Boston College Libraries ex libris U&TCt' &rl}&nc HtQ&L Paul Henry Lang 1901-1991 ELEMENTS OF PRACTICAL CHEMISTRY, COMPRISING \*AM$8$y»j A SERIES OF EXPERIMENTS ^i>^ C 4 u. *fU:5s i*«l!r^ EVERY DEPARTMENT OF CHEMtS1gl®C ^4 ^jP WITH ^ 0/j ^C^ DIRECTIONS FOR PERFORMING THEM, AND FOR THE PREPARATION AND APPLICATION OF THE MOST IMPORTANT TESTS AND REAGENTS. BY DAVID BOSWELL REID, EXPERIMENTAL ASSISTANT TO PROFESSOR HOPE, CONDUCTOR OF THE CLASSES OF PRACTICAL CHEMISTRY IN THE UNIVERSITY OF EDINBURGH, LECTURER ON CHEMISTRY TO THE LEITH MECHANICS' INSTITUTION, EXTRAORDINARY MEMBER AND FORMERLY SENIOR PRESIDENT OF THE ROYAL MEDICAL SOCIETY, MEMBER OF THE SOCIETY OF ARTS, AND OV THE ROYAL PHYSICAL SOCIETY. Nec manus inula, nee intellectus sibi permissus, multum valet ; instrumentis et auxiliis res per- ficitur ; quibus opus est, non minus atl intellectum, quam ad manum. — Bacon. MACLACHLAN AND STEWART,Qj§DINTJTJRGH. ^ N> ^- DOMESTIC M.DCCC.XXX. *'G H s c*** m A IS EDINBUBGli: PBJNTUD HY A. BALFOUR AND CO. NJDDRY STKKET. BOSTON C0LLE6I TO THOMAS CHARLES HOPE, M.D. F.R.S. VICE-PRESIDENT OF THE ROYAL SOCIETY OF EDINBURGH, PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF EDINBURGH, THIS WORK IS DEDICATED AS A SMALL TESTIMONY OF RESPECT, AND OF THE SENSE ENTERTAINED OF THE BENEFIT DERIVED FROM HIS INSTRUCTIONS BY HIS FORMER PUPIL, DAVID BOSWELL REID, Digitized by the Internet Archive in 2010 with funding from Boston Library Consortium Member Libraries http://www.archive.org/details/elementsofpractiOOreid PREFACE. The object of this Work is to present the student with a systematic series of experiments, sufficiently broad to lay a proper foundation for acquiring ha- bits of Practical Skill in chemical operations, with precise and minute directions for enabling him to perform them. That Practical Chemistry* besides its acknow- ledged importance to those who are engaged in particular professions, should be gaining ground every day as a branch of general education, was to be expected from the progress of the Science, and the extent to which it can be applied in ex- plaining the phenomena of nature, and improv- ing the processes of art. Chemistry is now no longer confined to particu- lar professions, arts, and manufactures, but extends its dominion over the whole economy of nature, and is seen ministering in every direction to the comforts and necessities of daily life. Wherever there are animals, vegetables, or minerals, — where- VI PREFACE. ever there is earth, air, or water, its agencies are found to be in continued operation, and act an essential part in sustaining the life, order, and har- mony of the whole. The power and number of its instruments, the exactness and precision of its analytic methods, the infinite variety of materials on which it operates, the endless combinations which it can effect, and the creative energies it exerts, have given a splendour to its progress that has arrested the attention of the world, and ex- cited a daily increasing interest in its investigations. Although Practical Chemistry is thus necessarily becoming every day more and more important, yet perhaps its value as an essential branch of che- mical education has not been duly estimated. Nor is it surprising that Chemistry, from the rapidity with which it has arisen from a subordinate art and at- tained a first rank among the liberal sciences, should not have yet been able to unfold all its capabilities, adjust its methods, and adapt its processes to the va- rious aspects under which a science so broad and comprehensive may be viewed, — to its power of imparting knowledge, or increasing practical skill. It is only from adverting to these considerations that we can explain how the practice of a science so eminently practical as Chemistry, has not been more generally taught, and, indeed, not many years ago, it was not considered possible that classes could be arranged for this purpose, unless rilF.FACF. Vll at such an expense as must have precluded the greater number of students from taking advantage of them. I may be here allowed to observe, that tile stu- dent who is engaged in a series of chemical expe- riments, properly conducted, is not only acquiring those practical habits which enable him to apply his knowledge to useful purposes, but is placed in a situation the most favourable that can be con- ceived to render it at once accurate, permanent, and effective. The interest he necessarily feels in the success of a process where he is called upon to act a part, and the striking nature of the pheno- mena, quicken his attention to every thing that may influence the result, and force him to an intimate acquaintance with the chemical relations of every material with which he operates. Nor is it of small importance that the teacher, besides superin- tending each step of the process, is always present to explain every difficulty, and point out whatever is most interesting. Thus habits of mental activity and manual dexterity go hand in hand. Know- ledge acquired in this manner stands on its pro- per basis j it is qualified with all the precision, and impressed with all the force of actual ex- perience. Nothing is allowed to escape the at- tention of the student ; at each step he is called upon to bring all his knowledge to some practical test, — an exercise eminently calculated to strengthen Vlll PREFACE. all the powers of his mind, and to train him to habits of accurate observation and rigorous induc- tion. Although no written directions can supply the place of practical habits, or give that dexterity, readiness, and resource which are to be acquired only by being conversant with the operations of the laboratory, yet much may be done to facilitate the student's progress, by minute and definite di- rections for performing such a series of experi- ments as may enable him to acquire a knowledge of the practical relations of the science, and the mode of operating with different kinds of materials and apparatus. It is with the hope of being use- ful in this respect that the present work has been written. It is divided into two parts ; the first com- prising an arranged series of experiments, and the second including several important subjects with which the student should make himself acquaint- ed as he proceeds with the experiments ; and a de- scription of miscellaneous apparatus, of the method of taking specific gravities, and of determining the strength of acid and alkaline solutions, all of which he should study before commencing the individual experiments. If he should require more informa- tion on apparatus, or on the subject of manipula- tion, than is necessary for performing these experi- ments, he will find Mr. Faraday's excellent Treatise PltEFACE. IX on Chemical Manipulation a work from which he will derive great advantage. In describing all those experiments and pro- cesses which an unexperienced operator cannot perform without danger, I have always carefully pointed out their nature ; and as few products are obtained in this manner which can be applied to any useful practical purpose, it will be better for the beginner to postpone them till he shall have acquir- ed more dexterity in chemical manipulation, or pass them over altogether, when there is no one to guide him in performing them. As the proportions of materials required for the different experiments have been expressed in equi- valent numbers, whenever this could be conveni- ently done, I have been induced to bring forward in the present work a series of diagrams construct- ed on a new plan, from which I have found the Student of Practical Chemistry to derive great benefit, enabling him to perceive at one view the quantities of the different materials required, the nature of the action, and the exact proportion of the products. I have also subjoined a copious table of chemical equivalents, enlarged from a similar table which I published several years ago, in a small pamphlet explaining my Improved Sliding Scale of Chemical Equivalents, in which hydrogen is assum- ed as a standard of comparison. This explanation has been inserted in the present work, and I have X PREFACE. also appended to the general table of chemical equi- valents, a table showing the corresponding equiva- lents of the most important gases by weight and by volume, abridged from a large table in my class room drawn up for the purpose of guiding the gentlemen attending the classes of Practical Che- mistry in their experiments on the gases. It is necessary here to correct a very erroneous opinion entertained by many who have not had an opportunity of attending to the subject, that only a very few pupils can be taught at a time in a class for Practical Chemistry. So far is this from being true, that the very reverse is the case ; and where proper arrangements have been made for car- rying on an effective system of tuition, not only by a proper selection of experiments, but also by ap- paratus peculiarly adapted for the purpose, and as- sistants trained up with this view, the advantage derived by the pupil is, within certain limits, just in proportion to the number attending. For each student not only operates as much as he other- wise would do, but has at the same time an oppor- tunity of witnessing a greater number of processes and experiments, and of seeing the same object ef- fected by a variety of different methods, every one elucidating the other. He is thus not merely in- troduced to the method of effecting particular com- binations and decompositions, but sees an extent of practice which could not be brought before his PREFACE. Xi view in a smaller class ; he acquires a much greater command over his materials, he is taught how to vary his mode of operating as circumstances may require, and he is naturally led to plan operations in his own mind, an object of the very last import- ance to every one who may be called upon pro- fessionally to enter upon any chemical investiga- tion. Having been engaged in teaching Chemistry, and superintending chemical manufactories, I have been led, in the course of the experience which I have had, to make arrangements for conducting the dif- ferent processes and experiments, so as to combine an extensive series of operations, many of which might not at first be considered capable of being introduced into a practical class. And I may per- haps be permitted to state, that I consider this as one of the leading features of the Courses of Prac- tical Chemistry which I have given, and that the number of pupils attending these classes has been progressively increasing since I adopted this plan, a hundred and twenty gentlemen having attended them within the last twelvemonth, not including those who have taken a private course of instruc- tions, or attended an advanced course for analyti- cal chemistry. It is almost unnecessary to observe, that in or- der to secure to the student the full advantages of a course of Practical Chemistry, he must conjoin Xll PREFACE. with it, the study of the principles of the sci- ence, and fortunately, in this school, he has an op- portunity of attending a course of Chemistry too well known to require any encomium from me. CONTENTS. PART I. DIVISION I.— SIMPLE SUBSTANCES. Class I. — simple substances not metallic, and their COMBINATIONS WITH EACH OTHER. CHAP. I. Page OXVGEN, ....... 1 Substances from which it is procured, 2 Preparation from the black oxide of Manganese by heat, 2 Dr. Black's Furnace, 2-3 — Gas- holder, 4 — Preparation from the Black Oxide on a small scale, 5. — Preparation from the Black Oxide by Sulphuric Acid, 6. — Retort stand, 6 — Pneumatic trough, 7 Chauffer and Chimney, 8 — To purify the Manganese, 9. — Precautions in conducting the pro- cesses, 9. — Theory of the action, 10 Quantity procured, 10 — Preparation of Oxygen from the red oxide of Lead, 11. — Apparatus for this process, 11. — Preparation of Oxygen from the red oxide of Mercury, 12.— Apparatus for this process, 12 — Preparation of Oxy- gen from the Nitrate of Potash, 12. — Theory of the action, 13.— Precautions, 13 — Preparation of Oxygen from the Chlorate of Po- tash, 14 Theory of the action, 14 — Chemical relations of Oxy- gen, 15. CHAP. II. HYDROGEN, 16 Preparation of Hydrogen from water by sulphuric Acid and Iron or Zinc, 17 Apparatus, 17— Precautions, 17. — Preparation of Hy- drogen from Steam, 18 — Apparatus for this process, 18. — Gaso- meter for Hydrogen Gas, 19.. — Convenient apparatus for preparing XIV CONTENTS. Page Hydrogen on the small scale, 20. — Theory of the action when Sul- phuric Acid is employed, 21 — Theory of the action when prepared from Steam, 22 — Quantity procured, 22. — Experiments with Hy- drogen, 23. — Detonation with Oxygen, 23. — Theory of the action, 24. — Action of Hydrogen on Spongy Platina, 25 — Dobereiner's instantaneous light apparatus, 25 — Method of filling a bladder with Hydrogen, 27 Action of spongy Platina on a mixture of Oxygen and Hydrogen Gases, 37. — Method of estimating the proportion of Oxygen or Hydrogen in mixed Gases, 28. SECT. I — WATER, .... . . 29 Formation of Water by the explosion of a mixture of Oxygen and Hy- drogen gases, 29 Importance of Water as a Chemical agent, 30 — Distillation of Water — apparatus, 31. — Distillation of Water in glass vessels, 32 — Quantity of gases absorbed by Water, 33 Ac- tion of Water in various decompositions, 34. — Apparatus for drying precipitates by Steam, 35. SECT. II DEUTOXIDE OF HYDROGEN (Oxygenated Wa- ter,) . ...... 35 Short sketch of the process for the preparation of the Deutoxide of Hydrogen, 35 — Its properties, 36. CHAP. III. NITROGEN, 37 Preparation of Nitrogen by burning Phosphorus in Air, 37. — Appara- tus for this process, 37 — Preparation of Nitrogen by the sulphuret- ed Hydrosulphuret of Potassa, 38. — By the Sulphuret of Iron, 38 Quantity obtained, 38 Experiments with Nitrogen, 39 Table of the compounds of Nitrogen with Oxygen and Hydrogen, 40. SECT. I.— PROTOXIDE OF NITROGEN, OR NITROUS OXIDE, ...... 40 Preparation of Nitrous Oxide from the Nitrate of Ammonia, 40 Precautions to be attended to in expelling the Water from the crys- tallized nitrate and from its solution— theory of the action, 42 Properties of Nitrous Oxide, 42 — Its effects on the animal econo- my, 43, — Mode of inhaling Nitrous Oxide — precautions, 45. SECT. II — DEUTOXIDE OF NITROGEN, OR NITRIC OX- IDE, . 4(> Preparation of Nitric Oxide by Nitric Acid and Copper, 40' Theory of the Action, 46. — Precautions, 17 — Preparation of Nitric Oxide CONTENTS. XV Page by Mercury, 47. — Properties of Nitric Oxide, 48. — Preparation of Hyponitrite of Potash, 49. — Experiments with Nitric Oxide, 49— Action of Nitric Oxide on a solution of the Sulphate of Copper, 50. SECT. Ill— HYPONITROUS ACID, . . . .51 SECT. IV— NITROUS ACID, .... 51 Preparation of Nitrous Acid from the Nitrate of Lead, 51. — By mix- ing Nitric Oxide with Oxygen, 52. — Properties of Nitrous Acid, 53. SECT. V— NITRIC ACID, .... 53 Preparation of Nitric Acid from the Nitrate of Potash, 53. — Appara- tus for this process, 53. — Precautions, 54 Method of conducting the distillation with flasks, 54. — Theory of the action, 55 — Prepa- ration of Nitric Acid on the small scale, 56. — To obtain Nitric Acid free from colour, 56. — Tables, showing the specific gravity of several compounds of Nitric Acid and Water in atomic proportions, 57 — Table of the quantity of real acid in distilled Nitric Acid at differ- ent densities, 58 Aquafortis, 59 — Diluted Nitric Acid of the dif- ferent Colleges, 59. — Boiling and freezing points of Nitric Acid, 59 Method of resolving Nitric Acid into Oxygen and Nitrogen Gases, 59 — Properties of Nitric Acid, 60 — Action of Nitric Oxide upon Nitric Acid — Apparatus for this experiment, 61. — To detect Sulphuric or Muriatic Acid in Nitric Acid, 62 To separate Sul- phuric Acid, 62 Tests of Nitric Acid, 63 Uses of Nitric Acid, 64.— Preparation of Oxygenated Nitric Acid, 66. SECT. VI— ATMOSPHERIC AIR, ... 04 Scheele's discovery of the composition of air, 64. — Mode of estimating the quantity of Oxygen in air, 65. — Professor Hope's Eudiometer, 66. — Mode of detecting Watery Vapour and Carbonic Acid in air, 66. — Properties of air, 67. CHAP. IV. SULPHUR, • 68 Melting, crystallization, and sublimation of Sulphur, 68-9 — Chemical relations of Sulphur, 69.. — Table of the compounds of Sulphur with Oxygen and Hydrogen, 70. SECT. I —SULPHUROUS ACID, . . . 70 Mode of preparing Sulphurous Acid, 70. — Mercurial Trough, 71.— XVI CONTENTS. Page Theory of the preparation of Sulphurous Acid, 72. — Experiments with Sulphurous Acid, 73 — Preparation of a solution of Sulphurous Acid in Water, 73. — Woulfe's Apparatus, 74. SECT. II— SULPHURIC ACID, ... 75 Preparation of Sulphuric Acid from Sulphate of Iron, 75.— Fuming Acid of Nordhausen, 76. — Preparation of Sulphuric Acid hy the ac- tion of Sulphurous Acid on Nitrous Acid, 76 Theory of the action, 77— Apparatus for illustrating this on the small scale, 78 — Pro- perties of Sulphuric Acid, 79. — Table showing the quantity of real Sulphuric Acid in liquid Acid of different densities, 80. — Chemical x-elations of Sulphuric Acid, SO — Decomposition of Sulphuric Acid by passing it through a red hot porcelain tube, 81. — Distillation of Sulphuric Acid, .82. SECT. Ill— HYPOSULPHUROUS AND HYPOSULPHU- RIC ACIDS, 83 Method of preparing Hyposulphurous Acid, 83 — Method of prepar- ing Hyposulphuric Acid, 83. SECT. IV— SULPHURETED HYDROGEN, . . 84 Preparation of Sulphureted Hydrogen, 84 — Preparation of Sulphu- ret of Iron, by the combination of Sulphur and Iron, 84. — By ex- pelling Sulphur from Iron Pyrites, 85. — Theory of the preparation of Sulphureted Hydrogen, 86 — Mode of procuring Sulphureted Hydrogen by the Sulphuret of Calcium or of Potassium, 87. — Precautions, 87. — Deleterious effects on the animal economy, 88 Combustion of Sulphureted Hydrogen, 88 'Properties of Sulphu- reted Hydrogen, 89. — Decomposition of Sulphureted Hydrogen by Nitric Acid, 89 — Mode of applying Sulphureted Hydrogen as a chemical agent, 90. — Tests of Sulphureted Hydrogen, 91 Hydro- sulphurets, 91. SECT. V— BISULPHURETED HYDROGEN, . . 91 Preparation of Bisulphureted Hydrogen, 91 Preparation of the Sulphureted Hydrosulphurets, 92 — Properties of the Sulphureted Hydrosulphurets, 92 — Precipitated Sulphur, 92. CHAP. V. SELENIUM, . 93 Selenjc Acid, 94. — Selenurcted Hydrogen, 94. CONTENTS. XVii CHAP. VI. Page PHOSPHORUS, 94- Preparation of Phosphorus from bones, 94 — Precautions, 95. — Me- thod of performing the process on a small scale, 96. — Preparation of Phosphorus from Urine, 97 — Distillation of Phosphorus, 97. — . Precautions in performing experiments with Phosphorus, 93. — Pro- perties of Phosphorus, 99. — Combustion of Phosphorus in Oxygen, 99. — Experiments with Phosphorus, 100. — Table of the compounds of Phosphorus with Oxygen and Hydrogen, 101. SECT. I. PHOSPHOROUS and H YPOPHOSPHOROUS ACIDS, . . • . .101 Preparation of Hypophosphorous Acid, 101 — Preparation of Phos- phorous Acid, 102. SECT. II— PHOSPHORIC ACID, .... 102 Preparation of Phosphoric Acid by burning Phosphorus in air, 102— , Preparation of Phosphoric Acid from the Superphosphate of Lime, 103. — By the action of Nitric Acid on Phosphorus, 104. — Proper- ties of Phosphoric Acid, 104 — Phosphatic Acid, 104. SECT. Ill— HYDRURET of PHOSPHORUS, or PHOS- PHURETED HYDROGEN, . . . . ■ . 104 Preparation of Phosphureted Hydrogen from Phosphorus, Water, and Potash or Lime, 105. — By the action of diluted Muriatic Acid on Phosphuret of Calcium, 106. — Experiments with Phosphureted Hy- drogen, 107. SECT. IV BIPHOSPHURETED HYDROGEN, . . 109 Preparation ofBiphosphureted Hydrogen, 109— Properties of Biphos- phureted Hydrogen, 109. CHAP. VII. CARBON, . . . . . . ; no Preparation of Charcoal, 110 — Preparation of very pure Charcoal, 111 — Properties of Charcoal, 111 — Table showing the quantities of different Gases which Charcoal can absorb, 112. — Chemical rela- tions and uses of Charcoal, 113. SECT. I— CARBONIC OXIDE, . . . .114, Preparation of Carbonic Oxide by Charcoal, Chalk, and Iron Eilings, 114 — Preparation of Carbonic Oxide by the action of Charcoal upon 6 XV111 CONTENTS. Page Carbonic Acid at a high temperature, 114 — Theory of the action, 115 Preparation of Carbonic Oxide by the decomposition of Ox- alic Acid, 115. — Properties of Carbonic Oxide, 116. SECT. II— CAKBONIC ACID, . . . .116 Preparation of Carbonic Acid from Marble, 116 — Properties of Car- bonic Acid, 117 Preparation of Carbonic Aeid in Nooth's Ap- paratus, 118 — Experiments with Carbonic Acid, 118. — Chemical relations of Carbonic Acid, 119. — Method of estimating the quanti- ty of Carbonates in any saline mass, from the volume of Carbonic Acid which can be disengaged, 119 — From the weight of Car- bonic Acid which can be disengaged, 120. — Natural sources of Carbonic Acid, 120. SECT. Ill— HYDRURET OF CARBON OR OLEFIANT GAS, 121 Preparation of Olefiant Gas from Alcohol, 121 — Theory of the ac- tion, 121-2. — Preparation of Olefiant Gas from Oil, &c. 122 — Apparatus for preparing an impure Olefiant Gas from Alcohol, 123 — Method of procuring an impure Olefiant Gas from Coal, 123. — Combustion of Olefiant Gas, 124 — Properties of Olefiant Gas, 124. SECT. IV— BIHYDRURET OF CARBON, OR LIGHT CARBURETED HYDROGEN, ... 125 Method of procuring Carbureted Hydrogen, 125. — Properties of Car- bureted Hydrogen, 125 — Purified Coal Gas, 126. — Sir Humphry Davy's Safety Lamp, 126 — Experiments with the Safety Lamp, 126. SECT. V— BICARBURET OF HYDROGEN, NAPHTHA, &c ....... 127 Quadrocarbureted Hydrogen, 128 — Naphtha, 128 — Bicarburet of Hy- drogen, 129 Naphthaline, 129. SECT. VI.— ALCOHOL, .... 130 Fermentation, 130 — Formation of Alcohol and Carbonic Acid from Sugar, 131. — Yeast, 132 — Distillation of Alcohol from fermented liquor, 132. — Preparation of absolute Alcohol by the Subcarbonate of Potassa, 133 — Mr. Graham's process, 133 — Method of ascer- taining the quantity of Alcohol in spirituous liquors, 134— Proof CONTENTS. Xix Page Spirit, 134 — Table, showing the quantity of absolute Alcohol in spirits of different densities, 135 — Properties of Alcohol, 135 — . Combustion of Alcohol, 135 — Uses of Alcohol, 136. SECT. VII— ETHER, ..... 136 I. Sulphuric Ether, . . . • 137 Preparation of Sulphuric Ether, 137 — Purification of Sulphuric Ether, by Potash and Water, 138 Theory of the action, 138 — Oil of Wine. — Sulphovinic Acid, 139. — Properties of Sulphuric Ether 139.— Uses of Sulphuric Ether, 140. II. Nitric Ether, . . < . . 140 Preparation of Nitric Ether, 140. — Process of the Dublin Pharmaco- pceia, 141. — Precautions, 142. — Purification of Nitric Ether, 142.— - Spirit of Nitric Ether, 142, SECT. VIII.— PYROXILIC AND PYROACETIC SPIRIT, 143 SECT. IX— CYANOGEN, OR BICARBURET OF NITRO- GEN, 144 Preparation of Cyanogen from the Bicyanide of Mercury, 144. — Pre- paration of the Bicyanide of Mercury by Prussian blue and the Pe- roxide of Mercury, 144.— Theory of the action, 143. — Properties of Cyanogen, 146. 1. Cyanic Acid, < ; <* 146 Preparation of Cyanic Acid, 146. 2. Hydrocyanic or Prussic Acid, „• . 147 Vauquelin's process for preparing strong Hydrocyanic Acid, 147. — Theory of the Action, 148. — Preparation of the strong acid by the action of Muriatic Acid on the Bicyanide of Mercury, 148. — Pre- paration of a diluted Hydrocyanic acid from the Ferrocyanate of Potash, 149. — Dr. Ure's process, 149. — Properties of Hydrocyanic Acid, 150. — Preparation of Gaseous Hydrocyanic Acid, 151. — Me- thod of estimating the strength of Hydrocyanic Acid, 151. — Detec- tion of Muriatic Acid in Hydrocyanic Acid, 152. — Antidotes to Hydrocyanic Acid, 152. — Tests of Hydrocyanic Acid, 153. 3. Ferrocyanic Acid, . . . 151 Preparation of Ferroprussiate of Potash, 154. — Diagram, showing the composition of Ferrocyanic Acid, 155 — Preparation of Ferrocyanic XX CONTENTS. Page , Acid from Ferrocyanate of Potash by Tartaric Acid, 155. — By Hydrosulphuret of Barytes and Sulphuric Acid, 155. 4. Stilphocyanic Acid, . . . 156 Preparation of Sulphocyanic Acid, 156. 5. Cyanides of Chlorine, Iodine, and Bromine, 157 Cyanide of Chlorine, 157 — Cyanide of Iodine, 158. — Cyanide of Bromine, 158. SECT. X— VEGETABLE ACIDS, . . 158 Their general properties, 158 — Table showing their composition, 159. 1. Acetic Acid, . . .159 Methods of obtaining Acetic Acid, 159 — Preparation of strong Acetic Acid 160. — Process of the Edinburgh Pharmacopoeia, 160, — Prepara- tion of strong Acetic Acid from the Acetate of Copper, 161. *— Table showing the specific gravities of compounds of Acetic Acid and Water in different proportions, 161 — Preparation of the weak Ace- tic Acid of the Pharmacopoeias, 161 — Method of estimating the strength of Acetic Acid, 162 — Properties of Acetic Acid, 162.-— Method of detecting adulterations of Acetic Acid, 162, 2. Tartaric Acid, • . . . 162 Preparation of Tartaric Acid from Tartrate of Lime, 162. — Prepara- tion of Tartrate of Lime, 163. — Theory of the action, 163 — Proper- ties of Tartaric Acid, 164. 3. Citric Acid, . . . 164 Preparation of Citric Acid, 164. — Properties of Citric Acid, 165. 4. Oxalic Acid, .... 165 Preparation of Oxalic Acid from Sugar, 166. — Properties of Oxalic Acid, 166. — Antidotes to Oxalic Acid, 166 — Method of distin- guishing between Oxalic Acid and Sulphate of Magnesia 167. 5. Benzoic Acid, . . . .167 Preparation of Benzoic Acid from Gum Benzoine, 167. — Another process for preparing Benzoic Acid, 168 — Properties of Benzoic Acid, 168. 6. Gallic Agid, Succinic Acid, &c. . • 169 Preparation of Gallic Acid from gall nuts, 169— Preparation of Sue- j CONTENTS. XXI Page cinic Acid from Amber, 169 — Boletic, Igasuric, Camphoric, Malic, Mucic, Mellitic, Moroxylic, Menispermie Acids, 170. SECT. XL— BISULPHURET OF CARBON, . 171 Preparation of the Bisulphuret of Carbon, 171 — Apparatus for this process, 171. — Properties of Bisulphuret of Carbon, 172. CHAP. VIII BORON, . ... .173 Preparation of Boron, 173 Properties of Boron, 173. BORACIC ACID, ... . 174- Preparation of Boracic Acid, 174 Properties of Boracic Acid, 174. CHAP. IX. CHLORINE, . , . 175 Table showing the compounds of Chlorine with the substances already treated of, 176 — Preparation of Chlorine by Peroxide of Manga- nese and Muriatic Acid, 176 — Theory of the action, 177. — Prepa- ration of Chlorine by Peroxide of Manganese, Chloride of Sodium, and Sulphur, 178 — Theory of the action, 178. — Properties of Chlorine, 178-9.— Chlorine Water, 179 — Uses of Chlorine, ISO. — Experiments with Chlorine, 181-2 Tests of Chlorine, 181. SECT. L— PROTOXIDE OF CHLORINE, . . 181 Preparation of Protoxide of Chlorine from Chlorate of Potassa, 181. Theory of the action, 184. — Properties of Protoxide of Chlorine, 185. SECT. II— PEROXIDE OF CHLORINE, . . 185 Preparation of the Peroxide of Chlorine, 186.— Method of performing the Process on a small scale, 186 — Theory of the process, 186. — , Properties of the Peroxide of Chlorine, 187. SECT. Ill— CHLORIC ACID, . . 187 Preparation of Chloric Acid from Chlorate of Barytes, 188 Prepara- tion of Chlorate of Barytes, 1 88.— Preparation of Chlorate of Po. XX11 CONTENTS. Page tassa, 188 — Properties of Chloric Acid, 189 — Perchloric Acid, 189. SECT. IV.— MURIATIC ACID, ... 189 Preparation of Muriatic Acid from Salt, 190 — Theory of the action, 190, — Method of testing the presence of Sulphuric Acid, 191 — ■ Formation of Muriatic Acid by detonating together Chlorine and Hydrogen, 191. — Preparation of Gaseous Muriatic Acid, 192 Properties of Muriatic Acid, 192 — Experiments with Muriatic Acid, 192 — Method of estimating the strength of Muriatic Acid, 193. — Table showing the quantity of real Acid in common Muriatic Acid at different densities, 194. — Tests of Muriatic Acid, 194.— Chemical relations of Muriatic Acid, 194. SECT. V— CHLORIDE OF NITROGEN, . . 19$ Preparation of Chloride of Nitrogen by Muriate of Ammonia, 1 95.— Explosion of the Chloride, 195. SECT. VI— NITRO-MURIATIC ACID, . . 195 Nature of Nitro- Muriatic Acid, 196. — Preparation of Nitro-Muriatic Acid, 196. SECT, VII— CHLORIDES OF SULPHUR, PHOSPHO- RUS, AND CARBON ; HYDROCARBURET OF CHLO- RINE, AND CHLOROCARBONIC ACID . . 197 reparation of Chloride of Sulphur, 197. — Preparation of Bichloride > of Phosphorus, 197.— Preparation of Hydrocarburet of Chlorine, 197 Perchloride of Carbon, 197. — Chloride, and Subchloride of Carbon, 198. — Chlorocarbonic Acid, 198. CHAP. X. IODINE, . • ... 198 Preparation of Iodine from Kelp, 199. — Method of Collecting the Iodine, 199 Theory of the process, 200. — Properties of Iodine, 201 — Experiments with Iodine, 201 — Detection of Iodine by Starch, 202. SECT. I.-IODIC ACID, ... 203 Preparation of Iodic Acid by Protoxide of Chlorine and Iodine, 203. Properties of Iodic Acid, 203. contents. xxiii Page SECT. II— HYDRIODIC ACID, . 204 Preparation of Hydriodie Acid by Phosphorus, Water, and Iodine, 204 — Theory of the Action, 205 — Method of procuring a Solution of Hydriodie Acid, 205 — Theory of the process, 206 Another Process for the same, 206 — Tests of t Iodic Acid, 207. — Experi- ments with Iodic Acid, 207. SECT. Ill— IODIDE OF NITROGEN, CHLORIODIC ACID, &c. . . .... 208 Preparation of Iodide of Nitrogen, 208 — Iodide of Sulphur — Chlo- riodic Acid, 209. CHAP. XI. BROMINE, . . . 209 Preparation of Bromine from Bittern, 209.— Theory of the process, 209., CHAP. XII. FLUORINE, . . • .211 SECT. I— FLUORIC ACID, . . . . 211 Preparation of Fluoric Acid from Fluor Spar, 21 1.— Precautions, 212. .—Properties of Fluoric Acid, 21 2.— Method of Etching on Glass with Fluoric Acid, 213. SECT. IL—FLUOBORIC ACID, . 214 Preparation of Fluoboric Acid, 214 — Properties of Fluoboric Acid, 214. SECT. III.— FLOUSILICIC GAS, . . . 214 Preparation of Fluosilicic Gas, 214.— Properties of Fluosilicic Gasj 215. XXIV CONTENTS. CLASS II. METALS, AND THEIR COMBINATIONS WITH NON-ME- TALLIC SUBSTANCES, AND WITH ONE ANOTHER. ORDER. I. ALKALIFIABLE METALS. CHAP. I. Page POTASSIUM, .... . glG Discovery of Potassium by Sir H. Davy, 216 — Gay Lussac and Then- ard's Process for preparing Potassium, 216 — B runner's Process, 217. — Description of an improved form of Apparatus for preparing; it by Brunner's process, 217 — Method of luting the Iron Pot, 218. — Description of the Furnace for this process, 219 — Description of the Receiver used, 220— Precautions necessary in conducting this Process, 221 Method of purifying the Potassium, 222. — Pro- perties of Potassium, 222. — Experiments with Potassium, 223. SECT. I.—POTASSA OR POTASH, ... 224 Preparation of Potassa from the Subcarbonate, 224 — Theory of the process, 225. — Method of detecting Carbonic A eid and Lime, 225. —Preparation of Potassa Fusa — of Potassa cum Calce, 225. — Hy- drate of Potassa, 226 — Experiments with Potassa, 227. — Uses of Potassa, 228 — Mode of preparing Pearl-ashes, 228. SECT. II.— SALTS OF POTASSA; SULPHURET, CHLO- RIDE, AND IODIDE OF POTASSIUM, . 228 Nitrate of Potassa, 228 — Preparation of Nitre, 229 — Properties and uses of Nitre, 229 — Experiments with Nitre, 229 — Preparation of Sulphate of Potassa, 230— Theory of the Action, 230 — Sulphas Potassae cum Sulphure, 231. — Preparation of Sulphuret of Potas- sium, 231 — Theory of the Process, 232. — Preparation of the Hy- drosulphuret of Potassa, 232 — Sulphureted Hydrosulphuret of Potassa, 233 — Carbonate of Potassa, 233 — White Flux, 234 — Black Flux, 234 — Bicarbonate of Potassa, 235 — Ferrocyanate of , Potassa, 235. — Preparation of Acetate of Potassa.— Tartrate of CONTENTS. XXV Page Potassa — Bitartrate — Chlorate, 236 — Chloride of Potassium, 237. — Preparation of Hydriodate of Potassa, or, Iodide of Potassium, 237. CHAP. II. SODIUM, . '. 238 Preparation of Sodium, 238 — Properties of Sodium, 239. SECT. L— SODA, . . . . . . 239 Preparation of Soda, 239. SECT. II SALTS OF SODA, CHLORIDE OF SODA, AND SULPHURET AND CHLORIDE OF SODIUM, . 239 Preparation of the Sulphate of Soda, 239. — Preparation of Carbonate of Soda from Kelp or Barilla, 240. — Bicarbonate of Soda, 240. — Preparation of Phosphate of Soda, 240 — Preparation of Chloride of Sodium, or Muriate of Soda, 241 — Detection of Magnesia in Salt, 242.— Method of preparing Chloride of Soda, 242 Prepara- tion of Tartrate of Potassa and Soda, 243 Biborate of Soda, or Borax, 243. CHAP. III. LITHIUM, . 244 Lithia, 244. CHAP. IV. AMMONIA, ..... .244 Preparation of Ammoniacal gas, 244 — Preparation of Water of Am- monia, 245 — Theory of the Process, 246 Table showing the quantity of real Alkali in Ammonia of different densities, 246. — Preparation of Alcohol Ammoniatum, 246 — Properties of Ammon- iacal Gas, 247 — Tests of Ammonia, 247. SALTS OF AMMONIA, . . 248 Nitrate of Ammonia, 248 Sulphate — Phosphate — Carbonate — Bi- carbonate of Ammonia, 248 — Preparation of Subcarbonate of Am- monia, 248.—- Preparation of the Muriate of Ammonia, 249-50. XXVI CONTENTS. ORDER II. ALKALINE GEOFIABLE METALS. CHAP. I. Page CALCIUM AND ITS COMPOUNDS, . . . [250 Method of procuring Calcium, 250 — Preparation of Lime, 251. — Hy- drate of Lime, 251. — Properties of Lime, 252— Tests of Lime, 252. Experiments with Lime, 252-3. SALTS OF LIME, CHLORIDE OF LIME, CHLORIDE OF CALCIUM, &c . .... 254 Preparation of Sulphate of Lime, 254 — Sulphuret of Calcium, 254. — Sulphureted Hydrosulphuret of Lime, 254 — Nitrate of Lime, 255. Phosphate of Lime, 255. — Phosphuret of Calcium, 255. — Car- bonate of Lime, 255 — Muriate of Lime, 255 — Chloride of Cal- cium, 256. — Chloride of Lime, 256 — Method of ascertaining the strength of Chloride of Lime,'257-8. CHAP. II. BARIUM AND STRONTIUM, 258 Preparation of Barium, 258. BARYTA, . • • 258 Method of procuring Baryta from the Nitrate, 258—From the Carbo- nate, 258.— Hydrate of Baryta, 258.— Tests of Baryta, 259 — Perox- ide of Barium, 259. — Preparation of Nitrate of Baryta, 259 Sul- phate of Baryta, 260. — Sulphuret of Barium, 260. — Hydrosulphu- ret of Baryta, 260. — Preparation of Carbonate of Baryta, 260 — Muriate of Baryta, 260. STRONTIA, .... 261 Preparation of Strontia, 261.— Method of distinguishing between Ba- ryta and Strontia, 261— Properties of Strontia, 261. CONTENTS. XXVH ORDER III. GEOFIABLE METALS. CHAP. I. MAGNESIUM, .... 262 Preparation of Magnesium, 262. — Preparation of Magnesia from the Carbonate, 262. — Preparation of Magnesia by Precipitation, 262. — Method of detecting Carbonic Acid in Magnesia, 262. — Method of distinguishing Magnesia, 263. — Preparation of Sulphate of Magne- sia by the Carbonate, 263 — From Bittern, 263. — Detection of Mu- riate of Magnesia in the Sulphate, 263.— Preparation of Carbonate of Magnesia, 264 Of the Bicarbonate, 264. CHAP. II. ALUMINIUM, SILICUM, &c. . . 264 ALUMINA, .... 264 Preparation of Alumina from Alum, 264.— Method of distinguishing Alumina, 265 — Sulphate of Alumina and Potassa, 265 — Prepara- tion of a Pyrophorus with Alum and Sugar, 265 — Burnt Alum, 266. SILICA, . . 266 Method of procuring Silica, 266. — Preparation of Glass, 267 Me- thod of Colouring Glass, 267. — Silicated Potassa, 267. — Window Glass, 268. GLUCINUM, ITTRIUM, ZIRCONIUM, THORINUM, 268 ORDER IV. COMMON METALS, WHOSE OXIDES CANNOT BE REDUCED BY HEAT ALONE. CHAP. I. IRON, . . . . .269 Oxidation of Iron, 269 Combustion of Iron in Oxygen, 269. — Pre- paration of Protoxide of Iron, 270.— Preparation of Peroxide of Iron from the Sulphate, 271. — Steel, 271 — Method of Tempering Steel, 271. — Detection of Iron by the Gall-nut, 272— By Ferrocyanate of Potassa, 273. XXV111 CONTENTS. Page SALTS OF IRON, . 273 Preparation of Nitrate of Iron, 273 — Preparation of Sulphate of Iron from the Sulphuret, 274. — By the action of Sulphuric acid on Iron, 274 — Method of expelling the water of crystallization from the Sul- phate, 275 Action of Nitric Acid on Sulphate of Iron, 275 — Prepa- ration of Carbonate of Iron by precipitation, 275 — By the action of Carbonic Acid on Iron filings, 276. — Preparation of the Liquor Ferri Alkalini, 277 Preparation of Acetate of Iron, 277 — Preparation of Tartrate of Potassa and Iron, 278 — Gallate of Iron, 278 — Me- thod of preparing Ink, 278. — Experiments with Ink, 279 — Prepara- tion of Ferrocyanate of Iron, or Prussian blue, 279 — Muriate of Iron, 280 — Muriate of Ammonia and Iron, 280 — Chloride of Iron, 280. CHAP. II. LEAD, . i . .281 Preparation of Lead from the Sulphuret, 284. — Preparation of very pure Lead from the Acetate of Zinc, 281. — Theory of the action, 282. — Oxi- dation of Lead in a Muffle, 282. — Muffle Furnace, 283.— Precautions in using Muffles, 283. — Preparation of Protoxide of Lead from the Nitrate, 283. — Massicot, 283— Preparation of Red Oxide or Deu- toxide of Lead, 284 — Preparation of Peroxide of Lead, 284. — Deoxi- dation of the Oxides of Lead by Charcoal, 284 — Tests of Lead, 284. SALTS OF LEAD, . . .285 Preparation of Nitrate of Lead, 285 — Preparation of Sulphate of Lead, 285. — Phosphate of Lead, 2S6 — Preparation of Carbonate of Lead or White Lead, 286. — Preparation of Acetate of Lead or Sugar of Lead, 286. — Preparation of Binacetate of Lead, 286. — Preparation of the Subacetate of Lead, 286. CHAP. III. COPPER, . ... 287 Preparation of pure Copper from the Sulphate of Iron or Zinc, 287. — Method of giving Copper a bright metallic surface, 287 — Preparation of Protoxide of Copper from the Protomuriate, 287 Preparation of the Peroxide from the Nitrate, 287 — .Action of Ammonia on the Per- oxide of Copper, 288 —Tests of Copper, 288. SALTS OF COPPER, .... 288 Preparation of Nitrate of Copper, 288. — Sulphate of Copper, 289 — Preparation of Ammoniated Copper, 289 Preparation of Sulpha- CONTENTS. Xxix Page ret of Copper, 290 — Preparation of Carbonate of Copper, 290. Preparation Fof Subacetate and Binacetate of Copper from Verdi- gris, 290. — Detection of Chalk and Plaster of Paris in Verdigris, 290. — Binacetate of Copper, 291 — Action of Chlorine on Copper, 291 — Preparation of Permuriate of Copper, 291 Preparation of Protomuriate of Copper, 291 — Action of the Salts of Copper on Flame, 291. CHAP. IV. ZINC, .... 292 Method of procuring Zinc from the Oxide, 292.