any fluorides or chlorides upon boiling with water, or give a solution which would be pre- cipitated by silver nitrate. At Glaciere we granulated the metal by pouring it while in good fusion into water acidulated with sulphuric acid ; this method partially succeeded. But the pro- cess which M. Paul Morin uses at present (1859), and which seems to give the best results, is yet simpler. Three or four kilos of aluminium are melted in a plumbago crucible without a lid, and kept a long time red-hot in contact with the air. Al- most always acid fumes exhale from the surface, indicating the decomposition by air or moisture of the saline matter impreg- nating the metal. The crucible being withdrawn from the fire, a skimmer is put into the metal. This skimmer is of cast iron ; its surface ought not to be rough and it will not be wetted by the aluminium in the least during the skimming; it may be of advantage to oxidize its surface with nitre before using. The white and slaggy matters are then removed, carrying' away also a little metal, and are put aside to be remelted. So, in this purification, there is really no loss of metal. After having thus been skimmed, the aluminium is cast into ingots. This operation is repeated three or four times until the metal is per- fectly clean, which is, however, not easily told by its appearance ; for, after the first fusion, the crude aluminium when cast into ingots has a brilliancy and color such as one would judge quite irreproachable, but the metal would not be clean when it was worked, and especially when polished would present a multi- tude of little points called technically ' piqiires,' which give to its surface, especially with time, a disagreeable look. Alumin- ium, pure and free from slag, improves in color on using. It is the contrary with the impure metal or with aluminium not free from slag. When aluminium is submitted to a slow, corrod- ing action, its surface will cover itself uniformly with a white, thin coating of alumina. However, any time that this layer is black or the aluminium tarnishes, we may be sure that it con- tains a foreign metal, and that the alteration is due to this im- purity." WORKING IN ALUMINIUM. 449 Freeing from impurities. — Again Deville is the authority, and we quote his advice on the subject: — " A particular characteristic of the metallurgy of aluminium is that it is necessary, in order to get pure metal, to obtain it so at the first attempt. When it contains silicon, I know of no way to eliminate it: all the experiments which I have made on the subject have had a negative result; simple fusion of the metal in a crucible, permitting the separation by liquation of metals more dense, seems rather to increase the amount of sil- icon than to decrease it. When the aluminium contains iron or copper, each fusion purifies it up to a certain limit, and if the operation is done at a low heat there is found at the bottom of the crucible a metallic skeleton containing much more iron and copper than the primitive alloy. At first I made this liqua- tion in the muffle of a cupel furnace, in which process the ac- cess of air permitted the partial oxidation of these two metals. The little lead which aluminium may sometimes take up may thus be easily separated. Unfortunately, the process does not give completely satisfactory results. It is the same in fusing impure aluminium under a layer of potassium sulphide, KjSj; there is a partial separation of the lead, copper, and iron. That which has succeeded best with us is the process which we have employed for a long time at Glaci^re, and which consists in melting the aluminium under nitre in an iron crucible. We have in this way improved the quality of large quantities of aluminium. The operation is conducted as follows : Aluminium has generally been melted with nitre in order to purify it by means of the strong disengagement of oxygen at a red heat, no doubts being entertained as to the certainty of the result. But it is necessary to take great care when doing this in an earthen crucible. The silica of the crucible is dissolved by the nitre, the glass thus formed is decomposed by the aluminium, and the siliceous aluminium thus formed is, as we know, very oxidizable, and especially in the presence of alkalies. So, the purification of aluminium by nitre ought to be done in a cast- iron crucible well oxidized itself by nitre on the inside." 29 45 O ALUMINIUM. " On mfelting aluminium containing zinc in contact with the air and at a temperature which will volatilize the zinc, the largest part of the latter burns and disappears as flaky oxide. To obtain a complete separation of the two metals it is neces- sary to heat the alloy to a high temperature in a brasqued cru- cible. This experiment succeeds very well, but it is here shown that the aluminium must oxidize slightly on its surface, for some carbon is reduced by the aluminium from the carbonic oxide with which the crucible is filled. This carbon thus sep- arated is quite amorphous.'' Dr. Lisle, of Springfield, O., tested the removal of zinc from aluminium by distillation and succeeded in obtaining a product with 98 per cent, of aluminium from which the zinc had been completely removed. If aluminium containing tin is melted with lead, the latter sinks with the tin, removing it almost com- pletely from the aluminium, but the metal remaining retains a little lead. In an experiment made by the author, aluminium with 10 per cent, of tin was treated in this way, but the alu- minium retained nearly 7 per cent, of lead, giving it a blue color and large crystalline structure. M. Peligot is reported by Deville to have succeeded in cupelling aluminium with lead, whereby impure, tough metal became quite malleable. It may be that the small percentage retained by aluminium when melted with lead is removed by fusion on a cupel, but I have been unable to perform any operation with aluminium at all analogous to the cupellation of silver with lead. G. Buchner states that commercial aluminium contains con- siderable quantities of silicon, which by treatment, when melted, with hydrogen, evolves hydrogen silicide. This does not result if arsenic is present. To test this point, I took a sample of aluminium containing 4 per cent, of silicon, and 94 per cent, of aluminium. This was melted at a low red heat in a sand crucible and hydrogen gas run in for 12 minutes. On pouring out, the crucible was unat- tacked, but the metal was identical in color and structure with that not treated. This was repeated several times, hydrogen WORKING IN ALUMINIUM. 45 I gas being passed in as long as 20 minutes with the metal at red heat, but no apparent change in the purity of the metal re- sulted. Similar experiments were made with a current of sulphuretted hydrogen gas, with a view of removing the iron. No improve- ment in the looks of the aluminium was apparent. If, however, air was blown into the melted metal, an improvement was made. The aluminium was at a bright red heat, and air blown in for 5 minutes, at the end of which time about 5 to 10 per cent, of dross composed of mixed metal and oxide was formed, and the remaining metal was whiter, of a finer grain, and evidently much improved. Prof. Mallet * made some very accurate estimations of the atomic weight of aluminium (which he found to be 27.02), and obtained the chemically pure metal required for his work by the following process, which is quite applicable when studying the properties of the pure metal, yet is of course altogether out of the question as an industrial operation. The purest com- mercial metal was bought, and on analysis was found to con- tain — Aluminium 96.89 per cent. Iron 1.84 " Silicon 1.27 " This was treated with liquid bromine and converted into bro- mide. This salt was then purified by fractional distillation, the temperature being very carefully regulated, and the operation repeated until the product was perfectly colorless, and dissolved in water without leaving any perceptible impurity. The reduc- tion was accomplished with difiSculty and much loss by treat- ing with sodium in a crucible made of a mixture of pure alu- mina and sodium aluminate. The metal obtained gave on analysis no weighable quantity of impurities, and the properties mentioned in Chapters III. and IV. as Mallet's observations are those quoted from his report on this pure metal. * Philosophical Magazine, 1880. 45-2 ALUMINIUM. Professor Le Verrier states * that by a simple fusion of alu- minium under a layer of an alkaline fluoride the amount of sili- con is easily diminished. He states that a specimen containing 0.81 per cent, of silicon, contained after one such fusion only 0.57 per cent. If aluminium is overheated in the crucible, it has a great tendency to absorb gas (like silver), and gives it out in setting, producing blow-holes in the castings. It is therefore important to carefully regulate the temperature of melting. Coehn re- commends the use of a very small amount of sodium, to take gas out of the metal, only enough being used to form a thin film over the melted metal. Annealing. By heating to very low redness and cooling quickly, as by dropping into water, aluminium becomes soft. To get the best results, the metal should be heated until it just begins to glow in the dark, or the object is rubbed with a lump of fat, and the moment that the black trace left by the carbonization of the fat disappears, the metal is removed from the annealing oven. Great care is necessary in annealing thin sheets which are being beaten into leaf, to avoid melting them. Fine wire can be an- nealed over the chimney of an Argand burner. If it is neces- sary that the heat must be kept below the point where the metal would bend and lose its shape, the articles can be heated in boiling linseed oil and allowed to cool very gradually with the oil. Very thin sheets or wire can be softened by putting into boiling water and letting them cool with the water. (See also pp. 70, 74.) Hardening. By hammering, rolling, or drawing, aluminium becomes sen- sibly harder and stiffer, so that it becomes elastic enough to be used even for hair-springs for watches. If castings of alumin- ium are made a little larger than the finished article desired, ♦ Comptes Rendus, July, 1894, p. 13. WORKING IN ALUMINIUM. 453 and drop-forged cold in dies of the right size, the hardness is much increased, and it becomes much better able to stand wear in bearings where great weight does not have to be endured, e.g., in surveying instruments. Queen &Co., of Philadelphia, state that they find it best, however, to bush all sockets in alu- minium castings with brass, when making a bearing or tapping in a screw. The most careful tests fail to show the slightest increase in hardness in metal which has been chilled, as practised with cast-iron. Surfaces cast in cold, metallic moulds seem as soft as those cast in sand. The Eureka Tempered Copper Company of Northeast, Penn- sylvania, claim that they have hardened aluminium castings in the same way as they harden copper, but I have seen none of their work. Rolling. Before rolling a bar of aluminium it is well to soften it, and to taper down a "lead" by hammering. The metal forges well under the hammer at a low red heat. The metal for rolling had better be cast into plates in covered iron ingot-moulds, and the surfaces planed to remove small irregularities. The rolling is not difficult, except that a large amount of power is required (about as much for cold aluminium as for hot steel), and as the metal quickly gets hard it must be annealed often. It is recommended that the metal be brought warm under the rolls, and, if possible, elongated lo to 20 per cent, with the first pass, in order to entirely destroy the crystalline structure of the metal. The annealing is repeated between each pass until the sheet is about 3 millimetres thick, after which it can generally be rolled with fewer annealings, sometimes without any at all. Rolls warmed to 100-150° C. work better than cold ones. Alu- minium has been rolled down to the thinness of tissue-paper. Thin-rolled sheets may be still further extended out by beat- ing into leaf. The gold-beaters are said to have no special difficulty in doing this, except that more frequent annealings 454 ALUMINIUM. are necessary than with gold or silver. M. Degousse was the first to make this leaf, in 1859; he states that the tempering must be done by warming only to 100° or 150° C, an actual glowing heat proving very unsuitable. Aluminium leaf is made as thin as ordinary gold or silver leaf, and this property would, therefore, establish aluminium as next to these noble metals in the order of malleability. The Mannesmann process of cold rolling is applicable to alu- minium, by which tubes of all shapes and sizes can be made. Mr. Elwood Ivins, of Philadelphia, has a special process for making metallic tubes, which is a sort of rolling process on a mandril, by which he makes aluminium tubes of any size, shape or thickness of walls. I have seen a tube made by this process 10 metres long by i millimetre in diameter. Drawing. Prof. Thurston places aluminium as sixth in the order of duc- tility, being preceded by gold, silver, platinum, iron and cop- per, but it is doublful if it does not rank equally as high as iron. Deville states that in 1855 M. Vangeois obtained very fine wire with metal far from being pure. Bell Bros., at New- castle-on-Tyne, recommended that the metal for drawing be run into an open mould so as to form a flat bar of about one-half inch section, the edges of which are beaten very regularly with a hammer. The diameter should be very gradually reduced at first, with frequent heating. When the threads are required very fine the heating becomes a very delicate operation, on ac- count of the fineness of the threads and the fusibility of the metal. The gauge should be reduced by the smallest possible gradations, when wires may be obtained as fine as a hair. Aluminium tubes are drawn, either round or square, from sheet which has been soldered together or from cast rings of the required section ; the first method is said to be preferred. As the aluminium quickly loses its temper it must be annealed after each extension. working in aluminium. 455 Stamping and Spinning. Aluminium can be spun on the lathe into all sorts of round and hollow forms ; it may also be pressed or stamped into shape in the cold ; it is of* advantage in doing this to use a kind of varnish composed of 4 parts of oil of turpentine and i part of stearic acid. Soap-water is always to be avoided. Grinding, Polishing and Burnishing. When cast carefully it can be filed without fouling the file. Spun and stamped articles of aluminium can easily be ground by using olive oil and pumice. A fine steel scratch-brush run at a high speed will give a good polish to sand castings, and remove the yellowish streaks that may have been produced by too hot metal. If sheet metal is thus treated it gives a frosted appearance, which forms a beautiful finish. Biederman makes the following remarks on polishing : " The use of the old means of polishing and burnishing metals, such as soap, wine, vinegar, linseed-oil, decoction of marshmallow, etc., is not effective with aluminium, but, on the contrary, is even harmful, because, using them, the blood stone and the burnishing iron tear the metal as fine stone does glass. Oil of turpentine has also been used, but with no good effect. Mourey found, after many at- tempts, that a mixture of equal weights of olive oil and rum, which were shaken in a bottle till an emulsified mass resulted, gave a very brilliant polish. The polishing stone is dipped in this liquid, and the metal polished like silver, except that one must not press so hard in shining up. The peculiar black streaks which form under the polishing stone need cause no trouble ; they do not injure the polish in the least, and can be removed from time to time by wiping with a lump of cotton. The best way to clean a soiled surface and remove grease is to dip the object in benzine, and dry it in fine sawdust." Mr. J. Richards found that when buffing in the ordinary way the dark-colored burnishing powder cut into the metal and filled its pores with black specks. He found the best means of 456 ALUMINIUM. burnishing is to use a piece of soft wood soaked in olive oil ; this closes the grain, and gives a most brilliant finish. The Pittsburgh Reduction Company polish sheet aluminium with a sheep-skin, chamois-skin or rag buff, using rouge, the same as for brass. The particular requisite of a polishing pow- der for aluminium is that it be very finely ground. This com- pany sells a polishing powder called "Almeta Polish," which consists of Stearic acid i part. Fuller's earth i " Rotten stone 6 " The whole ground very fine and well mixed. Engraving. Kerl & Stohman : Aluminium resists the action of the en- graving tool, which slides upon the surface of the metal as upon hard glass. But as soon as a varnish of 4 parts of oil of turpentine and i of stearic acid, or some olive oil mixed with rum is used, the tool cuts into it as into pure copper. Cleaning and Pickling: Mat. Dirt and grease are removed easily by dipping in benzine or turpentine. To obtain the beautiful "mat" or frosted efifect, which alu- minium takes as easily as silver, Deville recommended dipping for an instant in a very dilute solution of caustic soda, washing in a large quantity of water, and last dipping in strong nitric acid. An English writer recommends dipping i^ minutes in a solution of 3 ounces of caustic potash to a quart of water, wash thoroughly, and then dip in a mixture of 3 measures strong nitric acid to 2 measures sulphuric acid. By the above treatments, any elements which might contaminate the alumin- ium, except a very large proportion of silicon, are dissolved from the surface. If, as Mourey recommends, some hydroflu- oric acid is added to the nitric, the silicon is more actively attacked. working in aluminium. 45 7 Welding. Aluminium cannot be welded except by the electrical pro- cess, and then only with difficulty. The high electric conduc- tivity, the high specific heat and latent heat of fusion, and par- ticularly the mushy state into which the metal passes some considerable time before its real melting point, make the oper- ation hard to perform satisfactorily. In the early days of elec- tric welding it could not be done at all, but the Thomson Elec- tric Welding Company state that they have constructed a special machine for this kind of material, and can now make the welds rapidly and satisfactorily. Soldering Aluminium. A satisfactory solder for use on any metal should fill the fol- lowing requirements :* 1. It should fuse readily. 2. It must alloy easily with the metal; in common parlance, it must bite. 3. It must be tough. 4. It must not disintegrate. 5. It should be of the same color as the metal. 6. It should not discolor with age. 7. It should not be too expensive. Aluminium is a difficult metal to solder properly for three particular reasons : I. It is difficult to expose a bare surface of aluminium to the ^ action of the solder. Grease and dirt can be easily enough removed, but there is always present a thin, continuous coating of alumina which effectually prevents the solder from getting to the metal beneath. It might be thought that a thorough sand-papering or fiHng of the surfaces immediately before sol- dering would overcome this, but we find it of absolutely no use ; the reason is that the thin, invisible skin of alumina forms * For a more extended essay on the properties of a good solder, see a paper by the writer in the "Aluminium World," New York, October, 1894. 458 ALUMINIUM. instantly, as quickly as the metal is laid bare. The ordinary fluxes used in soldering have no effect at all on this coating. To overcome this difficulty, it is necessary either to use some particular flux which can remove this oxide and preserve the surface clean until the solder can take hold, or else to incor- porate into the composition of the solder some ingredient which can do the same thing. The latter device has been the most successful, as theoretically it should be ; for if the solder as it were carries its own flux, the action of the flux and the taking hold of the solder must be simultaneous, and therefore most effective. 2. Aluminium has a high conductivity for heat. This inter- feres greatly with the attempt to produce a local temperature at the joint high enough for the solder to alloy ; which causes the solder to chill quickly in the joint, particularly when work- ing on bulky articles. The only way to overcome this diffi- culty is to use very hot soldering-bolts and to work slowly, so as to get the metal at the joints hot. 3. Aluminium is highly electro-negative. This property causes the first difficulty, the instantaneous formation of a thin skin of oxide, but it also operates in another way after the joint is made. It causes galvanic action to arise at the joint between the aluminium and the solder, and causes the joint to weaken rapidly. To render this action as small as possible, the solder should be made as far as practicable of metals near to alu- minium in the galvanic series, such particularly as zinc. With the preceding introduction to the subject, we will con- sider the various solders which have been proposed and used, giving first Deville's views on the question, for even at the time of writing his book (1859), the difficulty of soldering alumin- ium properly was regarded as one of the greatest obstacles to its industrial employment. Deville : " Aluminium may be soldered, but in a very im- perfect manner, either by means of zinc, or cadmium, or alloys of aluminium with these metals. But a very peculiar difficulty arises here — we know no flux to clean the aluminium which WORKING IN ALUMINIUM. 459 does not attack the solder, or which, protecting the solder, does not attack the aluminium. There is also an obstacle in the particular resistance of aluminium to being wetted by the more fusible metals, and on this account the solder does not run between and attach itself to the surfaces to be united. M. Christofle and M. Charriere made, in 1855, during the Exposi- tion, solderings with zinc or tin. But this is a weak solder and does not make a firm seam. MM. Tissier, after some experi- ments made in my laboratory, proposed alloys of aluminium and zinc, which did not succeed any better. However, M. Denis, of Nancy, has remarked that whenever the aluminium and the solder melted on its surface are touched by a piece of zinc, the adhesion becomes manifest very rapidly, as if a partic- ular electrical state was determined at the moment of contact. But even this produces only weak solderings, insufficient in most cases." " A long time ago, M. Hulot proposed to avoid the difficulty by previously covering the piece with copper, then soldering the copper surfaces. To efifect this, plunge the article, or at least the part to be soldered, into a bath of acid sulphate of copper. Put the positive pole of a battery in communication with the bath, and with the negative pole touch the places to be covered, and the copper is deposited very regularly. M. Mourey has succeeded in soldering aluminium by processes yet unknown to me ; samples which I have seen looked excellent. I hope, then, that this problem has found, thanks to his ingenu- ity, a solution ; a very important step in enlarging the employ- ment of aluminium." Mourey's first practicable solders for aluminium were of zinc and aluminium, and of two kinds — hard and soft. He used a soft solder to first unite the pieces, and afterwards finished the soldering with a less fusible one. These solders contained — I. II. Aluminium 20 15 Zinc 80 85 The alloys with the larger proportion of zinc are the easiest III. IV. V. 12 8 6 88 92 94 46o ALUMINIUM. melting or softest ones, one such as IV. being used for ordin- ary work, while II. was used for brazing. These solders have the disadvantage that on melting they oxidize very easily, and in consequence of the film of oxide thus formed the work is so much more difficult. This difficulty can be overcome by dip- ping the small grains of solder in copaiva balsam and turpen- tine, which keep out the air, and act as reducing agents during the operation. The new solders subsequently used were sim- pler in application, for the work was finished with one solder and the moistening with balsam was rendered unnecessary. Mourey improved upon the zinc-aluminium solders by add- ing copper, using five different alloys of these three metals ac- cording to the objects to be soldered. They contained — I. II. III. IV. v. Aluminium 12 9 7 6 4 Copper 8 6 5 4 2 Zinc 80 85 88 90 94 The following directions are given for preparing these alloys:* " To make the solder, first put the copper in the crucible. When -it is melted, then add the aluminium in three or four portions, thereby somewhat cooling the melted mass. When both metals are melted, the mass is stirred with a small iron rod, and then the required quantity of zinc added, free from iron, and as clean as possible. It melts very rapidly. The alloy is then stirred briskly with an iron rod for a time, some fat or benzine being meanwhile put in the crucible to prevent contact of the metal with air and oxidation of the zinc. Finally the whole is poured out into an ingot mould previously rubbed with benzine. After the addition of zinc, the operation must be finished very rapidly, because the latter will volatilize and burn out. As soon as the zinc is melted the crucible is taken out of the fire. Only zinc free from iron can be used, since even an apparently insignificant amount of this impurity injures the qualities of the solders very materially in regard to dura- bility and fusibility. * Das LSthen, by Edmund Schlosser, \ ienna, 1880, p. loi. WORKING IN ALUMINIUM. 46 1 " The separate pieces of metal to be soldered together are first well cleaned, then made somewhat rough with a file at the place of juncture, and the appropriate solder put on it in pieces about the size of millet grains. The objects are laid on some hot charcoal, and the melting of the solder effected by a blast lamp or a Rochemont turpentine-oil lamp. During the melt- ing of the solder, it is rubbed with a little soldering iron of pure aluminium. The soldering iron of pure aluminium is essentially a necessity for the success of the operation, since an iron of any other metal will alloy with the metals composing the solder, while the melted solder does not stick to the iron made of aluminium. " For quite small objects, as for jewelry, solder I. is used ; for larger objects and ordinary work IV. is more suitable, and is the solder most used. These alloys work so perfectly that plates soldered together never break at the joint when bent back and forth, but always give way in other places ; which is a result not always possible in the best soldering of plates of silver." Bell Bros, used the above solders in their works at Newcastle, and in a description of the soldering operation state the follow- ing facts in addition to those already given :* " In the operation of soldering, small tools of aluminium are used, which facilitate at the same time the fusion of the solder and its adhesion to the previously prepared surfaces. Tools of copper or brass must be strictly avoided, as they would form colored alloys with the aluminium and the solder. The use of the little tools of aluminium is an art which the workman must acquire by practice. At the moment of fusion the work needs the appH- cation of friction, as the solder suddenly melts very completely. In soldering it is well to have both hands free, and to use only the foot for the blowing apparatus." We also find the following alloys credited to Mourey as used by him for soldering aluminium, probably with the blow-pipe :t * Chemical News, iv., 81. t Dingier, 166, 205. 462 ALUMINIUM. Aluminium 30 20 Copper 20 15 Zinc 50 65 While it is true that Mourey received from the Societe d'Encouragement a prize for the solders he had found, and while they were the best then in use, yet every one knows that they were not satisfactory. Their melting points were too high, and it required great skill to make neat joints. Even as late as 1890 we find a writer saying, " The want of a suitable solder for aluminium has greatly retarded its use in the arts," although many attempts had meanwhile been made to provide solders superior to Mourey's. Col. Wm. Frishmuth * recommends a solder containing: — Aluminium 20 Copper 10 Zinc 30 Tin 60 Silver 10 Later, Col. Frishmuth f states that the solder just given is used for fine ornamental work, while for lower-grade work he uses the following : — Tin Bismuth . I. II. III. 95 97 98-99 S 3 ' 2-1 He recommends for a flux, in all cases, either paraffin, stearin, vaselin, copaiva balsam, or benzine. In the solder for fine work, if aluminium is used in larger quantity than recom- mended, the solder becomes brittle. Schlosser % recommends two solders containing aluminium as especially suitable for soldering dental work, on accbunt of their resistance to chemical action. Copper cannot be allowed in alloys intended for this use, or only in very insignificant * Techniker, vi. 249. t Wagner's Jahresb., 1884. X Das Lothen, p. 103. WORKING IN ALUMINIUM. 463 quantity, since it is so easily attacked by acid food, etc. Since these two alloys can probably be used also for aluminium dental work, we subjoin their composition — Platinum-aluminium solder. Gold-aluminium solder. Gold 30 Gold.' 50 Platinum I Silver 10 Silver 20 Copper 10 Aluminium 100 Aluminium 20 M. Bourbouze states that the difficulties met with in solder- ing aluminium are satisfactorily overcome by the following process : — *"The parts to be united are subjected to the ordinary op- eration of tinning, except that in place of pure tin an alloy of tin and zinc, or, better, of tin, bismuth and aluminium is used. However, preference is given to an alloy of tin and aluminium, mixed in different proportions to suit the work put on the joint. For those which are to be subsequently worked, an alloy of 45 parts tin and 10 parts aluminium should be used. This solder is malleable enough to resist hammering, drawing, or turning. Pieces not to be worked after soldering may, whatever the metal to be united to the aluminium, be solidly soldered with a tin solder containing less aluminium. Neither of these solders requires any preparation of the pieces, and the last one may be applied with a common soldering-iron. To unite other metals to aluminium it is best to coat the part with pure tin, the aluminium is coated with one of the above alloys, the joint closed and finished by heating in the usual manner." O. M. Thowless has patented the following solder for alu- minium, and method of applying it:t The alloy is com- posed of — Tin 55 parts. Zinc 23 " Silver 5 " Aluminium., 2 " * Comptes Rendus, 98, 1490. t English Patent, 10,237, ^""S- '9> '885. 464 ALUMINIUM. The silver and aluminium are first melted together, the tin added, and lastly the zinc. The metallic surfaces to be united are immersed in dilute caustic alkali or a cyanide solution, washed and dried. They are then heated over a spirit lamp, coated with the solder and clamped together, small pieces of the alloy being placed around the joints. The whole is then heated to the melting point of the solder, and any excess of it removed. No flux is used. J. S. Sellon patents the following method:* The aluminium surfaces are cleaned by scraping and covered with a layer of paraffin wax as a flux. They are then coated by fusion with a layer of an alloy of zinc, tin and lead, preferably in the propor- tions — Zinc 5 Tin 2 Lead : The metallic surfaces thus prepared are soldered together in the usual way with any good solder. C. Sauer, of Berlin, patents the following :f An alloy is made of Aluminium 9 parts. Silver i, 2, 3 or 4 " Copper 2, 3, 4 or 5 " He also claims the above alloy, to which is added i or 2 parts of zinc, cadmium or bismuth, or even of a fusible metal such as Wood's alloy. A small proportion of gold may be added. In making, the copper and silver are first melted, molten alumin- ium, added and the solid zinc last dropped in. In using, the alloy is broken small, spread between the surface to be sold- ered, previously heated, and the joint then made with a solder- ering-iron. No flux is required. J. Novell states that the following alloys can be used on alu- minium, aluminium bronze or for any other metals: * English Patent, 11,499, Sept. 26, 1885. t English Patent, 8,551, May 5, 1892. I Comptes Rendus, 116, 256. WORKING IN ALUMINIUM. 465 Melting point. No. I. Pure Tin 235° C. 2. Tin 1000, Lead 50 280-300° 3. Tin 1000, Zinc 50 280-330° 4. Tin 1000, Copper 10 to 15 350-450° 5. Tin looo, Nickel 10 to 15 ~. 350-450° 6. Tin 900, Copper 100, Bismuth 2 to 3 350-450° Nos. I, 2, and 3 are for pure aluminium, having a white color ; Nos. 4 and 5 are harder and stronger, but are light-yel- low; No. 6 is yellow, and best adapted for soldering aluminium bronze. By reference to Deville's statement, (p. 459), it will be seen that aluminium was soldered with tin in 1855, but the joints were found too weak ; and it has been the writer's experience that such joints quickly disintegrate and fall apart. Mr. C. H. Land, of Detroit, Mich., states, however, that joints of pure tin can be made strong and permanent by oper- ating in the following manner : * The pieces of aluminium to be ■ soldered are immersed in molten tin, and while submerged, the parts to be soldered rubbed briskly with a brush having steel bristles. This removes the skin of oxide and permits the tin to unite firmly with the aluminium. Edges thus treated can be sweated together or soldered together with ordinary solder. Aluminium can thus be soldered also to copper, brass, galvan- ized-iron or cast-iron. It is stated by Mr. Laird that joints made four years ago are still strong, and show no signs of coming apart. Since the writer's experience with pure tin used in the ordinary way is just the reverse of this, it may be that the wetting of the edges by rubbing in the molten tin is of great benefit in producing a permanent joint. Exactly the same method of procedure was patented in England by L. Oliven, more than two years later, f The Aluminium Company at Neuhausen, Switzerland, put on the market in 1890 specially-prepared sheet aluminium, *U. S. Patent, 440,952, Nov. 18, 1890. t English Patent, 23,477, Dec. 20, 1892. 30 466 ALUMINIUM. which was easier to solder .than ordinary aluminium. The special preparation was not divulged, but I have heard that aluminium containing I or 2 per cent, of zinc solders more easily than the pure metal. The edges to be joined were not scraped, but a flux of resin, tallow and zinc chloride was to be used. The same firm also recommended depositing a thin film of copper on the edges to be joined, and then soldering on the copper. The trouble with this device is that the copper is apt to shell off by the sudden heating. The same firm also subsequently recommended the use of cadmium chloride as a flux, when doing blow-pipe work, but this salt quickly absorbs moisture from the air and becomes worthless for the purpose. Otto Nicolai, of Wiesbaden, and Carn Langenbach, have patented * the use of the chloride, sub-chloride, bromide or iodide of silver as a flux. Their action would be, of course, to deposit metallic silver on the aluminium. The salt is strewn as powder along the joint, and the soldering done with any good solder. The use of silver chloride in this way was patented in the United States previous to the above, date. The flux is certainly of advantage to use, but is too expensive for ordinary work. Wegner and Guhrsf recommend using as a flux a mixture of 80 parts stearic acid, 10 parts zinc chloride, and 10 parts stannous chloride, SnCl^. They claim excellent results wiien this is used with a solder of 80 parts tin to 20 zinc. E. Werner, of Hamburg, | proposes to use as a flux when soldering aluminium the cyanide of the metal used as solder, e. g., cyanide of tin. The solder and flux are strewn along the joint and melted with the blow- pipe. B. I. Roman § patents a solder composed of zinc 50 parts, * English Patent, 16,292, Sept. 12, 1892. t English Patent, 512, Jan. 10, 1893. X German Patent, 75,659. § English Patent, Sept. 19, 1893, No 17,623. WORKING IN ALUMINIUM. 467 tin 34, aluminium 9, nickel 5, silver 2. No flux is used with it, and an aluminium bolt is recommended. The Alsite Aluminium Solder, made in New York, was ex- tensively advertised during 1893 and 1894, and at a demonstra- tion before the Franklin Institute, Philadelphia, the inventor did some very neat and solid work with it, using the blow-pipe. The melting point, however, was high, and considerable skill was required to use it. The composition was not divulged. After the lapse of a year, however, the work done has tumbled apart by the disintegration of the solder, and even the bar of solder itself has become black and so brittle that it will not support its own weight. The writer's father, Mr. Joseph Richards, of the Delaware Metal Refinery, Philadelphia, one of the most extensive makers of lead-tin solder in the United States, has experimented a great deal with aluminium solder, and finally concluded that a small amount of phosphorus was a great improvement to any other solder hitherto used. The composition has been patented in the United States and England * and describes as preferable a solder composed of — Tin 32 parts = 78.34 per cent, tin Zinc 8 parts = 19.04 " zinc. Aluminium i part = 2.38 " aluminium. Phosphor tin I part = 0.24 " phosphorus. On re-melting some of this solder, a liquation was noticed, and it was inferred that the more fusible part was probably a better alloy for soldering, being less likely itself to liquate. It was therefore analyzed, and found to contain 71.65 per cent, of tin, corresponding closely to the formula Sn^Zns, which would call for 70.7 per cent. The solder as now made contains i part aluminium, i part phosphor tin, 1 1 parts zinc and 29 parts tin, giving it 71.2 per cent, of tin. As regards the use of this solder, it may be said that it fills most of the conditions of a satisfactory solder. It fuses easily, » United States Patent, 478,238, July 5, 1892; English Patent, 20,208, of 1892. 468 ALUMINIUM. at a heat attainable witji a copper or nickel bolt ; it has a won- derful ability to take hold on the metal, for I have heated a piece of sheet aluminium and then firmly traced my name on it with a stick of solder used as a pencil ; it is so tough that if a joint is well made the metal will break before the solder ; it does not disintegrate, for joints made three years ago are still firm ; it is very nearly the color of aluminium, but darkens slightly on standing some time ; when the article is in constant wear, however, the solder retains its bright color, or when dis- colored it becomes bright again by polishing ; the solder is not expensive. Joints may be made with the bolt, the blow-pipe, or by sweating together. The edges to be joined are filed or scraped clean immediately before soldering, then, if the piece will allow, heated to a temperature at which the solder melts and the edges are tinned by rubbing with a stick of solder. If the whole piece cannot be heated, the edges can be tinned by heat- ing with a tinned bolt, and rubbing in the melted solder briskly. Any surplus solder is removed from the edges by a small scraper, while still hot. The prepared edges are then soldered together in any way desired. For a lap-joint, the edges are over-lapped, the soldering bolt passed along, and a little extra solder melted in the joint. For a joint at an angle, it is neces- sary that the bolt be shaped to fit, as the solder must be rub- bed in well at the edges. No flux of any kind is to be used either on the bolt or the joint. In making a lock-seam, the edges of the aluminium should be coated with the solder as above described before being turned over, else the solder can- not soak into the joint. Common sheet-tin does not need such preparation, because the whole sheet is already tinned to start with. In brief, to put it in a way which any tinsmith can un- derstand, aluminium is similar to copper and black-iron, not like tinned iron, and the edges to be joined must be prepared for soldering. The solder answers equally well for uniting alu- minium to copper, brass, German-silver, steel or cast-iron, which work has been repeatedly performed, and found to make a permanently good joint. WORKING IN ALUMINIUM. 469 This solder is sold in Great Britain by Mr. Archibald Briggs, of Dundee, Scotland, and on the Continent by the Aluminium Industrie Actien-Gesellschaft at Neuhausen, Switzerland. Dr. Kiliani, director of the latter's works, pronounced it the only satisfactory solder for use with the bolt. It is the only solder used by the large makers of aluminium goods, and its use is increasing rapidly with the growth of the aluminium industry. Coating Metals with Aluminium. Many attempts have been made to give baser metals a thin coating of aluminium and thus impart to them superficially the resisting properties of that metal. We may distinguish broadly two different methods of procedure used to accomplish this — the chemical (and electric) and the mechanical. Aluminium is not thrown down in a metallic state from its solutions by any other metal, and therefore it cannot be obtained as a plating by dipping the article in any solution of its salts. It can, how- ever, be deposited electrically from aqueous solutions, using soluble aluminium anodes, as has been already described in Chapter XI. Aluminium can also be deposited electrolytically in the solid state from a fused bath of its chlorides, etc., but, although Deville says that this principle can be utilized for coating other metals with aluminium, yet the metal is never deposited in a dense, compact film, but more or less as a powder mixed with carbon and other impurities, and satisfactory results cannot be obtained. The mechanical methods alluded to are conducted in two ways, either by uniting thin sheets of aluminium to the surface of another metal (veneering), or by using aluminium powder and burning in (aluminizing). Of the practice of veneering with aluminium, Deville says in 1859: "M. Sevrard succeeded in 1854 in plating aluminium on copper and brass with considerable perfection. The two metallic surfaces being prepared in the ordinary manner and well scoured with sand, they are placed one on the other and held tightly between two iron plates. The packet is then 470 ALUMINIUM. heated to dark redness, at which temperature it is strongly compressed. The veneer becomes very firmly attached, and sheets of it may be beaten out. I have a specimen of such work perfectly preserved. The delicate point of the operation is to heat the packet just to that point that the adherence may be produced without fusing the aluminium, for when it is not heated quite near to this^fusing point the adherence is incom- plete. Experiments of this kind with copper and aluminium foil did not succeed, for as soon as any adherence manifested itself the two metals combined and the foil disappeared into the copper. In an operation made at too low a temperature, the two metals, as they do not behave similarly on rolling, be- come detached after a few passes through the rolls. Since then, the experiments in veneering aluminium on copper, with or without the intervention of silver, have succeeded very well." Deville stated later, in 1862, that Chatel had brought this art to perfection, the veneered plates being used largely for reflectors, etc., in place of silver-plated material. Dr. Clemens Winckler * gives his experience in this line as follows: "The coating of other metals with aluminium by the so-called plating method is, according to my own experience, possible to a certain degree, but the product is entirely useless, every plating requiring an incipient fusing of both metals and their final intimate union by rolling. The ductility of alumin- ium is, however, greatly injured by even a slight admixture with other metals ; iron makes it brittle, and copper, in small per cent., makes it fragile as glass ( ?). If now it were possible in any way to fuse a coating of aluminium upon another metal, there would be formed an intermediate alloy between the two metals from which all ductility would be gone and which would crumble to powder under the pressure of the rolls, thus separat- ing the aluminium surface from the metal beneath. But even if it were possible in this way to coat a metal with a thin plate, it is still doubtful if anything would be attained thereby. For, * Industrie Blatter, 1873. WORKING IN ALUMINIUM. 4/1 while compact aluminium resists oxidizing and sulphurizing agencies, the divided metal does not. In powder or leaves aluminium is readily oxidized, as is shown by its amalgam becoming heated in the air and quickly forming alumina. In the form of a coating upon other metals it must necessarily be in a somewhat finely divided state, and hence would probably lose its durability." Dr. G. Gehring* has patented a method of aluminizing by which difficultly-fusible metals, stone-ware or the like, can be coated with aluminium. A mixture is made of a fatty acid (sebacic) and acetic acid with clay, etherized oil and alumin- ium (or aluminium bronze) in powder. This is spread evenly on the metal or object to be treated and then heated with a Bunsen burner using blast or in a muffle. The coating pro- duced is silver white, does not oxidize under ordinary condi- tions, stands heating in an ordinary fire, and can be highly pol- ished. It is stated! that this process is now largely made use of in Germany. Somewhat analogous results are obtained by Brin Bros, (p. 417) without the use of metallic aluminium (similar to those claimed also by Baldwin, p. 426), but while in Dr. Gehring's process the coating would be formed on any surface, in these other processes the presence of the metallic base is necessary, and an alloy with a few per cent, of aluminium is formed on the surface of the object and penetrates a little way into its interior. Such a coating, then, is simply a transformation of the outer layer of metal into an alloy with a small quantity of alumin- ium, and could possess very few of the qualities of aluminium, but might possess, as an alloy, qualities superior to those of the original metal. H. C. Broadwell, oi Philadelphia, claims that sheet-iron can be coated with aluminium by first cleaning the iron carefully, then immersing it in a bath of molten aluminium, and while im- mersed rubbing its surface vigorously with a steel brush. If a ♦German Patent, 29,891 (1885). t Engineering and Mining Journal, Feb. 13, 1886. 472 ALUMINIUM. temperature over a red-heat is used, the iron will probably be attacked, because this happens when melting aluminium in an iron crucible (p. 444). I cannot learn, however, that the pro- cess has been applied on a commercial scale. If such a pro- cess could be made practicable, we should have in the alu- minium-coated plates a rustless substitute for tinned sheet-iron, the only drawback to which would be that it is not so easily soldered as sheet-tin. Plating on Aluminium. Deville says: "The gilding and silvering of aluminium by electricity is very difficult to do satisfactorily and obtain the desirable solidity. M. Paul Morin and I have often tried it by using a bath of acid sulphide of gold or of nitrate of silver with an excess of sulphurous acid. Our success has only been partial. However, M. Mourey, who has already rendered great services in galvano-plasty, gilds and silvers the aluminium of commerce with a surprising perfection, considering the little time he has had to study the question. I also know that Mr. Christofle has gilded it, but I am entirely ignorant of the methods employed by these gentlemen.* The coppering of aluminium by the battery is easily effected by M. Hulot by using an acid bath of sulphate of copper." Tissier Bros, state that aluminium can be gilded without using a battery by preparing a solution as follows : " Eight grammes of gold are dissolved in aqua regia, the solution diluted with water and left to digest twenty-four hours with an excess of lime. The precipitate, with the lime, is well washed, and then treated with a solution of twenty grammes of hyposulphite of soda. The liquid resulting serves for the gilding of aluminium without the aid of heat or electricity, the metal being simply immersed in it after being previously well cleaned by the suc- cessive use of caustic potash, nitric acid, and pure water." * M. Mourey has since stated that his means are galvanic, and that be has no trouble in depositing silver and gold in six different colors — shining, matt, or dull — but does not describe his methods. WORKING IN ALUMINIUM. 473 Aluminium can be veneered with other metals in a manner strictly analogous to the reverse process described by Deville. For example, Morin describes the veneering with silver as fol- lows : " Sheet silver is laid on the clean aluminium surface, a steel plate placed over the silver, and the whole bound into a packet with fine copper wire. Two large cast-iron blocks are heated to a dark red heat, the packet placed between them and a pressure of i ton to the square centimetre (lo tons per square inch) applied gradually and sustained for 15 minutes. When removed from the hydraulic press they can be rolled like silvered copper when brought to the proper heat. The plating with gold succeeds best if a thin leaf of silver is slipped be- tween the two sheets of metal, the operation proceeding then exactly as above. Platinum may be plated on aluminium just as easily as silver." The firm of J. and A. Erbsloh, of Barmen-Wupperfield, Ger- many, put on the market copper-sheet on which aluminium has been rolled, but they keep their mode of procedure secret. They also roll together gold and silver with aluminium. Wegner and Guhrs, of Berlin, plate aluminium electrolyti- cally with gold, silver, nickel, copper, bronze or brass. Their process has been very successful in practice, depositing directly on the aluminium. The baths recommended are solutions con- taining potassium cyanide, and require less than the ordinary power for precipitation. The same investigators have discov- ered processes for coloring aluminium black, brown, or almost any other shade, the colors being permanent. Neeson, a German chemist, recommends first dipping the aluminium in alkali till bubbles of gas appear, then into a solu- tion of corrosive sublimate, then again into the caustic, and finally into a salt of the desired metal, which is then deposited on the aluminium as an adherent film. Uses of Aluminium. Deville wrote in 1862: "Aluminium is the intermediate metal between the noble and the base metals." This was true 474 ALUMINIUM. then of its price as well as of its properties ; it does not with- stand chemical agents in general as strongly as the noble metals, but it withstands air, water, sulphuric acid, nitric acid and sulphuretted hydrogen — which is not the case with iron, copper, or even silver. We have then a semi-noble metal ; but while silver, gold and platinum have extremely small prospect of becoming noticeably cheaper, yet the time is probably not far distant when we shall have our semi-noble metal at the price of the base ones. This affords the immense future for alumin- ium. Whatever its price, it can only replace gold or platinum because of its lightness ; it already replaces silver especially be- cause of its resistance to sulphur, as well as for its lightness, besides being cheaper ; it can only replace the common metals, at its present price, for uses where its lightness is an extraordi- nary advantage. But when its price is down to that of these baser metals, it will begin to replace them by virtue of its other superior qualities, chemical and physical ; aside from its light- ness it will win a large field simply in comparison with them on its merits as a metal. Thus, there are wide applications now almost unthought of, because the high price has been a blank wall to stop its use ; but as it cheapens more and more, we hear every day of new uses brought to light. Thus its sphere will widen until, since its ores are as cheap as those of iron, it will approximate in utility to that universal metal. At the time of this writing, (1895) there are only four metals which are cheaper bulk for bulk than aluminium ; viz. : iron, zinc, lead and copper ; and the amount of aluminium produced yearly is increasing much more rapidly than any of these. Aluminium has there- fore already won its place among the common metals of every- day life. It will, of course, be many years before it outstrips any of these, but I believe the ultimate goal of aluminium in- dustry will be reached only when it stands next in importance and value of annual production to iron. From this time forth, every year will see substantial advance towards this goal, and the next century may see this end attained. Chronologically, the first article made of aluminium was a WORKING IN ALUMINIUM. 475 baby-rattle intended for the infant Prince Imperial of France, in 1856. For this purpose it no doubt answered excellently, from its brightness, lightness, ring and cleanliness, but only a prince could afford to possess one in those days. In the next few years it was used for all sorts of articles of ornament and luxury. It was found well-suited for fine jewelry by reason of its adaptability to being cast and carved, the beautiful reflec- tions from a chased surface, its color, matching well with gold, and the absence of odor. But it did not keep its polish so well as gold, and perhaps more to the point, it did not stay in fash- ion long; so that the rage for aluminium jewelry subsided al- most as fast as it had arisen, and it is only quite lately that it is being used again in this way to any extent. Then the French, with their ability for producing artistic furniture, used it for in- laid work on carved mouldings, cabinets, table tops, etc., 'but this application never exceeded a limited extent. It is said that the Emperor's interest in aluminium, in 1854, was aroused partly by the idea that if it could be had cheaply it would wonderfully lighten the weight of military equipments, such as spurs, buttons, sword-handles, sabre-sheaths, helmets, and the imperial eagles. A helmet was made for the Empe- ror's cousin, the King of Denmark, which when gilded, orna- mented, and fitted up complete, weighed only one and one-fifth pounds. The weight of the imperial eagles was lessened from eight pounds to nearly three pounds, it being remarked that " since they were gilded, only the bearer perceived the differ- ence." When Garopon, in Paris, was furnished with very fine wire by Vaugeois, he was immediately successful in working it into embroidery, lace and passementerie. This use of alumin- ium has also a military bearing, since aluminium wire can be used instead of silver in embroidering banners, and especially in working figures and epaulets on soldiers' uniforms. Military uses. — Within the last five years, several govern- ments have taken up the questfon of aluminium for military uses. The Germans have taken the initiative. They appointed a commission to test its suitability for canteens, cooking uten- 476 ALUMINIUM. sils, pontoons, and, in fact, almost every other metallic part of a soldier's equipment. As a result of this inquiry the German army is being permanently equipped with aluminium cooking utensils, canteens and pontoons. Every ounce of weight thus saved means as many more cartridges carried per man. In the Russian army, ammunition wagons with aluminium frames are being tried. The United States have not officially adopted any aluminium articles in their military service, but Lieut. Brown has been making many of the service articles in aluminium and sending them to headquarters at Washington. It is to be hoped that his efforts will be successful, and that our country will not be behind Europe in increasing in every way the com- fort and efficiency of the military. Naval use. — Within a very short time it has become possible to build aluminium vessels. Escher, Wyss & Co., of Zurich, were the first in this line, building a naphtha launch entirely of aluminium, even to its smoke-stack and rigging. Several others have been built by the same firm ; also, a sailing yacht and a flat-bottomed boat for inland navigation in Africa. The naph- tha yacht " Mignon" built by them is 43 feet long, 6 feet beam, draft 2 feet 2 inches. The keel, stern and stern posts are of forged aluminium with a section of 7 in. by i in. The frames are angles of i inch wide by i inch deep, one-sixteenth inch thick. The shell is three thirty-seconds of an inch thick. The whole is held together by aluminium rivets. The rigging is of aluminium wire, not painted. All the machinery is of alu- minium, including the propeller, except the cranks and shaft- ing. The engine is 6 horse-power, and on the trial trip the boat attained a speed of eight miles an hour. A writer in Dingler's Polytechnic Journal compares 3 yachts of 10 tons displacement, made respectively of wood, steel and aluminium. He finds that the light frame of the latter permits heavier bal- last, thus lowering the centre of gravity, and increasing the stability. In reckoning the cost, the value of the worn-out hull was not considered, and aluminium was taken at its price in 1892, which is 50 per cent, above its present price. WORKING IN ALUMINIUM. 477 Wood. Steel. Aluminium. Relative cost 1.0 i.o 1.8 Centre of gravity below water 0.43 m. 0.47 m. 0.65 metre. Relative sail area i.oo 1.06 1.35 Relative speeds i.oo 1.03 1.16 The calculation with regard to the stability, as shown by the lowering of the centre of gravity, will hold for any type of vessel. The Vendenesse, a sea-yacht constructed at Saint-Denis, France, in 1892, built for Count Chabonne, is of 12 tons dis- placement, contains a little over one ton of aluminium, a sav- ing in weight over steel or wood of two tons. A prolonged stay in the harbor at Havre has proven that the sea water has practically no effect on the hull, and with 1 1 tons of lead in the keel there was no straining or weakening in a heavy sea. Immediately thereafter the French Minister of the Marine de- cided to have an aluminium torpedo boat constructed, to be carried by the warship La Foudre. This was built by Yarrow & Co., and had its trial trip in September, 1894. The vessel is 60 feet long, 9 feet three inches in depth. The aluminium was strengthened by being alloyed with 6 per cent, of copper, which increased its tensile strength to 35,000 pounds per square inch. All frames were made 25 per cent, larger than if they were steel, and therefore weighed exactly one-half as much. The weight of the hull alone was reduced from 4 tons to 2 tons. The extra cost of the material, compared with steel, was $5000, for the whole boat, in return for which there was a saving of 2 tons in dead weight and an increase of 3.5 knots in speed over vessels of the same class and dimensions made of steel. The maximum speed attained was 22.2 knots, and the average 20.5 knots. The total weight with steam up and coal in the bunkers is 10 tons, the horse-power of the engines 300. While this torpedo boat is the largest vessel so far constructed in aluminium, yet we may expect in the near future to hear of still larger ones, particularly pleasure steam-yachts, being con- -structed of it. At the same time we must not omit to mention 478 ALUMINIUM. the aluminium boats constructed by Rossiter & Co., of Balti- more, for the explorer Wellman, and which did such good ser- vice in the battle with ice and frost that he ha^ nothing but praise for them ; nor the aluminium rowing-shells built by Galanaugh, of Philadelphia, in one of which the local champions lowered their course record 8 seconds the first time they rowed in it. Hunting boats and small row-boats are being made at present in considerable numbers. The yacht "Defender," which defended the American Cup against the English yacht Valkyrie III, in 1895, has its hull of aluminium-bronze plates to the water hne, and aluminium plates alloyed with 3 per cent, of nickel above the water line. The upper frames and deck beams are also of the nickel alloy. The aluminium work is very properly protected by painting. This is undoubtedly the staunchest and fastest racing yacht ever built. Vehicles. — For apparatus which has to be moved around, al- uminium is rapidly coming into extensive use. Bicycles are being made very successfully, notably by a St. Louis firm, who harden the aluminium with copper and zinc, and cast it very solidly under pressure. Their frames have stood even more severe tests than steel ones, and yet have only one-half the weight. Aluminium racing sulkies are used for fast running, and two records, broken during 1894, were by horses carrying aluminium shoes and pulling aluminium sulkies. One of these is said to have weighed only 20 pounds entire. An aluminium cab is running in Paris, and a railway carriage of this metal will probably appear soon. In fact, many of the doors, sash- frames, handles, racks, etc., formerly made of iron or brass, have already been replaced by it. If the problem of aerial navigation is ever satisfactorily solved, we may expect to see aluminium largely employed in constructing the machines. Professor Langley, at Washington, and Maxim, in Great Britain, represent the utmost so far ac- complished in this direction, and they use sheet and wire-rope of aluminium. WORKING IN ALUMINIUM. 