[SB 291 .14 14 I Copy 1 JTERNATIONAL BUREAU OF AMERICAN REPUBLICS JOHN BA.RRE1TT. DIREICTOR FRANQSCO J. YANES, SECRETARY RUBBER AND ITS RELATIVES (Reprint of an article from the Monthly Bulletin of the International Bureau of American Republics, December, 1 908) WASHINGTON. D. C. GOVERNMENT PRINTING OFFICE 1909 INTERNATIONAL BUREAU OF AMERICAN REPUBLICS ' JOHN BARREITT. D I R El C T O R FRANCISCO J. YANES. SECRETARY RUBBER AND ITS RELATIVES (Reprint of an article from the Monthly Bulletin of the International Bureau of American Republics, December, 1908) WASHINGTON. D. C, GOVERNMENT PRINTING OFFICE 1909 ^3 p ^ -. i i 1/ r" RUBBP^R is one of the great essentials of modern industrial life. With iron or steel, Avith copper, and with glass it may be compared in the diversity of its use; it has the advantage over these, and may be compared in this latter resjDect to corn, wheat, and the necessary foods, in that it is capable of eternal reproduction if mankind will but apply to its cultivation his ex- perience and scientific knowledge. There is scarcely a device of daily commerce into which rubber does not enter as a necessity, and yet in the annual statistical publi- cation of the Department of Commerce and Labor — Commerce and Navigation of the United States — the student will look in vain for the word " rubber," and not until he examines the word or the phrase " indiarubber," " India rubber," or " India-rubber " will he be able to see how vast and important is the subject before him. This con- servatism — if the term may be here applied — is traceable throughout all the literature of all the libraries of the English-speaking world. The aboriginal native word describing the substance first discovered by the early Europeans was cahuchu., probably pronounced but surely corrupted into caoutchouc. This latter word has spread into the languages of Europe. In French it is the same word; in Ger- man the only modification is to substitute a k for the c^ and in Rus- sian nearly the same change takes place. To be sure the Spanish uses frequently the word goma.^ equivalent to our gum, and this is made more specific by adding the adjective elastica, and the Portu- guese has the word honrtcha, but caucho is commercially well un- derstood, as might be supposed from the first association with the source of suppl}'. Rubber, or India rubber, hoAvever, is undoubtedly the term which will continue to be employed in English to distin- guish this indispensable product of the Tropics. Caoutchouc directly explains the descent of the gum and its adop- tion into the arts, but India rubbei; embraces not only this history but conceals one of the romances *b'f:the industries. Travelers — and it is said Columbus himself AAas One of them — noticed that the Indian inhabitants of America, thought then to be an unknown portion of the Indies, played ball with a curious substance grown in the primi- tive forests and prepared according to native ways. This substance was also made into shoes; it formed a protective coating for gar- ments, and from it were made bottles which could be squeezed to- 990 JAIM 8 ?910 fll [Mr il RUBBER AND ITS RELATIVES. 991 ~' gether so as to eject the liquid contents. This substance was called caucho in some parts of America and the gatherers were cauclieros; ^. in other parts the gatherers w^ere called, because of the shape of their ■ - -m _^ i^??^* II nni mm IHHH nn^ K' .-* A RUBBER TREE OF THE CASTILLOA SPECIES. This tree, like its relatives, the fig, breadfruit, and the trumpet tree, has a general appearance and habit of growth whieh render it easy of recognition. The tree, with its rather smooth light-gray bark, has no striking peculiarities, but the slender, simple branches, with their large oval leaves, pendent in two rows, are similar to those of very few other trees. The Castilloa is native of Mexico and Central America, and thus far it has been supposed that its climatic and cultural requirements were quite different from those of the Para rubber tree, but it now appears that these differences have been greatly overestimated. bottles and the uses to which the Portuguese saw them put, seriii- gueiros, syringe men. From this origin the india prefix of the word 992 INTEKNATIONAL BUREAU OF THE AMERICAN REPUBLICS. is derived. At first the gum, goma elastlca, according to the Spanish, -was merely a curiosity: it was imported into Europe and studied chemically with great interest: it-:v\4vs made into tubes and put to practical use in the laboratory. But in IT TO the English chemist Priestley recommended the use of the gum for effacing the marks of the lead pencil. It rubbed out these marks and was therefore a rubber. It became more widely known as experiment showed its value, and in 1823 