— Preparation of the Oxide by the Combustion of Zinc, 292 — Preparation of the Oxide by precipitation from a salt of Zinc, 293 Method of distinguishing Zinc, 293 — Preparation of Nitrate of Zinc, 293 — Preparation of Sulphate of Zinc, 293. — -Preparation of Carbonate of Zinc, 293, Preparation of Acetate of Zinc, 294? — Muriate of Zinc, 294. CHAP. V. ANTIMONY, . . ... 395 Preparation of Metallic Antimony from the Sulphuret by Cream of Tartar, 295. — By Iron filings and Nitre, 295 — Combustion of Me- tallic Antimony, 296.— Preparation of Protoxide of Antimony from the Muriate, 296 — From the Sulphuret by Nitre, (Crocus of Anti- mony,) 297 — Preparation of the Protoxide by exposing the Sulphu- ret to Heat, (Glass of Antimony.) 297 — Preparation of the Deutox- ide from the Protoxide, 297. — From the Peroxide, 297. — Prepara- tion of the Peroxide, 298 — Preparation of the Oxide of Antimony with Phosphate of Lime, 298 — Nature of this Substance, 298-9. SALTS OF ANTIMONY, SULPHURET AND CHLORIDE OF ANTIMONY, . . 299 Preparation of the Sulphate of Antimony, 299 — Purification of the Sulphate of Antimony, 300 — Precipitated Sulphuret of Antimony, 300 Kermes Mineral, 301. — Golden Sulphuret of Antimony, 301. Preparation of Tartrate of Antimony and Potassa, 301. — Composi- tion of Tartar Emetic, 302. — Chemical relations of Tartar Emetic, 302 Antidotes to Tartar Emetic, 303 — Tests of Tartar Emetic, 303 Method of applying Sulphureted Hydrogen for the detection of Antimony, 303-4 — -Preparation of the Muriate of Antimony, 304? Chloride of Antimony, 305. XXX CONTENTS. CHAP. VI. Page ARSENIC, .,..,. 305 Reduction of Metallic Arsenic from the White Oxide, 305 — Method of performing this process in a Glass Tube, 306. — Properties of Me- tallic Arsenic, 307 Experiments with Arsenious Acid, 307. — So- lution of Arsenious Acid, 307. — Preparation of Arsenite of Potassa, 307 — Action of Sulphureted Hydrogen on Arsenious Acid, 307-8. — On a Solution of Arsenite of Potassa, 308. — Action of Salts of Copper on Arsenious Acid in Solution, 308. — Preparation of Am- moniaco-Nitrate of Copper, 309. — Action of this Salt on a solution of Arsenious Acid, 309 — Action of Nitrate of Silver on a Solution of Arsenious Acid, 310 — Action of Nitrate of Silver on Phosphate of Soda, 310 — Ammoniaco-Nitrate of Silver, 310 — Action of this Salt on Arsenious Acid, 310 — On Phosphate of Soda, 310. — Action of Lime Water on a Solution of Arsenious Acid, 310. — Action of Bichromate of Potassa on a Solution of Arsenious Acid, 311. — Ac- tion of this Salt on Tartar Emetic, 311. — Circumstances to be at- tended to in testing the presence of Arsenious Acid, 311. — Method of extracting the Metallic Arsenic from the Precipitates obtained by the above Tests, 312. — Characters of Metallic Arsenic, 312 -3. — Me- thod of proceeding when there are only indistinct appearances of Metallic Arsenic, 313 — Method of Testing a very minute quantity of Metallic Arsenic, 313. — Precautions in examining the contents of the Stomach to ascertain the presence of Arsenic, 314 Method of proceeding with any solid powder which may be found in the Stom- ach, 314. — Preparation of Arsenic Acid, 314-15. — Preparation and Characters of Arseniate of Potassa, 315. — Method of preparing Ar- Benureted Hydrogen, 315. — Preparation of the Protosulphuret of Arsenic, (Realgar,) 315. — Preparation of the Yellow Sulphuret, (Orpiment,) 315. — Chloride of Arsenic, 316, — Antidotes to Ar- senic, 316. CHAP. VII. TIN, 316 Reduction of the Oxide of Tin, 316 — Tin in a minute state of divi- sion, 316 — Preparation of the Protoxide of Tin, 317 Of the Per- oxide, 317 — Method of forming the Mohre Mctallique, or Crystal- lized Tin Plate, 317-18.— Preparation of Muriate of Tin, 318 Tests of Tin, 318 — Purple of Cassius, 318. CONTENTS. XXXI CHAP. VIII. Page BISMUTH, 319 Oxide of Bismuth, 319. — Method of preparing Crystals of Metallic Bismuth, 319 — Preparation of Nitrate of Bismuth, 319 — Of Sub- nitrate and Binitrate of Bismuth, 319-20 — Tartrate of Bismuth, 320. CHAP. IX. MANGANESE, 320 Preparation of Metallic Manganese from the Peroxide, 320 Prepar- ation of the Protoxide, 321 — Of the Deutoxide, 321 Of the Red Oxide, 321 — Peroxide of Manganese, 321 Preparation of Man- ganesite of Potassa, (Mineral Chameleon,) 321-22 Manganesic Acid, 322 — Method of separating the Oxide of Iron from the Oxide of Manganese, 322. — Method of Testing the presence of Iron i in Muriate of Manganese, 323 — Preparation of a Solution of the ■ Muriate of Manganese, 323. CHAP. X. CHROME, ...... 383 Preparation of Chrome, 323. — Preparation of Protoxide of Chrome from Chromate of Mercury, 323— Preparation of Chromic Acid from Chromate of Baryta, 324. — Chloro-Chromic Acid, 324 Fluo- Chromic Acid, 321. SALTS OF CHROME, 325 Preparation of Chromate of Potassa, 325 — Of Bichromate of Potassa, 325 — Chromate of Baryta, 326 — Chromate of Lead, (Chrome Yellow,) 326 — Subchromate of Lead, 326 Chromate of Mercury, 326. CHAP. XL COBALT, . ... . . 327 Preparation of Metallic Cobalt from Zaffre, 327 Muriate of Cobalt, (sympathetic ink,) 327 — Action of Salt on the Muriate of Cobalt, 328. XXX11 CONTENTS. ORDER V. METALS WHOSE OXIDES CAN BE REDUCED BY EXPOSURE TO HEAT, WITHOUT INFLAM- MABLE MATTER. CHAP. I. Pege MERCURY, ...... 328 Preparation of Metallic Mercury from the Sulphuret, 328 — Method of conducting this process on a small scale, 329 — Precautions, 329. —Theory of the process, 330 — Characters of pure Mercury, 330. — Method of separating Mercury from Dust, or a Crust of Oxide, 331. — Characters of Adulterated Mercury, 331. — Distillation of Mer- cury, 331 — Method of separating Oil, 332. — Method of separating Zinc, 333. — Dr. Priestley's Method of purifying a small quantity of Mercury, 333 — Preparation of the Protoxide of Mercury by Calo- mel and Potassa, 333. — By Calomel and Lime, 331. — Theory of the action, 334 — Preparation of the Peroxide of Mercury by Ni- trous Acid, 334-5. — By exposing Mercury to air at a high tempera- ture, 335. — Method of detecting adulterations of the Peroxide, 335. ,— Tests of Mercury, 336-7. SALTS OF MERCURY, CHLORIDES, IODIDES, AND SULPHURETS OF MERCURY, . • . 337 Preparation of the Protonitrate of Mercury, 337. — Of the Pernitrate, 337. — Circumstances to be attended to in preparing the Nitrates of Mercury, 338. — Preparation of Persulphate of Mercury, 338. — Theory of the process, 338 — Preparation of the Protosulphate of Mercury, 339. — Theory of the process, 339 — Preparation of the Subsulphateof Mercury, (Turpeth Mineral,) 339 — Theory of the pro- cess, 339. — Preparation of Protosulphuret of Mercury, 3-10. — Blacl^ Sulphuret of the Pharmacopoeias, (Ethiop's Mineral,) 340 — Prepara- tion of Bisulphuret of Mercury, by the Pernitrate, 340 — By the di- rect combination of Sulphur and Mercury, (Artificial Cinnabar,) 341 . Method of detecting adulterations of the Bisulphuret, 341. — Vermilion, 341 — Carbonate of Mercury, 341 — Preparation of Per- carbonate of Mercury by the Pernitrate or Bichloride, 342 Theo- ry of the Action, 342. — Preparation of the Acetate of Mercury, 343. — Of the Peracetate, 343. — Preparation of Fulminating Mercury, 4 CONTENTS. XXxii Page (Cyanate,) 343 — Experiments with Fulminating Mercury, 341 Preparation of Chloride of Mercury (Calomel) from the Bichloride, 344-5 — Precautions, 345 — Method of separating any Bichloride that may be sublimed along'^with the Chloride, 345-6 Preparation of Calomel by the Sulphate of Mercury and Chloride of Sodium, 346. — Preparation of Calomel from the Protonitrate of Mercury, ( Calo- melas Precipitatum,) 347. — Theory of the action, ; 347. — Action that would take place were Pernitrate employed, 347-8 Prepara- tion of Bichloride of Mercury (Corrosive Sublimate) by the Persul- phate, 348 — Theory of the process, 349 — Characters of the Bi- chloride, 349 — Preparation of the Muriate of Ammonia and Mer- cury (Hydargyrum Precipitatum Album,) 350. — Preparation of Io- dide of Mercury, 350.— Of Periodide of Mercury, 350. CHAP. II. SILVER, 351 Method of procuring pure Silver by Precipitation, 351 — Arbor Dia- nae, 351. — Process of Cupellation, 352 Mode of separating Silver from Alloys by Nitric Acid and Chloride of Sodium, 352 — Theory of the action, 353 — Mr. Keir's Mode of dissolving Silver, 354 — Preparation of Oxide of Silver, 354. — Of Fulminating Silver, 354 — Precautions, 354 — Tests of Silver, 355 — Preparation of the Nitrate of Silver, 355. — Of the Fused Nitrate, (Lunar Caustic,) 355 — Marking Ink, 356. — Preparation of Sulphate of Silver — Of Phos- phate of Silver — Of Carbonate of Silver — Of Cyanate of Silver, 356. — Preparation of Chloride of Silver, (Horn Silver,) 357. CHAP. III. GOLD, 357 Method of separating Gold from an Alloy, 357 — Operations of Quar- tation and Parting, 357. — Action of the Oxyhydrogen Blow-pipe on Gold, 358 — Preparation of the Peroxide of Gold, 358.— Of the Chloride of Gold, 358 — Of Fulminating Gold, (Ammoniuret,) 359- — Action of Sulphate of Iron on the Chloride of Gold, 359. — Purple of Cassius, 359 — Fusion of Borax with Chloride °f Gold, 359.— Ethereal Solution of Gold, 359. CHAP. IV. PLATINA, -360 Method of pro iring Metallic Platina from its ores, 360 — Preparation of Spongy Platina, 360.— -Preparation of Oxide of Platina, 360 — . c XXXIV CONTENTS. Page Of Peroxide of Platina, 361 Tests of Platina, 361 — Sulphate of Platina — Fulminating Platina— Chloride of Platina, 361. — Action of Alcohol on Sulphate of Platina, 362. CHAP. V. NICKEL, 362 Preparation of Nickel from the 'Sulphate, 362. — Method of expelling Arsenic completely from, 362-3. — Oxide of Nickel, 363. — Peroxide of Nickel, 363. ALLOYS— AMALGAMS, &c 363 Method of forming Amalgams with Mercury, 364. — Brass, 364. — Cementation, 364 — Dutch Gold and Pinchbeck, 364 — Bronze, 364 —Speculum Metal, 364.— Pewter, 365 Plumber's Solder, 365.— Printing Types, 365 — Fusible Alloy, 365 — Gold Coin, 365.— Standard Silver, 365. — Amalgam for the Electrical Machine, 365. — For Looking Glasses, 365. — Fusible Spoons, 365. — Tinned Iron, 365, — Mode of Coating Copper Vessels with Tin, 366 Mode of Silvering Copper, 366. — Mode of Gilding Silver, Copper, and Brass, 366.— Mode of Gilding Steel, 366 Mode of preparing Gold Pow- der for Painting, 366. a DIVISION II. VEGETABLE AND ANIMAL SUBSTANCES. CHAP. I. GUM, SUGAR, STARCH, GLUTEN, TANNIN, LIGNIN, 368 Experiments with Gum, 368. — Sugar, 369 — Action of Chlorate of Potassa and Sulphuric Acid on Sugar, 369. — Action of Nitric Acid on Sugar, 369. — Method of forming Gum, Starch, &c. into Sugar, 370 — Starch, method of procuring, 370 — Gluten, method of pro- curing, 371. — Gliadine and Zimome, 371. — Lignin, 371 — Method of procuring Tannin, 372 — Characters of Tannin, 372. CHAP. II. COLOURING MATTER, .... 372 Method of preparing Coloured Test Papers, 372-3 — Blue infusion of Cabbage, 373.— Litmus and Turmeric Test Papers, 373, CONTENTS. XXXV EXPERIMENTS WITH COLOURING MATTER, 37! Method of forming Lakes, 374. — Carmine, 374— Method of Dyeing with Indigo, 375 — Sublimation of Indigo, 375 Method pf Dyeing with BrazilWood, 375-6.— Mordants, 376 Adjective Colours, 376. — Substantive Colours, 379 — Method of dyeing Yellow, Black, &c 376 — Action of Chloride of Lime on Colouring matter, 377. CHAP. III. VEGETABLE ALKALIS, .... 377 Method of procuring the Vegetable Alkalis, 377. SECT. I.— MORPHIA, MECONIC ACID, NARCOTINE, 378 MORPHIA, . . . .378 Composition of Opium, 378 — Process for extracting Morphia, 378. — Precautions, 379 — Properties of Morphia, 379 Sulphate of Morphia, 380 — Acetate — Nitrate— Muriate — Tartrate of Morphia, 380 — Action of Alkalis upon Salts of Morphia, 380 Action of Nitric Acid upon Morphia, 380. — Action of Heat on Morphia, 381. MECONIC ACID, ... 381 Preparation of Meconic Acid, 38] — Method of testing the presence of Meconic Acid by a Persalt of Iron, 382. — Action of the Persul- phate of Iron on Sulphocyanate of Potassa, 383. NARCOTINE, 383 Method of procuring Narcotine, 383 Properties of Narcotine, 383. — Method of separating Narcotine from Opium, 383. — Method of detecting Opium, 383 Antidotes to Opium, 384. SECT. II— QUINA, CINCHONIA, ... 385 Cautions regarding the purity of Bark, 385. — Substances from which Quina is procured, 385 — Preparation of Quina from the sul- phate, 385 — Experiments with Quina, 386. — Action of Heat on Quina, 386. — Preparation of the Sulphate of Quina, 386-7 — Precau- tions in evaporating the alcoholic solution of Quina, 388. — Method of detecting adulterations of Sulphate of Quina, 389. — Acetate, Oxalate, Gallate, and Tartrate of Quina, 390. — Cinchonia, 390.— Kinic acid, 390 — Method of ascertaining the quality of Bark, 391. j SECT. Ill— STRYCHNIA, .... 391 Preparation of Strychnia from Nux Vomica, j « . 391 XXXVI CONTENTS. CHAP. IV. Page OILS, RESINS, &c. . . 398 Method of preparing Fixed or Expressed Oils, 392 — Stearine and Elaine, 392. — Action of Sulphuric and Nitric Acids on Fixed Oils, 392 Action of heat on Fixed Oils, 393. — Oleum Ammoniatum,393. — Method of forming Soap, 393 — Experiments with Soap, 393-4. — Method of forming Plasters, 394 — Action of Heat on Volatile Oils, 394* Action of the strong Acids on Volatile Oils, 395. — Action of Sulphuric Acid and Chlorate of Potassa on Oil of Tur- pentine, 395. — Action of Muriatic Acid on Oil of Turpentine, 395. — Action of Heat and of Nitric Acid on Resins, 398. CHAP. V. ANIMAL SUBSTANCES, .... 396 SECT. I.— FIBRINE, • .... 396 Method of procuring Fibrine from Elood, 396 — Action of Alcohol upon Fibrine — Adipocire, 396-7. — Action of Nitric Acid on Fibrine, 397. — Action of Acetic Acid on Fibrine, 397. SECT. II.— ALBUMEN, 397 Action of Albumen on Blue Test Paper, 397 — Coagulation of Albu- men, S98 Use of Albumen in clarifying Liquids, 398 — Action of Sulphuric Acid on Albumen, 398-9 — Serosity, 399. SECT. III.— GELATINE, .... 399 Action of Heat on Gelatine, 399. — Action of an Infusion of Galls on Gelatine, 399 — Method of procuring Gelatine, 399. SECT. IV— OSMAZOME 400 Method of procuring Osmazome, 400. SECT. V MISCELLANEOUS EXPEPJMENTS, ILLUS- TRATING THE METHOD OF EXAMINING THE MOST IMPORTANT VARIETIES OF CALCULI, . 400 Preparation of Cholesterine, 400 — Action of Potassa on the Uric Acid Calculus, 401 — Action of Acetic Acid upon the Solution of the Urate of Potassa, 401 — Action of Nitric Acid on Uric Acid, 401. — Action of Heat on a Uric Acid Calculus, 401 — Method of dis- CONTENTS. XXXV11 Page languishing the Urate of Ammonia Calculus, 401 — Oxalate of Lime Calculus, 401. — Action of Heat on this Calculus, 402— Characters of this Calculus on Charcoal before the Blow-pipe, 402 — Method of detecting Oxalic Acid in this Calculus, 402 — Action of Nitric and Muriatic Acid on the Phosphate of Lime Calculus, 402.— Charac- ters of this Calculus before the Blow-pipe, 402 — Action of Potassa on this Calculus, 402. — Method of detecting the presence of Uric Acid in mixed Calculi, 403. — Method of distinguishing the Phos- phate of Ammonia and Magnesia Calculus, 403 — Fusible Calculus, 403 — Cystic Oxide Calculus, 403 — Fibrinous Calculus, 403. CHAP. VI. EXPERIMENTS ILLUSTRATING THE PRINCIPLE ON WHICH THE PRESENT IMPROVED PROCESS FOR THE ULTIMATE ANALYSIS OF VEGETABLE AND ANIMAL SUBSTANCES DEPENDS, . . 404 PART II. CHAP. I. DESCRIPTION OF AN IMPROVED SLIDING SCALE OF CHEMICAL EQUIVALENTS, WITH DIRECTIONS FOR USING IT, AND A COPIOUS TABLE OF CHE- MICAL EQUIVALENTS, . . . .408 Table of Chemical Equivalents, .... 420 Table of Equivalents by Weight and by Volume, . . 442 CHAP. II. MISCELLANEOUS APPARATUS, . . 443 Portable Furnace, 443 — Blast Furnace, 443-4 — -Method of construct- ing a Blast Furnace by Crucibles, 444 — Sand Bath, 445 — Method of fitting up a common Fire-place for Chemical operations, 445-6 — Tongs and Pincers, 447 — Crucibles, Hessian, Black Lead, Wedge- wood's ware, Platina, Cast Iron, 447 — Evaporating vessels, 448. —Florence Flasks— Digesting Flasks, 448 — Method of Prolonging the neck of a Retort in Distillation, by an Adopter, 449 — Conve- nient method of pouring small quantities of liquid at a time into a XXXVI11 CONTENTS. Page vessel, 449 — Sublimation— Alembic, 449— Sublimation by Cruci- bles, 450.— Separator, 450 — Filters, 450 Mode of Washing Pre- cipitates, 451 — Pipettes, 451, — Filtering Frame, 451 Syphon, 4,51-2 — Precipitate Glasses, 452.— Dr. Hope's Gas-holder, 453. —Method of filling it with Gas, 454.— Method of transferring Gas from it, 455 — Balance, and Measure for Liquids, 455 Exhausting Syringe, 455-6 — Professor Leslie's method of evaporating and freezing liquids in vacuo, 456-7. . . . 456-7 CHAP. III. LUTES AND CEMENTS, . . . 457 Lute with Linseed Meal or Pease Meal, 457 Chalk Lute, 457 — Gas Lute, 458. — Wax Lutes — Varnishes, 458. — Lutes with Lime, 459 — With Plaster of Paris, 459.— With Clay and Sand, 459 ■ Willis' Lute, 459. CHAP. IV. OF THE BLOW-PIPE, . . 460 Common Blow-pipe — Dr. Black's — Dr. Wollaston's, 460. — Directions for learning the manner of using it, 461. — Gas Lamp for, 461-2 — ■ Deoxidating Flame, 463. — Oxidating Flame, 463 — Supports for the substance to be examined, 463 — Water Pressure Blow-pipe, 464 — Oxhydrogen Blow-pipe, 465. — Experiments with the Blow -pipe, 466, 467 Fluxes, Borax, Soda, and Salt of Phosphorus, 467 — Table of the principal characters of the Earths and Metallic Oxides before the Blow- pipe, 468. CHAP. V. TUBE APPARATUS, . , . 477 Test Tubes, 477 Stands for, 477. — Manner of Subliming in Tubes, 478.— Method of applying Gases as Tests, 478 — Method of forming Test Tubes. 478. CHAP. VI. ELECTRICITY AND GALVANISM, . . . 179 Electrophorus, 479 Method of forming, 479 — Method of transmit- ting an Electrical spark through Gases, 479-80 — By Volta's Eudi- ometer, 480 — By Dr. Ure's, 480-1 — Method of passing an Elec- tric spark through substances by a Discharger, . . 481 CONTENTS. XXXIX Page GALVANIC BATTERY, . . . 482 Acid Mixture for Charging a Battery, 482. — Manner in which the Electric Current flows when a single pair of plates is used, 482. — In a Compound Galvanic Battery, 483. — Convenient Method of arranging Small Troughs, 483. — Method of passing an Electric Cur- rent through Gunpowder, Gold Leaves, &c, 484 — Method of De- composing Water, 484 — Method of Decomposing Salts by Galvan- ism, 485. CHAP. VII. ACIDIMETRY AND ALKALIMETRY, . 486 Method of ascertaining the Strength of an Acid, 486 — Method of ascertaining the Strength of an Alkali, 487 — Preparation of Subcar- bonate of Potassa for these purposes, 487 — Methods of Measuring the Quantity of Acid Liquor employed, 488-9. CHAP. VIII. METHODS OF ESTIMATING THE SPECIFIC GRAVI- TIES OF SOLIDS, LIQUIDS, AND GASES, . 489 Method of Estimating the Specific Gravity of a Solid heavier than Water, 489, 490-1 — Of a Body lighter than Water, 490 — Pro- , fessor Leslie's Method of Estimating the Specifie Gravity of a Pow- der, 491-2 — Specific Gravity of Liquids, 492 — Of Gases, 493. CHAP. IX. TABLES OF WEIGHTS AND MEASURES, OF THE CORRESPONDENCE BETWEEN FAHRENHEIT'S, REAUMUR'S, AND THE CENTIGRADE THERMO- METER, AND OF FREEZING MIXTURES, . 495 WEIGHTS AND MEASURES, ... 495 CORRESPONDENCE BETWEEN THERMOMETERS, 499 FREEZING MIXTURES, .... 501 INDEX, SOS a 38 "\$ ERRATA. Page 29, line 2i,/or " 1000," read " 1.000." 64, line IS, for " or nitre,'' read " on nitre." . 64, line 31, for " comparisoa," read " comparison." . 255, line 19, for " phosphate," read " phosphuret." 362, line 4, for " 1050," read '« 1071." ■ 467, line 30, for " evaporation, on exposure to heat at the blow-pipe ;" read " evaporation. On exposure to heat at the blow-pipe," EQUIVALENTS BY WEIGHT AND BY VOLUME. HYDROGEN = 1 BY WEIGHT, OR ONE MEASURE (Q) BY VOLUME. 1 Hydrog. = 1 Hydrog. = Equivalents by Weight Oxygen, Hydrogen, Oxide, (Water) . . . . . . Oxygen 8 + Deutoxide, Oxygen 16 + Nitrogen, Atmospheric Air, Oxygen 8+28 Nitrogen = Protoxide, (Nitrous Oxide) . Oxygen 8 -f- 14 Nitrogen = Deutoxide (Nitric Oxide) . . Oxygen 16 + 14 Nitrogen — Hyponitrous Acid, . . . . Oxygen 24 + 14 Nitrogen = Nitrous Acid, Oxygen 32+14 Nitrogen = Nitric Acid, Oxygen 40+14 Nitrogen = Ammonia, Hydrogen 3+14 Nitrogen = Sulphur, Hyposulphurous Acid, . . . Oxygen 8 + 32 Sulphur Sulphurous Acid, Oxygen 16 + 16 Sulphuric Acid, Oxygen 24 + 16 Sulphureted Hydrogen, . . Hydrogen 1 + 16 Bisulphureted Hydrogen, . Hydrogen 1 + 32 Phosphorus, Hydruret, Hydrogen 1 + 12 Phosph. Bihydruret, Hydrogen 2+12 Phosph. Carbon, Carbonic Oxide, Oxygen 8 + 6 Carbon Carbonic Acid, Oxygen 16 -,- 8 Bicarburet of Hydrogen, . . Hydrogen 1 4- 12 Hydruret, (Olefiant Gas) . . Hydrogen 1+6 Bihydruret, Hydrogen 2 + 6 Alcohol, Olefiant Gas 14 + 9 Sulphuric Ether, .... Olefiant Gas 28+9 Cyanogen, Nitrogen 14 + 12 Hydrocyanic Acid, .... Hydrogen 1 + 26 Chlorine, Protoxide, Oxygen 8 + 36 Chlorine = Peroxide, Oxygen 32 + 36 Chlorine = Chloric Acid, Oxygen 40 + 36 Chlorine = Muriatic Acid, Hydrogen 1+36 Chlorine = Chloro-carbonic Acid, . . Carbonic Oxide 14 + 36 Chlorine = Hydrocarburet of Chlorine, . Olefiant Gas 14 + 36 Chlorine = Iodine, Iodic Acid, Oxygen 40 + 124 Iodine = Hydriodic Acid, .... Hydrogen 1 + 124 Iodine = Bromine, Hydrobromic Acid, . . . . Hydrogen 1+75 Bromine = Sulphur = Sulphur = Sulphur = Sulphur = Carbon = Carbon = Carbon = Carbon = Water = Water — Carbon = Cyanog. = 8 or 1 or 9 or 17 or 14 or 36 or 22 or 30 or 38 or 46 or 54 or 17 or 16 or 40 or 32 or 40 or 17 or 33 or 12 or 13 or 14 or 6 or 14 or 22 or 13 or 7 or 8 or 23 or 37 or 26 or 27 or 36 or 44 or 68 or 76 or 37 or 50 or 50 or 124 or 164 or 125 or 75 or 76 or Corresponding Equivalents by Volume. Oxygen □ Oxygen B + □ Hydrog. + □ Hydrog. Oxygen □ . Oxygen a . Oxygen B . Oxygen R — 1 . Oxygen HH . Oxygen P^ Hydrogen I I 1 + Q3 Nitrog. + □ Nitrog. + □ Nitrog. + □ Nitrog. + □ Nitrog. + □ Nitrog. + □ Nitrog. a : ? b = LThl :□ . ? in . ? a . Oxygen □ • Oxygen B • Oxygen Eb Hydrogen □ Hydrogen Q + nil Sulphur + □ Sulphur + □ Sulphur + □ Sulphur : + I I I Sulphur : Hydrogen □ Hydrogen | j 1 + □ Phosph. : + □ Phosph. : . Oxygen o . Oxygen 3 . Hydrogen □ . Hydrogen □ Hydrogen | | | Olefiant Gas E3 Olefiant Gas EB . Nitrogen □ . Hydrogen □ + □ Carbon + B Carbon + FT! Carbon + B Carbon + B Carbon + B Water + B Water + EB Carbon + B Cyanog. . . Oxygen □ . . Oxygen EB . . Oxygen FEb . Hydrogen B Carbonic Oxide B Olefiant Gas B + B Chlorine = + B Chlorine = + B Chlorine: + B Chlorine = + B Chlorine = + B Chlorine = . Oxygen {~T~I 1 + B Iodine = Hydrogen B + B Iodine = Hydrogen B + B Bromine = = □ -? = B . ? "a D B B = □ = □ = B = □ CD O = □= = m ;? = LX1 :B :□ B . ? nn B :CB PRACTICAL CHEMISTRY. PART I. DIVISION I.— SIMPLE SUBSTANCES. Class I. — Simple substances not metallic, and their COMBINATIONS WITH EACH OTHER. CHAP. I.— OXYGEN. Equivalent by weighty 8 ; by volume, □ (half a measure). Specific gravity, 1.111. (barom. 30 ,- temp. 60.) weight of 100 cubic inches 33.888 grains. It is sparingly absorbed by water ; and evolves both light and heat, when sud- denly compressed. 1. Oxygen is an element that is widely distributed over the material world, forming about a fifth part of atmospheric air, eight-ninths of the water of the globe, and existing in large quantities in most earthy substances, and in the products of the vegetable and animal kingdoms. It is procured with fa- cility from a number of its compounds, by exposing them to heat, when it assumes the form of a transparent and colour- less gas, pre-eminently distinguished by its power of support- ing combustion and respiration. It can unite with all the ele- 2 PREPARATION OF OXYGEN GAS mentary substances with which we are acquainted, and with many of them in several different proportions. When it com- bines with the non-metallic bodies, the resulting compounds have usually acid properties ; and with the different classes of metals, it forms alcalies, earths, and the common metallic oxides. 2. The substances from which oxygen gas is usually pre- pared, are, the black oxide of manganese, the red oxide of lead, the red oxide of mercury, and the nitrate and chlorate of potash. The last of these affords the purest oxygen gas ; but the first is commonly employed, as it is procured at a mo- derate price, and affords oxygen sufficiently pure for the pur- poses to which it is usually applied. 3. When a large quantity of oxygen gas is required, the black oxide of manganese is exposed to a red heat in an iron bottle, placed in a furnace or open fire. The most convenient method of conducting the process, is to connect with a bottle (A) contain- ing the manganese, as represented in Fig. 1., a bent tube e, (made of a gun barrel or gas pipe, and previously ac- curately fitted to the neck of the bottle by grinding,) and then to put it in the furnace, so that it shall rest upon a piece of brick or stone, placed imme- diately above the grate, and from one to two inches thick. The connection between the iron bottle and the bent tube is made perfectly air-tight, by drawing the finger round the end of it, with a little clay, before it is introduced, and giving it a slight blow afterwards with a hammer. When the apparatus is proper- ly adjusted, the furnace is filled with red hot cinders till they reach the neck of the bottle, and the cover is put on, consist- ing of a flattened cylinder of baked fire clay, bound round .with an iron hoop, and with an opening at one of the sides for the passage of the iron tube. The door (d) of the ash pit is at the same time opened, that the air may enter freely. 4. The manganese must not be reduced to powder, as it is then very apt to be thrown from the iron bottle into the bent PROM THE PEROXIDE OF MANGANESE. 3 tube, but merely broken into pieces of such a size, as may al- low it to be easily introduced. The gun barrel (e) is kept cool, by wrapping it round with a piece of wet cloth on which a little water is poured, whenever it begins to be dry. 5. The furnace represented in the above figure, was in- vented by Dr. Black, and is extremely well adapted for a great variety of chemical operations. It consists of a case of strong sheet iron, lined with some very refractory clay (6 6), the luting increasing gradually in thickness from the top of the furnace to the roof of the ash pit. The grate is fixed to the iron plate, which supports the lute, and forms the top of the ash-pit, which has a door for the free admission of air, and a series of apertures, with proper plugs to regulate the quantity of air admitted when the door is shut, and a steady and de- terminate heat required. The smoke is carried away by the pipe/, and may be conveyed to any distance, by connecting several other pipes of the same kind with it. The last piece may be fixed into an opening in the wall communicating with the vent, or made to pass a few feet up the chimney over the common fire, if the usual conveniences of a laboratory cannot be procured. When more fuel is required, it may be intro- Figs. 2. 3. duced, after removing the lid #, at the top of the r~^ furnace, without displacing any part of the appa- ratus. Figs. 2. and 3. represent the form of the poker and shovel constantly required in using a furnace of this construction. 6. The first portions of gas that are disengaged must be rejected, consisting principally of atmospheric air and carbonic acid, the latter arising from the decomposition of some carbonate of lime, with which the oxide of manganese is often contaminated, and which parts with its carbonic acid when exposed to heat. 6. The quality of the gas must be tried from time to time, at the commencement of the process. This is usually done by Fig. 4. attaching a flexible leaden or tin tube, to the bent iron f| tube, connected with the bottle, as is seen in Fig. 1., the gas issuing from it being collected in a small glass jar A full of water, inverted in a bason or pneumatic trough * also filled with water. The thumb is placed on the 4 PISEPAKATION OF OXYGEN GAS. mouth of this jar, when full, (whicli need not be above an inch' or two long,) and a small wax taper, suspended by a wire, (Fig. 4.) (or a splinter of wood,) is introduced after the flame has been blown out, but while the wick is still red ; if it is im- mediately extinguished, this arises from the presence of carbo- nic acid ; but if it burns brighter, and is re-kindled into a flame, then, the oxygen may be collected ; for though it may be still mixed with a little carbonic acid, it will be found sufficiently pure for ordinary purposes. If no glass jar, so small as the one I have described, should be at hand, it may be collected in a larger one, and removed on a small plate or tin tray, before it is inverted. Occasionally I have seen an inflammable gas disengaged at the commencement of the process, probably from the pre- sence of some earth, containing a little woody fibre, as it had a great resemblance to the gas that arises from wood when it is exposed to heat in close vessels. The quantity of carbonic acid disengaged varies according to the quality of the manganese. The oxide is seldom in such a state of purity as to afford nothing but oxygen gas from the commencement of the process. 7- To collect the gas, large vessels capable of containing several cubic feet of gas, and termed gas-holders, are usually employed. These vessels are made of sheet copper, japanned Fig. 5. both externally andinternally, or some- times the bottom alone is made of cop- per and the sides and top of tin. The annexed figure represents Mr. PepysV gas-holder, the most convenient form of this apparatus hitherto contrived. A is the body of the gas-holder, in- tended to contain the gas ; B a trough supported on three pillars, resting on A ; c a flexible tube conveying gas through an aperture that permits the water to escape as it enters ; b a stop-cock connected with a flex- ible tube through which the gas may be propelled after it has been collected ; e another stop-cock connected with a tube TEl'lVs GASOMETER. .5 open at both ends and passing between A and B, through which the gas may be made to pass (when b is shut) into a jar full of water placed in the trough B. A tube (a) open at both ends, passes through one of the pillars supporting B, and is continued to the bottom of A ; d d a glass tube open at both ends, and cemented into the upper and lower part of A, to indicate the quantity of gas inside, the fluid in the tube beirjg always at the same level with the fluid in it. When the gas-holder is to be used, the aperture at c is closed by a plug made to screw upon it ; and water being poured into B it passes down through a into the body of the gas-holder, the atmospheric air being forced through b (which is also opened) as the water rises in A. All the stop-cocks are shut when the gas-holder is full of water, and the plug which closes the aperture at c being unscrewed, the tube which conveys the gas may be introduced, which will rise through the water as represented in the figure, while the latter flows out in a con- tinued stream as long as any gas enters ; great care must be taken not to open any of the stop-cocks while the plug at c is unscrewed, as the water would then be forced out with great violence by the pressure of the atmosphere, and the gas-hold- er filled with atmospheric air in a few seconds. When the gas-holder is full, the tube c is withdrawn, and the plug screwed on ; the trough b is then filled with water, and on opening the stop-cock in the tube a, the water descends and presses upon the gas ; but none escapes unless the stop- cocks at b or a are opened, through either of which it may be propelled by opening the one and shutting the other. Instead of a flexible leaden or tin tube, the gas is frequent- Fig. 6. _ ly conveyed from the gun-barrel to the : -o=cz g asome ter by two pieces of brass tube, Jilfif"" joined together by a moveable circular joint, ""^ as is seen in Fig. 6. Such is the most convenient method of preparing and col- lecting a large quantity of this gas, when a suitable appa- ratus can be obtained. On a smaller scale a wrought iron bottle, capable of containing one or two pounds of the man- ganese may be employed, and a bent gun barrel adapted to it. PREPARATION OF OXYGEN GAS the one extremity being ground accurately to the neck of the bottle, and the other made to dip under the shelf of the pneumatic trough without any intervening leaden tube. The bottle is placed in the open fire and surrounded with coals, so as to be exposed to a red heat, and the gas may be collected in glass jars, or preserved for use in common green glass bottles, with ground stoppers, which are to be well dried, and the finger drawn round them with a little gas lute before they are introduced. 8. Oxygen gas can be procured from the peroxide of man- ganese at a much lower temperature if previously mixed, with rather more than its own weight of sulphuric acid, every 44 parts of the oxide requiring 49 of the acid. Fig. 7. 9. For this purpose fill a tubulated retort about a third full of sulphuric acid, pouring it carefully through a glass funnel, the manganese in fine powder is then poured through another funnel, (Fig. 7-)> previously warmed to render it perfectly dry, which prevents it from adhering to the neck ; the acid is shak- en from time to time before the whole of the manganese is introduced, that it may not gather into lumps. Should the manganese be put in first, it is not so easily mixed afterwards with the acid, and if it should lie dry on any part of the bot- tom of the retort, which often is the case when they are in- troduced in this order, even after they have been well shaken together, the retort is extremely apt to be broken. These remarks apply to all cases where a powder and a liquid are exposed to heat in a glass vessel, whatever form it may have, and the more heavy and insoluble the powder is, the greater is the necessity of attending to them. 1 0. The retort is to be placed on a ring supported by a brass or iron stand, (Fig 8.) and fixed in its place by turn- ing a screw when its height has been pro- FJIOM THE PEKOXIDE OF MANGANESE. 7 perly adjusted. If the retort is large, and the ring at a con- siderable distance from the stem of the retort stand, weights must be put upon it to keep it steady ; the most convenient for this purpose are cylindrical pieces of lead, from half an inch to an inch and a half thick, having the same diameter as the bottom of the retort stand, over which they are placed ; a piece of lead being cut out from the centre to the circumfe- rence, so as to allow them to be put on or taken off without interfering with any other part of the apparatus. 11. The neck of the retort is introduced below the top of the small stool, which is made of wood, and has lead run into holes bored through it, to prevent it from floating in the wa- ter in the pneumatic trough. The upper part is hollowed out, to collect all the gas that is disengaged, which passes through an aperture in the centre to the pneumatic jar, placed immediately above it. The stool is made exactly on a level with the shelf in the pneumatic trough, and may be taken out, or moved up and down in either direction, as may be required. 12. These troughs are made of wood, copper or tin, the first kind being oil-painted, and the latter japanned. They are made of various shapes and sizes, and when not accompa- nied with a stool, holes are made in the shelf to allow gas to be more easily collected. The one I have found most conve- nient is made of wood and bound together at the corners by plates of brass. It is twenty-four inches long, twelve broad, and seven and a half or eight inches deep. The shelf is as long as the trough, and fixed to one of the sides about an inch and a half or two inches from the top ; its breadth is four and a half inches ; the stool, the top of which is on a le- vel with the shelf, is seven inches long and four and a half broad ; a small spout is fixed at the upper part of one of the ends of the trough to convey away any excess of water when the trough becomes too full from the gas displacing the water in the pneumatic jars. 13. h h h are jars filled with water in which the gas may be collected as it rises through the aperture in the stool ; when full they may be placed on the shelf till required, or removed F 'g- 9 - on a japanned tin tray or small plate (Fig. 9) This ^Z^% is done by merely placing the tray below the jar un- B CHAUFFERS. der water and removing it with the small quantity of water it may contain, which prevents the escape of the gas. The pneumatic jars required for collecting the gases are made of dif- ferent sizes ; where a small quantity of materials is employed, they may be from eight inches in length and two and a half in diameter, to four inches in length and one and a half in dia- meter. 