479 Decorations. — The sulphurous acid of the air or of the pro- ducts of combustion likewise leave aluminium untouched, while they quickly blacken silver. This caused its early use for re- flectors, for, while not taking at the start so high a polish as silver, yet it keeps its lustre indefinitely ; it has also the added superiority that its slight blue tint partly neutralizes the yellow color of artificial light, thus reflecting a very soft, white light. Even the unconsumed gas itself, containing sulphuretted hydro- gen, does not blacken the aluminium reflector in the least. It would follow that as a material for candelabra, chandeliers, or, in general, for any objects exposed to the air in dwellings, alu- minium keeps its color in a manner far superior to silver. This explains the superiority of aluminium leaf to silver leaf for almost any use, either for picture-frames or mural decorations indoors, or for outside decorations, especially in large cities where the air contains much sulphurous acid gas Since alu- minium leaf can be purchased in books at as low a price as silver leaf, it has entirely displaced the latter. Some of the latest uses in this line are extending very rap- idly, such as reflectors for locomotive headlights, in the ceilings of public halls, and shades for incandescent electric lights. For the first mentioned use it is vastly superior to the present nickel reflectors, and the Philadelphia firm manufacturing them can scarcely supply the demand. Much of the fancy grill-work used for decorating desks, shelves, stair-cases, elevator shafts and elevators themselves, is being made in aluminium. It is strong enough for all such purposes, and for the elevator car, which is lifted many thous- ands of feet in a day, the saving in weight is of great advan- tage. Mine-work. — For underground work, aluminium possesses great advantages over iron because of its non- rusting. Mine cars and Hfting-cages are made of it to great advantage, because every pound of dead weight saved on these allows so much more coal or ore to be lifted by a given power. Aluminium safety lamps are also a great improvement, not only from their 480 ALUMINIUM. lightness but because the high conductivity of aluminium gauze keeps the flame from passing through it so quickly as through brass gauze. Several collieries around Essen, Germany, are using these, as also aluminium lamps for the miners' hats. Medicine. — The harmlessness (innocuousness) of aluminium gives it exceptional advantages for use in surgery. M. Char- ri^re made, in 1857, a small aluminium tube for a patient on whom tracheotomy had been practiced. The tube was very light, and, therefore of little inconvenience to carry, and after wearing for some time the metal was very little attacked. After a long time a very thin, almost invisible coat of alumina formed, which was absolutely without harmful "efifect on the patient. Under the same circumstances a silver tube would have been blackened and corroded by the purulent matter. Aluminium has been used very advantageously for suture wire, and we can also deduce from this the great advantage there would be in making various surgical instruments of this material, not only from their not being corroded, but also because of the decrease in weight of the instrument case which the physician has to carry, often for long distances. We would also notice the com- fort to be derived from this large decrease of weight in any §ort of surgical appliances, braces, trusses, etc., which have to be worn and carried about continually on the person. Dental plates have been cast of aluminium, and, when com- plete, their weight is only a fraction of that of gold plates. But two difficulties are met in this application ; aluminium contracts very much in solidifying, and it is found almost impossible to cast it solidly on to the teeth ; also, pure aluminium is slightly corroded by the acids of the food and the saliva. To overcome these difficulties. Dr. Carroll (see also p. 446) adds a little copper, which he says decreases the contraction so much that the teeth remain solidly imbedded in the plate ; while the addi- tion of some platinum and gold renders it unalterable in the mouth. The aluminium plates possess the added advantage that on contact with metallic substances no disagreeable electric current is set up. It is a matter of common experience that if WORKING IN ALtlMINIUM. 481 a bit of iron, e. g., a carpet tack, is held in the mouth and touches a gold plate, a disagreeable bitter sensation is at once felt, due to electro-magnetic action. For this reason, some persons even refuse to wear the gold plates ; but it is stated by those who have worn aluminium plates that no such effect oc- curs with this metal. Further, broken teeth, etc., can be again attached by means of rubber cement, the sulphur of the rubber having no action on the aluminium. Dr. Fowler* obtained a patent for using aluminium in den- tistry in combination with vulcanite, which consisted in mixing granulated aluminium with a vulcanizable compound and then vulcanizing in the usual manner. The patent also claimed the inlaying of vulcanite articles with aluminium, the joining of articles made of vulcanite or rubber with clasps or rivets of alu- minium, and the use of aluminium tacks, nails, etc., in making rubber shoes. Scientific Instruments. — We have long been familiar with the appearance and advantages of the aluminium opera and field glasses, but the difiSculties met in working the metal, and more especially the monopoly of their manufacture by a few firms, have kept the price of these desirable instruments at unreason- able figures. Since there are but a few ounces of aluminium in the frames of these glasses, there is no reason at all why pur- chasers should have to pay double price for aluminium mount- ings over those of other metals ; and with the present wide de- velopment of the employment of aluminium I hope it will not be long before some enterprising American firm will make these instruments and sell them more nearly at their proper cost. Long before i860, Loiseau, of Paris, made for Captain Gordon a beautiful sextant, which only weighed one- third as much as those ordinarily made of brass. For an instrument which one is obliged to hold to the eye by one hand for several minutes, making observations from the rolling deck of a vessel, this property is of the greatest convenience, as any one will at- *U. S. Patent, 46230, Feb. 7, 1865. 31 482 ALUMINIUM. test who has had his wrist ache after making the noon observa- tion. Similarly, a difference of a pound in the weight of a tourist's glass may hardly seem much on lifting the glass, but we have trustworthy witnesses who say that it makes twenty pounds difference towards the end of a long walk. I suppose that sextants have not been more generally made of aluminium because of its high price ; this is now much less of an obstacle than formerly, and it is to be hoped that the instrument-makers will take up this subject again with fresh vigor. Engineering instruments, as transits, levels, etc., are made with aluminium frames, but it is certain that they have not come as yet into anything like common use. With cheaper aluminium it is to be hoped that the makers of these instruments will lighten the burdens of our surveyors by bringing about their general adoption. For any scientific instrument where the inertia of a heavy moving part is to be avoided, aluminium is the material par excellence. For electrical instruments it has the additional advantage that it is absolutely without magnetism or polarity, if pure, and it thus makes the most suitable material for com- pass boxes, galvanometer cases, etc. Aluminium is used for the beams of fine chemical balances as well as for the very small weights used with them. The aluminium weights for this purpose are in general use; they are quite rigid, unattacked by the air, and the smallest weights are of such size as to be quite manageable. The 50 milli- gramme weight can still be formed into a cylinder and termi- nated with a button, while the tenth of a milligramme is suffi- ciently large to be easily handled. The only other metal used for these small weights is platinum, and when the same weights in each metal are placed side by side the difference in size is very striking. Aluminium balances are now frequently seen. CoUot Bros., of Paris, made a balance which, with the excep- tion of the aqua-marine bearings, was composed entirely of alu- minium. Pure alunjinium, however, is hardly rigid enough for the beams, and'Sartorius, of Gottingen, was the first to WORKING IN ALUMINIUM. 483 Stiffen these by adding 4 per cent, of silver. With this im- provement an aluminium balance has no equal. They are now made by almost all the fine-scale-makers. Troemner, of Phila- delphia, places aluminium beams on all his assayers' button balances, while his analytical balance, entirely of aluminium except the bearings, is pronounced the chef d'oeuvre of the scale-makers' art. Dr. A. A. Blair, the noted analytical chemist, after using one for several years, states that for sen- sitiveness and quickness it is unsurpassed, while the gases of the laboratory have not had the slightest effect on it. The same rnaker constructs large bullion balances of the same material. Coinage* — Aluminium has been repeatedly proposed as a material for coins. As far back as 1856 Henri Montucci, a member of the French Academy, proposed this use to the Emperor. It then combined high price with lightness, and if it had always kept that high value it might have been substi- tuted for silver. But what a mistake it would have been ! A single invention, which reduced the price of aluminium one- half, would have depreciated the value of this currency to the same extent. The matter is different now, for two reasons ; first, the price of aluminium is so low that future reductions can only be by cents per pound ; second, as aluminium is so cheap it is out of question that it be used for money of final re- demption, but this same fact brings it into direct competition with nickel and bronze for minor coinage. Granted that aluminium can be suitably hardened by adding a few per cent, of some other metal, and there is not a single requirement for a metal for coinage which- such an alloy does not possess. For instance, the conditions to be filled are : 1. Capability of being cast, rolled, punched, stamped, and taking a fine impression. Aluminium does this as well as any metal known. 2. Durability. Aluminium is a very smooth metal, possess- ' * Further information than given here may be found in an article by the writer in the "Aluminium World," January, February and March, 1895. 484 ALUMINIUM. ing a sort of inherent, anti-friction quality, and even the pure metal, hardened by stamping, wears remarkably well. 3. Non-corrosion. Aluminium resists corrosion better than copper, bronze or any of the base metals. In addition to this is the fact that if it does corrode slightly, the salts formed are entirely harmless. No other metal compares with it in this regard. 4. Cheapness. Since small coins are only of nominal value, it becomes a matter of profit to the government to make the coin as cheap as it can. But aluminium ingot at $0.50 per pound is equivalent for coining purposes to nickel alloy at $0.14 and bronze at the same figure. But these really cost $0.20 and $0.10 respectively, so that aluminium would cost slightly more -than one and less than the other. It is therefore clearly suitable in this respect. 5. Large supply. If all the nickel and copper coins in the United States were replaced by aluminium, the annual amount required would be about one hundred tons. This is only ten per cent, of the total amount which will be produced this year. When nickel was adopted for coinage the supply of it was rela- tively much less abundant. 6. Difficult to counterfeit. Of all ordinary metals, aluminium would be the hardest to counterfeit. Further, the inducement to try to counterfeit minor coin is much less than with larger money, and this condition is not of as great relative importaftce. 7. Lightness. The people of the United States are carrying around probably 3,000 tons of minor coins. If this could be made 2,000 tons less, who would not favor an immediate change ? Granted, therefore, that aluminium can be suitably hardened, there is not a single requirement in which it is not equal to the metals now in use for minor coin, and in two ways it is far su- perior to them, viz., innocuousness, cleanliness and lightness. It is to be hoped that the United States government will rec- ognize the advantages of such a change and lead the world in making its minor coinage of aluminium. Chemical Apparatus. — Dr. George Bornemann has critically WORKING IN ALUMINIUM. 485 tested some aluminium utensils made by Max Kaehler and Martini of Berlin, and reports as follows:* An aluminium hot-air oven is heated quicker and to a higher temperature than a copper one; the distribution of temperature is more even ; no chemical alteration after daily use for ten months. Water baths evaporate water very quickly, and one tested suf- fered no loss in weight or disfiguration in three weeks' use. Rings and pincers stay bright; lacquering is unnecessary. Sand baths remain unaltered in weight, but care must be taken not to overheat them. Stove-pipe, tripods and hot funnels are very desirable. Crucibles are not to be recommended, as they cannot be used above incipient redness. Several chemical companies are using aluminium stills, evap- orating dishes, etc., particularly in the manufacture of medi- cinal extracts, etc., with great satisfaction. Culinary Utensils. — No less than six large firms are at pres- ent making aluminium cooking utensils in the United States. The pioneer was the Illinois Pure Aluminium Company, at La- mont, Illinois, whose factory was put in operation early in 1893. For about a year, the success of the venture was uncertain, but everyone who used the utensils recommended them so highly ithat the trade then began to grow, and at present the supply is not equal to the demand. America has certainly taken the lead in this application of aluminium, which, it is the writer's firm opinion, will overshadow in magnitude all other applica- tions of the metal. The well-established advantages of these utensils are : 1. Non-poisonous. This cannot be said of any other uten- sils except the expensive and fragile enamel-lined vessels. 2. Easily cleaned. It is very seldom that anything burns fast or sticks to an aluminium utensil. If such does happen, a soaking in water removes it entirely. 3. Not corroded. None of the acids found in foods have any perceptible corrosive action on aluminium. Daily use for *Chemiket Zeitung, January 11, 1893, p. 34. 486 ALUMINIUM. three years, in every way, has left no signs of corrosion on a utensil in use at the writer's home. In weight, the utensil has lost one-quarter of an ounce, which would point to about a hundred years as the probable time it will take to wear out. 4. Do not scorch. It is a singular fact, that it is almost im- possible to scorch even the most delicate foods in an aluminium vessel. This is a well-attested fact, and is due to the great heat conductivity of aluminium preventing a high local temperature at any one spot. On this account aluminium is not well- suited for frying-pans or skillets, in which the object is to brown the food, that is, to superficially scorch it in a measure. 5. Cook quickly. Kettles and sauce-pans have their contents heated very quickly, because of the great facility with which the metal conducts heat. 6. Lightness. Only one-third that of other utensils. 7. Durability. Do not corrode, and show very little wear outside; besides, there is nothing to crack off, as in enamel wear, no coating to wear through, as in tinned wear, and it will not crack like cast-iron ware. The utensils, if properly treated, are almost indestructable and will wear almost indefinitely. I have no hesitation in predicting that when the general pub- lic have proven by actual experience the merits of these uten- sils, they will displace all other kinds in the kitchens of all ex- cept the poorest classes. Already, they are being largely used in hotels, restaurants, railway cars, steamships, large institutions, and by makers of preserved food and confectionery. Several makers of pickles, condiments and soups have adopted them. For such use on a large scale, the kettles are made with a double bottom and are heated by steam. Table Ware. — The writer does not recommend aluminium for use on the table for such articles as are subject to consider- able wear. Spoons, knives, forks and plates, especially, very quickly lose their high polish, and become dull. However, for articles which do not meet heavy wear, its use is advantageous. Especially is this the case with soup-tureens, vegetable and meat covers and dishes, in which the property of aluminium of WORKING IN ALUMINIUM. 487 keeping hot a long time is of the greatest advantage. Alu- minium chafing-dishes are also highly recommended. For sugar bowls, cream and water pitchers and trays, aluminium does very well, its particular advantage over silver-plate in these cases being that it does not blacken. Every housekeeper knows what an amount of cleaning and polishing this saves. Whole services of plate have been made in aluminium. Constructions. — For purposes of construction, aluminium cannot replace steel, except where expense is a secondary con- sideration, and lightness or resistance to oxidation are the first conditions to be filled. If in a machine a certain moving part must be as light as possible, that piece may be made of alumin- ium, while the rest is still of iron or steel. In torpedo boats, railway carriages, cabs, wheel-barrows, or- any apparatus which is moved around continually, lightness is a prime consideration, and the substitution of aluminium for steel is simply a question as to whether the lightness gained compensates for the in- creased cost. For a stationary structure, the question is sim- ply one of the minimum cost for a given strength, and in such fields steel is king, and will stay at the head until aluminium can compete with it in price, bulk for bulk, which is a very re- mote contingency. It was said that a 16-story buildiflg in Chicago was to be built of iron frames with plates of aluminium fastened on for a facing. These plates were to be 36 inches by 20 inches, and three-sixteenths of an inch thick, composed of an alloy of 90 per cent, aluminium and 10 per cent, of copper. The informa- tion, however, was partially misleading ; the alloy used was alu- minium bronze, 90 per cent, copper and 10 per cent alumin- ium. Batteries. — Since aluminium is so inert in presence of nitric acid, it forms a good substitute for platinum in the Grove bat- tery. Hulot used a couple composed of an aluminium plate and a zinc plate amalgamated for some time previous to use. The exciting fluid may be either dilute nitric or sulphuric acid. With water, charged with one twentieth part of sulphuric acid 488 ALUMINIUM. at 66°, the cell gave for some hours a current at least equal to that afforded by platinum in the same conditions. After six hours its original force was diminished one-fifth, and at the end of 24 hours the cell was not entirely polarized, but still gave one-fourth its original current. To restore the electro-negative character of the aluminium it was only necessary to immerse it an instant in nitric acid and wash well. Col. Frishmuth, of Philadelphia, used aluminium-zinc batteries for several years in electrolytic experiments as well as for ordinary house use, and has stated that it answered as well as platinum, and in some cases gave greater power. From experiments made by the writer (p. 91), it appears that the purer aluminium is, the more it resists nitric acid. It is therefore recommended to make battery plates out of the purest obtainable aluminium, and on no account to use an alloy. Lithographic Plates. — Aluminium is being successfully used to replace the expensive Solenhofen lithographic stone. One inventor gives the directions for using it as follows :* "The plates are cleaned, levelled and polished, and then prepared for printing in one of two ways. One way is to apply "transfers" in chalk or ink to the plates, on which " facings " are then pro- duced by the action of suitable acids. Or, the plates may be first treated with the acids until their surfaces have an opaque white appearance, then, after rinsing with a solution of alum or of acetic acid to enable the plates to take them, "transfers" are applied and the plates then subjected to a second treatment with acid, this time more concentrated than before. Acids suitable for this purpose are ortho-, meta- or pyro-phosphoric, or hydrofluoric. These acids form salts of aluminium which are insoluble in water, and which, while attached to the plates; retain enough water to prevent the adherence to the parts acted on of the oily inks employed for coloring the other parts of the plates. An acid mixture such as is used in the process is com- * English Patent 16,312; Sept. 12, 1892. O. C. Strecker. Mainz, Germany. WORKING IN ALUMINIUM. 489 posed, for example, of 10 parts of a. solution of gum, 3 of a saturated solution of gallic acid, and i of a 20 per cent, solu- tion of ortho-phosphoric acid. Krebs, of Frankfort, recommends sponging the polished sur- face with a dilute solution of caustic soda, and in order that the surface shall take the ink it is covered with a varnish com- posed of zinc white, potash and saltpetre moistened with alcohol. The Ellery-Howard Co. of New York are using aluminium plates for printing, and report them entirely satisfactory. Flash-light Powder. — Very fine aluminium filings, or alumin- ium powder made by grinding up the leaf, makes an excellent flash-light for photographic purposes. Its advantages over magnesium are that it is cheaper, not so liable to explode in preparation, and produces none of the white fumes so disa- greeable when using magnesium. Villon, the first to use it, recommends the three following mixtures:* I. II. III. Aluminium powder 8 10 10 Chlorate of potash 20 25 25 Sugar 2 — 2 Nitrate of potash — S — Potassium f erro-cyanide — — 3 Sulphide of antimony — 4 — These powders may be ignited in various ways, but the best and safest is to project them into the flame. The following mixture also gives a very intense light : Aluminium powder 20 parjs, Lycopodium 5 Nitrate of ammonia - i " Villon recommends using a lamp fed in its centre with a jet of oxygen. Mr. Alexander Black, of New York, recommends the follow- ing mixture for very rapid flashes : * Reveu de Chimie Industrielle, 1892. 490 ALUMINIUM. Aluminium powder 5 parts. Chlorate of potash 15 " Sulphide of antimony 3 " The London Lancet recommends for medical photography, laryngoscopic, auroscopic and other demonstrations, the burn- ing of a thin aluminium ribbon in an ordinary spirit-lamp or blow-pipe flame. Miscellaneous. — We can do no more than mention the vari- ous other uses to which aluminium has been put. Cash registers and conveyers. Watch and key chain. Dog chains. Horse-shoes, bits, bridles, stirrups, harness trappings. Insoles for shoes, to keep out dampness. Shoe horns. Surgical instruments, suture wire, tracheotomy tubes. Braces, trusses, supports for various parts of the body. Fine wire woven into passementerie, uniforms and flags. Metallic parts of trunks and traveling bags. Keys — hardened by drop-forging cold. Watches, compasses, knife-handles. Cases for cigars, cigarettes, matches, spectacles. Teething plates for infants. Artificial limbs and noses. Pen and pencil holders. Slate pencils. Paper cutters. Thimbles. Pocket rules, scales, levels. Toilet articles, backs of brushes, combs, etc. Walking sticks, umbrella frames, billiard cues. Picture frames, mirror frames, placques for hand-painting. Pufif boxes, collar and cufif boxes, perfume bottles. Hat pins, hair-pins, bracelets, brooches, rings, etc. Candlesticks, fancy baskets, card receivers, ink-stands. Cigar-holders and pipes, with amber mouthpieces. Moulds for forming cigars. Patterns and models for metal castings. Eye-glass frames and chains. Name-tags on flying pigeons. WORKING IN ALUMINIUM. 49 1 Boot-trees and lasts in shoe factories. Connections in rubber hose, clasps on rubber garments. Blades for ventilating fans, especially those run by electric motors. Business and visiting cards. Body of ice and roller skates. Photographic cameras, tripods, " kodaks." Padlocks, especially for portable use. Car roofs, railway semaphore signals. Shelves on which to evaporate fruit. Musical instruments, cornets, trombones, horns, drum frames. CHAPTER XIV. ALLOYS OF ALUMINIUM. Aluminium unites easily with most of the metals, the com- bination being usually accompanied by a disengagement of heat, which is particularly active in the case of copper. (I do not know that any attempt has been made to measure this heat quantity except in the case of iron). This circumstance is taken to be an indication that these alloys are chemical combinations of the metals rather than mere mechanical mix- tures. Lead and antimony appear to be the only metals not alloying with it easily. The practical production of these alloys from the metals is in general a very easy operation. The alu- minium may be melted in a carbon or magnesia-lined cru- cible, without a flux, and the other metal simply thrown in; it falls to the bottom, melts, and is absorbed by the aluminium. In some few cases the alloying metal must be mixed in pow- der with finely-divided aluminium and heated together in a closed crucible, but this is only exceptionally the case. Again, a bar of aluminium may be taken in the tongs and held under the surface of another metal already melted. This is the best method of introducing small percentages of aluminium into other metals, unless we may except the adding of a small quan- tity of rich alloy to pure metal, thus diluting the percentage of aluminium to the desired quantity. Most of the alloys thus produced are improved by careful remelting, the aluminium seeming to become more intimately combined. The alloy made in the first operation is often not entirely homogeneous, but be- comes more uniform, and finally perfectly so, by repeated fusions. Very few of the alloys will Hquate; in general the alloy acts as a single metal. However, in some cases where (492) ALLOYS OF ALUMINIUM. 493 the alloy is not of a very definite or certain composition, a li- quation may take place, leaving as a residue an alloy with dif- ferent proportions from the fluid metal running off. In the case of volatile metals, they can usually be driven out of the aluminium by keeping the alloy melted and exposed to a heat sufficient to drive off the volatile metal. The useful alloys of aluminium seem to fall naturally into two groups: i. Aluminium containing not over 10 to 25 per per cent, of other metals; 2. Other metals containing not over 10 to 15 per cent, of aluminium. In almost every case, alloys between these limits possess no useful properties, and are mere chemical curiosities. I . Aluminium is too soft to stand much wear, or to keep a high polish, and too weak to support much stress. In order, then, to make it harder, stronger and better wearing, and at the same time to keep its valuable lightness and beautiful color, it is alloyed with a small percentage of some suitable metal. Silver, nickel, copper or tin is frequently used for this purpose, as well as some other metals, as will be explained at length in the succeeding consideration of the alloys. It might here be remarked that the color of aluminium is not radically altered, except by very large proportions of the foreign metal, by reason doubtless of our proportions being expressed by weights, while the influence of a metal in changing the color of another depends more on its volume. For instance, an alloy of 50 per cent, aluminium and 50 per cent, copper has the color of alu- minium, an alloy with 70 per cent, of copper still has the white color of aluminium, but with 85-95 P^r cent, of copper the alloy is yellow. It has experimentally been observed that the color appears to change from white to yellow at about 82 per cent, of copper. If we combine equal volumes of copper and aluminium, our alloy would contain about 77.5 per cent, of copper. If then, we acknowledge the principle that the metals affect each other's color according to the proportions by volume in which they combine, we see the explanation of both facts — the very small influence of foreign metals in changing the color 494 ALUMINIUM. of aluminium, and the great influence aluminium has in whiten- ing or changing the color of other metals. Again, precisely the same principle holds when we consider the specific gravity of these alloys, except that in this case our fundamental pro- position — that the metals afifect each other's specific gravity according to the proportions by volume in which they com- bine — is capable of mathematical demonstration. But we have also to consider in the case of the specific gravity a most curious phenomenon, which is, that aluminium seems to be able to absorb several per cent, of certain metals without in- creasing in volume, and, in some cases, it even decreases in volume. The basis for this statement is easily recognized. For instance, some aluminium was cast in a mould which gave a piece of a certain size weighing 480 grains. The aluminium was melted and 5 per cent, of silver added to it ; a piece was then cast in the same mould. Now, if the aluminium had ab- sorbed the silver without increasing in volume, the second test piece should have weighed 504 grains ; it weighed 502 grains, showing only the merpst dilatation of the aluminium in absorb- ing 5 per cent, of silver. So, if we calculate from the analyses of commercial aluminium given in Chapter III., the specific gravity of the alloy (for we can so consider it), on the suppo- sition that all the foreign elements are absorbed by the alumin- ium without change of volume, it will be found that in almost every case this calculated specific gravity is very close to or even below the observed gravity, showing in the latter event that even a condensation beyond the volume of the aluminium had taken place. This condensation seems to offer a natural explanation of the hardening and strengthening effect produced by the addition of a small quantity of the metals named. 2. At the other extreme of the scale of alloys we have those containing a few per cent, of aluminium. In general, the effect of a small quantity seems to be principally a notable increase in strength and a striking change in color of the highly colored metals. A very small quantity has little effect in reducing the specific gravity, but as the quantity increases, the effect is what ALLOYS OF ALUMINIUM. 495 we would infer from the previous remarks on specific gravity. The reason of this is that the condensation in alloying taking place with these alloys is so great that the metal absorbs the aluminium without any noticeable increase of volume, and its specific gravity may be even increased slightly at first. This great condensation offers a partial explanation of the strength- ening of the original metal, since its texture is finer and its hardness increased. After a certain small limit in the percent- age of aluminium is passed, the beneficial effects alluded to are overpowered by the influence of crystalline chemical combina- tions between the alloying metals, and the alloy quickly loses strength and malleability. With the exception of copper and tin, 5 per cent of aluminium is the limit of the useful alloys at this end of the scale. The alloys of aluminium with copper and iron have become so important that it seems proper to devote separate chapters to their consideration ; the remainder of this one will therefore treat of the alloys with metals other than copper and iron. I wish to remark, that as the tertiary alloys cannot be rigorously classified, we will have to place them under the alloys of that metal which, besides aluminium, seems to be their character- istic ingredient. Some of the combinations of aluminium with metalloidal elements, which might possibly be looked for in this chapter, are described in Chapter V. among the compounds of aluminium. Aluminium and Antimony. Tissier Bros, state that they were unable to get a homogene- ous alloy of these two metals. Dr. C. R. A. Wright * concluded that there is no commercially valuable alloy of these two metals. He found that when alu- minium is melted in a crucible and lumps of antimony dropped in, they fall to the bottom and melt quickly. The two metals remain separate until stirred, when part of them unite to an alloy which immediately solidifies because of its high melting ♦Journal of the Soc. of Chemical Industry, June, 18912. 496 ALUMINIUM. point, while the remainder stays as a fusible alloy of much lower melting point. This solidified alloy has the composition AlSb (81.6 per cent, of antimony), is a gray mass with an iri- descent lustre, and does not melt below 1000° C, which is most remarkable, considering that the melting points of its in- gredients are 625° and 425° respectively. The alloys low in aluminium look like antimony, those low in antimony are some- what spongy, and they all slowly disintegrate in the air and disengage hydrogen in water. Roche * arrives at somewhat different results. He confirms the existence of the alloy AlSb, with its abnormally high melt- ing point, but he claims that aluminium containing less than 5 per cent, of antimony *is malleable, and superior in hardness, tenacity and elasticity to pure aluminium. Above this, the hardness and tenacity diminish, until at 10 per cent, antimony the alloy crystallizes in brilliant laminae. The melting point and ease with which moist air attacks the alloy increase up to 81.6 per cent, of antimony (AlSb), which in moist air or water crumbles to a black powder. Roche recommends these alloys as forming, when melted with other metals, as copper or nickel, alloys of great hardness, strength and elasticity^ t Hoeveler states that he has tried to get Roche's alloys, but with negative results. In no way could he get homogeneous alloys with 6 or 12 per cent, of antimony; even a little antimony makes the aluminium weak and brittle. The only useful alloy claimed by Roche is the one with less than 5 per cent, of antimony. This, it is true, can be made apparently quite homogeneous, casts and rolls perfectly, and is apparently superior in many ways to pure aluminium, as re- marked by Roche. But, after a few months' standing, it will be found that the alloy has disintegrated to such an extent as to be worthless, a point which has probably been discovered by this time. * Moniteur Scientifique, 1893, p. 269. tChemiker Zeitung, July 12, 1893. alloys of aluminium. 497 Aluminium and Arsenic. Wohler* stated that when these two metals were mixed inti- mately and heated together they combine with a flame, forming a dark-gray metallic powder which smells a little of arsenu- retted hydrogen. It slowly evolves that gas in cold water, rapidly in hot. H. N. Warrenf melted aluminium and dropped arsenic upon it. He states that an alloy is thus formed, which is decom- posed on raising the temperature; but if the aluminium is used alloyed with another metal, a regulus results. Aluminium and Bismuth. These two metals combine easily, the alloys being very fus- ible, unchanged in the air at ordinary temperatures, but oxid- izing rapidly when melted. As small a quantity of bismuth as O.i per cent, in aluminium makes it so brittle that it will crack under the hammer in spite of repeated annealings. Tissier Bros, tried 0.5, 2.5, 3 and 5 per cent, of bismuth, but with simi- lar results; with 10 per cent, of bismuth, however, the alloy was not so brittle and could be worked under the hammer to a cer- tain extent, but could not be rolled or drawn. It takes a fine polish and is not attacked by nitric acid or blackened by sul- phuretted hydrogen. The same chemists found that on melt- ing I part aluminium with 2 parts of bismuth they obtained in the crucible an alloy of the two metals floating on top of pure bismuth. The alloy contained approximately 75 per cent, of aluminium, showing that aluminium does not appear to be able to take up over 25 per cent, of bismuth. This alloy was not so brittle as pure bismuth, and was so distinct from it in the cru- cible that the two layers could be separated by a blow of the hammer. Aluminium and Boron. Deville obtained an alloy rich in boron by melting aluminium * Pogg. Ann., 1827, ii. 160. t Chemical News, Aug. i, 1890. 32 498 ALUMINIUM. with borax, boracic acid or fluo-borate of potassium. The alloy is very white, only able to bear slight bending and splits in the rolls. It exhales a strong odor of hydrogen silicide, due to its having absorbed silicon from the vessel in which it was prepared. Metallic boron may be easily extracted from the alloy as both graphitic and diamantine boron. (See also Chapter V.) H. N. Warren introduced aluminium into a molten mixture of fluor-spar and vitrified boric anhydride which had been heated in an oxy-hydrogen furnace until fumes of boron flu- oride appeared. The aluminium immediately set free boron, which dissolved in the aluminium in excess, rendering it crys- talline and brittle. The boron thus dissolved is in the graph- itoidal state. Aluminium and Cadmium. Cadmium unites easily with aluminium, producing alloys which are malleable and easily fusible, and which have been used for soldering aluminium, but only answered that purpose imperfectly. I have not found in any aluminium solder I have tried any advantage gained by replacing zinc by cadmium. C. R. A. Wright melted together equal parts of aluminium and cadmium, and states that on keeping the mixture some time about iOO° C. above the melting point of cadmium it sepa- rated into two distinct layers, the upper part of which con- tained 3.39 per cent, of cadmium, while the lower part con- tained only 0.22 per cent, of aluminium. The addition of tin prevented the separation and formed a strong ternary alloy. Aluminium and Calcium. Wohler states that an alloy of these metals was obtained by fusing together equal parts of aluminium and sodium with a large excess of calcium chloride. The alloy produced had a lead color, easy cleavage, specific gravity 2.57, and was unal- terable in air or water. Analysis showed it to be evidently a mixture, as it eontained — ALLOYS OF ALUMINIUM. 499 Aluminium 88.0 per cent. Calcium g g << Iron 2.0 " Prof. Mabery describes a peculiar product formed in the elec- tric furnace, consisting principally of aluminium, copper, and up to 3 per cent, of calcium (p. 343). Aluminium and Chromium. Wohler* heated violet chromium chloride with aluminium wire, obtaining an alloy of the two metals, while aluminium chloride volatilized. When i part of aluminium was used to 2 of the salt, a gray, crystalline mass resulted, from which excess of aluminium was removed by caustic soda, leaving lustrous, tin-white crystals. When these were heated in the air they be- came steel-gray, but did not oxidize further. They were unat- tacked by caustic soda or concentrated nitric acid, but dissolved in hydrochloric acid, with separation of a little silica. Concen- trated sulphuric acid oxidized them to a green mass. They were fusible only at a very high temperature. On analysis, this alloy was found to contain both iron and silicon, coming from the aluminium used. Taking these out, the composition, as regards aluminium and chromium, was — CalculateJ'for AlCr. Aluminium 31.6 33.92 Chromium 68.4 66.08 loo.o 100.00 Professor J. W. Langley has alloyed chromium with alumin- ium by dissolving chromium oxide in a bath composed of fused fluorides of aluminium, sodium and calcium, then stirring in metallic aluminium. The latter reduces the chromium oxide, passing into the bath as alumina, while the chromium alloys with the excess of aluminium. It is found that 2 or 3 per cent. of chromium makes the aluminium harder, denser and stronger but decreases the malleability. Over 5 per cent, makes an alloy which is almost unworkable. " Ann. der Chemie und Pharmacie, 106, 118. 500 ALUMINIUM. Lejeal produced by Wohler's method an alloy with 1 1 per cent, of chromium. It was very brittle, crystalline and impos- sible to work. It was necessary to dilute to below 3.5 per cent, before the alloy could be hammered or rolled, and this metal was criqu^ (crickly) after rolling hard. With this per- centage, the fracture is crystalline, seggregated in the centre, and gives a tensile strength, annealed, of 12.5 kilos per square millimetre (18,000 lbs. per sqr. inch) with an elongation of 7 to 12 per cent. Aluminium and Cobalt. The following alloys have been mentioned, but I know nothing of their properties : — Cobalt. Aluminium, Copper. Iron. Sun bronze 40 to 60 10 30 to 40 — Metalline 35 25 30 10 Lejeal made an alloy with 6 per cent, of cobalt. It was rolled easily from 8 m. m. thickness down to 2 m. m. without annealing, and gave a fracture which was dark and pretty uni- form. An alloy with 3 per cent, of cobalt gave : — Tensile Strength. Elongation. 2 2 Kilos per m, m. Lbs. per in. Per Cent. Worked hard 22.0 31,000 4 Annealed 16.5 26,000 20 Aluminium and Copper. (See Chapter XV.) Aluminium and Gallium. Lecoq de Boisbaudran has stated that alloys can be formed by melting these metals together at dull redness. The alloys thus obtained remain brilliant, and do not sensibly absorb the oxygen of the air in their preparation. After cooling they are solid but brittle, even when the excess of aluminium has raised the melting point to incipient redness. They decompose water ALLOYS OF ALUMINIUM. SOI in the cold, but better at 40° C, with rise of temperature, evolu- tion of hydrogen, and formation of a chocolate-brown powder, which is ultimately resolved into white flakes of alumina. Aluminium and Gold. Tissier Bros, state that aluminium can contain as much as 10 per cent, of gold without its malleability or ductility being im- paired. The alloy with 10 per cent, of gold can be forged at a red heat as well as aluminium, is a little harder than aluminium but polishes scarcely any better. ^ The color of the alloy is a peculiar brownish tint. The alloy with 1 5 per cent, of gold can no longer be forged. , The addition of a small amount of aluminium to gold quickly takes away all its malleability. Ten per cent, of aluminium makes a white, crystalline, brittle alloy ; five per cent, is said to be extremely brittle, as much so as glass ; one per cent, gives an alloy similar to the gold-silver alloy called by the jewelers " green gold." It is very hard but still malleable. Professor W. Chandler Roberts-Austin, in a lecture on the influence of other metals on gold, stated that while a sample of pure gold had a tensile strength of 7 tons per square inch with 25 per cent, elongation, the addition of 0.186 per cent, of aluminium increased its strength to 8.87 tons (26 per cent.), its elongation remaining practically the same — 25.5 per cent.* " Niirnberg gold " is an alloy used to make cheap imitation- gold ware, resembling gold in color and not tarnishing in the air. Its composition is said to be Copper 90 per cent. Gold zM " Aluminium iVi. G. F. Andrews f has made a large number of experiments with reference to using aluminium in jewelry, and states that ♦Journal of the Society of Arts, vol. 36, p. 11 25. t Journal American Chemical Society, July, 1894, p. 485, 502 ALUMINIUM. the alloys with gold are of little practical use except for decora- tive purposes. His results are as follows : Per cent, of Gold. 6 As white as aluminium but much more brittle. 10 Harder than aluminium, does not work well except at a high temperature. Color light violet brown. 1 5 Slightly violet, although nearly white. A very soft, 6ne-grained metal. 50 Beautiful violet color; very soft and spongy. 78 Color peculiar, between pink and violet; very brittle. 90 Pale violet. 94 Violet approaching pink again. Alloys with very little aluminium leave a bright violet color on the cupel, under the blowpipe. An alloy of 50 parts gold, 45 copper and 5 aluminium takes the color and polish of fourteen carat gold, but easily tarnishes. Roberts-Austen has found with a Le Chatelier pyrometer that the alloy AuAlj, containing 22 per cent, of aluminium, melts at 1065° C. to 1070° C, or 25° to 30° above gold itself. Small amounts of aluminium, however, lower the melting point, 0.47 per cent., giving the alloy Aui,,,, Al, almost effacing the melting point of the gold, making it pasty, the mass only be- coming really solid at 900° C. Up to i per cent, of aluminiym the melting point is lowered, over this it begins to rise. Roberts-Austen also made a curious experiment, showing the great heat of combination of gold and aluminium. Thirty grammes of gold was melted in a crucible, and kept at 1155° C. A piece of cold aluminium weighing 0.3 gramme was put in and rapidly stirred. At first the temperature fell to 1045°, then rose briskly to 1380°, which was 225° above the initial temperature of the gold. It is possible to calulate roughly the heat set free in this ex- periment. Assuming the specific heat of gold in the molten state to be 0.036, and of liquid aluminium 0.308, we have — " ALLOYS IN ALUMINIUM. 503 Heat absorbed by the gold 30 X 225 X 0.036 = 243 gramme calories. Heat absorbed by the liquid aluminium 0-3 X (1380—625) X 0.308 = 70 " " Heat to liquefy the aluminium 0.3 X 258 = 77 Total 390 " " This is equal to 1300 kilogramme calories per kilo of alumin- ium, a quantity equal to nearly 20 per cent, of the heat of oxi- dation of the aluminium, and suggests the query whether the evolution of heat may not have been largely due to the oxida- tion of the aluminium by oxygen dissolved in the molten gold. A careful analysis of the alloy after the experiment would have thrown light on this question. Aluminium and Iron. (See Chapter XVI.) Aluminium and Lead. 'Deville remarked that these two metals had so little tendency to combine that there may be recovered intact at the bottom of an ingot of aluminium any small pieces of lead which may accidentally have dropped into the metal. Later, however, Deville remarked that M. Peligot was able to cupel buttons of impure aluminium with lead, thereby purifying the metal, and thought that an alloy may exist in certain proportions at the temperature necessary fdr cupellation. It is well known that if aluminium and lead are melted down together and cooled they separate, the aluminium chilling first and floating on the fluid lead. Mierzinski remarks that this property would render it possible to use aluminium for de-silverizing bulhon, if its price allowed. I do not think that the separation is quite as absolute as is indicated above. On melting the two metals together, they separated, with a sharp line of demarkation, so that there ap- peared to be no combination ; but the lead was hardly as blue S04 ALUMINIUM. as at first, and contained about ^ per cent, of aluminium, while the aluminium had visibly deteriorated, was darker, more crys- talline, heavier, and contained at least 5 per cent, of lead, a test for which could easily be had before the blowpipe on char- coal. A small percentage of lead appears to be very harmful to aluminium. Lejeal melted together lead and aluminium and allowed them to cool slowly. There was almost complete separation of the two metals, and analysis showed — Upper part of ingot. Lower part of ingot. Lead 9.78 per cent. 94.49 per cent. Aluminium 90.22 " 5.51 " If antimony is present, however, the lead can take up more aluminium. I. H. Johannes,* of Washington, has patented an alloy com- posed of 15 parts of aluminium to 85 parts of lead and anti- mony combined, but for what purpose he finds it suitable is not stated, it is probably for type metal. C. B. Millerf patents an anti-friction alloy of lead 320 parts; antimony, 64; tin, 24; aluminium, 2. T. MacKellarl patents a type metal consisting of lead 65 parts; antimony, 20; tin, 3.3; copper, 3.3; aluminium, 3.3. Heycock and Neville state that a small quantity of alumin- ium does not cause a fall in the melting point of lead, which would show that no alloy is formed. Aluminium and Magnesium. Wohler § fused these two metals together in the proportions represented by ALMg, forming an alloy with 69.2 per cent, of aluminium. The product was a tin-white mass, very brittle, igniting at a red heat and burning with a white flame similar to *U. S. Patent 443,943; Dec. 30, 1890. tU. S. Patent, 456,898; July 28, 1891. JU. S. Patent, 463,427: Nov. II, 189 1. § Ann. der Chemie und Pharm. 138, p. 253. ALLOYS OF ALUMINIUM. 505 magnesium alone. The alloy in the proportions MgaAl, con- taining 36 per cent, of aluminium was malleable, but completely destroyed by leaving in water for a day, without any evolution of hydrogen. Both these mixtures appear to contain a com- pound of definite composition, for when treated with a solution of sal-ammoniac they disengaged hydrogen abundantly and de- posited a brilliant, tin-white metallic powder. The solution contained magnesium chloride, while the residue was rich in aluminium and appeared to produce some aluminate of magne- sium, which clouded the solution. The metallic residue was washed with water, again treated with sal-ammoniac solution and then with solution of caustic soda until it no longer evolved hydrogen. This residue was about one-third the total alloy, and was insoluble in both the above reagents. It burned with brilliant sparks when thrown into a flame. Aluminium and Manganese. Michel* (a pupil of Wohler) obtained an alloy of these metals by melting together — Anhydrous manganous chloride 2 parts Potassium and sodium chlorides 6 " Aluminium 3 " On treating the regulus with hydrochloric acid the excess of aluminium was removed, leaving a dark-gray crystalline pow- der. This was unattacked by concentrated sulphuric acid in the cold, but dissolved on warming. Dilute caustic soda dis- solved out the aluminium, leaving a residue of manganese. Its specific gravity was 3.4, and analysis showed it to correspond to the formula MnAL, containing 60 per cent, of aluminium. Mr. A. H. Cowles manufactured an alloy for electrical pur poses, consisting of manganese 18 parts, aluminium 1.2, siHcon 5, zinc 13, copper 67.5. It was said to have a tensile strength of 35,000 pounds, with 20 per cent, elongation, and as its elec- * Ann. 'der Cham, und Pharm, 115, 102. 506 ALUMINIUM. trical resistance was greater than German-silver, it was especi- ally recommended for rheostats. The same inventor also patented the addition of manganese to commercial aluminium up to five per cent, for hardening and strengthening purposes. Aluminium and Mercury. It is not easy to understand why Deville said in his treatise, " Mercury is not able to unite with aluminium. Experiments of this nature which I have made myself, and which Mr. Wal- laston has confirmed, proved it most clearly." Several years ago, before reading anything about the failure of mercury to unite with aluminium, I remember on taking a clean, bright piece of aluminium foil, putting on it a small globule of mur- cury and rubbing in hard with the finger, I felt the foil become hot and a white powder appeared immediately. On rubbing still more a hole was eaten through the foil. I concluded at once that the mercury amalgamated the aluniinium and that the latter when distributed through the amalgam was in such a fine state of division that the air readily oxidized it, forming the white powder. In looking up the literature on the subject the following information has been collected: — Cailletet* stated that aluminium could be amalgamated by the action of ammonium or sodium amalgam in the presence of water ; also when the aluminium is connected with the negative pole of a voltaic battery and dipped into mercury overlaid with acidulated water, or into a solution of mercuric nitrate. Tissier confirmed the latter method, adding that if the aluminium foil used is not very thick it becomes amalgamated throughout and very brittle. Tissier also found that aluminium may be made to unite with mercury merely by the intervention of a solution of caustic potash or soda, without the intervention of a battery. If the surface of the metal be well cleaned, or moistened with the alkaline solution, it is immediately melted by the mercury, and a shining amalgam forms on its surface. * Comptes Rendus, 49, 56. ALLOYS OF ALUMINIUM. 507 Joule* States that if a solution of an aluminium salt is elec- trolyzed, using mercury as the negative pole, it will form an amalgam with the aluminium set free. Since the amalgam de- composes water, setting free hydrogen, it is probable that all the aluminium deposited would be promptly oxidized. Gmelinf states that potassium amalgam introduced into a hole bored into a crystal of alum immediately acquires a rotary motion, which lasts sometimes half an hour. At the same time, it takes up a considerable quantity of aluminium and becomes more viscid. It is first stated in Watts' Dictionary (vol. viii.), that "alu- minium oxidizes when its surface is simply rubbed with a piece of soft leather impregnated with mercury; the rubbed surface becomes warm in a few seconds, whitish excrescences appear consisting of pure alumina." In Watts' Supplement I., the best method of preparing the amalgam for use is stated to be by heating the two metals together in a gas which does not act on either of them. The operation is performed by placing a piece of aluminium foil at the bottom of a thick-walled test-tube, and pouring well-dried mercury on it, the tube haying been previously drawn out at the middle to prevent the foil rising to the surface. The air is then expelled by a stream of carbonic acid gas and the tube is heated, without interrupting the current of gas, till the metal is all dissolved. J. B. Bailie | and C. Fery made a study of the production of aluminium amalgam, using the method just described ; their re- sults were as follows : " If aluminium foil is placed in a tube with mercury, it oxidizes very rapidly, becoming heated, while the mercury loses quickly its ordinary fluidity and becomes covered with a layer of alumina. By constructing thin glass tubes and filling them with known weights of aluminium and mercury, in an atmosphere of carbonic acid gas, heating the tubes on a sand bath, we verified these facts : — * Chemical Gazette, 1850, p. 339. t Gmelin's Hand Book, vi. 3. t Ann. de Chim. et de Phys., 1889, p. 246. 508 ALUMINIUM. " a. The amalgamation proceeds more rapidly the higher the temperature ; at the boiling point of mercury the solution is very active. "3. The vapor of mercury does not attack aluminium; only liquid mercury attacks it. " c. The weight of aluminium dissolved is proportional to the weight of mercury used, and reaches a certain maximum after a given time. "On cooling the bath of mercury obtained, it became evident that the amalgam consisted of a definite compound of alumin- ium and mercury dissolved in excess of mercury, for, on cool- ing, a crystalline paste separates out, floating on the bath. This paste was strained out, put in a covered crucible and heated in a current of hydrogen gas. The mercury distilled, leaving ar- borescent crystals of aluminium. We thus determined the composition of this compound to be, in 3.181 grammes. Mercury 2.902 grammes = 91.26 per cent. Aluminium 0.279 " ^ 8.74 " " Its formula is probably AlaHgs, which would require 8.26 per cent, of aluminium." These investigators further noticed that if a leaf of aluminium has been once attacked by mercury and afterwards exposed to the air, it cannot be again attacked, since the layer of alumina produced adheres so closely as to protect it perfectly. In order to attack it again it is necessary to drive off all the mercury by heat and remove the alumina by acid. A leaf may be com- pletely dissolved in a current of mercury. Properties of aluminium amalgam. — The aluminium in its amalgam is very easily acted upon ; indeed, it behaves like a metal of the alkaline earths. If let stand exposed to the air it covers itself immediately with gelatinous, opalescent excres- cences of pure hydrated alumina, exhibiting both in their form and growth considerable resemblance to the so-called Pharaoh's serpents. This hydrated alumina is perfectly soluble in acids and alkalies. However, the coating protects the portion un- ALLOYS OF ALUMINIUM. S09 derneath to some extent, so that it takes a long time, say 24 hours, for the mercury to free itself completely of aluminium. If the mercury containing aluminium is heated and agitated in, air, more or less anhydrous alumina is formed, colored reddish from a little mercuric oxide, but all the aluminium is speedily oxidized. Water is decomposed by it at ordinary temperatures, hydrogen being liberated. Acids attack the amalgam, dissolving the aluminium, even nitric acid (which does not attack aluminium en masse) dissolv- ing out the aluminium completely. Caustic potash acts simi- larly, forming potassium aluminate. Bailie and Fery determined also that if antimony amalgam is mixed with aluminium amalgam, small crystals of antimony form immediately on the surface ; later, the aluminium oxidizes and a bath of mercury remains free from both metals. Lead amalgam produces a similar effect, except that some lead re- mains with the mercury. It is interesting to note that this is quite similar to the action of lead on a molten alloy of alumin- fiim and tin, the aluminium being driven out of combination. Krauchkoll * states that if aluminium and iron together are connected with the negative pole of a battery and dipped into mercury covered with acidulated water, an amalgam of both iron and aluminium is obtained, which oxidizes more slowly in the air than aluminium amalgam. Helbig finds that when metallic aluminium is moistened with a solution of mercuric chloride, the white, hair-like formations characteristic of the oxidation of the amalgam are quickly formed. Even the dry salt will act similarly. Aluminium and Molybdenum. Molybdic acetate was dissolved in hydrofluoric acid, the so- lution evaporated to dryness, and the residue mixed with cryoHte, flux and aluminium, in the same proportions as given for tungsten. Excess of aluminium was dissolved from the * Journal de Physique, III., 139. 5IO ALUMINIUM. product with caustic soda, and there remained a black, crystal- line powder consisting of iron-gray rhombic prisms, soluble in hot nitric or hydrochloric acid, and containing only aluminium and molybdenum in proportions corresponding to the formula Al*Mo. (Wohler). Aluminium and Nickel. Tissier: " An alloy with 50 per cent, of nickel was made by melting together the metals in equal proportions under sodium chloride ; the heat evolved was sufficient to raise the mass to incandescence. This alloy remains pasty at the temperature of melting copper. It is so brittle that it pulverizes under the hammer. By melting proper proportions of this alloy with more aluminium, an alloy with 25 per cent, nickel was pro- duced. This is less fusible than aluminium, and as brittle as the 50 per cent, alloy. By melting some 25 per cent, nickel alloy with aluminium, a 5 per cent, nickel alloy was obtained. This is much less brittle than the preceding, but is still very far from being easy to work. From the 5 per cent, alloy one with 3 per cent, was made. With this amount of nickel the alumin- ium acquired much hardness and rigidity, and was easy to work. A curious fact with this alloy is that it may be melted on a plate of aluminium, showing its fusing point to be less than that of pure aluminium, the reverse effect to what irpn produces, which if present in the same proportion would di- minish the fusibility of the aluminium. To sum up, the action of nickel on aluminium is mdch analogous to that of iron, for nickel, like iron, produces crystalline alloys with aluminium, but if employed with care it gives to it certain desirable quali- ties, such as hardness, elasticity, etc." Michel* melted together aluminium with nickel chloride, and obtained an alloy with nearly 25 per cent, of nickel, which was tin-white, crystalline, specific gravity 3.65, but too brittle to be of any practical use. *Ann. der Chem. und Pharm., 115, 102. ALLOYS OF ALUMINIUM. 5 I I Lejeal states that an alloy he prepared containing 4.5 per cent, of nickel had a coarsely- crystalline fracture, was easily worked, rolled well, but gave poor mechanical tests, as follows : Tensile Strength. Elongation. Kilos per mm.- Lbs per in.- Per Cent. Forged cold and annealed. .. , 14.7 21,000 6.0 " at low red heat 16.0 22,800 5.5 " " weak cherry red 16.3 23,000 n.5 The Pittsburgh Reduction Company have recently com- menced selling aluminium hardened by a small per centage of nickel, made by adding nickel oxide directly to the bath in which alumina is being electrolyzed. They claim for these al- loys a tensile strength in castings of 25,000 to 30,000 pounds per square inch and in rolled bars or plates of 45,000 to 50,000 pounds. A bar of this metal shown to the writer was certainly very strong and possessed of great elasticity, suggesting its probable use for light wagon or carriage springs. These nickel alloys, however, do not resist corrosion as well as some of the other light alloys. Aluminium has been used in small amount in casting metal- lic nickel, as it reduces the nickel oxide and allows the metal to melt easier. An alloy of nickel 40 parts; aluminium, 30; tin, 20, and silver 10, has been named " roseine " and is recommended for jewelry. Aluminium-Nickel-Copper Alloys. The following alloy has a beautiful white color and takes a high polish. It resembles some of the finer grades of German silver: — Copper 7° parts- Nickel 23 " Aluminium 7 " A similar alloy, but somewhat harder, is called Minargent. It contains 512 ALUMINIUM. Copper loo parts = 56.5 per cent. Nickel 70 " =39.5 " Antimony 5 " = 2.8 " Aluminium 2 " ^ 1.2 " To make this alloy, the directions are first to melt together the copper, nickel and antimony, and then granulate the resulting alloy in water. The dried granules are mixed with the alu- minium and with 1.5 per cent, of a flux consisting of 2 parts borax and i part fluorspar, and then remelted. F. H. Sauvage states that the following alloy resembles pure silver. He gives it the name Neogen: — Copper 58 parts. Zinc 27 " Nickel 12 " Tin 2 " Bismuth 3^ " Aluminium J^ " P. Baudrin claims that the following alloy resembles silver very closely in color, malleability, ring, and even specific gravity: — Copper 75 parts. Nickel l6 Zinc 2y^ " Tin...... 2% " Cobalt 2 " Iron ii^ " Aluminium ^ " Mr. Jas. Webster has patented the composition of several bronzes containing nickel. Prof. Kirkaldy's tests on these alloys, made by the "Webster Crown Metal Company," now the " Aluminium Company, Limited," gave results from 82,000 to over 100,000 lbs. per square inch with 20 to 30 per cent, elongation. a)* Copper is melted and aluminium added to it until a ten per cent, bronze is made. There is then added to it i to 6 per cent, of an alloy, ready prepared, containing * German Patent, 11,577. ALLOYS OF ALUMINIUM. S13 Copper 20 parts. Nickel 20 " Tin 30 " Aluminium 7 " The alloy thus prepared would contain, as represented by the two extremes, I. II. Copper 89.3 86.4 per cent. Nickel. 0.3 1.4 " Tin 0.4 2.0 " Aluminium lo.o 10.2 " b)* The two following alloys are prepared in the usual way, under a flux consisting of equal parts of potassium and sodium chlorides, and are cast into bars : I. II. Aluminium 15 parts. Nickel 17 parts. Tin 85 " Copper 17 " Tin 66 " 100 " 100 " To make the bronzes, equal parts of these two alloys are melted with copper ; the more of the alloys used the harder and better the bronze. The best mixture is of Copper 84 parts. AlloyI 8 " " II 8 " 100 " The copper is first melted, then the alloys put in together and stirred well. As iron is harmful to this bronze, the stirrer must be of wood or clay. This alloy is suitable for art castings, kitchen utensils, etc., or anywhere where durability, hardness, malleability, polish and very slight oxidizability are required. A cheaper and more common alloy may be made of Copper 91 parts. Alloy I 4 " " II 5 " ♦German Patent, 28,117. 33 514 ALUMINIUM. These two bronzes would contain centesimally Rich alloy. Poorer alloy. Copper 85.36 94.58 Tin 12.08 6.70 Nickel 1.36 3.85 Aluminium 1.20 0.60 c) * The following alloy is said to withstand oxidation well, to have great tenacity, durability, capability to bear vibrations, and to take a high polish. A preliminary alloy is made of Copper 200 parts. Tin 80 " Bismuth 10 " Aluminium 10 " The alloy proper is-formed by melting together Preliminary alloy 4^ parts. Copper 164 " Nickel 70 " Zinc 6li^ " The final composition would be by calculation Copper 55-67 Nickel 23.33 Zinc 20.50 Tin 0.40 Bismuth 0.05 Aluminium 0.05 It will be noticed that this alloy contains the same ingredients as Baudrin's alloy, though not in exactly the same proportions, the principal change being that it contains more nickel and less aluminium. d) t Another alloy patented by Mr. Webster contains * English Patent; J8320, June 23, 1886. t United States Pat?pt, 377,918, Feb. 14, 1888. ALLOYS OF ALUMINIUM. 515 Copper 53 parts = 51.0 per cent. Nickel 22>^ " =21.6 " Zinc 22 " =21.2 " Tin 5 " = 4.8 " Bismuth 3^ " ^ o_y « Aluminium V •' ^ 0.7 " 1 00.0 " Lechesne " is an alloy not very different from some already mentioned, said to be invented by M. Thirion, but the English patent being taken out by the Societe Anonyme La Ferro- Nickel, of Paris. The patent mentions two alloys, containing I. II. Copper 900 parts. 