Macintosh discovered the method of waterproof- A RUBBER GATHERER IN TROPICAL MEXICO. The "Ulero," or rubber gatherer, is provided with a sharp wedge-pointed ax for tapping the tree, and gourds for conveying the milk to be coagulated. He is generally assigned a given territory. A good collector will gather from 15 to 20 pounds of rubber per day. ing garments, and added another word to the vocabulary. From this date india rubber Avas more and more an article of commerce; it served many purposes, but it also balked the inventors in many direc- tions in which they had hoped it might be applied. Experiments were constantly being made; even the incorporation of sulphur had been tried, but it was not until 1839 that Xelsox Goodyear, in the United States, hit upon a practical method of combining rubber with EUBBER AND ITS RELATIVES. 993 sulphur so as to retain all its ijooci, unique properties, while losing those that had made it hitherto unsuitable. This process was called vulcanization. Rubber — india rubber — is a definite chemical combination of car- bon and hydrogen, expressed by the (proportionate) formula C^ Hj., or CioHj,;. It is a whitish solid, opaque, scarcely reacted upon by the ordinary solvents, but forming fluid or gelatinous masses with the ethers and the coal-tar oils. All this refers, of course, to the chem- ically pure rubber. It will also melt and burn. Physically, rubber will stretch, and when tension is released its mass returns to the origi- nal position and form. Unfortunately, however, rubber in the pure state has three awkward qualities: It loses this distensibility at cer- vSCALE I EUROPE RUSSIA UNITED STATES aooCOOOLbS. fe.OOO.OOOLba. 12.000.0OO Lbs. I io.000.000 Lt>S7 ms. RUBBER BOOTS— THE TRINCirAL BUT BY NO MEANS THE ONLY SOURCE OF " RECLAIMED RUBBER." Note.— Russia is not included in Europe, because it is attempted to show how great is the amount of rubber (from boots and shoes) reclaimed in Russia alone, as contrasted with the remaining portion of Europe. The cut illustrates the amount of old rubber shoes now held in various parts of the world, waiting to be turned into " reclaimexl rubber." tain degrees of heat and cold, it softens under heat, and has a great tendency to stick to itself or to other masses of rubber with which it is brought in contact. Noav, these three qualities of rubber as refined after entering the market from the tropical forests are overcome when it is mixed with sulphur— that is, vulcanized. It can then be molded into various shapes and still remain distensible. The degrees of tem- perature between which it retains these good qualities are very much wider apart, so that climatic changes are less felt by the manufactured product, and consequently rubber articles of an infiniteh^ more varied type can be turned out from the factories. Vulcanized rubber is therefore the substance really implied ordinarily by the word alone. COPY OF THE ORIGINAL ENGRAVING OF THE CASTILLOA ELASTICA, SOMEWHAT REDUCED. The rubber trees of Mexico received a botanical description and name in a paper read by Cervantes before the Royal Botanic Garden Association of the City of Mexico in 1794, and was printed on an engraved plate, a copy of which is in the Library of Congress, Washington. The tree was named Castilla in honor of Castilla, a Spanish botanist, who died in 1793, while engaged in the preparation of a work on the flora of Mexico. RUBBER AND ITS RELATIVES. 995 It might be thought that rubber woukl grow old after being once used in a manufactured article. So it does, but, almost like the met- als, it has a new life when restored to its earlier condition. Reclaimed rubber does not sell for as high a price as fresh rubber just imported, but it has a substantial value, and no discarded bit of rubber goods seems too old or Avorn-out for reclamation and repeated use in the arts. Up to a short time ago old rubber shoes seemed to be the only A RUBBER GATHERER IN BOLIVIA. The tapping of the tree marks the beginning of the rubber gatherer's work. He attaches a small cup to the tree, and with a wedge-shaped ax makes a gash in the bark, being careful not to penetrate the wood. This operation is repeated at intervals of about a foot in a line around the tree, until 5 or 6 cups have been placed, into which the milk flows slowly. The next day a row of incisions is made just below the first, and so on until the ground is reached. A good tree will yield to a height of 20 feet or more. An expert gatherer can tap a hundred trees per day, provided they are close together. or principal source of supply for reclaimed rubber, but to-day, thanks to modern ingenuity in devising chemical processes by wdiich separa- tion is accomplished, rubber is extracted from belts, from