14, The retort is then to be heated by placing a chauffer below it filled with red hot cinders (which burn better if mixed with a few pieces of charcoal) free from any smoking pieces of coal ; it affords a more equal and powerful heat than the less diffusive flame of a lamp. The small chauffers, as they are usually made, are seldom properly constructed. The grating ought to consist of stout pieces of iron wire, of a suit- able thickness, riveted to an iron ring supported on feet, and not of a thin and flat piece of sheet iron with a few holes cut in the centre, as is generally the case, much too small to sup- ply a sufficient quantity of air ; a space of about an inch at least should also intervene between the grating and the bot- tom of the chauffer in order to enable it to burn freely. The chauffer which I find most convenient for general purposes is six inches and a half deep and six in diameter ; the grating is placed one inch and a half above the bottom, which is sup- Tig. 10. ported about the same distance from the ground by feet riveted to it. 15. A chimney is of great use in kindling a chauffer quickly, and in raising a higher tem- perature than the chauffer would otherwise af- afford ; for a chauffer of the size just described it may be from two and a half to three or four feet long, and the pipe about three inches in diameter. Fig. 10. shows the chauffer with the chimney on it. Chauf- fers have usually wooden handles, which often Fig. II. prove very inconvenient; they are much better without them, and with a pair of strong iron pincers (Fig 11.) they may be moved as conveni- ently from place to place as when they are provided with a handle. A pair of tin pincers of another form (Fig. 12.) is required for adjusting the fire, and h ilHA'UEEEUS. f) Fig^l2. long iron rod bent at the end for filling the chauffer with cinders from the fire. Black lead crucibles are often converted into chauffers, (Fig. 13.) by bor- ing holes through them with a file and putting in a grating made of wire, and earthen-ware vessels are frequently made for this purpose alone ; all of them are easily broken, however, and the beginner will almost invariably find well made chauffers of sheet iron much more useful. A bright tin plate must be placed between the chauffer and the table to protect it from the heat, and another between the trough and the chauffer for the same purpose ; a rough tin plate that has lost all its lustre will not do, as it absorbs in- stead of reflecting all the rays of heat that fall upon it. 16. The gas disengaged by the action of sulphuric acid on the black oxide of manganese, must be tried as already describ- ed, (7-) If it should be mixed with any carbonate of lime, part of the sulphuric acid unites with the lime, and carbonic acid is at first disengaged. It is more convenient occasionally, to wash the manganese after it has been reduced to powder with dilute muriatic acid (one part of acid to eighteen of water) ; the acid combining with the lime and forming muriate of lime, which is completely removed by a little fresh water, while the carbo- nic acid is disengaged. The powder is dried by spreading it out on a plate and exposing it to the air or to a gentle heat before the fire. 17. Retorts made of the light green bottle glass are the best for this process, as they are not so apt to be softened by the temperature necessary for the expulsion of the oxygen as those made of flint glass, the large quantity of the oxide of lead which the latter contains rendering it much more fusible than any of the other kinds of glass. Care must be taken while conducting either of these processes, to keep the fire as steady and equal as possible. The fire in the furnace is regulated by the quantity of air admitted through the plug holes. When the door is shut, the tube connected with the bottle must never be left in water after the gas has ceased to come, or when the fire is allowed to decline, otherwise water would be 6 10 PREPAUATION OF OXYGEN GAS forced through it into the iron bottles by the pressure of the atmosphere, the heated gas still remaining there diminishing in volume as it cools. In the same manner the tubulated re- tort must be taken from the pneumatic trough when no more gas is disengaged, to prevent a similar accident, or the stop- per may be removed, which will have the same effect. If the retort has been exposed to a high temperature, and the mass inside appears quite hard and solid, the chauffer must not be suddenly withdrawn, as the cold air playing upon the external surface of the glass, while the internal surface is kept hot by the mass of heated matter within, is very liable to break it. 18. When the retort is cold, water is poured in and it is allowed to stand for some hours before the sulphate is washed out, and, in this manner, by repeated washings the dense mass is at last removed. If a larger quantity of sulphuric acid is employed, and the heat not continued till a dry mass is ob- tained, it is removed much more easily from the retort. 19- To understand the theory of the preparation of oxygen gas by either of these methods, it must be kept in view that there are three oxides of manganese, and the following is per- haps the most probable view of their atomic constitution : Manganese. Oxygen. Protoxide 28 + 8 = 36 Peroxide 28 + 16 = 44 Protoxide. Peroxide. Deutoxidc 36 + 44 = 80 When the oxygen gas is prepared from the peroxide by ex- posing it to a red heat, every 88 parts (two equivalents) give 8 parts of oxygen, and 80 parts of the deutoxide remain ; but if it is mixed with sulphuric acid and exposed to a more gentle heat, then every 44 parts (one equivalent) give 8 parts of oxygen, and there remains 36 parts of the protoxide united with 40 (one equivalent) of dry sulphuric acid. 20. As every cubic inch of oxygen gas at a mean tempera- ture and pressure weighs one-third of a grain within a very trifling fraction, and as every 88 parts of the peroxide of man- FROM THE PEROXIDE OF LEAD. 11 ganese by weight yield 8 of oxygen at a red heat, or every 11 grains give 1 grain, we have only to multiply by 3 the weight of the oxygen expressed in grains which any quantity of the peroxide can afford (1-llth of its own weight) and the quotient gives the number of cubic inches which it will occupy in the gaseous state. Gas is never prepared in quantity from the peroxide of manganese by means of sulphuric acid, though it is a process frequently performed for experimental illustra- tion. 21. The next substance mentioned from which oxygen gas can be procured is the red oxide of lead, which parts with a portion of its oxygen when exposed to heat in the same man- ner as the peroxide of manganese, either with or without sul- phuric acid. There are three oxides of lead, the composition of which may be represented as follows : Lead. Oxygen. Protoxide 104 + 8 = 112 Peroxide 104 + 16 = 120 Protoxide. Peroxide. Deutoxide . . . . . . 112 + 120 = 232 It is the deutoxide that is usually known by the name of red lead, and when exposed to a red heat, every 232 parts give off 8 parts of oxygen, and 224 (two equivalents) of the protoxide remain. A less degree of heat is sufficient to drive off the same quantity of oxygen when it is mixed with about half its weight of sulphuric acid, (See 9,) the protoxide com- bining with the sulphuric acid and forming sulphate of lead, Fig- i*. A piece of a gun barrel closed at one end, (Fig. 14.) may be used for preparing a small quantity of oxygen from this oxide, by heating it in a furnace or open fire, the gas being conveyed to a pneumatic trough by a brass or copper tube soldered into a perforated iron stopper, which is ground accurately to the open end of the gun barrel. 22. Tied lead is not often employed for the preparation of 12 PREPARATION OF OXYGEN GAS oxygen, as the remaining protoxide is apt to be melted, and then it is removed with difficulty from the vessel in which it has been heated. It is frequently adulterated with chalk or sulphate of lime ; the former may be detected by muriatic acid which immediately occasions a brisk effervescence, the latter by heating a small portion on charcoal with the blowpipe, the oxide of lead being instantly reduced while any sulphate that may be present remains. 23. Oxygen gas may be procured with great facility from the peroxide or red oxide of mercury, every 216 parts consist- ing of 200 of mercury (one equivalent,) and 16 (two equiva- lents) of oxygen. In this case the whole of the oxygen is ex- pelled, on exposing the oxide to heat ; and as the mercury is at the same time volatilized, none of the apparatus must be made of brass, copper, lead or any other metallic substance which might be acted on by this metal. 24. To prepare oxygen gas from this substance, it may be put into a small green glass retort, and heat applied by means of a good chauffer or powerful lamp, the beak of the retort being placed below the shelf of the pneumatic trough ; a retort made of flint glass is generally softened by the heat necessary for the expulsion of the oxygen, and cannot therefore be used. Occasionally an iron retort is employed, the body of the retort being made of a piece of gun barrel, and the neck of a bent iron tube, less in diameter and accurately fitted to the neck of the first piece by grinding ; a glass tube is fixed to the end of the iron one, in order that we may perceive if the water should begin to go back into the retort after the point has been placed below the shelf or stool in the pneumatic trough, when it must be immediately withdrawn. The form of this apparatus is re- Fig. 15. presented in the annexed figure, the heat being applied by a chauffer into which red hot cinders and charcoal are put after the retort has been properly adjusted. ! 25. If a considerable quantity of the pe- roxide of mercury has been used, the mercury that is distilled over ought to be kept, as it is extremely pure. 26. The nitrate of potash is another substance that is fre- quently employed for the preparation of oxygen when it is not IT ROM NITRATE OF POTASH. 1J wanted particularly pure. It may be exposed to a red heat in any of the kinds of apparatus previously described, with the exception of the glass retorts. Nitre consists of nitric acid and potash, and when exposed to heat it is in the first place melt- ed, and afterwards oxygen gas is evolved, which arises from the decomposition of the nitric acid : the latter consists of oxy- gen and nitrogen, and, if the heat is withdrawn after it has been continued for a considerable time, every 102 parts of nitre (consisting of 54 parts of nitric acid and 48 of potash) give 8 parts of oxygen, and there remain 94 parts of the nitrite of potash, (composed of 48 of nitrous acid and 48 of potash,) the nitric acid in the nitre being converted into nitrous acid by los- ing this quantity of oxygen. Thus before decomposition we have Nitric Acid 54+48 Potash=102 Nitrate of Potash and after decomposition, Nitrous Acid 46 + 48 Potash=94 Nitrite of Potash, Oxygen evolved, 8 102 If the heat is continued after this quantity of oxygen has been obtained, the whole of the nitrous acid is decomposed, and a large quantity of mixed gases is obtained, consisting of oxygen, nitrogen, nitrous and nitric oxides. 27- When nitre is used for the preparation of oxygen, the vessel in which it is contained should never be filled more than half full, for when oxygen escapes from the melted nitre, the whole is thrown into a state of ebullition ; and, if there were a larger quantity in the vessel, part of it would be thrown into the tube which conveys away the gas, and being immediately consolidated there (as it is at a much lower temperature than the melted nitre) would not only prevent the farther escape of gas, but might give rise to serious accidents from the accumu- lation of gas pent up in the interior of the vessel, and exerting a strong expansive force. 14 PREPAKATION OF OXYGEN GAS 28. Oxygen gas is always prepared from the cHorate of potash when it is required in a high state of purity, and is obtained from this substance by exposing it to heat in an iron or green glass retort, and collecting it in the usual manner. A small green glass flask, with a long stem, is occasionally employed, the stem being bent near the ball of the flask by the blowpipe, after the chlorate has been introduced. An iron or gun metal retort may be employed instead of the tube retort. (Fig. 15.) It should be made of two pieces, how- ever, the one being secured to the other. It is supported by a retort stand, the body of the retort being allowed to rest on red hot cinders in a chauffer, and surrounded with more if ne- cessary, using the tin pincers for this purpose. (Fig. 12.) 29- As the chlorate of potash is melted by the heat before it parts with any oxygen, the precautions mentioned with res- pect to nitre in 27 must be carefully attended to. 30. Chlorate of potash, containing more than a third of its weight of oxygen, all of which is expelled by heat, affords a much larger quantity of this gas than any of the preceding substances. Every 124 parts (one equivalent) consist of 76 parts (one equivalent) of chloric acid, and 48 parts (one -equi- valent) of potash. The following table shows the composition of these two substances, and the quantity of oxygen evolved when 124 parts of the chlorate are exposed to heat. 76 Chloric Acid = Oxygen 40 + 36 Chlorine. 48 Potash = Oxygen 8 + 40 Potassium. 124 Chlor. of Potash Oxygen 48 76 Chloride of Pm. All the oxygen (48 parts) comes away both from the chlo- ric acid and potash, the chlorine of the acid remaining in com- bination with the potassium of the potash, and forming 76 parts of the chloride of potassium. The latter remains in the retort, and may be removed by water, which speedily dissolves it. 31. There are several other substances of a similar nature FROM CHLORATE OF POTASH. 15 from which oxygen gas may be procured, but they are seldom employed for this purpose. Small quantities may be obtained also when the green leaves of vegetables are immersed in an inverted jar full of water, and placed in the sunshine. 32. Oxygen gas, in its pure state, is never applied to any practical purpose on the large scale ; it is used constantly, however, in the laboratory for a number of important and in- teresting experiments ; it will accordingly save much time and trouble on commencing a series of experiments, if a large quantity is prepared in the manner described in 3, &c. 33. Flexible tubes are required for conducting the gas from the gasholder to the pneumatic trough, in which the vessel is placed that is to be filled. These should not be made of lead or tin, as they are never required to stand a high temperature, but merely for the transmission of the gas after it has been prepared. They are in general made of a coil of wire sur- rounded with several folds of varnished silk, one end being fitted to the stop-cock of the gasometer, and the other placed in the pneumatic trough, or connected with a second flexible tube if the first should not be sufficiently long.* 34. In effecting combinations between oxygen and other substances, the compounds usually employed are atmospheric air, water, and acids. Bodies in general require to be heated before they combine with oxygen. Some, however, as potas- sium, abstract it rapidly both from air and water at natural temperatures. 35. By the conjoined action of air and moisture, many substances are readily oxidated; iron, for example, which soon passes into rust, and the sulphate of iron or green vitriol of commerce is prepared from the native sulphuret of iron in this manner, the sulphur being converted into sulphuric acid while the iron is oxidated. 36. A number of the metals attract oxygen very slowly from water when it is perfectly pure ; if some acid, however, be added, as the sulphuric or muriatic, then the oxidation " These flexible tubes may be procured at the principal opticians and phi- losophical instrument makers in town. 16 OXID'ATfOW goes on briskly, while the hydrogen, (the other element of which water is composed) is disengaged, and it is in this manner that hydrogen gas is usually procured. 37- When the acids containing oxygen are poured in a con- centrated form on substances that have a great affinity for this element, as metals and inflammable bodies, oxygen is rapidly taken from them, especially if the action of the decomposing agent be assisted by heat. Thus, mercury poured into nitric acid is speedily oxidated, and if boiled in sulphuric acid the same thing takes place. In both cases, however, the oxide formed by the decomposition of one portion of the acid unites with another portion that has not been decomposed, and the resulting pro- ducts are a nitrate and a sulphate of the oxide of mercury. 38. When oxygen is to be withdrawn from any substance which does not part with it on exposure to heat, it is usually mixed with charcoal, which has a much greater affinity for oxygen if it is a high temperature, than most other substances. It is in this manner that most of the common metallic oxides are deoxidated and their bases procured in the metallic form ; the carbon combining with the oxygen and being carried off in the form of carbonic acid gas. CHAP. II. HYDROGEN. Equivalent by weight 1 ; by volume □ (one measure.) Specific gravity 0.0694. Weight of 1 00 cubic inches 2.118 grains. It refracts light powerfully ', and is but sparingly absorbed by water, which dissolves about a % '5th part of its volume of this gas. 39. Hydrogen is another element that is extensively distri- buted over the face of nature, forming a ninth part of the water of the globe, and existing in almost all the products of the animal and vegetable kingdom. It is always obtained in the form of a transparent and colourless gas when not com- PREPARATION OF HYDROGEN GAS. 17 bined with any other substance, and is distinguished by its great levity and inflammability. 40. Hydrogen gas is always prepared for experimental pur- poses by decomposing water, a compound of hydrogen and oxygen ; the oxygen being withdrawn by the action of some substance which has a great affinity for it. Iron and zinc are usually employed for this purpose, and the most convenient method of conducting the process is to put the iron or zinc into a glass retort supported on a stand in the manner repre- sented in Fig. 8, or into a glass flask of the form shown Fi S- 16. in the annexed figure, (Fig. 16,) a cork be- ing fitted to the neck, through which a bent glass or leaden tube passes, intended to con- vey the gas as it is produced into a gasometer, or to dip under the shelf of the pneumatic trough. When the apparatus is properly adjusted, sulphuric acid, diluted with from five to nine parts of water, is poured over the metal through the tubulure at the side, and as hydrogen gas is immediately evolved, the stopper must be introduced and the gas collected when the atmospheric air has been expelled. Instead of the glass tube passing through a cork placed in the neck of the flask, it is often made thicker at the part where it is connected with the flask, and ground to it accurately in the same manner as a stopper. The flask is supported on a I'ig. 17. Fig. 18. r i n g made of tin or copper, (Fig. 17,) or on a square block of wood with a hole cut in the centre, as is seen in Fig. 18. 41. The vessel in which the hydrogen gas is prepared ought never to be filled more than one-third or one-half full, as the gas is frequently disengaged so rapidly as to cause the liquid to boil over. The rapidity with which the gas comes over de- pends not only on the quantity of the materials employed, but also on the state of division of the metal, and the extent of surface which it presents to the water and the acid. 42. As hydrogen gas detonates violently when mixed with atmospheric air or oxygen gas in certain proportions, a lighted match must never be applied to it as it issues from any appa- ratus containing either of these gases ; and this must be care- c 18 PREPARATION OF HYDROGEN GAS. fully attended to in preparing it by the process just described, serious accidents frequently taking place from not attending to this precaution, the flame being communicated through the tube to the mixed gases in the interior of the apparatus, upon which an explosion takes place. The best method of ascertain- ing when the atmospheric air has been expelled is to collect a small jar of the gas over a pneumatic trough and remove it on a plate or tray, keeping the mouth still downwards, and to ap- ply a lighted match to the gas as the tray is withdrawn, still keeping the jar in the same position. If it is mixed with at- mospheric air it will burn rapidly, but if it has been completely expelled the hydrogen will burn slowly, and only where it comes in contact with the air. 43. When iron is employed for the preparation of hydrogen gas, it may be used in the form of turnings or filings ; small nails are occasionally substituted for them, or iron wire cut into pieces from one to three inches long. Zinc is easily re- duced to fragments by melting it in a crucible or iron ladle over the fire, and pouring it from a height into a bason of water. 44. Another method of preparing hydrogen is by passing watery vapour over iron wire or turnings heated to redness. They must be put into a gun-barrel open at both ends, which is made to traverse a furnace, a bent tube being connected with one end and terminating under the shelf of the pneumatic trough, and a retort containing water attached to the other. Instead of a furnace, a chauffer may be employed when the process is conducted on a small scale, in the manner shown Fig. 19. i n Fig. 19. A chimney will f ~ j assist materially in keeping up ^?=o czz i > -*§ t j ie p r0 p er temperature ; and • oo ooo " \_J the chauffer may be raised to any height by supporting it on bricks. When the gun-barrel is at a red heat, the water in the re- tort is made to boil, and the steam passing over the iron at this high temperature is immediately decomposed, the hydro- gen escaping in the gaseous state and passing through the bent tube, while the oxygen combines with the iron. GASOMETEK. 19 45. Instead of connecting a retort containing water with one of the ends of the gun-barrel, a more convenient method of Fig. 20. proceeding is to fix another bent tube to it in the manner seen in Fig. 20, to which a tin funnel with a stop- cock fixed to it is soldered. Water is poured into the funnel, and when the gun barrel is at a red heat, the stop-cock is opened and immediately shut again ; a small portion of the water is thus allowed to run down into the gun-barrel, and being converted into vapour by the heat, is immediately forced over the iron shavings and de- composed as before. This is repeated until a sufficient quan- tity of gas is obtained ; the water must be allowed to pass into the tube only in small quantities at a time, otherwise the tem- perature of the turnings will be so much reduced that the wa- tery vapour will pass over them without being decomposed. 46. In using this apparatus it ought not to be exposed to a very high temperature, as a red heat is quite sufficient for the purpose, and all kinds of iron tubes are soon destroyed when exposed to the action of the air at a high temperature ; the gun-barrel need not be left till the fire has burnt away, but withdrawn from the furnace when the bent tube which conveys the gas away has been removed. 47. Hydrogen gas is occasionally collected in a gasometer of a different construction from the gas-holder described in 7. It consists of a vessel of tinned iron, japanned, and supported on feet, and filled with water, in which another vessel made of the same substance is placed in an inverted position, as is seen in the annexed figure, 21. To di- minish the quantity of water requir- ed for this apparatus, the interior of the outer vessel is filled up in a great measure by an inner vessel B B, from the top of which a tube passes to the bottom and divides into two branches which open on opposite sides of the outer vessel, as is seen at e and /, when the gasometer is to be filled a tube conveying the gas is fixed at /, and the bell-shaped vessel C, 20 PREPARATION OF HYDROGEN GAS. rises up as it enters, being suspended by cords passing over pulleys, and counterpoised by weights. Instead of connecting the tube which conveys the gas di- rectly with the gasometer, it is sometimes more convenient to Fig. 22. n introduce it under a funnel (Fig. 22) placed in a bason and screwed on at /, the gas rising in the funnel and passing into the gasometer, while the water in the bason prevents it from escaping. The rod g, attached to the bell-shaped vessel being accurately graduated, the quantity of gas it contains is found out by examining the point at which it is cut by the bar through which it slides. The gas in the interior may be expelled by shutting the stop-cock at f, and opening the stop-cock e, the counter- poising weights being at the same time removed, the bell- shaped vessel then descending by its own weight, forces the gas out at e. 48. A very convenient apparatus for preparing a small quantity of hydrogen whenever it may be required, is a bottle Fig. 23. (Fig. 23) with three tubulures, a long tube funnel being fixed into one, and descend- ing till it comes within an inch and a half of the bottom, and a bent tube adapted to one of the others. Fragments of zinc and water are put in by the middle tubulure, till the fluid shall have risen about half an inch above the lower end of the tube funnel, the cork or stop- per is then put in, and on pouring sulphuric acid down the long tube funnel, it mixes with the water, hy- drogen gas is immediately disengaged, and may be conveyed in any direction by the bent tube fixed in the tubulure. The diluted acid is forced up the long tube funnel to a height proportional to the depth that the bent tube is inserted in the pneumatic trough ; if the bent tube were sunk to a considera- ble depth in water, and the funnel made very short, then the gas would have to overcome a greater resistance in rising through this depth of water than in forcing the liquid in the bottle up to the top of the tube funnel, it would accordingly PREPARATION OF HYDROGEN GAS. 21 continue to flow over till the liquid in the bottle should fall below the lower part of this tube, and allow all the gas to es- cape. Several square blocks of wood of various sizes will be found necessary in adjusting the apparatus to a proper height. 49- If small quantities of sulphuric acid are added at a time, a constant stream of hydrogen gas may be made to issue from the bent tube ; and it is in this manner that hydrogen gas is usually prepared, when it is required to transmit it over any substance exposed to a red heat, in a gun barrel or por- celain tube. 50. The sulphuric acid ought previously to be diluted with an equal bulk of water, and allowed to cool before it is em- ployed, the tube being apt to be broken, when this precaution is not adopted, from the high temperature excited when the strong acid combines with the water. 51. The quantity of sulphuric acid required for the prepa- ration of hydrogen gas, depends upon the nature of the metal employed. When zinc is used, 40 parts of real sulphuric acid (which are contained in 49 of the common liquid acid,) are required for every 34 of this metal, and one of hydrogen gas is disengaged, 9 parts of water being decomposed, consist- ing of 8 parts of oxygen and 1 of hydrogen. Thus, before decomposition, we have Zinc, 34 parts -+- 9 water + 40 sulphuric acid = 83 parts. And after decomposition, , , , n . ( Sulphuric acid, 40 "I Sulphate ol zinc, < „ ., „ . ' „ f O o „„,.,. r I Oxide of zinc, 42 h= 83 parts. Hydrogen gas disengaged, 1 * These are the proportions in which the materials act upon one another, the 8 of oxygen (one equivalent) contained in the 9 parts of water, combining with the 34 of zinc, and form- ing 42 parts of the oxide of zinc, which unites with the sul- phuric acid, while the hydrogen of the water is disengaged. But the sulphuric acid must be diluted with more water than is decomposed during the preparation of the gas, otherwise little or no action will take place, and the sulphate of zinc 22 HYDROGEN GAS. produced must have a sufficient quantity of water to retain it in solution, to prevent it from being thrown down in the form of a powder, and impeding the farther action of the metal upon the liquid ; and as every 49 parts of the common sul- phuric acid contain 9 of water, we may use by weight, 7 parts of zinc, 10 of sulphuric acid, and 60 of water. 52. When iron is used, the same quantity of sulphuric acid and water may be mixed with 6 parts of this metal ; the theory of the process is precisely similar to what has just been stated with respect to the preparation of hydrogen by zinc, the iron being oxidated and uniting with the sulphuric acid, while the hydrogen arising from the decomposition of the water, which affords oxygen to the iron, is disengaged ; every 28 parts of iron (one equivalent) acting upon 9 parts of water, and 40 of sulphuric acid, in the same manner as 34 of zinc. In the other method of preparing hydrogen gas, by trans- mitting watery vapour over iron turnings at a red heat, every 28 parts of iron decompose 9 of water, forming 36 of the ox- ide of iron, which remains in the tube, 1 part of hydrogen be- ing disengaged. Accordingly, in calculating the quantity of hydrogen gas that is disengaged by the action of a given weight of zinc or iron, we may allow 1 grain of gas, for every 34 grains of zinc, (or 28 of iron) employed ; and as every 100 cubic inches of hydrogen gas weigh 2.118 grains, and 47 cubic inches about 1 grain, if we multiply the weight of the hydrogen that ought to be disengaged (expressed in grains) by 47, we have the vo- lume which it will occupy in the gaseous state, expressed in cubic inches. 53. The gas obtained by these different processes is not abso- lutely pure, having a disagreeable odour when disengaged dur- ing the solution of iron in diluted sulphuric acid, and contain- ing minute traces of sulphureted hydrogen when zinc is used. The odour is attributed to the presence of a portion of oil de- rived either from impurities in the iron turnings, or formed by the union of part of the carbon, which common iron always contains, with a little hydrogen. The zinc of commerce al- ways contains a portion of sulphur, which explains the for- HYDROGEN CAS. 23 mation of the small portion of sulphureted hydrogen, and a part of the zinc itself appears also to be combined with the gas. By passing it through a solution of potash or lime water, all impurities may in general be removed, with the ex- ception of a small portion of carbureted hydrogen, which has also been detected in hydrogen gas prepared by iron. 54. Distilled zinc is preferred for the preparation of hydro- gen gas, when it is required in a very high state of purity for experimental researches. 55. Hydrogen gas burns with a pale watery looking flame, which affords a very feeble light. To observe the character of the flame, apply a lighted match to it as it issues from a gas-holder, or to a jar containing the gas, so that it shall burn with the mouth downwards, the hydrogen will be slow- ly consumed, when it comes in contact with the atmospheric air. 56. If a lighted candle be tied to a piece of iron wire bent at right angles, and introduced into a jar of hydrogen gas held in the same manner as before, the hydrogen will be inflamed and continue to burn at the mouth of the jar, while the candle will be extinguished in the interior of the jar where it is sur- rounded by the hydrogen, proving evidently that the pre- sence of air or oxygen in some form or other is necessary for its combustion, the gas burning only where it comes in contact with the air, and the hydrogen from its great levity, occupy- ing the upper part of the jar till it is all consumed. 57. Inflame another jar of hydrogen gas with the mouth turned upwards, taking care not to remove the cover till the light has been brought over the top of the jar ; it will burn much more rapidly than before, rising quickly in the air, and mixing speedily with as much as may be required for its com- bustion. If the cover be removed before the light is held over it, the gas will be found to have escaped in a very short time, and the jar filled with common air. 58. In all these experiments the hydrogen unites with the oxygen of the air, forming water, and a corresponding propor- tion of nitrogen gas is disengaged. 59. Mix one measure of hydrogen gas with half its vo= 24 HYDROGEN GAS. lurae of oxygen gas, and fill a strong glass bottle with the mixture, cork it under water, and after wrapping it round with a towel, apply a lighted candle, or piece of paper, to the mouth of the bottle on withdrawing the cork. A quick and loud explosion will immediately take place, the oxygen and hydrogen combining as before, and forming watery vapour which is immediately condensed. In performing this experi- ment, a strong bottle made on purpose should be employed, capable of containing from three to six ounces of water, as it is seldom that a flint glass bottle, of the usual strength, will stand the explosion. The reason why the gases are mixed in the above proportions will be seen on referring to the table of equivalents by weight and by measure. Hydrogen. Oxygen. Equivalents by weight 1 + 8=9 water. Corresponding equivalents □ -+• a = D watery vapour. Here we find that one equivalent of hydrogen by weight (=1) corresponds with one measure or volume of hydrogen gas, and that one equivalent of oxygen by weight (= 8) cor- responds with half a measure, oxygen gas being sixteen times heavier than hydrogen gas ; and by their combination one vo- lume of watery vapour is produced, a condensation taking place equal to the volume of the oxygen employed. If an excess of either gas be present, it remains after the detonation. 60. Atmospheric air containing one-fifth of its volume of oxygen gas, every measure of hydrogen gas will re- quire two and a-half measures of air for its combustion ; the detonation that ensues is very feeble compared with what takes place when the hydrogen is mixed in the pro- per proportion with oxygen gas. A small excess of atmos- pheric air causes a louder detonation than when the exact quantity required for the combustion of the hydrogen is em- ployed. By varying the proportion of air or oxygen gas mix- ed with the hydrogen, before the light is applied, and holding the jar or detonating bottle containing the mixture in different positions, the rapidity of the combustion, and the appearance of the flame is considerably varied. HYDROGEN GAS. 25 A piece of paper folded into a match will be found more convenient than a candle in firing the hydrogen in these dif- ferent experiments. A bent iron wire, heated to bright red- ness, is sometimes used, but the paper match, or a small splin- ter of wood is better. 61. Oxygen and hydrogen do not combine so readily when they are expanded by diminishing the pressure to which they are exposed; if the pressure is increased, they unite with greater facility, and when mixed in the proper proportions, and suddenly compressed, they immediately combine, a loud detonation taking place ; if part of the vessel is made of glass, it is broken and a brilliant light is seen. This ex- periment was made by Biot, but it is not easily performed, and always dangerous ; the heat evolved during the compres- sion has generally been considered as the cause of the combi- nation. 62. A mixture of oxygen and hydrogen may be made to combine slowly and without any detonation, by introducing a piece of coal at a dull red heat, — if it is at a full red heat an explosion always takes place. 63. When a stream of hydrogen gas (issuing from a gaso- meter or any other source) is directed upon a piece of spongy platina (metallic platina in a very minute state of division) it immediately becomes incandescent if atmospheric air, or oxygen gas, is at the same time present, and the hydrogen is almost instantly inflamed. The spongy platina may be sup- ported in a small cage of platina wire ; this is not necessary, however, for though the effect is seen to greater advantage in this manner, the incandescence of the platina, and the inflam- mation of the gas take place, whenever they come into con- tact (along with air) whatever may be the nature of the sub- stance on which it rests. If the platina should be damp, it must be carefully dried by exposing it to heat in a crucible, or in a small plate of metal held over a spirit lamp. 64. This singular property of platina was discovered by Professor Doebereiner, and a lamp for procuring an instan- taneous light, constructed on this principle is well known by 26 doebereineb's lamp. Fig. 24. the name of Doebereiner's Lamp. (Fig. 24.) It consists of an ingenious contrivance of Gay Lussac's, by which a jet of hydrogen can be obtained instantaneously by merely opening a stop-cock and a brass cup fixed below it to contain the platina. The hy- drogen gas is produced by the action of a cylinder of zinc or diluted sulphuric acid placed in the lowermost vessel re- presented in the annexed figure, a small wine glass of strong sulphuric being mixed with as much water as may be required to fill this part of the apparatus nearly full. The upper part consists of a globe nearly as capacious as the first, but terminating in an open tube which is fitted accurately to the neck of the other by grinding. The cylinder of zinc is placed round this tube, supported about a quarter or half an inch above its inferior extremity by a cork that also fits closely to the tube. When the cylinder is introduced into the lower vessel, hydrogen gas being immediately evolved, and not finding any exit when the upper one is properly adjusted, it collects at the top of the lower vessel and presses upon the surface of the liquid below, which is consequently forced through the tube and collects above. If the stop-cock connected with the lower vessel be now opened, the liquid that has been forced into the upper one will descend, and force out the hydrogen gas by the small nozzle fixed so as to direct it upon the platina, and com- ing again into contact with the metallic zinc, more hydrogen will be produced, until at last the zinc is dissolved or all the sulphuric acid converted into sulphate of zinc. The stopper in the upper part of this apparatus must have a groove cut in the side to allow the free ingress or egress of the air, and the cup containing the platina must be supported by a wire sliding through a piece of brass attached to the stop-cock, so as to allow it to be brought nearer or removed farther away from the aperture by which the hydrogen es- capes. When more sulphuric acid is required, it is necessary to dilute it previously with twice its bulk of water, and allow HYDROGEN GAS. 27 it to cool ; for if strong sulphuric acid is poured into the upper vessel, after withdrawing the stopper, the heat produced when it comes in contact with the liquid, frequently causes the glass to break. 65. When neither a gas-holder nor an apparatus such as Doebereiner's lamp are at hand, the effect of the gas upon the spongy platina may be seen by filling a bladder with hydro- gen, and compressing it afterwards, so as to force out the gas in a slender stream. For this purpose the bladder must be provided with a stop-cock, and a brass nozzle fitted to it, which is to be fixed on when the bladder is full. A pneuma- tic jar, also provided with a stop-cock nrnst be procured, and a connector, as it is termed, or small tube, open at both ends, by which the bladder and the jar can be connected together Fig. 25. by the stop-cocks, as represented in the annexed Figure (25.) Both stop-cocks being now shut, and the jar placed on the shelf of the pneu- matic trough, and filled with water, hydrogen gas may be introduced, and by depressing it in the pneumatic trough, and opening both stop- cocks, the gas is forced from the jar into the empty bladder by the pressure of the water. 