600 parts. Nickel 100 " 400 " Aluminium i^ " 1^ " Which would give in per cents : — I. II. Copper 89.84 59.97 Nickel 9,98 39.98 Aluminium 0.18 0.05 100.00 100.00 The first of these alloys is the one to which the name "Lechesne" appears to be given. In a description of the manufacture of this alloy a French magazine states that the nickel is first put into a crucible and melted, the copper stirred in gradually, then the heat raised and the aluminium added. The alloy is heated almost to boiling and cast very hot. It is claimed that this alloy is equal. to the finest German silver, be- ing very malleable, homogeneous, strong and ductile, and stands hammering, chasing, punching, etc., perfectly. The proportion of aluminium in these bronzes last described is so small that it appears probable that its chief function must be as a deoxidizing agent, since a very small amount of oxygen dissolved in the bath would quickly combine with all the alu- minium added. In any event, very little can be left over, ap- parently too little to be able to account for all the improvement made in the alloy. 5l6 ALUMINIUM. Cowles Bros, have manufactured some of these bronzes, and have appropriated the name "Aluminium Silver" to the alloy- made by adding aluminium to German silver, or to their alloy of aluminium, nickel, and copper called "Hercules Metal." Two of their alloys were made of — I. II. 5 per cent, aluminium bronze i 2 Nickel 2 I containing respectively — I. II. Copper 31.67 63.33 Nickel 66.67 33-33 Aluminium 1.67 3.33 These alloys, on being tested, gave tensile strengths of 79,163 and 1 18,000 lbs. per square inch respectively, the first showing 33 per cent, elongation. They claim that an alloy of the pro- portions of II. will show an average strength of over 90,000 lbs. per square inch, but with very little elongation, and will take an edge in a manner that makes it quite suitable for table- knives. G. F. Andrews* states that the following alloys are all very hard, fine grained, and show great strength. Aluminium. Nickel. Copper. (I) 61^ 2ii^ 721^ (2) 10 24 66 (3) 12 33 5S (2) has the color of ten carat gold and takes a fine polish 1(3) has a beautiful golden-brown color ; ( i ) is similar, but richer and deeper. These alloys may become very useful for decora- tive purposes. Aluminium and Phosphorus. Wohler found that finely-divided aluminium, heated in phos- phorus vapors, burns and forms a dark-gray metallic mass, * Jour. Am. Chemical Society, July, 1 894, p. 486. ALLOYS OF ALUMINIUM. 517 smelling strongly of phosphoretted hydrogen ; it also evolves this gas copiously when placed in water. Shaw's phosphor-aluminium bronze is described in Chap. XV. Aluminium and Platinum. Aluminium alloys readily with platinum, forming alloys more or less fusible according to the proportion of aluminium. Tissier Bros, state that an alloy with 5 per cent, of platinum approaches in color gold containing 5 per cent, of silver, but is not malleable enough to be worked. Debray says that a small quantity of platinum (no definite amount named) can be toler- ated in aluminium without the malleability being destroyed. Aluminium and Silicon. Deville : " Any siliceous material whatever, put in contact with aluminium at a high temperature, is always decomposed ; and if the metal is in excess there is formed an alloy or a com- bination of silicon and aluminium in which the two bodies may be united in almost any proportions. Glass, clay, and the earth of crucibles act in this way. However, aluminium may be melted in glassware or earthen crucibles without the least con- tamination of the metal if there is no contact between the metal and the material ; the aluminium will not wet the crucible if put into it alone. But, the moment that any flux whatever facili- tates immediate contact (even sodium chloride does this) the reaction begins to take place, and the metal obtained is always more or less siliceous. It is for this reason that I have pre- scribed in melting aluminium not to add any kind of flux, even when the flux would not be attacked by the metal. Among the fusible materials which facilitate the melting of aluminium, it is necessary to remark of the fluorides that they attack the sihceous materials of the crucible, dissolving them with great energy, and then the siliceous materials thus brought into solu- tion are decomposed by the aluminium with quite remarkable facility. Aluminium charged with silicon presents quite dif- ferent qualities according to the proportion of the alloy. When 5 I 8 ALUMINIUM. the aluminium is in large excess, there is obtained what I have called the 'cast' state of aluminium, by means of which I dis- covered crystallized silicon in 1854. This 'cast' aluminium, gray and brittle, contains according to my analysis 10.3 per cent, of silicon and traces of iron. When siliceous aluminium is attacked by hydrochloric acid, the hydrogen which it disen- gages has an infected odor, which I formerly attributed to the presence of a hydrocarbon, but which we now know is due to hydrogen silicide, SiH4, thanks to the experiments of MM. Wohler and Buff. It is by the production of this gas that may be explained the iron smell which is given out by aluminium more or less contaminated with silicon. But aluminium may absorb much larger proportions of silicon, for, on treating fluo- silicate of potash with aluminium, M. Wohler obtained a mate- rial still metallic containing about 70 per cent, of silicon, some- times occurring as easily separable crystals. Since I had the occasion in a work which I published on silicon to examine a large number of these combinations, I found that they were much more alterable than pure aluminium or silicon, without doubt because of the affinity which exists between silica and alumina. I have, therefore, dwelt on and tried to explain the importance of this point in obtaining perfectly pure alu- minium." A small amount of silicon does not appear to be very inju- rious to the malleability of aluminium, which bears it much as iron and copper do, but over i or 2 per cent, commences to change its color, make it harder and, especially, crystalline, so that its malleability is rapidly impaired. The silicon, however, may be present up to even 5 per cent, without preventing the use of the metal for castings and articles not to be worked. Minet has proven that aluminium may contain even 8 per cent, of silicon and yet be quite strong, if the amount of iron present is small ; but if the iron increases over i per cent., the metal becomes worthless. The double role of silicon in aluminium, as combined and graphitoidal, was first pointed out by Rammelsberg (see p. 56), ALLOYS OF ALUMINIUM. SI9 and is now being noted in the analyses of the metal. It does not appear that chilling the metal has any influence in chang- ing one kind into the other, and no fixed rule has yet been ob- served as to the relative amounts of each kind existing in the metal. Aluminium and Selenium. Wohler* stated that if selenium and aluminium are mixed in- timately and heated together, they unite with a flame, leaving a black, pulverulent, metallic powder, which smells strongly of silicuretted hydrogen and evolves that gas violently when dropped into water. The Hquor is colored red from precipi- tated selenium. Aluminium and Silver. These alloys are easily made by direct fusion together of the two metals. All the alloys containing up to 50 per cent, of silver are more fusible than pure aluminium. In general, the introduction of a few per cent, of silver into aluminium benefits it considerably, increasing its hardness, capability of polish, making it whiter, denser and stronger. It has already been re- marked that aluminium will absorb almost 5 per cent, of silver without increasing in volume. A great advantage gained by this small amount of silver is also the increased facility of cast- ing, the metal filling the moulds better and shrinking less ; this alloy also rolls, draws, and works under the hammer like pure aluminium, requiring, however, more power to work it. Deville states that the alloy containing 3 per cent, of silver is unat- tacked by sulphuretted hydrogen, but Mierzinski states that every alloy of aluminium and silver is blackened more quickly than pure silver. I think the latter remark untenable, since the alloys with 3 to 5 per cent, of silver are noted for keeping their color like pure aluminium in places where silver would be im- mediately tarnished. With over 10 per cent, of silver, Mier- zinski's remark may be true. M. Christophle made statuettes of * Pogg- Ann., 1827, ii, 160. 520 ALUMINIUM. the alloy with 3 per cent, of silver, which kept their beautiful white color permanently, With 5 per cent, of silver, aluminium becomes elastic and as hard as coin silver with 10 per cent, of copper, but is still as malleable as pure aluminium. It has a specific gravity of 2.8, casts better than aluminium, shrinks less, and can be rolled or drawn perfectly, but requires more power than pure aluminium. It has been used for dessert-spoons, knife-blades, and even for watch-springs. This is the alloy which has often been pro- posed as a substitute for coin silver, since it contains no such poisonous metal as copper, and the color is not appreciably dififerent from that of pure silver. The beams of fine balances when made of aluminium contain from 3 to 5 per cent, of silver. The alloy with 3 per cent, of silver and 2 per cent, of copper, strongly compressed cold, is also recommended. The alloy containing 10 per cent, of silver is much harder than the foregoing. It casts well, and can be rolled at a par- ticular heat, but it does not work well under the hammer. Dr. Carroll, manufacturer of dental plates, uses an alloy for casting these articles* composed of — Aluminium 90 to 93 parts. Silver 5 to 9 " Copper I " This alloy, when cast under slight pressure, gives perfett castings, is very white and easy to work. The addition of cop- per is said to decrease to a minimum the shrinkage of the alloy, also giving it a closer grain. The alloys containing from 10 to 50 per cent, of silver are all brittle and cannot be worked under the hammer. Debray states that the 50 per cent, alloy is as hard as bronze. "Tiers Argent" is an alloy of two-thirds aluminium and one-third sil- ver. It is chiefly made in Paris ; its advantages over silver are that it is cheaper, harder, and can be stamped and engraved with greater ease than the alloys of silver and copper. Some * U. S. Patent 373,221, Nov. 15, 1887. ALLOYS OF ALUMINIUM. $21 difficulty was met, at first, in getting the alloy homogeneous ; but this has been overcome, and spoons, forks, salvers and articles generally made of silver are now made of this metal with an ap- pearance equal to that of any other silver alloy. Tissier Bros, stated that the alloy with 33 per cent, of silver (the same as "Tiers Argent") is fusible enough to be used as a solder for aluminium, but they found difficulty in running it out, and also found that it made a brittle joint. Hirzel* made alloys of aluminium and silver in atomic pro- portions, containing from 6 to 20 per cent, of aluminium. He found the alloy AlAg, containing 20 per cent., to be silver- white, very porous, tarnishing in the air, with a specific gravity of 6.73 ; the alloy AlAg^, containing 11. 11 per cent., to be also silver-white, less porous, also tarnishing in the air, specific gravity 8.744; and the alloy AlAg^, containing 5.9 per cent., to be pure silver-white, very malleable and forgeable, tarnishing in the air and with a specific gravity of 9.376. Aluminium and Sodium. Deville states that aluminium unites easily with small propor- tions of sodium ; with i to 2 per cent, it decomposes water in the cold. It follows from this that the properties of the metal made carelessly by using sodium are completely altered. The last traces of sodium can be removed only with great trouble, especially when the aluminium has been produced in presence of fluoride, because of the marked affinity of aluminium for fluorine at the temperature at which aluminium fluoride, AIF3, commences to volatilize. Aluminium and Tellurium. Wohler states that when heated together in powder, these elements combine very violently, leaving a black, brittle, metal- he mass, smelling strongly of tellurretted hydrogen and evolv- ing that gas actively when put into water. The water becomes first red, then brown, and finally opaque, from precipitated tel- *Bayerisches Kunst und Gewerb-Blatt, 1858, p. 45'- 522 ALUMINIUM. lurium. Put on paper, a piece of this alloy forms a brown, me- tallic ring around it. Wohler noted that it decomposed water even more energetically than aluminium sulphide. Aluminium and Tin. These two metals unite readily, small amounts of either metal changing the properties of the other quite materially. A small amount of tin renders aluminium brittle. Tissier Bros, made an alloy with 3 per cent, of tin, melting the metals under sodium chloride, then remelting once without any flux. This alloy was a little more fusible than aluminium, but very brittle ; the grain was very fine and crossed, but the bar broke at the first blow. Deville stated that these alloys with a small proportion of tin may be used as solders for aluminium, but they answer only imperfectly. M. Bourbouze* has recommended the use of an aluminium- tin alloy for the interior parts, especially, of optical instruments, in place of brass. The alloy formed of 100 aluminium to 10 of tin, or 9 per cent, of tin, is recommended as being the best for this purpose. It is white and has a specific gravity of 2.85, only slightly above that of aluminium itself. It may therefore be used in place of aluminium where great lightness is desired, and it is further superior to aluminium itself in resisting altera- tion better, being more easy to work, and finally it can be sojd- ered without any special apparatus, as easily as brass, particu- larily if the solder recommended by M. Bourbouze (p. 463) is used. If the alloy does work as well as represented by Bourbouze, there must be a very sudden change in the properties of alu- minium alloys between the 3 per cent, tin alloy described by Tissier Bros, and this 9 per cent, alloy; but from analogy with other aluminium alloys we admit that this is not im- possible. Having so many advantages over aluminium it should replace it for many purposes, especially in instruments of a portable character ; it would, besides, be somewhat cheaper *Comptes Rendus, cii., p. 131 7. ALLOYS OF ALUMINIUM. 523 than pure aluminium. An analysis of some of this metal ex- hibited at the Paris Exposition of 1889 gave Aluminium 85.74 per cent. Tin 12.94 " Silicon 1.22 " Iron . none. A test by Minet of a similar alloy, containing tin 10 per cent, aluminium 88, silicon i;30, iron 0.65, gave a tensile strength in casting of 9.8 kilos per square m. m. (14000 pounds per sq. in.) with an elongation of only 4. 11 per cent. It thus appears that this alloy is in reality not quite so strong as aluminium itself. At the other end of the scale we have alloys containing only a few per cent, of aluminium. Aluminium gives to tin greater hardness and tenacity if it is not present in too large an amount. The alloy with 3 per cent, of aluminium is harder than tin and less acted on by acids ; 5 per cent, of aluminium gives a much stronger and more elastic metal. The alloy with 7 per cent, of aluminium is especially recommended as being easy to work, being malleable at a red heat, and capable of a good polish, but possessing the drawback that it cannot be melted without a part of the tin separating from the aluminium. Tissier Bros, state that tin will not combine with more than 7 per cent, of aluminium, for they state that the alloy with 10 per cent, is not homogeneous, and on cooling in a mould ar- ranges itself in two layers, an upper brittle one, a little more fusible than aluminium, and a lower one containing nearly all the tin, but rendered harder and less fusible than pure tin by a small quantity of aluminium. I have not been able to notice this liquation. Mr. Joseph Richards prepared an alloy with 10 per cent, of aluminium, which was whiter and much stronger than tin and kept its color perfectly in the air. It had a specific gravity of 6.45 (calculated value 6.28) and melted only imper- fectly at a temperature slightly above that of tin. It was quite malleable, but became hard by rolling. On heating a piece of S24 ALUMINIUM. this, in the form of sheet, at a gradually increasing temperature, small globules sprouted out in all directions, but they were identical in composition with the bulk of the alloy, so that no separation had taken place. The surface of the sheet appeared harder than the interior, and did not melt so easily, but this property seemed to result from other causes than difference in composition. After standing several months a peculiar inter- nal change took place in this metal by which it lost all its mal- leability and became as rotten as baked clay, and annealing could not restore its strength. The same disintegration has been noticed with even smaller proportions of aluminium. A metal company in Philadelphia, which makes tin foil, tried the experiment of adding less than I per cent, of aluminium to their metal. It rolled beautifully and had a fine color, but in a few hours it became brittle, and in a few days it had all fallen to powder. Heycock and Neville have noticed that very small amounts of aluminium lower the melting point of tin, a minimum freez- ing point of 3 degrees lower than tin itself being obtained with 0,48 per cent, of aluminium. Very careful experiments showed this lowering to be, within the limit of 0.25 per cent, alumin- ium, at the rate of 1.3° fall per i atom weight of aluminium dissolved in 100 atom weights of tin. The alloy with 19 per cent, of aluminium is said to be mal- leable and workable at a red heat, though not so much so* as the 7 per cent, alloy. The alloys with over 30 per cent, of alu- minium are described as silver-white, porous and brittle. Minet found the alloy of 50 tin, 48.9 aluminium, 0.72 silicon and 0.36 per cent, iron to be malleable, but when forged it had a tensile strength of only 10 kilos per sq. m. m. (15,000 lbs. per sq. in.) with practically no elongation. The melting' points of a number of these alloys have been determined by Minet as follows, making the alloys with com- mercial aluminium containing 1.50 per cent, silicon and 0.76 per cent, iron, whose melting point was 619° C. : — ALLOYS OF ALUMINIUM. 525 Comme'cial aluminium. Tin. Fusing point, 100 o 619^ C. 92 8 595° 80 20 .....575° 7° 30 535° 60 40 575° 5° 50 570° 20 80 530° 10 90 490° o 100 233° Two points are worthy of particular attention in this table. First, that 10 per cent, of aluminium serves to raise the melting point over 250°, or 60 per cent, of the total difference between the melting points of the two metals. Second, the sudden drop at 30 per cent, tin, which looks almost as if a mis-print had been made. The alloy Ali„Sn would correspond to 30.4 per cent of tin. By a peculiar co- incidence, there will be noted in the melting points of aluminium-copper alloys a similar sudden fall at 20 per cent, of copper, and oddly enough, the alloy AlioCu calls for 19 per cent. Aluminium and Titanium. Wohler* obtained an alloy by melting together — Titanic oxide 2 parts. Cryolite 6 " Potassium and sodium chlorides 6 " Aluminium I " The excess of aluminium being dissolved out of the mass by caustic soda, bright, steel-colored crystals remained, containing aluminium, titanium, and a little iron and silicon from the aluminium used. The specific gravity was 3.3 ; the alloy was infusible before the blowpipe, but on ignition in chlorine gas burnt, forming chlorides of all the metals present. Its composi- tion seemed to vary, for another experiment at a lower tempera- ture gave an alloy richer in silicon, with a specific gravity of 2.7. On heating these alloys in the air they first become yellow, then steel-blue, and after that oxidize no further. *Ann. der Chem. und Pharm., 113, 248. 526 ALUMINIUM. Michel, proceeding in a similar way, obtained an alloy whose analysis denoted the formula AlsTi, containing about 62 per cent, of aluminium. L. Levy* describes an alloy which he obtained by similar processes, as being in crystalline plates, insoluble in water, alcohol, or ether, steel-gray in color, brittle, and conducting heat and electricity. Specific gravity 3.11 : composition on analysis — Aluminium 70.92 Titanium 26.80 Silicon 2.1 7 In 1 89 1, the Pittsburgh Reduction Company began to manu- facture alloys of aluminium with 0.5 to 2 per cent, of titanium by a process analagous to Wohler's. Cryolite is melted in a carbon-lined crucible, and titanic oxide dissolved in it. After thorough solution, aluminium is introduced, solid or liquid, and the heat continued. The titanic oxide which has been added will be completely reduced to titanium, which alloys with the aluminium, and the per cent, of titanium in the alloy is regu- lated by the weight of aluminium added. These alloys are harder than aluminium, and when rolled have a degree of elasticity comparable to spring brass, with a tensile strength of 30,000 to 40,000 pounds per sq. inch. If chromic oxide is ad- ded to the bath as well, a triple alloy of aluminium, titanium and chromium is obtained which is very hard and rigid. The titanium alloys alone will bear a cutting edge about as well as soft steel, and have been already used for potato and fruit knives. Lejeal made an alloy with 7 per cent, of titanium, and calls attention to its peculiar fracture, which is traversed by sharp lines like the top of a butcher's block. The following mechanical tests were made in Le Verrier's laboratory : * Comptes Rendus, 106, 66, (i ALLOYS OF ALUMINIUM. 527 Titanium. Tensile Strength. Elongation Per cent. Kilos per sq.m.m. Pounds per sq. in. Per cent. 2.9Z (rolled poorly) 19 27,000 2.5 2.20 (rolled well) 24 34,000 5.0 1.70 (rolled well) 20 28,000 1.5 " (annealed) 15 21,000 16.5 These results agree with the experience of the Pittsburgh Company, who have found 2 per cent, to be about the strong- est alloy. While these alloys are very strong, yet they are not of as fine color as pure aluminium, being somewhat leady in appearance, and they do not solder so easily. Still, for pur- poses where great strength and elasticity combined with light- ness are the prime requisite, and looks are a secondary consid- eration, the 2 per cent, alloy can be highly recommended. Aluminium and Tungsten. Michel fused together — Tungstic acid 3 parts. Cryolite 6 " Potassium and sodium chlorides 6 " Aluminium 3 " at a strong red heat. The fusion was afterwards treated with hydrochloric acid, leaving an iron-gray, crystalline, brittle pow- der, single crystals being several millimetres long. Hot caustic soda extracted from them all their aluminium, leaving pure tungsten. Their specific gravity was 5.58, and the composi- tion corresponded to the formula Al^W, containing 37 per cent, of aluminium. Mannesmann recommends the addition of small quantities of tungsten for improving the resistance of aluminium to corrosion. He also claims greatly increased strength. Tests made in Le Verrier's laboratory show properties similar to the titanium alloys. The following are the properties of the alloy with 7.5 per cent, of tungsten : Tensile Strength. Elongation. Kilos per sq, m.m. Pounds per sq. in. per cent. Cast 15.5 22,000 1.5 Rolled hard 25.0 3S>ooo 4.0 Annealed 18.0 25,000 lo.o " 15.9 22,000 14.0 528 aluminium. Aluminium and Zinc. Aluminium unites readily with zinc, the alloys being in gen- eral harder and more fusible than aluminium. Some of the first attempts to solder aluminium were with these alloys, con- taining 6, 8, 12, 15, and 20 per cent, of aluminium. They an- swered better than any other solders which had been tried, but unfortunately, when melted they are thick and run with difiS- culty, so much so that it is necessary to spread them over the joint as a plumber does when he wipes the joints of lead pipes. Joints thus made stand hammer blows or rough usage very poorly. The alloy containing 10 per cent, of aluminium is brittle, has the appearance of zinc, is more fusible than aluminium and less so than zinc. The alloy with 25 per cent, of aluminium has a fine, even grain, and is of about the same fusibility as the pre- ceding. The alloy AlZn, containing 29.5 per cent, of alumin- ium, forms a silver-white, very brittle, crystalline alloy, with a specific gravity of 4.53. It was noticed that in the preparation, when the two metals were fused together in this proportion . under a layer of sodium and potassium chlorides, they united with incandescence. The 50 per cent, alloy is white, crystalline, brittle, and does not appear to be homogeneous, for the Tis- sier's report that when heated on an aluminium plate it sepa- rated into a fusible portion which ran off, and a less fusible part which did not melt until the plate did. When zinc is in small proportion in aluminium it makes it brittle, unless below a very few per cent, in quantity. The alloy containing 3 per cent, of zinc is described by Debray as harder than .aluminium, very brilliant, but still quite malleable. Some of the aluminium first made by Deville contained zinc, the presence of which he accounted for as follows: "The re- torts used for making the aluminium were made at the Vielle Montagne Zinc Works, and having in their mixture some ground-up old zinc retorts, the new retorts contained zinc, which passed into the aluminium and altered its properties in a very evident manner. Some analyses of this metal having been ALLOYS OF ALUMINIUM. 529 made in England, some asserted that French aluminium was only an alloy to which zinc gave a fusibility which might be wanting in pure aluminium. The addition of both zinc and copper to aluminium makes a very stiff metal in castings. Alloys with five per cent, copper and I S per cent, of zinc, also 3 per cent, copper and as high as 27 per cent, of zinc have been used very successfully in cast- ings where great rigidity was desired. If such castings are made under pressure they are still stronger. Aluminium has found considerable use in the zinc industry. Mr. Joseph Richards, of the Delaware Metal Refinery, Philadel- phia, has patented * the addition of a very small amount of alu- minium to the galvanizing bath. An alloy is prepared contain- ing 2 per cent, of aluminium, and it is recommended to add i pound of this alloy to each ton of zinc in the bath. ,The efifect is to make the zinc more fluid, a given weight coating 20 per cent, more surface, and the sheets produced being brighter and keeping their color better. The bath also oxidizes less, and so produces less skimmings, although, as the metal is rendered more fluid, the per centage of " dross bottoms" {i. e. impurities settling out of the zinc) is increased. As the amount of alu- minium added is only o.ooi per cent., the cause of its marked effects seems difficult to explain. It has seemed to the writer that it acts chemically on dissolved oxygen or dissolved oxide of zinc in the bath, which substances have a strong tendency to render the metal thick or mushy. By completely eliminating the last trace of these ingredients, the aluminium gives the bath its maximum fluidity. The beneficial effects, in fact, are so well established that almost every galvanizer in the United States is already using Mr. Richards' process. Similar advantages are gained by using a small percentage of aluminium in the zinc used in desilverizing (Parke's process). Here zinc is stirred into silver-lead, and kept at a low red-heat for several hours, and the addition to it of aluminium gives it much greater resistance to oxidation. With i per cent of alu- * U. S. Patent, March, 1891. 34 530 ALUMINIUM. minium the zinc will remain clear and white, even at a red heat. The improvement can be noted with even o.i per cent. Instead of repeatedly adding zinc to the lead in several kettles, the whole of the silver may be removed from the lead in one operation. A German patent of Rossler * recommends using as high as 0.5 per cent, of aluminium. The scums are removed on cooling the bath, and are almost entirely free from oxide, thus allowing them to be liquated easily with very lit- tle loss, and giving a rich zinc -silver alloy almost entirely free from lead or oxides. The small amount of aluminium used is almost entirely oxidized out during the process; but if the scums are burnt to zinc oxide, what aluminium is left passes as alumina into the zinc oxide. A luminium-Zinc- Copper A Hoys. These alloys are generally known as " aluminium brasses," and are about as much superior to ordinary brass as aluminium bronze is to ordinary bronze. They are made in two general ways ; either by introducing metallic aluminium into melted brass, or by introducing zinc into melted aluminium bronze. The latter method is pursued by the Cowles Smelting Com- pany, because they produce the bronze directly, while the makers of pure aluminium claim that the first method is su- perior, because by adding aluminium to melted brass the dis- solved cuprous oxide and zinc oxide are removed, producing a dense metal, casting without pores, while the aluminium already combined with copper does not have this effect. It appears, however, that the Cowles brasses are equal in strength, elonga- tion, and casting qualities to those made with pure aluminium. Repeated remeltings of aluminium brass are not advisable, since, like all brasses, it changes in composition on melting, though not to so large a degree. After mixing, it need be re- melted only once in a clean crucible. Aluminium brasses flow well, give sharp, sound castings, are more ductile, malleable, and have greatly increased strength and power to resist cor- * No. 64,416, 1892. ALLOYS OF ALUMINIUM. 53 I rosion. The working qualities are said to be governed largely by the percentage of zinc present, an increase of which makes the brass harder, but does not injure its malleability. Numerous tests have been made of the strength and elonga- tion under stress, of aluminium brasses. Even i per cent, of aluminium is found of benefit, while the strength increases with the amount of aluminium. As early as 1863, Julius Baur, of New York, obtained a patent* for alloys containing — Copper 14-16 parts. Zinc 10 " Aluminium 0.1-3 " which he stated were of great hardness, toughness and dura- bility. This alloy differs from the aluminium brasses now made only in containing about half as much again of zinc. The next year, M. G. Farmer, of Salem, Mass., patentedf an alloy con- taining — Copper 65-80 parts. White metals 3S-io " Aluminium 0.3-10 " Cowles Bros, report the following series of tests made, in 1886, at their works in Lockport, their alloys all being made by adding zinc to aluminium bronze : Compo s ition. Tensile strength per Elongation, Aluminium. Oopper. Zinc. sq. inch (castings 1. percent. 5.8 67.4 26.8 95.712 I.O 3-3 63.3 33.3 85,867 7.6 3.0 67.0 30.0 67,341 12.5 i.S 77-5 21.0 32,356 41-7 1.5 71.0 27.5 41.952 27.0 1.25 70.0 28.0 35.059 25.0 2.5 70.0 27.5 40,982 28.0 1.0 57.0 42.0 68,218 2.0 1.15 55.8 43.0 69,520 4.0 *U. S. Patent, 40388, Oct. 1863. tU. S. Patent, 44086, Aug., 1864. 532 • ALUMINIUM. When it is remembered that ordinary brass rarely has a ten- sile strength over 30,000 lbs., with elongation about 10 per cent., the benefit of the aluminium can be easily realized. Gov- ernment tests of this company's brasses, to determine their suitability for steamship propellers, were made on the alloy composed of i part 10 per cent, bronze, i part copper and i part zinc, containing therefore — Aluminium 3.3 per cent. Copper 63.3 " Zinc 33.3 " The test pieces were 22 inches long, i % inches diameter, and 10 inches between elongation marks. The results showed a tensile strength of 70,000 to 82,500 lbs., elastic limit 55,000 to 65,000 lbs., and elongation 1.6 to 2.5 per cent.; having, there- fore, a tensile strength three times and elastic limit four times as great as the best Government bronzes. The Aluminium und Magnesium Fabrik, of Bremen, state the strength of aluminium brass according to their tests to be — 2 aluminium, 23 zinc, 75 copper 41,000 lbs. 2 " 30 " 68 " 49.530 " 2%. " 30 " 671^ " 65,400 " Prof. Tetmayer, of Zurich, has tested the strength of alumin- ium brasses with the following results : — Strength. ^, , A ^ Elongation, Content of aluminium. Kilos per sq. mm. Lbs. per sq. in. per cent. 4 per cent. 69 98,100 6J^ 3 " 60 85,300 7>4 2>^ " 52 73.900 20 2 " 48 68,250 30 13^ " 45 64,000 39 I " 40 56,900 50 The amount of zinc in these brasses is not stated, but was probably 25 to 30 per cent. In general, then, we may conclude that even a fraction of i per cent, of aluminium added to brass will increase very re- ALLOYS OF ALUMINIUM. 533 markably its strength and ductility, while about 5 per cent, will make an alloy, having brought its tensile strength close up to 100,000 lbs. per square inch. This indicates that as far as strength alone is concerned the cost of aluminium brass castings is less than aluminium bronze castings of the same strength, for they contain less aluminium and a quantity of the cheap metal zinc. The principal disadvantage of the brass compared with the bronze is, that it cannot be remelted without changing its quality, by reason of its containing zinc. A remarkable property of the aluminium brasses, however, is their capability of forging at a red heat; even 0.5 per cent, added to ordinary brass imparting to it this quality. A very strong and, at the same time, cheap alloy is that known as " Richards' Bronze," the invention of Mr. Joseph Richards of Philadelphia. It contains copper 5 5 parts, zinc 42 or 43, iron i, aluminium i to 2. This alloy is of a golden- yellow color, is exceedingly fine-grained, and has a tensile strength in castings of 50,000 pounds per square inch with 15 per cent, elongation. Like all the strong bronzes, however, it requires some experience in handling before the ordinary metal-worker can turn out uniformly castings with these maxi- mum properties. The worked metal averages 50 per cent, stronger. CHAPTER XV. ALUMINIUM-COPPER ALLOYS. These two metals unite readily in many proportions, the union being attended with evolution of heat, which in some cases is very large in amount. As has been noticed with re- gard to the alloys of other metals with aluminium, so here we note that the useful alloys of these two metals are in two groups, 1st — those in which a small percentage of copper im- parts certain advantageous properties to aluminium ; 2d — those in which a limited quantity of aluminium enhances the useful properties of copper. The latter is by far the class of most im- portance industrially. * General Properties. The color of aluminium-copper alloys is white until the per- centage of coppfer exceeds 80 per cent, or until its bulk be- comes equal to that of the aluminium with which it is alloyed. Above this amount of copper, the color becomes first slightly violet and then yellowish, until with 90 per cent, the alloy is a light golden yellow; at 92.5 per cent, the color is greenish- gold; at 95 per cent, the full color of 18 carat gold alloyed with silver; at 97.5 per cent, the color of 18 carat gold alloyed with copper ; above that amount, the color of red brass. Le Verrier has made a study of the melting points of the aluminium-copper alloys by means of the Le Chatelier pyro- meter, and has published the following results for alloys of commercial aluminium : (534) ALUMINIUM-COPPER ALLOYS. 535 Composition. Aluminium. Silicon. Iron. Copper. Melting Point (C°) 100.00 62s 97-75 1.50 0.75 619 90.00 1.40 0.70 8 587 89.00 1-35 0.68 10 578 83.00 1.28 0.64 IS 573 78.20 1.20 0.60 20 528 73-30 •-I3 0.56 25 553 65-5° 1. 00 0.50 33 527 58.70 0.90 0.45 40 535 48.90 0.7s 0.38 50 553 36.70 0.56 0.28 62.5 545 29.30 0-45 0.23 70 692 22.00 0-34 0.17 77-S 694 19.60 0.30 0.15 80 947 12.20 0.19 0.09 87-S 974 9.80 0.15 0.07 90 1029 7-3° 0.1 1 0.05 92-S 1000 4.90 0.08 0.04 95 100 1030 1054 If these melting points are carefully examined, several pecu- liarities are noticed, indicating chemical alloying. The natural compounds of aluminium and copper are those with the for- mulae AlCuj and AljCuj, containing respectively 12.4 per cent and 22 per cent, of aluminium. Both these alloys are well marked. The first melts completely without liquation and crystallizes in prisms, while all the alloys with a smaller pro- portion of aluminium have a serrated fracture. The fall of the melting point at 7.5 per cent, of aluminium indicates combina- tion at this point, and its formula, AlCuj, may be understood as A\Cu^ plus Cuj, indicating that it is a chemical combination of the 12.4 per cent, alloy with a definite amount of copper. Its behavior on cooling supports this view, by showing indications of free copper in passing the melting point of copper. It is also interesting to note, that if we consider the specific gravities of the two metals, the alloy AlCuj consists of a combination of one volume of aluminium to two volumes of copper, truly a very simple relation. The alloy Al^Cu., is also very sharply defined. It contains 536 ALUMINIUM. 22 per cent, of aluminium, but its melting point, 994°, is 250° lower than that of the alloy with 20 per cent. That a differ- ence of only 2 per cent, in composition should make this ex- treme change in fusibility is very curious. This alloy, more- over, consists by volume of equal parts of aluminium and copper, and it is at this point that the yellow color of the lower alloys fades out entirely, and the alloy is white. Another sharp fall in the melting point at 37.5 per cent, of aluminium indicates the alloy AljCuj, in which the proportions of the two metals combined by volume is 2 aluminium to i of copper. Its melting point is 545° C, or 80° below that of alu- minium alone ; a fact which is very remarkable considering that the alloy contains over half of its weight of copper. From this point until the percentage of aluminium is over 80, the melting point remains between 500° C. a;nd 550°, with pos- sibly definite alloys at AljCu (68 per cent.) and AluCu (81 per cent). What the true constitution of these alloys is must be left to conjecture. They are probably definite compounds of AI2CU3 with fixed quantities of aluminium ; or, as we might put it, AI2CU3 dissolved in a certain excess of aluminium. From 85 per cent, of aluminium, the melting point rises; from 90 per cent, upwards at a nearly uniform rate of 4° for each per cent, increase. We therefore note the singular fact, that the addition of copper to aluminium, in amounts up to 10 per cent., lowers the melting point of the latter about 4° for every per cent, of copper present. The study of the specific gravities of these alloys would be most interesting, but, unfortunately, the data are largely wanting. Alloys of the First Class. A small percentage of copper hardens aluminium, but does not take away its malleability. I have observed that a very small amount, less than o.i per cent., closes the grain of com- mercial aluminium, making it look more compact, and for that reason whiter, on a fractured surface. This small amount makes the aluminium perceptibly harder. It has been ob- ALUMINIUM-COPPER ALLOYS. 537 served that by adding a small amount of copper to aluminium much better castings are obtained and with greater ease than with pure aluminium. The reason is probably that the copper is mostly absorbed into the aluminium, so that it shrinks less in cooling and casts more solidly. Christofle, of Paris, exhibited at the London Exhibition in 1862, statuettes of a beautful sil- ver-white color made of aluminium with i per cent of copper. Deville states that the addition of 2 or 3 per cent, of copper was found useful in making large art-castings, and that the alloy produced worked very well under the chisel and burin. The metal reduced by Deville in copper boats (see p. 255) contained from 5 to over 6 per cent, of copper, yet it could be worked easily. This malleability is retained until the copper exceeds 10 per cent., above which quantity brittleness sets in. Cowles Bros, report the alloy with 16.8 per cent, of copper as having a specific gravity of 3.23, tensile strength 29,370 lbs. per square inch, but elongation almost nothing, the alloy being too brittle for any practical use. Alloys containing from 30 to 40 per cent, of copper are very brittle, and hard as glass and beautifully crystalline. The alloys with small percentages of copper have recently been in great favor with constructors of aluminium apparatus, boats, etc. The works at Froges, France, makes regularly a 6 per cent, alloy which rolls well, and has the following mechan- ical properties : Tensile Strength.. Elongation. Treatment. Kilos per sq. m. m. Pounds per sq. in. Per cent. Rolled hard 25 35,000 3.5 Annealed 18 25,000 15.5 Captain Julien made experiments with these alloys at the Aerostatic Park at Meudon, and gives the following properties of sheet i milHmetre thick cut in strips 5 millimetres wide : Observed. Calculated. Tensile Strength. Per cent, of Copper. Specific gravity. Specific gravity. Kilos per sq. m. m. Pounds per sq. in 2.67 2.67 18.7 26,500 2 2.71 2.71 30-7 43.500 4 2.77 2.7s 3I-I 44,000 6 2.82 2.79 38.6 55,000 8 2.84 2.83 39-S 56,000 538 ALUMINIUM. These light alloys do not resist corrosion as well as pure alu- minium, but they cast well and are very suitable for many purposes where lightness and strength together are wished. The alloy with 2 to 3 per cent, of German-silver, first de- scribed by the writer, may be also commended as being of a fine white color, strong, and quite elastic. When rolled hard, its tensile strength exceeds 40,000 pounds, -with an elongation of 3 to 5 per cent., while in casting its strength is 22,000 pounds, or 50 per cent, stronger than aluminium. The fine color and elasticity of this alloy commend it for many purposes where pure aluminium is too soft and non-elastic. Alloys of the Second Class. Aluminium is more efficient than any other metal in improv- ing the qualities of copper. Under this second head we shall consider these alloys made by adding to copper any quantity of aluminium up to the limit within which the alloys are of prac- tical value. This limit has been definitely established at about 1 1 per cent. ; and the alloys here included are generally known as " the aluminium bronzes," being particularized as i per cent, bronze, 5 per cent, bronze, etc. ; but on account of its general superiority over all the rest, the alloy with about 10 per cent, of aluminium has received the title. of "aluminium bronze" — without any qualifications. This distinction has come into gen- eral use, and it will be well to keep it in mind in going over the succeeding pages, for, whenever the expression " the aluminium bronze'' or " aluminium-bronze'' occurs without the percentage of aluminium being specified, the 10 per cent, alloy is signified. The late Dr. Percy seems to have been the first to call atten- tion to these beautiful alloys, but I am unable to find any ac- count given by him beyond the statement that " a small pro- portion of aluminium increases the hardness of copper, does not injure its malleability, makes it susceptible of a beautiful polish, and varies its color from red-gold to pale-yellow." This statement must have been made prior to 1856. In that year, Tissier Bros, brought aluminium bronze to the notice of the ALUMINIUM-COPPER ALLOYS. 539 French Academy,* and a week later a paper by Debray.f hur- riedly put together, made known the results obtained up to that time by Messrs. Rousseau, Morin and himself at La Glaciere. Aluminium bronze went through the same experience that aluminium itself and all its other alloys underwent during the first decade after its discovery. It was unduly praised, too much claimed for it, and so, while its wonderful properties did sustain for a season all the exaggerations heaped upon it, yet some unprejudiced observers soon made known the true state of the case, and determined its proper place among the alloys ; but, as even the high place finally accorded it was far below the first expectations, we have seen the alloy become the subject of unmerited fault-finding. If some people expect too much of the alloy, and are therefore disappointed, let them blame them- selves, or, perhaps, those who led them to expect so much, and not the metal. The history of the application of aluminium bronze is summed up in the oft-repeated expression " it would come into extensive use in the arts if its price would permit." Since, until recently, it was made by melting directly together the copper and aluminium, its price was naturally dependent upon that of the latter metal, and by reference to the price of that metal in dififerent years, it is an easy matter to figure out what one-tenth of a kilo or pound of aluminium would cost to make a kilo or pound of bronze. In 1864, Morin, of Paris, quoted the alumin- ium bronzes at the following prices : — 10 per cent, aluminium 15 francs per kilo (I1.36 per lb.). 7>^ " " 12}4 " " («I.I4 " ). 5 " " 10 " " (;?o.9i " ). During the years from i860 to 1883 the price of aluminium remained almost constant, its use was not extended, and its *Comptes Rendus, 43, 885 (Nov. 3, 1856). tComptes Rendus, 43, 92s (Nov. 10, 1856). 540 ALUMINIUM. bronze shared the same apathy. In 1 879, the Societe Anonyme de TAluminium quoted — 10 per cent, aluminium bronze 18 francs per kilo (^(1.64 per lb.) which does not show much improvement on the price of fifteen years before. And so the bronze was kept out of almost every possible industrial application until 1885, when the ap- plication by Cowles Bros, of the electric furnace to the reduc- tion of alumina in presence of copper brought the question of aluminium bronze nearer to a practical solution than it had ever been before. They sold the alloy at the start on the basis of $3.50 per pound for the contained aluminium, which brought the price down to — 10 per cent, aluminium bronze ^60.50 per lb. For several years, the Cowles Company and the owners of the Heroult process sold large amounts of aluminium bronze on the basis of $2.50 per pound for the contained aluminium, and in 1890 on the basis of $1.50 per pound, which made the price of 10 per cent, bronze $0.30. However, when the price of commercial aluminium dropped below $1.00 per pound, and especially since it has reached $0.50, the bronze can be made from the pure metals, in any grade desired, so cheaply and ac- curately, that the sale for ready-made bronzes has well-nigh vanished. Users of the bronzes prefer to do their own mixing, and make the alloys according to their own formulae. With copper worth $0.10 per pound, and aluminium $0.50, the metals in 10 per cent, bronze cost only $0.14; and if the cost of making is added, the total cost in ingots is not over $0.16 per pound. At such prices, there is no margin of profit left to the makers of bronzes by the alloy processes. This reversal of industrial conditions since 1890 has been a prominent fea- ture of the aluminium industry. Constitution of the bronzes. — The question whether the alu- minium bronzes are chemical combinations of the two metals composing them has long been argued pro and con. It is ALUMINIUM-COPPER ALLOYS. 541 acknowledged that the bronzes containing about 21^, 5, "jY^ and a little less than 10 per cent, aluminium behave most like true alloys, or chemical combinations in which the identity of the constituents is sunk completely in that of the compound. There is a coincidence to notice here, which would be remark- able if it had no significance. The alloys represented by the following formulas would contain respectively — Cu^Al g.6i per cent, aluminium. CugAl 5.05 " CuieAl ••2.59 Cu,Al 7-i With regard to these bronzes, Morin* advances the following arguments to prove that they are true chemical combinations according to the formulas given : — 1. The alloy made by melting 10 parts of aluminium with 90 parts of copper is a very brittle mixture, which only takes on its best properties after two or three repeated fusions, during which the excess of aluminium above that called for by the formula is oxidized and separated out. When this point has been reached, further meltings do not alter the properties any more. 2. The addition of 5, 75^ and 10 per cent, of aluminium gives perfectly homogeneous alloys, but if 6, 7 or 8 per cent, is added, only metallic mixtures result, in which can be distin- guished uncombined aluminium. A point worthy of remark is that the color of the 5 and 10 per cent, bronzes is similar to gold, the latter giving a brighter shade; but the 7^ per cent, bronze is of a greenish cast, and has an entirely different ap- pearance from the other two. 3. When 10 per cent, of aluminium is added to molten cop- per, the large amount of heat absorbed by the aluminium cools the copper so much that almost all of it becomes solid. How- ever, as the whole becomes warmer, and the chilled part is * Genie Industriel, 1864, p. 167. 542 ALUMINIUM. stirred in that remaining melted, the mass gradually warms up as the copper combines with the aluminium, until towards the end the crucible is raised to a white heat by the heat set free within it. This phenomenon can only be explained on the basis of chemical action and combination between the two metals. 4. If a piece of aluminium bronze is heated nearly to its melting point and hammered at that temperature, it splits into fragments showing peculiar cleavage planes. These particles are evidently crystalline, and are smaller the nearer the temper- ature has been brought to the melting point. If they are ana- lyzed it will be found that they are all identical in composition with the mass, and that therefore no liquation or separation of any kind has taken place. If the bronze were a mere mixture, the temperature to which these pieces were heated would have caused the more easily fusible aluminium to sweat out. Almost all the arguments advanced to prove that the alumin- ium bronzes are true alloys are along these four lines discussed by Morin. A German pamphlet describes the 2j^, 5 and 10 per cent, bronzes as not being mixtures, like the alloys of cop- per and zinc, but perfect combinations of absolute homogeneity and uniform density, and not altered by remelting. When, how- ever, it is known that i per cent, or less of aluminium has a considerable influence on copper, it is almost begging the ques- tion to claim all the improvement to be due to the formationnof some alloy in atomic proportion something like Cu^oAl. It is certain that the first effect of adding the aluminium, and in the case of very small proportions the whole effect, is that the alu- minium acts as a deoxidizing agent, somewhat similar to the action of phosphorus in phosphorizing bronze. It reduces all dissolved oxides, combines with any occluded gases, and pro- tects the copper from oxidization during cooling. Thus a frac- tion of a per cent, of aluminium is of considerable benefit to brass and bronze, adding just before pouring. I have in mind the statement of an English metallurgist who reported that on adding i per cent, of aluminium to a not very pure copper he ALUMINIUM-COPPER ALLOYS. 543 was unable to find any aluminium on analyzing the resulting metal, but its properties were a great improvement on those of the original metal. In this case the aluminium was entirely slagged off. On adding the same quantity to pure copper it is certain that a larger part of the aluminium remains in the cop- per, as is shown by its color, but part of the improvement is undoubtedly due to the elimination of gases and traces of impurities. It is on the strength of these facts that some makers of pure aluminium have advanced the argument (directed against those makers producing bronzes directly) that the aluminium forms valuable bronzes principally by its action on the foreign sub- stances in the copper, and that therefore a really valuable alu- minium bronze can only be made by introducing pure alumin- ium into copper ; that it is wholly wrong practice to reduce an aluminium bronze of -high percentage to one of low percentage by adding fregh copper, since, although the bronze used may be of first quality, yet the already combined aluminium cannot produce any effect on the copper added, and the resulting bronze will be of inferior quality. The weak point in this argument is the last statement, that " the already combined aluminium cannot produce any effect on the copper added." We know that the aluminium and copper had previously com- bined with evolution of much heat, but there is reason to sup- pose that if subsequently a substance were brought into contact with this bronze which could be decomposed by aluminium with the evolution of much more heat than was set free in the formation of the bronze, the second reaction would take place. For instance, the reaction Al,4 3Cu,0-Al,03+3Cu, is very strongly exothermic, to the amount of something like 270,000 calories, and it is in a high degree probable that the heat of combination of this amount of aluminium with 9 times its weight of copper is not more than a small fraction of this amount. Therefore, the reaction . 2Cu,Al-l-3Cu,03=Al203+7Cu, 544 ALUMINIUM. which differs from the former one in involving the decomposi- tion of the bronze, Cu^Al, is still largely exothermic and there- fore liable to occur. To sum up, even considering that the heat developed in the formation of the copper aluminium alloy is very large, say even 3 or 4 times that of mercury combining with potassium, the largest so far measured experimentally, yet it would be so small in comparison with the heat developed by the reaction of the aluminium on the impurities present as to theoretically have very little effect in retarding that reaction. I would therefore conclude that the already combined aluminium would be very slightly less powerful than free aluminium in re- ducing and eliminating impurities in the copper, and the prac- tical effects would be identical. Further, it is clear that when a considerable percentage of alu- minium occurs in the bronze, only a part of its beneficial effect is due to the removal of impurities, a considerable effect being necessarily produced by the presence of the aluminium in the bronze. Therefore, even if the argument advanced as to the combined aluminium not being able to remove impurities were true, yet this can only be part of the function of the aluminium, and if the aluminium is really present, the results will be iden- tical in the two cases as far as the influence of the continued presence of the aluminium is concerned. Therefore, it may be safely concluded, that if the bronzes are made with copper of the same purity, the one made by diluting a good quality high-priced bronze with copper will be prac- tically as good as the one made directly from the metals. If it is true that the bronze placed on the market by those following the former method is not so good as that made from the metals directly, the reason is that the high per cent, bronze is not pure, due to the manner of its production. This is a defect in- herent in the first production of the alloy, and not chargeable to the subsequent inability of the aluminium to perform its function during dilution. The company producing bronzes by direct reduction have been understood to claim that since their alloy is made by cop- ALUMINIUM-COPPER ALLOYS. 545 per or copper vapor absorbing aluminium vapor, the result is a bronze far more homogeneous than is produced by melting the two metals together. This is partially true, since the metals in the latter case may not be kept molten long enough for com- plete combination to take place, and therefore would lack hom- ogeneity to a certain degree if not carefully made. This oppor- tunity for carelessness to enter into the question and affect the result does not occur in the reduction process, and the latter bronze would for this reason be at an advantage. But if the alloy is made carefully and with the precautions dictated by ex- perience in melting the metals together, there is no reason why the bronzes should differ. Two specimens containing nothing but aluminium and copper in like proportions will be identical, no matter how they are produced. Looking at the industrial side of the question, it is safe to say that users of bronze generally prefer to buy the constituent metals and make their own mixtures in whatever proportions their experience shows to be best for the kind of work they ex- ecute. Other things being equal, I think a bronze worker would prefer to purchase the metals, rather than buy the bronze ready-made, as in the former case he can always be sure of the composition of his alloy, and can profit by all those little variations in the manipulations and in the proportions of metals used which experience suggests, and which form so valuable a part of the successful metal-worker's art. Preparing the bronzes. — In making aluminium-copper alloys great attention must be paid to the quality of the copper used. Ordinary commercial copper may contain small amounts of an- timony, arsenic, or iron, which the aluminium can in no way remove, and which affect very injuriously the quality of the bronze. The aluminium bronzes seem to be extremely sensi- tive to the above metals, particularly to iron. This necessi- tates the employment of the very purest copper ; electrolytic is sometimes used when not too high priced, but Lake Superior is generally found satisfactory enough. Even the purest cop- per may contain dissolved cuprous oxide or occluded gases, 35 546 ALUMINIUM. and it is one of the functions of the aluminium to reduce these oxides and gases, forming slag which rises to the surface and leaving the bronze free from their influences. If tin occurs in the copper, it lowers very greatly the ductility and strength of the bronzes, but zinc is not so harmful. Care should also be taken as to the purity of the aluminium used, though its impurities are not so harmful as they would be if occurring in similar percentage in the copper, since so much more copper than aluminium is used in these alloys. Yet, the bronzes are so sensitive to the presence of iron that an alumin- ium with as small a percentage of this metal as possible should be used. The silicon in commercial aluminium is not so harm- ful as the iron, but it does harden the bronze considerably and increases its tensile strength. The purest aluminium alloyed with the purest copper always produces the highest quality of bronze. The " Magnesium und Aluminium Fabrik," of Hemelingen, gives the following directions for preparing the bronzes : " Melt the copper in a plumbago crucible and heat it somewhat hotter than its melting point. When quite fluid and the surface clean, sticks of aluminium of a suitable size are taken in tongs and pushed down under the surface, thus protecting the aluminium from oxidizing. The first effect is necessarily to chill the cop- per more or less in contact with the aluminium ; but if the cop- per was at a good heat to start with, the chilled part is speedily dissolved and the aluminium attacked. The chemical action of the aluminium is then shown by a rise in temperature which may even reach a white heat; considerable commotion may take place at first, but this gradually subsides. When the re- quired amount of aluminium has been introduced, the bronze is let alone for a few minutes and then well stirred, taking care not to rub or scrape the sides of the crucible. By the stirring, the slag, which commenced to rise even during the alloying, is brought almost entirely to the surface. The crucible is then taken out of the furnace, the slag removed from the surface with a skimmer, the melt again stirred to bring up what little ALUMINIUM-COPPER ALLOYS. 547 slag may still remain in it, and is then ready for casting. It is very injurious to leave it longer in the fire than is absolutely necessary; also, any flux is unnecessary, the bronze needing only to be covered with charcoal powder. The particular point to be attended to in melting these bronzes is to handle as quickly as possible when once melted." As with ordinary brass and bronze, two or three remeltings are needed before the combination of the metals appeajrs to be perfect and the bronze takes on its best quahties. When the alloy is thus made perfect, the bronze is not altered by remelt- ing, and the aluminium, which in the first instance removed the dissolved oxides and occluded gases from the copper, now pre- vents the copper from taking them up again and so keeps the bronze up to quality. If, however, the bronze is kept melted a long time, and subject to oxidizing influences, the tendency of the copper to absorb oxygen will cause some loss of aluminium by the action of the latter in removing the oxygen taken up, and a slag consisting principally of alumina will result; but if the remelting of the bronze is done quickly and the surface covered with charcoal or coke, the loss from this cause will be very trifling, and the percentage of aluminium will remain prac- tically constant. We have already discussed at length the dilution of a high per cent, bronze to a lower one. This operation is practised on a large scale by the companies which produce aluminium bronze directly in their reduction furnaces. I understand that they simply melt the high per cent, bronze in a crucible and stir into it pure copper in the required proportions, or else melt the two down together on the hearth of a reverberatory furnace. The combined aluminium thus cleanses the added copper and produces a lower bronze of right quality if the high-per cent, bronze used is pure and the copper added of the proper quality. It is, of course, quite certain that no difficulty can occur in adding aluminium to a low-per cent, bronze to in- crease its percentage, other than that of imperfect combination, which may be overcome by one or two remeltings. 548 ALUMINIUM. Fusibility. — The bronzes all melt easier than copper. Le- Verrier gives the following determinaticyis with the Le Chatelier pyrometer : Aluminium. Copper. Melting point, o loo 1054° C. 5 95 1030" 7.5 92.5 1000° 10. 90. 1029° These alloys all become slightly pasty below the melting point of copper until they have become thoroughly alloyed, showing that if not carefully prepared they contain free copper. When re-melted, this disappears, and the combination may be regarded as perfect. Casting. — Aluminium bronze is not an easy metal to cast per- fectly until the moulder is familiar with its peculiarities. The great enemies of steel castings, dissolved oxides and gases, form- ing blowholes, are here absent. As we have seen, the alumin- ium removes these impurities from the original copper, and by its presence afterwards keeps the bronze free from them. This difficulty, therefore, is not met in casting aluminium bronze, but the obstacles which afford the most trouble are the shrink- age in setting and contraction in cooling. These two factors are extraordinarily large, and must be met by provisions made in moulding, as shown later. A plumbago crucible, or one lined with magnesite (see p. 444), is the best to use for melting the bronze, the melt being kept covered with powdered charcoal. I would recommend that the stirrers and skimmers used be coated with a wash made of plumbago and a little fire-clay, as the contact of bronze with bare iron tools cannot but injure its quality. The crucible should not be kept in the fire any longer than is absolutely re- quired to bring the bronze to proper heat for casting. In cast- ing, it is of considerable advantage to use a casting ladle, into which the bronze is poured, which is arranged so as to tap from the bottom. This efifectually keeps any slag or scum from be- ing entangled in the casting. The same result is also obtained ALUMINIUM-COPPER ALLOYS. 