hose, or from the scrap of the trade, devulcanized as far as possible, and re- turned to the manufacturer for further use, although in this state it is never so generally serviceable as fresh rubber. The departments of government, the railway companies, and large users of rubber 996 INTERNATIONAL BUREAU OF THE AMERICAN REPUBLICS. make a business of selling discarded articles, and rubber gatherers of the stuff vie with the cauehcros in supplying the market with the results of their labor. To one whose attention has not been carefully directed to the mat- ter the multiplicity of the uses and combinations of rubber will be astonishing. All know how common are rubber bands, lead-pencil eraser tips, stamps, and fountain 2)ens on a writing desk; every minute we see a wheeled vehicle fly past, its peace-destroying noise of yesterday obliterated by the rub- ber tire; but the use of rubber for these purposes, however enor- mous it is in the aggregate, by no means exhausts or even illus- trates the demands for rubber in modern industry. The devices into which rubber enters can no more be enumerated than can those of iron or copper, but among them may be mentioned the various appliances for insula- tion in electricity; without rub- ber an entirely neAv method of telegraphing and telephoning would have to be invented. The air brake of the railroad must have rubber for its proper equip- ment; our fire service would be essentially crippled without rub- ber in the hose, and, in fact, hose of any kind can scarcely be con- ceived without rubber. Packing, belting, and tubing imply the use of rubber. Then there are boots, rubber heels, and overshoes ; coats and gloves for clothing ; the many pharmaceutical, dental, and sur- gical rubber goods, such as blank- ets, stoppers, combs, sheeting, bandages, water bottles, and syringes. In domestic life there are carpets, mats, toys, and cushions; rubber paint and pavement have special advantages in selected places; roller skating would be a tor- ment, and English tennis, Scotch golf, and American baseball would be decidedly tamer without rubber. It is evident that there are two distinct phases to the study of this, commercial commodity. The one is industrial, the other botanical. COAGULATIXi; liri'.HKi: BY THK IS K OF MOON VINE JUICE IN MEXICO. The milk is emptied into this preparation, the impurities remaining in solution, and the clean rubber colleeting in a solid mass, which can be lifted off the top. RUBBER AKD ITS RELATIVES. 997 Before crude rubber becomes the finished product, it must be treated both mechanicall}^ and chemically to make it pliant for its multiform purposes. These processes are complicated, but necessary in trans- forming the raw material into an article ready for manipulation into any of the shapes mentioned above. First the rubber must be washed and cut into bits, then it is squeezed between rollers in order to remove the water and to prepare it in sheets; then it is dried and made ready for compounding. Ver}^ few articles as employed to- day are made of the pure gum ; some compound is necessary in many cases ; in others it is adopted in order to cheapen the price of the goods, which varies according to the quantity of compounded sub- stance used. The consumer can. however, if he wishes to pay the cost, get the best possible article, the judgment of the manufacturer alone determining how much rul)- ber to use. Sulphur is the principal ingre- dient employed in compounding rubber, and serves two purposes; it reduces the amount of pure rub- ber engaged for any article — in it- self a valuable item — and it is the most efficient vulcanizer known. It transforms pure rubber into two distinct commercial substances, ac- cording to the amount of sulphur used, but chiefly according to the intensity of heat applied to effect the combination, for in all proba- bilit}" a chemical change occurs here, in addition to the undoubted physical union of rubber with sul- phur. The one substance is soft rubber in the j^rotean elastic condi- tion familiar to all ; this is produced by combining pure rubber with sulphur at a low temperature. The other substance is hard rubber, ebonite, or vulcanite, in which all elasticity is lost, and the shape into which this is molded is permanently and rigidly retained, within natural temperature limits. Xevertheless, compounded and Aidcan- ized rubber will not last forever: it grows brittle and dull with age, the grittv scales on the surface of combs, etc.. beinw the crvstals of BASE OF TREE INJURED BY TAPPING. Anxiety to obtain tbe largest yield of rubber, with slight regard for the protection of the trees and for future production, has resulted in the permanent injury of many young trees 998 INTERNATIONAL BUREAU OF THE AMERICAN REPUBLICS. unabsorbed sulphur coming to the surface, so that vuk-anized rubber must finally be desulphurized and returned to the trade as reclaimed rubber. Millions have dreamed of the possibilities and fortunes have been premised as the result of a process producing a rubber substitute. Artificial or synthetic rubber would seem so easy ; take only ten atoms of carbon and combine them with only sixteen atoms of hydrogen and you have rubber. But the little trick of adding life to this inert molecule has not yet been learned. The fortune is still there for the lucky inventor who can accomplish it, because carbon and hydrogen COAGULATING THE LATEX IN MEXICO. 