66. Oxygen and hydrogen gases, when mixed in the pro- per proportions, are inflamed by the spongy platina as rapidly as by flame, or an iron rod at a white heat. If a bladder is filled with a mixture of the two gases, and a piece of spongy platina introduced, it immediately explodes with great vio- lence, and the bladder is blown to pieces. The best method of performing this experiment is to fit a large cork to the neck of the bladder, with a hole in the centre ; through this the spongy platina is introduced, supported in a small wire cage, attached to an iron wire which is fixed to another cork that fits the aperture in the first. When the bladder has been filled with the mixture, a common cork is immediately put into the first, to prevent the escape of the gas ; and on removing it to a safe place, where it may be supported on a retort sand, this cork is taken out, and the other, with the platina attached to it, immediately introduced, a glove being 28 HYDROGEN GAS. put on the hand in which it is held, in case it should explode as soon as it is put in. 67- When the gases are mixed in different proportions, or when the oxygen and hydrogen, though present in the exact proportions in which they combine with each other, are mixed with other gases, the detonation does not take place, or, at least, only after some time has elapsed; the platina always causes them, however, to combine, and the heat generated during the combination is so great, that the platina frequently becomes incandescent, though the mixture is not inflamed. The spongy platina retains this property even when mixed with clay, and made into small balls. They are made with different proportions of platina, and are more or less active, according as the quantity of platina is increased or diminish- ed. The method of preparing the spongy platina, &c. will be described under platina. 68. As oxygen and hydrogen always combine in the pro- portion of half a measure (o) of the former to a whole mea- sure (□) of the latter, forming watery vapour, which is im- mediately condensed, if the temperature is not raised to 212°, it is obvious that we can estimate the proportion of oxygen or hydrogen in mixed gases, by adding one or other of these to the mixture, and noting the degree of condensation that at- tends the combination. For example, if we wish to ascertain the purity of hydrogen gas, prepared by any of the preceding processes, it may be mixed with its own volume of oxygen gas in a small jar or tube, over a mercurial trough, and a ball of spongy platina introduced, previously mixed with clay, however, to prevent any detonation. If a condensation takes place equal to the bulk of the hydrogen, and half of the oxygen employed, then we are sure that the hydrogen gas was pure, for oxygen and hydrogen combine in these propor- tions ; if, however, it does not take place to this extent, then on noting the amount, and taking two-thirds of it, we ascer- tain the exact quantity of pure hydrogen contained in what we employed, every measure of hydrogen combining with half its volume of oxygen. 69- In the same manner, the purity of oxygen gas may be WATER. 29 ascertained by mixing an excess of pure hydrogen with a given quantity of the oxygen gas, and proceeding as before. If the diminution of volume in the mixed gases is equal to three times the bulk of the oxygen employed, it is evident the oxygen must have been pure, for it combines with twice its bulk of hydrogen ; if, however, the condensation does not proceed so far, then one-third of the amount to which it does take place, indicates the exact quantity of pure oxygen in the portion employed. 70. Mixtures of hydrogen and oxygen gases may be in- flamed also by means of electricity. 71. Hydrogen gas produces an intense degree of heat dur- ing its combustion, and if mixed with oxygen gas in the pro- per proportion, and made to issue from a small orifice, we have at our command a more powerful heat than can be produced in any other way. It is on this principle that the oxy-hydrogen blowpipe is constructed, which will be described when we come to treat of the blowpipe. Sect. I. — Water. Equivalent by weight, 9 ; by volume □ (one measure.) Specific gravity, 1000. One cubic inch weighs 252.525 grains ,• it is 828 times heavier than atmosphere air, and when converted into vapour at 212°, it expands to nearly 1700 times the volume it occupies when at its greatest den- sity. The specific gravity of steam (air being 1) is 0.625. 72. When a mixture of half a measure of oxygen gas (□,) with one measure of hydrogen (□,) is inflamed in a dry glass vessel, both gases entirely disappear, and the interior surface of the vessel is found bedewed with moisture, formed by the condensation of the watery vapour that results from the com- bination. To see this distinctly, the dry gases must be mix- ed in a proper detonating bottle (59) over a mercurial trough ; or a stream of hydrogen gas may be inflamed as it is made to issue from a gasometer through a flexible tube, to which a 30 WATER. brass nozzle, with a small aperture, has been fitted, and in- troduced into a larger glass flask or jar, taking care not to bring the flame too near the glass. 73. If a mixture of oxygen and hydrogen gases were made at the temperature of 212, and the apparatus not allowed to cool after the detonation, one measure of steam would be found to have been produced, a condensation having accom- panied the combination equal to the volume of oxygen em- ployed. 74. There is perhaps no agent of more importance in a practical point of view than water, whether we consider its mechanical or chemical properties, and the infinite variety of purposes to which it may be applied. It not only enters into combination with many substances, forming a well defined series of compounds termed hydrates, but is also the medium by means of which many important combinations and decom- positions are effected, as in the decomposition of compound salts, where it communicates that fluidity without which they do not in general act on each other. From the extensive range of the affinities of its elements, and the facility with which they are separated by peculiar arrangements, it is con- stantly giving rise to new combinations ; while, by others, of a different nature, these are subverted, and the oxygen and hydrogen again unite to form water. No department of chemistry is certainly more interesting than the study of the different changes of which this fluid is susceptible, and the combinations arising from its decomposition, and attending its formation, which accompany the action of a great number of substances upon it, and upon one another. This is well ex- emplified in the changes that take place in the chlorides, io- dides, bromides, and cyanides and water, when one of the stronger acids is added to them, and also in the preparation of nitrous oxide, protoxide of chlorine, chloric acid, sulphureted hydrogen, and many other substances, where water is either formed or decomposed ; and by the researches of modern che- mistry, especially those more immediately connected with the examination of the chemical equivalents of the different ele- ments and their compounds, these actions have been traced, DISTILLED WATER. 31 with a degree of a minuteness and precision which has been attended with the happiest results ; and instead of being con- sidered as complex phenomena, the method in which the dif- ferent particles arrange themselves, may now be studied with facility and satisfaction by the beginner. 75. Pure water being constantly required for experimental purposes, it is necessary to state the characters by which it may be known, and the method of obtaining it, as this fluid is always contaminated with some foreign matter in its native state, according to the channel through which it may have flowed, and the particles of mineral, vegetable, or animal mat- ter with which it may have come in contact. 76. The purest water that can be obtained without subject- ing it to artificial operations, is procured by melting snow, or collecting rain as it falls at a distance from town, or in any place where it is not liable to be vitiated by the state of the atmosphere. Even this, however, is not perfectly pure, for it contains a portion of air which may be disengaged by boiling it, or placing it under the exhausted receiver of an air-pump. 77- It w iH be found most convenient in general to prepare pure water by distillation, the only method indeed by which it can be completely separated from the saline matter which it usually holds in solution. The most usual form of apparatus Fig. 26. f or t n j s p Ur pose is a small boiler of /f\& tinned iron, (Fig. 26,) 6 or 7 inches fUL V^-fj p^I^ ^ in diameter, and about 7 or 8 inches H—- -7 ni^%7 deep. It is filled half full of water by the funnel (a) which is soldered ^f in it, and descends till it comes if within an inch of the bottom of the \ boiler ; the steam is conveyed by _J a tin tube (b) to another tube coiled in a spiral form in a vessel of water, termed the refrigeratory, where it is condensed, and may be collected in a bottle as it drops from the other extremity of this tube. 78. The water must be allowed to boil for a short time be- fore it is collected, to expel any gaseous matter which it may 32 DISTILLED WATER. contain, as well as to remove any foreign matter that may be adhering to the sides of the tube ; after three-fourths of the water has been distilled over, the remainder had better be thrown away. When the level of the water in the interior of the boiler falls below the lower part of the funnel, the steam then issues through the tube of the funnel, and informs us of the extent to which the evaporation has been carried. More water may then be poured in by the funnel, or the boiler may be removed, and a fresh charge introduced after the remainder has been set aside. 79- It is seldom necessary to distil water in glass vessels, except perhaps in very delicate experimental investigations, or where an apparatus such as has been described is not at hand. Water may then be introduced into a tubulated retort with a long neck, and condensed in a thin glass receiver or florence flask, over which a stream of cold water is made to pass. Fi § 27 - Fig 27 represents a very convenient appa- ratus for this purpose. Small quantities of hot water being introduced at a time by the glass tube, which is ground 'accurately to the tubu- lure of the retort, while its beak passes into a long and thin glass tube terminating in a receiver. The condensation is ef- fected almost entirely in this tube by a stream of cold water flowing from a funnel, the throat of which is obstructed with a cork, at the side of which a small groove has been cut to allow the water to pass through in sufficient quantity. A piece of linen or cotton cloth is wrapped round the tube after it has been moistened, that the whole of it may be kept cold ; care being taken that the excess of water is conducted away from the tube (an inch or two before it enters the receiver,) by some tow or a piece of cloth in the manner shown in the figure. The beak of the retort may be introduced two or three inches into the tube, but no lute must be applied, nor is it necessary that they should fit accurately to each other. DISTILLED WATER. 33 The boiler may be heated by placing it on the open fire, and the retort by a chauffer after it has been supported by a retort stand. The funnel from which the water drops may be sup- ported by a retort stand : instead of a cork being introduced into the neck, a filter is often put into the funnel which al- lows the water to pass slowly through it and keep the glass tube cool. 80. Pure water is perfectly transparent and colourless, and is remarkably limpid, though it has not that fine sparkling ap- pearance which water impregnated with gaseous matter always presents when it is poured from one vessel to another. To the taste it is insipid and unpleasant. It is not so heavy as water containing saline matter in solution, mixes easily with soap, and gives no precipitate with a solution of soap in alcohol, ni- trate of silver, muriate of barytes or acetate of lead. It also moistens other substances more easily than water which has any foreign matter in solution. 81. As water readily absorbs a number of gaseous sub- stances, especially when it has been boiled to expel any air that may have been combined with it, distilled water must be kept in glass bottles with ground stoppers, otherwise it will soon be contaminated by the different gases that are constantly floating about in an experimental room. The following table by Dr. Henry shows the quantity of several of the gases which 100 cubic inches of water can absorb at the usual temperature and pressure. Dalton. Sulphureted Hydrogen 100 cubic inches. Carbonic Acid 100 Nitrous Oxide 100 Olefiant Gas 12.5 Oxygen ; 3-7 Carbonic Oxide . 1 .56 Nitrogen , 1 .56 Hydrogen . 1.56 . 82. Distilled water should always be employed in preparing solutions, for experimental purposes, and when these are to be used as re-agents, attention to this circumstance is quite in- Saussure. 3 inches. 253 do. 106 do. 76 do. 12.3 do. 6.5 do. 62 do. 4.1 do. 4.6 34 WATER. dispensable, as the presence of the smallest portion of foreign matter might lead to an erroneous conclusion. 83. When water is decomposed by a metallic sulphuret or chloride, the hydrogen almost invariably goes to the sulphur or chlorine, forming sulphuretted hydrogen or muriatic acid, while the metal takes the oxygen and is converted into an oxide which remains in combination with the acid. The same action ensues when a compound of bromine, iodine, or cyano- gen, and a metal decomposes water, and when there are two equivalents of any of these substances united with one of the metal, as in the bicyanide of mercury, then two equivalents of water are decomposed, the two of hydrogen in the water going to the two of cyanogen in the bicyanide, and forming two equivalents of hydrocyanic or prussic acid, while the corres- ponding equivalents of oxygen combine with the mercury and convert it into a deutoxide. 84. Again, when any compound of an acid, such as the muriatic, (composed of chlorine and hydrogen,) or prussic, (consisting of cyanogen and hydrogen,) with a metallic oxide is decomposed, the oxygen of the oxide unites with the hy- drogen of the acid, and water is reproduced. Nothing can be of more importance than acquiring a clear and precise idea of the nature of these changes, as they are constantly taking place in a great number of combinations and decompositions. 85. From the large quantity of caloric which becomes la- tent when water is converted into steam, (as much as would raise its temperature 967 degrees, according to Dr. Ure,) and is evolved again when it is condensed, it is often em- ployed to communicate heat, as in the distillation of alcohol or ether, in drying precipitates, &c. In distilling liquids, according to this plan, a pipe from a still in which steam is produced, is coiled round in another still containing the li- quid to be heated, and by placing the still where the steam is condensed, on a higher or lower level than the first still, it may be made either to return to the first still, where it would be again converted into steam, or collected and used as dis- tilled water. vv DEUTOXIDE OF HYDROGEN. 35 86. For drying precipitates, a square F te- 28 - tin box (Fig. 28.) will be found very /r) convenient, which may be heated by a ^//^W'C-^ pipe conveying steam from the small still seen in Fig. 26. It may be made about twelve or sixteen inches long, from eight to twelve broad, and about six inches deep. The con- densed steam is conveyed away by a spout, placed at the bot- tom, and opposite to the end where the steam is introduced, and the box has a slight inclination, so that it may be all car- ried off. In addition to a flat surface for laying on any sub- stance that is to be speedily dried, (as a filter with a precipi- tate, see the figure,) it is convenient to have one or two fun- nel-shaped cavities of different sizes passing through it, to hold filters containing liquids that must be kept warm during filtration. These are represented by the dotted lines, and are open both above and below, like a common funnel. Sect. II — Deutoxide of Hydrogen, or Oxygenated Water. Equivalent byw eight, 17; Spec. grav. 1.452. 87- The minute details of the process for preparing the deutoxide or peroxide of hydrogen, as it is occasionally term- ed, are too long to be inserted in an elementary work ; I shall, therefore, merely mention the method by which Then- ard obtained it, and refer to Vols. xiii. and xiv. of the An- nals of Philosophy, and to the original memoirs in Vols. viii. ix. and x. of the Annales de Chimie et Physique, where a full detail of all the circumstances to be attended to in pre- paring this compound will be found. 88. Muriatic acid is diluted with about ten times its bulk of water in a glass vessel which is surrounded with ice or snow, and the deutoxide of barium, reduced to fine powder, is added, in small quantities at a time, as long as any is dis- 36 DEUTOXIDE OF HYDROGEN. solved. Sulphuric acid is then added to the solution which decomposes the peroxide of barium, disengaging a portion of oxygen, and combining with the protoxide (barytes,) that re- mains, forming the insoluble sulphate of barytes which is precipitated. The oxygen, set at liberty at the same time, combines with a portion of the water, converting it into deut- oxide of hydrogen, which remains along with the rest of the water and the muriatic acid. This is repeated till the water shall have been combined with from twenty to thirty times its bulk of oxygen gas, the muriatic acid added to the water at the commencement of the process, serving for the solution of the successive portions of the deutoxide of barium. Sulphate of silver is employed to remove the muriatic acid, the silver being withdrawn by the muriatic acid in the form of an inso- luble compound, while the sulphuric acid remains in its place, which is again separated by adding barytes in powder. 89. The deutoxide of hydrogen, prepared in this manner, is still diluted with a considerable proportion of water, and it is removed by placing the liquid in the exhausted receiver of an air pump, with another vessel containing strong sulphuric acid, when the water evaporates and is condensed by the acid : care must be taken, however, not to continue the evaporation after the specific gravity of the residue has increased to 1.452, as then the deutoxide begins to evaporate also, and mixes with the water and sulphuric acid. 90. The deutoxide of hydrogen has not been applied to any use. It is distinguished by the great facility with which it is decomposed by most of the metals and many of the me- tallic oxides, being converted into water and oxygen gas ; with some of the metallic oxides, especially the oxides of silver, lead, gold, mercury, and platina, the decomposition takes place the moment they are brought into contact with it, great heat is at the same time produced, and the oxides are reduced to the metallic state, if they belong to the class of metals whose ox- ides are decomposed by exposure to heat without the addition of any carbonaceous matter. 91. It is decomposed also by heat, being resolved into water and oxygen gas, at the temperature of 59 of Fab.., and PREPARATION OE NITROGEN GAS. 37 when exposed suddenly to a temperature of 212, the oxygen is disengaged with explosive violence. When combined with water, or with the stronger acids, it does not part so readily with its oxygen. CHAP. III. NITROGEN. Equivalent by weight, 14; by volume Q (one measure.) Specific gravity, .9722. Weight of 100 cubic inches, 29.625 grains. Water absorbs this gas still more sparing* ly than oxygen ; 100 cubic inches of water taking up about one and a half of nitrogen. 92. Nitrogen, when uncombined, exists always in the gaseous form, and is distinguished principally by its negative properties, being transparent and colourless, insipid, and in- odorous, incombustible and incapable of supporting combus- tion. It forms four-fifths of atmospheric air ; exists in almost all the products of the animal kingdom, and enters into a number of important combinations. With oxygen it forms atmospheric air, nitrous and nitric oxides, hyponitrous, nitrous and nitric acids ; with hydrogen it forms ammonia ; with car- bon cyanogen, and it can combine also with sulphur, chlorine and iodine. 93. The best method of preparing nitrogen gas is by burn- ing phosphorus in atmospheric air, included in a jar or bottle over water. For this purpose a tin float, or a brass stand with a copper cup fixed to the top as represented in the an- Fig. 29. nexed figure (29), or any thing that will support a small metallic cup with the phosphorus, is placed on the shelf of a pneumatic trough, and covered with a bell jar, the moment the phosphorus is kindled by touching it with a small iron wire previously heated ; a large quantity of white fumes are pro- duced arising from the phosphorus combining with the oxygen of the air, and being convert- 38 PREPARATION OF NITROGEN GAS. ed into phosphoric acid, which is diffused through the ni- trogen ; these are speedily absorbed by the water, and on transferring the residual gas from one jar to another several times under water, nitrogen gas is obtained sufficiently pure for common experiments, though it still contains a mi- nute portion of carbonic acid (which is always found in at- mospheric air) and a little phosphorus in solution, both of which may be removed, if required, by agitation with a solution of caustic potash. 94. Eight or ten grains of phosphorus may be taken for every 100 cubic inches of atmospheric air, and if a cup fixed to a stand is employed for supporting the phosphorus, it must be raised to a proper height above the water, which rises after- wards in the jar to supply the place of the oxygen which has been converted into phosphoric acid. 95. It is seldom that any other substance is employed for the preparation of nitrogen. It may be obtained, however, by agitating atmospheric air with a solution of the sulphureted hydro- sulphuret of potash or of lime in a bottle ; the oxygen being speedily absorbed while the nitrogen remains. The finger is drawn round the stopper of the bottle with gas lute, before it is introduced, in order that it may be withdrawn more easily afterwards. The stopper must be taken out under water, a portion of which immediately rushes in to supply the place of the oxygen that has been absorbed, and the resi- dual gas may then be transferred to a pneumatic jar. 96. A mixture of one part of sulphur with two of iron filings speedily attracts oxygen from atmospheric air, if made into a paste with water, and exposed to a gentle heat before the fire for two or three minutes, or until it begins to grow warm and become of a black colour. It is then put into a tin cup, and ajar placed over it on the shelf of the pneumatic trough. The quantity of sulphuret of iron used must not be so great as to prevent the tin cup from floating in the water as it ascends to supply the place of the oxygen absorbed. In this process the sidphur and the iron both attract oxygen from the air, and if it were exposed for a long time to the free ac- tion of atmospheric air and properly moistened, it would be NITJtOUEN GAS. 39 eventually converted into sulphate of iron, the sulphuric acid and oxide of iron formed by the absorption of the oxygen combining together as they are produced. 97- In all these processes four parts by measure of nitrogen gas are obtained from every five parts of atmospheric air, when the oxygen has been completely separated. Nitrogen gas may be obtained also by exposing muscular fibre to the action of nitric acid diluted with two or three times its bulk of water. When prepared in this manner, it is always contami- nated with a little carbonic acid gas, which may be removed by agitation with a solution of caustic potash or lime water, the carbonic acid combining with the potash or lime, and forming a carbonate. None of these latter processes, how- ever, are resorted to for the preparation of nitrogen gas, ex- cept for experimental illustration, as it is procured with much more facility by burning phosphorus in air. 98= To show that this gas cannot support combustion, any substance may be introduced into it in a state of combustion, when it will be immediately extinguished. If two jars are taken, one full of oxygen, and the other full of nitrogen gas, a suspended candle (Fig. 4, p. 3.) introduced into the nitrogen, is immediately extinguished, but if it shall have been previously allowed to burn till the wick is red, it will be re- kindled on transferring it to the jar of oxygen gas, and again extinguished in the nitrogen ; this may be repeated several successive times with the same portions of gas. 99. If two measures of nitrogen gas are mixed with half a measure of oxygen, a mixture is obtained which cannot be distinguished from atmospheric air. 100. Nitrogen gas is occasionally employed to fill bottles or retorts instead of atmospheric air, when it is necessary that the gaseous fluid should have no action on the materials after- wards to be introduced. 101. The following table shows the constitution and the chemical equivalents of the compounds which nitrogen forms with oxygen and hydrogen by weight and by volume, where these have been ascertained, and it will be found useful to keep this table in view while studying these compounds. 40 PREPARATION OF NITROUS OXIDE. Nitrogen. Oxygen. Nitrogen. Oxygen. Atmospheric air = 28 + 8 = 36 or [JJ\ + o = \T~H Protox. of nitrog.= 14+ 8 = 22 or D + Deutox. of nitrog.= 14 + 16 = 30 or □ Hyponitrous acid= 14 + 24 = 38 or D Nitrous acid . = 14 + 32 = 46 or □ Nitric acid . = 14 + 40 = 54 or □ Nitrogen. Hydrogen. Ammonia . = 14 + 3 = 17 or D Sect. I. — Protoxide of Nitrogen, or Nitrous Oxide, Equivalent by weight, 22 ; by volume, Q (one measure.) Specific gravity, 1.527. Weight of 100 cubic inches, 46,596 grains. Water absorbs more than half its bulk of this gas. 102. Nitrous oxide is obtained by exposing the nitrate of ammonia to heat in a glass retort, when it is resolved into water and nitrous oxide gas, which may be collected in a ga- someter or in jars over a pneumatic trough. To prepare the nitrate of ammonia (composed of nitric acid and ammonia) car- bonate of ammonia in powder is added to nitric acid, pre- viously diluted with its own bulk of water till the acid is neu- tralized, which is known by the liquid not affecting an infusion of blue vegetable colouring matter, which would be turned green by any excess of carbonate of ammonia and red by any excess of acid.* The nitric acid combines with the ammonia forming nitrate of ammonia which remains in solution, and the carbonic acid is disengaged with effervescence. The neu- tralization is effected more speedily by heating diluted nitric acid in a flask or in an evaporating bason (supported on a retort stand) by a chauffer, if strong nitric is added to the car- • Paper soaked in an infusion or decoction of red cabbage, dried and then cut into small pieces, will be found very convenient in ascertaining when the neutralization is completed. PREPARATION OF NITROUS OXIDE. 41 bonate of ammonia, the nitrate may be obtained as before, but a large quantity of offensive fumes are disengaged. 103. When the solution of nitrate of ammonia has been prepared, it is introduced into a glass retort, of which it should not fill more than a half, and heat is applied till the water is entirely expelled. This is known by introducing the beak of Fig. 30. the retort into a small cup with cold water, as is shown in Fig. 30 ; if the whole of the water has been expelled, gas will rise through the water, but if nothing is com- ing over but steam, it will be condensed, and the cold water will probably rise in the neck of the retort ; a very small quantity, therefore, must be put into the cup, to allow atmospheric air to enter by the beak of the retort after the water shall have risen a certain length in the neck, otherwise it will pass into the retort, which will be immediately filled with water and probably broken. This also shows the necessity of not introducing the beak of the retort into a pneumatic trough or into a gas-holder, till the gas begins to be disengaged abundantly by the decomposition of the nitrate, which does not take place till all the water has been driven off. In expelling the last portions of water, great attention must be paid to the management of the heat, as the li- quid is then extremely apt to boil over. An iron or tin plate is extremely useful in this stage of the process, which may be interposed between the chauffer and the retort, when the li- quid appears as if it were going to boil over, and withdrawn when it falls again in the retort. In this manner the last por- tion of water are expelled more speedily, and full advantage ta- ken of as high a temperature as can be applied with safety. The first portions of gas that come away are often impure, es- pecially if the heat to which the nitrate is exposed is too great, and part of the salt also is then volatilized without being decomposed, and collects occasionally in a solid mass in the beak of the retort. When the water is completely expelled the heat should be moderated, so that the fused nitrate shall be kept in a state of gentle ebullition ; the heat may be con- tinued till the whole of the nitrate is decomposed. The re- 42 NITROUS OXIDE. tort should have a long neck that it may be conveniently in- troduced into the gas-holder, and the beak should not be made so thick as usual, that it may not be so liable to break when it is put into the cold water. 104. Every 54 parts or one equivalent of real nitric acid (contained in *]2 of the common liquid nitric acid) combine with 17 of ammonia, and give 71 of dry nitrate of ammonia, which is resolved by the heat into 27 parts of water and 44 of nitrous oxide, and as a 100 cubic inches of this gas weigh very nearly 46^ grains, 71 grains of the nitrate will give 95 cubic inches of this gas, (= 44 grains.) The following diagram shows the changes that are produced by the decomposition. Nitrate of , Ammonia= ( 71 grains. Nitric Acid 54. Amm. 17. V Ox. 8. - Ox. 8. Ox. 8. Ox. 8. Ox. 8. Nit. 14. Nit. 14. Hyd. i; Hyd. 1. Hyd. 1. 71 • 22 Protox. of Nitrog. /-/ 22 Protox. of Nitrog, 9 Water. 9 Water. 9 Water. 71 The first part of the table (to the left) represents the ele- mentary composition of the 54 parts of nitric acid and the 17 of ammonia existing in 71 parts of the dry nitrate, and the other shows the new arrangement which these enter into, and the compounds produced. The three proportions of hydrogen in the ammonia combine with three of oxygen from the nitric acid, and the remaining proportions of oxygen come away with the nitrogen both of the nitric acid and the ammonia in the form of nitrous oxide. 105. Nitrous oxide supports combustion more brilliantly than atmospheric air, containing half its bulk of oxygen in a condensed state, whereas air only contains a fifth part of its INHALATION OF NITROUS OXIDE. 43 volume of oxygen. It revives the iiame of a candle which has been blown out, if the wick is still red ; phosphorous burns in it with great splendour, and sulphur with a rose-coloured flame; these however, and most other combustible substances must be introduced into the gas in a state of active inflammation, as a higher temperature is required to support their combustion in this gas than in oxygen or atmospheric air. 106. Nitrous oxide may be detonated with hydrogen by mixing equal measures of that gas in a proper bottle, and ap- plying a lighted match ; the hydrogen combines with the oxy- gen of the oxide and nitrogen gas remains. 107. The characteristic property of this gas is the singular action which it has upon the animal economy, a high degree of excitement being produced after a few inspirations, which is accompanied by a rich and genial glow that pervades the whole frame, and the most pleasing and thrilling sensations, particularly in the chest, and a rapid succession of vivid ideas, with increased power and disposition to muscular exertion, which it is impossible for any one to restrain who has breathed freely of the gas. Out of nearly a hundred gentlemen attend- ing my classes for practical chemistry, who have taken it within the last eighteen months, only one disliked it, com- plaining of a disagreeable sensation which pervaded the whole body after he had begun to inspire it, but which passed away in a minute or two, without leaving any bad effects or any dis- agreeable impression. In another case, the individual fainted after six or seven inspirations, but recovered with a kind of start in a few seconds, without subsequently experiencing any kind of depression. On four or five it had no apparent effect ; of these, some did not take the gas properly, but one of them, a South American, took a larger doze three times in succession than all the rest, and breathed with every precau- tion, and after exhausting the kings as completely as possible of atmospheric air, but still without being in the slightest de- gree affected by it, a circumstance that attracted our attention more particularly, as it had been lately affirmed in France that the effects which are usually ascribed to it may be traced 44 INHALATION OF NITROUS OXIDE. more to the imagination than to any peculiarity in the gas itself. The rest were all affected by it in a manner which removed all doubts of the power of this singular gas, even in those who were previously impressed with the idea of the ac- curacy of the statements made abroad. 108. Occasionally it acted so powerfully on the system, that seven people were required to restrain a single individual while under its influence, and prevent him injuring himself or others ; no person, therefore, should breathe freely of it by himself. It is curious, that the excitation which it pro- duces passes away as speedily as it is induced, in no case that I have seen did it ever last longer than thirty-five seconds, though it often leaves a cheerfulness and gaiety of disposition for hours afterwards ; nor is this state of excitation accompa- nied by any subsequent depression, as is the case with other stimuli, except when it has given rise to violent muscular ex- ertion, when it is always accompanied by a corresponding de- gree of exhaustion. 109- Different individuals require different quantities of this gas in order to be affected by it, and by varying the quantity, the same person generally experiences all the varie- ties of effect which it produces, from the most gentle and agreeable stimulus, to the most furious excitement, when he will show a degree of muscular power of which it might scarce- ly be supposed the human frame was susceptible. In some cases, though the individual cannot restrain himself, he is per- fectly conscious of his own actions and of all that is going on around him, in others nothing is recollected from the time a slight giddiness is felt till its effects pass away, when the in- dividual often recovers with a wild start, as if previously un- conscious of the place where he is, and those by whom he is surrounded. I am strongly disposed to believe from the ex- pression of the countenance, and from individuals sometimes attempting to knock their heads on the ground, that very severe pain is sometimes felt where large doses have been taken, although, on questioning them afterwards they have invariably expressed the reverse, and affirmed that their sen^ sations were highly pleasurable. INHALATION OF NITROUS OXIDE. 45 Those who had never previously heard of the nature of this gas, nor were aware at the time of the effect it was likely to produce, frequently stopped suddenly and exclaimed, " That they felt as if they were lighter than the atmosphere, and were going upwards,'" a sensation very generally experi- enced by all who breathe this gas. 110. To breathe nitrous oxide, an oiled silk bag, capable of containing several quarts, must be provided, or a bladder may be employed if nothing else can be conveniently procured. A tube is fixed to the bag, and a brass connecting tube fitted to the other end of this tube, in order that it may be attached easily to a gosometer, or any other reservoir from which the gas is obtained. The tube may be made either of brass, glass, or hard wood. I generally prefer the latter, as it is not so liable to do any injury when the person breathing the gas has been strongly excited by it, and will not part with it, which is often the case. To prevent also the bad effects that might arise from too frequent an inhalation of the same portion of air, there ought to be an aperture in the side of the tube, which may be kept closed by an assistant placing his thumb upon it when the bag is filling and during the respiration of the gas ; and by re- moving it when it has been continued sufficiently long, and closing the neck of the bladder with the finger and thumb, no Fig. 31. violent measures are required to force the tube from the mouth of the person who has been breathing the gas, as in this manner, he will now respire nothing but at- mospheric air through the tube. This form of the tube is represented in the annexed cut. (Fig. 31.) 