549 by arranging a large basin on top of the pouring gate, which is temporarily closed by an iron or clay stopper. Enough bronze is then poured into this basin to fill the mould, and after the dirt is all well up to the surface the plug is withdrawn and the mould fills with clean metal. For very small work the ordinary skim- gate will answer the above purpose ; for large castings the tap- ping ladle is preferred. Plain castings, such as pump-rods, shafting, etc., and especially billets for rolling and drawing, are cast advantageously in iron moulds, which should be provided with a large sinking-head on top to feed the casting as it cools. Rubbing with a mixture of plumbago, kaoHn and oil is said to protect the iron moulds from sticking. The chilling makes the bronze soft, and the slabs and cylinders thus cast for rolHng and drawing are in good condition to be worked at once. For ordi- nary foundry castings, sand-moulds are used. The slower cool- ing makes the castings more or less hard ; if soft castings are wanted they can be subsequently annealed. Thomas D. West, the author of " American Foundry Prac- tice," read a paper on " Casting Aluminium Bronze and other Strong Metals," before the American Society of Mechanical Engineers, November, 1886, from which we make the following extracts : " The difficulties which beset the casting of aluminium bronze are in some respects similar to those which were encountered in perfecting methods for casting steel. There is much small work which can be successfully cast by methods used in the ordinary moulding of cast-iron, but in peculiarly proportioned and in large bronze castings other means and extra display of skill and judgment will be generally required. In strong metals there appears to be a " red shortness," or degree of temperatui-e after it becomes solidified, at which it may be torn apart if it meets a very little resistance to its contraction, and the separation may be such as cannot be detected by the eye, but will be made known only when pressure is put upon the cast- ing. To overcome this evil and to make allowances for sufficient freedom in contraction, much judgment will often be required. 550 ALUMINIUM. and different modes must be adopted to suit varying conditions. One factor often met with is that of the incompressibility of cores or parts forming the interior portion of castings, while another is the resistance which flanges, etc., upon an exterior surface oppose to freedom of contraction of the mass. The core must generally be ' rotten' and of a yielding character. This is obtained by using rosin in coarse sand, and filling the core as full of cinders and large vent-holes as possible, and by not using any core rods of iron. The rosin would cause the core when heated to become soft, and would make it very nearly as compressible as a ' green-sand' core when the pressure of the contraction of the metal would come upon it. " By means of dried rosin or green-sand cores we were able to meet almost any difficulties which might arise in ordinary work from the evils of contraction, so far as cores were con- cerned. For large cylinders or castings which might require large round cores which could be ' swept,' a hay-rope wound around a core barrel would often prove an excellent yielding backing, and allow freedom for contraction sufficient to insure no rents or invisible strain in the body of the casting. To pro- vide means for freedom in the contraction of exterior portions of castings, which may be supposed to offer resistance sufficient to cause an injury, different methods will have to be employed in almost every new form of such patterns. It may be that conditions will permit the mould to be of a sufficiently yielding character, and again it may be necessary to dig away portions of the mould or loosen bolts, etc., as soon as the liquid metal is thought to have solidified. In any metal there may be in- visible rents or strains left in a casting through tension when cooling, sufficient to make it fragile or crack of its own accord, and it is an element which from its very deceptive nature should command the closest attention of all interested in the manufacture of castings. " Like contraction, the element of shrinkage is often found seriously to impede the attaining of perfect castings from strong metals. In steel castings much labor has to be ex- ALUMINIUM-COPPER ALLOYS. SSI pended in providing risers sufficient to ' feed solid ' or prevent 'draw-holes' from being formed, and in casting aluminium bronze a similar necessity is found. The only way to insure against the evils of shrinkage in this metal was to have the ' risers ' larger than the body or part of the castings which they were intended to ' feed.' The feeder or riser being the largest body, it will, of course, remain fluid longer than the casting, and, as in cast-iron, that part which solidifies first will draw from the nearest uppermost fluid body, and thus leave holes in the part which remains longest fluid. The above principle will be seen to be effective in obtaining the end sought. It is to be remembered that it is not practical to ' churn ' this bronze, as is done with cast-iron. A long cast-iron roll, i foot in diameter, can by means of a feeder S inches in diameter and a y^ inch wrought-iron rod be made perfectly sound for its full length. To cast such a solid in bronze, the feeding head should be at least as large as the diamater of the roll, and the casting moulded about one-quarter longer than the length of roll de- sired. The extra length would contain the shrinkage hole, and when cut off a solid casting would be left. This is a plan often practised in the making of guns, etc., in cast-iron, and is done partly to insure against the inability of many moulders to feed solid, and to save that labor. A method which the writer found to work well in assisting to avoid shrinkage in ordinary castings in aluminium bronze was to ' gate ' a mould so that it could be filled or poured as quickly as possible, and to have the metal as dull as it would flow to warrant a full run casting. By this plan very disproportionate castings were made without feeders on the heavier parts, and upon which draw or shrinkage holes would surely have appeared had the metal been poured hot. " The metal works well in our ordinary moulding sands and • peels ' extra well. As a general thing, disproportionate cast- ings weighing over loo pounds are best made in 'dry' instead of ' green ' sand moulds, as such will permit of cleaner work and a duller pouring of the metal, for in this method there is SS2 ALUMINIUM. not that dampness which is given off from a green-sand mould and which is so liable to cause ' cold shots.' When the posi- tion of the casting work will permit, many forms which are pro- portionate in thickness can be well made in green-sand by coating the surface of the moulds and gates with ' silver lead ' or plumbago. "From 'blow-holes,' which are another characteristic ele- ment likely to exist in strong metals, it can be said that alu- minium bronze is free. Should any exist it is the fault of the moulder or his mould, as the metal itself runs in iron moulds as sound and close as gold. Sand moulds to procure good work must be well vented, and, if of ' dry-sand,' thoroughly open sand mixture should be used and well dried. The sand for • green-sand ' work is best fine, similar to what will work well for brass feastings. For 'dry-sand' work the mixture should be as open in nature as possible, and, for blacking the mould, use the same mixtures as are found to work well with cast-iron." In view of the above-recommended precautions, the reader recognizes at once the falsity of the statement in the pamphlet of a German manufacturer that " aluminium bronze shrinks almost none at all." I have, in fact, measured the contraction of a 5 per cent, bronze as y^ inch to the foot, just twice that of cast-iron. Such wild statements at a time when aluminium bronze is coming into such extended use, can only bring dis- credit on the firm making them. Color. — One per cent, of aluminium changes the color of cop- per considerably, making it like red brass. The influence of the aluminium is properly seen when two ingots, one of pure copper and the other of the bronze, are chilled from a high temperature, in which case the yellower color of the latter is plainly perceptible. If, however, the two ingots are let cool slowly in the air, the effect of the aluminium is more striking, since the copper oxidizes so as to turn quite black, while the bronze keeps as untarnished as if it had been chilled in water. Two and one-half per cent, of aluminium makes a bronze re- ALUMINIUM-COPPER ALLOYS. 553 sembling in color gold of low carat alloyed with copp^. The five per cent, bronze is pure yellow and the nearest approach to the color of pure gold of any known metal or alloy. The seven and one-half per cent, bronze has the color of the jewel- er's green gold. The ten per cent, bronze, or aluminium bronze proper, is a bright light-yellow, similar to the jeweler's pale gold. The eleven per cent, bronze is still paler. Fifteen per cent, makes a yellowish-white alloy which is too brittle to be of any practical use. Specific gravity. — The aluminium bronzes are not as much lighter than copper as the percentage of aluminium would indi- cate. If the specific gravity of a mixture of copper and alu- minium in the given proportions is calculated, it will be found uniformly lower than the observed specific gravities, showing the amount oi contraction in alloying to be large. This will account for the denseness and very close grain of these bronzes' The following table will set forth these data more plainly: — Contraction in alloying Percent, ef aluminium. Observed. Calculated. (percent.) 2y„ 8.60* 8.40 2.3 3 8.69 8.33 4.1 4 8.62 8.13 5.7 5 Specific GRAVITY. Observed. Calculated. 8.60* 8.40 8.69 8.33 8.62 8.13 /8-37 8.0 1 8.20* 8.0 S.oot 7.60 /7-69 I 7.56! 7-25 7-25 7-23t 7.10 4-4 \ 2.4 i 2.4 71^ S.oot 7.60 5.0 S 4- 1.8 :i} Hardness. — Accurate observations of the hardness of the alu- minium bronzes are wanting, with perhaps a single exception. It is known that the annealed metal, which has been chilled from a red heat, is much softer than that which has been al- lowed to cool very slowly. The metal which has been worked some time becomes almost as hard as steel. I think that the * According to Saarburger. t Cowles Bros.' alloys. The rest were given by Bell Bros. 554 ALUMINIUM. pure aluminium bronzes, when softened, are yet harder than all ordinary bronzes. The Cowles Company's bronzes almost invariably contain a small amount of silicon, which slightly increases the tensile strength, but is principally active in increasing the hardness of the bronze. For this reason, the following determinations, made on their alloys at the Washington Navy Yard, graded ac- cording to the government standard of hardness, must be con- sidered as maximum figures: — Metal. Hardness. Remarks. Average of gun-steel forgings, oil- tempered and annealed 21.4 Elongation 20 per cent. Same, not oil-tempered and annealed 14.9 " 18.7 " II pec cent, aluminium bronze, cast in sand 20.0 Elongation 4.5 per cent. Same, forged at low redness 18.0 " 5.2 " Same, rolled at red heat 21.2 " 6.5 " 7)'2 per cent, aluminium bronze, rolled hot 16.9 Elongation 30.0 per cent. Same, cast in chill moulds ■< •''^ •' ' t.li.8 " 26.1 " Government bronzes i 3-3 Elongation 1 2.5 per cent. t. 6.6 " 33.6 " Transverse strength. — The transverse strength or rigidity of aluminium bronze is one of its most noticeable qualities. Strange measured the amount of deflection in bars of aluminium bronze, gun-bronze, and ordinary yellow brass, laid on horizon- tal supports with the weight in the centre. From these exper- iments he concluded that the aluminium alloy was three times as rigid as gun-bronze and forty-four times as much so as ordinary brass. Compressive strength. — Mr. Anderson made a test of alumin- ium bronze for compressive strength in the Royal Gun Foundry at Woolwich. The piece taken had a height and diameter of 15 millimeters (tV inch). The results were as follows: ALUMINIUM- COPPER ALLOYS. SS5 Strain Applied. ' * N Shortening, Permanent set. Kilos per sq. mm. Lbs. per sq. in. per cent. per cent. 14-84 21,100 I.OI 0.17 96.42 I37.'40 (Specimen crushed.) It is seen from this test that the elastic limit for compression is comparatively low, but that the metal give's very slowly, as is shown by the large interval between this point and the ultimate crushing strength. According to two tests made at the Watertown Arsenal on Cowles' bronzes, their compressive strength was as follows : — 1 1 per cent, aluminium 160,400 lbs per sq. inch. 10 " aluminium 1 53,600 " " The test pieces being 2 inches long and 5^ inch in diameter, and cast specimens. The shortening up to the crushing point was 15 and 23.7 per cent, respectively. Tensile strength. — One of the first properties of the alumin- ium bronzes to draw attention to them was their great tensile strength. Since this property is attended by a large extensi- bility under strain, and a high elastic limit, we see that they are very valuable metals fqr engineering uses. For such uses, however, a metal costing $1.50 to $2 per . lb. was almost entirely out of question, and it is only recently that the lower "price has permitted placing the metal in situations where its great strength is of most use. Taking the various determinations chronologically, we have, first, those made by Lechatelier, in 1858. The alloy was cast in cylinders 10 millimetres (0.37 inch) in diameter, length of test pieces not given. The results were as follows : — Strength. Percentage of ' * ^ aluminium. Kilos per sq. m. m. Lbs. per sq. in. 10 58.36 83,000 10 55-35 78,720 8 33.18 47.190 5 32-20 45,800 S 31-43 44,700 French wrought-iron 35-00 49,780 5S6 ALUMINIUM. Deville determined the strength of aluminium bronze drawn into wire, compared with that of iron and steel wire of the same size (i mm. diameter=No. 19 B. W. G.), as — Kilos per sq. m. m. Lbs. per sq. in. Aluminium bronze 85 120,900 Best iron : 60 85,340 90 / 128,000 142,000 Steel { ,S { Experiments made in 1861,* on the relative strength of alu- minium bronze and the common metals gave — Aluminium bronze 19 Gun metal (copper 89, tin 1 1) 10 Drawn brass wire 8 Drawn copper wire 7 Tin bronze (copper 96, tin 4) 4 Same, with I per cent, aluminium 10 Same, with 2 " " l6 In 1862, Anderson tested the strength of aluminium bronze at the Woolwich Arsenal — testing pieces 3)^ inches long and 0.6 inch diameter, with the following results : — Lbs. per sq. in. Aluminium bronze 73,185 Gun metal 3S>ooo Hardest steel 1 18,000 Medium cast-steel 82,850 Steel from a Krupp cannon 74,670 The Cowles bronzes have been tested officially at the Water- town Arsenal and at the Washington Navy Yard, with especial reference to their comparison with the government bronzes. The Cowles alloys contain small variable quantities of silicon and the following content of aluminium : — Grade. Special "A" 11 per cent. A 10 " B 7>t " C- 5-S'A " D 2% " E iM " * Chemical News, v, p. 318. ALUMINIUM-COPPER ALLOYS. 557 Three tests of the " Special A" grade, made on the Water- town testing machine, gave the following results : — 1. Cast in sand Test pieces 2 inches long, 0.2 sq. inch area. 2. Forged hot (some flaws). " lo " 0.5 " " 3. Rolled hot " 2 " 0.2 " " 1. i. 3. Tensile strength (lbs. per sq. in,). 109,800 87,600 111,400 Elastic limit " « . 79,900 41,000 84,000 Total elongation (per cent.) o. 2. 6.5 Modulus of elasticity 17,240,000 15,625,000 The curve of number 3 is given on the diagram (Fig. 45) as A. Two tests of the "A" grade, on the same machine gave 5- Cast in sand. Test piece i inch long, 0.08 sq. inch area. 6. Forged hot. " 10 inches '' 0.25 " " 5. 0. Tensile strength (lbs. per sq. in.) 87,510 89,680 Elastic limit " " 50,000 Total elongation (per cent.) 17. 29.7 Modulus of elasticity 15,741,000 The curve of number 6 is marked B on the diagram. The test of a specimen of Cowles' bronzes of " A 3" grade, containing 8j4 per cent, of aluminium, made by Professor Un- win, F. R. S., gave Tensile strength 82,389 lbs. per sq. in. Elastic limit 39.738 " " Elongation 33-26 per cent. Test pieces 10 inches long and 0.2 sq. inch area. The B, C, D, and E grades decrease in tensile, transverse, torsional and . compressive strength, and in elastic limit in the order in which they are named, but the extensibility increases as the other properties decrease. Samples of Cowles' B and C grades, tested by Mr. Edw. D. Self, at the Stevens Institute, Hoboken, N. J., gave — B. C. Tensile strength ( lbs. per sq. in) S 1,680 40,845 Elongation (per cent) • • 4-' ' '-^ S58 ALUMINIUM. A sample of the D grade, tested on the manufacturers' ma- chine, gave a strength of 42,770 lbs., with 53 per cent, elonga- tion. Lbs.^er sq. in. Fig. 45. Kilos per sq. m.m. ..--._._ ___._._.___.__----- ' "r" :"j %20 000 ----------- ~ ~ ,-'-'--*- ^ '■• ^ ^^ - !:j5ll'!eus: :::::::::::::: I .' :: :::;;?'::::::::::::::::: y - — :z:'i:i---- -- ::::-::::::;-:: 90 000 l-f ^:i^H?:!^^^:^;r::i: = i=i--=: 00.000 1 rr T]lT\ 11 .XfflTI H L -rm / :^" — I' J-ril Toooo - 112 ::::::::::;:::: :::: J^Ll Jl 1 Al .Ml *11 L : I.:::::::::::::::::::::::::: : 2::::::::::::::::::::::::::: - Elongation — per cent. The bronzes made at Neuhausen by the Heroult process have been tested in Zurich with the following results : — ALUMINIUM-COPPER ALLOYS. 559 Grade. D H Tensile Strength. Per cent. Kilos per lbs. per Elongation, aluminium. sq. m.m. sq. in. per cent. 7 (35-9 49,200 25.4 ■ 38.7 5S,o6o 27-3 1% 38.4 S4,6oo 27.4 40.7 58,320 25-5 ' 36.4 51,760 34-3 8 i 45-° 64,000 45-7 (46.3 65.95° 48.4 8>^ 48.0 68,270 37-5 f 50.6 72,250 32.9 9 |si.6 73.380 39-2 r\\/ ( 52.2 74,240 23-5 9^ |s6.o 79,650 16.1 10 ] 5S-3 j 62.1 78,620 88,325 18.5 IO-5 I0I/2 f 59.0 83.915 12.0 j 64.0 91,000 6.3 Professor Tetmayer, under whose supervision the above tests were made, made a series of bronzes from the pure metals, for the express purpose of testing, and obtained the following results: — Tensile Strength. Per cent, of Elongation, aluminium. Kilos per sq. m.m. Lbs. per sq. in. per cent. 5K 44 62,580 64.0 »y2 50 71.II5 52.5 9 57-5 81,780 32. 9% 62 88,180 19. 10 64 91,000 II. II 68 96,720 I. ii>i 80 113.780 0.5 The annexed diagram (Fig. 46) shows by its curves the va- riation of tensile strength and elongation of the aluminium bronzes with the increasing percentage of aluminium, the curves Cand C being taken from Cowles' advertised guarantee (1889), the elongation being the minimum and the strength the average values guaranteed in castings ; H and H' represent the aver- age values given by Professor Tetmayer for bronzes made by the Heroult process ; T and T represent Tetmayer's determina- tions with bronzes made from the pure metals. 56o ALUMINIUM. Tensile strength, lbs. per sq. in. 130.0DB Fig. 46. . of aluminium. Le Chatelier has tested the resistance of 10 per cent, an- nealed bronze at different temperatures, with the following re- sults — Temperature. Tensile strength. Elongation C° Kilos per sq. m.m. Pounds per sq. in. per cent. 15 S3-2 76,000 19 100 52.4 74,800 22 150 51.0 72,800 21 200 49.2 70,200 22 250 47.0 67,000 21 300 44.2 63,000 19 350 37-0 52,800 15 400 23.2 33,000 21 45° 1 0.0 14,200 23 ALUMINIUM-COPPER ALLOYS. 561 These figures show that the bronze retains over three-quar- ters of its strength up to 300°, and show that it is admirably- adapted for replacing copper tubes in steam boilers and for steam pipes. Annealing and hardening. — Aluminium bronze acts like ordi- nary brass in these respects. It is softened by chilling; the best procedure is said to be to heat the articles to bright red- ness for some time, to destroy all crystalline structure, then cool in still air to full redness and plunge into cold water. The metal becomes very hard and stiff when worked for some time without annealing. To get the bronze to its maximum elasticity and hardness it must be cooled very slowly. Articles of bronze can be heated red-hot in charcoal powder and allowed to cool embedded in it. It is said that the bronze can be thus made elastic enough for the hair-springs of watches. Working. — Despite the assertions that aluminium bronze can be heated to bright redness and then hammered out until quite cold, yet it is not so easily worked. Persons who have had a large experience with the alloy say that it possesses peculiarities in working which must be learned and strictly attended to. As with many other alloys, there is a certain temperature at which it works perfectly, but this is contained within narrow limits. This heat is rather indefinitely stated as full-redness. At a lit- tle above this heat (bright-red) or at a little below (low-red) it works with much less ease. If it is rolled at this temperature, it does not become brittle by working. When the bronzes are worked cold they will quickly stiffen up, and will crush or spHt unless annealed frequently. Working increases the strength and rigidity, but diminishes the extensibility. As alu- minium bronze is such a strong metal, it is natural to expect that it would require a large amount of power to work it. This is the case, and accords with the fact that when Cowles Bros, first introduced their bronzes the workers of copper and ordi- nary bronze came very nearly breaking their rolls in endeavor- ing to work it; the steel workers, however, had no difficulty from this source. The Aluminium Brass and' Bronze Company, 36 S62 ALUMINIUM. who work up the Cowles bronzes, have put in rolls which are even more powerful than those used for working steel bil- lets of corresponding size. It is recommended to subject the billet at the first pass to the heaviest presure the rolls will give, in order to destroy at once any crystalline structure. When rolling cold, the lower grade bronzes can be worked for a longer time between annealings, but when rolling hot the higher bronzes give the least trouble. When drawing the bronzes, they are first cast into rods of small diameter, annealed and then drawn. Very hard dies are required, or the ordinary bronzes, especially the higher grades, are apt to become so hard between annealings as to cut them. The speed of drawing must be slow, and the reduction effected very gradually. In regard to forging aluminium bronze, the statement that it can be forged perfectly at all temperatures from bright red to cold does not coincide with the experience of many workers. At a cherry red, the suitable temperature for rolling, it hardly forges at all. A much lower temperature must be used, a low redness, and at that heat it forges perfectly. Metal hammered from this heat until it is cold has its strength much increased. Aluminium bronze can be spun, stamped, or pressed, like ordinary brass. In these operations it must be annealed after each successive treatment, since it hardens up so quickly under the great pressure. In working with the file it is noticeable that the aluminium bronzes do not clog the file. Before the chisel it gives long, clean chips. On the lathe and planing machine the tool takes off long elastic threads and leaves a fine surface. It is especi- ally in these cutting operations that the great advantages of a metal as strong as steel and yet as easy to work as brass be- come apparent. Simms states that aluminium bronze can be easily engraved, taking the sharp lines and deep cuts of the tool as well as any cast metal. Since it can be soldered, it forms a very suitable material for drawing into tubes. It is stated that it can even be hammered out into leaf, but this state- ment needs further proof. ALUMINIUM- COPPER ALLOYS. 563 Anti-friction qualities. — Along with the great toughness and malleability of aluminium bronze, as also its fine grain, we note a peculiar unctuousness or smoothness which seems to resist abrasion, and to render it one of the best anti-friction metals known. Morin held that to bring out the metal's best qualities it should not be used in castings, but as forged or rolled forms. He cites an instance where it was appHed to the bearings of a large lathe, the axle having a diameter of 60 millimetres and making up to 1800 revolutions per minute. A plate of alu- minium bronze was soldered in place on a common bearing metal back, and then carefully bored true. This bearing had been in use four years at the time of Morin's statement, and after 2^ years' working the wear was only 0.4 millimetre. Cowles Bros, recommend using the higher grades for bearings working under very heavy pressures, as their great strength prevents crushing, while the lower grades are more suitable for high speeds and low pressures. They recommend casting the bearings, bringing the working surface up to a high polish and using them only under steel axles. An incident occurring under the author's immediate notice may be more to the point than quotations from other sources. A smooth metallic ball was required for a rotary steam engine, to work between steel guides in such a position that almost all the work of the engine passed through it. Steel balls were impracticable because they cut the guides. All sorts of bronzes and anti-friction metals were tried, but a few hours' work would cut them out of shape. Mr. Joseph Richards sug- gested to the maker that an aluminium bronze ball be tried. A ball was cast of ten per cent, bronze, but the casting not be- ing solid it was warmed up and hammered until all the holes were closed. The ball was then turned smooth and polished. On putting into place it was worked several days at high speed without giving way, and on taking it out for examination the only sign of wear was that the polish was a little higher. I think that the hammering increased its capability of resistance, and would recommend that if the cast aluminium-bronze bear- 564 ALUMINIUM. ings do not meet any extra requirements put on them, the hammered or rolled metal might be successfully substituted." Conductivity. — The aluminium bronzes conduct heat and electricity better the lower the proportion of aluminium. Benoit measured the electrical conductivity of 10 per cent, bronze as 13, silver being lOO and copper 90. Edw. D. Self states that he found the heat conductivity of the 6 per cent, bronze almost the same as for pure copper, and that of the 10 per cent, bronze very little less. Resistance to corrosion. — Deville said, " In chemical proper- ties aluminium bronze cannot differ much from the other alloys of copper," yet from numerous experiments we have noticed that it does resist most chemical agents better, particularly sea-water and sulphuretted hydrogen. Bernard S. Proctor,* after describing thirty-one experiments comparing aluminium bronze and brass, sums up the conclu- sions as follows : — " From the above experiments it appears that aluminium bronze has a little advantage over ordinary brass in power to withstand corrosion, and its surface, when tarnished, is more easily cleaned. This should give it general preference where cost of material is not an important consideration, especially if strength, lightness and durability are at the same time desirable. It is out of my power to say anything about its fitness for deli- cate machinery, except that its chemical examination has re- vealed nothing which can detract from the preference its me- chanical superiority should give it. Being so much less acted on by ammonia and coal-gas suggests its suitability for chem- ical scales, weights, scoops, etc. Its resistance to the action of the weather and the ease with which tarnish is removed render it especially applicable for door-plates, bell-handles, etc. Its mechanical strength and chemical inactivity together recom- mend it for hinges exposed to the weather. In experiments 18, 22, etc., the tendency of brass to corrode on the edges and at any roughness on its surface will be observed, while the * Chem. News, 1861, vol. iv, p. 59. ALUMINIUM-COPPER ALLOYS. 565 bronze is free from this defect. In several cases the bronze seemed to be more quickly covered with a slight tarnish which did not increase perceptibly, probably the tarnish acting as a protection to the metal ; but the brass, though less rapidly dis- colored, continued to be corroded and apparently with in- creased speed as the action was continued. The bronze is more easily cleaned. For culinary vessels its superiority to metals now in use appears questionable." The author states that he wrote the article with a home-made pen of aluminium bronze, and suggests that it is well worthy of the attention of pen-makers. The Cowles Co. states in a pamphlet that salt-water, soap- water and urine have no effect on aluminium bronze, which would make it a very valuable metal for ship builders and sani- tary engineers. It is well known that the fatty acids, as in tal- low, corrode brass and bronze, as is seen in old fashioned brass candle-sticks, but aluminium bronze is said to be untouched by these agents. It is said that for preserving pans, in which fruit juices are boiled, aluminium bronze is superior in resisting power to the coppers now used. Sulphuretted hydrogen and coal-gas have hardly any effect on it. Hydrochloric acid dis- solves out the aluminium, nitric acid dissolves out the copper. Tissier Bros, remarked that the color of the bronzes containing from 5 to 10 per cent, of aluminium could thus be altered at will by leaving in dilute nitric or hydrochloric acid. Concen- trated sulphuric acid attacks it at first, but a coating is speedily formed which seems to protect the metal against further injury ; dilute sulphuric acid attacks the alloy more deeply. Hot soda solution slowly removes the aluminium near the surface, leav- ing a velvety coating of copper oxide. The acid of perspira- tion is quite active in attacking aluminium bronze superficially, as any one can test by noticing how quickly a polished surface is tarnished. I do not think, however, that the corrosion is any more marked than other bronzes would show, and the tar- nish is very easily removed and the polish restored by a little rubbing with a dry woolen cloth. 566 ALUMINIUM. In order to test the suitability of aluminium bronze for boats, the following experiments were made at Neuhausen. Sheets of the metals were kept for 40 hours in ( i ) a solution of 3 per cent, sodium chloride and 4 per cent, acetic acid, (2) in sea- water. The comparative losses were as follows : — I. II. 10 per cent. Bronze free from Silicon i i 10 per cent. Bronze with 2.89 per cent. Silicon 2 39 Brass with 3.59 per cent, of aluminium 4 loi Phosphor Bronze 32 116 When heated in the air, aluminium bronze remains unoxi- dized even if kept at a red heat for a long time. This is a re- markable property when contrasted with the behavior of brass wire, which would quickly turn to oxide. It is stated that it has been kept at a bright red heat for several months without showing any oxidation. As a chemist, who has in common with all other chemists been annoyed by the oxidation of brass wire when heated over a Bunsen burner, I hope that aluminium bronze wire gauze will soon be made for this purpose. When exposed to the weather, the tarnish formed is very superficial and protects the metal underneath from continued oxidation. The aluminium bronzes take on a darker hue, after some exposure, but they never turn black like ordinary bronzes, or green like brass. Since the color of out-door bronze statues is only preserved by a coat of lacquer, which hides many of the most artistic strokes, the value of a bronze which will stand the weather unprotected should be utilized by the art casters. It has been proposed to cast cannon of alu- minium bronze, and this incorrodibility gives it an advantage over all other bronzes for this purpose. A commission ap- pointed by the Austrian Government in t888, to report on various types of rifle barrels, tested, among other materials, aluminium bronze. Two rifles, one with a steel barrel the other of aluminium bronze, were left in the gutter on a roof for sev- eral weeks. On examining them, the steel gun was rusted so far as to be completely useless, while the bronze barrel was ALUMINIUM-COPPER ALLOYS. 567 only slightly tarnished and was loaded and fired without clean- ing and without accident. Uses of the aluminium bronzes. — The previous remarks have necessarily contained allusions to the many uses to which these bronzes may be advantageously applied. Their resemblance to gold early caused their use for jewelry, watch-chains, etc., but the ease with which their fine polish is tarnished by perspira- tion makes them unsuitable in this direction. Their wearing qualities make them valuable bearing metals, being also espec- ially applicable to parts of machinery subject to heaxy strain and rapid work, such as weavers' shuttles, ball-bearings, pin pivots, etc. It seems to be the great strength united with con- siderable malleability which gives these wonderful wearing qualities. The Engineering and Mining Journal * suggested that alu- minium bronze should make excellent battery, sizing and jig- screens for mining and ore working machinery. The Cowles Company soon afterwards placed milling screens of 5 per cent, bronze on the market, and they have given excellent satisfac- tion. Screens of this bronze lasted six months, while Russia- iron screens broke through in two weeks. The considerable resistance of aluminium bronze to chemical agents has suggested its use as a material for pumps and machinery subjected to the action of acid mine-water. It is said that the Worthington Company have used it in their high pressure mine-pumps. Mr. Strange.t an English engineer, made a thorough discus- sion of the suitability of aluminium bronze for the construction of astronomical and philosophical instruments, and concluded that it was superior not only in some, but in all respects to any metal hitherto used for that purpose. Mr. A. H. Cowles read a paper before the U. S. Naval Insti- tute, October 27, 1887, urging the merits of aluminium bronze ♦August, 1887. t Chemical News, vii., p. 220. 568 ALUMINIUM. as a metal for casting heavy guns. Reference was made to the casting of a mountain howitzer of this bronze in i860, which stood every test put upon it by the French artillery ofiScers, and which would have caused a revolution in cannon material but for the fact that its cost was prohibitory. The principal points made by Mr. Cowles are — i. The great strength and high elastic limit of aluminium bronze. 2. Its ductility. 3. The sound castings it produces. 4. The fact that no liqua- tion takes place during cooling, as in ordinary gun bronze. 5. No tendency to crystallization, as is the case with steel. 6. No rusting or corrosion. 7. Seventy per cent, of the cost of the gun is represented by the metal, which may be melted over when the gun is worn out. 8. Even with this high cost of metal, the total cost of the gun would be only four-fifths that of a built-up steel gun. While the discussion following the reading of this paper was not altogether in favor of the solid gun versus the built-up gun, yet no doubt was expressed that for casting solid guns aluminium bronze was undoubtedly the best metal that could be used, and as regards its comparison with built-up steel guns, the sum total of the discussion seemed to point to the expectancy that the bronze gun would be as good, if not better. But, as Deville was wont to say, " It is not necessary to theorize if you can make the experiment," and we hope soon to see a large aluminium-bronze cannon success- fully cast and its exact worth demonstrated. Aluminium bronze has been used very advantageously as a material for propeller blades. Its freedom from galvanic ac- tion, its non-corrosion by sea water, and its great strength, make it particularly well adapted for this use. Quite a long discus- sion on this subject was printed in London Engineering during April and May, 1888, raised principally by the makers of man- ganese bronze, but it was shown conclusively that in every point in which the latter was claimed to be of special advant- age, aluminium bronze was still more advantageous. The Web- ster Aluminium Co. cast a propeller for a vessel whose bottom was subjected to the destructive influence of tropical waters. ALUMINIUM -COPPER ALLOYS. 569 and it was used with the most satisfactory results as regards freedom from corrosion. I understand that several of the new U. S. gunboats have aluminium bronze propellers, since as speed is a great requisite, the lightening of the blades made possible by the use of a much stronger metal is of consider- able advantage. Besides the items mentioned, we might conclude by saying that if aluminium bronze were as cheap as brass or ordinary bronze, there is hardly a single use that can be mentioned for which it would not be preferred ; since it costs more than these, it will be used for all those purposes for which it is of partic- ular excellence, and its use will extend in a largely increasing proportion as its cost is lowered. Its specific gravity is not so much lower than ordinary brass or bronze as to cause its use on this account, but the fact that its superior strength allows a large decrease in weight without any less strength than with the other metals, will aid greatly in increasing its sphere of usefulness. The fact that it will not rust gives it always the advantage over steel in out-door uses, and the fact that it can be cast perfectly will cause it to replace complicated steel forgings. With aluminium bronze at the prices now made possible by the low prices of aluminium and copper, it should be able to drive all other strong bronzes out of the field. Brazing. — Aluminium bronze can be brazed easily at a red heat, using ordinary brazing solder (zinc i, copper i) and 3 parts of borax. Soldering. — Deville stated that aluminium bronze could be soldered with ordinary hard solder at a low red heat. It re- sists the common soft solders at ordinary temperatures, but if some zinc amalgam is added it can be soldered cold. Schlosser* gives the following directions for preparing this solder : White solder is alloyed with zinc amalgam in the pro- portions White solder 248 Zinc amalgam r ' ' ' *Das L5then, p. 180. 570 ALUMINIUM. The white solder may be composed as follows: — Brass 40 22 18 Zinc 2 2 12 Tin 8 4 30 The zinc amalgam is made by melting 2 parts of zinc, adding I part of mercury, stirring briskly and cooling the amalgam quickly. It forms a silver white, very brittle alloy. The white solder is first melted, the finely powdered zinc amalgam added and the alloy stirred until uniform and poured into bars. The Cowles Co. recommend the following solders as effective and convenient for aluminium bronze jewelry: — Hard solder for 10 per cent bronze — ■ Gold 88.88 Silver 4.68 Copper 6.44 Middling hard solder for 10 per cent, bronze — Gold 54.40 Silver 27.00 Copper 18.00 Soft solder for Al bronze — Copper 70 per cent. I -^ Tin 30 " [Bronze 14.30 Gold 14.30 Silver 57-10 Copper 14-30 The aluminium bronzes can be easily brazed, using borax or borax and cryolite as a flux. A cheap bronzing solder is an alloy of equal parts of zinc and copper, or 46 parts zinc, 52 copper and 2 tin. Butt and lapped joints made in this way are from one-half to one-third as strong as the bronze itself, and stand hammering or rolling. Silicon-aluminium bronze. — Cowles Bros, have, by reduciffg fire-clay in presence of copper, obtained alloys of aluminium, silicon and copper. This alloy is white and brittle jf it contains , ALUMINIUM-COPPER ALLOYS. 57 1 over 10 per cent, of aluminium and silicon together. With from 2 to 6 per cent, of these in equal proportions, the alloy is stronger than gun metal, is very tough, does not oxidize when heated in the air, and has a fine color. With 10 per cent, of aluminium and 2 or 3 per cent, of silicon, Cowles Bros, claim to have produced one of the strongest metals known. Phosphor-aluminium bronze. — Thos. Shaw, of Newark, N.J.,* patents a phosphor-aluminium bronze, making the following claims : First, an alloy of copper, aluminium and phosphorus, containing 0.33 to 5 per cent, of aluminium, 0.05 to i per cent, of phosphorus, and the remainder copper. Second, its manu- facture by melting a bath of copper, adding to it aluminium in the proportions stated, the bath being covered with a layer of palm oil to prevent oxidation, and then adding a small propor- tion of phosphorus. It has been stated that thfs alloy has a high conductivity (pre- sumably for electricity), but I am unable to find any determi- nations or evidence of any kind to substantiate this statement. Boron-aluminium bronze. H. N. Warren, of Liverpool, Eng- land, produces first alloys of aluminium with boron (see p. 498). These crystalline, brittle alloys are then dissolved in copper to the extent of 5 or ID per cent. The bronze produced is described as melting sharply, casting well, and showing no signs of liqua- tion. No information has been given as to its mechanical properties. * U. S. Patent, 303,236, Aug., 1884. CHAPTER XVI. ALUMINIUM-IRON ALLOYS. Although aluminium does not appear to combine as ener- getically with iron as with copper, yet the affinity between these two metals is sufficient to cause their combination in all proportions. The useful alloys, however, are confined to those containing a small amount of aluminium, the addition of small quantities of iron to aluminium producing no useful result. Iron is one of the most obstinate impurities in commercial aluminium. About the only way to obtain aluminium free from iron is to keep the materials from which it is made scrupulously free from that metal, since if it once gets into the aluminium, it is almost impossible to remove it. As to its exact influence on the properties of aluminium, when in small quantities, we may say that it renders the color more of a gray, the aluminium becomes harder, less malleable, and appears to crystallize more readily. The most noticeable effect, however, is on the fusi- bility. Tissier Bros, observed, somewhere about 1857, that aluminium free from iron could be melted on a plate of alu- minium containing 4 to 5 per cent, of that metal. Deville also observed that if a large amount of iron was present (10 per cent.), the aluminium could be liquated by careful heating, a ferruginous skeleton remaining, while aluminium containing less iron flowed away. This process, however, could not be used for the ultimate purification of commercial aluminium, since when the percentage of iron is low no liquation takes place. The exact rise in the melting point due to the presence of iron has been recently determined by Prof. Carnelly. He found that a specimen of aluminium containing 0.5 per cent, of iron melted very close to 70o°C., whereas a specimen containing 5 (572) ALUMINIUM-IRON ALLOYS. 573 per cent, of iron did not even soften at that temperature, but commenced to fuse at about 730°.* The effect of the iron is particularly seen in rendering the fusion pasty. Since silicon acts in an almost similar manner, it is important to observe that commercial aluminium can contain a certain small quantity of iron with very little detriment only on condition that the amount of silicon present is small. Tissier Bros, took pure aluminium in small pieces, mixed it with bits of pure iron wire, and melted in a crucible under common salt. The alloy with 5 per cent, of iron thus made was harder, more brittle, and less fusible than pure aluminium. The alloy with 7 per cent, of iron differed from the preceding principally in showing a stronger tendency to crystallize. With 8 per cent, of iron the alloy crystallized in long needles. Deville states that the alloy containing 10 per cent, of iron has the color and brittleness of native antimony sulphide (stibnite). By melting together 10 parts of aluminium, 5 parts of ferric chloride, and 10 parts each of potassium and sodium chlorides, Michel obtained a crystalline mass, which by careful treatment with very dilute hydrochloric acid left some six-sided crystals, having the color of iron, and agreeing nearly to the formula AljFe, containing 51 per cent, of iron.f These crystals dis- solved easily in hydrochloric acid ; caustic soda dissolved out the aluminium. Calvert and Johnson obtained the alloy AljFcj (see p. 420), containing on analysis 24.55 P^*" cent, of alumin- ium — the formula calling for 24.34 per cent. Globules of this alloy were white, did not rust in moist air, and when treated with weak sulphuric acid gave up the iron, while the aluminium remained as a skeleton, having the shape of the original button. These experimenters also obtained an alloy containing, in two different experiments, 12.00 and 12.09 P^'' cent, of aluminium. The formula AlFe,, requires 10.76 per cent. This alloy was extremely hard, and rusted on exposure to the air ; but could be forged and welded. * These temperatures are both too high, which does not, however, affect the com- parison. f Ann. der Chemie und Pharm., 1 1 J, 102. 574 ALUMINIUM. The iron-aluminium alloy which is being largely used at present for introducing aluminium into iron and steel is gen- erally made with 5 to 15 per cent, of aluminium and has re- ceived the trade name of "ferro-aluminium." Several different makes of this alloy are on the market, some made directly from alumina, others made by adding aluminium to iron. An analysis of Cowles Company's ferro-aluminium has already been given. The grade mostly supplied by this company averages 6 to 9 per cent, of aluminium, with 2^ to 3 J^ per cent, of silicon, and about 3 per cent, of carbon. When ferro-aluminium is made by alloying aluminium with iron, a good quality of pig- iron is chosen, and when melted the aluminium, in bars, is seized in tongs and dipped under the surface. A rise of tem- perature occurs, and a noticeable separation of graphitic car- bon, causing " kish" to collect on the surface. It is said that the pig-iron thus alloyed has its combined carbon almost en- tirely converted into free carbon, losing sometimes as much as 2^ per cent, in weight thereby. When all the aluminium re- quired has been added, the melt is stirred, the crucible remain- ing in the furnace ; then it is let stand for a few minutes, taken out of the fire, skimmed clean and cast into slabs or bars. These alloys (ferro-aluminiums) are very hard, brittle, easily broken, and yellowish-white in- color. Ledebuhr states that as the percentage of aluminium increases the iron becomes less magnetic, and at 17 per cent, the alloy is non-magnetic. It is said that in the works where the alloy is being made a workman can, after a few practices, grade the alloys roughly by a sim- ple magnetic test, even some degree of accuracy being finally attainable. Since wrought-iron and steel are very sensitive to small amounts of impurities, it is important that the ferro-alu- minium added to them should be as pure as possible, being made from the purest pig-iron ; this condition is of less im- portance when operating on cast-iron. This has led to the manufacture of two grades of ferro-aluminium, one for ordinary foundry use, the other for steel and mitis-castings. Pig-irons and commercial iron and steel do not take up any ALUMINIUM-IRON ALLOYS. 57$, appreciable quantity of aluminium in the process. of their manu- facture. Blair states that he finds aluminium nearly always present as such in steels, but only in quantities of a few thous- andths of a per cent, such as, from actual analyses, 0.026, 0.029, 0-034 per cent. Corbin reported 2.38 per cent, in chrome steel, but Blair finds chrome steel to contain no more aluminium than other steels. Aluminium is very seldom re- ported even in the smallest amount in wrought-iron, since the puddHng process may be reasonably expected to eliminate al- most entirely any that might be in the pig-iron. Conflicting views have been expressed as to the presence of aluminium in pig-iron, As much as i per cent, has been reported in Ger- man gray-iron ; Griiner states that some English pig-irons con- tain 0.5 to I per cent., and some Swedish irons 0.75 per cent. Percy quotes an analysis of pig-iron showing 0.97 per cent, of aluminium, but questions its correctness, supposing that much of this might have come from aluminium contained in included slag. The Marshall furnace, at Newport, Pa., has produced iron containing as much as 0.9 per cent, of aluminium, working with a slag carrying 25 per cent, of alumina. (See p. 428.) Faraday and Stodart obtained an alloy containing 3.41 per cent, of aluminium by melting an iron carbide with alumina at a very high heat. This alloy is described as being white, close- grained and very brittle. G. H. Billings (see p. 424) made an alloy containing 0.52 per cent, of aluminium and 0.2 per cent, of carbon. Its fracture showed solid, homogeneous and finely crystalline, like steel with i per cent, of carbon. It forged very well at cherry redness, but crumbled to fragments at a yellow heat; it would not harden. As the principal use of aluminium in iron is as a refining agent, we will sub-divide the remainder of this chapter into three parts ; namely, the effect of small quantities of aluminium on (i) steel, (2) wrought-iron, (3) cast-iron. Effect of Aluminium on Steel. Although A. A. Blair found aluminium almost always present 576 ALUMINIUM. in steel as a few thousandths of a per cent., yet he was not able to determine that so small a quantity had any appreciable effect on the properties of the metal. Faraday, in seeking for the distinguishing ingredient of the famous Bombay Wootz-steel, found that it always contained alu-- minium in quantities varying from 0.0128 to 0.0695 psr cent. In order, then, to prove the case synthetically, Faraday and Stodart took an alloy of iron with 3.41 per cent, of aluminium and a little carbon, and melted it in various proportions with steel. On melting 40 parts of the alloy with 700 of good steel (introducing 0.18 per cent, of aluminium), a malleable button was obtained, which on treatment with acid on a polished sur- face gave the beautiful damask peculiar to Wootz. On melting 67 parts of alloy with 500 steel (introducing 0.4 per cent, of aluminium) the resulting button forged well, gave the damask, and " had all the appreciable characteristics of the best Bombay Wootz." Karsten could not find any aluminium in specimens of Wootz which he examined, and suggested that that found by Faraday was due to intermingled slag; but the latter found aluminium in the steel without silica, which seems to prove that his results are beyond question. Rogers* corroborated the above results obtained by Faraday. He melted an iron-aluminium alloy with steel in quantity suf- ficient to introduce 0.8 per cent, of aluminium. The product had great hardness, a bright silver-like polish, and when treated with dilute acid acid gave the undulating markings peculiar to Damascus steel and Wootz. With aluminium costing $12 to $16 per lb. it can be readily seen that this use could not be practiced commercially ; but, with aluminium at less than half that price, and especially with even more economical ferro-aluminium to be had, these old references were looked up, and many steel-makers began try- ing the virtues of aluminium. Since 1885 hardly a maker of crucible steel and steel castings but has made some experi- * Moniteur Industrie!, 1859, p. 2379. ALUMINIUM-IRON ALLOYS. 577 mehts in this line. It had long been known that if alumina is added during the melting of steel in a crucible, the grain and lustre are improved. It was found that ferro-aluminium, added just before pouring, had the same efifect ; and since the latter operation is under exact control, it is preferred to the former practice, providing that the ferro-aluminium can be obtained pure enough for this use. From experiments made at Faustman & Ostberg's Mitis Foundry at Carlsvick, Sweden, in 1885, it was proved that ferro- aluminium is of great use in making steel castings, and the pro- cess was patented by Wittenstrom.* Wrought-iron scrap, was melted in crucibles, carbonized to hard steel by adding pure pig-iron, and before pouring, ferro-aluminium added to supply 0.1 per cent, of aluminium. The steel was then cast into the shape of ordinary edge-tools, which needed only to be hardened and ground in order to be ready for use. The surface of these tools was very clean and took a high polish. It was found that manganese, which is so often purposely introduced into steel, was deleterious in its action on steel containing aluminium, and that mild steel almost free from manganese gave by far the best results when aluminium was added. If true, this is a curi- ous fact which it is not easy to see the cause of. In Bessemer practice it is evidently of no use to add ferro-aluminium before blowing, but it has been thrown into the converter just before tipping into the ladle, and Mr. Ostberg states that Bessemer ingots containing only 0.06 per cent, of carbon have been thus made which did not rise in the mould at all, and were solid and of good quality throughout. SimHar advantages should also result on treating Siemens-Martin steel in this way, and perhaps even greater advantages, since mild steels are so much more dif- ficult to cast solid than high-carbon steel. At present aluminium is in general use among steel-casters. Some add it in the crucible or furnace,, others put it into the ladle or runner, while others even drop it into the main pour^ *U. S. Patent, 333,373; Dec. 29, 1885, English Patent, 8,269; Ny 3. -1885. ,; 37 5/8 ALUMINIUM. ing gate of the mould and pour the steel onto it. The latter method of procedure has been found by far the most econom- ical, and even superior in efficiency. The Phoenix Iron Company of Germany report that 0.2 per cent, of aluminium added (as ferro-aluminium) to their basic Siemiens-Martin steel gave them a metal with a tensile strength of 112,000 pounds per square inch, with 12.5 per cent, elonga- tion, whereas the best results previously attained were never over 100,000 pounds. Swedish works have found that an addi- tion of 0.02 to 0.025 per cent, to a Bessemer steel with 0.9 per cent, of carbon, ensures good castings ; in Martin steel of 0.65 per cent, carbon, o.oi per cent., put into the gate of the moulds, ensures dense ingots. In the latter steel, when casting ingots of 400 kilos weight, containing 0.15 per cent, of carbon, and using no aluminium, a zone of blow-holes was formed about S centimetres from the sides of the ingot; using 0.02 per cent, of aluminium, superficial blows appeared in such quantities as to make the ingot unsalable ; with 0.04 per cent, the ingot was free from blow-holes and almost faultless. In general, low carbon steel requires more aluminium to give sound castings than high carbon metal, Bessemer more than Siemens-Martin steel, and in any case more aluminium is required when it is added to the metal in the ladle than when dropped in small pieces into the flask during the pouring. The Swiss makers of aluminium, who should be naturally interested in selling as much aluminium as possible, recommend for steel the addition of only 0.004 to 0.025 P^r cent. ; for carbonless iron 0.01 to O.i per cent., the latter being sufficient to quiet overblown iron which is " wild" in the ladle. It is also important not to add too much aluminium to steel, because of the excessive shrinkage any excess causes. In high carbon steel, any considerable amount of aluminium left over also decreases its strength by separating out some of the com- bined carbon as graphite. It is therefore sometimes good policy to add a little less aluminium than is necessary to com- pletely eliminate the blow-holes, preferring to have a few of ALUMINIUM-IRON ALLOYS. 579 these left than to have a large shrinkage cavity. Ingots of alu- minium-steel have been made, at a time when its use was not properly understood, which contained a "shrink" clear to the bot- tom of the ingot. It was hoped that perhaps the use of alu- minium as a deoxidizer would render manganese unnecessary. P. A. Gilchrist investigated this point, and found that with alu- minium alone the steel is red-short, so that while the manga- nese is less necessary, it is not rendered superfluous. An interesting effect of the addition of aluminium to soft steel is the increased ease of welding. Specimens have been shown by the Cowles Syndicate Co., in England, of iron welded to Siemens-Martin steel with and without aluminium. With the ordinary steel the line of weld was clearly visible, but with steel containing 0.2 per cent, of aluminium no such line could be seen, the crystalline structure of the iron appearing to merge gradually into the fine grain of the steel, even under the micro- scope. We shall see later that the addition of aluminium to cast- iron tends to separate combined carbon as graphite. This probably accounts for the poor results obtained by adding ferro-aluminium to high carbon steels ; for these, melting more easily and fluidly than mild steels, would be made less fusible by the decrease in combined carbon and possibly also made pasty by graphite being entangled in the metal as it thickens. As illustrative of this point we will quote the experiments made by R. W. Davenport.* A large charge of carbonless ingot iron holding about 0.08 per cent, carbon, and boiling strongly, was tapped into two similar ladles and ferro-manganese added in order to convert it into a low-carbon steel. Into one ladle was put, in addition, ferro-aluminium sufficient to introduce 0.064 per cent, of aluminium. Both ladles were then teemed into sand castings and ingot moulds. The steel treated with ferro-aluminium lay perfectly dead and piped in the ingot moulds, and yielded practically solid sand castings ; the other * Howe's Metallurgy of Steel. S8o ALUMINIUM. rose in the moulds, had to be stoppered, and gave very porous sand castings. On another occasion, ferro-aluminium sufficient to introduce 0.04 per cent, of aluminium and O.IO per cent, of silicon was added to molten crucible steel, which owing to the presence of carbon and manganese evolved no important quan- tity of gas. This steel contained 0.25 per cent, of carbon. The result of adding the aluminium was to stiffen this steel, make it hard to pour and difficult to get solid castings. Mr. J. W. Spencer,* of the Newbern Steel Works, Newcastle- on-Tyne, made a series of tests on this subject of the effect of aluminium on crucible steel, and reached a similar conclusion. With a low carbon steel, the effect on the tensile strength in- creased with the increase of aluminium, but it was found on an- alysis that the amount of silicon in the metal was also increased by the treatment, which may partly account for the difference in strength. The following table shows these results : — Carbon Aluminium Silicon in steel. added. present. Elastic limit. Tensile strength. (per cent.) (per cent.) (per cent.) (tons . per sq. in.) (tons per sq. in.) O.IO 0.12 0.06 9.8 20.8 0-15 0.22 0.08 10.2 21.8 0.28 043 0.22 12.0 2S-S These three steels were described as " fluid, sound and tough," excepting the last which was brittle before annealing. They were all stronger before annealing. With high carbon steels most of these properties were reversed, as is seen by the follow- ing results : Carbon Aluminium Silicon in steel. added. present. Elastic limit. Tensile strength. (per cent.) (per cent.) (per cent.) (tons per sq. in.) (tons per sq. in.) 0.53 0.12 0.28 14.38 29.60 0.65 0.22 0.28 14.38 26.28 0.8s 0-43 0.40 15.80 21.87 In these cases, as in the previous ones, the increase in carbon and particularly silicon would cause a corresponding increase in * Iron Age, Dec. 22, 1887. ALUMINIUM-IRON ALLOYS. S8l tensile strength; but it is very noticeable that with' carbon over 0.5 per cent, the strength decreases with the increase of alumin- ium, in spite of a simultaneous increase in both carbon and sili- con. These steels are also described as fluid and running into sound castings, but they are brittle and hard before annealing, particularly the one containing most aluminium. Mr. Spencer sums up his experience as follows : " The result is satisfactory in every instance so far as soundness and the usual attributes of good castings are concerned, running fluid and without ebulli- tion into sharp, clear castings ; the milder mixtures, under the hammer, breaking very strong, though unannealed. The gen- eral conclusion from the mechanical tests is that though alu- minium may increase the elastic limit and tensile strength slightly, yet this is done at the expense of ductility, while in presence of high carbon it is disadvantageous in all these re- spects. It is also probable that the increase of elastic limit and tensile strength, when it does occur, is not more than can be accounted for by the carbon and silicon present. The chemi- cal reactions of the aluminium in the crucible may be various, but the prevention of blow-holes and increased fluidity are the chief advantages." In order to avoid introducing impurities into steel by using ferro-aluminium made from ordinary pig-iron, a German firm put on the market a steel-aluminium " containing lo per cent, of aluminium and 90 per cent, of pure cast-steel." This can of course be used instead of ferro-aluminium for any purpose, but it is particularly preferable in treating steel, which is so extremely sensitive to minute quantities of certain impuri- ties — sulphur, phosphorus, etc. The rationale of the action of aluminium in preventing blow- holes and increasing the fluidity of the metal will be discussed more at length in considering the action of aluminium in the mitis process, a little further on. Effect of Aluminium on Wrought-Iron. When wrought-iron is heated to a high temperature, it does 582 ALUMINIUM. not pass quickly into the fluid state, but for a large increase of temperature above the point at which it first softens it will re- main thick or mushy. At a very high temperature it can be made sufficiently fluid to pour into moulds, but the castings thus made are notably unsound and weak. It was discovered by Mr. Wittenstroem, of Stockholm, working with the co-ope- ration of Mr. L. Nobel, of St. Petersburg, that if a small amount of aluminium is added to a charge of wrought-iron which has been heated until pasty, the iron immediately liquefies and can be poured into castings having all the properties of wrought-iron except fibre, and as sound as if of cast-iron. This idea was investigated thoroughly at Nordenfelt's mallea- ble-iron foundry, in Carlsvick, Sweden, by Messrs. Witten- stroem, Nordenfelt, Faustman and Ostberg. The result of two years' experimenting during 1883 and 1884 was so successful that the malleable-iron plant was pulled down and a new foundry, operated by Faustman and Ostberg, supplied their former trade with wrought-iron castings, which were called "Mitis" castings by Mr. Nordenfelt, because of their softness in contrast with cast-iron castings. This plant began operations in January, 1885, and its product soon reached a larger sale than that of the malleable castings which it had supplanted. Mr. Ludwig Nobel also installed the process in his foundry at St. Petersburg at about the same time. The process was rep- resented by a fine display at the International Inventions Exhi- bition in London, in 1885, and received a gold medal. In 1885, Mr. Ostberg visited the United States for the purpose of establishing the process here,* and a plant was erected and put in operation at Worcester, Mass. In February, 1886, Mr. Ost- berg spoke before the Institute of Mining Engineers at their Pittsburg meeting, showing specimens of the castings ; an ex- perienced iron worker said on that occasion that he would not have believed the statements if they had not been proved by the sight of the castings. In the same month, the "United * U. S. Patent, 333.373; Dec. 29, 1885. ALUMINIUM-IRON ALLOYS. 