1. Spreading the latex on Calathaea leaves. 2. Pressing the two coated leaves together to unite the sheets of rubber. are cheap, inexhaustible even, while rubber may get costlier year by year. The discussion of artificial rubber may therefore be dismissed with a phrase — there is no such thing. Either the exploited article is a humbug, or it contains some proportion of real rubber mixed with substitute ingredients. Rubber substitutes are often of value in the trade because the article manufactured from them only needs that small proportion of rubber they contain. The botanical aspects of rubber are, however, the more fascinating to the investigator, and touch very much more intimately the field in which the International Bureau of the American Republics is EUBBER AND ITS RELATIVES. 999 interested. The plant from which the product comes is peculiarly a l^art of tropical flora, and although there are rubber-producing plants outside of tropical forests, the bulk of the staple is derived from a narrow belt on both sides of the equator, and decidedly better adapted in Latin America to rubber growth than corresponding regions elsewhere. Rubber is the cream from the juice, the milk, or the latex, of several varieties of tree or shrub. This latex is not the same as the sap, and it runs in different channels and performs different functions. As this latex flows from the cut in the tree, it has the appearance of milk and acts much in the same way. If left to itself, the latex separates into a lower fluid and a surface mass, like cream, which is india rubber. A latex possessing from 15 to 40 per cent of rubber (cream) is of value and will pay for working, but a proportion below this is poor and ^.hin, and only in exceptional circumstances will it return any profit. Various ways have been developed or devised for obtain- ing this rubber from the latex, the process being intrinsically coagu- lation. The aboriginal method seems to have been, in Brazil, by smoking heat ; elsewhere natural heat is applied, or mineral or chem- ical additions are made to the milk to separate the rubber. Recently the suggestion has been carried into practice of using the separator apparatus so efficient in the dairy industry. It can not be doubted but that the coagulation process adopted has a noticeable influence on the character and market price of crude rubber, although the kind of tree from which the latex flows, as well as the soil in which it grows, are substantial factors in the result. Having been, up to within recent times, largely a matter of native habit, left altogether in unscientific hands by the buyers of rubber, the coagulation showed remarkable differences, and in some instances has even impressed a name upon the product ; nigger heads, bisquits, and scraps are among the terms applied, but the shape of the crude rubber usually indicates the place from which it is shipj^ed. It will take years to uniformize the various native plans adopted for coagulation. Perhaps this will never be accomplished, but on plantations where careful study can be given to the matter it has been determined that heating by smoke produces the cleanest and purest rubber for commercial export. Rubber is rubber, whether from a tree on the Amazon, in the up- lands of Ceara, the mountains of Bolivia, the jungles of Nicaragua, the fastnesses of the Congo, the cultivated plantations of Ceylon, or the northern regions of Mexico; the important question is, however, whether the plant has an abundant yield of latex. Therefore the source of supply has been the subject of great study for the botanist ever since the first American discoverers saw the curious balls and bottles of the natives. The classification of rubber-bearing trees carries the number well toward one hundred, and if many latex-producting shrubs and vines TAPPING A RUBBER TREE IN CHIAPAS, MEXICO. The obiect in rubber tapping is not merely to avoid the destruction of trees, but to secure the maximum quantity of gum with the least injury to future productiveness The gatherer (uIi'to) makes with his machete.