111. Before inspiring the nitrous oxide freely, a small quantity of it should always be tried very cautiously at first, to see if it is pure. Its taste is sweet and pleasant, and has an agreeable though very faint odour. If the materials of which the nitrate of ammonia is made are not pure, the gas is seldom good, especially if any sulphate or muriate of am- monia should have been present. When inspired, the lungs should be previously emptied as much as possible of common air by a deep expiration, and the gas inspired and expired into 46 PREPARATION OF NITRIC OXIDE. the bladder several successive times, the nose being held by the fingers at the same time. The tube should be large enough to allow the gas to pass freely along. When a narrow tube is used, the difficulty of respiration is so great that it seldom produces its characteristic effects. When warm-blooded animals are placed in vessels full of nitrous oxide, they die in a short time, and the blood becomes purple ; the muscles at the same time lose their irritability ; even fishes die in a short time in water impregnated with this gas, which acquires a very slight sweet taste. Sect. II. — Deutoxide of Nitrogen or Nitric Oxide. Equivalent by weight 30 ,• by volume I I 1 ( two measures). Specific gravity 1.0416. Weight of 100 cubic inches 31.77 grains. Water absorbs from jotk to a ^th of its volume of this gas. It produces a dense orange red coloured gas when mixed with air or oxygen gas, which is completely absorbed by water. 112. The deutoxide of nitrogen is another gaseous com- pound of nitrogen and oxygen, usually prepared by decom- posing nitric acid by means of copper or mercury. For this purpose, copper clippings are put into a tubulated retort, and nitric acid diluted with one and a half times or twice its bulk of water poured over them; an effervescence immediately commences, the liquid assumes a greenish blue colour, and the copper is dissolved ; the deutoxide of nitrogen that is disen- gaged may be collected over the pneumatic trough in the man- ner represented in Fig. 8, page 6. 113. In this process, every three equivalents of metallic copper decompose two equivalents of nitric acid, combining with the greater portion of the oxygen, and being converted into three equivalents of the peroxide of copper, and each of these at the same time unites with two proportions of nitric acid, forming pernitrate of copper, which remains in solution ; PREPARATION OF NITRIC OXIDE. 47 the nitrogen of the two proportions of nitric acid which are de- composed comes away with the remaining oxygen in the form of deutoxide of nitrogen. The following diagram will convey a more precise idea of the manner in which the copper reacts upon the nitric acid which is decomposed, the part to the left expressing the elementary constitution of the two proportions of nitric acid, while the other shows the manner in which they arrange themselves. Nit. 14 ^?^30 Nitric oxide. Ox. 8- Nitric J Ox acid 54 i Ox q x g_^T=>16 4 64 Copper = 80 perox. of C. 16+64 Copper = 80 perox. of C. Nitric J Ox. 8 ^T> 16 + 64Co PP er = 80perox. of C. acid 54 j ^Nit. 14 ^^^30 Nitric oxide. 114. The solution of nitrate of copper that remains in the retort may be reserved for future experiments. Should a more diluted acid be employed, as is usually recommended, heat is necessary for the preparation of this gas, and towards the end of the process water often rushes from the pneumatic trough to the retort, if the process is not constantly attended to, (particularly if the retort has a wide beak) nothing but watery vapour passing over after all the nitric acid has been decomposed, or converted into nitrate of copper by combining with the peroxide, which is condensed whenever it comes in contact with the cold water. 115. Mercury and copper are perhaps the only metals that disengage pure nitric oxide when they act upon nitric acid. When mercury is employed, the gas is obtained in the same manner as by the action of copper on nitric acid, heat being applied to the retort containing the materials when the acid is much diluted, while little or none is required when a small quantity has been added. 48 NITRIC OXIDE. 116. Deutoxide of nitrogen is a transparent and colourless gas, easily distinguished from all other substances by the dense orange-red and suffocating vapours that are produced when it is brought into contact with oxygen gas or atmospheric air, or with any gaseous mixture containing oxygen gas. It does not support the combustion of all inflammable substances, burning sulphur and a lighted candle being immediately extinguished in it. Phosphorus and charcoal burn with greater brilliancy than usual if they are introduced into this gas in a state of active combustion. 117- To see these properties of the deutoxide of nitrogen, the suspended candle (6) may be introduced into a jar or bottle containing this gas, and the burning sulphur into another, being Fig. 32. kindled in a small brass or copper cup (Fig. 32) sup- T ported by an iron wire fixed to a flat piece of sheet copper, large enough to cover the mouth of the gas or bottle into which the sulphur is placed. A similar cup may be used for holding the phosphorus, which must be allowed to burn a second or two before it is put into the gas, and dried well with blotting paper before it is kindled, to pre- vent it from throwing off sparks. Instead of a cup, a small iron wire cage may be attached to another plate of copper by a suspending wire, into which small fragments of charcoal are placed when it is to be burnt in nitric oxide gas. The most convenient method of obtaining the charcoal in an active state Fig. 33. of combustion is to place a small piece of red hot charcoal from a chauffer into the cage along with the rest, and to hold it for a short time in a jar of oxy- gen gas, transferring it into the bottle containing the nitric oxide (Fig. 33.) after it has been pro- perly kindled. The annexed figure represents the cage, &c. placed in a bottle of nitric oxide gas. 118. The phosphorus is converted into phosphoric acid, and the carbon into carbonic acid during combustion, while the nitrogen is in both cases set at liberty. 119. Hydrogen does not detonate with this gas when they are mixed together and exposed to heat, but burns away with a quiet though silent flame of a white colour, with a tinge of 4 NITRIC OXIDE* 49 giteen. Equal measures of the gases may be mixed together for this purpose in a long glass jar, and a lighted match ap-» plied to the mixture. 120. When oxygen gas and the deutoxide of nitrogen are mixed together, the proportions in which they re-act upon one another, and the nature of the resulting compound, is modified by a variety of circumstances. Three different compounds, viz. hyponitrous, nitrous, and nitric acids, are formed in various proportions, according to the relative quan- tities of the gases, the size and shape of the vessel in which the mixture is made, the nature of the fluid over which they are mixed, the time they are left in contact with each Other, and other circumstances of less importance. 121. When an excess of nitric oxide is mixed with oxygen in a tube containing a solution of caustic potash over mer- cury, every half measure of oxygen, (one equivalent) com- bines with two measures of nitric oxide, (one equivalent) and are completely absorbed by the solution, hyponitrous acid being formed, which remains in combination with the potash. This is the smallest proportion of oxygen which nitric oxide can combine with, and the acid formed in this manner must evidently consist of one equivalent of nitrogen and three of oxygen ; it has not hitherto, however, been obtained in an insulated state, being always decomposed when any acid is added to detach it from the potash. 122. When two measures of nitric oxide (one equivalent) are mixed with one measure of oxygen (two equivalents) in a wide jar over water, a complete condensation ensues ; all the oxygen combining with the nitric oxide, and forming nitrous acid vapours, which are speedily absorbed by the water. 123. Both these compounds (nitrous and hyponitrous acids,) are formed when equal bulks of atmospheric air and nitric oxide are mixed together in a wide jar, two equivalents of oxygen combining with one of nitric oxide, form nitrous acid, which is immediately condensed, while other two equi- valents of oxygen combine each with one equivalent of nitric oxide, forming two equivalents of hyponitrous acid, which are also condensed. Hence, as every measure of oxygen re-acts E 50 NITRIC OXIDE. on three times its bulk of nitric oxide, and a complete con- densation takes place, on dividing the amount of this by four, we ascertain the quantity of oxygen which may be present in a given bulk of air. Gay Lussac has found that the quantity of oxygen in mixed gases may be determined in the same manner, whether there shall be a larger or smaller proportion of oxygen present than exists in atmospheric air, taking care always to have a sufficient quantity of deutoxide present, the condensation being always uniform when the nitric oxide is added at once to the oxygen in a wide vessel. When a nar- row tube is employed for mixing the gases, the condensation is not uniform, and the resulting compounds are so slowly ab- sorbed, that it is necessary to agitate them with the water, when a portion of nitric oxide is at the same time condensed. 124. These experiments may be made by mixing air and oxygen with different proportions of nitric oxide in glass jars over the pneumatic trough, taking a small jar to measure the different quantities. Any excess of nitric oxide may be easily detected, by mixing a little air or oxygen with the gas in the jar suspected to contain it ; if, on the other hand, all the oxygen should not have been consumed, on introducing a lit- tle nitric oxide, ruddy vapours will be immediately produced ; hence, nitric oxide and oxygen gas may be employed, each to indicate the presence of the other ; and by adding an excess of one to any gaseous mixture containing the other, it may be entirely removed, as the compounds which they form are so readily absorbed by water. 125. If the nitric oxide is made to pass through a solution of the green muriate or sulphate of iron, a large quantity of this gas is absorbed, the liquid becoming quite black and opaque when fully saturated with the nitric oxide. This solution was employed by Sir. H. Davy for ascertaining the quantity of oxygen in any gaseous mixture, as it absorbs it quickly ; it is not much relied on now, however, as an evolution of nitric oxide usually accompanies, or at least speedily follows the ab- sorption of the oxygen gas. The change in the appearance of the solution of the sulphate of iron, and the absorption of the nitric oxide, may be easily shown by introducing the beak NITROUS ACID. 51 <*f a retort from which nitric oxide is escaping under the surface of the liquid placed in a glass vessel. When the solution is cold, neither the nitric oxide nor the sulphate of iron, it is affirmed, are decomposed ; but when exposed to heat, a large portion of the gas is disengaged, while the protoxide of iron, uniting with the oxygen of the rest, and of a portion of water which is decomposed, is converted into peroxide of iron, the nitrogen of the nitric oxide combining with the hydrogen of the water to form ammonia. Sfxt. III. — Hyponitrous Acid. Equivalent by Weight, 38. 126. Hyponitrous acid may be obtained, in combination with potash, in the manner described in 121 ; but it has never been procured in a free state, and is always resolved into ni- trous acid, and deutoxide of nitrogen, when any acid is added to the compound which it forms with potash ; one proportion of the acid losing one equivalent of oxygen, by which it is converted into nitric oxide, while another combining with this becomes nitrous acid. Sect. IV. — Nitrous Acid. Equivalent by Weight, 46 ; by volume, □ (one measure.) Specific gravity of liquid acid, 1.452 ,• boils at 82 ,• — Spe- cific gravity of vapour, 3.19- Weight of 100 cubic inches 97-428 grains. 127- To prepare liquid nitrous acid, dry nitrate of lead is exposed to heat in a green glass retort, placed in a sand bath (in the manner that will be described when we come to nitric acid,) till it is completely decomposed, and the vapours which are disengaged condensed in a receiver kept cold by snow or ice. The nitric acid is completely decomposed by the heat, 52 NITROUS ACID. and resolved into nitrons acid and oxygen, the former being, condensed into an orange-red coloured fuming liquid, while oxide of lead remains in the retort. 128. The same compound may be obtained in the gase- ous state, by mixing two measures (one equivalent) of nitric oxide with one measure (two equivalents) of oxygen. This, mixture must be made in a flask, previously exhausted by the air-pump, and a condensation takes place equal to two-thirds of the mixed gases. It consists, accordingly, of one equiva- lent of nitrogen (14) and four of oxygen, (32,) one of the ni- tric oxide containing two of oxygen, and its equivalent by vo- lume will be represented by one measure, (□). The dry gas- es mixed in the proportions mentioned form nothing but ni- trous acid vapours, and they must not be mixed together over either water or mercury, as the former determines the forma- tion of a portion of nitric acid, and the latter decomposes ni- trous acid. 129. Liquid nitrous acid evaporates speedily when expos- ed to the air, forming a highly corrosive and suffocating va- pour. It is capable of supporting the combustion of a taper or phosphorus, while other substances, as sulphur, are extin- guished in it, though introduced in a state of active inflam- mation. A large quantity of water decomposes it completely, converting it into nitric acid which remains in combination with the water, and forms a colourless solution, and into nitric oxide gas, which escapes with effervescence ; when a smaller quantity of water is added to the acid, it passes through a variety of shades of colour, from a deep reddish brown to a greenish blue, and finally becomes quite colourless. Both the solution and the acid redden the vegetable blues, and are ex- tremely acrid and corrosive of animal and vegetable matter. 1 30. Pure nitrous acid is seldom prepared, except for ex- perimental illustration. It may be employed, however, to oxidate a number of substances, as it gives off its oxygen readily to a great number of bodies. PREPARATION OF NITRIC ACID. 53 Sect. Y,— .-Nitric Acib. Equivalent by weight, 54 (Ox. 40 + 14 N.^ Equivalent of common liquid nitric acid J 2, (Nitric acid, 54 + 18 wafer.) Transparent and colourless, but soon acquires a straw colour on exposure to light ; emits suffocating fumes when exposed to the air, and absorbs water. Ex- tremely acid and caustic. Specific gravity 1.500 ; boils at 210, and becomes solid when cooled to — - 62. 131. Nitric acid has not hitherto been obtained in an insu- lated state, and the term is usually applied to a compound of the dry acid with two proportions of water. To prepare this acid, bruised nitrate of potash is put into a plain or tubulated retort, exposed to heat with an equal weight of sulphuric acid, and the product condensed in a glass receiver. When a plain retort is employed, the sulphuric acid must not be poured down the neck, but introduced into the body of the Fig. 34. retort by a long bent funnel, (Fig. 34.) as any sulphuric acid that might re- main in the neck of the retort would be carried over with the nitric acid in the subsequent stages of the operation, and render the product impure. The retort is then placed in a sand bath, (Fig. 35.) consisting of an iron bason with a little sand in it, so that the low- er part of the retort shall rest about an inch above the bottom of the bason, and, when it has been properly adjusted, and the beak introduced into a receiver, more sand is then poured in till the iron bason shall have been completely filled. The 54 PREPARATION OF NITRIC ACID. body of the retort may be covered to a greater height with sand, by placing round it a ring of thin sheet iron, from one to two inches deep, a small piece being cut out on one side, to allow the neck of the retort to be inclined, in the manner shown in the figure. The retort should be of such a size as to allow at least half an inch of sand between it and the sides of the iron bason, otherwise it is very apt to be broken when the heat is raised. The iron bason is heated by the furnace used for the pre- paration of oxygen gas, (Fig. 1. p. 2.) to which it is accurate- ly fitted, the flange on the outside of the bason resting on the upper part of the furnace, while the lower part is freely ex- posed to the action of the fire; the retort not being adjusted till the fire has been kindled, and the iron bason put in its place. 132. The degree of heat is regulated by the plugs or air- holes at the bottom of the furnace, (5,) and great care must be taken not to expose the retort to a strong heat, as the mix- ture is extremely apt to boil over ; the product is also greater the lower the temperature by which the distillation is effected. The acid that is disengaged must be condensed in a receiver, kept cold by a slender stream of water, which may be kept constantly flowing from a large jar or pitcher by a syphon made of glass or tin, in the manner represented in the figure ; the distillation may be continued, till red vapours have been seen in the retort for some time, and the acid must be kept in a glass bottle with a ground stopper. 133. Light green glass retorts do better for conducting this distillation than the flint glass retorts, and should always be preferred when they can be procured, as they are not nearly so liable to be broken. Instead of heating the retort by a sand-bath, the operation may be conducted much more expe- ditiously on the small scale by means of a chauffer; constant attention, however, will be necessary in this case to regulate the fire, as it is not so easy in this manner to maintain a uni- form temperature. 134. The distillation may also be conducted in flasks with a long glass tube bent at one end in the manner shown in the TREPANATION OF NITItJC ACID. 55 Fl S- 36 - annexed figure, (Fig. 36) or the con- densation of the acid may be effeet- Ted almost entirely in the tube. (See Fig. 27, p. 32.) This is a very convenient method of conducting y\ ~~^^r^~\ the process, and is often preferred -~^ to distilling the nitric acid from a ^ retort, though beginners find some v difficulty in adjusting the tube. The nitre and the sulphuric acid are first put into the flask, and a thin tube bent at an acute angle about two inches from one extremity, and a very little less in diameter than the neck of the flask, is surrounded with some well worked clay, and put into it, a small quantity of plaster of paris * being placed over the luting to render it perfectly tight. The acid is condensed in a receiver, into which the other extremity of the tube is introduced. 13B. In this process, the materials are mixed so nearly in the proportion of two equivalents of sulphuric acid to one of nitrate of potash, that we may assume this to be the case in ex- plaining the reaction which ensues. Every two equivalents of the common sulphuric acid (96) consist of two equivalents of water (18) and two of dry sulphuric acid (80) ; the nitrate of potash, on the other hand, is composed of one equivalent of potash (48) and one of nitric acid (54). The dry sulphuric acid combines with the potash, forming bisulphate of potash, and the water goes to the nitric acid, forming tiie liquid which is condensed in the receiver, dry nitric acid not having hither- .to been procured in a free state, as it is always decomposed when disengaged from any of its compounds if no water shall be present to condense it. The annexed diagram is intended to give a clearer view of the theory of the action, the part to the left showing the composition of the materials, while, in the other, the products of the decomposition are seen. * In using plaster of paris (dry sulphate of lime) as a lute or cement, the most convenient method is to take a small quantity of water and pour the plaster of paris upon it, till it shall have absorbed it all ; it must then ba cdrred, and in a short time it will begin to set. 56 PREPARATION OF NITRIC ACID, Common sulphuric acid 96 Water 9 '~r"""f-~/ T& common nitric acid. Water 9"' / Dry Acid 40- I Dry Acid 40- Nitrate off Nitric Acid 54/ potash 102\ Potash 48 ^K 128 bisulphate of potash. 136. Though the sulphuric acid and nitre must be used in these proportions in order to obtain all the nitric acid from the nitre, a smaller quantity of sulphuric acid is in general em- ployed. The proportions already given are those recommend- ed by the London College, but the Edinburgh and Dublin Colleges take only two parts of sulphuric acid to three of nitre. One equivalent of sulphuric acid (49) is sufficient for decomposing an equivalent of nitre (102) ; but as it only con- tains one equivalent of water (9), and as the nitric acid in the nitre requires two, a great portion of the nitric acid is decom- posed, being resolved into nitrous acid and oxygen. When two parts by weight of sulphuric acid are mixed with three of nitre, it is evident that the product will be composed of nitric acid and nitrous acid, and this forms what is usually, though incorrectly, termed nitrous acid. The salt that remains in the retort is a mixture of the sulphate and bisulphate of po- tash. The nitric acid that is disengaged at first comes away with the water of the sulphuric acid and is condensed ; to- wards the end of the process it is decomposed as it is separat- ed, a large quantity of dense red fumes of nitrous acid being disengaged, the most of which are condensed by the nitric acid in the receiver, if it is kept sufficiently cool. 137- In conducting this process on the small scale, three ounces (water measure) of sulphuric acid to eight ounces by weight of nitre will be found convenient proportions, using a retort of such a size that it shall be rather less than half full when both the nitre and the acid have been introduced, and continuing the distillation till a quantity of acid shall have been obtained equal in measure to the sulphuric acid em- ployed. By continuing the heat still longer, a little more acid may be obtained. 138. Nitric acid has usually a slight tinge of yellow, even NITRIC ACID. 57 when prepared from nitre with an equal weight of sulphuric acid, occasioned by the presence of a small quantity of nitrous acid, formed by the decomposition of a minute portion of the nitric acid during its preparation. To deprive it completely of colour, it must be exposed to a gentle heat, as long as any nitrous acid vapours or nitric oxide gas is expelled. When the nitric acid has been prepared with a small quantity of sul- phuric acid, it is necessary to expose it to heat for a consider- able time before all the nitrous acid is disengaged. By expo- sure to light, part of it is decomposed, oxygen gas being evolved and nitrous acid formed, imparting to the whole various tints from a light straw colour to a deep orange, according to the quantity produced. 139- It is seldom necessary to expose the mixed acid to heat so as to obtain pure and colourless nitric acid, as it may be used for almost all the purposes to which the latter is ap- plied. It is even preferred in many processes from its great strength, being always stronger and more active than the pale acid. Dr. Hope has prepared it with so high a specific gra- vity as 1.54, though the specific gravity of the colourless acid does not exceed 1.500. 140. The annexed table by Dr. Thomson shows the speci- fic gravity of several compounds of nitric acid and water in regular atomic proportions, and the quantity of real acid con- tained in a hundred parts of each.* Table of Nitric Acid hy Dr. Thomson. Specific Gra- Acid in 100 Atoms of Atoms or' vity. parts. acid. water. 1.4855 75.000 2 1.4546 66.668 3 1.4237 60.000 4 1.3928 54.545 5 1.3692 50.000 6 1.3456 46.260 7 1.3220 42.857 8 1.3032 40.000 9 1.2844 37.500 10 1.2656 35.294 11 1.2495 32.574 12 1.2334 31.579 13 1.2173 30.000 14 1.2012 28.571 15 Thomson's First Principles of Chemistry, vol. i. p. 114. 58 NITRIC ACID. The following is a more extensive table by Dr. Ure, show- ing the quantity of real acid in liquid nitric acid of different specific gravities, which will be found very convenient to refer to, in making experiments where acid of various degrees of strength is required. Table of Nitric Acid by Dr. Ure. SpecificGravity. Dry.'acidinlOO iSpecificGravity. Dry acid in 100 SpecificGravity. Dry acid in 100 parts. ■ parts. parts. 1.5000 79.700 1.3783 52.602 1.1895 26.301 1.4980 78.903 1.3732 51.805 1.1833 25.504 1.4960 * 78.106 1.3681 51.068 1.1770 24.707 1.4940 77.309 1.3630 50.211 1.1709 23.900 1.4910 76.512 1.3579 49.414 1.1648 23.113 1.4880 75.715 1.3529 48.617 1.1587 22.316 1.4850 74.918 1.3477 47.820 1.1526 21.519 1.4820 74.121 1.3427 47.023 1.1465 20.722 1.4790 73.324 1.3376 46.226 1.1403 19.925 1.4760 72.527 1.3323 45.429 1.1345 19.128 1.4730 71.730 1.3270 44.632 1.1286 18.331 1.4700 70.933 1.3216 43.835 1.1227 17.534 1.4670 70.136 1.3163 43.038 1.1168 16.737 1.4640 69.339 1.3110 42.241 1.1109 15.940 1.4600 68.542 1.3056 41.444 1.1051 15.143 1.4570 67.745 1.3001 40.647 1.0993 14.346 1.4530 66.948 1.2947 39.850 1.0935 13.549 1.4500 66.155 1.2887 39.053 1.0878 12.75» 1.4460 65.354 1.2826 38.256 1.0821 11.955 1.4424 64.557 1.2765 37.459 1.0764 11.158 1.4385 63.760 1.2705 36.662 1.0708 10.361 1.4346 62.963 1.2644 35.865 1.0651 9.564 1.4308 62.166 1.2583 35.068 1.0595 8.767 1.4269 61.369 1.2523 84.271 1.0540 7.970 1.4228 60.572 12.462 33.474 1.0485 7.173 1.4189 59.775 1.2402 32.677 1.0430 6.376 1.4147 58.978 1.2341 31.880 1.0375 5.579 1.4107 58.181 1.2277 31.083 1.0320 4.782 1.4065 57.384 1.2212 30.286 1.0267 3.985 1.4023 56.587 1.2148 29.489 1.0212 3.188 1.3978 55.790 1.2084 28.692 1.0159 2.391 1.3945 54.993 1.2019 27.895 1.0106 1.594 1.3882 54.196 1.1958 27.098 1.0053 0.797 1.3833 53.399 141. Nitric acid attracts water from the air, and combines with it in all proportions, a considerable condensation attend- ing the combination which is also accompanied by an evolu- tion 'of heat. The greatest degree of condensation takes NITKIC ACID. 59 place according to Dr. Ure, when 58 parts of acid by weight (spec. grav. 1.500) are mixed with 42 of water, amounting to about one-twelfth of the bulk of the whole, the temperature rising at the same time about 80 degrees. The aqua fortis of commerce is merely a diluted nitric acid prepared by distillation from nitre with diluted sulphuric acid. It contains only one-fourth part as much acid accord- ing to Dr. Ure, as the strong nitric acid; what is called double aqua fortis, contains twice as much acid, being half as strong as the best nitric acid. The diluted nitric acid of the Edinburgh and Dublin col- leges, consists of equal parts of the strong acid and water by weight ; that of the London college is prepared by mixing one part by measure of acid with nine parts of water, and contains therefore much less real acid than the diluted acid of the Edinburgh and Dublin colleges. The temperature at which this acid boils varies according to the quantity of water combined with it. When its specific gra- vity is 1.42, it boils at 248, and distils unaltered ; when its specific gravity is above or below this point, it boils at a lower temperature, and stronger acid becomes weaker, and weaker acid stronger by boiling. Its freezing point varies also ac- cording to the quantity of water it contains ; acid of the spe- cific gravity of 1.420, requires a great degree of cold ( — 41) to congeal it. When poured upon snow it causes it to melt speedily, and an intense degree of cold is produced. 142. If exposed to a red heat in a porcelain tube, it is re- solved into oxygen and nitrogen gases, which may be collect- ed in a pneumatic trough. To perform this experiment, a tube about three-fourths of an inch in diameter, stuffed with fragments of earthen ware (merely to extend the internal sur- face) is made to traverse a furnace or large chauffer with a chimney fitted to it, a small tubulated glass retort being fixed to one end, and a bent glass tube to the other, with pieces of linen or cotton cloth and the chalk lute, the extremity of the glass tube being made to dip under the shelf of the pneu- matic trough. The arrangement of the apparatus will be 60 NITRIC ACID. easily understood by referring to Fig. 19, p. 18. A small quantity of nitric acid is poured into the retort, and when the porcelain tube is at a full red heat, the acid is made to boil by a small chauffer, or a spirit lamp placed below it. The stopper is then put into the retort (not before, lest water should rush from the pneumatic trough into the porcelain tube) and the acid vapours are decomposed as they pass through the red hot tube, the oxygen and nitrogen gases be- ing collected in jars placed over the trough. The porcelain tube ought not to be exposed to a strong heat at first, but gradually brought to a full red heat, as it is not then so liable to be broken. 143. Nitric acid (by which the common liquid nitric acid is always understood, composed of one equivalent of real acid, and two of water) emits very acrid fumes when exposed tq the air ; it possesses in a very eminent degree all the charac- teristic properties of an acid, corroding animal and vegetable substances, reddening the vegetable blues, and forming salts with the different salifiable bases. Its taste is intensely sour and acid, even when diluted with a large quantity of water, and it stains the skin of a yellow colour, which remains till the cuticle is completely abraded. It is distinguished from all other acids by the facility with which it affords oxygen to metals and combustible bodies, most of which decompose it with great rapidity ; all the oxygen, however, is not withdrawn from the nitrogen, nitric oxide, and nitrous acid being gene- rally disengaged during the action that takes places. 144. From these properties, nitric acid is often employed to oxidate a variety of substances. But when it is of a parti- cular specific gravity (1.48) it is scarcely affected by the metals at ordinary temperatures ; on adding a small quantity of water, however, a decomposition immediately begins, the metal often taking oxygen both from the acid and the water. When this takes place, the hydrogen of the water unites with the nitro- gen of the acid forming ammonia, which combines with part of the nitric acid that is not decomposed, forming nitrate of ammonia ; this explains the appearance of the white fumes NITRIC ACIU. 61 which are often seen intimately blended with the nitrous acid va- pours that are formed when this acid is decomposed by a metal having a great affinity for oxygen. 145. If a current of nitric oxide gas (p. 48) be transmitted through colourless nitric acid, a large quantity of this gas is absorbed, and the acid speedily acquires a light straw colour, which deepens to a reddish brown, and passes through various shades of olive and green, till it at last becomes almost blue. On exposing the acid in this condition to heat, nitrous acid and nitrous oxide are disengaged, and the liquid assumes the same appearance as it had at first. The apparatus best adapt- ed for this purpose is a retort or a flask with two tubulures, one for introducing the materials for preparing the nitric oxide, and the other for a bent glass tube which is accurately fitted to it by grinding, and intended to conduct the nitric oxide to the nitric acid to be impregnated with it. The acid may be placed in a common white glass bottle, or what is Fig. 3?. better, into a bottle of the form shown in the annexed figure (37) ; one of the tubulures be- ing accurately ground to the other leg of the glass tube, and the opposite one having a se- cond tube fitted to it to convey away any excess of nitric oxide to a pneumatic trough. When the nitric oxide ceases to come over, the stopple must be taken out of the flask, and the second tube out of the pneumatic trough, otherwise the pressure of the atmosphere might force the acid into the flask, or part of the water of the pneumatic trough into the bottle containing the acid. The change of colour arises from the nitric oxide taking oxygen from the nitric acid, both being converted into nitrous acid, the one by losing and the other by gaining oxygen, the depth of colour varying according to the quantity of oxide absorbed. It has not yet been determined whether any hypo- nitrous acid is formed during these changes, though several- chemists appear inclined to adopt this opinion. 62 NITRIC ACID. 146. If small quantities of water be added to the strong fuming acid (composed of nitric and nitrous acids) prepared by distilling nitre with two-thirds of its weight of sulphuric acid, it gradually loses its deep orange red colour, and passes through various shades of olive, green, and blue ; and, if a sufficient quantity of water be added, it becomes quite colour- less. 147. The nitric acid of commerce is often contaminated with sulphuric and muriatic acids, the former arising from the distillation of the acid having been conducted in a careless manner, and the latter, from the nitre employed containing some muriatic salts. To detect the presence of these acids, the nitric acid must be diluted with three or four parts of water, and solutions of nitrate of baryta and nitrate of silver added to separate portions of the acid in a glass. If any sul- phuric acid is present, the nitrate of baryta will cause a white precipitate, sulphuric acid always combining with baryta when they meet in the same solution, and forming an insoluble compound, the sulphate of baryta. Nitrate of silver pro- duces the same effect when muriatic acid is present, the chlo- rine (one of the elements of the muriatic acid) combining with the metallic silver, and forming a white curdy precipitate. In applying these tests it is always necessary to dilute the nitric acid with water, as strong nitric acid in many cases gives a precipitate with saturated solutions of salts whether pure or not, the nitric acid combining with the water that retains the salt in solution, while it is precipitated in the solid form. 148. The best method of separating sulphuric acid from nitric acid is to redistil the acid with an additional quantity of nitre, the sulphuric acid combining with the potash, and disengaging an equivalent portion of nitric acid. When nitric acid is prepared from sulphuric acid and nitre by a slow fire, using two parts of the acid, by weight, with three of nitre, I have never seen the product contaminated with sulphuric acid. To separate muriatic acid, nitrate of silver must be added to it, and the pure acid separated by distillation. It will be found much more convenient when a very pure nitric acid is required, to examine if the nitre contains any muriatic acid "N1TRTC ACID. 63 before distillation, by adding a solution of the nitrate of silver to a small quantity of nitre dissolved in water, and crystal- lizing it repeatedly till the crystals shall be obtained quite free from muriatic salts, if they shall contain any, the solution of the nitre giving no precipitate with the nitrate of silver where these have been completely removed. 149. Pure nitric acid is easily recognised by the facility with which it is decomposed by inflammable substances and the metals, especially zinc, tin, mercury, and copper, and the large quantity of deep ruddy coloured fumes which are dis- engaged ; when present in small quantity, however, it is not so easily recognised, as there are no substance with which it forms characteristic and insoluble precipitates. The only test, indeed, which can be relied on, is that proposed by Dr Liebig : (Ann. de Chimie xxxv. 80.) he recommends the liquid under examination to be mixed with a solution of indigo in sulphuric acid till it requires a perceptible blue colour ; a few drops of sulphuric acid are then added to the solution, and the whole is boiled for a short time. If the liquid contain any nitric acid it will be completely deprived of colour, or rendered yel- low, if the proportion of acid is extremely small. One part of nitric acid may be detected by these means in four hundred parts of water, and if a small quantity of muriatic acid or com- mon salt be mixed with the liquid before applying heat, a five hundredth part of acid may, it is affirmed, be detected in this manner. 150. Another very delicate method of detecting nitric acid, consists in adding a little sulphuric acid to any solution sus- pected to contain it, by which it will be separated from any salifiable base with which it may be combined, and then put- ting in a few drops of muriatic acid with a small piece of gold leaf. If any nitric acid is present, it will immediately decompose the muriatic acid and liberate a portion of chlorine (one of the elements of muriatic acid) which will dissolve the gold. This test, however, cannot be relied on in all cases, as chloric acid produces the same effect when treated in this manner. 151. The salts of nitric acid are generally soluble in water, 64 NITRIC ACID. easily decomposed by heat, and deflagrate with inflammable' substances. It is easily separated from all its combinations by sulphuric acid, aided by the application of a gentle heat. 152. Nitric acid is used in a great number of the arts. From the facility with which it affords oxygen, it is constantly employed in a great variety of chemical processes, as in the preparation of the nitrates of mercury, tin, copper and bis- muth ; for etching on copper ; to form aqua regia (the solvent of gold) with muriatic acid, and in the preparation of sulphu- ric acid, nitric ether, &c. Diluted with a large quantity of water, it is used internally as a tonic, and occasionally with success, it has been affirmed, in counteracting the consecutive effects of opium ; and in the form of nitro-muriatic acid as a bath, a sufficient quantity being added to the water to make it excite a slight prickling sensation in the skin. Strong nitric acid is also occasionally employed as an escharotic, and when disengaged in the form of vapour (by pouring sulphuric acid or nitre in a cup placed in a ladle containing hot sand) for the purpose of destroying contagion. 