583 States Mitis Company" was incorporated in New Jersey, W. F. Durfee, M. E., of New York, being general manager, Mr. Robt. H. Sayre, of Bethlehem, Pa., president, and the list of directors including Mr. John Fritz, manager of the Bethlehem Iron Works, and several other well-kaown gentlemen. The object of this company, which owns the " Mitis " patents for the United States, is to regulate the use and sell rights to work under these patents ; and it is said that five plants are now in operation in the United States. Abroad, plants are working in England, France, Germany, Austria, Sweden and Russia, The experimental plant started at Worcester, Mass., has been aban- doned for some time, it being said that the success achieved there was anything but briUiant ; but since the process does suc- ceed in other places, the plant in question was probably closed for reasons satisfactory to those concerned.. Such, in brief, has been the rise of the mitis process. It seems to have found its sphere in replacing malleable iron cast- ings, because principally of the superior toughness of mitis metal, although the castings are not so uniformly sound and trustworthy, nor hardly so cheap, as those of malleable iron. The following details of the production of mitis castings are from descriptions by Nordenfelt, Ostberg, and E. A. Cowper, of London : — Raw material. — As the raw material to operate on, wrought- iron scrap or mild steel are equally suitable. It was found that some of the best results are to be obtained by using Swedish scrap-iron or English hematite-iron — that is, materials contain- ing less than o.i per cent of phosphorus, which is a very injuri- ous ingredient if present in much larger quantity. Using a mixture with poorer quality iron, with phosphorus running up to 0.15 per cent., good results may still be obtained, that is, the castings still compare favorably with ordinary malleable castings. In using scrap steel, which is necessarily low in phosphorus, it was found that manganese interfered with the production of good castings, a result rather unexpected. Since almost every melter devises various mixtures of his own, as circumstances 584 ALUMINIUM. permit, it is but natural that we find the best features of the mitis process united with some other old-estabUshed practices. Thus, in one mitis plant in this country the mixture for melt- ing was composed of: Mitis scrap 35 per cent. Hematite muck bar 35 " Wrought iron punchings 12% " Soft steel scrap (o.i per cent, carbon) 12% " White pig-iron 3 " Ferro-silicon (10 per cent, silicon) i " ferro -aluminium (6 per cent, aluminium) ; % " It is seen that in this charge the melter used a little white iron as a flux, which would probably introduce O.i per cent, of car- bon ; then the virtues of ferro-silicon for making sounder cast- ings are utilized by adding o.i percent, of silicon to the charge; lastly, 0.04 per cent, of aluminium was introduced. In general, it may be said that if iron free from impurities is used, very good castings are obtained ; if iron is used with a large percentage of phosphorus, proportionately brittle and unsatis- factory castings result. The ferro-aluminium used should be, for similar reasons, fi^ee from any considerable amount of such impurities as generally injure wrought-iron. Since the castings are almost identical in composition with the charge of iron melted, the following analyses of mitis metal, made by Mr. Edward Riley, will show the range of material or mixture to which the process has been successively applied: — Raw material. Carbon. Hematite bar 0.067 Swedish scrap 0'053 Refined iron 0.130 'I ... 0.130 J^ Swedish scrap %( Staffordshire iron I ^^ > ••■ 0.070 0.093 Silicon, O.161 Phosphorus^ 0.068 Manganese. 0.022 0.044 0.124 0.077 0-I37 0.027 0.014 0.035 0.150 0.026 0.194 0.014 j^ Hematite bar Stafiordshire iron 0.106 0.080 0.250 0.014 The above figures are percentages ; sulphur was present in all ALUMINIUM-IRON ALLOYS. 585 as a trace. The first in the table, those low in phosphorus, gave the best castings, the last the poorest ; with over ^ per cent, of phosphorus, the castings were brittle. As already stated in considering steel castings, mixtures containing higher percentages of carbon had been treated, but there seems to be a limit to the increase of this element, above which the addition of aluminium is no longer helpful, but even deleterious. Method of treatment. — The charge of wrought-iron is placed in covered crucibles and brought to a temperature of about 2200° (Mr. Ostberg), at which heat it is just losing the solid and assuming the pasty condition. If it were desired to cast the iron without adding aluminium, it would be necessary to superheat it several hundred degrees above this point, not only to give it the desired fluidity, but also to permit it being carried around the casting shop. It is during this superheating that a large part of the. gases contained in the molten iron are ab- sorbed. If, therefore, the charge is treated with aluminium immediately on reaching the melting point, the efTect is such that this superheating with its accompanying deterioration of the iron is rendered unnecessary. This is possible for the reason that on adding ferro-aluminium sufficient to introduce 0.05 to o. I per cent, of aluminium, the charge immediately li- quefies, and is so far from its setting point that it can be re- moved from the furnace and poured into numerous moulds, re- taining all the time its exceptional fluidity. The metal acts just as if it had been superheated several hundred degrees, but this has been accomplished without leaving it in the furnace for half an hour or so, thus attaining an economy in fuel which is not to be ignored. When the crucible is taken from the fur- nace the charge is perfectly dead melted, lies quiet in the cruci- ble, exolves no gas and teems like molten silver. It is cast in either sand or iron moulds, and on account of its fluidity does not require large heads to bring the castings up sharp and show the finest impressions of the mould. Several devices are used in connection with this process which it may be interesting to note. The furnace used is one 586 ALUMINIUM. designed and patened by Mr. Noble, and burns naphtha or crude petroleum or petroleum residues. A full description with draw- ings may be seen in Engineering and Mining Journal, May 8, 1886. With this furnace are melted on an average 8 heats in 10 hours. Starting cold, the first charges are melted in i^ hours ; when the furnace is fully up to heat only ^ hour is nec- essary, so that the furnace is equal to 24 heats in 24 hours. Any one familiar with steel melting will recognize this as a great improvement in melting furnaces. The difficulty met with in this country has been to get oil of uniform quality. At the Chester Steel Casting Works they state that with one car of oil the furnace works splendidly, but with the next they may have difficulty in keeping up the heat. A supply of oil of uniformly good quality is necessary for the successful work- ing of this furnace. A patent pouring ladle is also used in which the metal is kept up to its original heat as long as is needed in order that a number of castings can be all poured at the same temperature. The moulding material used is pure fire-clay, hard burnt, finely ground and mixed with sugar or molasses as a binding material. This is perfectly fire-proof at the temperature of the molten wrought-iron, and is said to answer well. Properties of mitis castings. — The material being practically wrought-iron, the castings do not have to be annealed before using. The thinnest or most complicated castings can be pro- duced, which it would be almost impossible to forge in wrought- iron, thus furnishing difficult forged pieces at not much greater expense than ordinary castings. When there is less than J^ per cent, of phosphorus present, the castings can be welded and forged in all respects as wrought-iron. The castings come out of the above moulding material with a remarkably smooth surface and a peculiar bluish tint ; there is no sand burnt into their surface. The castings are as ductile as the iron from which they are made, but when tested for elongation under stress it was found that they did not elongate so much. This is counterbalanced, however, by the fact that as mitis metal ALUMINIUM-IRON ALLOYS. 58/ contains no intermingled slag and absolutely no fibre, it has the same strength and elongation in all directions. In general, the tensile strength of the iron is increased, Mr. Ostberg says 20 to 50 per cent., but the lower figure is probably nearer correct. Experiments at the Bethlehem Iron Works showed 10 per cent, increase in tensile strength, with no change in the elongation. Mitis castings are, in short, objects cast in low-carbon iron, yet having all the desirable properties of wrought-iron. The uses to which they can be put are very numerous, including all pur- poses for which malleable castings are suitable, and particularly to replace complicated or even impossible forgings in any shape which admits of casting. Rationale of the process. — The following facts are to be ex- plained: I. On adding ferro-aluminium to wrought-iron brought into a pasty fusion, the charge immediately becomes very liquid. 2. The castings made of metal thus treated are almost entirely free from the blow-holes which render ordinary wrought-iron castings almost useless. Mr. Ostberg's explanation of the first point is that the addi- tion of the aluminium produces a sudden lowering of the fusing point of the wrought-iron by some 150° to 250°, thus leaving the metal superheated to that extent above its new melting point, and consequently with greatly increased fluidity. That this view is erroneous has been shown by the fact that the alu- minium added does not remain in the iron. Numerous analy- ses made abroad have failed to find any aluminium in the cast- ings. Mr. R. W. Davenport, a trustworthy analyst, could find it in no instance. Mr. A. A. Blair, of Philadelphia, one of the greatest authorities on the analysis of iron and steel, has been unable to find any, and considers it very improbable that 0.03 per cent, could escape detection. Mr. Ostberg also admits that it has never been detected, and virtually abandons his ex- planation by saying, in a letter to Mr. Howe, " An iron may contain i or 2 per cent, of aluminium without any noticeable effect in the making of castings ; it is not the presence of the aluminium, but the act of adding it at a certain moment, that produces the effect." 588 ALUMINIUM. Mr. Osmond has definitely settled this question of the melting point of aluminium-iron alloys by determining the fusing point of an alloy with 5 per cent, of aluminium. This he found to be only 25° below that of the pure iron, so that the efifect on the melting point is really inappreciable. Mr. R. W. Davenport offers the following explanation : A rise of the temperature of the metal would explain the phenom- ena as satisfactorily as a fall in the melting point. Since the aluminium oxidizes and passes into the slag, probably accord- ing to the reaction, 2AI + 6FeO = sFeO.AljO, + sFe, the high calorific power of the aluminium would supply a con- siderable quantity of heat, in spite of its small amount. Mr. Davenport then assumes the calorific power of aluminium as 10,000, leaves out of consideration the heat absorbed by the reduction of FeO to Fe and the union of FeO with Al^Oj to form the aluminate, and from this calculates that the oxidation of 0.06 per cent, of aluminium would produce 640 calories of heat and raise the temperature of the bath about 40°. He fur- ther implies that a rise of 120° would thus call for the oxida- tion of only 0.18 per cent, of aluminium, which might easily have been added to Mr. Ostberg's castings. This explanation is as untenable as Mr. Ostberg's, for the following reasons: i. The calorific power of aluminium burn- ing to alumina is very nearly 7500* ; when producing hydrated alumina (the datum usually given in the tables) it is only lop higher. 2. The heat required to reduce ferrous oxide is pretty accurately known, and there is no reason why this should not be taken into account. 3. The heat of combination of ferrous oxide and alumina is certainly not known, though probably qiiite small; but on inspecting slag from mitis metal, white patches or flakes of alumina are to be seen in it, showing that some of the aluminium, if not the greater part, escapes as * Ann, de Chim. et de Phys., June, 1889, p. 250. ALUMINIUM-IRON ALLOYS. 589 alumina uncombined. It would be erring on the safe side to leave this quantity out of consideration altogether. 4. As the ferro-aluminium is thrown into the crucible cold, the melting of it will very nearly absorb as much heat as is developed by its chemical reactions. .Reconstructing the formula with these points in view we have — Heat developed. Heat absorbed. Oxidation of aluminium 0.06X7250 =435 Redaction of ferrous oxide 0.24XJX1286 = 240 Melting of ferro-aluminium 1 .00 X 200 (Gruner) = 200 435 440 Making all reasonable allowances, the increase of heat due to the addition of the alloy will be too small to be noticeable. I might say, finally, that if the charge were left in the crucible untreated, and heated one or two hundred degrees hotter than the temperature at which the charges usually receive, their ferro-aluminium, the wrought-iron would not flow with any- thing like the fluidity shown by mitis metal. It is probably safe to say that wrought-iron untreated could not, at any prac- ticable temperature, be made as fluid as the aluminium-treated metal. What then will explain the increased fluidity? The author asks a consideration of the following facts : Every metal melter who has tried to run down wrought scraps of any metal, zinc, copper, tin, etc., knows how the melt will become pasty, and in many cases resist every effort to run it together. Now zinc is zinc, and its melting point is somewhere about 420°, and yet the surface of the scrap metal will keep together while the interior is quite fluid. This is particularly noticeable with copper. It appears that the previous working has driven particles of for- eign matter, particularly oxide, into the pores of the metal, and this less fusible skin keeps the melted particles from coming in contact and running together. Again, it is noticeable with many metals that the absorption or solution of a minute quantity of 590 ALUMINIUM. its oxide tends to make the metal pasty. Let any one blow air for a very short time through perfectly fluid zinc, and in an in- credibly short space the metal will thicken up, and an amount of mush out of all proportion to the amount of oxide which could have been formed, will float on the surface. It can also be noticed that on heating up this mushy metal again it passes out of the solid state at nearly the same temperature as pure zinc ; but instead of becoming fluid it remains pasty for many degrees' rise of temperature above that point. The case of wrought-iron appears to me to be similar to those just noted. When wrought-iron scrap is heated it becomes soft at a mod- erately high temperature, but on heating it further to get it to form a homogeneous bath the hard, wrought surface is a great hinderance to its running together; a very high temperature causes the separate pieces to unite imperfectly into one body, but because of the scale and oxide present from the first, to- gether with that formed during heating, the fusion is thick and viscid. Here the second phenomenon pointed out above can be noticed. This metal, because of the oxide in it, requires a higher temperature to make it fluid than if the oxide were not there. What follows then ? Remove the oxide by some means, and the bath becomes perfectly fluid, and is superheated with respect to \i?, proper melting point, i. e., the melting point of the metal uncohtaminated with oxide. The aluminium added does this work, reduces the oxide to metallic iron, the infusible and unalterable alumina produced rises to the surface, and the bath attains its extraordinary fluidity for the reason just given. With regard to the lessening of blow-holes, we will first note their cause. First, they are not shrinkage cavities, which are caused by the metal chilling too quickly after pouring in the mould, and the sink-head not remaining fluid long enough to feed the cavities made in the body of the casting as it cools. The metal which is most liquid and least likely to chill quickly will produce the least number of unfilled shrinkage cavities, and these advantages are possessed by the wrought-iron when con- verted into mitis metal. But, in considering blow-holes proper, ALUMINIUM-IRON ALLOYS. 59 1 we note three distinct causes for them in wrought-iron cast- ings. 1. When molten metal is poured into a mould prepared with the greatest care there is always some ebullition caused by the expulsion of moisture from the mould or moulding material. This boiling will continue as long as the metal is fluid enough to allow the vapor to escape, but as soon as it stops escaping, there will be some gas entangled in the solidifying metal, pro- ducing cavities. The gas thus entrapped is principally hydro- gen with some oxygen, most of the oxygen being caught by the metal and forming a lining of oxide inside the cavity. 2. When a stream of liquid, molten metal or water, is poured, it draws with it into the bath a considerable quantity of air. Every one who has poured water from a pitcher into a goblet has had opportunity to see this phenomenon, which occurs just as certainly and perhaps to a still greater degree when molten metal falls six or eight inches through the air and down a pour- ing gate. Such an arrangement is an actual suction apparatus. The gas thus drawn into the metal will be principally air with whatever proportion of moisture it contains. This gas escapes as long as the metal remains fluid enough, but will be largely entangled in the solidifying metal. 3. Metals possess the property of dissolving or occluding gases while molten, just as water dissolves air. They can re- tain some gas even when solid, but when they melt their dis- solving power is largely increased. It results from this, that if iron is kept molten for some time it will be able to dissolve a certain quantity of gas. As it cools toward its setting point its dissolving power may increase or decrease, I cannot say which ; but it is certain that when very near to its setting point it sud- denly loses this power of solution, and considerable quantities of gas are evolved. The corresponding phenomenon in alumin- ium is very marked and quite easy to observe (see p. 57). The gas being set free near to the setting point, much of it is entangled in the casting. 4. In castings made of cast-iron there is another cause of 592 ALUMINIUM. blow-holes ; viz., the carbonic oxide produced by the carbon present reducing oxides ; but since carbon is very low in mitis castings and the dissolved oxides are otherwise removed,. this cause need scarcely be taken into account. Reviewing the causes of blow- holes, we note that the first two will occur in casting any kind of metal, but that kind which is most fluid in the mould and remains fluid the longest time will permit most gases to escape and so set with the smallest num- ber of blow-holes. The superiority of aluminium-treated metal in these requirements gives it great advantages over these causes of blow-holes. For the same reason, when the third cause is considered, fluidity of mitis metal down almost to its melting point, with a small range during which it is pasty, al- lows more of the dissolved gas to escape when once set at lib- erty. In the author's opinion, the increased fluidity of mitis metal and the closer definition of its melting point, are the chief causes of the comparative freedom of the castings from blow-holes. However, the point has been raised by Mr. Howe, that perhaps the aluminium imparts to the iron greater power of holding gases in solution, not directly by alloying with it, since none remains in the iron, but indirectly by removing the oxygen. In one of Mr. Davenport's experiments, wrought- iron was melted alone in a crucible, and while oxygenated and boiling gently, i per cent, of ferro-aluminium was added, intro- ducing 0.04 per cent, of aluminium and o.i per cent, of silico,)!. It appeared to lessen the evolution of gas, and in 2J^ minutes the iron was perfectly still, and when poured three minutes later lay quiet in the mould like cast-iron. In all of Daven- port's experiments with molten iron, the addition of aluminium seemed to check the evolution of gas. We cannot say that Mr. Howe's suggestion is impossible, yet it is very improbable, because one of the laws of solution of gases in liquids is that when a liquid has dissolved as much of one gas as it is able, it will yet take up as much of another gas as if the first were not present.* If then, we have the case of solution of gases in *Deschanel's Natural Philosophy, pp. 182, 183. ALUMINIUM-IRON ALLOYS. 593 molten iron, the removal of one gas would not affect the amount of any other gas which the iron might take into solu- tion. When wrought iron is boiling the cause is that carbon present (perhaps that still left in the metal, but more probably the graphite of the plumbago crucible) is reducing the dis- solved ferrous oxide and forming carbonic oxide. To explain the action of the aluminium in stopping this ebullition, it is not necessary to suppose that it gives the iron increased power of retaining in solution the gases which are escaping (Howe's ex- planation), nor yet that it reduces the carbonic oxide gas as it forms, which reaction might take place,* but simply that it re- duces all the dissolved ferrous oxide at once, and so leaves no available oxygen in the bath for the carbon to combine with. With regard to any carbonic oxide which might be held dis- solved in the iron, and by being evolved near the setting point form blow-holes, it is quite probable that the aluminium takes the oxygen away from it also, and so lessens chances of blow-holes from this cause. If such gases as hydrogen or nitrogen are dissolved in the molten' iron, the greater fluidity of the bath will have no tendency to cause their evolution, the aluminium cannot influence them chemically, and it is alto- gether probable that they remain. Professor LeVerrier has given a very satisfactory explanation t)f the fact that the hydrogen and nitrogen also cease to be evolved when the carbonic oxide stops being evolved. He cites the case of carbonated water, saturated with gas, which evolves nothing when quiet, but the agitation caused by blowing a very gentle current of air through it liberates large quantities of gas. Just so in steel. When the evolution of carbonic acid ceases, the bath is no longer kept agitated, and in consequence the other gases cease coming off also, producing a result appar- ently out of all proportion to the quantity of aluminium which produces it. * Professor Arnold blew 40 gallons of pure carbonic oxide through a crucible of mol- ten steel containing aluminium, and obtained an increase of 35 per cent, in the carbon present in the metal, proving that aluminium can take oxygen away from carbon. 38 594 ALUMINIUM. The arguments just presented may be summed up as follows : 1. Treatment with aluminium makes the bath fluid because it removes the dissolved oxide which made it pasty. 2. Treating with aluminium stops the evolution of gas be- cause — (a) It combines with all the oxygen present, and so removes the essential gaseous ingredient of the carbonic oxide which was being evolved ; (^) the stopping of the formation of carbonic oxide allows the bath to remain quiet, and so the other gases are not agitated out of the solution. 3. Treating with aluminium also lessens blow-holes in cast- ings, because the greater fluidity of the metal allows the easier escape of the gases mechanically entangled in it during cast- ing. Influence of Aluminium in Puddling Iron. The Cowles Company state in one of their pamphlets that if a small percentage of aluminium is added to iron in the pud- dUng furnace, the bath comes to nature quicker, and the wrought-iron produced is much stronger, equalling the best grades of mild steel. An article in the "Iron Trade Review," September, 1887, stated that on adding o.i per cent, of aluminium to iron about to be puddled, the tensile strength was raised from 52,000 to 60,000 lbs. per square inch, an increase of 16 per cent., while the elongation was variously increased up to 20 per cent. The only thoroughly reliable report on this subject is made by Mr. G. W. Thomson, a gentleman connected with the well- known firm, Messrs. P. & W. MacLellan, Glasgow. He took a charge of 373 lbs. of No. 4 forge pig-iron, charged it into the usual type of puddling-furnace, and when nearly melted threw in an ingot of ferro-aluminium, which weighed 13 lbs., con- tained 7. 11 percent, of aluminium, and so introduced 0.25 per cent, of aluminium into the bath. The operation of puddling then went on as usual, and with no noticeable change, except that when the charge was just getting pasty it suddenly swelled up considerably, slag flowed from it abundantly, and the charge ALUMINIUM-IRON ALLOYS. 595 was very soon ready for balling. In the shingler and rolls the balls worked decidedly stiffer than usual. The result was very satisfactory. The ordinary iron averaged 22 tons tensile strength, with 12 per cent, elongation. , The aluminium-treated iron showed 31 tons tensile strength and 22 per cent, elonga- tion, being gains of 40 and 80 per cent, respectively. These bars stood the bending test perfectly, and when polished and cut showed a remarkably fine surface and close grain. They also forged satisfactorily. If the above reports are to be relied on, this subject deserves looking into by every puddling-mill manager desirous of im- proving the quality of his iron. Influence of Aluminium on Cast-Iron. Very early in the history of aluminium, away back in 1858, the Tissier Bros, suggested the possibility of this application of aluminium by saying : " When aluminium has become low in price, it will be interesting to see what qualities it can conr.- municate to cast-iron, introduced in large or small quantities." This suggestion does not appear to have led to any experi- ments in this line until after 1885, when the discovery and publication of the mitis process turned many experimenters toward the determination of the effect of aluminium on cast- iron. In April, 1886, Mr. Sellers, of Philadelphia, remarked at the Washington meeting of the National Academy of Science that he had made a series of experiments on the use of alumin- ium with iron in casting, with the result that the castings pro - duced were very sharp and without any flaws. In December, 1887, the Williams Aluminium Company, of Boston, began the sale of an alloy called by them aluminium-ferro-sihcon, which they recommended to founders for addition to cast-iron in the ladle, claiming increased •fluidity of the iron and greater free- dom from blow-holes. This company is now located in New York, with works in Newark, N. J., and manufactures and sells this alloy in tolerably large quantities. The claims of this company, as also of other companies selling ferro-aluminium 596 ALUMINIUM. for foundry practice, are certainly very broad, but we will dis- cuss in how far they are probably true. These claims are, in general, that the addition of aluminium — 1st. Makes the iron more fluid. 2nd. Makes hard iron softer. 3rd. Frees castings from hard spots and blow-holes. 4th. Lessens the tendency of the metal to chill. Sth. Increases the resistance of the iron to chemical action. It is also stated that while good, soft iron is made more fluid and benefited to some degree, yet the advantages of treating with aluminium are most evident with poor, hard, white iron. We will review these claims in the Hght of those trustworthy experiments which have been made and certified to. It is now generally conceded that the addition of ferro-alu- minium does affect the quality of the castings. The method of adding it which has been generally adopted is to put some pieces of broken ferro-aluminium into the bottom of a ladle, preferably a hot one, and tap the iron from the cupola directly on to the alloy. In this way the maximum benefit is obtained. A German experimenter states* that it is important that the iron be not too hot when the ferro-aluminium is added, for if it is white-hot, the aluminium burns with a greenish flame and a peculiar smell ; a golden-yellow heat is recommended as the right heat for treatment. If the ferro-aluminium is thrown into the molten iron at this heat, the streaks playing on the surface of the metal disappear, and the bath becomes blistery looking. The same writer states that, in general, white iron is undoubt- edly improved by this treatment, but that gray iron is made porous, the pores showing particularly in the lower parts of castings. While there have been many testimonials from practical men as to the benefits derived from the use of ferro-aluminium, testi- monies so numerous that the fact of benefit has become indispu- table, the only systematic investigation of this subject is that * Zeitschrift des Vereins Deutscher Ingenieure, 1889, p. 301. ALUMINIUM-IRON ALLOYS. 597 made by Mr. W. J. Keep, of the Michigan Stove Company, Detroit, with the co-operation of Prof. C. F. Maybery and L. D. Vorce. Their results are embodied in two quite lengthy papers, one read before the American Association for the Advance- ment of Science at their Cleveland meeting, August 17, 1888, the other published in the transactions of the American Insti- tute of Mining Engineers, December, 1889. As we shall quote many of the results given in these papers, we will first explain the methods employed in pursuing the investigation. Two kinds of iron were used, having the following composi- tion : — , White iron. Gray iron. Silicon o.i86 1.249 Phosphorus 0.263 O.084 Sulphur 0.031 0.040 Manganese 0.092 0.187 Graphitic carbon 0.95 3.22 Combined " 2.03 0.33 Total " 2.980 3'S50 The ferro-aluminium used contained 11.42 per cent, of alu- minium and 3.86 per cent of silicon. The melting was done in a covered plumbago crucible, and the melt was run into test- bars one foot long, some having a section y^ inch square, others i inch wide and ^V inch thick. The ferro-aluminium was added to the molten iron, the smallest quantity first, and, after casting, part of this first cast was remelted with more ferro-aluminium, and so on. Another series of heats was made under exactly the same conditions but without adding alumin- ium, these tests serving for comparison and determination of the true effect of adding the ferro-aluminium. The general plan of the tests consisted in adding 0.25, 0.50, 0.75, and i.oo per cent, of aluminium to the white iron and 0.25, 0.50, 0.75, i, 2, 3, and 4 per cent, to the gray iron, the test-bars being care- fully examined as to strength, shrinkage, etc., and comparison made with the corresponding remelt of the iron alone. The weak point of the first set of, tests, recorded in the first 598 ALUMINIUM. paper, was the fact that many of the changes credited to the addition of the ferro-aluminium might probably have been ac- counted for by the silicon in the alloy added, and so the results could not be accepted as demonstrating the influence of the aluminium except where the change was in a direction con- trary to that which the silicon could have produced. Mr. Keep recognized at once the necessity of differentiating the effect of these two elements, which was accomplished very ingeniously by finding an iron containing the same amounts of silicon, car- bon, etc., as the ferro-aluminium, and making comparison tests with this iron in place of the aluminium alloy; also, by adding pure metallic aluminium to the iron. Taking the second paper in connection with the first, the conclusions advanced may be regarded as final and beyond reasonable doubt. Since Mr. Keep's method of presenting his results is in some cases not easily understood, I have, from an inspection of his diagrams, re-cast the results into tabular shape. Solidity of castings. — All Mr. Keep's tests bore on this point, but one particular test was made with white iron, adding only O.I per cent, of aluminium (0.03 of silicon). The castings were of slightly finer grain, but blow-holes and interstitial cav- _ities were noticeably absent, this accounting for the largely in- creased strength. The resistance to dead weight was increased 44 per cent., and to impact 6 per cent. No check test was made to eliminate the effect of the silicon added, but the effect produced was much greater than can with any probability be ascribed to the silicon alone. Does the aluminium remain in the iron f — To determine this question, enough ferro-aluminium was added to white iron to introduce 0.25 percent, of aluminium (0.08 of silicon), and the resulting metal was re-melted five times. Samples were taken of each melt, and found to contain at first addition 0.23 per cent, of aluminium, and at the successive re- meltings 0.20, 0.18, 0.15, 0.13 and o.io per cent, respectively. On compari- son with white iron remelted alone the same nuiftber of times, the influence on the strength is also seen to endure through the re-meltings ; for instance — ALUMINIUM-IRON ALLOYS. 599 Increase in Strength (per cent). No. of Per cent. , ^ » re-melting. of aluminium. Dead wt. Impact, 0.23 35 109 1 0.20 118 235 2 0.18 115 165 3 015 '23 150 4 0-13 32 62 5 o.io 21 39 The analyses of Mr. Keep's other tests also answer the above question affirmatively, since, as before explained, the percentage of aluminium was increased gradually by adding ferro-alumin- ium to a previous melting, giving the aluminium several chances to escape if it tended to do so, before a large percentage was reached, but the calculated amounts agreed with those actually found as follows : — Found on Analysis. Percentage by calculation. White iron. Gray iron. 0.25 0.25 O.IO 0.50 0.54 0.14 0.7s 0.89 0.32 i.oo 1.28 0.75 2.00 1.50 3.00 2.23 4.00 3-84 There were, of course, unavoidable irregularities in the mak- ing of the tests, but the general conclusion from the above an- alyses is that all the aluminium remains in the white iron and almost all in the gray, the reason of the slight loss in the latter case not being apparent. On adding small amounts of alumin- ium to wrought-iron, none remains in the metal ; the reason for the contrary phenomenon in the case of cast-iron is that the presence of carbon in large quantity prevents the presence of iron oxide dissolved in the iron, and the aluminium remains because there is no such oxidized compound present to slag itofif. Transverse strength. — The addition of aluminium as ferro- aluminium had the general effect of strengthening the iron, the 600 ALUMINIUM. white iron showing the greater improvement, and the resistance to impact being increased more than the resistance to dead weight. The following table gives the percentage increase in strength in each case, the minus quantities in parentheses mean- ing decreased strength : — White Iron. Gray Iron. Percentage of , aluminium. Dead wt. Impact. Dead wt. Impact. 0.2S 32-S 82.8 -(12-5) -(15-5) 0.50 128.0 291.0 -(8.9) 44.0 0-7S 1 13.6 240.0 S.8 23.0 1. 00 1 1 7.6 350.0 2.4 30.0 2.00 —(10.4) 29.0 3.00 4.6 II.O 4.C0 iS-8 130.0 Since, for every i per cent, of aluminium added, 0.34 of sili- con was contained in the ferro-aluminium, the question very naturally occurred, how much of this benefit was due to silicon. Tests were therefore made on this point, proving the part taken by the aluminium. The figures show the percentage in- crease in strength, as in the former tables. White Iron. Addition. Dead wt. Impact. I per cent, aluminium in ferro-aluminium 1 1 7.6 3S0'0 Cast-iron, introducing the same quantity of silicon. 126.8 94.6 I per cent, of aluminium as pure aluminium I4I-7 156.5 The conclusions to be drawn are, therefore, that while the silicon in the ferro-aluminium is sufficient to explain the in- creased resistance to a dead weight, yet the increase in resist- ance to impact is clearly due in large part to the aluminium. Elasticity. — The closing of the grain of the iron on treatment with ferro-aluminium caused the iron to be less brittle, or more elastic. The deflection of the dififerent specimens for a fixed weight was measured, and the increase in deflection was found to be (in percentages) — ALUMINIUM-IRON ALLOYS. 6oi Gray iron. 125 116 147 133 "33 194 193 Percentage of aluminium. White iron. 0.25 31 0.50 89 0.7s 100 1. 00 153 2.00 3.00 4.00 To distinguish the effect due to the silicon added, tests made with siHcon and aluminium alone showed increased deflections as follows : Addition. White-iron. I per cent, of aluminium in ferro aluminium 153 Cast-iron containing an equal quantity of silicon 11 I per cent, of aliuninium as pure aluminium 100 It is thus proved that the increased elasticity is due to the aluminium, caused, as Mr. Keep believes, by a very uniform distribution of the graphitic carbon when aluminium is the ele- ment precipitating it, a phenomenon to be examined further on. Effect on the grain. — Mr. Keep found that the addition of ferro-aluminium made the grain of the iron decidedly darker, caused by the separation of more carbon as graphite. It is well-known that silicon acts in the same direction, but Keep's first impressions were that the separation of graphite took place much nearer to the setting point of the iron than he had ever observed to result from silicon acting alone. A check test, adding cast-iron without aluminium, confirmed this impression ; for instance. White-iron. Addition. (Description of fracture.) White. 0.25 per cent, aluminium as ferro-aluminium A few gray specks.. 0.50 " " " " Light gray. 0.75 " " " " Gray. i.oo " '■ " " Dark gray. - Cast-iron containing an equal quantity of silicon to preceding White— a few gray specks. 1.00 per cent, aluminium as pure aluminium Dark gray. The comparisons made show that aluminium is undoubtedly 602 ALUMINIUM. active in changing combined into graphitic carbon ; from a com- parison of the analyses of the above tests it appears that it is even more powerful than silicon in accomplishing this result, since 0.25 per cent, of aluminium (with 0.20 per cent, of sili- con) seems to give a fracture identical with that produced by 0.62 per cent, of silicon alone. Mr. Keep notices that the separation of the graphite seems to take place instantaneously just as the iron is about to set, and not before, the result of which is that there is very little opportunity for any gathering together of the graphite into soft spots in the casting, and also that no matter how quickly the iron sets, the graphite will be mostly separated out, and thus the iron chills less. This effect is very noticeable in gray-iron, where the first addition of 0.25 per cent, aluminium as ferro- aluminium decreased the depth of chill fully one-half and slightly darkened the fracture ; subsequent additions of two, three and four times as much reduced the chill to nearly noth- ing ; while with 2 per cent, of aluminium added, the drop of the graphite was so nearly instantaneous that no chill was visible. Fluidity of the iron. — The general conclusion from Mr. Keep's tests is that, with white-iron, small additions of alumin- ium, such as would be used in ordinary foundry practice, in- crease slightly the fluidity; one-half per cent, of aluminium and over decreases the fluidity. Gray-iron is rendered decidedly less fluid by any addition of aluminium. Mr. Keep notices* a peculiarity of cast-iron containing aluminium which is similar to that we have remarked in pure aluminium (p. 446) ; viz., that as the metal flows it seem to have a skin in front of it, causing it to run with a very thick edge, and if two currents of this iron come together in a mould, they are apt not to unite, but to simply chill without union. Shrinkage. — Mr. Keep measured carefully the shrinkage of the different specimens of aluminized cast-iron. The general conclusion was that aluminium reduces the shrinkage if enough of it is added. The following table shows the reduction in the shrinkage, in percentage of the original shrinkage, under the different conditions — ALUMINIUM-IRON ALLOYS. 603 Reduction of shrinkage (per cent.) White-iron. Gray- IRON. Percentage of aluminium. Square bar. Thin bar. Square bar. Thin bar. 0.25 -(4) -(4) 14 0.50 -(4) -(3) 4 0.7s 16 -(4) 4 14 1.00 21 -(4J 9 16 2.00 — — 19 16 3.00 — — 34 16 4.00 — — 28 26 It will be noticed that, particularly with the square bar, the first two additions of aluminium have very little effect either way, but that with subsequent additions the amount of shrink- age is reduced 5 to 30 per cent. Mr. Keep thinks that this behavior is dependent on the action of the carbon ; that the small amounts of aluminium are chiefly active in closing blow- holes and giving soundness to the casting, but the larger amounts have a noticeable influence on changing combined carbon into graphite, and that the increased deposition of graphite just as the metal sets increases its volume and de- creases the amount of shrinkage. Hardness. — The indications from Mr. Keep's tests are that aluminium of itself hardens cast-iron, but, by its influence in changing combined' carbon into graphite, it indirectly renders the iron softer. It is noticeable that if an iron cast with soft spots, the parts in between being hard, that the addition of alu- minium caused the graphite to be dropped so near to the set- ting point that it had no opportunity to collect into spots, and was therefore uniformly distributed, rendering the iron uni- formly softer. Aside from the above determinations, many testimonials could be quoted from practical iron founders as to the practical benefit to poor iron gained by adding ferro-aluminium. Per- haps one of the most striking results is the increased time which the aluminium-treated iron will remain molten. For in- stance, Mr. Keep found that 0.02 per cent, of aluminium added to a ladle of iron caused it to keep fluid 5 minutes, while a simi- 604 ALUMINIUM. lar ladleful of the same metal without aluminium became solid in 2j4 minutes. This property of keeping fluid longer is of direct usefulness in a foundry where it is necessary to run a large number of small castings, during which operation there is usually much trouble experienced in keeping the iron fluid, unless it was very hot to start with. I am quite assured of the fact that the addition of a very small amount of aluminium does have the efifect described above. A friend of the author described an experiment in which a large ladleful of iron was tapped from a cupola and taken for pouring about 200 yards, partly through the open air. The iron was not hot enough to fill the moulds satisfactorily. Another ladleful, similar in all respects, was tapped immediately after, some ferro-aluminium being placed in the ladle. This iron was taken to the same place for casting, filled the moulds perfectly, and when brought back to the cupola the metal left in the ladle was still fluid enough to make good castings. I have heard similar reports from trustworthy sources, all stating that the judicious use of a small quantity of ferro-aluminium will result in nearly doubling the time during which a bath of iron will stay fluid enough to make castings. The practical results observed by the foundrymen are that they obtain cleaner, more solid, softer casti-ngs, with a large reduction in the percentage of defective castings. Mr. Adam- son, President of the British Iron and Steel Institute, says that " since using ferro-aluminium in my foundry, 80 per cent, of the the waste has been saved, and all the work manufactured is improved in quality." The general testimony seems to be that the castings come out of the sand cleaner, are much more free from blow-holes, work more uniformly in the lathe or planer because of the absence of hard or soft spots, come up sharper in the mould, and are generally stronger. There is not much improvement made on good gray foundry iron, in which case it is best to leave the good iron to itself ; but when the quality of the iron is low, and difficulty met in getting good cast- ings, then ferro-aluminium is of undoubted benefit. Very small ALUMINIUM-IRON ALLOYS. 60S additions are relatively of greatest effect ; Mr. Keep has stated that with only 0.00067 P^i" cent, of aluminium added to a poor quality iron it could be observed that the blow-holes were les- sened and the transverse strength noticeably increased. It is probable that the first one-hundredth of a per cent, of alu- minium added has more effect than the next five-hundredths ; and it is fortunate that this is so, for it opens up an extremely large field for the use of aluminium alloys. The rationale of the action of aluminium on cast-iron may be said to be an open question. That 0.25 to 0.50 per cent, begins to affect the carbon has been proven by Mr. Keep, yet these are quantities which are not used in ordinary foundry practice, where o.io per cent, may be taken as the maximum amount which the founder can afford to use, while o.oi to 0.05 percent, may be said to be the usual additions. It would appear to me that such small proportions of aluminium can only exert the effects attributed to them by (expressing it figuratively) holding a sort of balance of power, by which it determines a much greater result than the aluminium alone could possibly bring about. This idea is alluded to by Mr. Keep when he says that to use ferro-aluminium to best advantage the cast-irons should be mixed so as to get mixtures most suitable for treatment, or in other words, to get an iron more sensitive to the aluminium. What the conditions are which render an iron sensitive to the action of the aluminium has not been definitely determined. We might infer that since it acts in many respects similarly to silicon, the less the amount of silicon present the larger the scope of the aluminium, that is, the more room it has to act. Or, similarly, the more combined and less graphitic carbon present, the more opportunity is given the aluminium to bene- iit the iron. But, why the aluminium-treated iron should stay fluid so much longer, we cannot see. This seems to be one of those effects out of proportion to the quantity of aluminium present. For the present, we will rest the case here ; practi- cally, very small additions of ferro-aluminium can be made very advantageous; theoretically, we have, as yet, no satisfactory explanation of the facts observed. CHAPTER XVII. ANALYSIS OF ALUMINIUM AND ALUMINIUM ALLOYS. Commercial aluminium may contain the following elements besides aluminium : Silicon, iron, lead, tin, zinc, copper, silver, carbon, sodium, chlorine, fluorine. The method of attack gen- erally preferred is solution in pure caustic soda. Hydro- chloric acid usually attacks aluminium very energetically, and more easily the larger the percentage of silicon it carries, for the purest aluminium is not attacked very violently. When much silicon is present, the odor of silicuretted hydrogen is plainly perceptible during the action of the acid, thus indicating some loss of silicon. In dissolving in caustic soda this loss does not take place. Solution in bromine or iodine solution also offers similar advantages as respects avoiding loss of silicon. When analyzing particularly for carbon, the solvent used in the de- termination of carbon in iron may be appropriately used. We will consider these more in detail further on. A qualitative test may very appropriately precede the analy- sis, and will often save much time in the quantitative determi- nations. These qualitative tests may generally be made on the same lines as the others ; though in some cases shorter methods are practicable. Thus, after solution in hydrochloric acid, neu- tralizing with and adding excess of ammonia will show the presence of copper. If the solution is made hot, a spot of sul- phuric acid will show whether lead is present. Iron may be detected by potassium ferro-cyanide. Silver will remain as a white residue after the action of the acid. Chlorine is detected most easily by Berzelius' blow-pipe test with oxide of copper. Lead and zinc can be detected to a certain extent before the blow-pipe. A specimen of aluminium which gave an unmis- (606) ANALYSIS OF ALUMINIUM. 607 takable test for lead on charcoal before the blow-pipe, was found on subsequent analysis to contain nearly 7 per cent, of that metal. It appeared as though a much smaller proportion could have been thus detected. Another specimen similarly treated gave a good test for zinc, and the quantitative analysis gave 6.25 per cent, of that metal. Smaller amounts than this could probably be easily detected. On the other hand, how- ever, it is not probable that the presence of tin would make it- self evident in the charcoal test; for aluminium seems to pro- tect the tin very strongly from oxidation. An alloy known to contain 90 parts of tin to 10 of aluminium was tested on char- coal, and would not, with the hottest flame at my command, give the usual white coat indicating tin. Such being the case, it appears highly improbable that aluminium containing a small percentage of tin would give the test in question. The better test would be the white residue left on solution in hot, concen- trated nitric acid. The presence of iron or copper, or of both together, can usually be immediately recognized by dissolving a small piece of the aluminium in a borax bead, on a platinum wire, in the oxidizing flame. Copper thus detected by the au- thor was found on analysis to be less than i per cent, of the weight of the aluminium tested. The presence of sodium is generally shown by the metal decomposing water heated nearly to boiling, setting free hydrogen. This test can be easily made in a test-tube. The specific gravity of the metal, accurately taken, furnishes some intimation as to the presence of any of the heavy metals in any considerable quantity. Thus, 5 per cent, of silver in- creased the specifiq gravity from 2.65 to 2.8 ; 6 per cent, of lead from 2.7s to 2.9. This test is not, however, of much value, since, because of the very low specific gravity of aluminium, small amounts of heavy metals have only a small influence in increasing it, while silicon, an impurity most likely to be pres- ent, is lighter than aluminium (specific gravity 2.35), and therefore neutralizes to some extent the effect of the heavy metals. However, in commercially pure aluminium, containing 6o8 ALUMINIUM. only iron and silicon, the specific gravity can be made useful in indicating the amount of iron present within rather wide limits — say within i per cent. Another test of somewhat similar utility would be that given by Fr. Schulze.* He proposes to dissolve the aluminium in caustic alkali and measure the volume of hydrogen set free. If the metal contains no zinc, this volume will be approximately proportional to the amount of aluminium in the metal. Thus, Yi gramme of one specimen gave 648 cubic centimeters of hy- drogen; a similar weight of another, 580 cubic centimetres. These figures are then taken as expressing the relative purity of the two samples. In an aluminium works where a quick, approximately accurate test is needed, which can be made, if need be, by a person not necessarily a skilful chemist, and which is applied to testing samples of nearly the same compo- sition, this test would appear to be of practical utility. Determination of silicon. — Deville recommended the follow- ing method : " Dissolve in pure hydrochloric acid and evap- orate to dryness in a platinum dish. The evaporation to dry- ness is indispensable in order to render insoluble the quite important quantity of silica which is kept in solution by the presence of the acid. There remains an insoluble residue con- sisting of silicon, silicon protoxide and silica, which is washed by decantation with hot water and thrown on to a filter. This mixture of siliceous material is then calcined with the filter*in a platinum dish at low temperature. A little flame may often be seen coming from dififerent parts of the mass, caused by the production (at the expense of the silicon protoxide) of a little silicon hydride, according to the reaction — 3SiO+2H20=SiH4+3SiO, causing a slight loss of silicon. This may be altogether avoided by moistening the material with ammonia before calcining. The residue after ignition is a mixture of silicon and silica, the * Wagner's Jahresbericht, x. 23. ANALYSIS OF ALUMINIUM. 609 silicon protoxide having completely disappeared, and is care- fully weighed. This done, it is put into a platinuni crucible, and treated with a little dilute hydrofluoric acid, which dis- solves the silica and leaves the silicon, which is washed with care. This residue is then dried and weighed, and by subtract- ing from the former weight, the weight of silica is known with which it was mixed. This silica is calculated to silicon, and when the silicon weighed directly is added in, the result is the total weight of silicon in the metal tested." The above method probably does determine with accuracy the amount of silicon which remains after solution of the alu- minium, but Rammelsberg observed (see p. 56) that when alu- minium contains considerable silicon there is always some sili- con hydride formed during its solution in hydrochloric acid, which escapes and so causes error in the analyses. By passing the gases produced during solution through a solution of caus- tic potash, the silicon hydride was intercepted and the amount of silicon thus escaping was determined. It was found to be in two instances, 0.74 and 0.58 per cent., being 7 per cent, and 22 per cent respectively, of the total silicon in the metal (the first was very siliceous). It follows, therefore, that to make an ac- curate determination of the silicon in aluminium, hydrochloric acid cannot be used for attacking the metal unless care is taken to catch and determine the amount of silicon passing off as silicon hydride. Prof. Rammelsberg concluded from his study of the subject that silicon occurred in two forms in aluminium, a small amount free (like graphite in iron) the larger amount combined, and that on treatment with hydrochloric acid the free silicon remained as such, while the combined silicon partly escaped as silicon hydride and the rest was converted into silica. Such being the case, we can readily see the superiority of caustic potash or soda solution for dissolving the aluminium. Graphitoidal or crystalline silicon is dissolved by hot potash so- lution, the combined silicon will be dissolved, and if the nas- cent hydrogen forms for an instant any silicon hydride — as it does when acid is used — this gas is at once decomposed by the 39 6lO ALUMINIUM. alkali solution. The result is that if aluminium is attacked by hot potash solution, all the silicon present is oxidized and none lost. The solution of the aluminium should take place in a sil- ver or platinum dish or crucible ; a porcelain dish, however, is very slightly attacked, but glass should not be used. Care should be taken that the solution of caustic does not contain alumina or silica. After solution is complete, the liquor is fil- tered from any residue, hydrochloric acid is added until the re- action is acid, the bath evaporated to complete dryness until no smell of acid is perceptible, then moistened with a little hydro- chloric acid to dissolve any alumina formed, water added and the whole brought to boiling. The silica is then filtered out, dried, ignited, weighed and calculated to silicon. F. Regelsberger, chemist for the Aluminium Industrie Actien Gesellschaft, at Neuhausen, Switzerland, recommended using nitric acid to which was added one-fifth of its volume of hydro- chloric acid. The oxidizing power of the nitric acid prevents any loss of silicon as silicon hydride, and solution of the alu- minium takes place completely when the acid is warmed. This is the best and also the cheapest method of getting the alumin- ium into solution, and determining the total silicon. Mr. J. O. Handy, chemist of the Pittsburg Reduction Company, conducts the analysis as follows : * One gramme of turnings or drillings of the metal are dissolved in a mixture of 15 c.c. strong nitric acid and 2 c.c. concentrated hydrochloric acid. When 'the solution is nearly complete, add 2 c.c. more of the hydro- chloric acid, and warm. When completely dissolved, add 20 c.c. of concentrated sulphuric acid, evaporate quickly on a hot plate until fumes of sulphuric anhydride appear, cool, add 75 c.c. of water and 10 c.c. of hydrochloric acid, stir well, boil for five minutes, and filter out the mixture of silicon and silica. Wash first with water, then with hot, dilute (30 per cent.) hydrochloric acid, and then with water, until free from acid. The filtrate may be used for determining aluminium, iron, etc. The silicon and silica are dried and fused with * Journal of Applied and Analytical Chemistry, January, 1892. ANALYSIS OF ALUMINIUM. 6ll about 3 grammes of sodium carbonate. After fusion, dis- solve in hot water with hydrochloric acid, add 1 5 c.c. of con- centrated sulphuric acid, evaporate to sulphuric fumes, cool, add 75 c.c. of water and 10 c.c. of hydrochloric acid, heat to boiling and filter. Wash with water, 30 per cent, hydrochloric acid, then with water, and weigh as silica. If it is desired to determine the graphitoidal silicon, another sample is dissolved in the same way, but the mixture of silicon and silica first ob- tained is filtered out upon platinum sponge in a platinum filter in a Grooch crucible, washed, dried at 80° C. and weighed. Then wash with hydrofluoric acid and sulphuric acid, thus dis- solving away the silica, wash with hot water, dry again at 80° and weigh quickly the graphitoidal silicon. The loss in weight is, of course, the silica representing the combined silicon in the sample of, metal. Determination of iron {and aluminium'). — Deville's method of procedure was as follows : " The metal is dissolved in pure hydrochloric acid, evaporated to complete dryness in a plati- num dish, and the insoluble, siliceous materials filtered out. The solution is mixed with a large excess of nitric acid, evap- orated in a porcelain dish covered by a glass, thus converting the bases into nitrates, which are then transferred to a platinum dish. Here the solution is evaporated to dryness and calcined lightly on the sand-bath, the dish being covered, until abund- ant vapors of nitric acid rise from all parts of the mass. Cool, and moisten with a solution of ammonium nitrate containing free ammonia. Heat until all odor of ammonia has disap- peared, take up with water, and separate by decantation all sol- uble matter. (Decanting for greater precaution on to a filter.) The solution obtained contains all the sodium which was in the aluminium (see Determination of Sodium), while the insoluble residue is a mixture of aluminium and ferric oxide. This is heated to redness in the platinum dish which contains it, and transferred in whole or part into a tared platinum boat, where it is weighed. (It is best to make all these weighings with the boat inclosed in a glass tube closed by the flame at one end, 6l2 ALUMINIUM. and at the other by a well-fitting cork. The tube and boat are then weighed together.) The boat is then placed inside a por- celain or platinum tube, heated up to redness, and a current of pure hydrogen passed over it. When the tube is bright-red, the hydrogen is replaced by hydrochloric acid gas, which transforms all the reduced iron into ferrous chloride without touching the alumina. At the end of the operation, when the tube is just below redness, the hydrochloric acid gas is replaced by hydrogen. When nearly cold, the boat is drawn out and weighed, the loss in weight bei«g the ferric oxide removed, the portion still remaining being pure alumina. From these data the iron and aluminium are calculated. Very little trust can be placed on the alumina being perfectly white, to conclude that it is, therefore, free from iron ; for experience has taught me that one may be very greatly deceived in making this con- clusion. Experience will show about how long and at what heat the operation must be continued to remove all the iron ; but to be absolutely certain, the operation should be repeated for a short time, when the alumina will remain constant in weight if it is perfectly pure." The above operation is the most accurate method of deter- mining iron and aluminium, and is more applicable to estimating small quantities of iron in aluminium rather than vice versa, since in the latter case the operation is much prolonged in re- ducing and volatilizing the iron compounds. The estimation of small amounts of aluminium in presence of a large quan- tity of iron generally calls for special methods of separation, which will be detailed under the analysis of aluminium-iron alloys. Confining ourselves here to the determination of iron in commercial aluminium, we may suggest the following modi- fication of the above method. After solution in hydrochloric acid and separation of silica, the addition of a few drops of sul- phuric acid will precipitate any lead which may be present, and then the iron and aluminium may be precipitated with ammonia in slight excess. Any copper present will remain in solution, and the precipitate may be washed well, filtered. ANALYSIS OF ALUMINIUM. 613 ignited, and weighed. Instead then of removing the ferric oxide by the method given by Deville, the method of H. Rose may be used, which consists in fusing the two oxides with caustic potash (by alcohol) or caustic soda (from sodium) in a silver crucible, when alkaline aluminate will be formed, and on boiling the mass with water and filtering, the alkaline fluid will contain the aluminium, while the residue will be ferric oxide containing some potash. If a solution has been prepared containing only iron and alu- minium (lead, zinc, copper, etc., having been separated out) many methods have been proposed for separating these two elements. The oldest method is to make the solution nearly neutral and then pour it gradually into excess of pure caustic potash or soda solution heated nearly to boiling in a platinum or silver dish. The iron is precipitated, while aluminium re- mains in solution. The details of this test can be found in any treatise on quantitative analysis. It is not to be relied on in many cases, especially for determining a small amount of alu- minium in presence of much iron, since it is always prob- able that some aluminium is retained by the iron precipitate. Dissolving the iron hydroxide and reprecipitating will par- tially correct this. Solution of ordinary caustic soda is more apt than caustic potash to contain alumina, and so only the caustic soda made from sodium should be used. In either case the alkaline solution of potassium or sodium aluminate is heated nearly to boiling, and mixed with a large excess of am- monium chloride, when the alumina is entirely precipitated. The method most frequently used to separate ferric oxide from alumina is to weigh the two oxides together, then dissolve in concentrated hydrochloric or sulphuric acid, reduce the solu- tion by any suitable reducing agent (zinc, sulphurous acid gas, etc.), and determine the amount of iron present by titration with potassium permanganate or bichromate solution. These results are quite accurate if the proportion of aluminium is not small; when the latter is the case, as in ferro-aluminium, other methods give more satisfactory results, and are given further on in considering the analysis of ferro-aluminium. 6l4 ALUMINIUM. The solution of the aluminium to be tested in caustic alkali offers the quickest method of separating out the iron, for the alkali dissolves out all the aluminium and leaves iron in the residue. The best way to conduct this method of analysis is to roll out the aluminium into a thin sheet, put in moderately con- centrated alkali and allow it some time to dissolve. On filter- ing, the solution will contain all the aluminium while all the iron will remain, with various other metallic impurities, in the residue. This residue is then dissolved in acid and the iron easily determined in it without any interference from aluminium. Determination of lead. — Dissolve the aluminium in hot hydro- chloric acid, evaporate to dryness, moisten with hydrochloric acid, add hot water, and boil. Filter hot to separate out silica. To the hot, boiling solution add a few drops of sulphuric acid and let stand an hour. The precipitated lead sulphate can then be filtered out and weighed. Determination of copper. — Proceed as in determining iron, when the copper will pass into the filtrate on precipitating iron and aluminium by excess of aqua ammonia. If any amount of copper is present this solution will be blue, especially when con- centrated by evaporation. The solution may be evaporated to dryness, taken up with a little acid and the copper determined by any ordinary method ; or, the ammoniacal copper solution may be acidified with sulphuric acid, crystals of oxalic acid added, the liquid boiled, and the copper thus deposited as oxalate. This is washed in boiling water, dried, calcined at a gentle heat, and weighed as cupric oxide. The ammoniacal copper solution might also be acidified with acetic acid and the copper precipitated by lead foil. Determination of zinc. — Dissolve the aluminium in hydro- chloric acid or in caustic alkali and separate out silica, taking up, however, with strong acetic acid. On passing sulphuretted hydrogen through the solution, zinc will be precipitated free from aluminium or iron. The precipitate of zinc sulphide is washed carefully with distilled water saturated with sulphuretted hydrogen, dried, calcined very carefully in a muffle and after- ANALYSIS OF ALUMINIUM. 01$ wards very strongly over a blast lamp, and weighed as zinc oxide. A very satisfactory separation is also obtained by nearly neu- tralizing the solution, adding a limited quantity of acetic acid and then sodium acetate, and thus precipitating the aluminium (and iron) as basic acetates, leaving the zinc in solution, from which it can be precipitated by a current of sulphuretted hydrogen. Determination of tin. — ^Solution of the aluminium in hot nitric acid will leave the tin as insoluble meta-stannic acid. This residue is washed and treated with warm, dilute hydro- chloric acid, which dissolves the tin compound and leaves the silica. The tin is then thrown down in the solution of stannic chloride by any of the ordinary methods of precipitation, pre- ferably by sulphuretted hydrogen. The stannic sulphide is ignited gently, moistened with nitric acid, ignited more strongly, and the tin weighed as stannic oxide. Determination of silver. — Dissolve the aluminium in weak aqua regia, dilute and filter out the siHceous residue, which will contain also all the silver as chloride. Wash carefully, and then dissolve out the silver salt with concentrated ammonia. On neutralizing the ammoniacal solution with nitric acid, the silver chloride is again precipitated, washed by decantation, dried at 250° to 300°, and weighed. If the aluminium is attacked with caustic alkali, the silver will remain in the residue. This is washed, filtered, and treated on the filter with dilute nitric acid, which dissolves the silver. The solution of silver nitrate is precipitated by hydrochloric acid or sodium chloride, and the operation finished as before. Determination of sodium. — In the first steps of the deter- mination of iron, as given by Deville (p. 611), a solution was obtained free from iron and aluminium, and containing all the sodium which was in the aluminium tested. Deville describes the estimation of the sodium in this solution as follows : " To the solution is added a drop of ammonium oxalate, which sometimes precipitates a trace of calcium, indicative of the 6l6 ALUMINIUM. presence of fluorspar in the slag with which the metal may be impregnated. After filtering (if necessary) evaporate to dry- ness in a weighed platinum dish, cover and heat to 200° or 300°, to decompose the ammonium nitrate. Nitrate of soda remains. This is moistened with water, and on it are placed several crystals of oxalic acid. Dry, calcine, and there re- mains sodium carbonate, which is often impregnated with a little carbon from the decomposition of the oxalate of soda. Dis- solve the residue in water ; if not clear, filter. Mix the solu - tion with a little hydrochloric acid, evaporate to dryness, heat to 200°, and weigh as sodium chloride." Commercial aluminium rarely contains metallic sodium, but when it does exist it can usually be detected from the fact that the amount of chlorine present is not sufficient to combine with the sodium found. The presence of fluorine would weaken this conclusion, but it is seldom present in any quantity. Determination of chlorine. — Dissolve the aluminium in pure caustic soda, neutralize with nitric acid in very small excess, filter, and add several drops of nitrate of silver. The chloride of silver precipitated is washed well, dried at 300°, and weighed. Determination of carbon. — Carbon occurs probably all as com- bined carbon. A large proportion of this carbon would neces- sarily escape on treating the aluminium with acids or alkalies, for the nascent hydrogen developed during solution would form volatile hydrocarbons with it. To obviate this, the ammonkal solution of copper chloride should be used as a solvent, as in carbon determinations in iron. Solution in this, or, perhaps, in bromine, give a means of estimating the total carbon present. See Le Verrier's determinations on p. 57. Detection of fluorine. — Deville recommends the following pro- cedure : " Dissolve in caustic soda (using no more than is necessary), filter, and nearly neutralize with pure sulphuric acid. It is necessary to take care to leave a very small amount of free alkali without separating out any alumina, which falls at the mo- ment when neutralization is complete. Evaporate the whole in a platinum crucible, and heat, covering with a watch-glass coated ANALYSIS OF ALUMINIUM. 617 with varnish through which regular lines have been traced with a copper point. A section of quartz prepared in the same way does still better. Vapor of water and hydrofluoric acid are disengaged on heating the crucible, and the latter . etches the glass quite perceptibly. Sometimes, by breathing on the glass, the lines become more apparent. Determination of Titanium. — Dissolve 2 grammes of the alu- minium in caustic alkali solution, bring to boiling and filter quickly, washing repeatedly with boiling water. The residue contains all the iron and titanium. Dry and fuse with 8 grammes of potassium acid sulphate. After complete fusion, taking perhaps thirty minutes, dissolve in hot water and filter out the silica. To the solution add dilute ammonia until a sHght percipitate forms, add dilute sulphuric acid until the pre- cipitate just rc'dissolves, then add 4 drops of concentrated sul- phuric acid, dilute to 250 c. c, and saturate with sulphurous acid gas. Heat slowly to boiling and boil gently for 45 min- utes, occasionally adding a little strong sulphurous-acid water. Filter out the precipitated titanic oxide, wash thoroughly with hot water, dry, ignite and weigh as TiOj. In the filtrate, the iron can be determined by oxidizing the solution, precipitating with ammonia, washing, re-dissolving in sulphuric acid and titrating with potassium permanganate. (Handy.) Determination of Chromium. — This element is only present when intentionally introduced. The aluminium-chromium alloy is treated as for detecting titanium, when the chromium will re- main in the residue with titanium, iron and silicon. This resi- due is put in a platinum crucible and treated with i c. c. of concentrated sulphuric acid and 5 c. c. of hydrofluoric acid. Evaporate to sulphuric fumes, then add 4 grammes of potas- sium acid sulphate and fuse, finishing the fusion over the blast lamp. Cool, add enough sodium carbonate to make the fusion alkaline, ialso some nitre, and fuse again. Take up in hot water and filter. Add some ammonium chloride, heat and filter out any alumina. Reduce the solution by sodium hyposulphite or 6l8 ALUMINIUM. sulphurous-acid gas, and precipitate the chromium by am moiiia. Re-dissolve the precipitate in hydrochloric acid and re-precipitate with ammonia, wash, dry, ignite and weigh as Cr,0,. (Handy.) Analysis of Ferro- Aluminiums. It is not intended to give directions for the complete, analysis of ferro-aluminium. The determinations of silicon, carbon, sulphur, phosphorus, etc., are made the same as in steel or pig- iron. The only point offering special difficulty is the accu- rate determination of a small amount of alummium in presence of a large amount of iron. For doing this, the ordinary methods do not give satisfactory results. Thus, when deter- mining the iron volumetrically and the aluminium by dififer- ence, it is almost impossible to get concordant results When separating by caustic alkali, the results in aluminium are too low, for the iron precipitate being so abundant, carries much aluminium down with it. Also, a large amount of caustic alkali must be used, and since it sometimes contains alumina, con- siderable error may thus be thus introduced. Supposing that the alloy has been dissolved in acid, silica separated out and a solution containing only iron and alumin- ium obtained to work with, we will take up the various methods proposed to determine accurately the small amount of aluminium. Mr. H. N. Yates analyzed several hundred specimens of ferro-aluminium, and found that the caustic alkali separation gives aluminium too low, and is unreliable ; the method of weighing the two oxides together and afterwards determining the iron volumetrically with potassium bichromate gives pretty fair results with aluminium from i to 19 per cent.; but, with less than i per cent., as in steels, the most satisfactory results were obtained by the sodium thiosulphate separation. This latter is known as Chancel's separation, and is operated as fol- lows : The solution is neutralized with sodium carbonate, made dilute, solution of sodium thiosulphate (hyposulphite) added, and the liquid boiled until no moce sulphurous acid is disen- ANALYSIS OF ALUMINIUM. 619 gaged. All the alumina is precipitated as hydi-ate, with free sulphur, which may be washed, dried, ignited and weighed as alumina. The boiling until all sulphur smell is gone is a tedi- ous operation, and the following modification is said to give equally accurate results : To the slightly acid solution, sodium thibsulphate is added more than equivalent to the arhount of free acid present. The liquid is then boiled in a flask 10 to 15 minutes. The precipitated alumina is in a fine, granular state, easy to wash. The liquor is rapidly filtered, the precipitate washed with boiling water, dried, ignited and weighed. A great disadvantage of the foregoing method is that any phosphoric acid present in the solution will be precipitated with the alumina. With certain iron alloys this would materially afifect the result. To overcome this disadvantage, Mr. Peters suggested converting the alumina entirely into phosphate, still keeping the same method of separation from iron. The pro- cess, as mbdified, is as follows : If less than one gramme of iron is in the solution, it is diluted to 400 or 500 c.c. with cold water, and ammonia added until the solution is dark-red in color but contains no precipitate. Now add 3 c.c. of hydro- chloric acid (sp. gr. 1.2), and 2 grammes of sodium phosphate, dissolved in water and filtered. Stir till the precipitate formed is re-dissolved and the solution is clear. Add now 10 grammes of sodium hyposulphite dissolved in water and 1 5 c.c. of acetic acid (sp. gr. 1.04), heat to boiling, boil 15 minutes, filter as rapidly as possible, wash with hot water, dry, ignite in a porce- lain crucible raising the heat very carefully until all the carbon has burnt ofif, and weigh as AlPO^ (Al.Oa.P.O^).* Mr. R. T. Thompson, an English chemist, stated that he found Chancel's separation ineffectual in determining alumin- ium in presence of large, quantity of iron (probably mainly be- cause of the phosphoric acid present), and devised the follow- ing method of separation : The iron is reduced to the ferrous state by a current of sulphurous acid gas, excess of this gas is *The Chemical Analysis of Iron, A. A. Blair. 620 ALUMINIUM. boiled off, and when cool, phosphoric acid or sodium or am- monium phosphate is added in excess of that required to pre- cipitate all the alumina, then aqua ammonia until a faint permanent cloudiness is formed, finally excess of ammonium acetate. The precipitate generally contains a little iron, but on washing it, re-dissolving in acid and repeating the precipita- tion, it is obtained free from iron. The precipitate is dissolved in hydrochloric acid, a little nitric acid added, boiled, and nearly neutralized with caustic soda, and then boiled with an excess of the latter. The aluminium is precipitated as phos- phate, is washed with a i per cent, solution of ammonium nitrate containing about O.i gramme of ammonium di-hydric phosphate per litre, and ignited and weighed as aluminium phosphate. * A method of separation which has given the writer satisfactory results is the following :f To the cold, concentrated and slightly acid solution add an excess of solid sodium bi-carbonate in such quantity that after stirring a little remains undissolved and all the iron appears to be thrown down. Now add solution of potassium cyanide until the precipitate dissolves, then heat gently until the yellow color of potassium ferro- cyanide is pro- duced. Add a few drops of caustic potash to the somewhat turbid solution until it is perfectly clear ; then add excess of ammonium chloride and boil. Aluminium hydrate is precipi- tated free from iron, nickel or cobalt. As an analytical opera- tion this method works very satisfactorily ; care must be taken, however, in handling such large quantities of the very pois- onous potassium cyanide. It has been stated that if an excess of tri-methylamine is added to a dilute solution containing iron and aluminium, and let stand twenty-four hours, all the iron is precipitated and all the aluminium remains in solution. f The accuracy of this sep- aration has not been thoroughly tested. * Journal, Society of Chemical Industry, V, 152. t Chemical News, March 29, 1888. J Zeitschrift fiir Anal. Chemie, xxiv, part 5. ANALYSIS OF ALUMINIUM. 621 A. A. Blair recommends the determination of aluminium in iron and steel (when it occurs in very small amount) by the direct separation of ferric oxide from alumina, the method used being as follows : Dissolve the iron in strong hydrochloric acid, in a flask provided with a valve, thus keeping out air and allowing the iron to dissolve in the ferrous state. Neutralize with sodium carbonate, cool, dilute, add " milk" of barium car- bonate, let stand several hours, the flask being meanwhile well stoppered, and filter. The precipitate consists of all the alu- mina, ferric oxide, chromic oxide, phosphoric acid or titanic acid mixed' with the graphite and insoluble silica of the alloy. Wash well, treat with dilute hydrochloric acid, boil the solution with a slight excess of sulphuric acid, to precipitate the barium in the solution. Settle, filter, wash with hot water and concen- trate the solution by evaporation. To separate the iron from the aluminium, add citric acid to the amount of five times the weight of oxides present, and excess of ammonia. If the solu- tion does not stay clear, acidulate with hydrochloric acid, add more citric acid and excess of ammonia. Heat the clear solu- tion to boiling and add fresh solution of ammonia sulphide until all the iron is precipitated. Let settle, wash with water containing ammonium sulphide. The iron sulphide can be dissolved in acid and the iron thrown down with ammonia. The solution can be acidified with hydrochloric acid, boiled, the sulphur fil- tered out, evaporated to dryness, ignited, the residue fused with sodium carbonate, dissolved in water, filtered, acidulated with hydrochloric acid and the alumina precipitated by am- monia. It would be quicker to take the solution containing iron and aluminium and divide it into two portions. In one part the iron and aluminium are thrown down together by am- monia and weighed as oxides ; in the other the iron is sepa- rated as above. The last part may then be omitted and the aluminium found by difiference. The imperfection of this method is the fact that the precipitate of alumina finally ob- tained contains any chromic oxide, titanic oxide or phosphoric acid that may be in the original solution. The first two ele- 622 ALUMINIUM. ments may be seldom present, but some phosphorus is usually present, and the alumina will be too high for this reason. If the phosphoric acid is determined in this precipitate, this source of error may be eliminated. A more serious defect, however, is the fact that the iron is not completely precipitated, as may be proved by small flakes of iron sulphide being de- posited if the solution is let stand several days, showing that the ammonium sulphide has the power of holding small quan- tities of iron in solution. The aluminium results are thus apt to be too high. Tartaric acid might be used instead of citric, but it is more liable to contain alumina, and so gives results too high in aluminium. For separating large quantities of iron from small quantities of aluminium, the electrolytic method seems to be particularly applicable, for aluminium cannot be deposited from aqueous solution by the battery (except under exceptional conditions as alumina), while the iron can be totally deposited in a form easy to weigh. This method of separation is equal in accu- racy to any of the preceding chemical methods, and is not difficult of application. Dr. Classen gives the following method of procedure:* The solution may contain iron, cobalt, nickel, zinc, and aluminium. The solution of their sulphates is made very nearly neutral with ammonia and an excess of ammonium oxalate added, so that there are 2 or 3 grammes of this salt present to every o'.i gramme of oxides. When the solution is not above 40° C. (its volume is best 150 to 200 c.c.) it is electrolyzed with a current not exceeding 10 or 12 c.c. of oxy- hydrogen gas per minute. If the current is stronger than this, alumina may be precipitated. If the amount of aluminium is not greater than that of the iron (and other metals), this method gives accurate results. The solution remaining is evaporated to dryness, heated gently to decompose the aluminium salts, and finally ignited strongly to alumina. Prof. Edgar F. Smith gives an electrolytic method which for * Quant. Chem. Analyse durch Electrolyse, p. 79. ANALYSIS OF ALUMINIUM. 623 accuracy leaves nothing to be desired. * The solution of the sulphates is made dilute, and about 10 per cent, of sodium ci- trate and a few drops of citric acid added to it. This is elec- trolyzed with a current of about 12 c.c. oxy-hydrogen gas per minute, usingplatinum electrodes. The deposit of iron is firm, and is washed successively with water, alcohol and ether, and weighed. If the iron and aluminium have been already deter- mined together, the« aluminium can be calculated by differ- ence. If it is desired to weigh the aluminium directly, the citric acid solution must be evaporated to dryness, ignited to drive off organic matter, dissolved in acid, and the alumina pre- cipitated by ammonia or ammonium sulphide. Mr. John E. Stead of Middlesboro, England, has modified Chancel's separation as follows, with very satisfactory results : t The alumina is precipitated with sodium hyposulphite, thus separating it from the bulk of iron. The precipitate is dissolved on the filter in hot, dilute hydrochloric acid, and this solution evaporated to dryness in a platinum dish. When dry, pure caustic soda is put in, with a little water. After warming gently, more water is added, the whole boiled five minutes and filtered. The aluminium is precipitated in the filtrate by Peter's modifi- cation of Chancel's precipitation, and the aluminium thus weighed as phosphate, AIPO4 (22.13 per cent, aluminium). The advantage of Stead's method is that it gives three dis- tinct separations from the iron, thus completely eliminating it from the final precipitate, while the addition of an excess of phosphate causes the aluminium to precipitate quicker and more completely. Comparisons of the different methods for determining small amounts of aluminium in iron have shown this to be superior in accuracy to any other method. Analysis of Aluminium Bronzes. The ingredients usually present are copper, aluminium, silicon, iron, and sometimes zinc, tin, nickel or lead. Solution in nitro- * American Chemical Journal, 1888, p. 330. t Journal Society of Chemical Industry, Dec. 31, 1889. 624 ALUMINIUM. hydrochloric acid and evaporation to dryness will serve to sepa- rate out the silicon as silica. If dissolved in hot nitric acid, the tin remains in the residue as metastannic acid, which can be ignited along with any silica remaining and weighed as stannic oxide. The silica is left on treating this residue with hydro- chloric or sulphuric acid, and its weight being subtracted from the previous weighing gives the net weight of stannic oxide. Lead would be precipitated from the nitris acid solution filtered out above by nearly neutralizing the solution and adding a few drops of sulphuric acid. The precipitated lead sulphate is filtered out and weighed. Copper may be precipitated free from zinc, iron or aluminium by evaporating the last filtrate nearly to dryness, to drive off" nitric acid, acidulating with hydrochloric acid and precipitating with sulphuretted hydrogen. The precipitate of cupric sulphide may be mixed with sulphur and ignited in a Rose crucible in a current of hydrogen and weighed as cupric sulphide. Or, it may be dissolved in a few drops of nitric acid (the least possible quantity), a few centi- metres of sulphuric acid added and the solution electrolyzed. The electrolysis of the solution can also be made directly in the presence of iron and aluminium by using a sulphuric acid solu- tion with only two or three drops of free nitric acid present. The precipitation of copper by.the battery is advisable in many respects, since the copper is simply removed from the solution without leaving any reagent behind it, and the other metals can be easily separated out of the solution remaining. If the copper has been removed, either by sulphuretted hy- drogen or by the battery, the solution contains only iron, alu- minium, zinc, nickel or manganese. In the first case, it must be oxidized by a little nitric acid and the precipitated sulphur separated out. The metals remaining can be separated in sev- eral ways ; the best, however, is to precipitate the iron and alu- minium as basic acetates. To do this the solution is neutral- ized with carbonate of soda until a faint precipitate forms, which redissolves only after two or three minutes' stirring. Dilute, add about 4 per cent, of acetic acid and excess of sodium ace- ANALYSIS OF ALUMINIUM. 625 tate. Boil two or three minutes and then let the precipitate settle. Wash quickly with boiling water containing a little so- dium acetate. The filtrate contains all the zinc, manganese, cobalt or nickel which were in the solution. The precipitate can be dissolved in dilute hydrochloric acid and the iron and alu- minium separated by any of the methods already given, prefer- ably Peter's modification of Chancel's separation. The filtrate may be evaporated to dryness, taken up with hydrochloric acid, sodium carbonate added till a permanent precipitate just forms, and then a drop or two of hydrochloric acid added to re- dissolve this precipitatCj On passing sulphuretted hydrogen through the solution the zinc is precipitated as sulphide, while any manganese, nickel or cobalt present remain in solution. When all the zinc is precipitated, allow to stand twelve hours, filter, wash with sulphuretted hydrogen water, re-dissolve in hydrochloric acid and throw down the zinc as carbonate by sodium carbonate and ignite to oxide; or the zinc sulphide may be mixed with sulphur, put in a Rose crucible and ignited in a stream of hydrogen sulphide. It is in this case weighed as sulphide. If the solution from which the zinc has been precipitated and filtered out be made strongly acid with acetic acid, and excess of sodium acetate added, sulphuretted hydrogen may be passed through again and will precipitate nickel or cobalt sulphides. These are filtered out and the filtrate concentrated, ammonium sulphide added to it, and then acetic acid. The remaining nickel and cobalt will be precipitated. The two precipitates are united and the nickel (and the cobalt if present) determined by any of the ordinary methods of precipitation. The filtrate is neutralized with ammonia, ammonium chloride added and let stand at least 24 hours in order to precipitate out the manga- nese as sulphide. Manganese might also be separated out of the filtrate from the basic acetate separation by adding hydro- chloric acid and boiling with bromine water. The manganese is completely precipitated as dioxide. If it is not wished to determine the copper, but only the alu- 40 626 ALUMINIUM. minium present, the copper can be easily removed by adding a slight excess of ammonia to the hot hydrochloric acid solution. The solution is boiled a few minutes and filtered. The precip- itate is apt to carry down and retain some copper. It is there- fore necessary to re-dissolve it in acid and repeat the precipita- tion. All the iron and aluminium are thus obtained in the precipitate, along with manganese and possibly some zinc and nickel, if these are present. The precipitate can be dissolved in hydrochloric acid and the iron and aluminium precipitated alone by a basic acetate separation. Aluminium-Zinc Alloy. The writer has several times had occasion to search for mi- nute quantities of aluminium in zinc. The method which gave complete satisfaction was as follows : Dissolve in nitric acid, and separate out tin. Add sulphuric acid and separate out lead. Make a basic acetate precipitation, and filter out the pre- cipitated iron and aluminium. Dissolve in hydrochloric acid, and precipitate the alumina with sodium hyposulphite, pre- ferably adding sodium phosphate if the latter reagent on hand is free from alumina. Using a large quantity of zinc for the analysis, two analyses gave 0.004 srid 0.005 P^i" cent, of alu- minium respectively, while a blank analysis to correct for alu- mina coming from the reagents used gave absolutely nothing. General Remarks. In analyzing aluminium-tin alloys, hot nitric acid will dis- solve the aluminium and leave the tin as meta-stannic acid. Aluminium-silver alloys may be attacked by caustic alkali, leaving silver undissolved in the residue, or may be dissolved in hot nitric acid, nearly neutralized and the silver precipitated by hydrochloric acid or sodium chloride. Alloys of aluminium with either zinc, nickel or manganese are best analyzed by bringing the alloy into solution and separating aluminium from the other metal by a basic acetate precipitation. Aluminium- lead alloys may be dissolved in hot nitric acid and the lead ANALYSIS OF ALUMINIUM. '. 62/ precipitated by sulphuric acid after, nearly neutralizing the so- lution and adding alcohol to it. I would recommend that some qualitative tests such as are suggested in the beginning of this chapter — blow-pipe tests, wet tests, etc. — be always made preparatory to the quantitative analysis ; and then, knowing what is present and which ele- ments it is desired to estimate and which to neglect, the method of attack and analysis should be decided on. Half an hour spent in making qualitative tests and ten minutes in re- flection as to the best method of analysis to adopt, will often save several hours of unnecessary work, and frequently prevent the exasperating necessity of having to stop an analysis and start over again. INDEX. ACETYLENE, heat absorbed in the formation of, 241 pure, cost of, 242 theoretical temperature at which alumina should be reduced by, 241 Acid element, action of aluminium as an, 99 hydrochloric, action of, on alu- minium, 91, 92 nitric, action of, on aluminium, 90,91 resistance of aluminium to,488 sulphuric, action of, on alumin- ium, 88-90 Acids, organic, action of, on alumin- ium, 92-97 Adamson, Mr., on the use of ferro- aluminium, 604 Air, action of, on aluminium, 83-85 -ships, use of aluminium in, 478 Alabama, deposits of bauxite in, 41 kaolin in, 49 Alkali Reduction Syndicate, Limited, 32 Alkalies, caustic, action of, on alu- minium, 99, 100 double carbonate of aluminium and the, 131 Alkaline carbonates, reaction of, on neutral solutions of alu- minium salts. 111 chlorides, solutions of, action of aluminium on, 102 j metals, reduction of, theoretically I considered, 237 I sulphates and carbonates, action | of, on aluminium, 104 Allegheny river, aluminium works on ' the, 382 I Alliance Aluminium Co., London, England, 31, 32 ' cost of aluminium to i the, 294 ; plant of, 291 ] Alloy, carboniferous, of aluminium, 403 Alloy, light, elastic, of aluminium, 538 Miller's anti-friction, 504 Alloys, aluminium, 492-533 analysis of, 606-627 aluminium-antimony, 495, 496 -arsenic, 497 -bismuth, 497 -boron, 497, 498 -cadmium, 498 -calcium, 498, 499 -chromium, 499, 500 -cobalt, 500 -copper, 534-571 general properties of, 534-536 groups of, 534 melting points of, 534-536 -gallium, 500, 501 -gold, 501-503 groups of, 493 -iron, 572-605 -lead, 503, 504 -magnesium, 504, 505 -manganese, 505, 506 analysis of, 626 -mercury, 506-509 -molybdenum, 509, 510 -nickel, 510, 511 analysis of, 626 -copper, 511-516 -phosphorus, 516, 517 -platinum, 517 practical production of, 492 -selenium, 519 -silicon, 517-519 -silver, 519-521 analysis of, 626 -sodium, 52] specific gravity of, 494 -tellurium, 521, 522 -tin, 522-525 analysis of, 626 -titanium, 525-527 -tungsten, 527 -zinc, 528-530 analysis of, 626 -copper, 530-533 (629) 630 INDEX. Alloys, for soldering aluminium, 461, 462, 464, 465 iron-alumiuium, Brin Bros', pro- cess of preparing, 425 Cleaver's patent for pro- ducing, 424, 425 Faraday and Stodart's investigations on, 422, 423 ' preparation of, by an alu- min ium compan y in Ken- tucky, 425, 426 by the Alumin- ium Process Co., 426, 427 ready-made, decline of the sale of, 31 Almeta polish, composition of, 456 Alsite Aluminium Solder, 467 Alum and vitriols, separation of, 2 calcined, 128 discovery of process of obtain- ing, 2 ignition of, with carbon, 403 j investigations on the base of, 2 [ native, analysis of, 50, 51 Alumen, account of, by Pliny and Columella, 1 derivation of the term, 1 Roccas, 1 Alumina, 112 action of carbon-bisulphide on,244 addition of, in the manufacture of cast steel, 423 amorphous in aluminium, 59 amount of metal extracted from, by the Hall process, 379 Billing's experiment on reducing, in contact with iron, 424 change of, into its chloride, 242 conditions required for the re- duction of, 238 i cost of calcination of, 379 in Pittsburg, 379 data for the decomposition of, 239 : Davy's experiment to decompose, 1 319 ' decomposition of, by the electric current, 5 ! effect of, on steel, 577 1 electro-motive force required to decompose, 302 equation for the temperature at which hydrogen gas will begin to reduce, 240 Alumina, equation for the voltage re- quired to decompose, 239 formula for finding the tempera- ture at which reduc- tion of, by carbonic oxide begins, 240 the heat required to de- compose, 239 hydrated, precipitation of, 133 impossibility of the reduction of, by the ordinar3' reagents, 230 liquefaction of, 231 rnanufacture of, by Bergius, 379 native sulphate of, 50, 51 not reduced by sodium or potas- sium, 230 occurrence of, in plants, 39, 40 preparation of, for reduction, 133- 152 reduction of, by carbon, 231,240, 241,415 hydrogen, 231, 240, 241, 407 magnesium, 229, 230, 437, 438 theoretical aspect of the reduc- tion of, 229 temperature at which acety- lene should begin to re- duce, 24J various names for, 2 Aluminate of soda, precipitation of alumina from, 143 Aluminates, 109, 110 properties of the various, 114,115 Aluminite, 127 Aluminium, action of air on , 83-85 alkaline sulph- ates and car- bonates on,104 ammonia on, 100 bromine on, 106 caustic alkalies on, 99, 100 chlorine on, 106 cryolite on, 103 fiuorine on, 106 fluorspar on, 102, 103 hj-drochloric acid on, 91, 92 hydrogen on,106 iodine on, 106 lime water ou, 100 nitre on, 104 nitric acid on, 90,91 INDEX. 631 Aluminium, action of on baryta, 105 carbonic ox- ide, 106 copper oxide, .105 solutions, 101 ferric oxide, 105 lead oxide, 105 solutions, 101,102 manganese di- oxide, 105 oxide, 436 mercu reus chloride, 106 mercury solu- tions, 101 metallic o x - ides, 105, 106 silver c h 1 o - ride, 106 solutions of al- uminium salts, 102 of metallic chlorides, 102 zinc oxide, 105 solution, 102 organic acids, vinegar, etc., on, 92- 97 secretions on, 98,99 phosphate of lime on, 106 sea-water on, 97, 98 silicates andbor- ateson,103,104 silver solutions on, 101 sodium chloride on, 97,98 solutions of me- tallic salts on, 100-102 sulphuric acid on, 88-90 water on, 85, 86 < alloys, 492-533 Bamberg's method of pre- paring, 427 Aluminium alloys, groups of, 493 H^roult's process of producing, 388 practical production of, 492 amalgam, preparation of, 507 properties of, 508, 509 1 -ammonium chloride, 117, 118 amorphous alumina in, 59 amount of, produced, 35-38 analyses of, 53-56 and specific gravities of, 63 and aluminium alloys, analysis of, 606-627 carbon, 123-125 nickel, electro-deposition of an alloy of, 31 1 sodium, double sulphide of, 177 anhydrous silicates of, 49 annealing of, 452 antimonate, 130 -antimony alloys, 496, 496 apparatus for obtaining, 311 -arsenic alloys, 497 articles, polished, tarnishing of, 98, 99 as a base and as an acid, 109 atomic weight of, 83, 301 basic salts of, 110 Basset's process for obtaining, 429-431 bell cast of, 67, 68 Benzon's patent for the reduction of, 414, 415 Bessemer's process for producing, 404, 405 -bismuth alloys, 497 borate, 131, 132 bolides, 122, 123 -boron alloys, 497. 498 boron-carbide in, 59 Brass and Bronze Co., of Bridge- port, Conn., 28 brasses, 530-533 forging capability of, 533 tests of, 531 , 532 Braun's process for depositing, 310, 311 bromide, 118 heat developed in the forma- tion of, 232 bronze, annealed, resistance of, 560 brazing of, 569 Brin's process for producing, 417,418 casting of, 548-552 632 INDEX. Aluminium bronze, Clark's patents for preparing, 434 dilution of a high per cent., to a lower one, 547 Evrard's process for producing, 414 Faurie's process for preparing, 415, 416 Hampe's experiments in producing, 290 history of the applica- tion of, 539 Mann's patent for pro- ducing, 417 mechanical properties of (6per cent.), 537 prices of, 35 soldering of, 569, 570 bronzes, 538-571 analysis of, 623-626 annealing and hardening of, 561 anti-friction qualities of, 563, 664 color of, 552, 553 compressive strength of, 554, 555 conductivity of, 564 constitution of, 540-545 diagram of the variation of tensile strength and elong- ation of, 559, 560 fusibility of, 548 hardness of, 553, 554 melting points of, 548 preparation of, 545-547 prices of, 539, 540 resistance of, to corrosion, 564-567 role of aluminium in, 542, 543 specific gravity of, 553 tensile strength of, 555-561 transverse strength of, 554 uses of, 567-569 working of, 561, 562 Bucherer's process for producing, 400, 401 Bull's process of manufacture, 314 Burghardtand Twining's process for depositing, 314, 315 burning of, 84, 85 cab, 478 -cadmium alloys, 498 -calcium alloys, 498, 499 Calvert and Johnson's experi- ments on the reduction of, by iron, 420, 421 Aluminium carbide, process of prepar- ing, 124 properties of, 124, 12.5 carbon required for the produc- tion of, 378 carbonate, 131 carboniferous alloy of, 403 casting of, 445-447 castings, hardening of, 453 chemical equivalent of, 301 chemically pure, preparation of, 451 chloride, 115, 116 and aluminium-sodium chlo- ride, preparation of, 152- 168 anhydrous, preparation of, 152 apparatus for the continuous electrolysis of, 354 preparation of, used at Salin- dres, 157-159 calculated difference of po- tential, for the dissociation of, 369 calories required for the de- composition of, 369 Deville's methods of reduc- ing, by sodium, 252-257 electro- motive force necessary to decompose, 302 graphic formulae of, 108, 109 heat developed by the com- bination of some of the elements with, 232 heat for formation of, 242, 243 inconveniences of the reduc- tion of, 275 molten, decomposition of, .398 or aluminium-sodium chlo- ride, methods based on the reduction of, 246-300 purification of, 156, ].57 reduction of, by battery, 10 by magnesium, 437 by tin, 439 the vapor of, b)' zinc, 435 voltage required to decom- pose, 238 -chlorphosphydride, 118 ■chlorsulphydride, 118 -chromium alloys, 499, 50O INDEX. 633 minium, cleaning and pickling of, Aluminium compounds, Monckton's 456 patent for reducing. clippings, filings, etc., melting by the battery, 3k5 of, 442, 443 Netto's process of re- coating iron work of the tower ducing, 290-294 of the Philadelphia Public Oersted's experiments Buildings with, 316, 317 in reducing, 246, 247 metals with, H07, 308, 469-472 Percy and Dick's ex- -cobalt alloys, 500 periments in reduc- color of, 59, 60 ing, 283-285 combinations of, 39 preparation of, for re- Comenge's process for producing, duction, 133-178 411 properties and prepar- commercial, average strength of. ation of, 107-132 73 reduction of, by electri- carbon in, 57, 58 city ,236, elements to be sought for in, 301-401 606 by means impurities in, 52 of po- nitrogen in, 58, 59 tassium testing of, with the knife, 62 and so- Co., Ivimited, bronzes containing dium, nickel made by the. 246-300 512-515 by Nie- incorporation of the, 23 werth ' s works of the, 212, 270, process. 271 268 Neuhausen, sheet aKiminium by other made by the, 465, 466 means comparison of actual and atomic than so- specific heats of, 80 d i u m of production of, with other and el- metals, 38 ect rici- compounds, appearance of, 40 ty, 402- jehavior of, before the blow- 441 pipe, 111 from the Deville's experiments in re- stand- ducing, 250-252 point of methods of reducing. thermal 285-287 c hemis- Deville-Castner process for try,226- the reduction of, 270-273 245 formulse of, 40 Minet 's Frishmuth's process for the views reduction of, 269,' 270 on the. Gadsden's patent for the re- 358 duction of, 269 Rose's experiments in general methods of formation reducing, 274-283 and properties of, 110, 111 structure of, 108-110 Gerhard's furnace for the re- Thompson and White's duction of, 289 patent for the reduc- Grabau's process of reducing. tion of, 290 294-300 Tissier Bros', method Grousillier's improvement of reducing, 287, 288 in the reduction of, 270 voltage required to de- Le Chatellier's method of compose, 237 reducing, by the battery. Wohler's experiments 324, 325 in reducing, 247-250 634 INDEX. Aluminium, compressive tests of, 72 cooking utensils, advantages of, 485, 486 -copper alloys, 534-571 general properties of, 534r-53(i groups of, 534 melting points of, 534- 536 Corbelli's patent for producing, 410 process for depositing, 308 corrosion of, 84 cost of, 379, 380, 381, 382 by the Deville process, 267, 268 -Castner pro- cess, 273 H&roult pro- cess, 397 by Netto's processes, 294 Cowles Bros', process of produc- ing, 329-347 Crown Metal Co., 22 crucibles for melting, 103, 104 crystalline form of, 69 crystallization of, 282 cyanide of, reduction of b}' zinc, 433, 434 decomposition of silver sulphide by, 87 decorations of, 479 density of, increa.sed by being worked, 63 dental plates, action of saliva on, 98 deposition of, from aqueous solu- tion, 307-318 determination of, in aluminium bronze, 624 does the, remain in iron castings ? 598, 599 drawing of, 454 ductility of, 76. 77 dust, 76 earl}' production of, by electro- lytric methods, 11 effect of alloying on the color of, 493 carbon on the physical properties of, 58 nitrogen on, 58, 59 on steel, 575-581 on wrought-iron, 581-595 purity of, on the amount of heat in, 80 effects of impurities in, 52 elasticity of, 69, 70 Aluminium, electric conductivity of, 81,82 electro-chemical equivalent of, 301 -deposition of, various pat- ents for, 315 Emanuel's process for producing, 406 engraving of, 456 exhibit at the Columbian Expo- sition in Chicago, 1893, 34 of, at the Paris Exposition, 1855, 13 expansion of, by heat, 77 Farmer's patent for producing, 347 Faure's proposition to obtain, 398, 399 Feldman's method of producing, 362, 363 -ferro-silicon, claims for, 595, 596 manufacture of, 427 films, color of, by transmitted light, 60 first article made of, 13, 474, 475 experimenter on the isolation of, 3 Fleury's process for producing, 408 fluorhydrate, 120 fluoride, 119 affinity of, for sodium fluor- ide and potassium fluoride, 275 and aluminium-sodium fluor- ide (cryolite), preparation of, 168-173 reduction of, 235 by sodium, 294-300 fracture of, 60, 61 freeing of, from impurities, 449-452 fusibility of, 65, 66 fusion of, latent heat of, 79,80 -gallium alloys, 500, 501 gases in, 57 Gaudin's patent for reducing, 325 Gerhard's process for producing, 406, 407 -gold alloys, 501-503 Gore's process for depositing, 308, 309 Grabau's apparatus for produc- ing, 364, 365 process of producing, 400 Gratzel's process of producing, 326-329 Green's process of producing, 409, 410 INDEX. 635 Aluminium, grinding, polishing and burnishing of, 455, 456 Hall's process of producing, 372- 386 hardening of, 452, 453 hardness of, 61, 62 heat generated by the combina- tion of, with the different elements, 228 required to melt, 81 Hferoult's process of producing, 386-398 high value of the specific heat of, compared with other metals, 81 history of, 1-38 hollow-ware, cast, for culinary use, 447 hydrates, 113 -hydrogen fluoride, 120 immense future of, 474 improving the quality of, 449 impure, phenomena in melting, 442 purifying of, 295 Industrie Actien Gesellschaft, 30 organization and plant of, 393, 394 patent of the, 401 industry at the Paris Exposition, 1889, 33 in 1859, 263. 264 possible lines of improve- ment in the, 20 progress in the, 33, 34 reactions of use in the, 242- 245 revolutions in the, 24 statistics of the, 34-38 \V. Weldon on the prospects of the, 20, 21 influence of, in puddling iron, 594, 595 flux or slag on the, 253 on cast-iron, 595-605 the vessel on, 253 in the soot from Cowles Bros'. furnace, 343 iodide, 118, 119 heat developed in the forma- tion of, 232 -iron-alloys, 572-605 melting point of, 588 isolation of, 8 Jeancon's process for depositing, 309, 310 kaolin the natural ore of, 49 Aluminium, Kagensbusch's process of reducing, 325 Kleiner's process for producing, 347-353 Knowles' patent for producing, 410 latent heat of fusion of, 79, 80 -lead alloys, 503, 504 leaf, 76 beating and tempering of, 454 decomposition of, in water, 86 superiority of, 479 Lebedeff's process of producing, 409 loss of, by oxidation during re- duction, 280, 281 Iiossier's method of producing, 353, 354 -magnesium alloys, 504, 505 magnetism of, 67 malleability of, 75, 70 -manganese alloys, 505, 506 analysis of, 626 mat on, 456 mechanical tests of, by the Pitts- burgh Reduction Co., 7(1-72 value of, 74 melted, improvement in, b}' blow- ing air into it, 451 melting of, 442-445 point of, 65, 66 Menge's patent for producing, 347 -mercury, alloys of, 506-509 metallic, occurrence of, 39 sulphates, 129 meta-phosphate, 131 method of obtaining, patented by H. A. Gadsden, 164 military uses of, 475, 476 Minet's electrolytic process of producing, 354-362 miscellaneous uses of. 490, 491 molten, absorption of gases by, 57 peculiarity of, 446 -molybdenum alloys, .509, 510 Montegelas' patents for deposit- ing, 312, 313 Morris' process for producing, 405, 406 naval use of, 476-478 necessity of using pure materials in the production of, 252 -nickel alloys, 510, 511 alloys, analysis of, 626 -copper alloys, 511-516 636 INDEX. Aluminium, Niewerth's patent for the reduction of, by iron, 418, 419 process for producing, 411- 413 nitrate, 130 nitride, 125, 12(5 non-aqueous electric processes of depositing, 318-401 normal and neutral salts of, as a base, 110 object of alloying, 493 objections to the term. 5, occurrence of, in nature, 39-51 odor of, 66, 67 origin of the term, (i output of, by the Hall process, 383 Overbeck and Niewerth's process for depositing, 311, 312 oxidation of, 84, 85 oxide, 112 graphic formulae of, 108, 109 passementerie, 76 Pearson, Liddon and Pratt's pat- ent for producing, 404 percentage of, in the earth's crust, 39 perfectly pure, Deville's method of obtaining, 252 Petitjean's process for produc- ing, 408, 409 phosphates, 130, 131 -phosphorus alloys, 516, 517 chloride, 117 physical properties of, 52-82 plating of, on copper, 323, 324 on, 472, 473 -platinum alloys, 517 position of, in the periodic clas- sification of the elements, 107, 108 powder of, influence of pressure on, 66 precipitation of, by magnesium, 437 prices of, 14, 15, 17, IS, 20, 35 Process Co., of Washington, D.C., iron-aluminium alloys manu- factured by, 42(>, 427 proportion of, extracted from cryolite, ,351 pure, HSroult and Kiliani's ap- paratus for producing, 394 impossibility to manufacture, direct from minerals con- taining silica, 103 purest commercial, analysis of, 451 Aluminium, purification of, 447-452 purity of, produced by Kleiner's process, 352, 353 quality of, produced by Minet's process, 361 racing sulkies, 478 railway carriage, 478 rationale of the action of, on cast iron, 605 reaction according to which cry- olite dissolves, 372 reasons for blue tint of, being more prominent after working the metal, 60 its being difficult to solder, 457, 458 reduction of, in the iron blast furnace, 429 Reillon, Montague and Bourger- el's patent for producing, 409 Reinbold's recipe for depositing, 312 relative cost of materials in mak- ing, 20 removing discoloration from arti- cles of, 60 researches of H. St. Claire De- ville on, 9-16 retrospect of the art of working, 18, 19 Rogers's process of producing, 365-368 rolling of, 453, 454 salts, decomposition of, in aque- ous solution, 304 reactions of neutral solutions of, HI solutions of, action of alu- minium on, 102 second quality, analyses of, 381 selenide, 122 selenites, 129, 130 -selenium alloys, 519 chloride, 117 vSenet's process for depositing, 311 Seymour's patent for the reduc- tion of, by zinc, 432, 433 silicates, 132 -silicon alloys, 517-519 silver, 516 alloys, 519-521 analysis of, 626 -sodium alloys, 521 chloride, 116. 117 and aluminium chloride, preparation of, 152-168 INDEX. 637 Aluminium-sodium chloride, Bunsen 's and Deville's methods of de- composing, by the battery, 320-324 cost of, 159, 164 largest plant erected for the manufacture of 159-162 method of pre- \ paring, 278. I 279 ■ j quantities of ma- terials used in the prepara- j tion of 163 o r aluminium chloride.meth- ' ods based on 1 the reduction i of, 246-300 j reduction of, by | sodium, 265-268 I by zinc, 429 fluoride, 120, 121 (cr3-olite) and alu- minium fluoride, preparation of, 168-173 lining of, 296 soldering of, 457-469 solution of, by molten cryolite,371 sonorousness of, 67-69 specific gravity of, 62-65 when molten, 386 heat of, 77-81 stamping and spinning of 455 suitability of, for culinary uten- sils, 96, 97 sulphate, 126, 127 or alunjs, preparation of alumina from, 133-137 sulphide, 121, 122 decomposition of, by anti- mony and carbon, 438 electrolysis of 400, 401 heat for combination of, 244 Lisle's experiments in reduc- ing, by zinc, 435 preparation of, 174-178 reduction of, by copper, 417 iron, 418 thermal relations of, 2.S5, 236 voltage required to decom- pose, 238 Aluminium-sulphur chloride, 117 superiority of, for constructions, 75 taste of, 67 -tellurium alloys, 521 , 522 tendency of, to absorb gas, 452 tensile and compressive strength of 70-75 strength of, affected by an- nealing, 74 tests of, 7] thermal conductivity of, 82 Thompson's process for deposit- ing, 308 manufac- ture of, 419,420 Thowless' proposition to pro- duce, 403,404 -tin alloys, 522-525 analysis of, 620 melting points of, 524, 525 -titanium alloys, 525-527 torpedo boat of, 477 transverse tests of, 72 tri-valency of 109 . tubes, manufacture of, 454 -tungsten alloys, 627 und Magnesium Fabrik at Hem- eliugen, 24 Magnesium Fabrik, tests of aluminium brass by the, 532 Magnesium Fabrik, works of the, 328 use of, for batteries, 487, 488 chemical apparatus, 484, 485 coinage, 483, 484 constructions, 487 culinary utensils, 485, 486 flash light powder, 489. 490 lithographic plates, 488, 489 ships, 97, 98 sounding boards, 68, 69 table ware, 486, 487 in aerial navigation, 478 German army, 96 Grove's batterj', 91 surgery, 98 uses of, 473-491 vapor, color of 66 variations in Rose's process of preparing, 279 638 INDEX. Aluminium, velocity of sound in, 69 volatilization of, 66 Walker's patents for the electro- deposition of, 313, 314 Warren's experiments in produc- ing, 363, 364 welding of, 457 Willson's process for producing, 399 Winckler's patent for producing, 399 ■wire, 76, 77 annealed, tensile strength of, 73 tests of strength of, 70 worked and annealed, strength of, 74 working in, 442-491 world's production of, 37, 38 Zdziarski's patent for producing, 364 -zinc alloys, 528-530 analysis of, 626 batteries, 488 -copper alloys, 530-533 Aluminous earths, manufacture oi aluminium sulphate from, 127 fluoride slags, utilization of, 148, 149 pig iron, 414 Alumin-um, 6 Alums, 128, 129 or aluminium sulphate, prepa- ration of alumina from, 133-137 Alunite, 128 Amalgam, aluminium, preparation of, 507 properties of, 508, 509 American Aluminium Co., of Mil- waukee, experiments of, 365-367 organization of the, 432 Amfreville, works at, 14 Ammonia, action of, on aluminium, 100 alum, 128, 129 Ammonium and aluminium, chloride of, 117 reaction with, of neutral solutions of aluminium salts. 111 Ampere, decomposing power of a current of one, 301, 302 Analysis of alumiuium and alumin- ium allovs, 606-627 -zinc alloy^ 626 quantitative, necessity of being preceded by a qualitative anal- ysis, 627 Andalusite, 49 Anderson, W., on the sodium works at Oldbury, 212-215 tests by, of the strength o f aluminium bronze, 554, 555, 556 Andrews, G. F., on aluminium-gold alloys, 501,502 on al uminium- nickel-copper al- loys, 516 Anhydrous aluminium sulphate, 126 Annealing aluminium, 452 and hardening aluminium bronzes, 561 Anti-friction alloy. Miller's, 504 qualities of aluminium bronzes, 563, 564 Antimonate of aluminium, 130 Antimony and aluminium, alloys of, 495, 496 reduction hy, 438 Aqua ammonia, reaction with, of neutral solutions of aluminium salts. 111 Arc, electric, reduction of disthene in the, 319 Argil, 2 Arkansas, deposits of bauxite in, 41 Arsenic and aluminium, alloys of, 497 Atomic weight of aluminium, 83 Austria, deposits of bauxite in, 41 BAILLE and FSry on aluminium amalgam, 507, 508, 509 Balances, alloy for beams of, 520 Balland, tests by, of the action of or- ganic acids on aluminium, 94 Bamberg, G., alloys of aluminium prepared by, 427 claims of, 435 Barium aluminate, 114, 115 salts, voltage required to decom- pose, ^37 Barlow, W. H., on the tensile strength of aluminium, 70 Baron, experiments of, on the isola- tion of aluminium, 3 Baryta, action of aluminium on, 105 Base, action of aluminium as a, 109 Basic aluminium sulphate, 127 Basle, projected aluminium works near, 395 Basset, M. N., process of, for obtain- ing aluminium, 429-431 Bath, electrolytic, decomposition of a, 306 Hall's, specific gravities of the substances used in, 386 INDEX. 639 Bath-tubs, 447 Baths, composition and properties of the, used in Minet's process, 357, 358 Batteries, use of aluminium for, 487, 488 Battersea, aluminium works at, 18 Battery, Grove, use of aluminium in the, 91 use of, by Deville and Bunsen,in decomposing aluminium com- pounds, 320-324 Baudrin, P., alloy of, 512 Baur, J., alloys of, 531 Baux, bauxite from, 44 Bauxite, 40-45, 113 American, analyses of, 43 cost of, 41, 42 foreign, analyses of, 42, 43 French, composition of the typi- ical kinds of, 44 important beds of, 41 imported, cost of, 41 Ivaur's process of calcining, 143 manufacture of aluminium sul- phate from, 127 preparation of alumina from, 137-144 reaction of common salt on, 142 red, 44 Bauxites, American, analyses of, 45 constancy of the titanic acid in, 45 Bayer, Dr. K. J., improvement in the process of extracting alumina from bauxite by, 143, 144 Beams, deck, of aluminium, 47S Beer, action of, on aluminium, 95, 96 Behuke, process of, for preparing alumina, 141 Beketoff, M., experiment of, 429 Bell Bros., aluminium plant of, 18 on drawing aluminium, 454 on Mourey's solders for alu- minium, 461 Lowthian, experiment of, 410, 411 Bells, aluminium, 67 Benzon, patent of, 414, 415 Bergius, alumina manufactured by, 379 Berlin, Germany, aluminium works at, 18 Bernard Bros., operation of Minet's process by, 361 works of, 26 Berthaut's proposition, 326 Bertrand, M. A., electro-deposition of aluminium by, 310 Beryllium aluminate, 115 Berzelius, experiments of, 6, 7 process for preparing artificial cryolite, recommended by, 169 i Bessemer, H., Jr., process of, 404,405 ' steel, eflfect of aluminium on, 578 ; Bicycles, use of aluminium for, 478 ! Biederman, R.,directionsby, formelt- j ing aluminium, 443 on polishing alumin- ', ium, 455 on the preparation of alumina, 148 Billings, G. H., alloy of aluminium and carbon of, 575 experiment of, 424 Bismuth and aluminium, alloys of, 497 Blackmore, H. S., process of obtain- ing sodium, patented by, 203 Blair, A. A., method of determining aluminium in iron and steel, recommended by, 621, 622 on aluminium in steels, 575 Blast-furnace, occurrence of spinel in the slags of, 115 reduction of aluminium in the, 423, 429 Blow-holes, causes of, in wrought- iron castings, 590-592 Blowpipe, behavior of aluminium compounds before the. 111 Boats, tests of the suitability of alu- minium bronze for, 566 Boisbaudran, L. de, on aluminium- gallium alloys, 500, 501 Bolley, experiment of, 416 Bombay wootz steel, 422, 576 Boonton, N. J., works at, 31, 396 Borate of aluminium, 131 Borates and silicates, action of, on aluminium, 103, 104 Bornemann, Dr. G., on the use of al- uminium for chemical apparatus, 484, 485 Boron-aluminium bronze, 571 and aluminium, alloys of, 497, 498 compounds of, 122, 123 carbide in aluminium, 59 Bourbouze, M., on aluminium-tin al- loys, 522 ' process of, for sol- dering aluminium, 463 Braces, aluminium, 480 Bradley and Crocker, retort, patented by, 332, 333 640 INDEX. Brandy, action of, on aluminium, 95 Brass, aluminium-tin alloy as substi- tute for, 522 depositing aluminium on, 308,309 plating aluminium on, 469, 470 with, 473 Brasses, aluminium, 530-533 forging capability of, 533 tests of, 531, 532 Brauu, J., process of, for depositing aluminium, 310, 811 Brazing aluminium bronze, 569 Bridgeport, Conn., works at, 31, 396 Brin Bros., preparation by, of iron- aluminium alloys, 425 process of, for coating metals with aluminium, 471 Iv. Q., process of, 417,418 Broadwell, H. C, process of, for coat- ing sheet-iron with aluminium, 471,472 Bromide of aluminium, 118 Bromine, action of, on aluminium, 106 Bronze, analysis of a peculiar product formed in the furnace when smelting for, 342 slags formed in pro- ducing, 342, 343 boron-aluminium, 571 Cowles Bros., analyses of, 341 plating aluminium with, 473 phosphor-aluminium, 571 Richards', 533 silicon-aluminium, 570, 571 1 standard grades of, produced by . the Cowles Co., 341 Bronzes, aluminium, 538-571 containing nickel patented by J. Webster, 512-515 i Brown, Lieut., experiments on alu- minium for military use, 476 Bruner, process of, for preparing alu- minium fluoride, 170 i Briinner, experiments of, in making | sodium, 180 method of, for making aluminium fluoride, 119 Brush dynamo, dubbed the ' ' Colos- sus," 339 Bucherer, process of, 400, 401 Buchner, G., on the treatment of alu- minium containing silicon, 450 Buff-Dunlap washing apparatus, 147 Bull, H. C, manufacture of aluminium proposed by, 314 Bullion, de-silverization of, by alu- minium, 503 Bunsen and Deville, methods of, for decomposing aluminium-sodi- um chloride by the battery, 320-324 isolation of aluminium by elec- trolysis by, 11 Burghardt and Twining, process of, for depositing aluminium, 314, 315 Burnishing, polishing and grinding aluminium, 455, 456 Butter, action of, on aluminium, 94 CAB, aluminium, 47S Cadmium and aluminium, alloys of, 498 Cailletet on the amalgamation of alu- minium, 506 Calcined alum, 128 Calcium aluminate, 115 and aluminium, alloys of, 498, 499 Calvert and Johnson, experiments of, on the reduction of aluminium by iron, 420, 421 on aluminium-iron alloys, 573 process of, 413, 414 Candelabra, aluminium, 479 Canteens, aluminium, 475, 476 Carbon, action of, on alum, 403 and aluminium, 123-125 carbon dioxide, reduction by, 405, 406 bisulphide, heat of formation of, 245 reaction of, on alumina, 245 consumption of, in Hall's pro- cess, 378 determination of, in aluminium, 616 dioxide, preparation of, 147 effect of, on the physical proper- ties of aluminium, 58 formula for expressing the heat in, 240 in aluminium, 53 non-wetting of, by molten cryo- lite, 324 oxysulphide, heat of formation of, 245 presence of, in commercial alu- minium, 57, 58 reduction by, without the pres- ence of other metals, 402- 405 of alumina by, 231 , 240, 241 in the presence of copper,415 INDEX. 641 Carbonate of aluminium, 131 Carbonates, alkaline, action of, on al- uminium, 104 Carbonic acid gas, precipitation of alumina by, 147, ]4« oxide, action of aluminium on 106 formula for finding the tem- perature at which reduction by, of alumiua begins, 240 the heat of formation of, 240 Carburetted hydrogen, reduction by 408-410 Carhart, Prof, on the thermal con- ductivity of aluminium, 82 Caruelly, Prof, on the influence of iron on the melting point of alu- minium, 572, 573 Carroll, Dr. C. C, alloy of, for dental plates, ri'IO mode of casting al- uminium by, 446 Casting aluminium, 445-447 bronze, 548-552 Castings, aluminium, addition of zinc and copper to. 529 effect of copper on, 537 cast-iron, solidity ol, 597 iron, effect of the addition of ferro- aluminium on. 59f> mitis, absence of aluminium in, 587 history of, 582, 583 mixture for, 584 production of, 583 properties of, 586, 5S7 rationale of the process of making, 587-594 raw material for, 583-585 strength of, 587 sharp, of aluminium, 446 wrought iron, causes for blow- holes in, 590-592 Cast-iron, aluminium in, 423 aluminized, shrinkage of, 602, 603 castings, solidity of, 597 increase in the hardness of, by aluminium, 603 influence of aluminium on, 595-605 rationale of the action of alu- minium on, 605 Cast steel, addition of alumina in the manufacture of, 423 Castner, H. Y., invention of, 22-24 41 Castner, H. Y., process, amount of alu- niinium pro- d u c e d by the, 36 of, for the manu- facture of so- dium, 203- 217 for the reduc- tion of so- dium com- pounds by electricity, 223-225 for removing iron from al- um i n ium- sodium chlo- ride, 163 reduction of alumin- ium by, 270-273 Caustic potash, reaction with, of neu- tral solutions of aluminium salts. 111 soda, electromotive force re- quired to decompose, 304 molten, electrolysis of, 223- 225 reaction with, of neutral solu- tions of aluminium salts,lll Ceilings, aluminium. 479 Cliancourtois, M. de, on Greenland cryolite, 286. 287 Cliandeliers, aluminium, 479 Chanu, M., founding of a works by, 14 Cbapelle, M., on the reduction by carbon without the presence of other metals, 402, 403 Chemical apparatus, use of aluminium for, 484, 485 balances, aluminium for the beams of, 482, 483 equivalent of aluminium, 301 properties of aluminium, 83-106 Chemistry, thermal, reduction of alu- minium compounds from the stand- point of, 226-245 Chenot, M., claim by, 10 experiments of, 421 , 422 Chicago, use of aluminium on a building in, 487 Chiolite, 121 Chloride of aluminium, 115, 116 and sodium, manu- facture of, 152-168 reduction of, theo- retically consid- ered, 232, 233 ■ 642 INDEX. CWoride, double, of aluminium and sodium, reduction of, by zinc, 429 Chlorides, alkaline, solutions of, ac- tion of aluminium on, 102 anhydrous metallic, preparation of, 165, 166 heat developed by metals in forming, 282. 233 metallic, solutions of, action of aluminium on, 102 sodium or potassium, apparatus for decomposing, 219 Chlorine, action of, on aluminium, 10(3 determination of, in aluminium, 616 gas, action of, on alumina, 112 qualitative test for, 6U6 Chrome-steel, aluminium in, 423,575 Chromium and aluminium, alloys of, 4i)9, 5U0 determination of, in alnminium, 617, 6KS Chrysoberyl, 115 Church on alumina in plants, 39 Cider, action of, on aluminium, i)4 Clark, J., patents of, 434 Clarke, F. W. , on the percentage of aluminium in the earth's crust, 39 Classen, Dr., method of, for deter- mining aluminium in iron and steel, 622 Clay, manufacture of aluminium sul- 1 phate from, 127 ! use of, for producing aluminium j chloride, 167 i Cleaning and pickling aluminivim, [ 456 Cleaver, E., patent of, 424, 425 1 Cobalt and aluminium, alloys of, j 500 ! determination of, in aluminium j bronze, 625 j Coehn, recommendation of, in melt- i ing aluminium. 452 t Coffee, action of, on aluminium, 95, | 96 I Coinage, aluminium, 483. 484 requirements of a metal for, 483. 484 Color of aluminium, 59. 60 alloys, 498 vapor of aluminium, 66 Colorado, cryolite in, 46 native alum in, 50 Columbian Exposition, Chicago, 1893, aluminium exhibit at the, 84 Comenge, M., on the reduction of aluminium sulphide by copper, 417 on the reduction of aluminium sulphide by iron, 418 preparation of alumin- ium sulphide pro- posed by, 177 process of, 411 Compass boxes, aluminium, 482 Compounds of ahiminium, structure, properties and pre- paration of, 107- 132 voltage required to decompose, 287 Conductivity, electric, of aluminium, 81,82 thermal, of aluminium, 82 Constructions, use of aluminium for, 487^ Cooking utensils, aluminium, 476 use of aluminium for, 485 Cooper, W. S., castiugs of aluminium, made by, 447 Copper alloyed with aluminium, pro- duction of, 413, 414 aluminate, 115 and aluminium, alloys of, 534-571 depositing aluminium on, 308, 309 determination of, in aluminium, 614 bronze, 624 effect of a small percentage of, on aluminium, 536. 537 on the color of alumin- ium, 59 malleability of alu- minium, 537 elimination of, from aluminium, 449 heat of combination of, with alu- minium, 543. 