153. Oxygenated nitric acid may be prepared much in the same manner as oxygenated water, the deutoxide of barium being dissolved in diluted nitric acid, the barytes removed by sulphuric acid, and the liquid that remains strengthen- ed by evaportion in the exhausted receiver of the air pump. It presents the same general phenomena with many of the metals and metallic oxides, &c. as oxygenated water, but has not hitherto been applied to any use. Sect. VI. — Atmospheric Air. Equivalent by weight, 36 ,• (nitrogen, tico equivalents, 28 + 8 oxygen.) Its specific gravity is reckoned 1.000, being taken as standard of comparisoa in estimating the specific gravity of all other gases. Weight of 100 cubic inches 30.5 grains. It is 828 times lighter than water. 154. The discovery of the composition of atmospheric air, was made by Scheele, (and soon after by Lavoisier,) but the ATM0SPHE11IC AIU. (')!> fexact proportion of oxygen and nitrogen which it contains, was not ascertained till lately. The original experiment of Scheele may be easily repeated, by pouring two ounces of a solution of $he sulphureted hydrosulphuret of potash or lime into a bottle, capable of containing about twelve ounces, closing it accurate- ly with a glass stopple, and opening it under water, after it has stood for some time. Scheele allowed the bottle to remain for two weeks before he opened it ; but if it is frequently agitated, the stopple may be taken out in half an hour, when water will immediately rush in to supply the place of the oxygen of the air included in the bottle, the greater part of which will have been absorbed. 155. When the constitution of atmospheric air had been ascertained, and the necessity of the presence of oxygen for sup- porting respiration and combustion, many were inclined to at- tribute the noxious effects which it occasionally produces, to a diminution in the proportion of this gas, and the discordance in the results of early experimenters, with respect to the quan- tity of oxygen they found in it, gave some countenance to this opinion, though more accurate researches have since shown, that the proportion of oxygen and nitrogen in the air is the same in all quarters of the globe, and at all elevations to which man has reached. The term Eudiometer, now so constantly employed, derived its origin from this opinion, being an ap-, paratus intended for examining the purity, or rather the quan- tity of oxygen in atmospheric air, but now used also for esti- mating the proportion of oxygen in all mixed gases. 156. The method of employing nitric oxide and hydrogen gases for ascertaining the quantity of oxygen in air, has been already pointed out. 1 may remark, however, that Dr. Thom- son has lately shown, that on detonating hydrogen with atmos- pheric air, 100 parts, by measure, of air must be mixed with. 42 measures of hydrogen, in order that all the oxygen may be, consumed ; when less hydrogen is employed, all the oxygen is not consumed, and if a larger quantity is taken, some of the hydrogen unites with the nitrogen, and forms ammonia, caus- ing a greater condensation than would otherwise take place, hydrogen gas is used in Volta's and Dr. Lire's Eudiometers^. 66 ATMOSPHERIC AIE. (See Electricity) and, with spongy platina and hydrogen gas a smaller quantity of oxygen can be detected than in any other way. (67, 68.) 157- Phosphorus has also been employed for eudiometrical purposes, a stick of it being introduced into the air to be ex- amined in ajar or tube, placed on the shelf of the pneumatic trough, and the -white vapours formed by the phosphorus com- bining slowly with the oxygen, are condensed by the water ; the nitrogen is left, increased, however, about ^th part, in volume, by combination with a little phosphorus. The phos- phorus must be allowed to remain in the jar for a considerable time before the oxygen is entirely withdrawn. 158. Professor Hope's eudiometer, which is represented in Fig. 38. the annexed figure, consists of a tube into which the gas to be examined is introduced, about 9 inches long, closed at one end, and ground at the other, so as to fit accurately into the neck of a bottle, which may be two or two and a half inches in diameter, and three inches high. It is filled with a solution of the sulphureted hydrosulphuret of potash or lime, placed under water, and the tube with the gas immediately fixed into it, having placed it also under water, that it may be con- veniently introduced. It is then taken out of the water and inverted, the gas mixing with the liquid in the bottle, which speedily absorbs the oxygen, when they are briskly shaken to- gether. The stopple in the tubulure, at the lower part of the bottle, should be rubbed over with a little gas lute, and fixed firmly in its place before pouring in the liquid sulphuret ; and on taking it out afterwards, from time to time, under water, a portion of this fluid rushes in to supply the place of the oxy- gen absorbed ; by observing the height to which it rises in the tube, which ought to be divided into a hundred parts, the per- centage of oxygen is ascertained by bare inspection. 159. Atmospheric air always contains a small quantity of watery vapour and carbonic acid, which may be easily detect- ed by potash and lime water ; the former attracting the water and becoming liquid ; while the lime in the latter combines with the carbonic aeid, and forms an insoluble compound* ATMOSPHERIC AIR. f?7 which collects as a crust on its surface : the dry potash may be placed on a plate, and the lime water should be put into a broad shallow dish, so as to expose an extensive surface to the air. Besides these, it must often contain a great variety of other kinds of volatile matter, though in too small a propor- tion, in general, to be rendered sensible by any means of an- alysis which we at present possess. 160. The chemical agency of atmospheric air depends al- most entirely, so far as we are acquainted with it, upon the oxygen which it contains. It is it that supports combustion and respiration; and, indeed, in all those chemical changes that are constantly going on at the surface of the earth, where atmospheric air acts an important part, the oxygen has ak ways been found to contribute to the new arrangements which take place, while the nitrogen appears seldom to undergo any alterations. The atmosphere is supposed, from astronomical observations, to be about forty-five miles in height, gradually diminishing in specific gravity as it recedes from the surface of the earth, being less and less compressed by the smaller column of air above. It is highly elastic and compressible, like all other gaseous fluids ; and, according to Mr. Perkins, may be made to assume the liquid form, by a pressure, equal to 2000 atmospheres. It has been calculated to be equal in weight to a leaden ball about sixty miles in diameter, and it presses up- on the surface of the earth, with a force equal to a weight of fifteen pounds on every square inch. It is not heated direct- ly by the rays of the sun, allowing all kinds of radiant matter to pass through it, without being in any way affected by it. SULPHI7K* CHAP. IV. SULPHUR. Equivalent by weight, 16 ; by volume, O (one measure.) Its usual Specific Gravity is 1.99 ; by throwing it when melted, and at a temperature about 450, into water, it is increased to 2.325. 161. Sulphur is a solid inflammable substance of a light yellow colour, very brittle, with little or no taste, and emit- ting a peculiar odour when rubbed. It is an abundant pro- duction of the mineral kingdom, and is found in large quan- tities in volcanic countries, as Sicily, Italy, and Iceland. It is frequently obtained in pyramidal crystals, and when melted and cooled slowly, it always presents a crystalline structure. Sulphur is also found in combination with a number of the metals, as iron, lead, copper, and antimony ; and by exposing the common yellow iron pyrites (bi-sulphuret of iron) to a red heat in close vessels, it may be procured in considerable quantity. 162. When exposed to heat, it melts at the temperature of 216 or 220, and becomes very thin and fluid at 250. The roll sulphur of commerce is prepared by pouring the melted sulphur in this state into cylindrical moulds ; it gives a crack- ling noise when held in a warm hand, and often falls to pieces, having little cohesion, and being unequally expanded by the heat, as it is a bad conductor of caloric. When ex- posed to a stronger heat, instead of becoming more thin and fluid, as is generally the case with other liquids, it soon be- gins to turn thick and viscid, and at the temperature of 450, the vessel containing it may be inverted without any of the sulphur falling out. By a farther increase of temperature it again becomes more fluid, and if it is then poured into water, it becomes a soft and tenacious mass, which may be xised for taking impressions of seals or medals, becoming hard after SULPHUIt. »wue time lias elapsed. All these circumstances may be easily seen by heating sulphur in a dry Florence flask, over a chauffer, supporting it on a retort stand. 163. To obtain large crystals of sulphur, the best method is to melt one or two pounds in an earthern crucible, and to invert it after it has been removed from the fire and a crust formed on the surface, a small hole having been made to al- low the sulphur that is still liquid to flow out. When the crucible is quite cold, it may be broken, and crystals of sul- phur will be found lining the cavity previously occupied by the sulphur which had been poured out. 164. Sulphur is converted into vapour at 600, and may be condensed unchanged by conducting the sublimation in close vessels. This process is generally resorted to for the purpose of purifying common sulphur, and when the heat is not too great, the vapour of the sulphur condenses in very minute crystalline grains, forming what is commonly called Floivers of Sulphur. To show the sublimation of sulphur, it may be exposed to heat in a retort with a short neck, connected with a large receiver. 165. Sulphur takes fire at about 300, when heated in the open air, burning with a blue flame, and producing very pun- gent suffocating fumes. In oxygen gas it burns much more vividly and with a larger flame, sulphurous acid gas is the product of the action in both cases, unless when the gases are moist, a small portion of sulphuric acid then being form- ed. The apparatus used for the combustion of sulphur in nitric oxide — (Fig. 32. p. 48) — may also be employed here, the oxygen neither increases nor diminishes in volume, but becomes twice as heavy as before from the sulphur which it takes up. 166. Sulphur is insoluble in water, but combines with it when precipitated from any solution containing it, forming a white powder, usually termed the milk of sulphur. The method of preparing it will be described in the last section of this chapter; it is the precipitated sulphur of the pharmacopoeia. Sulphur and alcohol combine when they are presented to each other in the gaseous state ; it is spai-ingly soluble ^0 SULPHUROUS ACID. in ether, but is dissolved readily when boiled in oil of tur- pentine. 167- Sulphur combines with the metals forming a great number of very important compounds, and during the com- bination, heat and light are frequently disengaged ; a certain elevation of temperature is almost always necessary, however, to commence the action, and the appearance of the product varies considerably according to the temperature at which it takes place, 168. The annexed table represents the eonstitutien of the compounds sulphur forms with oxygen and hydrogen, and which will be considered in the following sections. Sulphur. Oxygen. Sulphur. Oxygen. Hyposulphurous acid, 32 + 8 = 40 or |~T~1 + □ === ? Sulphurous acid, 16 + 16 = 32 or D + B — Q Sulphuric acid, 16 + 24 = 40 or Q + Eb = ? Sulph acid. Water. Liquid Sulphuric acid, 40 + 9 = 49 Sulphuric Sulphurous acid. acid. Hyposulphurie acid, 40 + 32 = 72 Sulphur. Hydrogen. Sulphur. Hydrogen. Sulphureted Hydrogen, 16+ 1 = 17 or □ + □ =Q Supersulphureted hyd. 32 + 1 = 33 or QD + □ = ? Sect. I. — Sulphurous Acid. Equivalent by weight, 32. (Oxygen, 16 + 16 sulphur J ; by volume □, (one measure.) Specific gravity, 2.222. Weight of 100 cubic inches, 67-77^ grains. It is a pun- gent and suffocating gas, and may be liquefied by a force equal to the pressure of tivo atmospheres, or by collecting it in small glasses, surrounded by a freezing mixture of snow and salt. The specific gravity of the liquid acid is 1.45, and it boils at 14 F, producing an intense degree of cold. Water absorbs 33 times its volume of sulphurous acid gas at natural temperatures. 169. Though sulphurous acid may be obtained by burn- SULPHUKOUS ACID. 71 ing sulphur in oxygen gas or atmospheric air, it is more easily prepared by decomposing sulphuric acid, heating it in a glass retort with some substance which can deprive it of a portion of its oxygen. Almost all vegetable bodies can pro- duce this effect, and a great number of the metals. Mercury is the metal that is generally employed for the prepara- tion of pure sulphurous acid, two parts of it, by weight, being mixed with three of sulphuric acid in a tubulated glass retort, supported on a retort stand, and heated by a chauffer, or spi- rit lamp. When it is prepared on the small scale, 200 grains of mercury, and 300 of sulphuric acid, (about 3 drachms by measure,) may be taken and put into a retort capable of con- taining about three ounces, (water measure) ; the beak of the retort should be extremely small. 170. As water absorbs such a large quantity of this gas, it must be collected in jars over the mercurial trough, which ia constructed on the same principles as the water trough alrea- dy described, (10.) It may be made of wood, marble, or cast iron ; the latter is generally preferred, and it is well varnished, to prevent it Fi S- 39 « from rusting. The annexed figure (39-) shows the con- j struction of the mercurial S y == — '■ trough which I generally em- /to O ploy; it is 17 inches long, f 1 7 broad, and 5 deep. The | """" "" mercury does not pass under the shelf, so that the body of the trough is only about half as broad below the shelf, as it is above, and it is rounded at the bottom, to save an unne- cessary quantity of mercury. There are four niches at the edge of the shelf, at equal distances from one another, to al- low the beak of a retort to be introduced more easily under jars placed over them, and the small rods attached to two of the sides of the trough, are intended for fixing on clasps or rings, to steady any tall jar that may be left on the shelf. It requires about 140 pounds of mercury, when a number of jars are used. Newman* has cast iron mercurial troughs of two " A philosophical instrument maker in London. 72 SWLPHUROUS ACID. different sizes, the one requiring 65, and the other only 2(F pounds of mercury ; the large trough allows jars to be used rather more than two inches in diameter, and nine inches long ;; but for the other, they must not exceed one and a half inches in diameter. Almost all the most important and interesting experiments, where a mercurial trough is required, may be performed with a small trough containing only 20 pounds of mercury, and a little practice will soon enable the operator to adjust the beaks of one or two retorts (by heating and draw- ing them out at the blowpipe) to the small jars or bottles, which he must use along with it. 1"7I. The jars for the mercurial trough must be mdde at least one-tenth of an inch in thickness, though not more than one or two inches in diameter, they ought also to be ground, at the edges, that they be removed easily on a flat glass plate rubbed over with a little gas lute, without losing any of their contents. The mercurial trough should be placed in a large sheet iron tray, several times the size of the trough itself, to prevent the loss of mercury, that is otherwise unavoidable. Blotting paper is constantly required, to remove any acid or water that may collect on the surface of the mercury, and when any acid gas has been prepared over it, the mercury should always be washed with water afterwards, and dried with a sponge and blotting paper. A red hot poker held for a short time in the mercury, enables this to be done more effec- tually ; it is in this manner also, that the mercury is most conveniently brought to a proper temperature when it is re- quired to be heated for particular experiments. 172. The beak of the retort must be placed near the sur- face of the mercury, that the gas may have to overcome as lit- tle resistance as possible in rising through this heavy fluid; none should be collected till the atmospheric air has been ex- pelled. 173. The theory of the process is very simple ; one equi- valent of sulphuric acid (composed of three of oxygen = 24 4- 16 = one equivalent of sulphur) loses one equivalent of oxygen (8), which combines with the metallic mercury, and the rest of the oxygen comes away in combination with the SULPHUROUS ACID. *J3 Sulphur ill the form of sulphurous acid gas ; the oxide of mer- cury combines with another portion of sulphuric acid which is not decomposed, and is converted into sulphate of mercury. 174. To see how readily this gas is absorbed by water, remove one of the jars filled with it by means of a flat glass plate held firmly to it, or place the thumb or finger on the mouth of a small glass bottle or tube filled with this gas, and take it off under water ; this fluid will instantly combine with it, and be forced up into the tube with explosive violence by the pressure of the atmosphere. 175. Take a small glass tube, closed at one end, an inch or two long, and about l-3d of an inch in diameter ; fill it with water, place the thumb upon it, and invert it in the mercurial trough, transferring a small quantity of water from it into another jar filled with sulphurous acid, in the same manner as gases are transferred from one jar to another. The mercury will immediately rise in the jar, and the water will be seen to absorb many times its own bulk of gas. 176. Sulphurous acid cannot support respiration or com- bustion ; a suspended candle (Fig. 6.) introduced into a jar of this gas is immediately extinguished, and a small quantity of it excites coughing, even when largely diluted with air. 177- Sulphurous acid bleaches a great variety of vegetable colouring matters, sometimes reddening them before the colour disappears. The colouring matter is not completely destroyed, and may be often made to re-appear by a stronger acid, as the sulphuric, or by an alkali. The most convenient method for showing its action on the vegetable colours is to make a solution of sulphurous acid in water, by transmitting it through this fluid as long as it continues to absorb any. The apparatus represented in Figure 40 may be used for this purpose, or the beak of a retort, from which sulphurous acid is issuing, may be introduced into a glass or bottle containing water, which will soon become sufficiently impregnated with it. The best apparatus, however, for this purpose is a series of bottles connected with a retort in which the gas is gene- rated, and known by the name of Woulfe's Apparatus. The 6 74 SULPHUROUS ACID. gas from the retort passes from the first bottle into the second by a tube which dips under water, and the excess may be conducted into another bottle, as is seen in the annexed Fig. 40. Figure (40), or through a series of them connect- ed with one ano- ther in the same manner as the first is connected with the second. Should the sulphurous acid cease to come before the water has been saturated, it will continue to absorb the portion which still remains above it, and the pressure of the atmosphere acting upon the surface of the liquid in the third bottle may cause it to pass by the tube b into the second bottle, and by the tube a into the first. To prevent this, which would derange the whole apparatus, safety tubes c, c, are put into the bottles, which admit atmospheric air when an absorption of gas takes place till the equilibrium is again restored, and prevents the liquid passing from the one bottle to the other. These tubes must all be fitted tightly to the tubulures of the different bottles, either by passing them through corks, or having them accurately ground to one ano- ther. A still better method is to join the connecting tubes to the tubulures, as Mr. Faraday has recommended, by small caoutchouc tubes or collars, the upper edge being tied round the tube, and the lower part round the tubulure of the bottle. The different bottles then admit of a considerable degree of lateral motion. This apparatus is used for a great variety of other pur- poses, which will be mentioned afterwards. 178. The solution of sulphurous acid, prepared in this man- ner, often contains a small portion of sulphuric acid, which must be carefully neutralized by a little potash or soda (in solution), adding it drop by drop till it can destroy the vege- table blues, which it reddens as long as there is any sul- phuric acid present. 179. A very pure solution of sulphurous acid in water may SULPHURIC ACID. f5 be obtained by heating 100 parts of the black oxide of man- ganese with 15 of sulphur in an iron bottle or gun barrel, (Fig. 14) placed in the open fire, and transmitting it through water, the sulphur combining with part of the oxygen of the oxide to form sulphurous acid. 180. These solutions soon pass into sulphuric acid when exposed to the air, but may be kept for years in stoppered bottles, with little or no change. Sulphurous acid attracts oxygen from a number of metallic oxides, as gold and mer- cury, precipitating them in the metallic form. Its salts are all decomposed with effervescence by the stronger acids ; when exposed to air and moisture, they attract oxygen, like the acid itself, and become sulphates. Sect. II. — Sulphuric Acid. Equivalent by weight 40, (oxygen 24+16 sulphur,) Equivalent of common sulphuric acid 49, (dry acid 40 + 9 water ;) specific gravity 1.845. It boils at 590, when the acid and water rise together, and may be condensed without undergoing any change. 181. Sulphuric acid is seldom or never prepared on the small scale, large quantities of it being manufactured in this country and on the continent, as objects of commerce. The processes by which it is obtained, consist in exposing sulphate of iron to heat in close vessels when it is distilled over and collected in a receiver, or in oxygenating sulphurous acid by the action of nitrous or nitric acid. 182. In the first process, the water of crystallization in the crystallized sulphates is, in a great measure, expelled by heat- ing it over the fire, and the acid procured in the subsequent stages of the operation, consists of two equivalents of dry sul- phuric acid, (80.) combined with one of water. It usually contains a small quantity of sulphurous acid derived from the decomposition of a portion of sulphuric acid, caused partly ^(> StlLPHURIG ACID- by the high temperature and partly by the protoxide in tftd sulphate attracting an additional quantity of oxygen. In this state, it is known by the name of glacial oil of vitriol, or the fuming sulphuric acid of Nordhausen, from a manufactory of it at that place which has now been carried on for a long time. Its specific gravity varies from about 1.80 to 1.98 ; it emits fumes when exposed to the air, makes a hissing noise when dropped into water, and boils at about 100 of F* When exposed to a very gentle heat in a glass retort connect- ed with a receiver kept cold by ice or snow, nothing comes over but real sulphuric acid, which is condensed in the receiver, and may be obtained in the solid form by stopping the distil- lation before any of the water begins to come along with it. 183. Anhydrous sulphuric acid emits copious fumes on exposure to the air, it is very tough, and converted into com- mon sulphuric acid by adding the proper quantity of water* It becomes liquid at 68, and boils at a much lower tempera- ture in its pure state, (about 120,) than when combined with water. 184. The second process, however, is that which has been most generally adopted for the preparation of this acid. Eight or nine parts of sulphur are mixed with one of nitre, and the mixture burned in a large room or chamber lined on every side with lead, and covered to the depth of several inches with water. The sulphur is converted into sulphurous acid during its combustion, and a portion of it into sulphuric acid by com- bining with some of the oxygen of the nitre, nitrous acid and nitric oxide being disengaged ; the sulphurous acid combines with the nitrous acid, and some watery vapour forming a cry- stalline compound which is decomposed by the water at the bottom of the chamber, being converted into sulphuric acid which remains in combination with the water and nitric oxide gas, (deutoxide of nitrogen,) which is disengaged. All the nitric oxide, (which is a light gas,) rises in the chamber, and mixing with a fresh quantity of atmospheric air, combines with the oxygen and forms a dense ruddy vapour, (nitrous acid,) which immediately falls down in consequence of its great spe- SULlfHUKIC ACID. 77 cific gravity, and meeting with more sulphurous acid and watery vapour, a crystalline compound is again formed, which is resolved asrbefore into sulphuric acid and nitric oxide. In this manner a smaU quantity of nitre may be made to com- municate or hand over as it were a large quantity of oxyo-en from the air to the sulphurous acid, and the same series of combinations and decompositions is made to go on till the water at the bottom of the chamber has become strongly acid. It is then boiled in leaden vessels to expel a part of the water, and the concentration finished in large glass retorts heated in a sand bath. The following diagram exhibits more distinctly the nature of the reaction that takes place between the sulphurous and nitrous acid, when the crystalline compound which they form with water is decompsoed by a large quantity of this fluid, the part to the left showing the elementary composition of nitrous acid, &c. and the other the compounds resulting from its decomposition. Nit. 14 -----^ 30 n it r i c oxide. Ox. 8 --'-;;;>'' Nitrous acid -J Ox. 8 '" J Ox. [Ox. Sulphurous acid . 32 — ^/ Vss * 40 sulphuric acid. Sulphurous acid . 32 — ^ 40 sulphuric acid. Hence, one equivalent of nitrous acid is sufficient to con- vert two of sulphurous acid into sulphuric acid, and one of nitric oxide is disengaged. 185. In some manufactories, instead of mixing the sulphur with nitre, the nitrous acid which is disengaged during the conversion of sugar into oxalic acid by nitric acid is employed to convert the sulphurous into sulphuric acid. The theory of the preparation of sulphuric acid may be illustrated very beau- tifully on the small scale by making sulphurous acid and ni- trous acid gases meet together in a glass vessel, in the manner 78 SULPHURIC ACID. Fig. 41. shown in Fig. 41, the sulphurous acid being prepared in this case, however, not by the combustion of sul- phur, but by the de- composition of sul- phuric acid. Into one of the small re- torts, (which should be large enough to hold about three or four ounces of water when full,) put 400 grains of mercury, and six drachms, (water measure,) of sulphuric acid, and into the other 80 or 90 grains of sugar. Heat the first retort by a chauffer, and when the sulphurous acid begins to come, pour four drachms of nitric acid over the sugar, previously dilut- ed with an equal bulk of water, and heat the retort gently till the nitrous acid fumes begins to come over, (which are formed by. the sugar attracting oxygen from the nitric acid.) When the gases meet in the large bottle, (into which the re- torts are fixed by being ground to the tubulures, or having their beaks passed through corks,) a crystalline compound will be deposited on the sides of the vessel in beautiful dendritical crystals, which often cover its whole internal surface. Remove the retorts when either the sulphurous or nitrous acid ceases to come over, and pour a little water into the bottle ; a brisk effervescence will immediately take place wherever it comes in contact with the crystalline compound, which is resolved into nitric oxide and sulphuric acid, the former producing ruddy coloured fumes as it comes into contact with the air. In all these processes a little watery vapour must be present in the gases, as sulphurous and nitrous acids do not act on each other when they arc perfectly dry. In this experiment, the water, SULPHURIC ACID. 79 from the diluted acid, which the nitrous acid vapours carry along with them, is sufficient for the purpose. 186. Pure sulphuric acid, or hydro- sulphuric acid as it has been termed, from the water which is usually combined with it, is transparent, colourless, and inodorous, and has a thick oily appearance when poured from one vessel to another. It is very acid and corrosive, reddens the vegetable blues, and tastes extremely sour, even when diluted with a very large quantity of water. It absorbs this fluid rapidly from the air, and combines with it in all proportions ; a considerable eleva- tion of temperature attends the combination ; this experi- ment, accordingly, must not be made in a thick glass vessel. The degree of condensation may be easily seen by pouring sulphuric acid into a long glass tube till it is about half full, filling it gently with water, emptying it into a jug or thin glass flask, and returning it to the tube when cold. The di- minution of volume which ensues marks the degree of conden- sation which has taken place. One part of water by weight mixed with five of acid, causes their temperature to rise from 50 to 300, according to Dr. Ure. With one part of ice, and the same quantity of acid, the temperature rises to 212 ; but with four of ice to one of acid it falls below zero. As it is important to know the quantity of real acid in diluted sul- phuric acid of different densities, I have inserted the follow- ing useful table drawn up by Dr. Ure. 80 SULPHUItIC ACID. Table of Sulphuric acid by Dr. Ure, showing the quantity of hydrosulphuric or liquid acid (composed of acid 40 -f 9 water,) and dry acid which it contains at different den-> sities. ■e ■a . 2 • . Specific gravity. 3-C J a Dry acid. Specific gravity. 3 * Dry acid Specific gravity. 3" Dry acid. 1.848,? .100 81.54 1.5503 66 53.82 1.2334 32 26.09 1.847£ » 99 80.72 1.5390 65 53.00 1.2260 31 25.28 1.846C 98 79.90 1.5280 64 52.18 1.2184 30 24.46 1.843S 97 79.09 1.5170 63 51.37 1.2108 29 23.65 1.841C 96 78.28 1.5066 62 50.55 1.2032 28 22.83 1.8376 95 77.46 1.4960 61 49.74 1.1956 27 22.01 1.8336 94 76.65 1.4S60 60 48.92 1.1876 26 21.20 1.8290 93 75.63 1.4760 59 48.11 1.1792 25 20.38 1.8233 92 75.02 1.4660 58 47 29 1.1706 24 19.57 1.8179 91 74.20 1.4560 57 46.48 1.1626 23 18.75 1.8115 90 73.39 1.4460 56 45.66 1.1549 22 17.94 1.8043 89 72.57 1.4360 55 44.85 1.1480 21 17.12 1.7962 88 71.75 1.4265 54 44.03 1.1410 20 16.31 1.7870 87 70.94 1.4170 53 43.22 1.1330 19 15.49 1.7774 86 70.12 1.4073 52 42.40 1.1246 18 14.68 1.7673 85 69.31 1.3977 51 41.58 1.1165 17 13.86 1.7570 84 68.49 1.3884 50 40.77 1.1090 16 13.05 1.7465 83 67.68 1.3788 49 39.95 1.1019 15 12.23 1.7360 82 66.86 1.3697 48 39.14 1.0953 14 11.60 1.7245 81 66.05 1.3612 47 38.32 1.0887 13 10.41 1.7120 80 65.23 1.3530 46 37.51 1.0809 12 9.78 1.6993 79 64.42 1.3440 45 36.69 1-0743 11 8.97 1.6870 78 63.60 1.3345 44 35.88 1.06S2 10 8.15 1.6750 77 62.78 1.3255 43 35.06 1.0614 9 7.34 1.6630 76 61.97 1.3165 42 3425 1.0544 8 6.52 1.6520 75 61.15 1.3080 41 3343 1.0477 7 5.71 1.6415 74 60.34 1.2999 40 32.61 1.0105 6 4.89 1.6321 73 59.52 1.2913 39 31.80 1.0336 5 4.08 1.6204 72 58.71 1.2826 38 30.98 1.0268 4 3.26 1.6090 71 57.89 1.2740 37 30.17 1.0206 3 2.446 1.5975 70 57.08 1 .2654 36 29.35 1.0140 2 1.63 1.5868 69 56.26 1.2572 35 28.54 1.0074 1 0.8154 1.5760 68 55.45 1.2490 34 27.72 1.5648 67 54.63 1.2409 33 26.91 187- Sulphuric acid has a great affinity for the different salifiable bases, and can disengage almost all the other acids from their combinations with them. It forms soluble com- pounds with the alkalis, but with most of the earths, especi- ally bary^s, the compounds which it forms are very insoluble. SULPHURIC ACID. 81 Hence barytes is generally employed as a test of the presence of sulphuric acid, giving a copious white precipitate in all solutions containing it either in a free state or combined with other substances. 188. The different sulphates may be formed by bringing sulphuric acid into contact with their respective bases, great heat being in general produced, so that they must be mixed cautiously together. Some of these are extensively distribut- ed throughout the globe, as the sulphate of lime, and many are prepared in large quantities by artificial operations. The metallic sulphates are decomposed by a red heat, but the earthy and alkaline sulphates resist the action of a much higher temperature ; all the latter may be decomposed by heating them along with charcoal, or passing a stream of hydrogen gas over them at a high temperature, the oxygen both of the sulphuric acid and of the metallic oxide being withdrawn, and a metallic sulphuret remaining. These de- compose water, the sulphur combining with the hydrogen and the metal with the oxygen, forming hydros ulphurets, which are dissolved when a sufficient quantity of water is employed. 189- Sulphuric acid freezes at — 15 in the state it is usually met with in commerce, but if diluted with water so as to have a specific gravity of 1-78, it shoots into large crystals when placed in snow or ice, and will remain in a solid form if not exposed to a temperature above 44. If the quantity of water is increased it requires a much lower temperature to cause it to congeal. 190. By passing sulphuric acid in vapour through a red hot porcelain tube, in the manner already described under nitric acid, it is resolved into sulphurous acid and oxygen ; and if these gases are returned through the tube, they will unite and form sulphuric acid, a fact that will not appear so improbable when we reflect on the numerous circumstances by which chemical action is influenced. There are numerous instances also where an action of a similar kind occurs. Thus, water may be decomposed by electricity, and its elements again combined by the same agent so as to form water ; if a G 82 SULPHURIC ACID. stream of hydrogen gas be transmitted over the oxide of iron at a red heat, it will combine with the oxygen, and water will be produced ; and by transmitting watery vapour over the metallic iron that remains still at a red heat, hydrogen gas may be procured, the oxygen of the water combining with the iron. 191. The sulphuric acid of commerce is never in a state of absolute purity, being always contaminated with a small quan- tity of sulphate of potash and sulphate of lead, it is the latter that causes the common sulphuric acid to become turbid when diluted with water, sulphate of lead being insoluble in water or diluted sulphuric acid, though the strong acid can dissolve a small quantity. The only method of obtaining the sulphu- ric acid perfectly pure is by distillation, a process that requires some precautions in consequence of the small quantity of ca- loric which becomes latent when this acid passes to the gase- ous state causing the ebullition to take place suddenly, and producing violent succussions which frequently break the re- tort. The best method is to fill a retort about one-third full of acid, placing the beak within a long glass tube which is introduced into a receiver ; Fig. 27 shows the general arrange- ment of the apparatus, but the tube should be longer in pro- portion than represented there, the retort plain or tubulated, and heat applied by a good charcoal chauffer. It is not ne- cessary to keep the tube cold by water, as the acid gives out as little heat during its condensation as it takes up when con- verted into vapour. To prevent the succussions from taking place, which would almost certainly break the retort, put seve- ral pieces of platina wire, or foil, into the retort along with the acid ; fragments of glass may be taken when these are not at hand. The quantity of impurities may be ascertained by boiling a given weight of the sulphuric acid to dryness in a glass or platina capsule. 192. There are few agents that are so extensively employed in chemical operations as sulphuric acid. Sometimes it is used to form important combinations, or to disengage one of the ingredients of a compound by the great affinity which it HYPOSULPHUROUS AND HYPOSULPHURIC ACIDS. 83 has to the other; often for the preparation of sulphurous acid, in bleaching, dyeing, in making freezing mixtures, and in com- municating oxygen to a variety of substances. Sect. III. — Hyposulphurous and Hyposulphuric Acid. 193. These acids are comparatively of much less import- ance than those which have been already considered ; their composition, according to the most recent analyses has been stated at page 70- 194. Hyposulphurous Acid may be formed by digesting sulphur in a solution of a sulphite (a compound of sulphurous acid and a salifiable base,) the two equivalents of oxygen in the sulphurous acid combining with an additional quantity of sulphur, and being thereby converted into two equivalents of hypo-sulphurous acid. It is not easy to procure this acid in a free state, as it is almost immediately decomposed by the reaction of its elements when detached from the base with which it is combined. Hypo-sulphurous acid is distinguished by the peculiar relation which it has to the oxide of silver, combining with it in preference to soda, which is easily sepa- rated from this acid by the oxide, the only instance where a metallic oxide can separate a fixed alkali from an acid, with- out the aid of some other affinity. The hyposulphite of soda dissolves chloride of silver, forming a compound which has a very intense sweet taste, not accompanied by any disagreeable astringency, or any thing that could indicate the presence of a metal. 