544 nickel and aluminium, alloys of, 511-516 oxide, action of aluminium on, 105 plating aluminium on, 323, 324, 469, 470 with, 478 qualitative test for, fi06 reduction in the presence of, or by, 418-418 of aluminium sulphide by, 236,417 INDEX. 643 Copper, salts, voltage required to de- compose, 237 sheet on which aluminium has been rolled, 473 * solutions, action of aluminium on, 101 zinc and aluminium, alloys of, 530-533 Corbelli, patent of, 410 process of, for depositing aluminium, 308 Corbin on aluminium in chrome steel, 575 Corrosion, resistance to, of alumin- ium bronzes, 564 Corundum, 47, 4H value of, 48 Cowles, A. H., aluminium-manganese alloy of, 505, 506 on aluminium bronze for heavy guns, 567, 568 Bros., aluminium-nickel-copper alloys made by, 516 furnace of, aluminium in the soot from, 343 process of, 329-347 furnaces used in the, 332-336 products of the furnace of, 341-343 reactions in the process of, 343-347 silicon-aluminium bronze of, 570, 571 test of aluminium brasses made by, 531 , 532 useful effect of the current in the process of, 344, 345 Co., bronzes, tests of, 554, 555, 556, 55i, 558 ferro-aluminium of the, 574 occurrence in the history of the, 346, 347 on the resistance to corrosion of aluminium bronzes, 565 solders for aluminium bronze recommended by, 570 E. H. and A. H., 28 Electric Smelting and Alumin- ium Co., 28 Electric Smelting and Alumin- ium Co., infringement of the Hall patents by the, 34 invention, 28, 29 process, principle made use of in the, 28, 29 Cowles Syndicate Co., of England, plant of, 340 Creil, France, works at, 26 installation of Minet's process at, 362 Cross and Hillebrand, description of Colorado cryolite by, 46 Crucible steel, tests of the effect of aluminium on, 580, 581 used in Heroult's process, 388, 390 Crucibles for manufacture of sodium, 208 melting aluminium, 103, 104, 443, 444 iron, used by Rose, 276, 277 lining for, 367, 444, 445 used at the Froges works, 395 Cryolite, 45-47, 120 action of, on aluminium, 103 quartz, 370 spiegeleisen, 436 advantages of, for reduction, 287, 288 amount of aluminium extracted from, 367 artificial, preparation of, 169, 170 boiling of, in solution of soda, 168 commercial, impurities in, 295, 296 cost of, 46 decomposition of, in the wet way, 149-152 experiments on the use of, for producing aluminium, 15 Gratzel on the electrolysis of, 369, 370 Hampe on the electrolysis of, 368-372 importation of, by the Pennsylva- nia Salt Co., 46 manufacture of aluminium sul- phate from, 127 methods based on the reduction of, 274-300 molten, action of, on aluminium, 371 decomposition of, by mag- nesium, 437 non-wetting of carbon by, 324 specific gravity of, 386 phosphoric acid in, 285, 286 preparation of, 168-173 of alumina from, 144-152 properties of, 45 proportion of aluminium ex- tracted from, 351 644 INDEX. Cryolite, pure, composition of, 46 purity of comuiercial, 367 quartz in, 870 recovering alumina from, 262 reduction of, ^85 advantages of the, 281 Woliler's modifica- tions in the, 289 Schmidt on the electrolysis of, 308, 869 typical analysis of, 46, 47 use of, as a flux, 288 in Kleiner's process, 848, 34W Wohler's modificalions of reduc- ing, :iH9 Crystalline form of aluminium, 6!) Culinary utensils, use of aluminium for, 48.'), 486 Cunningham, Capt, patents of, 31 sodium processes of, 291.292 Cupellation of aluminium with lead, 459 Curaudau, production of potassium or sodium by, 179, 180 Curie, P., process of making alumin- ium chloride proposed by, 165 Current-density, influence of, 305 effect of the tension of the, 306 Cyanide of aluminium, reduction of, by zinc, 433, 434 Cyanite, 49 Cyanogen, reduction by, 410, 411 DAGGER, H. T., on the Cowles .process in England, 345 Darling, J. D., on the electro-deposi- . tion of aluminium, 317, 318 Davenport, R. W., experiments of, 592^ experiments of, with ferro-alu- minium, 579, oSO explanation by, of the effect of aluminium on wrought iron, 588, 589 Davy, Sir Humphry, experiment of, to decompose alumina, 319 experiments of, 4,5 isolation of so- dium by, 179 Debray on aluminium bronze, 539 Decorations, use of aluminium for, 479 D'Eichthal, M., 15 "Defender," the, 478 Delaware, kaolin in, 49 Dental plates, alloy for, 520 aluminium for, 480, 481 cast aluminium, 446 of aluminium, 98 Dentistry, use of aluminium in, 481 Desilverizing process, addition of alu- minium to the zinc used in the, 529, 530 Deville-Castner process, the, 24, 270- 273 cost of aluminium by the, 273 H. St. Claire and Bimsen's meth- ods of decompos- i n g aluminium- sodium chloride by the battery, 320-324 composition of mix- tures used by, 258, 261 controversy between, and the Tissier Brothers, 13, 14 experiments of, in reducing alumin- ium compounds, 250-252 first production of aluminium fluor- ide by, 119 improvements in the manufacture of so- dium by, 180-194, 197-201 method for deter- mining silicon rec- om mended by, 608, 609 method of, for de- termining fluorine, 616,617 method of, for de- term ining iron (and aluminium), 611, 612 method of, for de- termining sodium, 615, 616 method of, for pre- paring alumina, 1.84, 135 INDEX. 645 Deville,H.St.Claire,methods of, based on the reduction of cryolite, 285-:i87 methods of, for re- ducing aluminium chloride by so- dium. 252-1^57 on action of air on aluminium, 83, 8-1 on action of caustic alkalies on alu- minium, 99 on action of nitre on aluminium, 104 ou action of nitric acid ou alumin ium, 90 on action of organic acids ou alumin- ium, fi2, 93 on action of solu- tions of metallic salts on alumin- ium, lUO, 101 on action of sul- phuretted hydro- gen on alumiuium, 80, 87 ou action of sul- phuric acid on aluminium, 88 on action of water on aluminium, 85, 86 on aluminium-boron alloys. 497, 498 on aluminium-lead allovs, n{)3 on aluminium-mer- cury alloys, 500 on aluminium-sili- con alloys, 517, 518 on aluminium-sodi- um alloys, 521 on aluminium-zinc alloys, 528, 529 on casting alumin- ium, 445 on color of alumin- ium, 59 on crystalline form of aluminium, 09 on effect of iron on aluminium, 572 on freeing alumin- ium from impuri- ties, 449, 450 Deville, H. St. Claire, on freeing alu- minium from slag, 447; 448 on fusibilitj' of alu- minium, 05 on gilding and sil- vering of alumin- ium, 472 on melting alumin- ium, 442, 443 on soldering alumin- ium, 458, 459 on soldering alumin- ium bronze, 509 on sonorousness of aluminium, 07, 08 on veneering with aluminium, 409, 470 on volatilization of aluminium, 00 process for preparing aluminium fluor- ide recommended by, 170 process for utilizing aluminous fluoride slags used by, 148, 149 process of amount of aluminium made by the, 30 process of for de- composition of cryolite in the wet way, 149, 1.50 process of, for pre- paring aluminium chloride on a'sniall and a large scale, 153-157 process of, for pre- paring artificial cryolite, 109,170 process of for reduc- tion of aluminium compounds, 257- 208 production of alu- minium by, 8 researches of, on alu- minium, 9-10 test by, of alumiuium bronze, 5.56 work by, on alumin- ium, 10 Dewar, Prof , on the relative electrical resistances of metals, 82 646 INDEX. Diaspore, 113 Dick and Percy, experiments of, 283- 285 • Discoloration, removal of, from alu- minium, 60 Disthene, 49 laminated, Duvivier's experiment with, 319, 820 Ditte, A., on action of nitric acid on aluminium, 90 sulphuric acid on alumin- ium, 88 water on alu- minium, 86 Drawing aluminium, 454 Ductility of aluminium, 76, 77 Dufour, on the velocity of sound in aluminium, 69 Dullo, M., on reduction of the double chloride of aluminium and sodium by zinc, 429 use of common clay for producing aluminium chloride, 167, 168 Dumas, M., on gases in aluminium, 57 Dust, aluminium, 76 Duvivier's experiment with laminated disthene, 319, 320 Dyuamo-electric machinery, advances in the, 24 machines, use of, first proposed, 326 ELASTICITY of aluminium, 69, 70 Electric arc, reduction of disthene in the, 319 conductivity of aluminium, 81, 82 current, mechanical and ther- mal equivalent of the, 301 furnace. Mierzinski on the use of the, 27, 28 Siemens', 27 lights, shades of aluminium for, 479 processes, classification of non- aqueous, 318 non-aqueous, of depositing aluminium, 818-401 welding of aluminium, 457 Electricity, decomposing power of,236 reduction of aluminium com- pounds by, 236, 301-401 Electricity, reduction of aluminium compounds by other means than, 402-441 sodium com- pounds by, 219-225 Electro-chemical equivalent of alu- minium, 301 deposition of a metal, 304, 305 thermal methods, 318 Electrolysis of molten caustic soda, 223-225 sodium chloride, 222, 2:3 Elements, difierent, heat developed by sulphur combining with, l35 generated by the combi- nation of al- u m i n i u m with, 228 heat given out by, combining en- ergetically with oxygen, 229 position of aluminium in the periodic classification of the, 107, 108 Elevators, use of aluminium on, 479 Ellery-Howard Co., New York, use of aluminium plates for printing by the, 489 Emanuel, P. A., process of, 406 Embroidery, aluminium in, 475 Engineering instruments of alumin- ium, 482 England, amount of aluminium pro- duced in, 36 first aluminium works in, 18 kaolin in, 49 Engraving aluminium, 456 Equivalent, chemical, of aluminium, 801 electro-chemical, of aluminium, 301 Escher, Wyss & Co., aluminium ves- sels built by, 476 Ettmiiller, discovery by, 2 Eureka Tempered Copper Co., claim of the, 458 Evrard, M., production of aluminium bronze by, 414 FALLS OF THE RHINE, alumin- ium works at, 388 Farmer, M. G., alloy of, 531 INDEX. 647 Fanner, M. G., apparatus patented by, for obtaining aluminium elec- trically, 311 patent of, 347 Faraday and Stodart, aluminium-iron alloy obtained by,575 investigations of, on iron-aluminium al- loys, 422, 423 on sonorousness of alu- minium, 6S thermal conductivity of aluminium, 82 Faure, C. A., process for producing aluminium chloride patented by, 166,167 proposition of, 398, 399 Faurie, G. A., claim of, 413 process of, for prepar- ing aluminium bronze, 415, 416 Faustman & Ostberg Mitis Foundry, experiments at the, 577 Feldman, A., method of, 362, 363 Felsobanyte, 127 Ferric oxide, action of aluminium on, 1115 Ferro-aluminium, 574 analyses of, 342 -aluminium, analysis of slags formed in producing, 342 claims for, in foundry use, 595, 596 effect of, on the grain of iron, 601 , 602 increase in elasticity of iron by the addition of, 60(1, 601 in fluidity of iron by, 602 in hardness of iron by, 603 in transverse strength of iron by the addition oi, 699, 600 manufacture of, 425 mode of adding to iron, 596 practical benefit to poor iron from, 603-604 results of adding, to iron, 605, 606 reduction in the shrinkage of iron by, 602, 603 -aluminiums, analysis of, 618-623 Field glasses, aluminium, 481 Films of aluminium, color of, by transmitted light. 60 Findlay, Ohio, plant at, 432, 433 Fischer, Dr. P., on Braun's process for depositing alu- minium, 311 Gratzel's patent claims, 328 Fizeau on the expansion of aluminium by heat, 77 Flash-light powder, use of aluminium for, 489, 490 Fleury, A. L,., process of, 408 Fluoride of aluminium, reduction of, theoretically considered, 234, 235 Fluorides of aluminium, 119-120 role of, as a flux, 257, 258 table of the heat of formation of, 234 Fluorine, action of, on aluminium, 106 determination of, in aluminium, 616, 617 gas, action of, on alumina, 112 isolation of 234 Fluorspar, action of, on aluminium, 102, 103 Flux and slag, influence of, on the aluminium, 253 Foods, action of on aluminium, 94, 96 Forks, aluminium, 486 Fowler, Dr., patent of, for using alu- minium in dentistr3', 481 Fracture of aluminium, 60, 61 France, aluminium industry, in 19,20 amount of aluminium produced in, 36 bauxite in, 41 kaolin in, 49 operation of the Hall process in, 362 Fremy, M., on the preparation of al- uminium sulphide, 174-176 French Guiana, deposits of bauxite in, 41 Frishmuth, Col. Wm., aluminium man- ufactured by, 32,33 electro-de posi- tion of an alloy of nickel and aluminium by, 311 process of, 269, 270 solders of, for al- uminium, 462 Froges (IsSre), France, works at, 30, 395, 396 648 INDEX. Fruits, juices of, action of, ou alumin- ium, 96 Furnace, Cowles Bros'., ?.R4-H?S aluminium in the soot from, 34S products of the, 341-343 electric, Mierzinski ou the use of the, -27, 28 peculiar product formed in tne, 499 for continuous manufacture of sodium in cylinders, 191, 192 mitis castings, 585. 586 production of sodium, 2(i8 Gerhard's, 289 Grabau'sf 298 Gratzel's, 326, 327 Niewerth's, 411, 412 Oni holt's, ;h64 reduction, 266 reverberatorj-, melting alumin- ium in the, 444 Siemens' electric. 27 Thomson's, for preparing alu- mina from cryolite, 144, 145 used in Heroult's process, 388,390 Fusibility of aluminium, 65, 66 Fusion of aluminium, latent heat of, 79, 80 GADSDEN, H. A., method of ob- taining alu- minium pat- ented by, 164 patent of, 269 Gabnite, 115 Galanaugh, aluminium rowing .shells of, 478 Gallium and aluminium, alloys of, 500, 601 Galvanizing bath, aluminium-zinc alloy as an addition to the, 5l9 Gas, absorption of, by aluminium, 452 -fixtures, aluminium, 470 Gaudin, process of, for reducing alu- minium, 325 Gehring, Dr. G., method of, for coat- ing metals, stoneware, etc., with aluminium, 471 Geoffroy on the base of alum, 2 Georgia, bauxite in, 41 Bauxite and Mining Co., 41 kaolin in, 49 Gerhard, F. W., furnace of, 289 process of, 406, 407 I Gerhart, C. H., aluminium works of, 18 German armv, use of aluminium in the, 96 -silver, alloy of, with aluminium, 538 depositing aluminium on, 308, 309 Germany, aluminium industry of, 18 Gibbsite' 113 Gilchrist, P. A., investigations of, on aluminium in steel, 579 Gilding aluminium, 472 Glaciere, works at, 15 Gmelin on the amalgamation of alu- minium, 507 Gold and aluminium, alloys of, 501- 603 heat of combination of, 502, 503 Niirnberg, 5(11 plating aluminium with, 473 Gore, G., experiments of, 307 on electro-deposition of al- uminium, 315 process of, for depositing aluminium, 3*18, 309 Grabau, L,., advantages of the process of, 299 apparatus of, 364, 365 electrolytic process of, 400 on electrolysis of molten sodium chloride, 222, 223 patent of, for reducing aluminium compounds by phosphorus, 440, 441 patented improvements of, 32 process of, 294-300 for producing al u ni i n i u m fluoride, 171- 173 Graphic formulae of aluminium com- pounds, ](;8. I(i9 Gratzel, R., furnace used by, 326, 327 on the electrolysis of cryolite, 369 patent of, 437 process of, 24, 326-329 Greene andWahl, patent of, for pro- ducing pure me- tal 1 i c manga ■ nese, 105, 106 production of pure manganese by, 436 INDEX. 649 Greene, Dr., experiment of, 43() Green, R. E., process of, 409, 410 Greenland, difficulties in obtaining cryolite from, 28B occurrence of cryolite in, 45 Grill-work, aluminium, 479 Grinding, polishing and burnishing aluminium, 4o5, 456 Grove battery, use of aluminium in the, 91 Grousillier, H. v., improvement of, L'70 Griiner and Lau, on the reduction of aluminium in the blast furnace, 423 on aluminium in pig iron, 575 Guns, heavy, aluminium bronze for, 507, 508 HALL, CHAS. M., electrolytic method of, 25, 26 process of, 872-880 heat developed and disiril)- uted in the process of,H84 patents of, 373, ■ 374. 375 process, opera- tion of, in France, 362 not antedated b y Deville, 324 reactions and efficiency of the process of, 38:;- 386 in the pro- cess of, 3h4 summary of pro- cess o f , 374 voltage required to decom- pose the bath of, 238 Halotrichite, 126 Hampden Emery Co., 47, 48 Hampe, Dr. W., analysis of Cowles Bros', bronze by, 341 Hampe, Dr. W., experiments of, 290 on electro-depcsition of aluminium, 316 electrolysis of cry- olite, 308-372 reactions in Cowles' process, 344 reduction of alum- ina b.y carbon, 416.417 Handy, J. O., on the determination of silicon, 610.611 Hardening aluminium, 452, 453 and annealing aluminium bronzes, 561 Hardness of aluminium, 61, 62 Hare, Dr., experiments of, 4 Harvey Filley Plating Co., electro- deposition of aluminium by the, 810 Haurd, Jas. S , electro-deposition of aluminium by, 810 Hautefeuille, process of, for making crystallized aluminium fluoride, 17(). 171 Head-lights, aluminium reflectors for, 479 Heat, calories of, absorbed by acety- lene, 241 developed and distributed in Hall's process, 384 by the combination of some of the elements with chlo- rine, bromine or iodine, 232 expansion of aluminium by, 77 formula for calculating the, of combustion of hydrogen gas, 240 for expressing the, in carbon, 240 for, of formation of carbonic oxide, 2-10 for, required to decompose alumina, 239 generated by the combination of aluminium with the different elements, 228 given out by elements combining energetically with oxygen, 229 of the formation of fluorides, table of the, 234 specific, of aluminium, 77-81 Helbig on aluminium amalgam, 509 Hellot on the base of alum, 2 Helmet, aluminium, 475 Hemelingen, Aluminium and Mag- nesium Fabrik at, 24 650 INDEX Hemelingen, works at, 328 Hercules metal, 51b Hercynite, 115 probable occurrence of, in iron ore, 429 H^roult-alloy process in tlie United States, HO, 31 and Kiliani, apparatus of, for producing pure aluminium, 391 electrolytic process of, 38()-398 current used in ,392 of, useful effect de- rived from the current in, 392, 393 patent of, 373 process, cost of aluminium by the, 397 Hesse, deposits of bauxite in, 41 Heycock and Neville on aluminium- lead al- loys,504 -tin al- loys, 524 Hirzel on aluminium-silver alloys, 521 Hoeveler on aluminium-antimony al- loys 496 Hoffman on the base of alum, 2 Holbrook, C. T., on aluminium in pig-iron, 427-429 Hollow-ware, casting of, in alumin- ium, 447 Horse-shoes, aluminium, 478 Howard and Hill, patent specifica- tions of, 439 Howe, H. M., on the role of alumin- ium in wrought-iron castings, 592 Hunt, A. E., on action of sodium chlo- ride on aluminium, 97 bauxites of Georgia, Alabama and Ar- kansas, 45 Dr. T. Sterry, on the produc- tion of aluminium by Cowles Bros', process, 331. 332 Hydrated aluminium sulphate, 126, 127 Hydrochloric acid, action of, on alu- minium, 91, 92 Hydrofluoric acid, heat of formation of, 234 Hydrogen, action of, on aluminium, 106 carburetted, reduction by, 408- 410 compounds, voltage required to decompose, 237 Hydrogen, electro-chemical equiva- lent of, 301 gas, equation for the temperature at which alumina will be- gin to be reduced by, 240 formula for calculating the heat of formation of, 240 reduction by, 405, 407 of alumina, 231, 240 aluminium chlo- ride, bromide, and iodide, 233, 234 sulphide and sulphur, action of, on aluminium, 86, 87 reaction with, of neutral so- lutions of aluminium salts, 111 union of, with oxygen to form water, 226, 227 ILLINOIS Pure Aluminium Co., manufacture of culinary utensils by the, 485 India, corundum in, 47 Instruments, astronomical and philo- sophical, use of aluminium bronze for, 567 surgical, 480 Iodide of aluminium, 118 Iodine, action of, on aluminium, 106 Ireland, deposits of bauxite in, 41 Iron aluminate, 115 -aluminium alloys, Brin Bros', process of pre- paring, 425 Cleaver's patent for producing, 424, 425 Faraday and Stod- art's investiga- tions on, 422,423 preparation of, by an alumin- ium com- p a n y in Kentucky, 425, 426 of, by the Alu- minium Pro- cess Co. ,426, 427 and aluminium, alloys of, 572- 605 (and aluminium), determination of, in aluminium, 611-614 blast furnace, reduction of alu- minium in the, 429 INDEX, 651 Iron, Castner's process of removing, from aluniiuium-sodium chlo- ride, 163 commercial, aluminium taken up by, 574, 575 composition of, used in testing the efifects of ferro- aluminium, 597 determination of aluminium in, H21 , 622, 623 of, in aluminium bronze, 624 of, modification of Deville's method, 612-614 does the aluminium remain in castings of? 5il8, 599 effect on grain of, by the addition of ferroaluminium, 601 ,(i()2 of, on the malleability of alu- minium, 75 melting point of alu- minium, 66 elimination of, from aluminium, 449 increase in elasticity of, bv the addition of ferro- aluminium, 6(10. COl fluidity of by ferro- aluminium, 602 hardness of, by alu- minium, 603 transverse strength of, b)' the addition of ferro-aluminium, 599, 600 influence of, on aluminium, 572 the melting point of aluniin ium, 572. 578 poor, practical benefit to, from ferro-aluminium, 603, 604 practical results of adding ferro- aluminium to, 605. 606 puddling, influence of aluminium in, 594, 595 qualitative test for, 606 reduction by and in presence of, 41H-429 in the shrinkage of, by ferro- aluminium, 602. C03 of aluminium sulphide by, 236 r61e of, in aluminium, 53 salts, voltage required to decom- pose, 237 wrought, effect of aluminium on, 581-595 explanation of the increased fluidity of. by the addition of aluminium, 589, 590 Ivins, E., process of, for making me- tallic tubes, 454 TABLOCHOFP, P., apparatus of, J for decomposing .sodium or po- tassium chlorides, 219 Jacquemont, M., 15 Jarvis, G. A., improvement in the manufacture of sodium patented by, 203 Javel, methods used by Deville at, 252-257 Jeangon, J. A., process of, for depos- iting aluminium, 309, 310 Jewelry, use of aluminium for, 601, 502 Johannes, I. H., alloy of, 504 Joule on the amalgamation of alu- minium, 507 Julien, Capt., tests by, of aluminium- copper alloys, 537 Juniata Valley, manufacture of alu- minous pig-iron from the iron ores of the, 428 KAGENBUSCH'S process, 325, 326 Kalait, 131 Kamarsch, test of aluminium wire by, 70 Kaolin, 48, 49 composition of, 48 deposits of, 49 formation of, 48 properties of, 48, 49 value of, 49 Karsten, experiments of, 4 on woolz steel, 576 Keep, J. W., investigations of, on the effect of ferro-alumin- ium, 597, 5fl8 on effect on the grain of iron by the addition of ferro-aluminium, 601,602 t)n increase in the fluid- ity of iron by ferro- aluminium, 602 on shrinkage of alu- minized cast-iron, 602, 603 tests by, 599 of the solidity of castings, 5^7 Kentucky, aluminium company in, 403 preparation of iron-aluminium alloys by an aluminium com- pany in, 425, 426 652 INDEX. Kerl and S'.ohman on engraving alu- minium, 45(5 Kettles, steam, of aluminium, 486 Kiliani, Dr., modifications in Her- oult's process by, SO Klaproth, experiments of, 4 Kleiner, Dr. B-, process of, 25, 347- 853 electrical power con- sumed in, 352 purity of the aluminium prod need by, 352,353 trial of process of, at Neuhausen, 38 S Knife, use of, in testing the quality of aluminium, 62 Knives, aluminiurn, 486 Kuowles, patent of, -110 Kopp on the specific heat of alumin- ium, 78 Kosman,Dr., on reactions in Castner's process, 215-217 Cowles ' process, 344 Krauchkoll on aluminium amalgam, 509 Krupp's works, apparatus erected at, 293, 294 LACE, aluminium in, 475 La Glaci^re, improvements in the manufacture of sodium at, 197-199 Lamps, safety, of aluminium, 479 Land, C. H., process of, for soldering aluminium, 465 Laugley, Prof. J. W., on aluminium- chromium - alloys, 499 expaii si on of alumin- i u m b y heat, 77 specific gravity of alumin- ium, 64 Latent heat of fusion of aluminium, 79, 81) Laur, F., on French bauxites, 44 process of, for calcining bauxite, 143 Lauterborn, F., decomposition of alu- minium sulphide by antimony and car- bon proposed by, 438 on reduction of alu- minium sulphide by iron, 418 patent of, 433, 434 for preparing aluminium sulphide, 178 Lavoisier on alumina, 3, 4 Lead and aluminium, alloys of, 503, 504 cupellatiou of aluminium with, 450 determination of, in aluminium, 614 bronze, 624 oxide, action of aluminium on, 105 qualitative test for, 606 reduction by, 435, 436 separation of, from aluminium, 449 solutions, action of aluminium on, 101, 102 Leaf, aluminium, 76 beating and tempering of, 451: LebedefF, process of, 409 Le Chatellier, method of, for reduc- ing aluminium com- pounds, 324, 325 on tensile strength of annealed aluminium wire, 73 test by, of resistance of annealed alumin- ium bronze, 560 tests by, of tensile strength of alumin- ium bronzes, 555 Lechesne, 515 Ledebuhr on aluminium-iron alloys, 574 Lejeal, on aluminium-chromium al- loys, 5(10 -cobalt alloys, 500 -lead alloys, 504 -nickel alloys, 511 -titanium alloys, 526 Le Roy, G. A., tests by, of the action of .svilphuric acid on aluminium, 89 Lessiveur methodique, 146 INDEX. 653 Le Verrier, determinations by, of the melting points of alu- minium bronzes, .'548 on carbon in commercial aluminium, 57, 58 on diminishing the amount of silicon in aluminium, 45:^ on evolution of gas by molten iron, 593 on nitrogen in commercial aluminium, 58, 59 on specific heat of alu- minium, 78 process of preparing alu- minium carbide by, 124 study by, of the melting points of aluminium- copper alloys, 634, 535 tests by, of aluminium-ti- tanium al- loys, 526, -tun g s t e n alloys, 527 Levy, I/., on aluminium-titanium al- loys, .'26 Lieber, R., process of, for preparing alumina, 141, 142 Light, obtaining of, by burning alu- minium, 490 Lime-kiln for furnishing carbon di- oxide, 147 phosphate of, action of, on alu- minium, 106 water, actionof,on aluminium,100 Lisle, Dr., analysis of native alum by, 50, 51 experiments of, 409, 416 in reducing alumin- ium sul- phide by zinc, 485 on reduc- tion o f alumin- ium com- po u n d s by tin, 439, 440 on removal o f zinc from alu- minium, 450 on electro-deposition of aluminium, 316 Lithographic plates, use of aluminium for, 488, 489 Lockport. description of Cowles Bros', process as carried on at, 333- 339 Hall's experiments at, 376 Locomotive head lights, aluminium reflectors for, 479 Lorenz, L., on the thermal conduc- tivity of aluminium, 82 Lossier, method of, 353, 354 Low carbon steel, aluminium for, 578 Lowig, experiments of, in precipitat- ing solution of sodium aluminate, 143 Lubbert and Roscher, investigations of, on the action of organic acids on aluminium, 93, 94 Lunge, Prof. G., tests by, of the action of organic acids upon aluminium, 94-96 MABERY, Prof. C. F., 28 ona peculiar product formed in the electric furnace, 499 on prodjc- tion of alu- minium l)y C o w 1 e s Bros', pro- cess, 3l9- 331 process o f m.aking al- umi n i u m ch 1 o r i d e patented by, 165 MacKellar, T., type-metal of, 504 Macquer on the earth of alum, 3 Mac Tear, F., on Castner's sodium process, 207-212 Magnesia, heat developed in the re- action of, on aluminium chloride, 233 Magnesite, calcined, for lining cruci- bles, 444, 445 Magnesium, action of, on aluminium fluoride, 235 aluminate, 115 and aluminium, alloys of, 504^,505 reduction by, 437, 438 of alumina, 229, 230 of aluminium sulphide by, 236 654 INDEX. Magnesium salts, voltage required to decompose, 238 und Aluminium Fabrik, direc- tions bj', for preparing alumin- ium bronzes, 646, 547 Magnetism of aluminium, 67 Malleability of aluminium, 75, 76 influence of sili- con on the, 518 Mallet on action of caustic alkalies on aluminium, 99 color of aluminium, 59 elasticity of aluminium, 69 fusibility of aluminium, 65 malleability of aluminium, 75 specific gravity of alumin- ium, 62 heat of aluminium, 77. 78 production of aluminium nitride by, 125 Manganese and aluminium, alloysof, 505, 506 anal y sis of alloys of, 626 determination of, in aluminium bronze, 625 dioxide, action of aluminium on, 105 heat developed in the reaction of, on aluminium chloride, 233 oxide, action of aluminium on, 436 pure metallic, method of produc- ing, 105, 106 production of, 436 reduction by, 436 of aluminium sulphide by, 236 salts, voltage required to decom- pose, 237 ! Mann, A., patent of, 417 Mannesmann, addition of tungsten to aluminium recom- mended by, 527 process of cold rolling, 454 Marggraff on alum and. its earth, 2 Margottet, M., description by, of ap- paratus for the prep- aration ofaluminium chloride, 157-159 j on action of alumin- ' ium on solutions of I metallic chlorides, ! 102 Margottet, M., on action of hydrogen sulphide on aluminium, 87 Marshall Furnace, Penna., aluminium in pig iron produced at the, 428 Mat on aluminium, 456 Medicine, use of aluminium in, 480. 481 Melting aluminium, 442-445 point of aluminium, 66 points of aluminium-copper al- loys, 5:-i5 -tin alloys, 525 Meuge, patent of, 347 Mercurous chloride, action of alu- minium on, 106 Mercury and aluminium, alloys of, 506-509 bottles, manufacture of sodium in, 185-190 solutions, action of aluminium on, 101 Metal, electro deposition of a, 304,305 mitis, analyses of, 584, 585 method of treatmentof,585,586 quality of the, produced by Minet's process, 361 requirements of a, for coinage, 483, 484 Metallic chlorides, anhydrous, prepa- ration of, 165, 166 solutions of, action of aluminium on, 102 oxides, action of aluminium on, 105, 106 salts, action of solutions of, on aluminium, 100-102 Metals, alkaline, reduction of, theo- retically considered, 237 coaling of, with aluminium, 307, 308, 469-472 effect of a small quantity of alu- minium on, 494, 495 heat developed by, in forming chlorides, 232, 233 influence of aluminium on the color of, 494 other, comparison of production of, with aluminium, 38 order pf the aflinity of the, for sulphur, 236 various, prices of, 61. 65 relative electrical resistances of, 82 weights of, to give a cer- tain strength, 74, 75 specific gravity of, 64 heat of aluminium com- pared with, 81 INDEX. 65S Metals, veneering of, with aluminium, 473 Meudon, tests of aluminium-copper alloys at, 587 Michel on aluminium-iron alloys, 573 -manganese alloys, 505 -nickel alloys, 510 -titanium alloys, 526 -tungsten alloys, 527 Mierzinski, Dr. S. , on the electro-depo- silion of alumin- ium, 316 on the use of the electric furnace, 27,28 " Mignon," the, 476, 477 Military uses of aluminium, 475, 476 Milk, action of, on aluminium, 94 Miller, C. B., anti-friction alloy of, 504 Milling screens, 567 Milton, England, aluminium works at, 840 Milwaukee, the American Aluminium Company of, 365 Minargent, 511,512 Mine work, use of aluminium for, 479, 4)-0 Mineral soda, 276 Minet, A. , electrolytic process of, 354- 362 of, composi- tion and properties of the baths used in the, 357, 358 of, disposi- tion of the apparatus in the, 355-357 experiments of, 26 installations of the process of, 361, 362 on aluminium-tin alloys, 5-24. 525 on silicon in aluminium, 51:-' on strength of aluminium strongly worked and an- nealed, 74 results of the experiments of, 359-361 test by, of an aluminium- tin alloy, 523 views of, 358, 359 voltage required to decom- pose the bath of, 239 Mitis castings, absence of aluminium in, 587 history of, 582, 583 mixture for, 584 Nobel's furnace for, 585, 586 production of, 583 properties of, 586, 587 rationale of the process of making, 587-594 raw material for, 583-585 strength of, 587 metal, analyses of, 584, 585 method of treatment of, 585, 586 Molybdenum and aluminium, alloys of, 509, 510 Monckton's patent for reducing alu- minium compounds, 325 Monnier, M. A., early manufacture of sodium by, 17 Montgelas, R. de, patent of, 437 patents of, for the electrolysis o f aqueous s o 1 u - tions, 312, 313 process patented by, for producing aluminium chlo- ride and the double chloride with sodium, 164 Montucci,H., alviminium coinage pro- posed by, 483 Morin, arguments of, that aluminium bronzes are true chemical com- binations, 541, 542 on anti-friction qualities of alu- minium bronzes, 563 on veneering aluminium with silver, 473 Morris, J., claim of, 405, 406 Moulds for casting aluminium, 447 Mourey, M., alloys used by, for sol- dering aluminium, 461 , 462 , solders of, for alumin- ium, 459-461 Muller, H., process of, for preparing alumina, 142 NACCARI on the specific heat of aluminium, 7H Nanterre, composition of the mix- tures used at, 258, 261 furnace used at, 261 improvement in the manu- facture of sodium used at, 199-201 656 INDEX Nanterre, process for utilizing alu- minous fluoride slags used at, ]4«, 149 rationale of the process used at, 257 works at, lo Napoleon III., assistance of, 11, 12 interest of, in alumin- ium, 475 Nelson, recommendation by, 473 Neogen, 512 Nelto, Dr. C, patents of, 31 process of, 290-294 for the pro- duction of sodium, 217-219 and Saloman, processes of, 31 Neuhausen aluminium bronzes, test of, 558. 553 tests at, of the suitability of aluininiuui bronze for boats, 506 works at, 29, 388 manufacturing cost of aluminium at the, 397. 398 selling price of alu- minium at the, 397 New Ken.sington, Pa., aluminium works at, 382 • New Mexico, deposit of native alum in, 50 Newport,Ky., aluminium works in, 403 Niagara Fal ls,alumi nium works at, 382 Nickel andaluminium, alloys, 510.51 1 analy sis of, 626 use of alloy of, on the "Defender," 478 bronzes containing, 512-515 copper and aluminium, alloys of, 511-516 determination of, in aluminium bronze, 625 plating aluminium with, 473 salts, voltage required to decom- pose, 237 Nicolai and Langenbach, process of, for soldering aluminium, 466 Niewerth, H., patent of, 418, 419 process of, 411-413 for the re- duction of alumin- ium com- pounds, 268 Nitrate of aluminium, 130 Nitre, action of, on aluminium, 104 purification of aluminium by, 449 Nitric acid, action of, on aluminium, 90, 91 cold, amount of the action of, on aluminium, 90, 91 resistance of aluminium to, 488 Nitrogen and aluminium, compounds of, 125 effect of, on aluminium, 58. 59 presence of, in commercial alu- minium, 58. 59 Nobel's furnace for mitis castings, 585, 586 Novel, J., alloys for soldering recom- mended by, 464, 466 Niirnberg gold, 501 ODOR of aluminium, 66, 67 Oersted, experiments of, 6 in reduc- ing alu- minium c o m - pounds, 246-247 Ohio, native alum in, 50 Oil, action of, on aluminium, 94 Oldbury, England, aluminium works at, 28, 212-215, 270, l71 mode of conducting the reduction at, 271, 272 Omholt, I., furnace of, 354 Opera glas.ses, aluminium, 481 Organic acids, action of, on alumin- ium, 92-97 secretions, action of, on alumin- ium, 98, 99 Osmond, Mr., on the melting point of aluminium-iron alloys, 588 Ostberg, Mr., explanation by, of the rationale of the pro- cess of making mitis castings, 587 on manufacture of ferro-aluminium, 425 on strength of mitis castings, 587 Overbeck and Niewerth, process of, for depositing aluminium, 311, 312 Overheating of aluminium, 452 Oxides, metallic, action of aluminium on, 105, 106 Oxygen, heat given out by elements combining energetically with, 229 INDEX. 657 Osygen, union of hydrogen with, to form water, 226, 227 PACHNOWTE, 121 Painting, protection of aluminium boats by, 478 Pans, evaporating, use of aluminium for, 485 Paracelsus, separation of alum and vitriols by, 2 Paraluminite, 127 J Paris Exposition, 1889, aluminium 1 industry at the, 33 | Parke's process, addition of alumin- ium to the zinc used in, 529, 530 Passaic Art Casting Co., Passaic, N. J., castings in aluminium made by the, 446, 447 Passementerie of aluminium, 76, 475 Patricoft, England, works at, 382 Pearson and Pratt, patent of, for the reduction of aluminium in the iron blast furnace, 420 Ividdon and Pratt, patent of, 404 : Turner and Andrews, claim of, i 413 I Peligot, cupel] ation of aluminium by, 1 450 i Pennsylvania Salt Company, purity of j cryolite from the, 367 use of cryolite by the, 45, 46 Percy, Dr., experiments of , 17 on aluminium bronze, 538 in pig iron, 575 and Dick, experiments of, 283- 285 Periodic classification of the ele- ments, position of aluminium in the, 107, 108 Perspiration, action of, on alumin- ium, 98 Peters, Mr., on the analysis of ferro- aluminiums, 619 Petitjean on preparation of a double sulphide of aluminium and sodium, 177 process of, 408, 409 Petroleum furnace for mitis castings, 585 Philadelphia Public Buildings, coat- ing the iron work of the tower of ' the, with aluminium, 316, 317 Phosphate of lime, action of, on alu- minium, 106 Phosphates of aluminium, 130 Phosphor-aluminium bronze, 571 42 Phosphorus and aluminium, alloys of, 516,517 chloride of, 117, 118 reduction by, 440, 441 Pickling and cleaning aluminium, 456 Pieper; process for preparing artificial cryolite patented by, 170 Pig iron, presence of aluminium in, 574, 575 irons, aluminium in, 423, 427-429 Pionchon on the specific heat of alu- minium, 79 Pittsburgh Reduction Co., 26 aluminium- nickel alloys of the, 511 -titanium alloys ma de by the, 526 cost of pro- ducing al- umini u m bythe,381 enlargement and re- moval of the plant of the, 381, 382 mechanical tests of al- umini u m by the, 70-72 mode of pol- i s h i n g sheet alu- minium used by the, 456 organization and plant of, 376 remelting plant of, 379 suit of the, against the Cowles Co., 346, 347 Testing Laboratory, analyses of commercial aluminium by the,55 6s8 INDEX. Plants, alumina in, 39, 40 Plates, aluminium, 486 Plating on aluminium, 472, 473 Platinum, plating of, on aluminium, 473 Polishing, burnishing and grinding aluminium, 455, 456 Pontoons, aluminium, 476 Potash alum, 128 Potassium aluminate, 114 and sodium, Netto's patents for the reduction of, 31 reduction of aluminium compounds by means of, 246-300 chloride, apparatus for decom- posing, 219 dangers of handling, 181 heat developed in the reaction of, on aluminium chloride, 233 reduction of aluminium sulphide by, 236 salts, voltage required to decom- pose, 237 Pott on the base of alum, 2 Pressing of aluminium ware, 455 Pressure, influence of, on aluminium powder, 66 Proctor, B. S., on the resistance to corrosion of aluminium bronzes, •564, 565 Propeller blades, aluminium bronze for, 568, 569 Puddling, influence of aluminium in, 594 Pumps, use of aluminium bronze for, 567 Purification of aluminium, 447-452 Purple alloy of aluminium and gold, 502 ore, use of, in Castner's sodium process, 208 /QUARTZ, occurrence of, in cryolite, "70 y RAILWAY carriage, aluminium, ! 478 : Rammelsberg, Prof., investigations ' by, of the dif- i f erent states 1 of silicon in aluminium, 5H i on the forms in which silicon i occurs in alu- minium, 609 Reactions, chemical, of aluminium salts. 111 in the Hall process, 384 Reagents, ordinary, impossibility of the reduction of alumina by, 230 reaction with, of neutral solutions of aluminium salts, 111 Reduction by double reaction, 411- 413 furnace, 266 of alumina by acetylene gas, 241 aluminium chloride or alumin- ium-sodium chloride, methods based on the, 246-800 compounds by electric- ity, 236 by other means than sodium or electric- ity, 402-441 theoretically consid- ered, 226-245 cryolite, methods based on the, 274-300 Reflectors, use of aluminium for, 479 Regelsberger, F., on the determina- tion of silicon, 610 Regnault on the specific heat of alu- minium, 77, 78 Reichel on preparation of alumin- ium sulphide, 176 reduction of aluminium sulphide b y cop- per, 417 by iron, 418 Reillon, Montague and Bourgerel, pat- ent of, 409 process for producing alumin- ium sul- phide pat- ented by, 177 Reimar, G. W., statement by, 403 Reinbold, H., recipe of, for deposit- ing aluminium, 312 Republic Mining and Manufacturing Co., 41 Rheinfelden, projected aluminium works at, 395 Rhine Falls, plant at the, 388, 394. 3;v5 Ricciardi on the assimilation of alu- mina by plants, 39, 40 INDEX. 659 Richards, J., alloy of, as an addition t o . t h e galvanizing baa, 529 bronze invented by, oR3 on an aluminium-tin al- loy, 523, 524 on bufl&ng and burnish- ing aluminium, 456,456 solder of, for aluminium, 467-469 Rifle, aluminium bronze, test of an, 566, 567 Riley, E. , analyses by, of mitis metal, 584, 585 Roberts- Austen, Prof. W. C, on alu- minium-gold alloys, 501 , 502 Rocca, manufacture of alum in, 1 Roche on aluminium-antimony al- loys, 496 Rock alum, 1 Rogers, Prof., analysis of pure cryo- lite by, 46 experiments of, in re- ducing sodium com- pounds, 219-222 on wootz steel, 576 process of, H65-368 Rolling aluminium, 453, 454 Roman, B. I., solder of, for alumin- ium, 466, 467 Roscoe, Sir H., on the sodium works at Oldbury, 212-215 Rose, H., experiments of, 17 in the reduc- tion of alu- minium compounds, 274r-283 Rossiter & Co., aluminium boats con- structed by, 478 Rossler, patent of, 530 Rouen, history of the works at, 14 Roussin on the precipitation of alu- minium by magnesium, 437 Rowing shells, aluminium, 478 Royal Gun Foundry, Woolwich, tests of aluminium bronzes in the, 554, 555, 556 Rupp, tests by, of food kept in alu- minium vessels, 94 Ruprecht and Tondi, experiments of, 4 PAARBURGER, letter of, on the Gratzel process, 328 process, 24, 25 Safety-lamps, aluminium, 479 Saint-Michel, Savoy, installation of Minet's pro- cess at, 362 works at, 26 Salindres, apparatus for preparing al- uminium chloride at,. 157-159 expense of the process in: use at, 267, 268 preparation of alumina at, 137-141 principal chemical reac- tions in the process used at, 265 process in use at, 264-268 works at, 15 Saliva, action of, on aluminium, 94 Saloman and Netto, processes of, 31 Salt, common, reaction of, on baux- ite, 142 Salts, basic, of aluminium, 110 metallic, action of solutions of, on aluminium, 100-102 neutral, of aluminium, 110 Saner, C, process of, for soldering aluminium, 464 Sauerwein, process of, for the decom- position of cryolite, 150, 151 Sauvage, F. H., alloy of, 512 Savaresi, experiments of, 4 Savoy, installation of Minet's pro- cess in, 362 Scales, aluminium, 482 Schaffhausen, aluminium works near, 388 _ Schering, use of Gratzel's process by, 328 Schlosser, directions by, for soldering for aluminium bronze, 569, 570 solder for aluminium re- commended by, 462, 463 Schmidt, Dr. O., on the electrolysis of cryolite, 368, 369 Schuch, decomposition of cryolite ac- cording to, 151, 152 Schulze, Fr., test of, 608 Scientific instruments, use of alumin- ium for, 481-483 Sea-water, action of, on aluminium, 97, 98 Secretions, organic, action of, on alu- minium, 98, 99 Sel alumineux, 2 Selenide of aluminium, 1 22 Selenites of aluminium, 129 Selenium andaluminium, alloys of, 519 chloride of, 117 66o INDEX. Self, E. D., test by, of aluminium bronzes, 657, 558 Sellers, Mr., experiments of, on the use of aluminium with iron in casting, 595 Sellon, J. S., process of, for soldering aluminium, 464 Senet, M. L., process of, for deposit- ing aluminium, 311 Sestini, on the solution of alumina in carbonated waters, 131 Sevrard, M., process of, for plating aluminium on copper and brass, 469, 470 Sextant, aluminium, 481, 482 Seymour, F. J., patent of, 432, 433 Shaw, Thos. , phosphor-aluminium bronze of, 571 Sheet-iron, coating of, with alumin- ium, 471, 472 Shimer, P. W., on the occurrence of spinel in blast-furnace slags, 115 Ships, use of aluminium for, 97, 98 Siderite, occurrence of, in cryolite, 149 Siemens, Sir W. , electric furnace of, 27 -Martin steel, basic, effect of alu- minium on, 578 Silicates and borates, action of, on aluminium, 103, 104 of alumina, extraction of alumina from, 142 of aluminium, constitution and properties of, 132 Silicon-aluminium bronze, 570, 571 and aluminium, alloys of, 517-519 bronze, Evrard's process for pro- ducing, 414 condition of the, in aluminium, 56 determination of, in aluminium, 608-611 bronze, 624_ different states of, in aluminium, 56 diminishing the amount of, in al- uminium, 452 double role of, in aluminium, 518, 519 effect of, on aluminium, 518 malleability of alu- minium, 75 melting point of al- uminium, 66 elimination of, from aluminium, 449 experiments on aluminium con- taining, 450, 451 graphitoidal, 56 Silicon, reduction by, 441 r&le of, in aluminium, 53 Silliman, Prof. Benj., experiments of, 6 Silver and aluminium, alloys of, 519- 521 _ analysis of alloys of, 626 chloride, decomposition of, by aluminium, 106 sub-chloride, bromide and iodide of, as a flux in sol- dering aluminium, 466 determination of, in aluminium, 615 plating aluminium with, 473 qualitative test for, 606 salts, voltage required to decom- pose, 237 solutions, action of aluminium on, 101 sulphide, decomposition of, by aluminium, 87 veneering aluminium with, 473 Silvering aluminium, 472 Slag, freeing aluminium from, 447, 448 or flux, influence of, on the al- uminium, 253 Slags, blast-furnace, occurrence of spinel in, 115 composition of, 262, 263 formed in producing bronze, anal- ysis of, 342, 343 f erro- aluminium, analysis of, 342 utilization of aluminous, 148 Smith, Dr., patents of, 432 Smith, Prof. E. F., method of, for de- termining aluminium in iron anfl steel, 62v;, 623 Soci^t^ Anonyme La F?rro-Nickel, aluminium-nickel-copper alloy made by the, 515 Electro-Metallurgique Franjaise, 30 works of the,395, 396 Metallurgique Suisse', 29 plant of the, 388-390 Soda alum, 129 mineral, 45 Sodium, advantages of, over potas- sium, 181 aluminate, 114 precipitation of, 143 INDEX. 66 1 Sodium-aluminium chloride, 117 analyses of the residues from the production of, 210 and aluminium, alloys of, 521 chloride, reduction of, by ~ zinc, 429 manufacture of chloride of, 152-168 sulphide of, 1 11 potassium, Netto's patents for the reduction of, 31 reduction of aluminium compounds by means of, 246-300 apparatus for condensing, 180 reducing, condens- ing and heating in the manufac- ture of, 186 carbonate, separation of, from alumina, 148 cast-iron vessels for producing, 199 Castner's process of manufactur- ing, 203-217 chloride, action of, on alumin- ium, 97, 98 apparatus for decomposing, 219 calories required for the de- composition of, 369 molten, electrolysis of, 222, 223 composition of mixtures used in the manufacture of, 182-184,194 compounds, reduction of, by elec- tricity, 219-225 continuous manufacture of; in cylinders, 190-194 cost of, 22, 201 by Castner's process, 210 crucibles used in the production of, 208 determination of, in aluminium, 615, 616 Devilie's improvements in the manufacture of, 180-194, 197-201 methods of reducing alumin- ium chloride by, 252-257 early manufacture of, in the United States, 17 first patent granted in the United States on the manufacture of, 204 fluoride, injury to crucibles by, 263 furnace for the production of, 208 Sodium furnaces, experiments of Tis- sier Brothers on, 13 heat developed in the reaction of, on aluminium chloride, 233 evolved in action of, on alu- minium fluoride, 235 history of, from Davy to Deville, 179, 180 manufacture of, 179-225 in mercury bottles, 185-190 method employed in the manu- facture of, 182 minor improvements in the man- ufacture of, 201-203 patents, Castner's, 23 perfection in the process of pro- ducing, 10, 11 phosphate, reactions with, of neutral solutions of aluminium salts. 111 process, radical change in the, 22 processes, Cunningham's, 291,292 production of, by Netto's process, 217-219 properties of, 181, 182 quantity of metal reduced by, 258 reactions in the production of, 207, 215-217 reduction by, of aluminium fluo- ride, 294-300 of aluminium compounds by other means than, 402-441 -sodium chloride by, 265-268 sulphide by, 236 salts, voltage required to decom- pose, 237 solid, reduction by, 253-256 substitutes for, in reducing alu- minium, 234 sulphate of, use of, in decompos- ing bauxite, 143 Tissier Bros', method of manu- facturing, 194-197 use of, in melting aluminium, 452 mixtures employed in the manufacture of, 184, 185 vapor, reduction by, 256, 257 yield of, in Castner's process, 210 Solder, Richards', for aluminium, 467-469 Roman's, for aluminium, 466, 467 Sauer's, for aluminium, 464 satisfactory, requirements of a, 457 Sellon's, for aluminium, 464 662 INDEX. Solder, Thowless', for aluminium, 463, 464 Solders, Frishtauth's, for aluminium, 462 Mourey's, for aluminium, 459-461 Schlosser's, for aluminium, 462, 463 Soldering aluminium, 457-469 bronze, 569, 570 Solutions of aluminium salts, reac- tions of reagents upon, ] 1 1 Sound, velocity of, in aluminium, 69 Sounding boards of aluminium, 68, 69 South Carolina, kaolin in, 49 Southern Bauxite and Mining Co., 41 Specific gravity of aluminium, 62-65 molten aluminium, 386 test, 607, 608 Spencer, J. W. , tests by, of the effect of aluminitim on crucible steel, 580, 581 Spiegeleisen, action of cryolite on, 436 Spilsbury, Mr., test of strength of al- uminium wire by, 70 Spinel, 115 Spinning and stamping aluminium, 455 Spoons, aluminium, 486 Sprague on the electro-deposition of aluminium, 315 Springer, Dr. A., on the use of alu- minium for sounding boards, 68. ()9 Spring on compressing aluminium powder, 66 Stahl on the base of alum, 2 Stamping and spinning aluminium, 455 Statistics of the aluminium industry, 34-38 Statuettes, aluminium, 519 Stead, J. E., method of, for determin- ing aluminium in iron and steel, 623 Steel, aluminium, 581 taken up by, 574. 575 Bombay wootz, 422, 576 cast, addition of alumina in the manufacture of, 423 casters, general use of aluminium by, 577, 578 castings, use of ferro-aluminium in making, 577 chrome, aluminium in, 423 determination of aluminium in, 621, 622, 623 high carbon, poor results by add- ing aluminium to, 579 Steel, soft, effect of aluminium on the welding capability of, 579 substitution of aluminium for, 487 Stills, use of aluminium for, 485 Stocker on the occurrence of metallic aluminium, 39 Stoke-on-Trent, works at, 28, 340 Stone-ware, coating of, with alumin- ium, 471 Strange, Mr., on the use of alumiu- ivim bronze for astronomical and philosophical instruments, 567 Strength, tensile and compressive of aluminium, 70-75 Strontium salts, voltage required to decompose, 237 Structure of aluminium compounds, 108-110 Stutzer, Prof. A., on the action of caustic alkalies on aluminium, 100 Styria, deposits of bauxite in, 41 Sulkies, racing, use of aluminium for, 478 Sulphate, native, of alumina, 50, 51 Sulphates, alkaline, action of, on al- uminium, 104 double, of aluminium and other metals, 129 of aluminium, 126, 127 Sulphide of aluminium, 121 reduction of, theo- retically consid- ered, 236 Sulphides, voltage required to de- compose, 238 Sulphur and aluminium, chloride of, 117, 118 hydrogen sulphide, action of, on aluminium 86, 37 heat developed by combining with other elements, 235 order of the af&nity of the metals for, 236 Sulphuretted hydrogen, action of, on alumin- ium, 86, 87 of, on so- lutions of alu- minium salts , 111 gen eration of, from aluminium sul- phide, 121 Sulphuric acid, action of, on alumin- ium, 88-90 INDEX. 663 Surgery, use of aluminium in, 98, 480 Surveying instruments of aluminium, 4S2 Suture-wire, aluminium, 480 Sweden, rise of the mitis process in, 577 ^ Swiss Metallurgic Co., 29 Switzerland, aluminium works in, 388 amount of aluminium produced in, 3(5 n^'ABLE ware, use of aluminium for, 1 486. 487 Tacony Metal Co., Philadelphia, ope- ration of the electric plant of the, 316- 318 works of the, 316 Tarnish on polished aluminium, 98 Taste of aluminium, 67 Taylor, W. J., article by, 17, 18 Tea, action of, on aluminium, 95, 96 -kettles, 447 Tellurium and aluminium, allo5-s of, 521,522 Temperature at which acetylene re- duces alumina, 241 carbon reduces alumina, 240 hydrogen reduces alumina, 240 Terre argilleuse, 2 Tests, compressive, of aluminium, 72 mechanical, of aluminium, 70-72 tensile, of aluminium, 71 transverse, of aluminium, 72 Tetmayer, Prof, test by, of alumin- ium brasses, 532 tests by, of alumin- ium bronzes, 559 Thenard, M., recommendation by, 9, j 10 Thermal chemistry, reduction of alu- j minium compounds from the standpoint of, 226-245 conductivity of aluminium, 82 Thomas and Tilly, patent of. for coat- ing metals with aluminium, 307, 308 Thompson and White, improvements by, in the manufacture of sodium, 202, 203 patent, 290 Thompson, J. B., process of, for depos- iting aluminium, 308 R. T., on the analysis of ferro - aluminiums, 619, 620 W. P., discovery by, of corundum in the United States, 47 on the production of aluminium by Cowles Bros', process, 333-339 patent of, 419, 420 Thomson, G. W., on the influence of aluminium in puddling iron, 594, 595 J., process of, for preparing alumina from cryolite by the dry way, 144-147 Thonichte erde, 2 Thowless, O. M., process of, for man- ufacturing sodi- um, 203 proposition of, 403, 404 solder of, for alu- minium, 463, 464 Thurston, Prof., on the drawing ca- pacity of aluminium, 454 Tiers Argent, 520, 521 Tilghman, method of, for preparing alumina, 135, 136 Tin and aluminium, alloys of, 522-525 analysis of alloys of, 626 determination of, in aluminium, 615 bronze, 624 ' foil, effect of a small addition of aluminium on, 524 properties imparted to, by alu- minium, 523 qualitative test for, 607 reduction by, 439, 440 of aluminium sulphide by, 236 use of, in soldering aluminium, 459 Tissier Brothers, controversy be- tween, and De- ville, 13, 14 experiments on so- dium furnaces by, 13 history by, of the works at Rouen, 14 method of, 287,288 664 INDEX. Tissier Brothers, on action of alka- line s u 1 - phates and carbonates on alumin- ium, 104 of alumin- ium on me- tallic ox- ides, 105, 306 aluminium-anti- mony al- loys, 495 -bismuth al- loys, 497 bronze, 538, 539 -gold alloys, 501 -iron alloys, 573 -nickel al- loys, 510 -pi a t i n u m alloys,517 -tin alloys, 523 amalgamation of aluminium, 506 application o f aluminium to cast-iron, 595 gilding alumin- ium, 472 the effect of iron on alumi n - 1 ium, 572 process of, for the manufacture of sodium, 194-197 work by, on alu- minium, 15, 16 Titanic .acid, constancy of, in Ameri- 1 can bauxites, 45 Titanium and aluminium, alloys of, 525-527 determination of, in aluminium, 617 in aluminium, 53 Tomlinson on the specific heat of al- uminium, 78 Tondi and Ruprecht, experiments of, 4 Torpedo boat of aluminium, 477 Transit instruments, aluminium, 482 Trusses, aluminium, 480 Tubes, manufacture of, 454 Tungsten and aluminium, alloys of, 527 Tuning forks, aluminium, 67 Turquois, 131 Type metal, MacKellar's, 504 UNIONVILLE Corundum Mines Co., 48 United States Aluminium Metal Co., organization and plant of, 396 amount of aluminium pro- duced in the, 37 Army, use of aluminium in tlae, 476 Co., plant of the, 382, 383 cryolite in the, 46 deposits of bauxite in, 41 early experiments in, 17 first discovery of corundum in the, 47 patent on the manufac- ture of sodium granted in the, 204 ! H^roult alloy process in the, 30, 31 kaoliu in the, 49 manufacture of aluminium culinary utensils in the, 485 Mitis Co., organization of, 682, 583 production of corundum in the, 47 Unwin, Prof, test by, of aluminium bronzes, 557 Uses, miscellaneous, of aluminium, 490 *■ VALENCY of aluminium in its compounds, 109 Valoirette, use of, to operate Minet's process, 362 "Vapor of aluminium, color of, 66 Vehicles, use of aluminium for, 478 "Vendenesse," the, 477 Veneering other metals with alumin- ium, 473 Very, Prof l-<\, on the magnetism of aluminium, 67 Vessels, use of aluminium in build- ing, 476 Villeveyrac (HSroult), bauxite from, 44 Vinegar, action of, on aluminium, 92-97 Vitriols and alums, separation of, 2 INDEX. 665 Volatilization of aluminium, 66 Voltage, equation for the, required to decompose alumina, 239 required for decomposition at high tempera- tures, 302, 303 Minet's bath, 360, 361 in Hall's process, 378 H^roult's process, 392 to decompose anhy- drous molten sub- stances, 237 WAGNBR, R., improvements by, in the manufac- ture of sodium, 201,202 process for prepar- ing alumina pro- posed by, 142, 143 Wagons, ammunition, of aluminium, 476 Wahl and Greene, use of aluminium by, 436 Walker, A., patents of, for the electro- deposition of aluminium, 313, 314 Wanner, M., claims of, 441 Warren, H., experiments of, 363, 364 reduction by, of alumina with hydrogen, 407 H. N., boron-aluminium bronze of, 571 on aluminium-arse- nic alloys, 497 -boron a 1 - loys, 498 process for produc- ing anhydrous me- tallic chlorides re- commended b y , 165, 166 Washington, England, aluminium ■works at, 18 Monument, aluminium tip on the, 33 Navy Yard, tests of bronzes at the, 554, 556 Water, action of, on aluminium, 85, 86 electro-motive force required to decompose, 303 union of hydrogen with oxygen to form, 226, 227 Watertown Arsenal, tests of Cowles' bronzes at the, 555, 656, 557 Watt, A., on the electro-deposition of aluminium, 316 Wavellite, 131 Weber, decomposition of cryolite in the establishment of, 151 Webster Crown Metal Co., bronzes containing nickel made by the, 512-515 Mr. , bronzes of, containing nickel, 512-515 inventions of, 21, 22 process of, for preparing alu- mina, 136,137 Wedding, Mr., on Basset's process for obtaining aluminium, 431 Wegner and Guhrs, flux in soldering aluminium re- commended by, 466 process of, for plating a 1 u - minium, 473 Weights, aluminium, 482 Welding aluminium, 457 Weldon, W., on the prospects of the aluminium industry, 20, 21 process of, 436 Wellman, aluminium boats in the expedition of, 478 Werner, E., flux in soldering alu- minium recommended by, 466 West, Thomas D., on casting alu- minium bronze, 549-552 Wheelbarrows, aluminium, 487 Wilde, A. E-, invention of, 435, 436 Williams Aluminium Co., New York, aluminium- ferro - sili- con of the, 595 manufac- ture of al- uminium - ferro - sili- con by, 427 Willson, Mr., process of, 399 Winckler, A., patent of, 399 Dr. C, experiments of, in reducing a 1 u - mina by mag- nesium, 229, 230 on coating metals with alumin- ium, 470, 471 666 INDEX. Winckler, Dr. C, on electro-deposi- tion of a 1 u - minium, 315 reduction of alu- mina by mag- nesium, 437, 438 retrospect by, of the art of work- ing aluminium, 18,19 Wine, action of, on aluminium, 94, 95 Wirtz & Co., aluminium works of, 18 Wittenstroem and Nobel, discovery by, 582 patent of, for use of aluminium in casting wrought iron and steel, 577 Wocheinite, 41 Wohler, F., experiments of, 7, 8 in reduc- ing alu- minium c o m - pounds, 247-250 modifications by, of re- ducing cryolite, 289 on aluminium-arsenic al- lo);s, 497 -calcium alloys, 498, 499 -chromium a 1 - loys, 499 -magnesium al- loys, 504, 505 -molybdenum alloys, 509,510 -phosphorus al- loys, 516, 517 - s e 1 e nium al- loys, 519 -tellurium a 1 - loys, 521, 522 -titanium alloys, 525 process of, for preparing aluminium chloride, 152 Wootz steel, Bombay, 422, 576 Worcester, Mass., plant for the manu- facture of mitis castings at, 582 Working aluminium bronzes, 561, 562 in aluminium, 442-491 Wright, Dr. C.R. A.,on aluminium-an- timony al- loys, 495, 496 -cadmium alloys, 498 Wrought iron castings, causes for blow holes in, 590-592 effect of aluminium on, 581-595 explanation of the in- creased fluidity of, by the addition of alumin- ium, 589, 590 YACHTS, aluminium, 476 Yates, H. N., on the analysis of ferro-aluminiums, 618, 619 yDZIARSKI, A., patent of, .'^64 /y Zinc aluminate, 115 and aluminium, alloys of, 528- 530 analysis of, copper and aluminium, alloys of, 580-533 determination of, in aluminium, 614, 615 bronze, 625 minute quantities in alumin- ium, 626 effect of, on aluminium, 528 industry, use of aluminium in the, 529, 530 oxide, action of aluminium on, 105 qualitative test for, 606, 607 r e a c tion of, on aluminium chloride, 235 reduction by or in presence of, 429-435 of aluminium sulphide by, 236 salts, voltage required to de- compose, 237 separation of, from aluminium, 450 solutions, action of aluminium on, 102 use of, in soldering aluminium, 459 JANNEY&STEIIMMETZ No. 421 CHESTNUT STREET Philadelphia, Pa. ALUMINUM Cable Address: { /-\ | j_ j "ALUMINUM." Ingots, Sheet, Plates, Foil, Leaf, Rods, Wire, Bars, Tubing, Castings, Solder and Alloys. Pure Ingot Aluiniiiuni for Steel Plants and Foundries. (1) THE Pittsburgh Reduction Co. MANUFACTURERS OF ALUMINUM INGOTS, BARS, SHEET, WIRE, TUBES AND CASTINGS. T.P.R.Co. .tV ^y ALIUM Trade Mark MAIN OFFICES, to which all correspondence should bedirected, No. 121 THIRD AVENUE, PITTSBURGH, PA., U.S.A. WORKS: New Kensington, Westmoreland County, Pa. Niagara Falls, Niagara County, N. Y. New York Store, No. 4 Havemeyer Building, Cliurcii and Dey Streets, Cliicago Store, No. 132 Lake Street, Pliiladelplila Store, No. 360 Bullitt Building. (2) Mr. JOSEPH RICHARDS- Delaware Metal Refinery, Eighteentli Street and Washington Avenue, Philadelphia, Pa., U. S. A. Patentee of Richards' Solder for Aluminium. Agents for the United States, Messrs. Janney & Stelnmetz, 421 Cheistnut Street, Philadelphia. Agent for Great Britain, W. Archibald Brlggs, Dundee, Scotland. Agents for Europe (Continent), The Aluminium Industrie Actien Gesellschaft, Neuhausen, Switzerland. Patentee of The Use Of Aluminium in Galvanizers' Baths. Patentee of The Use of Aluminium in Refining Zinc. Inventor of Richards' Hardened Aluminium. Specially adapted for castings of great strength and rigidity. Inventor of Richards' Bronze. Equal to Manganese Bronze or Phosphor Bronze, at t\vo-thirds the cost. CHARLES METCALF. JOHN M. FERGUSON. METCALF & FERQUSON, Cast, Forged, Pressed, Stampe^i Wire and Drawn Shapes, Rivets. 709 Ferguson Block, Pittsburgh, Pa., U.S. A. (3) The Aluminum World. A Journal for Manufacturers of Aluminum and its Alloys, Dealers in Alumi- num Goods, and for the Metal Industry in General, with Special Reference to the Reduction of Ores by Electricity. Published at No. 14 Lafayette Place, New York. SPECIAL CONTRIBUTORS. Mr. Alfred E. Hunt, President of the Pittsburgh Reduction Company. Prof. Joseph W. Richards, Dr. C. W. Hayes, Lehigh University, Bethlehem, Pa. United States Geological Survey. Charles N. Butler, Attorney in Patent Cases, Philadelphia. Joseph A. Steinmetz, Heinrich Ries, Philadelphia. Columbia College School of Mines. Subscription in the United States, Canada and Mexico . $2.00 Foreign Subscription ...... 3.00 ADVERTISING RATES ON APPLICATION. Subset iptions. Advertisements and News will be received at the following offices : New York— 25 Broad Street Palmer H. Langdon. Philadelphia— 423 Chestnut Street - Janney & Steinmetz. Pittsburgh— 701 Ferguson Block = E. Blair Allen. Chicago— 123 Fifth Avenue = - James Langland. London, England — 57 Holbcrn Viaduct - W. Durrant. THE ALUMINUin WORLD, 14 Lafayette Place, New York City, U. S. A (-•) INDUSTRIAL LITERATURE Civilization without Diversified Industries is an Impossibility and all History Bears Witness to this Great Truth. H.C.B. CATALOGUE OF Practical and Scientific Books PUBLISHED BY Henry Carey Baird & Co. INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS. 810 Walnut Street, Philadelphia. 4^ Any of the Books comprised in this Catalogue will be sent by mail, free of postage, to any address in the world, at the publication prices. 4®* A Descriptive Catalogue. 94 pages, 8vo., will be sent free and free of postage, to any one in any part ot the world, who will furnish his address. 4S- Where not otherwise stated, all of the Books in this Catalogue are bound in muslin. AMATEUR MECHANICS' WORKSHOP: A treatise containing plain and concise directions for the manipulation of Wood and Metals, including Casting, Forg- ing, Brazing, Soldering and Carpentry. By the author of the "Lathe and Its Uses." Seventh edition. Illustrated. 8vo ■ • 52.50 ARLOT.— A Complete Guide for Coach Painters: Translated from the French of M. Arlot, Coach Painter, for eleven years Foreman of Painting to M. Eherler, Coach Maker, Paris. By A. A. Fesquet, Chemist and Engineer. To which is added an Appendix, containing Information re- specting the Materials and the Practice of Coach and Car Painting and Varnishing in the United States and Great Britain. i2rao |i.25 2 HENRY CAREY BAIRD & CO.'S CATALOGUE ARMENGAUD, AMOROUX, AND JOHNSON.— The Prac- tical Draughtsman's Book of Industrial Design, and Machinist's and Engineer's Drawing Companion: Forming a Complete Course of Mechanical Engineering and Architectural Drawing. From the French of M. Armengaud the elder, Prof, of Design in the Conservatoire of Arts and Industry, Paris, and M. Armengaud the younger, and Amo- roux. Civil Engineers. Rewritten and arranged with addi- tional matter and plates, selections from and examples of the most useful and generally employed mechanism of the day. By William Johnson, Assoc. Inst. C. E. Illustrated by fifty folio steel plates, and fifty wood-cuts. A new edi- tion, 4to., cloth $5.00 ARROWSMITH.— The Paper-Hanger's Companion: Comprising Tools, Pastes, Preparatory Work; Selection and Hanging of Wall- Papers; Distemper Painting and Cornice- Tinting; Stencil Work; Replacing Sash-Cord and Broken Window Panes; and Useful Wrinkles and Receipts. By James Arrowsmith. a New, Thoroughly Revised, and Much En- larged Edition. Illustrated by 25 engravings, 162 pages. (1905) $100 ASHTON.— The Theory and Practice of the Art of Design- ing Fancy Cotton and Woolen Cloths from Sample: Giving full instructions for reducing drafts, as well as the methods of spooling and making out harness for cross drafts and finding any required reed; with calculations and tables of yarn. By Frederic T. Ashton, Designer, West Pittsfield, Mass. With fifty-two illustrations. One vol. folio ?4.oo ASKINSON. — Perfumes and and their Preparation : A Comprehensive Treatise on Perfumery, containing Complete Directions for Making Handkerchief Perfumes, Smelling- Salts, Sachets, Fumigating Pastils; Preparations for the Care of the Skin, the Mouth, the Hair; Cosmetics, Hair Dyes, and other Toilet Articles. By G. W. Askinson. Translated from the German by Isidor Furst. Revised by Charles Rice. 32 Illustrations. 8vo $3.00 BEANS. — ^A Treatise on Railway Curves and Location of Railroads: By E. W. Beans, C. E. Illustrated. i2mo. Morocco. .$1.00 BELL. — Carpentry Made Easy: Or, The Science and Art of Framing on a New and Improved System. With Specific Instructions for Building Balloon Frames, Barn Frarnes, Mill Frames, Warehouses, Church Spires, etc. Comprising also a System of Bridge Building, with Bills, Estimates of Cost, and valuable Tables. lUus- HENRY CAREY BAIRD & CO.'S CATALOGUE 3 trated by forty-four plates, comprising nearly 200 figures. By William E. Bell, Architect and Practical Builder. 8vo $5.00 BERSCH.— Cellulose, Cellulose Products, and Rubber Substitutes: Comprising the Preparation of Cellulose, Parchment-Cellu- lose, Methods of Obtaining Sugar, Alcohol, and Oxalic Acid from Wood-Cellulose; Production of Nitro-Cellulose and Cellulose Esters; Manufacture of Artificial Silk, Viscose, Celluloid, Rubber Substitutes, Oil-Rubber, and Faktis. By Dr. Joseph Bersch. Translated by William T. Brannt. 41 Illustrations. (1904.) JS3.00 BILLINGS.— Tobacco : Its History, Variety, Culture, Manufacture, Commerce, and Various Modes of Use. By E. R. Billings. Illustrated by nearly 200 engravings. 8vo $3.00 BIRD. — The American Practical Dyers' Companion: Comprising a Description of the Principal Dye-Stuffs and Chemicals used in Dyeing, their Natures and Uses; Mor- dants and How Made; with the best American, English, French and German processes for Bleaching and Dyeing Silk, Wool, Cotton, Linen, Flannel, Felt, Dress Goods, Mixed and Hosiery Yarns, Feathers, Grass, Felt, Fur, Wool, and Straw Hats, Jute Yarn, Vegetable Ivory, Mats, Skins, Furs, Leather, etc., etc., by Wood, Aniline, and other Processes, together with Remarks on Finishing Agents, and Instructions in the Finishing of Fabrics, Substitutes for Indigo, Water- Proofing of Materials, Tests and Purification of Water. Manufacture of Aniline and other New Dye Wares, Harmoniz- ing Colors, etc., etc.; embracing in all over 800 Receipts for Colors and Shades, accompanied by 170 Dyed Samples of Raw Materials and Fabrics. By F. J. Bird, Practical Dyer, Author of "The Dyers' Hand-Book. " 8vo $4.00 BIJNN. — ^A Practical Workshop Companion for Tin, Sheet- Iron, and Copper-plate Workers: Containing Rules for describing various kinds of Patterns used by Tin, Sheet-Iron and Copper-plate Workers; Practical Geometry; Mensuration of Surface and Solids; Tables of the Weights of Metals, Lead-pipe, etc.; Tables of Areas and Circumferences of Circles; Japan, Varnishes, Lacquers, Ce- ments, Compositions, etc., etc. By Leroy J. Blinn, Master Mechanic. With One Hundred and Seventy Illustrations. i2mo $2.50 BOOTH. — Marble Worker's Manual: Containing Practical Information respecting Marbles in general, their Cutting, Working and Polishing; Veneering of Marble; Mosaics; Composition and Use of Artificial Marble, 4 HENRY CAREY BAIRD & CO.'S CATALOGUE Stuccos, Cements, Receipts, Secrets, etc., etc. Translated from the French by M. L. Booth. With an Appendix con- cerning American Marbles. l2mo., cloth $1-50 BRANNT.— A Practical Treatise on Animal and Vegetable Fats and Oils: Comprising both Fixed and Volatile Oils, their Physical and Chemical Properties and Uses, the Manner of Extracting and Refining them, and Practical Rules for Testing them; as well as the Manufacture of Artificial Butter and Lubricants, etc., with lists of American Patents relating to the Extraction, Rendering, Refining, Decomposing and Bleaching of Fats and Oils. By William T. Brannt, Editor of the "Techno- Chemical Receipt Book." Second Edition, Revised and in great part Rewritten. Illustrated by 302 Engravings. In Two Volumes. 1304 pp. 8vo $10.00 BRANNT.— A Practical Treatise on Distillation and Rec- tification of Alcohol: Comprising Raw Materials; Production of Malt, Preparation of Mashes and of Yeast; Fermentation; Distillation and Rectification and Purification of Alcohol; Preparation of Alcoholic Liquors, Liqueurs, Cordials, Bitters, Fruit Essences, Vinegar, etc.; Examination of Materials for the Preparation of Malt as well as of the Malt itself; Examination of Mashes before and after Fermentation; Alcoholometry, with Numer- ous Comprehensive Tables; and an Appendix on the Manu- facture of Compressed Yeast and the Examination of Alcohol and Alcoholic Liquors for Fusel Oil and other Impurities. By William T. Brannt, Editor of "The Techno-Chemical Receipt Book.'' Second Edition. Entirely Rewritten. Illustrated by 105 engravings. 460 pages, 8vo. (Dec, 1903) $12.50 BRANNT.— India Rubber, Gutta-Percha and Balata: Occurrence, Geographical Distribution, and Cultivation, Ob- taining and Preparing the Raw Materials, Modes of Working and Utilizing them, including Washing, Maceration, Mixing, Vulcanizing, Rubber and Gutta-Percha Compounds, Utiliza- tipn of Waste, etc. By William T. Brannt. Illustrated. i2mo. A new edition in preparation. BRANNT.— A Practical Treatise on the Manufacture of Vinegar and Acetates, Cider, and Fruit-Wines: Preser\'ation of Fruits and Vegetables by Canning and Evap- oration; Preparation of Fruit-Butters, Jellies, Marmalades, Catchups, Pickles, Mustards, etc. Edited from various sources. By .William T. Brannt. Illustrated by 79 En- gravings. 479 pp. 8vo (Scarce) BRANNT.— The Metallic Alloys: A Practical Guide For the Manufacture of all kinds of Alloys, Amalgams, and Solders.^used by Metal Workers: together with their Chemical HENRY CAREY BAIRD & CO.'S CATALOGUE 5 and Physical Properties and their Application in the Arts and the Industries; with an Appendix on the Coloring of Alloys and the Recovery of Waste Metals. By William T. Brannt. 45 Engravings. Third, Revised, and Enlarged Edition. 570 pages. 8vo Net, $5.00 BRANNT.— The Metal Worker's Handy-Book of Receipts and Processes: Being a Collection of Chemical Formulas and Practical Manipulations for the working of all Metals; including the Decoration and Beautifying of Articles Manufactured there- from, as well as their Preservation. Edited from various sources. By William T. Brannt. Illustrated. i2mo. .$2.50 BRANNT.— Petroleum : Its History, Origin, Occurrence, Production, Physical and Chemical Constitution, Technology, Examination and Uses; Together with the Occurrence and Uses of Natural Gas. Edited chiefly from the German of Prof. Hans Hoefer and Dr. Alexander Veith, by Wm. T. Brannt. Illustrated by 3 Plates and 284 Engravings. 743 pp. 8vo $12.50 BRANNT.— The Practical Dry Cleaner, Scourer and Garment Dyer: Comprising Dry, Chemical, or French Cleaning; Purifica- tion of Benzine; Removal of Stains, or Spotting; Wet Clean- ing; Finishing Cleaned Fabrics; Cleaning and Dyeing Furs, Skin Rugs and Mats; Cleaning and Dyeing Feathers; Clean- ing and Renovating Felt, Straw and Panama Hats; Bleach- ing and Dyeing Straw and Straw Hats; Cleaning and Dyeing Gloves; Garment Dyeing; Stripping, Analysis of Textile Fabrics. Edited by William T. Brannt, Editor of "The Techno-Chemical Receipt Book." Fourth Edition, Revised and Enlarged. Illustrated by Forty-One Engravings. 12 mo. 371 pp $2.50 CONTENTS: I. Dry Chemical or French Cleaning. II. Removal of Stains, or Spotting. III. Wet Washing. IV. Finishing Cleaned Fabrics. V. Cleaning and Dyeing Furs, Skin Rugs and Mats. VI. Cleaning and Dye- ing Feathers. VII. Cleaning " and Renovating Felt, Straw and Panama Hats; Bleaching and Dyeing Straw and Straw Hats. VIII. Cleaning and Dyeing Gloves. IX. Garment Dyeing. X. Stripping Colors from Gar- ments and Fabrics. XI. Analysis of Textile Fabrics. Index. BRANNT.— The Soap Maker's Hand-Book of Materials Processes and Receipts for every description of Soap includ- ing Fats, Fat Oils and Fatty Acids; Examination of Fats and Oils; Alkalies; Testing Soda and Potash; Machines and Utensils; Hard Soaps; Soft Soaps; Textile Soaps; Washing Pov^ders and Allied Products; Toilet Soaps, Medicated Soaps, and Soap Specialties; Essential Oils and other Perfum- ing Materials; Testing Soaps. Edited chiefly from the German of Dr. C. Deite, A. Engelharut, F. Wiltner, 6 HENRY CAREY BAIRD & CO.'S CATALOGUE and numerous other Experts. With Additions by William T. Brannt, Editor of "TheTechno-Chemical Receipt Book." Illustrated by Fifty-Four Engravings. Second edition, Re- vised and in great part Re- Written. 535 pp. 8vo JS6.00 BRANNT. — Varnishes, Lacquers, Printing Inks and Seal- ing Waxes: Their Raw Materials and their Manufacture, to which is added the Art of Varnishing and Lacquering, including the Preparation of Putties and of Stains for Wood, Ivory, Bone, Horn, and Leather. By William T. Brannt. Illustrated by 39 Engravings, 338 pages. i2mo $3-oo BRANNT— WAHL.— TheTechno-Chemical Receipt Book: Containing several thousand Receipts covering the latest, most important, and most useful discoveries in Chemical Technology, and their Practical Application in the Arts and the Industries. Edited chiefly from the German of Drs. Winckler, Eisner, Heintze, Mierzinski, Jacobsen, Keller and Heinzerling, with additions by Wm. T. Brannt and Wm. H. Wahl, Ph. D. Illustrated by 78 engravings. l2mo. 495 pages I2.00 BROWN. — Five Hundred and Seven Mechanical Move- ments: Embracing all those which are most important in Dynamics, Hydraulics, Hydrostatics, Pneumatics, Steam Engines, Mill and other Gearing, Presses, Horology, and Miscellaneous Machinery; and including many movements never before published, and several of which have only recently come into use. By Henry T. Brown $1.00 BULLOCK.— The Rudiments of Architectui'e and Build- ing: For the use of Architects, Builders, Draughtsmen, Machin- ists, Engineers and Mechanics. Edited by John Bullock, author of "The American Cottage Builder." Illustrated by 250 Engravings. 8vo ^2.50 BYRNE.— Hand-Book for the Artisan, Mechanic, and Engineer: Comprising the Grinding and Sharpening of Cutting Tools, Abrasive Processes, Lapidary Work, Gem and Glass En- graving, Varnishing and Lacquering, Apparatus, Materials and Processes for Grinding and Polishing, etc. By Oliver Byrne. Illustrated by 185 wood engravings. 8vo $4.00 BYRNE.— Pocket-Book for Railroad and Civil Engineers: Containing New, Exact and Concise Methods for Laying out Railroad Curves, Switches, Frog Angles and Crossings; the Staking out of work; Levelling; the Calculation of Cuttings; Embankments; Earthwork, etc. By Oliver Byrne. i8mo., full bound, pocketbook form ; $1.50 HENRY CAREY BAIRD & CO.'S CATALOGUE 7 BYRNE.— The Practical Metal- Worker's Assistant: Comprising Metallurgic Chemistry; the Arts of Working all Metals and Alloys; Forging of Iron and Steel; Hardening and Tempering; Melting and Mixing; Casting and Founding; Works in Sheet Metals; the Process Dependent on the Duc- tility of the Metals; Soldering; etc. By John Percy. The Manufacture of Malleable Iron Castings, and Improvements in Bessemer Steel. By A. A. Fesquet, Chemist and En- gineer. With over Six Hundred Engravings, Illustrating every Branch of the Subject. 8vo $3-5o CABINET MAKER'S ALBUM OF FURNITURE: Comprising a Collection of Designs for various Styles of Furniture. Illustrated by Forty-eight Large and Beau- tifully Engraved Plates. Oblong, 8vo $1.50 CALLINGHAM.— Sign Writing and Glass Embossing: A complete Practical Illustrated Manual of the Art. By James Callingham. To which are added Numerous Alpha- bets and the Art of Letter Painting Made Easy. By James C. Badenoch. 258 pages. i2mo $1.50 CAREY.— A Memoir of Henry C. Carey: By Dr. Wm. Elder. With a portrait. Svo., cloth 75 CAREY.— The Works of Henry C. Carey: Manual of Social Science. Condensed from Carey's "Principles of Social Science." By Kate McKean. i vol. i2mo $2.00 Miscellaneous Works. With a Portrait. 2 vols. 8vo. $10.00 Past, Present and Future. 8vo $2.50 Principles of Social Science. 3 volumes, 8vo $10.00 The Slave-Trade, Domestic and Foreign; Why it Exists, and How it may be Extinguished (1853). 8vo $2.00 The Unity of Law: As Exhibited in the Relations of Phys- ical, Social, Mental and Moral Science (1872). 8vo $2.50 COOLEY. — A Complete Practical Treatise on Perfumery: Being a Hand-book of Perfumes, Cosmetics and other Toilet Articles, with a Comprehensive Collection of Formulae. By Arnold Cooley. i2mo $1.00 COURTNEY.^The Boiler Maker's Assistant In Drawing, Templating, and Calculating Boiler Work and Tank Work, etc. Revised by D. K. Clark. 102 ills. Fifth edition 80 COURTNEY.— The Boiler Maker's Ready Reckoner: With Examples of Practical Geometry and Templating. Re- vised by D. K. Clark, C. E. 37 illustrations. Fifth edi- tion r $i-6o 8 HENRY CAREY BAIRD & CO.'S CATALOGUE CRISTIANI.— A Technical Treatise on Soap and Candles: With a Glance at the Industry of Fats and Oils. By R. S. Cristiani, Chemist. Author of "Perfumery and Kindred Arts. " Illustrated by 176 engravings. 581 pages, 8vo. .I15.00 CROSS.— The Cotton Yarn Spinner: Showing how the Preparation should be arranged for Differ- ent Counts of Yarns by a System more uniform than has hith- erto been practiced; by having a Standard Schedule from which we make all our Changes. By Richard Cross. 122 pp. i2mo 75 DAVIDSON.— A Practical Manual of House Painting, Graining, Marbling, and Sign-Writing: Containing full information on the processes of House Paint- ing in Oil and Distemper, the Formation of Letters and Practice of Sign-Writing, the Principles of Decorative Art, a Course of Elementary Drawing for House Painters, Writers, etc.", and a Collection of Useful Receipts. With nine colored illustrations of Woods and Marbles, and numerous wood en- gravings. By Ellis A. Davidson. i2mo $2.00 DA VIES. — A Treatise on Earthy and Other Minerals and Mining: By D. C. Davies, F. G. S., Mining Engineer, etc. Illustrated by 76 Engravings. l2mo fc.oo DAVIES.— ^A Treatise on Metalliferous Minerals and Mining: By D. C. Davies, F. G. S., Mining Engineer, Examiner of Mines, Quarries and Collieries. Illustrated by 148 engrav- ings of Geological Formations, Mining Operations and Ma- chinery, drawn from the practice of all parts of the world. Fifth Edition, thoroughly Revised and much Enlarged by his son, E. Henry Davies. l2mo. 524 pages $5-00 DAVIS. — A Practical Treatise on the Manufacture of Brick, Tiles and Terra-Cotta: Including Stiff Clay, Dry Clay, Hand Made, Pressed or Front, and Rbadway Paving Brick, Enamelled Brick, with Glazes and Colors, Fire Brick and Blocks, Silica Brick, Carbon Brick, Glass Pots, Retorts, Architectural Terra-Cotta, Sewer Pipe, Drain Tile, Glazed and Unglazed Roofing Tile, Art Tile, Mo.saics, and Imitation of Intarsia or Inlaid Surfaces. Comprising every product of Clay employed in Architecture, Engineering, and the Blast Furnace. With a Detailed Description of the Differ- ent Clays employed, the Most Modern Machinery, Tools, and Kilns used, and the Processes for Handling, Disintegrat- ing, Tempering, and Moulding the Clay into Shape, Drying, Setting, and Burning. By Charles Thomas Davis. Third Edition. Revised and in great part rewritten. Illustrated by 261 engravings. 662 pages ■ (Scarce.) HENRY CAREY BAIRD & CO.'S CATALOGUE 9 DAVIS.— The Manufacture of Paper: Being a Description of the various Processes for the Fabrica- tion, Coloring and Finishing of every kind of Paper, Includ- ing the Different Raw Materials and the Methods for De- termining their Values, the Tools, Machines and Practical Details connected with an intelligent and a profitable prose- cution of the art, with special reference to the best American Practice. To which are added a History of Paper, complete Lists of Paper-Making, Materials, List of American Machines, Tools and Processes used in treating the Raw Materials, and in Making, Coloring and Finishing Paper. By Charles T. Davis. Illustrated by 156 Engravings. 608 pages. ' 8vo. $6.00 DAWIDOWSKY— BRANNT.— A Practical Treatise on the Raw Materials and Fabrication of Glue, Gelatine, Gelatine Veneers and Foils, Isinglass, Cements, Pastes, Mucilages, etc.: Based upon Actual Experience. By F. Dawidowsky, Tech- nical Chemist. Translated from the German, with extensive additions, including a description of the most Recent American Processes, by William T. Brannt. 2d revised edition, 350 pages. (1965.) Price $3-00 DEITE. — ^A Practical Treatise on the Manufacture of Perfumery: Comprising directions for making all kinds of Perfumes, Sachet Powders, Fumigating Materials, Dentifrices, Cos- metics, etc., with a full account of the Volatile Oils, Balsams, Resins, and other Natural and Artificial Perfume-substances, including the Manufacture of Fruit Ethers, and tests of their purity. By Dr. C. Deite, assisted by L. Borchert, F. EiCHBAUM, E. Kugler, H. Toeffner, and other experts. From the German, by Wm. T. Brannt. 28 Engravings. 358 pages. 8vo iPS-OO DE KONINCK— DIETZ.— A Practical Manual of Chemical Analysis and Assaying: As applied to the Manufacture of Iron from its Ores, and to Cast Iron, Wrought Iron, and Steel, as found in Commerce. By L. L. DeKoninck, Dr. Sc, and E. Dietz, Engineer. Ed- ited with Notes, by Robert Mallet, F. R. S., F. S. G., M. I C. E., etc. American Edition, Edited with Notes and an Appendix on Iron Ores, by A. A. Fesquet, Chemist and Engineer. i2mo jsi.oo DIETERICHS.— A Treatise on Friction, Lubrication, Oils and Fats: The Manufacture of Lubricating Oils, Paint Oils, and ot Grease, and the Testing of Oils. By E. F. Dieterichs, 10 HENRY CAREY BAIRD & CO.'S CATALOGUE Member of the Franklin Institute; Member National Associa- tion of Stationary Engineers; Inventor of Dieterichs' Valve- Oleum Lubricating Oils. i2mo. (1906.) A practical book by a practical man $i-25 DUNCAN. — Practical Surveyor's Guide: Containing the necessary information to make any person of common capacity, a finished land surveyor, without the aid of a teacher. By Andrew Duncan. Revised. 72 Engrav- ings. 214 pp. i2mo $1.50 DUPLAIS.— A Treatise on the Manufacture and Dis- tillation of Alcoholic Liquors: Comprising Accurate and Complete Details in Regard to Alcohol from Wine, Molasses, Beets, Grain, Rice, Potatoes, Sorghum, Asphodel, Fruits, etc.; with the Distillation and Rectification of Brandy, Whiskey, Rum, Gin, Swiss Absinthe, etc., the Preparation of Aromatic Waters, Volatile Oils or Essences, Sugars, Syrups, Aromatic Tinctures, Liqueurs, Cordial Wines, Effervescing Wines, etc., the Ageing of Brandy and the improvement of Spirits, with Copious Directions and Tables for Testing and Reducing Spirituous Liquors, etc., etc. Translated and Edited from the French of MM. Du- PLAis. By M. McKennie, M. D. Illustrated. 743 pp. 8vo *i5-oo EDWARDS.— A Catechism of the Marine Steam- Engine: For the use of Engineers, Firemen, and Mechanics. A Prac- tical Work for Practical Men. By Emory Edwards, Me- chanical Engineer. Illustrated by sixty-three Engravings, including examples of the most modern Engines. Third edition, thoroughly revised, with much additional matter. i2mo. 414 pages $1.50 EDWARDS. — ^American Marine Engineer, Theoretical and Practical: With Examples of the latest and most approved American Practice. By Emory Edwards. 85 Illustrations. lamo. $1.50 EDWARDS. — Modern American Locomotive Engines: Their Design, Construction and Management. By Emory Edwards. Illustrated. i2mo $1.50 EDWARDS. — 900 Examination Questions and Answers: For Engineers and Firemen (Land and Marine) who desire to obtain a United States Government or State License. Pocket-book form, gilt edge ?i.50 EDWARDS.— The American Steam Engineer: Theoretical and Practical, with examples of the latest and most approved American practice in the design and con- struction of Steam Engines and Boilers. For the use of HENRY CAREY BAIRD & CO.'S CATALOGUE ii Engineers, machinists, boiler-makers, and engineering stu- dents. By Emory Edwards. Fully illustrated. 419 pages. i2mo $1.50 EDWARDS.— The Practical Steam Engineer's Guide: In the Design, Construction, and Management of American Stationary, Portable, and Steam Fire-Engines, Steam Pumps, Boilers, Injectors, Governors, Indicators, Pistons and Rings, Safety Valves and Steam Gauges. For the use of Engineers, Firemen, and Steam Users. By Emory Edwards. Illus- trated by 119 engravings. 420 pages. i2mo $2.00 ELDER. — Conversations on the Principal Subjects of Political Economy: By Dr. William Elder. 8vo $1.50 ELDER.— Questions of the Day: Economic and Social. By Dr. William Elder. 8vo. $3.00 ERNI AND BROWN.— Mineralogy Simplified: Easy Methods of Identifying Minerals, including Ores, by Means of the Blow-pipe, by Flame Reactions, by Humid Chemical Analysis, and by Physical Tests. By Henri Erni, a. M., M. D. Fourth Edition, revised, re-arranged and with the addition of entirely new matter, including Tables for the Determination of Minerals by Chemicals and Pyrog- nostic Characters, and by Physical Characters. By Amos P. Brown, E. M., Ph. D. 464 pp. Illustrated by 123 En- gravings, pocket-book form, full flexible morocco, gilt edges. $2.50 FAIRBAIRN. — ^The Principles of Mechanism and Machi- nery of Transmission: Comprising the Principles of Mechanism, Wheels, and Pul- leys, Strength and Proportion of Shafts, Coupling of Shafts, and Engaging and Disengaging Gear. By Sir William Fairbairn, Bart., C. E. Beautifully illustrated by over 150 wood-cuts. In one volume, l2mo $2.00 FLEMING.— Narrow Gauge Railways in America: A Sketch of their Rise, Progress, and Success. Valuable Statistics as to Grades, Curves, Weight of Rail, Locomotives, Cars, etc. By Howard Fleming. Illustrated. 8vo. ..$1.00 FLEMMING.— Practical Tanning: A Handbook of Modern Processes, Receipts, and Sugges- tions for the Treatment of Hides, Skins, and Pelts of Every Description. By Lewis A. Flemming, American Tanner. 630 pp, 8vo. 1910 $6.00 FORSYTH.— Book of Designs for Headstones, Mural, and other Monuments: Containing 78 Designs. By James Forsyth, With an In- troduction by Charles Boutell, M. A. 4to. Cloth., .fo.oo 12 HENRY CAREY BAIRD & CO.'S CATALOGUE GARDNER.— Everybody's Paint Book: A Complete Guide to the Art of Outdoor and Indoor Paint- ing. . 38 illustrations. i2mo. 183 pp $1^00 GARDNER.— The Painter's Encyclopaedia: Containing Definitions of all Important Words in the Art of Plain and Artistic Painting, with Details of Practice in Coach, Carriage, Railway Car, House, Sign, and Ornamental Paint- ing, including Graining, Marbling, Staining, Varnishing, Polishing, Lettering, Stenciling, Gilding, Bronzing, etc. By Franklin B. Gardner. 158 illustrations. i2mo. 427 pp. $2.00 GEE.— The Goldsmith's Handbook: Containing full instructions for the Alloying and Working of Gold, including the Art of Alloying, Melting, Reducing, Color- ing, Collecting, and Refining ; the Processes of Manipulation, Re- covery of Waste; Chemical and Physical Properties of Gold; with a New System of Mixing its Alloys; Solders, Enamelsj and other Useful Rules and Recipes. By George E. Gee. l2mo $1.25 GEE. — ^The Jeweler's Assistant in the Art of Working in Gold: A Practical Treatise for Masters and Workmen. l2mo. $3.00 GEE.— The Silversmith's Handbook: Containing full instructions for the Alloying and Working of Silver, including the different modes of Refining and Melting the Metal; its Solders; the Preparation of Imitation Alloys; Methods of Manipulation; Prevention of Waste; Instructions for Improving and Finishing the Surface of the Work; together with other Useful Information and Memoranda. By George E. Gee. Illustrated. i2mo $1-25 GOTHIC ALBUM FOR CABINET-MAKERS: Designs for Gothic Furniture. Twenty-three plates. Ob- long $1.00 GRANT.— A Handbook on the Teeth of Gears: Their Curves, Properties, and Practical Construction. By George B. Grant. Illustrated. Third Edition, enlarged. 8vo Ii.oo GREGORY.— Mathematics for Practical Men: Adapted to the Pursuits of Surveyors, Architects, Mechan- ics, and Civil Engineers. By Olinthus Gregory. 8vo., plates $3.00 GRISWOLD.— Railroad Engineer's Pocket Companion for the Field: Comprising Rules for Calculating Deflection Distances and Angles, Tangential Distances and Angles and all Necessary Tables for Engineers; also the Art of Levelling from Prelim- HENRY CAREY BAIRD & CO.'S CATALOGUE 13 inary Survey to the Construction of Railroads, intended Expressly for the Young Engineer, together with Numerous Valuable Rules and Examples. By W. Griswold. lamo. pocketbook form .$1.50 GRUNER.— Studies of Blast Furnace Phenomena: By M. L. Gruner, President of the General Council of Mines of France, and lately Professor of Metallurgy at the Ecole defe Mines. Translated, with the author's sanction, with an Ap- pendix, by L. D. B. Gordon, F. R. S. E., F. G. S. 8vo. $2.50 Hand-Book of Useful Tables for the Lumberman, Farmer and Mechanic: Containing Accurate Tables of Logs Reduced to Inch Board Measure, Plank, Scantling and Timber Measure; Wages and Rent, by Week or Month; Capacity of Granaries, Bins and Cisterns; Land Measure, Interest Tables with Directions for finding the Interest on any sura at 4, 5, 6, 7 and 8 per cent., and many other Useful Tables. 32mo., boards. 186 pages. •25 HASERICK.— The Secrets of the Art of Dyeing Wool, Cotton and Linen: Including Bleaching and Coloring Wool and Cotton Hosiery and Random Yarns. A Treatise based on Economy and Practice. By E. C. Haserick. Illustrated by 323 Dyed Patterns of the Yarns or Fabrics. 8vo $4.50 HATS AND FELTING: A Practical Treatise on their Manufacture. By a Practical Hatter. Illustrated by Drawings of Machinery, etc. 8vo. 1 1. 00 HAUPT.— A Manual of Engineering Specifications and Contracts : By Lewis M. Haupt, C. E. Illustrated with numerous maps. 328 pp. 8vo I2.00 HAUPT. — Street Railway Motors: With Descriptions and Cost of Plants and Operation of the Various Systems now in Use. l2mo $1.50 HAUPT. — The Topographer, His Instruments and Meth- ods. By Lewis M. H.\upt, A. M., C. E. Illustrated with numer- ous plates, maps and engravings. 247 pp. 8vo $2.00 HULME.— Worked Examination Questions in Plane Geometrical Drawing: For the Use of Candidates for the Royal Military Academy, Woolwich; the Royal Military College, Sandhurst; the In- dian Civil Engineering College, Cooper's Hill; Indian Public Works and Telegraph Department; Royal Marine Light In- 14 HENRY CAREY BAIRD & CO.'S CATALOGUE fantry; the Oxford and Cambridge Local Examinations, etc. By F. Edward Hulme, F. L. S., F. S. A., Art-Master Marl- borough College. Illustrated by 300 examples. Small quarto f l.oo KELLEY. — Speeches, Addresses, and Letters on Industrial and Financial Questions: By Hon. William D. Kelley, M. C. 544 pages. 8vo. $2.00 KEMLO.— Watch-Repairer's Hand-Book: Being a Complete Guide to the Young Beginner, in Taking Apart, Putting Together, and Thoroughly Cleaning the English Lever and other Foreign Watches, and all American Watches. By F. Kelmo, Practical Watchmaker. With Il- lustrations. i2mo $1.25 KICK. — Flour Manufacture: A Treatise on Milling Science and Practice. By Frederick Kick, Imperial Regierungsrath, Professor of Mechanical Technology in the Imperial German Polytechnic Institute, Prague. Translated from the second enlarged and revised edition with supplement by H. H. P. Powles, Assoc. Memb. Institution of Civil Engineers. Illustrated with 28 Plates, and 167 Wood-cuts. 367 pages. 8vo $10.00 KINGZETT.— The History, Products, and Processes of the Alkali Trade: Including the most Recent Improvements. By Charles Thomas Kingzett, Consulting Chemist. With 23 illu.stra- tions. 8vo $2.00 KIRK. — A Practical Treatise on Foundry Irons: Comprising Pig Iron, and Fracture Grading of Pig and Scrap Irons; Scrap Irons; Mixing Irons; Elements and Metalloids: Grading Iron by Analysis; Chemical Standards for Iron Castings; Testing Cast Iron; Serai-Steel; Malleable Iron; Etc., Etc. By Edward Kirk, Practical Moulder and Melter, Consulting Expert in Melting. Illustrated. 294 pages. 8vo. 1911 I3.00 KIRK.— The Cupola Furnace: A Practical Treatise on the Construction and Management of Foundry Cupolas. By Edward Kirk, Practical Moulder and Melter, Consulting Expert in Melting. Illustrated by 106 engravings. Third Edition, revised and enlarged. 482 pages. 8vo. 1910 $3.50 KOENIG.— Chemistry Simplified: A Course of Lectures on the Non-Metals, Based upon the Natural Evolution of Chemistry. Designed Primarily for Engineers. By George Augustus Koenig, Ph. D., A. M., E. M., Professor of Chemistry, Michigan College of Mines, Houghton. Illustrated by 103 Original Drawings. 449 pp. i2mo. (1906) J2.25 HENRY CAREY BAIRD & CO.'S CATALOGUE 15 LANGBEIN.— A Complete Treatise on the Electro-Deposi- tion of Metals: Comprising Electro-Plating and Galvanoplastic Operations, the Deposition of Metals by the Contact and Immersion Pro- cesses, the Coloring of Metals, the Methods of Grinding and Polishing, as well as the Description of the Voltaic Cells, Dynamo-Electric Machines, Thermopiles, and of the Materi- als and Processes Used in Every Department of the Art. Translated from the Fifth German Edition of Di^ George Langbein, Proprietor of a Manufactory for Chemical Pro- ducts, Machines, Apparatus and Utensils for Electro-Platers, and of an Electro-Plating Establishment in Leipzig. With Additions by William T. Brannt, Editor of "The Techno- Chemical Receipt Book." Sixth Edition, Revised and En- larged. Illustrated by 163 Engravings. 8vo. 725 pages. (1909) fc-oo LARKIN.— The Practical Brass and Iron Founder's Guide: A Concise Treatise on Brass Founding, Moulding, the Metals and their Alloys, etc.; to which are added Recent Improve- ments in the Manufacture of Iron, Steel by the Bessemer Process, etc., etc. By James Larkin, late Conductor of the Brass Foundry Department in Reany, Neafie & Co.'s Penn Works, Philadelphia. New edition, revised, with extensive additions. 414 pages. i2mo S2.50 LEHNER.— The Manufacture of Ink: Comprising the Raw Materials, and the Preparation of Writing, Copying and Hektograph Inks, Safety Inks, Ink Extracts and Powders, etc. Translated from the German of SiGMUND Lehner, with additions by William T. Brannt. Illustrated. i2mo $2.00 LEROUX. — A Practical Treatise on the Manufacture of Worsteds and Carded Yarns: Comprising Practical Mechanics, with Rules and Calcula- tions applied to Spinning; Sorting, Cleaning, and Scouring Wools; the English and French Methods of Combing, Draw- ing, and Spinning Worsteds, and Manufacturing Carded Yarns. Translated from the French of Charles Leroux, Mechanical Engineer and Superintendent of a Spinning-Mill, by Horatio Paine, M. D., and A. A. Fesquet, Chemist and Engineer. Illustrated by twelve large Plates. 8vo $3.00 LESLIE.— Complete Cookery: Directions for Cookery in its Various Branches. By Miss Leslie. Sixtieth thousand. Thoroughly revised, with the additions of New Receipts. i2mo $1.00 LE VAN.— The Steam Engine and the Indicator: Their Origin and Progressive Development; including the Most Recent Examples of Steam and Gas Motors, together i6 HENRY CAREY BAIRD & CO.'S CATALOGUE with the Indicator, its Principles, its Utility, and its Applica- tion. By William Barnet Le Van. Illustrated by 205 Engravings, chiefly of Indicator-Cards. 469 pp. 8vo. J2.00 LIEBER.— Assayer's Guide: Or, Practical Directions to Assayers, Miners, and Smelters, for the Tests and Assays, by Heat and by Wet Processes, for the Ores of all the principal Metals, of Gold and Silver Coins and alloys, and of Coal, etc. By Oscar M. Lieber. Re- vised. 283 pp. i2mo. r jSi-So Lockwood's Dictionary of Terms: Used in the Practice of Mechanical Engineering, embracing those Current in the Drawing Office, Pattern Shop, Foundry, Fitting, Turning, Smith's and Boiler Shops, etc., etc., com- prising upwards of Six Thousand Definitions. Edited by a Foreman Pattern Maker, author of "Pattern Making." 417 PP- i2mo $3.75 LUKIN.— The Lathe and Its Uses: Or Instruction in the Art of Turning Wood and Metal. In- cluding a Description of the Most Modern Appliances for the Ornamentation of Plane and Curved Surfaces, an Entirely Novel Form of Lathe for Eccentric and Rose-Engine Turning; A Lathe and Planing Machine Combined; and Other Valu- able Matter Relating to the Art. Illustrated by 462 engrav- ings. ' Seventh edition. 315 pages. 8vo 14-25 MAUCHLINE.— The Mine Foreman's Hand-Book: Of Practical and Theoretical Information on the Opening, Ventilating, and Working of Collieries. Questions and An- swers on Practical and Theoretical Coal Mining. Designed to Assist Students and Others in Passing Examinations for Mine Foremanships. By Robert Mauchline.. 3d Edi- tion. Thoroughly Revised and Enlarged by F. Ernest Brackett. 134 engravings. 8vo. 378 pages. (1905.) fe.75 MOLESWORTH.— Pocket-Bpok of Useful Formulae and Memoranda for Civil and Mechanical Engineers. By Guilford L. Molesworth, Member of the Institution of Civil Engineers, Chief Resident Engineer of the Ceylon Railway. Full-bound in Pocketbook form $1.00 MOORE. — The Universal Assistant and the Complete Mechanic: Containing over one million Industrial Facts, Calculatiofis, Receipts, Processes, Trades Secrets, Rules, Business Forms, Legal Items, etc., in every occupation, from the Household to the Manufactory. By R. Moore. Illustrated by 500 Engravings. i2mo $2. go HENRY CAREY BAIRD & CO.'S CATALOGUE 17 NAPIER.— A System of Chemistry Applied to Dyeing: By James Napier, F. C. S. A New and Thoroughly Revised Edition. Completely brought up to the present state of the Science, including the Chemistry of Coal Tar Colors, by A. A. Fesquet, Chemist and Engineer. With an Appendix on Dyeing and Calico Printing, as shown at the Universal Ex- position, Paris, 1867. Illustrated. 8vo. 422 pages. . .$2.00 NICHOLLS.— The Theoretical and Practical Boiler-Maker and Engineer's Reference Book: Containing a variety of Useful Iriformation for Employers of Labor, Foremen and Working Boiler-Makers, Iron, Copper, and Tinsmiths, Draughtsmen, Engineers, the Gen- eral Steam-using Public, and for the Use of Science Schools and classes. By Samuel Nicholls. Illustrated by sixteen plates. i2mo ,. . .$2.50 NICHOLSON.— A Manual of the Art of Bookbinding: Containing full instructions in the different Branches of For- warding, Gilding, and Finishing. Also, the Art of MarbUng Book-edges and Paper. By James B. Nichollson. Il- lustrated. i2mo., cloth $2.25 NYSTROM.— On Technological Education and the Con- struction of Ships and Screw Propellers : For Naval and Marine Engineers. By John W. Nystrom, late Acting Chief Engineer, U. S. N. Second edition, revised, with additional matter. Illustrated by seven engravings. i2mo jfi.oo O'NEILL.— A Dictionary of Dyeing and Calico Printing: Containing a brief account of all the Substances and Processes in use in the Art of Dyeing and Printing Textile Fabrics; with Practical Receipts and Scientific Information. By Charles CNeh-l, Analytical Chemist. To which is added an Essay on Coal Tar Colors and their application to Dyeing and Calico Printing. By A. A. Fesquet, Chernist and En- gineer. With an appendix on Dyeing and Calico Printing, as shown at the Universal Exposition, Paris, 1867. 8vo. 491 pages $2.00 ORTON.— Underground Treasures: How and Where to Find Them. A Key for the Ready De- termination of all the Useful Minerals within the United States. By James Orton, A. M., Late Professor of Natural History in Vassar College, N. Y.; author of the "Andes and the Amazon," etc. A New Edition, with An Appendix on Ore Deposits and Testing Minerals. (1901.) Illustrated. OSBORN.— A Practical Manual of Minerals, Mines and Mining: ^ , . „ • • Comprising the Physical Properties, Geologic Position; Local Occurrence and Associations of the Useful Minerals, i8 HENRY CAREY BAIRD & CO.'S CATALOGUE their Methods of Chemical Analysis and Assay; together with Various Systems of Excavating and Timbermg, Brick and Masonry Work, during Driving, Lining, Bracing and other Operations, etc. By Prof. H. S. Osborn LL. D., Author of "The Prospector's Field-Book and Guide. 171 engravings. Second Edition, revised. 8vo ?4-50 OSBORN.— The Prospector's Field Book and Guide: In the Search For and the Easy Determination of Ores and Other Useful Minerals. By Prof. H. S. Osborn, LL. D. Illustrated by 66 Engravings. Eighth Edition. Revised and Enlarged. 401 pages. i2mo. (1910-) *l-50 OVERMAN.— The Moulder's atid Founder's Pocket Guide: A Treatise on Moulding and Founding in Green-sand, Dry- sand, Loam, and Cement; the Moulding of Machine Frames, Mill-gear, Hollow Ware, Ornaments, Trinkets, Bells, and Statues; Description of Moulds for Iron, Bronze, Brass, and other Metals; Plaster of Paris, Sulphur, Wax, etc.; the Con- struction of Melting Furnaces, the Melting and Founding of Metals; the Composition of Alloys and their Nature, etc., etc. By Frederick Overman, M. E. A new Edition, to which is added a Supplement on Statuary and Ornamental Moulding, Ordnance, Malleable Iron Castings, etc. By A. A. Fesquet, Chemist and Engineer. Illustrated by 44 engravings. i2mo. $2.00 PAINTER, GILDER, AND VARNISHER'S COMPANION: Comprising the Manufacture and Test of Pigments, the Arts of Painting, Graining, Marbling, Staining, Sign-writing, Varnishing, Glass-staining, and Gilding on Glass; -together with Coach Painting and Varnishing, and the Principles of the Harmony and Contrast of Colors. Twenty-seventh Edition. Revised, Enlarged, and in great part Rewritten. By William T. Brannt, Editor of "Varnishes, Lacquers, Printing Inks and Sealing Waxes. " Illustrated. 395 pp. l2mo $1-50 PERCY.— The Manufacturing of Russian Sheet-Iron: By John Percy, M. D., F. R. S. Paper 25 POSSELT.— Cotton Manufacturing: Part I. Dealing with the Fibre, Ginning, Mixing, Picking, Scutching and Carding. By E. A. Posselt. 104 illustra- tions, 190 pp $3.00 Part 11. Combing, Drawing, Roller Covering and Fly Frame, $3.00 POSSELT.— The Jacquard Machine Analysed and Ex- plained : With an Appendix on the Preparation of Jacquard Cards, and Practical Hints to Learners of Jacquard Designing. By E. A. HENRY CAREY B AIRD & CO.'S CATALOGUE 19 PossELT. With 230 illustrations and numerous diagrams. 127 pp. 4to $3.00 POSSELT. — Recent Improvements in Textile Machinery Relating to Weaving: Giving the Most Modern Points on the Construction of all Kinds of Looms, Warpers, Beamers, Slashers, Winders, Spoolers, Reeds, Temples, Shuttles, Bobbins, Heddles, Heddle Frames, Pickers, Jacquards, Card Stampers, Etc., Etc. By E. A. PossELT. 4to. Part I, 600 ills.; Part 11, 600 ills. Each part $3.00 POSSELT. — Recent Improvements in Textile Machinery, Part III: Processes Required for Converting Wool, Cotton, Silk, from Fibre to Finished Fabric, Covering both Woven and Knit Goods; Construction of the most Modern Improvements in Preparatory Machinery, Carding, Combing, Drawing, and Spinning Machinery, Winding, Warping, Slashing Machinery, Looms, Machinery for Knit Goods, Dye Stuffs, Chemicals, Soaps, Latest Improved Accessories Relating to Construc- tion and Equipment of Modern Textile Manufacturing Plants. By E. A. PossELT. Completely Illustrated. 4to $7.50 POSSELT.— Technology of Textile Design: The Most Complete Treatise on the Construction and Appli- cation of Weaves for all Textile Fabrics and the Analysis of Cloth. By E. A. PossELT. 1,500 illustrations. 4to fo.oo POSSELT.— Textile Calculations: A Guide to Calculations Relating to the Manufacture of all Kinds of Yarns and Fabrics, the Analysis of Cloth, Speed, Power and Belt Calculations. By E. A. Posselt. Illus- trated. 4to ' $2.00 REGNAULT.— Elements of Chemistry: By M. V. Regnault. Translated from the French by T. Forrest Betton, M.D., and edited, with Notes, by James C. Booth, Melter and Refiner U. S. Mint, and William L. Faber, Metallurgist and Mining Engineer. Illustrated by nearly 700 wood-engravings. Comprising nearly 1 ,500 pages. In two volumes, 8vo., cloth $5-00 RICH.— Artistic Horse-Shoeing: A Practical and Scientific Treatise, giving Improved Methods of Shoeing, with Special Directions for Shaping Shoes to Cure Different Diseases of the Foot, and for the Correction of Faulty Action in Trotters. By George E. Rich. 362 Illus- trations. 217 pages. i2mo $2.00 RICHARDS.— Aluminium : Its History, Occurrence, Properties, Metallurgy and Applica- tions including its Alloys. By Joseph W. Richards, A. C, 20 HENRY CAREY BAIRD & CO.'S CATALOGUE Chemist and Practical Metallurgist, Member of the Deutsche Chemische Gesellschaft. lUust. Third edition, enlarged and revised (1895) $6.00 RICHARDSON.— Practical Blacksmithing : A Collection of Articles Contributed at Different Times by Skilled Workmen to the columns of "The Blacksmith and Wheelwright," and Covering nearly the Whole Range of Blacksmithing, from the Simplest Job of Work to some of the most Complex Forgings. Compiled and Edited by M. T. Richardson. Vol. I. 210 Illustrations. 224 pages. l2mo $1.00 Vol. II. 230 Illustrations. 262 pages. l2mo $l.oo Vol. III. 390 Illustrations. 307 pages. i2mo jSi.oo Vol. IV. 226 Illustrations. 276 pages. i2mo ji.oo RICHARDSON.— Practical Carriage Building: Comprising Numerous Short Practical Articles upon Carriage and Wagon Woodwork; Plans for Factories; Shop and Bench Tools; Convenient Appliances for Repair Work; Methods of Working; Peculiarities of Bent Timber; Construction of Carriage Parts; Repairing Wheels; Forms of Tenons and Mor- tises; Together with a Variety of Useful Hints and Sugges- tions to Woodworkers. Compiled by M. T. Richardson. Vol. I. 228 Illustrations. 222 pages $1.00 Vol. II. 283 Illustrations. 280 pages $l.oo RICHARDSON.— The Practical Horseshoer: Being a Collection of Articles on ' Horseshoeing in all its Branches which have appeared from time to time in the col- umns of "The Blacksmith and Wheelwright," etc. Com- piled and edited by M. T. Richardson. 174. Illustrations, jfi.oo RIFFAULT, VERGNAUD, and TOUSSAINT.— A Practical Treatise on the Manufacture of Colors for Painting: Comprising the Origin, Definition, and Classification of Colors, the Treatment of the Raw Materials; the best Formulae and the Newest Processes for the Preparation of every description of Pigment, and the Necessary Apparatus and Directions for its use; Dryers; the Testing, Application, and Qualities of Paints, etc., etc. By MM. Riffault, Vergnaud, and ToussANT. Revised and Edited by M. F. Malpeyre. Translated from the French by A. A. Fesquet. Illustrated by Eighty Engravings. 659 pp. 8 vo $5.00- ROPER. — Catechism for Steam Engineers and Elec- tricians: Including the Construction and Management of Steam En- gines, Steam Boilers and Electric Plants. By Stephen Roper. Twenty-first edition, rewritten and greatly enlarged by E. R. Keller and C. W. Pike. 365 pages. Illustrations. l8mo., tucks, gilt $2.00 HENRY CAREY BAIRD & CO.'S CATALOGUE 21 ROPER.— Engineer's Handy Book: Containing Facts, Formulae, Tables and Questions on Power, its Generation, Transmission and Measurement; Heat, Fuel, and Steam; The Steam Boiler and Accessories; Steam Engines and their Parts; Steam Engine Indicator; Gas and Gasoline Engines; Materials; their Properties and Strength; Together with a Discussion of the Fundamental Experiments in Elec- tricity, and an Explanation of Dynamos, Motors, Batteries, etc., and Rules for Calculating Sizes of Wires. By Stephen Roper. 15th edition. Revised and enlarged by E. R. Keller, M. E., and C. W. Pike, B. S. With numerous illustrations. Pocket-book form. Leather $3-50 ROPER. — Hand-Book of Land and Marine Engines: Including the Modeling, Construction, Running, and Manage- ment of Land and Marine Engines and Boilers. With illu- strations. By Stephen Roper, Engineer. Sixth edition. i2mo., tucks, gilt edge $3-5o ROPER.— Hand-Book of the Locomotive: Including the Construction of Engines and Boilers, and the Construction, Management, and Running of Locomotives. By Stephen Roper. Eleventh edition. i8mo., tucks, gilt edge $2.50, ROPER. — Hand-Book of Modern Steam Fire-Engines: With illustrations. By Stephen Roper, Engineer. Fourth edition, i2mo., tucks, gilt edge fe.50 ROPER.— Instructions and Suggestions for Engineers and Firemen : By Stephen Roper, Engineer. i8mo., Morocco $2.00 ROPER. — Questions and Answers for Stationary and Marine Engineers and Electricians: With a Chapter of What to Do in Case of Accidents. By Stephen Roper, Engineer. Sixth edition. Rewritten and Greatly fenlarged by Edwin R. Keller, M. E., and Clayton W. Pike, B. A. 306 pp. Morocco, pocketbook form, gilt edges $^-0o ROPER.— The Steam Boiler: Its Care and Management: By Stephen Roper, Engineer. i2mo.,tuck, gilt edges. $2.00 ROPER. — Use and Abuse of the Steam Boiler: By Stephen Roper, Engineer. Ninth Edition, with illus- trations. i8mo., tucks, gilt edge $2.00 , ROPER.— The Young Engineer's Own Book: Containing an Explanation of the Principle and Theories on which the Steam Engine as a Prime Mover is based. By Stephen Roper, Engineer. 160 Illustrations,' 363 pages. i8mo., tuck • $2.50 22 HENRY CAREY BAIRD & CO.'S CATALOGUE ROSE.— The Complete Practical Machinist: Embracing Lathe Work, Vise Work, Drills and Drilling, Taps and Dies, Hardening and Tempering, the Making and Use of Tools, Tool Grinding, Marking out work. Machine Tools, etc. By Joshua Rose. 395 Engravings. Nineteenth Edition, greatly Enlarged with New and Valuable Matter. i2mo., 504 pages I2.50 ROSE.— Mechanical Drawing Self-Taught: Comprising Instructions in the Selection and Preparation of Drawing Instruments, Elementary Instruction in practical Mechanical Drawing, together with Examples in Simple Geometry and Elementary Mechanism, including Screw Threads, Gear Wheels, Mechanical Motions, Engines and Boilers. By Joshua Rose, M. E. Illustrated by 330 en- gravings. 8vo. 313 pages $3.50 ROSE.— The Slide- Valve Practically Explained: Embracing simple and complete Practical Demonstrations of the operation of each element in a Slide-valve Movement, and illustrating the effects of Variations in their Proportions by examples carefully selected from the most recent and successful practice. By Joshua Rose, M. E. Illustrated by 35 engravings jSl.oo ROSE.— Steam Boilers: A Practical Treatise on Boiler Construction and Examination, for the Use of Practical Boiler Makers, Boiler Users, and In- spectors; and embracing in plain figures all the calculations necessary in Designing or Classifying Steam Boilers. By Joshua Rose, M. E. Illustrated by 73 engravings. 250 pages. 8vo $2.00 ROSS. — The Blowpipe in Chemistry, Mineralogy and Geology: Containing all Known Methods of Anhydrous Analysis, many Working Examples, and Instructions for Making Apparatus. By Lieut. Colonel W. A. Ross, R. A., F. G. S. With 120 Illustrations. l2mo $2.00 SCHRIBER.— The Complete Carriage and Wagon Painter: A Concise Compendiun of the Art of Painting Carriages, Wagons, and Sleighs, embracing Full Directions in all the Various Branches, including Lettering, Scrolling, Ornamenting, Striping, Varnishing, and Coloring, with numerous Recipes for Mixing Colors. 73 illustrations. 177 pp. l2mo. ..$1.00 SHAW.— Civil Architecture: Being a Complete Theoretical and Practical System of Build- ng, containing the Fundamental Principles of the Art. By Edward Shaw, Architect. To which is added a Treatise on HENRY CAREY BAIRD & CO.'S CATALOGUE 23 Gothic Architecture, etc. By Thomas W. Silloway and George M. Harding, Architects. The whole illustrated bj' 102 quarto plates finely engraved on copper. Eleventh edi- tion. 4to §5.00 SHERRATT.— The Elements of Hand-Railing: Simplified and Explained in Concise Problems that are Easily Understood. The whole illustrated with Thirty-eight Ac- curate and Original Plates, Founded on Geometrical Principles, and showing how to Make Rail Without Centre Joints, Making Better Rail of the Same Material, with Half the Labor, and Showing How to Lay Out Stairs of all Kinds. By R. J. Sherratt. Folio $2.50 SHUNK.^ — A Practical Treatise on Railway Curves and Location, for Young Engineers: By W. F. Shunk, C. E. l2mo. Full bound pocket-book form ?2.oo SLOANE. — Home Experiments in Science: By T. O'CONOR Sloane, E. M., A. M., Ph.D. Illustrated by gi engravings. i2mo Si.oo SLOAN. — Homestead Architecture: Containing Forty Designs for Villas, Cottages, and Farm- houses, with Essays on Style, Construction, Landscape Gar- dening, Furniture, etc., etc. Illustrated by upwards of 200 engravings. By Samuel Sloan, Architect. 8vo $2.00 SMITH.— The Dyer's Instructor: Comprising Practical Instructions in the Art of Dyeing Silk, Cotton, Wool, and Worsted, and Woolen Goods; containing nearly 800 Receipts. To which is added a Treatise on the Art of Padding; and the Printing of Silk Warps, Skeins, and Handkerchiefs, and the various Mordants and Colors for the different styles of such work. By David Smith, Pattern Dyer. i2mo. $1.00 SMITH. — A Manual of Political Economy: By E. Peshine Smith. A New Edition, to which is added a full Index. l2mo $1.25 SMITH. — Parks and Pleasure-Grounds: Or Practical Notes on Country Residences, Villas, Public Parks, and Gardens. By Chari.es H. J. Smith, Landscape Gardener and Garden Architect, etc., etc. l2mo $2.00 SNIVELY.— The Elements of Systematic Qualitative Chemical Analysis: A Hand-book for Beginners. By John H. Snively, Phr. D. l6mo $2.00 24 HENRY CAREY BAIRD & CO.'S CATALOGUE STOKES.— The Cabinet Maker and Upholsterer's Com- panion : Comprising the Art of Drawing, as applicable to Cabinet Work; Veneering, Inlaying, and Buhl- Work; the Art of Dye- ing and Staining Wood, Ivory, Bone, Tortoise-Shell, etc. Directions for Lacquering, Japanning, and Varnishing; to make French Polish, Glues, Cements, and Compositions; with numerous Receipts, useful to workmen generally. By J. Stokes. Illustrated. A New Edition, with an Appendix upon French Polishing, Staining, Imitating, Varnishing, etc., etc. l2rao jfl.zs STRENGTH AND OTHER PROPERTIES OF METALS: Reports of Experiments on the Strength and other Properties of Metals for Cannon. With a Description of the Machines for Testing Metals, and of the Classification of Cannon in service. By Officers of the Ordnance Department, U. S. Army. By authority of the Secretary of War. Illustrated by 25 large steel plates. Quarto fe.oo SULZ. — A Treatise on Beverages: Or the Complete Practical Bottler. Full Instructions for Laboratory Work with Original Practical Recipes for all kinds of Carbonated Drinks, Mineral Waters, Flavoring Extracts, Syrups, etc. By Charles Herman Sulz, Technical Chemist and Practical Bottler. Illustrated by 428 Engrav- ings. 818 pp. 8vo I7.50 SYME.^Outlines of an Industrial Science: By David Syme. i2mo JS2.00 TABLES SHOWING THE WEIGHT OF ROUND, SQUARE AND FLAT BAR IRON, STEEL, ETC. By Measurement. Cloth 63 TEMPLETON.— The Practical Examinator on Steam and the Steam-Engine. With Instructive References relative thereto, arranged for the Use of Engineers, Students, and others. By William Templeton, Engineer. i2mo $1.00 THALLNER.— Tool-Steel : A Concise Hand-book on Tool-Steel in General. Its Treat- ment in the Operations of Forging, Annealing, Hardening, Tempering, etc., and the Appliances Therefor. By Otto Thallner, Manager in Chief of the Tool-Steel Works, Bis- marckhiitte, Germany. From the German by William T. Brannt. Illustrated by 69 engravings. 194 pages. 8vo. 1902 $2.00 THAUSING.— The Theory and Practice of the Preparation of Malt and the Fabrication of Beer: With especial reference to the Vienna Process of Brewing. HENRY CAREY BAIRD & CO.'S CATALOGUE 25 Elaborated from personal experience by Julius E. Thausing, Professor at the School for Brewers, and at the Agricultural Institute, Modling, near Vienna. Translated from the Ger- man by William T. Brannt. Thoroughly and elaborately edited, with much American matter, and according to the latest and most Scientific Practice, by A. Schwarz and Dr. A. H. Bauer. Illustrated by 140 Engravings. 8vo. 815 pages $10.00 TOMPKINS.— Cotton and Cotton Oil: Cotton: Planting, Cultivating, Harvesting and Preparation for Market. Cotton Seed Oil Mills: Organization, Construc- tion and Operation. Cattle Feeding: Production of Beef and Dairy Products, Cotton Seed Meal and Hulls as Stock Feed. Fertilizers: Manufacture, Manipulation and Uses. By D. A. Tompkins. 8vo. 494 pp. Illustrated I7.50 TOMPKINS.— Cotton Mill, Commercial Features: A Text-Book for the Use of Textile Schools and Investors. With Tables showing Cost of Machinery and Equipments for Mills making Cotton Yarns and Plain Cotton Cloths. By D. A. Tompkins. 8vo. 240 pp. Illustrated fS-oo. TOMPKINS.— Cotton Mill Processes and Calculations: An Elementary Text-Book for the Use of Textile Schools and for Home Study. By D. A. Tompkins. 312 pp. 8vo. Illustrated $5.00 TURNER'S (THE) COMPANION: Containing Instructions in Concentric, Elliptic, and Eccen- tric Turning; also various Plates of Chucks, Tools, and In- struments; and Directions for using the Eccentric Cutter, Drill, Vertical Cutter, and Circular Rest; with Patterns and Instructions for working them. l2mo $1.00 VAN CLEVE.— The English and American Mechanic: Comprising a Collection of Over Three Thousand Receipts, Rules, and Tables, designed for the Use of every Mechanic and Manufacturer. By B. Frank Van Cleve. Illustrated. 500 pp. l2mo $2.00 VAN DER BURG.— School of Painting for the Imitation of Woods and Marbles: A Complete, Practical Treatise on the Art and Craft of Grain- ing and Marbling with the Tools and Appliances. 36 plates. Folio, 12x20 inches $6.00. VILLE. — ^The School of Chemical Manures: Or, Elementary Principles in the Use of Fertilizing Agents. From the French of M. Geo. Ville, by A. A. Fesquet, Chemist and Engineer. With Illustrations. i2mo. ...$1.25 26 HENRY CAREY BAIRD & CO.'S CATALOGUE VOGDES.— The Architect's and Builder's Pocket-Com- panion and Price- Book: Consisting of a Short but Comprehensive Epitome of Deci- mals, Duodecimals, Geometry and Mensuration; with Tables of United States Measures, Sizes, Weights, Strengths, etc., of Iron, Wood, Stone, Brick, Cement and Concretes, Quanti- ties of Materials in given Sizes and Dimensions of Wood, Brick and Stone; and full and complete Bills of Prices for Carpenter's Work and Painting; also, Rules for Computing and Valuing Brick and Brick Work, Stone Work, Painting, Plastering, with a Vocabulary of Technical Terms, etc. By Frank W. Vogdes, Architect, Indianapolis, Ind. Enlarged, revised, and corrected. In one volume, 368 pages, full-bound, pocketbook form, gilt edges $2.00 Cloth $1.50 WAHNSCHAFFE.— A Guide to the Scientific Examina- tion of Soils: Comprising Select Methods of Mechanical and Chemical Analysis and Physical Investigation. Translated from the German of Dr. F. Wahnschaffe. With additions by Wil- liam T. Brannt. Illustrated by 25 engravings. i2mo. 177 pages $1.50 WARE.— The Sugar Beet: Including a History of the Beet Sugar Industry in Europe, Varieties of the Sugar Beet, Examination, Soils, Tillage, Seeds and Sowing, Yield and Cost of Cultivation, Harvesting, Transportation, Conservation, Feeding Qualities of the Beet and of the Pulp, etc. By Lewis S. Ware, C. E., M. E. Illustrated by ninety engravings. 8vo $2.00 WARN.— The Sheet-Metal Worker's Instructor: For Zinc, Sheet-Iron, Copper, and Tin-Plate Workers, etc. Containing a selection of Geometrical Problems; also, Prac- tical and Simple Rules for Describing the various Patterns required in the different branches of the above Trades. By Reuben H. Warn, Practical Tin-Plate Worker. To which is added an Appendix, containing Instructions for Boiler-Mak- ing, Mensuration of Surfaces and Solids, Rules for Cal- culating the Weights of different Figures of Iron and Steel, Tables of the Weights of Iron, Steel, etc. Illustrated by thirty-two Plates and thirty-seven Wood Engravings. 8vo. $2.00 WARNER. — New Theorems, Tables, and Diagrams, for the Computation of Earth- work: Designed for the use of Engineers in Preliminary and Final Estimates, of Students in Engineering and of Contractors and other non-professional Computers. In two parts, with an Appendix. Part I. A Practical Treatise; Part II. A HENRY CAREY BAIRD & CO.'S CATALOGUE 27 Theoretical Treatise, and the Appendix Containing Notes to the Rules and Examples of Part I.; Explanations of the Con- struction of Scales, Tables, and Diagrams, and a Treatise upon Equivalent Square Bases and Equivalent Level Heights. By John Warner, A. M., Mining and Mechanical Engineer. Illustrated by 14 Plates. 8vo $3.00 WATSON.— A Manual of the Hand-Lathe: Comprising Concise Directions for Working Metals of all kinds. Ivory, Bone, and Precious Woods; Dyeing, Coloring, and French Polishing; Inlaying by Veneers, and various methods practised to produce Elaborate work with dispatch, and at Small Expense. By Egbert P. Watson, Author of "The Modern Practice of American Machinists and En- gineers." Illustrated by 78 engravings §1.00 WATSON. — ^The Modern Practice of American Machinists and Engineers: Including the Construction, Application, and Use of Drills, Lathe Tools, Cutters for Boring Cylinders, and Hollow-work generally, with the most economical Speed for the same; the Results verified by Actual Practice at the Lathe, the Vise, and on the floor. Together with Workshop Management, Economy of Manufacture, the Steam Engine, Boilers, Gears, Belting, etc., etc. By Egbert P. Watson. Illustrated by eighty-six engravings. i2mo $2.00 WEATHERLY.— Treatise on the Art of Boiling Sugar, Crystallizing, Lozenge-making, Comfits, Gum Goods: And other processes for Confectionery, including Methods for Manufacturing every Description of Raw and Refined Sugar Goods. A New and Enlarged Edition, with an Appen- dix on Cocoa, Chocolate, Chocolate Confections, etc. 196 pages. i2mo. (1903-) ?i-50 WILL. — Tables of Qualitative Chemical Analysis: With an Introductory Chapter on the Course of Analysis. By Professor Heinrich Will, of Giessen, Germany. Third American, from the eleventh German edition. Edited by Charles F. Himes, Ph. D., Professor of Natural Science, Dickinson College, Carlisle, Pa. 8vo $1.00 WILLIAMS.— On Heat and Steam: Embracing New- Views of Vaporization, Condensation and Explosion. By Charles Wye Williams, A. I. C. E. Illus- trated. Bvo J?2.00 WILSON.— The Practical Tool-Maker and Designer: A Treatise upon the Designing of Tools and Fixtures for Machine Tools and Metal Working Machinery, Comprising Modern Examples of Machines with Fundamental Designs 28 HENRY CAREY BAIRD & CO.S CATALOGUE for Tools for the Actual Production of the work; Together with Special Reference to a Set of Tools for Machining the Various Parts of a Bicycle. Illustrated by 189 engravings (1898.) JS2.50 CONTENTS: Introductory. Chapter I. Modern Tool Room and Equipment. II. Files, Their Use and Abuse. III. Steel and Tempering. IV. Making Jigs. V. Milling Machine Fixtures. VI. Tools and Fixtures for Screw Machines. VII. Broaching. VIII. Punches and Dies for Cut- ting and Drop Press. IX. Tools for Hollow- Ware. X. Embossing: Metal. Coin, and Stamped Sheet-Metal Ornaments. XI. Drop Forging. XII. Solid Drawn Shells or Ferrules; Cupping or Cutting, and Drawing; Break- ing Down Shells. XIII. Annealing, Pickling, and Cleaning. XIV. Tools for Draw Bench. XV. Cutting and Assembling Pieces by Means of Rat- chet Dial Plates at One Operation. XVI. The Header. XVII. Tools for Fox Lathe. XVIII. Suggestions for a set of Tools for Machining the Various Parts of a Bicycle. XIX. The Plater's Dynamo. XX. Conclu- sion — With a Few Random Ideas. Appendix. Index. BRANNT'S "SOAP MAKER'S HAND BOOK." The most helpful and up-to-date book on the Art of Soap Making in the English language. In one volume, 8vo, B35 pages, illustrated by 54: engravings. Price $6,00 net. Free of Postage to any Address in the World, or by Express C. O. D. freight paid to any Address in the United States or Canada. PUBLISHED APRIL, 1912. THE SOAP MAKER'S HAID BOOK OF MATERIALS, PROCESSES AND RECEIPTS FOR EVERY DESCRIPTION OF SOAP ijroLnDiNo PATS, PAT OILS, AND PATTY ACIDS ; EXAMINATION OP PATS AND OILS ; ALKALIES ; TESTING SODA AND POTASH ; MACHINES AND UTENSILS ; HARD SOAPS ; SOPT SOAPS ; TEXTILE SOAPS ; WASHING POWDERS AND ALLIED PEODUOTS ; TOILET SOAPS, MEDICATED SOAPS, AND SOAP SPECIALTIES ; ESSENTIAL OILS AND OTHER PERFUMING MATERIALS ; TESTING SOAPS. EDITED CHIEFLY FROM THE GERMAN OF DR. C. DEITE, A. ENGELHARDT, F. WILTNER, AND NUMEROUS OTHER EXPERTS. WITH ADDITIONS BY WILLIAM T. BRANNT, EDITOK OP "THK TECHNO CHEMICAL EEOEIPT BOOK." (LLUSTRATED BY FIPTT-FOUR ENGFIA.VINGS. SECOND EDITION. REVISED AND IN GREAT PART RE-WRITTEN. PHILADELPHIA : HENRY CAREY BAIRD & CO., INDUSTRIAL PUBLISHEES, BOOKSELLERS AND IMPORTERS, 810 Walnut Street. 1911 KIRK'S CUPOLA FURNACE. An Eminently, Practical, Up-to-Date Booh, by an Expert. Third Thoroughly Revised and Partly Re-written Edition. In one volume, 8vo,, 4:82 pages, illustrated by one hundred and six engravings. Price $8.30. Free of Postage to any Address in the World, or by Express C. O. D., freight paid to any Address in the United States or Canada. PUBLISHED AUGUST, 1910. THE CUPOLA FURNACE A PRACTICAL TREATISE ON THE CONSTRUCTION AND MANAGEMENT OF FOUNDRY CUPOLAS: COMPRISING IMPROVEMENTS IN CUPOLAS AND METHODS OF THEIR CONSTRUCTION AND MANAGE- MENT; TUYERES; MODERN CUPOLAS; CUPOLA FUELS; FLUXING OF IRON; GETTING UP CUPOLA STOCK; RUNNING A CONTINUOUS STREAM; SCIENTIFICALLY DESIGNED CUPOLAS; SPARK-CATCIIING DEVICES; BLAST-PIPES AND BLAST; BLOWERS; FOUNDRY TRAM RAIL, ETC, ETC. BY EDWARD KIRK, PRACTICAL MOULDER AND MELTER, CONSULTING EXPERT IN MELTING. Author of " The Founding of Meials^^ and o/Kumero2tc Papers on Cupola Practice, ILLUSTRATED BY ONE HUNDRED AND SIX ENGRAVINGS. THIRD THOROUGHLY REVISED AND PARTLY RE-WR.TTEN EDITION. PHILADELPHIA : HENRY CARIDY BAIRD & CO., INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, 810 Walnut Stbeet. KIRK'S FOUNDRY IRONS. A Practical, JTp-to-Date Book, by the well known Eoapert. In one volume, 8vo, 294: pages, illustrated. Price $3.00 net. Free of Postage to any Address in the World, or by Express C. O. D., freight paid to any Address in the United States or Canada. PUBLISHED JUNE, 1911. A PRACTICAL TREATISE ON FOUNDRY IRONS COMPRISING PIG IRON, AND FRACTURE GRADING OF PIG AND SCRAP IRONS ; SCRAP IRONS ; MIXING IRONS ; ELEMENTS AND METALLOIDS ; GRADING IRON BY ANALYSIS ; CHEMICAL STANDARDS FOR IRON CASTINGS ; TESTING CAST IRON ; SEMI- STEEL ; MALLEABLE IRON ; ETC. , ETC. BY EDWARD KIRK, PRACTICAL MOULDER AND MELTER; CONSULTING F.XPERT IN MELTING. AUTHOR OF "the CUPOLA FURNACE," AND OF NUMEROUS PAPERS ON CUPOLA PRACTICE. ILLUSTRATED PHILADELPHIA : HENRY CAREY BAIRD & CO., INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, 810 Walnut Street. 1911 BRANNT'S DRY GLEANER. The only book, including Mat Cleaning and Reno- vating in any language, in one volume, 12nio, S71 pages, illustrated. Price $2.60 net, Free of postage to any address in the world, or by express freight paid to any address in the United States or Canada, PUBLISHED OCTOBER, 1911. THE PRACTICAL DRY CLEANER, SCOURER, AND GARMENT DYER: COMPRISING DRY, CHEMICAL, OR FRENCH CLEANING; PURIFICATION OF BENZINE; REMOVAL OF STAINS, OR SPOTTING; WET CLEANING; FINISHING CLEANED FABRICS ; CLEANING AND DYEING FURS, SKIN RUGS AND mats; CLEANING and DYEING FEATHERS; CLEANING AND RENOVATING FELT, STRAW AND PANAMA HATS; BLEACHING AND DVEING STRAW AND STRAW HATS; CLEANING AND DVEING GLOVES; GARMENT DYEING; STRIPPING; ANALYSIS OF TEXTILE FABRICS. EDITED BY WILLIAM T. BRANNT, EDITOR OF "the TECHNO-CHEMICAL RECEIPT BOOK," FOURTH EDITION, REVISED AND ENLARGED. ILLUSTRATED BY FORTY-ONE ENGRAVINGS. PHILADELPHIA: HENRY CAREY BAIRD & CO., INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, 810 WALNUT STREET. 1911.