195. The Hyposulphuric Acid is prepared by transmitting sulphurous acid through water in which finely powdered per- oxide of manganese has been suspended, a portion of the oxygen of the oxide combining with some of the sulphurous acid and forming sulphuric acid, part of which unites with the remaining sulphurous acid, by which the hypo-sulphuric acid is produced. Both acids remain in combination with oxide of manganese, and by adding barytes, it is precipitated, the sul- phuric acid being also thrown down in combination with part of 84 SULPHURETED HYDROGEN. the barytes, while the hypo-sulphuric acid unites with the rest, and remains in solution. By cautiously adding sulphuric acid to this solution, the barytes is removed, and the hypo-sulphu- ric acid remains in solution. It has not been procured free from water, and is resolved into sulphurous and sulphuric acids when exposed to heat. Sect. IV. — Sulphureted Hydrogen. Equivalent by weight 17 ; by volume □ (one measure). Specific gravity 1.1805. Weight of 100 cubic inches 36.006 grains. It is liquified by a pressure of 17 atmos- pheres at 50. 196. Sulphureted hydrogen is most easily procured by pouring sulphuric acid, diluted with three or four parts of water, over sulphuret of iron reduced to small fragments, and collecting the gas that is disengaged in jars over the pneumatic trough. The materials may be put into a retort, or into a bottle with a bent tube adapted to the tubulure ; the appara- tus already described and used for the preparation of hydrogen gas may also be employed here, and when a steady current of gas is required, the bottle represented in Fig. 23, (48) or one constructed on the same principle, will be found very conve- nient. The gas may be made to come over more rapidly by using a stronger acid, and by reducing part of the sulphuret to powder, or by assisting the action by a gentle heat. 197- Several methods have been proposed for preparing the sulphuret of iron. By exposing a bar of iron to a white heat in a furnace or at a smith's forge, and then bringing it in con- tact with a piece of roll sulphur, it is obtained perhaps more conveniently than in any other way. The iron combines im- mediately with the sulphur, forming a liquid which speedily becomes a solid brittle mass, with a metallic lustre ; it is a protosulphuret of iron, and the great superiority of this pro- cess to the others consists in the protosulphuret formed in SULPHURETED HYDltOGEN. 85 this manner containing no metallic iron and no excess of sul- phur ; the former would cause pure hydrogen to be disengaged along with the sulphureted hydrogen. When more than one equivalent of sulphur is combined with one of iron, it does not afford any gas when treated with an acid. The roll sulphur should be placed on a stone and the iron brought in contact with it, gradually bringing them closer and closer to one ano- ther as the sulphuret is formed ; or they may be held over an iron bason filled with water into which the melted sulphuret falls, taking care always to keep the sulphur and iron in con- tact with one another. A shower of sparks is thrown off dur- ing the action, and if the sulphuret is allowed to fall on the ground, it divides into an infinite number of small globules presenting a very beautiful appearance ; most of it, however, is lost when it is allowed to fall to the ground in this manner. The iron must be at a white heat, otherwise it merely melts the sulphur, and causes it to take fire, no sulphuret being formed. The roll sulphur should be wrapped round with some cloth or cotton where it is to be held by the hand, or a glove may be put on to prevent it from falling to pieces. When a long bar of iron cannot be procured, a smaller piece may be held with a pair of pincers, and care must be taken to hold the iron and Fig* 42 - sulphur in the manner represent- ed (Fig. 42) to prevent the liquid sulphuret from running down the iron and reaching the hand. If o the sulphur is applied to the mid- ° die of the bar when it is at a proper temperature, it may be divided into two parts in a few se- conds by pressing the sulphur gently against it. The iron should be taken out of the forge or furnace whenever it has be- come sufficiently hot, as it would be speedily destroyed in the fire at this high temperature. 198. The proto-sulphuret of iron may also be obtained by exposing iron pyrites to heat in a crucible placed in a furnace till the excess of sulphur which it contains has been expelled. When neither of these methods can be conveniently followed, it may be procured by mixing four parts of sulphur with se- 86 SULPHURETED HYDROGEN. ven of iron filings, and exposing the mixture to heat in a dry Florence flask, (which should not be more than a third full,) resting on the red hot cinders in a good chauffer. In a short time the sulphur melts and combines with the iron, a rich red glow of light pervading the whole mass during the combina- tion ; a cork with a small piece cut out at the side (to allow the vapours of sulphur which are formed at first to be disen- gaged) should be put into the neck of the flask, to prevent the free access of the air. The flask need not be kept over the chauffer after the glow of light has begun to appear, and care must be taken not to press the cork too hard in, lest the va- pour of the sulphur, not having room to escape freely, should cause an explosion ; the flask is broken afterwards to get the sulphuret. When it is not desired to see the glow of light at- tending the combination, the mixture may be heated in a co- vered crucible. The sulphuret prepared in this manner al- ways has some metallic iron mixed with it, but the sulphuret- ed hydrogen which it affords is sufficiently pure for all ordi- nary experiments. 199. The theory of the preparation of this gas is very sim- ple. A reaction takes place between every nine parts of wa- ter (one equivalent) and 44 (one equivalent) of the sulphuret of iron, the latter being composed of 16 of sulphur and 28 of iron. The oxygen of the water combines with the iron of the sulphuret, forming oxide of iron, with which one equivalent of the acid unites, converting it into sulphate of iron which re- mains in solution, while the sulphur and the hydrogen com- bine together to form sulphureted hydrogen. The following diagram is intended to illustrate the decomposition. Before Decomposition. After Decomposition. JHyd. 1 ;- 17 sulphureted hydrogen, j water . j Qx ^ 44 sulphuret ( Sulph. 16- of iron . \ Iron 28- 40 sulphuric acid . 40 ^^ 76 sulphate of iron. 93 93 93 SULl'HUUETED HYDKOGEN. 87 Accordingly, 44 parts of the sulphuret will give 17 of sul- phureted hydrogen, and 40 of real sulphuric acid will be re- quired for the action. 200. Instead of diluted sulphuric acid, strong muriatic acid may be used with the sulphuret of iron, and when sulphureted hydrogen is required particularly pure, sulphuret of antimony reduced to powder is mixed with five times its weight of mu- riatic acid, the antimony being oxidated by the water which the acid contains, while the sulphur combining with the hy- drogen that is set at liberty forms the gas that is evolved. It does not appear, indeed, to be purer than that which is ob- tained from the sulphuret of iron as prepared by the first pro- cess described, though it is certainly much purer than when the sulphuret prepared from a mixture of sulphur and iron filings is used. The materials must be heated by a lamp or chauffer when the sulphuret of antimony is employed. 201. This gas has also been procured frequently of late by the action of diluted acids on the sulphurets of potassium and calcium prepared by decomposing the sulphates of potash and lime by charcoal, in the manner that will be explained after- wards ; the same reaction takes place between the diluted acid and the sulphuret of calcium or potassium as has been already described, when the sulphuret of iron or antimony is used. Sulphuric acid must not be used with the sulphuret of cal- cium, as it forms an insoluble compound with lime (oxide of calcium,) which would speedily accumulate and prevent the farther action of the acid on the remaining sulphuret ; muri- atic acid, however, does well, as the muriate of lime is very soluble. Small quantities of sulphureted hydrogen may be obtained by subliming sulphur in hydrogen gas. 202. As sulphureted hydrogen has not only an extremely offensive odour (similar to that of sulphureous mineral waters) but produces severe headache when it is mixed even in small proportion with atmospheric air, none should be allowed to escape into the apartment in which it is prepared. A small quantity, indeed, such as is usually lost during its prepara- tion, will not do any harm ; but where the materials from which it has been procured have been carelessly thrown aside 88 SULfHURETED HYDROGEN. before the gas has ceased to come, it still goes on accumula- ting, and often produces very deleterious effects. I have seen several people very much affected by the gas disengaged, even from a small quantity of materials set aside in a corner of a very large room ; one of them felt so much depressed, that for two days almost he lay in a listless state, and was unable for a long time to hold up his head, after which he gradually recovered. It is indeed much more noxious to animal life than what one would have at rlrst anticipated ; a horse dies in air containing even l-150th of its bulk of this gas, and dogs and smaller animals when the quantity is so small as an l-800dth part ; a small bird died instantly in air containing a l-1500dth part. Chaussier states, that many animals die soon if they are put into bladders full of this gas, though their heads are left out, and they are allowed to breathe at- mospheric air as freely as before- 203. Sulphureted hydrogen burns with a pale blue lam- bent flame when kindled in contact with atmospheric air or oxygen gas. The experiment described with hydrogen gas in 56 may also be performed with sulphureted hydrogen, and indeed with all inflammable gases, taking care to hold the mouth of the jar downwards when the gas is lighter than air, but upwards when it is heavier. During its combustion, the hydrogen combines with the oxygen of the air, forming water, while the sulphur uniting with the same element is converted into sulphurous acid. It is evident from this, that one measure (□) of sulphureted hy- drogen will require a measure and a half ( R—i ) of oxygen for its complete combustion ; for it contains in a condensed state its own bulk of hydrogen (□)> which requires half a measure of oxygen to convert it into water (59), and an equal volume of the vapour of sulphur, with which two equivalents of oxygen (one measure) must be combined to produce sul- phurous acid. The combustion is never complete in atmospheric air, part of the sulphur being always deposited then on the sides of the vessel in which it is inflamed ; when mixed with pure oxygen, however, in the proportion just mentioned, the combustion is SULHIUUETED HYDROGEN. 89 always complete, and a sharp report accompanies the com- bination ; the gases must in this case be mixed in the detona- ting bottle. 204. Water absorbs sulphureted hydrogen readily, taking up more than its own volume of this gas when previously de- prived of air by boiling, and acquiring its peculiar odour. On exposure to the air, part of the sulphureted hydrogen escapes, and the rest is decomposed, the water acquiring an opales- cent appearance from the deposition of a portion of sulphur, or bisulphureted hydrogen. Sulphureted hydrogen reddens the infusion of litmus, and possesses the other properties of an acid. The red tint which it communicates, is not perma- nent, however, from the cause which has just been mention- ed, and if the reddened infusion is boiled, it becomes blue immediately, the gas being expelled, which may be easily seen by heating a small quantity in a Florence flask. Sul- phureted hydrogen water may be kept for years in bottles well corked and sealed ; they ought also to be filled perfectly full. Perhaps the most convenient method of preparing sul- phureted hydrogen water is to fill bottles about two-thirds full with the gas over the pneumatic trough, and to agitate the remaining water briskly with it as long as it continues to ab- sorb any, taking out the cork from time to time to allow at- mospheric air to enter, and supply the place of the gas as it combines with the water. 205. Fuming nitric acid decomposes sulphureted hydrogen, communicating oxygen to the hydrogen, while the sulphur is deposited ; if a piece of thin paper be placed over the bottle containing the gas, whenever the acid is poured in, and the finger pressed very gently upon it so as to prevent any es- caping, the temperature rises so high that the sulphur and any undecomposed sulphureted hydrogen immediately take fire, burning with a beautiful flame, and producing a slight detonation ; the experiment may be performed with a flask or bottle containing a few cubic inches of the gas with perfect safety. It succeeds, it has been affirmed, only when the sul- phureted hydrogen has been prepared by diluted sulphuric acid and sulphuret of iron. yO SULPHDHETED HYDROGEN. 206. Mix three volumes of sulphureted hydrogen, with two of sulphurous acid in a jar over a mercurial trough ; they condense into a solid compound which is the hydro-sulphur- ous acid of Dr. Thomson. It has not been applied to any use. Chlorine, iodine, and bromine decompose this gas, com- bining with the hydrogen and precipitating the sulphur. 207- Sulphureted hydrogen is a very important agent in practical chemistry, forming several salts which are often prepared in large quantities in different stages in the decom- position of sulphates by charcoal, where the salifiable base is required in a pure state, or combined with another acid, as the carbonic, nitric, or muriatic. It is also very much employed as a reagent for detecting a number of the metals, or separa- ting them from solutions containing them, as in the detection of arsenic, where the sulphur unites with the metallic arsenic, forming a rich yellow coloured precipitate, if the liquid under examination contain any. In general the sulphur combines with the metal in solution, forming a metallic sulphuret which is precipitated, while the oxygen previously in combination with the metal goes to the hydrogen of the gas. The sul- phureted hydrogen gas should be transmitted through the liquid to be examined in Woulfe's apparatus, or in one similar to what has been represented in Fig. 37- A bottle with a bent tube adapted to it (which may be done at the blowpipe) will do very well for this purpose, or a small apparatus similar to Woulfe's may be easily constructed for the purpose with some wide-mouthed jars, bottles, or glasses, with corks and bent Fig. 43. tubes, as shown in the annexed fig- ure (43), fixing the corks with a little (c ^ f^^^ wax lute or wax cement if they should not be air tight. A solution of caus- tic potash should be put into the last glass or bottle to condense any excess of sulphureted hydrogen. The long tube is to allow a fresh quantity of \l V acid to be poured on the sulphuret c ^-^ > CrD> when the action becomes feeble, with- out taking out the corks ; it is not necessary, however, and a c* BISULI'HUIIETED HYDKOGEN. 91 Fig. 44. bottle with a bent tube (Fig. 44) adapted to it, is (f^^ all that is required. It should be supported on a block of wood, that it may be easily removed, and more acid added to it if necessary. The solutions of the common metals which it does not decom- pose, are those of iron, nickel, cobalt, manganese, titanium, and molybdenum (Dr. Henry.) The most delicate test of sulphureted hydrogen is car- bonate of lead, which is converted into a sulphuret by the action of this gas, becoming perfectly black. Air containing even a 20,000th part of its bulk of sulphureted hydrogen acts on carbonate of lead, the basis of most white points. 208. The hydrosulphurets (compounds of this acid with the salifiable bases,) may, in general, be formed by passing a stream of a sulphureted hydrogen through a solution of the different bases dissolved or suspended in water, or by indirect processes, where the sulphureted hydrogen and the base are presented to each other in a nascent state ; the most impor- tant will be described under their respective bases. All the hydrosulphurets are decomposed by heat, but the nature of the resulting compound varies according to the base with which the sulphureted hydrogen is combined. Magnesia parts with all its sulphureted hydrogen ; potash and soda give off hydrogen and sulphureted hydrogen, part of the sulphur being retained ; and the hydrosulphurets of manganese, zinc, iron, tin, and antimony, are converted into water and metallic sulphurets. (Dr. Ure.) Sect. V. — Btsulphureted Hydrogen. Equivalent by weight, 33. (Sulphur 32 + 1 Hydrogen.) 209. Bisulphureted hydrogen is prepared by adding a so- lution of the sulphureted hydrosulphuret of potash or lime, to an equal bulk of muriatic acid. These are compounds of bi- sulphureted hydrogen, and their respective bases, with which the muriatic acid combines, and the bisulphureted hydrogen 92 SULPHUKETED HYDROSULPHUltETS. is slowly deposited in the form of a viscid oily -looking sub- stance of a yellow colour. Its smell is disagreeable, it is in- flammable, and is speedily decomposed when gently heated or exposed to the air, sulphureted hydrogen being disengaged, and sulphur deposited. It has not been applied to any use. 210. The sulphureted hydrosulphurets may be prepared by digesting solutions of the hydrosulphurets with flowers of sulphur, rubbing the sulphur with a drop or two of the liquid in a mortar at first, that they may mix more easily together, the sulphur resting on the top of the liquid for a long time, when this precaution is not taken. They may be formed also by mixing sulphur with the earths or alkalis, and boiling them in a Florence flask with water ; two equivalents of the sulphur combining with one of hydrogen, obtained from an equivalent of water, which is decomposed, while the oxygen of the water probably combines with other two of sulphur, forming hyposulphurous acid ; but this has not been satis- factorily ascertained. 211. The colour of these solutions varies from a greenish yellow to a reddish orange. They are distinguished by their disagreeable odour, bitter taste, and by absorbing oxygen readily from the air, or any gaseous mixture containing it ; a property, in consequence of which they have been much employed, in eudiometrical experiments. They are all decom- posed by the acids, and when the solution is dilute, a copious precipitation of sulphur takes place ; and as little or no sul- phureted hydrogen is disengaged, it is likely that on the addition of an acid which has a great affinity for the base con- tained in one of these solutions, that the oxygen of the hydro- sulphurous acid (supposing that to be the compound which the oxygen of the water that is decomposed forms with the sul- phur,) combines with the hydrogen of the bisulphureted hy- drogen, and that the sulphur of both is precipitated. 212. It is in this manner that the precipitated sulphur of the London College is prepared, a sulphureted hydrosulphu- ret of lime being formed by boiling a pound of sulphur with two pounds of lime in four gallons of water, and adding mu- SELENIUM. 93 riatic acid to the liquid which is formed as soon as it has been filtered through paper. The precipitate must be washed with water till it becomes tasteless. When sulphuric acid is used, instead of muriatic acid, with this solution, sulphate of lime is precipitated along with the sulphur, being very insoluble ; but muriatic acid forms a very soluble salt with lime, and re- mains in solution. The Lac Sulphuris (see 166) was usually prepared with the sulphuric acid formerly. Sulphate of lime may be easily de- tected when mixed with sulphur, by exposing a small quantity to heat in a crucible placed in the fire, b* still more easily by the blowpipe ; the sulphur will be entirely dissipated, but any sulphate of lime which may be present will remain. 213. When these solutions absorb oxygen, they lose their disagreeable smell, their colour becomes lighter, and a portion of sulphur is deposited. By long exposure to the air, they become quite colourless, the sulphur being converted into sul- phurous and sulphuric acid. They tarnish the metals, and give precipitates with a number of metallic solutions. They must be kept in bottles well closed with stoppers, or corks made perfectly air-tight with a little wax lute. CHAP. V. SELENIUM. Equivalent by weight 40 ; Specific gravity 4.5. 214. Selenium is an elementary substance, which was dis- covered a few years ago by Berzelius, in sulphur prepared by sublimation from iron pyrites at Fahlun. It has hitherto been obtained only in small quantity, and has not been ap- plied to any use. As it will be seldom made the subject of experiment by those commencing the study of chemistry, it may be sufficient in this place, to refer to the 13th volume of the Annals of Philosophy, where the process for preparing it 94 PHOSPHORUS. is described. — It is a solid substance, of a dark brown colour, and metallic lustre, melts at 220, boils at COO, forming a yellow coloured vapour, which condenses in a powdery form like the flowers of sulphur, but of a red colour. It combines with oxy- gen when heated in the air, producing a strong smell of horse- radish, and forming oxide of selenium and a small quantity of an acid at one time called the selenic acid, but now selenious acid, in consequence of another acid compound having been discovered containing a larger quantity of oxygen than it. 215. The selenic acid bears a great resemblance, in all its chemical habitudes with the different salifiable bases to the sulphuric acid ; and selenium, indeed, in most of its combina- tions, produces compounds analogous to those which sulphur forms with the same substances. 216. Selenium and hydrogen unite together when the selenuret of potassium acts on water, the oxygen of the water combining with the potassium, and forming potash, while the selenium goes to the hydrogen. On adding muriatic acid to the compound of the selenureted hydrogen and the potash which remains, the former is disengaged in the gaseous form, while the muria- tic acid combines with the potash. It possesses all the pro- perties of an acid. CHAP. VI. PHOSPHORUS. Equivalent by weight 12 f Specific gravity 1-7- It melts at 100, and boils at 550. 217. When bones are burnt to whiteness in an open fire, all the animal matter which they contain is destroyed, and no- thing remains but a solid mass of a fine white colour, consist- ing almost entirely of phosphate of lime, a compound of phos- phoric acid and lime. It is from this that phosphorus is usu- ally prepared ; a superphosphate of lime being formed in the PHOSPHORUS. 95 first place, by mixing the phosphate in fine powder with three- fourths of its weight of sulphuric acid, previously diluted with an equal weight of water. The mixture should be made in a large wedgwood mortar, stirring it constantly, and adding water from time to time, till the mass becomes quite fluid and uniform. The sulphuric acid combines with the greater part of the lime, and the phosphoric acid set at liberty, attaches itself to a portion of the phosphate which is not decomposed, forming superphosphate of lime, which remains in solution. After the mixture has been kept for a day or two, stirring it frequently, and adding more water to keep it quite thin, it is put into a linen bag. The superphosphate of lime, which is dissolved by the water, filters into a receiver placed below, while the sul- phate of lime remains. More water is poured upon it as long as the liquor which passes through contains much acid, and the mixed solutions evaporated till they assume a syrupy consistence, when they are to be mixed with as much powder- ed charcoal as may render them solid. On exposing this in an earthen retort to a strong heat in a furnace, phosphorus is dis- engaged, and as it is easily volatilized, it may be collected by connecting the beak of the retort with a tin tube which is made to dip in water. 218. In conducting this operation, a very large quantity of gas is disengaged, which inflames when it comes in contact with the air, and the phosphorus congeals occasionally in the tin tube, or the neck of the retort, preventing the farther escape of gas. To prevent accident, it should be immediately melted by a chauffer or shovel of red hot cinders held below the part where the stoppage is supposed to have taken place. The materials should be well dried by exposure to heat in an iron ladle or crucible placed over an open fire, before they are put into the retort, to prevent them from swelling and boiling over. The retort should be coated with Willis's lute, which prevents a great part of the phosphorus from passing through the pores of the retort, through which it easily forces its way at a high temperature when this precaution is not adopted. The superphosphate of lime does better for the pre- 96 PHOSPHORUS. paration of phosphorus than pure phosphoric acid, as it is not so apt to be volatilized. 219. In this process the carbon combines with the oxygen of the phosphoric acid, and forms part of the gaseous products which are disengaged ; phosphureted hydrogen gas is also pro- duced by the combination of a portion of phosphorus with some of the hydrogen of the water that is always united with this acid, when prepared in the manner that has been describ- ed. 220. If it is required merely to illustrate the principle on which phosphorus is prepared, and not to procure any quantity of it, which may now be always purchased from the manufac- turer, thirty or fifty grains of a mixture of phosphoric acid, (or the superphosphate of lime prepared in the manner just mentioned,) with half its weight of charcoal may be put into a glass tube sealed at one end, about a foot in length and half an inch in diameter. The tube should be coated with a mix- ture of two parts of clay and one of sand, previously mixed with cut thread or flax, and then wrapped round with iron wire. The coating need not extend farther than an inch be- yond the part to which the mixture reaches when it has been introduced, as this alone is to be exposed to heat. It is placed in a chauffer with a hole cut in the side, in the manner shown in the annexed figure, and a chimney placed over it (15) to Fig. 45. increase the heat ; the tube should be gent- ery vapour that may be disengaged and con- •gffi^SSf densed on its sides, and the end which is not V— 5— — 5 coated had better be drawn out at the blow- pipe when the mixture has been put in, till it is about a quar- ter or an eighth of an inch in diameter. A green glass tube is much better than one made of flint glass, as it is not so easi- ly melted. A mixture of red hot cinders and charcoal gives the best fire for this experiment. The phosphorus soon be- gins to come, condensing along the sides of the tube, and a flame appears at the open end, similar to what is produced by the combustion of phosphorous. If the tube is broken off" I PHOSPHORUS. 97 above the point where it is coated, after gas ceases to be dis- engaged, on blowing through it, the phosphorus will immedi- ately take fire and burn with a vivid light. 221. Phosphorus was formerly prepared from urine, by ex- posing it when evaporated to dryness to a high temperature, the carbon of the animal matter decomposing the phosphoric acid which it also contains. By adding a solution of the ni- trate of lead to it, phosphate of lead is precipitated, which yields it more readily, when mixed with about a fourth of its weight of charcoal. The same compound may be obtained by adding a solution of the phosphate of soda to a solution of the acetate of lead, phosphate of lead being thrown down, and ace- tate of soda remaining in solution. 222. The phosphorus obtained in these processes is never pure, having a reddish brown colour which arises from the pre- sence of some phosphuret of carbon formed during the distil- lation. It is purified most effectually by a second distillation, but for ordinary purposes it will be sufficient to melt it in hot water and press it through chamois leather under water. The distillation of phosphorus may be conducted in a small glass retort, the phosphorus being covered with water to the depth of about a quarter of an inch before applying heat, and the beak of the retort inserted into a receiver containing a small quantity of water, and dipping under its surface. A strong and steady heat is then applied to the bottom of the retort by an argand or common spirit lamp ; the phosphorus is melted, the water boils and is condensed in the receiver by the cold water, which soon becomes heated to the temperature of 212, and is thereby not so liable to be forced back into the retort when all the water has been distilled over. The heat should then be gradually increased by bringing the lamp nearer the bottom of the retort, and the phosphorus is speedily volatilized, condensing in the neck of the retort and dropping into the re- ceiver. When the last portion of phosphorus is converted in- to vapour, the beak of the retort may be lifted out of the wa- ter in the receiver, and placed in a small cup or saucer with a little hot water in it, (no more than is sufficient to cover the beak) and in the same manner as the retort for preparing ni- H 98 PHOSPHORUS, trous oxide (103. Fig. 30.) All this time the lamp must not be shifted, and the heat maintained as steadily as before ; but when the retort has been adjusted in the manner described, the heat may be withdrawn. The vapour of phosphorus still remaining in the retort soon condenses ; the water rises in the neck, but as the quantity is so small, atmospheric air imme- diately enters before it has proceeded far, when it again falls, and continues rising and falling till the retort has become cold. The small quantity of air which enters in this manner at a time prevents any violent action taking place, its oxygen combines with some of the phosphorus still remaining in the retort ; a lambent phosphorescent flame appearing in the neck, and at last the retort is filled with nitrogen gas. When cold, the phosphorus adhering to the neck may be removed by boiling more water in it, but this must not be mixed with the rest, as it contains the most of the phosphuret of carbon, which gene- rally condenses in the neck, forming a crust of a beautiful rich; red colour. I prefer conducting the distillation of phosphorus in this manner to filling the retort full with water after the phospho- rus to be distilled has been introduced, and replacing it by hydrogen or nitrogen gas. 223. The phosphorus obtained by distillation is transparent, and has little or no colour. It may be procured in the form of sticks by pouring it when melted in hot water into glass tubes slightly tapered and closed at one end by a cork ; the tube must also be placed in hot water, the phosphorus being heavier than this liquid sinks in the tube and displaces the water. It is of a waxy consistency at natural temperatures, and may be easily cut with a knife. 224. In all experiments with phosphorus, great care must be taken not to allow it to come in contact with air when melted or exposed even to a very gentle heat, if it is not re- quired to kindle it, as it takes fire then, even when gently pressed between the fingers, or when heated a very little above its melting point. It ought also to be cut under water, as it frequently takes fire when cut in the open air, and should ne- ver be held by the fingers.; Accidents are continually taking phosphorus. 99 place from not attending to these precautions. It must be kept in bottles filled with water, and should not be exposed to the light, as it then soon acquires a crust upon its surface. When phosphorus is to be inflamed in atmospheric air or oxy- gen gas, it must always be well dried on blotting or filtering paper, which prevents it from throwing out sparks. 225. Phosphorus appears luminous in the dark when sur- rounded by atmospheric air, and traces drawn on the wall with it present a beautiful phosphorescent appearance ; a bason of water should always be at hand when this is done, in case the friction should cause it to take fire. It appears that this lumi- nousness depends upon a small portion of phosphorus being dissolved by the nitrogen of the air, which combines with the oxygen when in this minute state of division ; for when phos- phorus is enclosed in a jar with pure oxygen, little or no action takes place at ordinary temperatures. When water is boiled with a little phosphorus, part of it rises in vapour along with the steam and renders it luminous when it comes in contact with the air ; if the steam is made to issue from a small aper- ture it presents a luminous cone which is incapable of in- flaming any combustible matter. Phosphorus is insoluble in water, but is dissolved by alcohol, ether, and fixed and volatile oils. The solutions are affected easily by heating these differ- ent liquids with the phosphorus in a flask. They are luminous in the dark when exposed to the air. 226. When phosphorus is inflamed in atmospheric air, a large quantity of white fumes are formed, which may be col- lected by including the phosphorus in a glass jar. These con- sist of dry phosphoric acid formed by the combination of the phosphorus with the oxygen of the air, falling down in the jar like flakes of snow. Great heat and light are produced during its combustion. The apparatus represented in page 37, Fig- 93, may be used for this purpose, placing it upon a brass plate which ought to be perfectly dry, as the phosphoric acid is extremely deliquescent. 227. When phosphorus is burnt in oxygen gas, the combus- tion is very brilliant, and ai. intense dazzling light is produc- ed, which, however, is of short duration. The phosphorus 100 PHOSPHORUS. (previously well dried) may be placed in a copper cup sus- pended by a wire, from a small plate of copper, (Fig. 32, page 48,) and kindled by touching it with a hot wire when it has been put into a bottle or vase filled with oxygen. When a very large quantity of gas is used, a vessel made in the man- Fig. 45. ner represented in the figure, (45) will be found vpnrv very convenient. It is filled with water after Q putting a cork into the opening at the top, placed on the shelf of a large pneumatic trough, in the same manner as ajar, and oxygen gas introduced by the lower aperture. When quite full, it is allowed to drain, removed on a flat plate of brass and placed over a small cup containing the phosphorus ; sand to the depth of half an inch being placed where the jar is to rest. The cork is then taken out, and a thin plate of copper placed over the top, after the phosphorus has been kindled by an iron wire ; the copper plate allows part of the oxygen to es- cape freely when expanded by the heat ; corks should never be put in during the combustion, as they are generally set on fire ; and, if part of the expanded air cannot get out easily in consequence of the cork getting fixed, the apparatus will in general be blown to pieces. It is often broken, also, when a large quantity of phosphorus is employed. 100 cubic inches of oxygen can combine with about 24 grains of phosphorus, but less than half this quantity will be sufficient. 228. Phosphorus may be inflamed under water by driving a stream of oxygen upon it after putting a few grains into a glass and pouring boilingwater over it till it is half full. The oxygen should be made to issue from a small brass nozzle held in con- tact with the melted phosphorus, and connected with the gasometer (or a bladder containing oxygen) by a flexible tube. The aperture at the pointed extremity of the nozzle need not be larger than l-50th of an inch. 229. Phosphorus burns also in nitric and nitrous oxides, and in chlorine with a pale flame. 230. If a thin piece of phosphorus is dried, folded in paper, and rubbed with a piece of wood or any solid substance, it will immediately take fire. 3 PHOSPHOROUS AND HYPOPHOSPHOROUS ACIDS. 101 231. Nothing but phosphoric acid is formed during the combustion of phosphorus in oxygen gas, but when it is heat- ed in air which has been rarefied to a very great degree, or inflamed in a limited quantity of atmospheric air not suffici- ent to supply oxygen for its combustion, both phosphorous and phosphoric acids are formed, and these are also mixed with another substance of a red colour, the precise composi- tion of which has not been accurately ascertained, it is gene- rally considered as a compound of phophorus containing a smaller proportion of oxygen than phosphorous acid. 232. The number representing the chemical equivalent of phosphorus which I have adopted is 12, but this has not yet been satisfactorily determined. The same remark may be made, perhaps, with respect to the other compounds of phos- phorus, and the whole subject requires further investigation. The following table shows the composition of the most impor- tant compounds it forms with oxygen and hydrogen, and the equivalent numbers which Dr. Thomson has adopted in his Principles of Chemistry. Phosphorous acid Phophoric acid Hydruret of phosphorus . Bihydruret of phosphorus Sect. I. — Phosphorous and Hypophosphorous Acids. 233. The Hypophosphorous Acid is the least important of the compounds of oxygen and phosphorus, and contains the smallest quantity of oxygen. It is directed to be prepared by digesting phosphuret of barytes in water, when two new com- pounds are formed, phosphate of barytes, which is insoluble, and hypophosphite of barytes, which remains in solution ; they are separated by filtration, and the barytes thrown down from the filtered liquid by sulphuric acid. The solution of the hypophosphorous ^cid which remains is then concentrated by Ox. Phos. 8 + 12 — 20 16 ttfrt + 12 = 28 xlyu. 1 + 12 — 13 2 + 12 = 14 102 PHOSPHORIC ACID. evaporation till a thick viscid fluid is obtained. It deoxi- dates a great number of substances and precipitates several of the metals in the metallic form from their solutions, combin- ing with their oxygen and passing to a higher state of oxida- tion. It has been regarded as a compound of two equivalents of phosphorus with one of oxygen. 234. Phosphorous Acid is formed when phosphorus is in- flamed in a smaller quantity of air than is necessary for its rapid combustion, and even when phosphorus is exposed to the air at natural temperatures, mixed, however, in both these cases with phosphoric acid. The process which is best adapt- ed for preparing it in a pure state, was pointed out by Sir H. Davy. A piece of dry phosphorus is put into a tube retort, and some of the bichloride of mercury in powder placed over it. On exposing the retort to heat, the phosphorus, as it rises in vapour through the bichloride, takes one proportion of chlorine from it, and a limpid fluid condenses in the re- ceiver, the protochloride of phosphorus. On mixing it with water, they mutually decompose each other, the chlorine com- bining with the hydrogen of a portion of the water, and form- ing muriatic acid, while the phosphorus takes the oxygen, and is converted into phosphorous acid ; by heating the liquid till it becomes of a thick consistence, all the muriatic acid, and most of the water is driven off, and the phosphorous acid still combined with a portion of water, becomes a solid crystalline mass on cooling. 23-5. It has a sour taste and a disagreeable fetid smell. It reddens the vegetable blues, and when exposed to heat it is decomposed, a portion of phosphorus being disengaged, and phosphoric acid remaining. Sect. II. — Piiosphokic Actd. Equivalent, 28 f (Oxygen 16 + 12 Phosphorus.) 23G. Phosphoric acid is prepared most easily by burning phosphorus in atmospheric air, in the manner already de- PHOSPHORIC ACID. 103 scribed, (226) taking care to use no more phosphorus than can burn freely in it, to prevent the formation of phosphorous acid. It falls down in the form of a large bulky powder, very like snow, and must be immediately put into a stoppered bot- tle, as it is extremely deliquescent. 237. This is an expensive process, however, and is never resorted to except for the purpose of experimental illustration ; the acid is usually procured from the solution of the super- phosphate of lime, (217) which always contains a small quan- tity of the sulphate, when prepared from the phosphate by sulphuric acid. Carbonate of ammonia is added to this liquid till it is completely neutralized, and as long as any precipita- tion takes place ; the excess of phosphoric acid combines with the ammonia, forming phosphate of ammonia, and disengag- ing carbonic acid with effervescence, while the phosphate of lime previously retained in solution by the excess of acid is precipitated. The sulphate of lime is at the same time decom- posed by another portion of the carbonate of ammonia, carbo- nate of lime being thrown down, and sulphate of ammonia remaining in the solution along with the phosphate of ammonia. After concentrating the liquid by evaporation, the phosphate of ammonia crystallizes, still mixed with the sulphate of ammo- nia, and on melting these in silver or platina crucibles, the sulphate of ammonia is volatilized, and the ammonia of the phosphate at the same time expelled. The phosphoric acid is melted, forming a transparent and colourless glass as it cools. In this state Berthier affirms that it still contains one-fourth of its weight of water. 238. If the solution of the superphosphate of lime is eva- porated as it is procured at first, a solid substance is obtained, similar in appearance to the glacial phosphoric acid procured in the manner which we have just described ; it is evident, however, that it must be contaminated with phosphate and sulphate of lime, and if the evaporation has been conducted in glass or earthen vessels, and the dry mass fused in an earthen vessel, it will contain a still greater quantity of impurities, as phosphoric acid acts both on glass and earthen vessels when its solution in water i3 concentrated, or when it is fused by 104 PHOSPHURETED HYDROGEN. exposure to heat. For a great many purposes where phos- phoric acid is required, the solution of the superphosphate of lime may be employed instead of the purified phosphoric acid. Phosphoric acid may be formed also by dropping small pieces of phosphorus at a time through a tube into a tubulated retort filled half full of nitric acid, and continuing to add it till no more is dissolved ; the acid should be heated gently by a lamp or chauffer. The phosphorus takes oxygen from the acid, and a large quantity of nitric oxide is disengaged, which may be collected over the pneumatic trough ; when a suffi- cient quantity has been added, the phosphoric acid may be ob- tained in the solid form by evaporating the liquid in the retort, and fusing the dry mass afterwards in a crucible. 239. Phosphoric acid is sublimed by exposure to heat in close vessels, but when combined with a small quantity of water, it cannot be volatilized. It is very soluble in water and de- liquescent, tastes extremely sour, but is not corrosive, it reddens the vegetable blues. It is not easily crystallized, and yields phosphorus when heated along with inflammable matter. It acts upon silica and most vessels containing this earth. With the different salifiable bases it forms an important class of salts, the exact composition of which, like that of the other compounds of phosphorus, still requires further investigation* What was formerly called phosphatic acid, formed by expose ing phosphorus to a moist atmosphere, has now been found to be a mixture of phosphorus and phosphoric acids. Sect. III.- — Hydruret of Phosphokus, or Phosphur- eted Hydrogen. Equivalent 13 f. specific gravity 0.9722 ? weight o/lOO cubic inches 27.5 grains, 240. There are two compounds of phosphorus and hydro- gen, whose composition and chemical equivalents, according to Dr. Thomson, have been represented in page 101. The first of these is termed hydruret of phosphorus, and is usually PREPARATION OF PHOSPHURETED HYDROGEN. 105 known by the name of phosphureted or perphosphureted hy- drogen ; the other contains a larger quantity of hydrogen, and has been called the bihydruret of phosphorus, from its sup- posed atomic composition. Both these exist in the gaseous state, and the hydruret is distinguished by taking fire when it comes in contact with air or oxygen, and producing beautiful rings or wreaths of white smoke during combustion, if the at- mosphere is calm, which gradually increase as they ascend in the air. 241. There are two processes for preparing this gas. The first consists in mixing small pieces of phosphorus with water and potash or lime, and exposing the mixture to heat in a glass or metallic retort. With lime the gas comes away slow- ly and steadily, when it begins to be disengaged, but with potash it is evolved much more rapidly, and more care is re- quired in conducting the process. With a large quantity of water, the gas is long in coming, as the materials do not act upon one another, till the most of it has been expelled. Forty grains of phosphorus, 50 of caustic potash, and 60 drops of water, give this gas very readily when gently heated in a small retort (capable of holding an ounce and a half or two ounces when quite full) and with very little trouble. The phospho- rus should be put in first in small pieces, that it may be covered by the water, and the potash last, which produces considerable heat as it is dissolved. A spirit lamp held in the hand, will be found most convenient for heating the re- tort, as the temperature may be easily regulated by holding the lamp at any distance that may be required. A slight ex- plosion generally takes place in the interior of the retort from the phosphureted hydrogen that is first produced reacting upon the common air which it contains, and as considerable condensation takes place at the same time, if the beak of the retort is placed in the pneumatic trough before this is observed, water will be very apt to be thrown into the retort by the pressure of the atmosphere. The best method is to place the beak of the retort into a cup containing a very small quantity of water in the manner shown in Figure 30 (103), not trans- ferring it to the pneumatic trough till the vapours formed in 106 PREPARATION OF PHOSPHURETED HYDROGEN. the retort shall have been expelled, and become transpa- rent and colourless, which takes place almost immediately after the air in the apparatus has been acted upon by it. If the heat is applied very slowly at first, the oxygen of the air is gradually consumed. The retort is supported by a re- tort stand. 242. When a large quantity of this gas is required, it will be found most convenient to prepare it by filling a green glass retort (a metallic one is still better) with milk of lime and chips of phosphorus ; 7^ grains of phosphorus with 1500 of slaked lime and three or four ounces of water by measure will give a sufficient quantity for the experiments which arc usual- ly performed with it ; the beak of the retort should not be wide, and a tin tube may be attached to it, if it is not suffi- ciently long. After some time has elapsed, a gas is disen- gaged, which does not take fire spontaneously ; the process may then be discontinued. 243. The other method of preparing the hydrurct of phos- phorus is by the action of muriatic acid diluted with several parts of water on phosphuret of calcium, and a purer gas is said to be obtained in this manner, than by any of the pre- ceding processes. For this purpose a small tubulated retort is filled nearly full with the acid; fragments of the phosphuret arc then put in, and the gas collected over the pneumatic trough. Phosphuret of calcium, indeed, decomposes water without the addition of an acid, and disengages phosphurcted hydrogen gas, but it is procured more easily by adding the muriatic acid. In both cases, a portion of the water is de- composed, its oxygen combining with the calcium and form- ing lime, and the hydrogen uniting with the phosphorus. 244. In the other processes, a portion of the water is also decomposed, its hydrogen combining with part of the phos- phorus and forming the gas which is disengaged, while the oxygen converts the rest into phosphoric and hypophosphorous acids, which remain in combination with the potash or lime. I >;ivy has stated that this gas is formed also by pouring six parts of sulphuric acid over one of phosphorus cut into small pieces and mixed with two of granulated zincand and ten of water PH0SP1IUKETED HYDROGEN. 107 245. To show the horizontal rings that arc formed when this gas takes fire in a calm atmosphere, which present a very beautiful appearance, the beak of the retort should be placed under water in the pneumatic trough, or in a glass bason. Every bubble of gas, as it breaks on the surface of the water immediately takes fire, and produces a ring. 246. Place a jar half full of air on the shelf of the pneu- matic trough, and allow the gas to rise in it ; a vivid Hash of light will be seen as before, and all the oxygen will be con- sumed. 247. Place another jar half full of oxygen gas in the same situation ; each portion of the gas as it rises in the jar and mixes with the oxygen, produces an extremely vivid flash of light, perhaps as intense, though only momentary, as can be made by artificial means. In performing this experi- ment, care must be taken not to allow the gas to accumulate in the jar without mixing with the oxygen, which frequently takes place from the deposition of a portion of phosphorus on the surface of the water, which rises with the gas, and often enables a large quantity of it to gather into one globule, and whenever this breaks, the jar is thrown down or broken by the violence of the explosion. To prevent gas accumulating in this manner, all that is necessary is to tap the jar with the finger when they begin to appear, or shake it gently over the shelf of the trough on which it is standing. 248. When mixed suddenly with one and a half times its volume of oxygen gas, it is all consumed, and a violent deto- nation takes place, two strong jars containing the proper proportions of the gases must be employed for this purpose, and the one into which the gas is transferred should be more than sufficient to hold both the gases, and wider than the other ; it is scarcely necessary to add that they must be mixed under water, and only a small quantity of the gases em- ployed. 249- A flash of light appears also, according to Dr. Henry, when this gas is admitted into a flask exhausted as com- pletely of air as can be done by the air pump, showing that there is still a small quantity of air present. To show this, a 108 PHOSPHURETED HYDROGEN. jar with a stopcock fixed to it is filled with the gas, or it may be only filled in part, if it should be a large jar, and an ex- haused flask which must also be provided with a proper stop- cock is connected with it precisely in the same manner as the bladder is connected with the jar in Figure 25 (see 65, p. 27-) The stopcock of the jar is opened first that the phosphureted hydrogen may have time to act on the small quantity of air between the two stopcocks, and on opening the other, water is forced from the pneumatic trough into the jar by the pres- sure of the atmosphere, and the gas which it contained at the same time passes through the connector into the exhaust- ed flask. 250. The products of its combustion, both in air and oxy- gen, are phosphoric acid and water. Experiments similar to those which have been described may be made by transmitting the gas into jars filled with chlorine, a brilliant green light being produced, while it combines with the hydrogen, and also with the phosphorus, forming muriatic acid and 1 per- chloride of phosphorus. If a glass retort is taken into a dark room while full of this gas, it presents a very beau- tiful appearance, as the atmospheric air gradually mixes with the phosphureted hydrogen ; the beaks of the retorts used in all these experiments, however, should be small, that neither air nor water may enter too quickly. 251. Phosphureted hydrogen may be detonated with nitric or nitrous oxide ; it is decomposed also by iodine and potas- sium which combine with the phosphorus. Water absorbs about five per cent, according to Dr. Thomson, when it has been previously boiled to expel the air which it usually con- tains ; solutions of the sulphate of copper and chloride of lime absorb it in large quantity, and are employed to as- certain its purity, as they do not absorb any other gases with which it might be mixed. Its smell is very fetid and disagree^ able. BIPHOSPHURETED HYDROGEN. 109 Sect. IV. — Biphosphureted Hydrogen. Equivalent, 14? 252. The same discrepancy of opinion prevails with respect to the exact composition of this compound, that has been al- ready observed with respect to the other compounds of phos- phorus. It has also received a variety of other appellations, indicating that it contains a smaller proportion of phosphorus than the preceding compound, some of which are very inaccu- rate — as protophosphureted hydrogen, which would lead to the opinion that it consists of one equivalent of phosphorus and one of hydrogen, though many of those who adopt this term regard it as a compound of two proportions of hydrogen and one of phosphorus. It exists always in the gaseous state, and is distinguished from the hydruret of phosphorus, by not tak- ing fire spontaneously in atmospheric air, or oxygen gas. 253. This gas is prepared by exposing the crystalline com- pound of water and phosphorous acid (233) to heat in a small retort, and collecting the gas that is disengaged over water. The oxygen of part of the acid and of the water converts the rest of the phosphorous acid into phosphoric acid, and the phosphorus that remains combines with the hydrogen of the water that is disengaged. The same compound is formed when phosphorous acid and water are exposed to heat, and to- wards the end of the processes described for the preparation of phosphureted hydrogen gas ; it is also formed when this gas is allowed to stand over water for some time, part of the phosphorus being deposited. 254. The smell is not so strong and disagreeable as that of the phosphureted hydrogen. When mixed with oxygen it detonates violently on the approach of flame, or when heated to 300. It inflames spontaneously in chlorine, and is ab- sorbed in small quantity by water. In Dr. Ure's Dictionary, and in the 31st volume of the Ann. de Ch. et Phys., a de- 110 CARBON. tailed account of Dumas's recent investigations with respect to the exact composition of these gases will be found. CHAP. VII. CARBON. Equivalent by weight 6 ; by volume □ (one measure); spe- cific gravity of the vapour of Carbon 0.416.; weight of 100 cubic inches 12-708 grains. 255. Though carbon has not been obtained in the gaseous form, so as to admit of a series of experiments being made with it in this state, it may be volatilized by the action of a powerful galvanic battery, and it has been customary to re- present its equivalent by volume, by a measure equal to that of the equivalent of hydrogen gas. The term Carbon is used to signify the pure and inflammable part of charcoal, which, in the manner that it is usually procured, always contains a small proportion of foreign matter. 256. Charcoal is prepared on the large scale by piling wood into cones, which are often of an immense size, covering it in a great measure with earth, and setting fire to it through a few air holes, which are closed when it is properly kindled. It is also obtained in great quantities now, by exposing wood to heat in iron cylinders, for the manufacture of gunpowder, where a finer kind of coal, as it is technically termed, is re- quired, a large quantity of inflammable gases, water, tar, and impure acetic or pyroligncous acid being disengaged; the latter is condensed in barrels connected with the cylinders, and pu- rified by subsequent operations. Wood consists of carbon, oxygen, and hydrogen, and in both these processes the oxygen and hydrogen arc driven off by the heat, the different pro- ducts that are disengaged being formed by their combining CARBON, 111 with one another, and with part of the carbon, while the rest of this element remains mixed with any saline matter that may have previously existed in the wood. 157. To prepare a small quantity of charcoal, a few pieces of wood may be put into a crucible, covered with sand, and exposed to heat in the open fire or in a furnace. When no more gas is disengaged, it may be removed from the fire, but the charcoal must not be taken out till it is cold, to prevent it from taking fire. The wood (a potatoe does equally well) may be cut into the form of a crucible, or in any other shape that the charcoal may be required to have. 258. Very pure charcoal may be obtained by exposing se- veral inflammable substances to heat in vessels where they are not brought into contact with the air, as by passing the vapour of alcohol or turpentine through a red-hot tube, where a considerable quantity is deposited, in the form of a fine powder. The condensed soot that is obtained from the im- perfect combustion of resinous substances, oil, and many other inflammable matters, and known by the name of lamp black, consists principally of charcoal, in a very fine state of division, and when exposed to a red heat for some time, in a covered crucible, to drive off and decompose any volatile mat- ter adhering to it, may be used for the most delicate experi- ments, where the purest carbon is required. 259- Charcoal usually retains the form of the wood from which it is prepared. It is black and brittle, insoluble in water, and has the property of destroying the odour, the taste, and the colour of many substances, for which it is much em- ployed in the arts, and for domestic purposes, as in rendering tainted meat fresh, &c. By filtration through charcoal pow- der, water that has become putrid, from long keeping in wooden vessels, becomes sweet and palatable. By exposing it to a red heat in close vessels, the same quantity of charcoal may be used again and again. On the small scale, it is often used with great advantage in depriving solutions of their colour, when they are required to be chemically examined. For this purpose, what is termed animal charcoal or ivory black, is usually preferred, which is a mixture of charcoal and phos- 112 CARBON. phate of lime, prepared by exposing bones to heat in close vessels, and derived from the decomposition of the gelatine, of which they contain a considerable quantity. 260. The charcoal obtained from the gas-works, or by the smothered combustion of coal, is usually termed coke, and consists of that portion of the carbon which the hydrogen and oxygen have not been able to carry away in the gase- ous form, mixed with saline and earthy matter which the coal contains. 261. Charcoal is infusible by heat, and undergoes little or no change in its appearance or properties, when exposed to heat in close vessels ; but when subjected to the action of a powerful galvanic battery, part of it is volatilized, and the lustre of the remainder is increased, while it also becomes so hard as to be able to scratch glass ; approaching in no small degree, therefore, in its character to the diamond, which is composed of pure carbon, and produces the same compound (carbonic acid) during its combustion. 262. When charcoal has been recently prepared, it has the property of condensing in its pores a large quantity of di f_ ferent gases, without any other changes taking place in their condition or its own. The following table by Saussure, shows the quantity of different gases which boxwood charcoal ab- sorbs, when allowed to remain in contact with these different gases for twenty-four hours : — Ammonia, . . 90 vols. Carbonic Acid, 35 vols Muriatic Acid, 89 Oxygen, . . 9.25 Sulph. Hydrogen, 65 Nitrogen, . u Nitrous Oxide, 40 Hydrogen, . . 1.75 In conducting these experiments, a piece of red-hot box- wood charcoal should be plunged under mercury, and allowed to remain so till it is cold, after which it may be introduced into a measured quantity of any of these gases, placed in the same portion of mercury, taking care not to allow it to come in contact with the air. It imbibes about 1-Gth of its weight of water from the air in a day. CARBON. 1.18 263. Charcoal is highly inflammable, producing great heat during its combustion, and is much employed as fuel, especi- ally where smoke must be carefully avoided, and gives no flame when properly prepared. In oxygen gas it burns more brilliantly than in atmospheric air, producing vivid sparks ; the apparatus already described for the combustion of charcoal in nitrous oxide (Fig. 33, p. 48.) may be used here. In both cases, the product of the combustion is carbonic acid, the oxygen neither increasing nor diminishing in volume, but becoming heavier by the quantity of carbon which combines with it ; every 16 of oxygen take up 6 of carbon. Even the diamond, the hardest substance in nature, may be inflamed in oxygen gas, and consisting solely of carbon, carbonic acid is the only product of its combustion. It was in this manner that its real nature was ascertained, though Newton conjectured that it was an inflammable substance, long before the experiment was made, from its great refractive power. 264. Expose some well pounded charcoal to a red heat in a covered crucible, remove it, and then drop some nitric acid upon it from a pipette with a long stem. The charcoal takes oxygen from the acid, and a shower of sparks are thrown out. Charcoal, in a minute state of division, decomposes this acid at a much lower temperature. 265. From the powerful affinity which charcoal has for oxygen at a high temperature, it is constantly employed for deoxidating the metals and a number of other substances. With this element it forms two important compounds, car- bonic oxide and carbonic acid. It unites with hydrogen in several proportions, and with nitrogen it forms cyanogen, the base of prussic acid. It enters into the composition of all the peculiar products of the vegetable and animal kingdom. It is used in the preparation of iron and steel, in the composi- tion of gun-powder, and forms the basis of black paints and printing ink. 114 CARBONIC OXIDE. Sect. I. — Cabbonic Oxide. Equivalent by weight, 14,- by volume □ (one measure.) Specific gravity, 0.972. Weight of 100 cubic inches, 29.652 grains. 266. There are several processes by which this inflamma- ble gas may be procured, most of which consist essentially in depriving carbonic acid of half its oxygen by heating it with some substance which has a great affinity for this element. The best method, perhaps, consists in exposing dried chalk to heat with an equal weight of iron filings, and a small quantity of charcoal, (from a fifth to a tenth part) in an iron tube re- tort, and raising its temperature speedily in a good furnace or open fire, till the gas begins to come. The materials should be reduced to as fine a state of division as possible, and the temperature must never be allowed to fall, otherwise the gas soon ceases to come, or carbonic acid is disengaged instead of carbonic oxide. The retort represented in Fig. 14, (21,) will do very well, and the end of the small tube connected with it may be placed below the shelf of the pneumatic trough. 267- In this process the chalk (which is a carbonate of lime,) parts with its carbonic acid on exposure to heat, and the iron and carbon mixed with it take away one proportion of oxygen, converting it accordingly into carbonic oxide. Either the iron or the carbon would do separately, but when they are both taken, there is less risk of the product being contaminated with carbonic acid. A sufficient quantity of gas for showing the general properties of carbonic oxide may be procured from 250 grains of chalk. 268. Another process for preparing carbonic oxide gas con- sists in transmitting carbonic acid repeatedly over carbon at a high temperature in a porcelain tube. It should be suffici- ently long to allow corks to be put in at both ends without any danger of their being destroyed by the heat when it is made PREPARATION OF CARBONIC OXIDE. 115 to traverse a furnace, and stuffed with fragments of charcoal ; a bladder half full of carbonic acid with a stopcock being fitted to one of the corks by boring a hole through it, and an empty- bladder to the other. When the charcoal has been properly heated, taking care not to urge the heat too strongly at first, lest the tube should be cracked, the carbonic acid is passed slowly over the charcoal from the one bladder to the other, by pressing it gently, and this is repeated several times. The volume of the carbonic acid is doubled, and it is converted en- tirely into carbonic oxide. This process, however, is never resorted to except for experimental illustration, as the carbonic oxide may be procured more easily by the method previously described. 269- The theory of the action is sufficiently obvious ; the carbonic acid is converted into carbonic oxide by losing one proportion of oxygen, as is seen in the following diagram, and this combining with part of the carbon, also becomes carbonic oxide. But carbon occupies the same volume whether com- bined with one or two equivalents of oxygen ; consequently, a given measure of carbonic acid must double its volume when converted into carbonic oxide by carbon. Before decomposition. After decomposition. f Carb. 6 ~^"14 == Q Carbonic oxide. Carb. acid, 22 = □ 4 Oxyg. 8 - (Oxyg.8 Carbon, 6 2^14 = □ Carbonic oxide. 270. Carbonic oxide has been prepared also by the decom- position of oxalic acid, which is regarded as a compound of carbonic acid and carbonic oxide. On exposing it to heat in a small green glass retort, it is resolved into these two gases, but any of the preceding processes are better, as the water of crystallization which it contains generally carries a portion of the acid along with it, which is apt to obstruct the beak of the retort and cause an explosion. Dumas proposes to heat the superoxalate of potash with five times its weight of sulphuric acid, when the latter takes away the potash and water from the oxalic acid, on which it is resolved into carbonic oxide and 116 CARBONIC ACID. carbonic acid. The carbonic acid is separated by collecting the gases over a trough filled with lime water, the lime com- bining with it but not affecting the carbonic oxide. 271. When carbonic oxide is required particularly pure, it ought always to be agitated with lime water or a very dilute solution of caustic potash, as it generally contains a small quantity of carbonic acid by whatever process it has been pre- pared. 272. Carbonic oxide is an inflammable gas, transparent and colourless, and burns with a pale blue and lambent flame. During its combustion it combines with half its volume of oxy- gen, and is converted into carbonic acid ; a condensation tak- ing place equal to the volume of oxygen consumed. It de- tonates feebly with pure oxygen, even when mixed in the ex- act proportions required for converting it into carbonic acid. Its smell is disagreeable, it is very noxious to animal life, and is sparingly absorbed by water. Sect. II. — Carbonic Acid. Equivalent by weight 22, (oxygen 16 + 6 carbon ;) by vo- lume Q ; specific gravity 1.527, weight 0/ 100 cubic inches 46.597 grains. It is gaseous at all temperatures to which it has hitherto been exposed under ordinary pressure, but has been rendered liquid by a pressure of thirty-six at- mospheres. 273. Carbonic acid is most easily procured by pouring mu- riatic acid diluted with an equal bulk of water on fragments of white marble, a compound of carbonic acid and lime. The muriatic acid combines with the latter, and the carbonic acid is disengaged with effervescence. The materials may be put into a retort, or a bottle or flask with a bent tube adapted to it may be employed, as no heat is required, and the gas collected in jars over the pneumatic trough. Two ounces of muriatic CARBONIC ACID. 117 acid by measure may be taken for every 300 grains of marble, and as every 100 grains of marble contains 46 grains of car- bonic acid, which occupy very nearly the space of 100 cubic inches at ordinary temperatures, it is easy to calculate the quantity of marble required to afford a given bulk of gas. 274. Carbonic acid is a transparent and colourless gas, heavier than air, and incapable of supporting combustion or respiration. Animals are killed immediately when confined in it, and fatal accidents are frequently occurring in old wells and pits, at the bottom of which it often accumulates in considerable quantity, A burning candle, therefore, should always be let down before any person descends, which will be extinguished if the air is loaded with this gas, and incapable of supporting respiration. 275. From its great specific gravity, it may be poured from one jar into another in the same manner as water, and a jar left full of it with the cover off and the mouth turned upwards will retain it for a considerable time. A candle may be ex- tinguished also by pouring the gas upon it, and the experi- ment may be varied in a variety of ways. 276. Pure carbonic acid does not pass into the lungs when it is attempted to inspire it, a spasm of the glottis which im- mediately takes place preventing its entrance ; but if it is di- luted with a considerable quantity of air, it then passes freely into the lungs, and though its action is scarcely perceptible at first, it soon gains upon the system, and has often proved fa- tal in a close apartment where a charcoal chauffer has been used. 277- Water absorbs its own volume of carbonic acid gas or rather more, and by pressure it may be made to take up a much larger quantity. A solution is easily made by filling a bottle about two- thirds full of the gas over the pneumatic trough, and shaking the remaining water with it as long as it continues to absorb any. It may be kept for years if it is put into bottles which are filled quite full and properly secured. 278. Carbonic acid water is sometimes prepared on the small scale by passing the gas through water in the bottles of Woulfe^ apparatus. Another apparatus, invented by Dr, 118 CARBONIC ACID. Fig. 46. Nooth, (Fig. 46.) is also occasionally used for this purpose. It consists of three glass vessels, which are made to fit accurately to each other by grinding. In the lower vessel the carbonic acid is prepared from a mixture of equal weights of sulphuric acid and chalk, the acid being previ- ously diluted with twelve times its weight of water, and the apparatus inclined to one side, by a small piece of wood placed below it, that all the chalk (which should be finely powdered) may not mix with it at once. The middle ves- 'sel is filled with the water to be impregnated with the gas, a valve at the bottom allowing the carbonic acid to arise into it from the lower vessel, when it is accumulated in sufficient quantity to overcome the pressure of the liquid above, but constructed so as to prevent any of the solution from falling into the lower vessel. When the gas accumulates in the middle vessel, it presses upon the surface of the liquid, a part of which is forced into the vessel above, and when the whole water has been completely saturated, the excess of carbonic acid, after passing into the upper vessel (which always takes place whenever the level of the liquid falls below the extremity of the tube part of the upper vessel, as is represented in the figure,) lifts up the conical stopper at the top, which returns to its place the moment it has escaped. Before using it, see that the valve moves readily on blowing through it. 279- Carbonic acid water has a pleasant acidulous taste, sparkles when poured from one vessel to another, but loses its agreeable pungency when exposed to heat, or to the air for some time, from the acid gas escaping. This also takes place when it is frozen, or placed in the exhausted receiver of an air-pump. 280. Pour a little of the infusion of litmus into some car- bonic acid water ; it will be immediately reddened, but the original colour will be restored by exposing it to heat. 281. Mix another portion with some lime water in a glass; it will immediately become milky, carbonate of lime being CARBONIC ACID. 119 formed, which is insoluble. Add an additional quantity of the acid water, and the liquid will become clear, as a supercar- bonate of lime is then formed, which is soluble. If it is now exposed to heat, the excess of carbonic acid will be disengag- ed, and it will again become turbid. 282. Pour some lime water on a flat plate, and expose it to the air ; a pellicle will speedily form on its surface, from the carbonic acid in the air combining with the lime. 283. Breathe through some lime water in a bottle by a bent tube. The carbonic acid produced during respiration will combine with the lime, and render the liquid turbid. " r 284. Fill a tube, about 12 or 18 inches long, with carbonic acid gas over the pneumatic trough ; close it with the finger or thumb, and place it in a small cup of mercury, or on the shelf of a mercurial trough. Introduce a small quantity of a strong solution of caustic potash from a pipette of the form Fig 47. represented in Fig. 47, by blowing upon it, taking care H not to allow any air to enter. If the carbonic acid is quite pure, the potash will absorb it all, carbonate of II potash being formed, and the mercury will rise in the ( J tube ; if any common air was mixed with it, the bulk of the remaining gas will indicate the quantity, and deducting this from the total amount of gas, the quo- tient gives the quantity of real carbonic acid which it contains. 285. Carbonic acid combines with the different salifiable bases, forming a very well defined class of salts. It has, how- ever, but a feeble attraction for them, compared with almost all other acids, and may be easily displaced, assuming at the same time the gaseous form, when it is not retained in solu- tion by a large quantity of water. The carbonates according- ly effervesce with most other acids, and by noting the quan- tity of carbonic acid disengaged in this manner, the quantity of carbonates, in any saline mass, may be estimated. This may be done either by measuring the volume of carbonic acid, which a given weight of mixed salts affords, or by ascertaining its weight. 286. In the first case, the easiest method of proceeding is 120 CARBONIC ACID. to fill a long tube (closed at one end, and capable of con- taining two or three cubic inches,) nearly full of mercury, filling it completely afterwards with muriatic acid diluted with an equal quantity of water. The thumb is placed over this, after dipping it in oil, or rubbing it over with a little gas lute, the tube inverted, and placed in a cup of mercury. One or two grains of the solid salt are then introduced into the tube, (the experiment is most easily performed with a frag- ment of some carbonate,) and the moment it rises to the top, and comes in contact with the acid, the carbonic acid is dis- engaged with effervescence, depressing the mercury, and its amount is estimated by examining the volume which it occupies and making the usual corrections ; one equivalent of car- bonic acid indicating one equivalent of a carbonate, whatever may be the nature of the base. 287- In the other method, which is more generally adopted, Fig. 48. a thin glass flask or bottle, of the form shown in Fig. 48, is placed on one of the scales of a ba- lance, with some muriatic acid, and accurately coun- terpoised along with a given weight of the substance under examination and the bent tube passing through a cork, which fits to the mouth of the flask. This tube is put in when the acid and carbonates are mixed together, to prevent any loss from particles of liquid that are thrown up during the effervescence, and it is evident, that, by adding weights to the scale on which the glass vessel is placed, (when the effervescence has finished,) till it is again counter- poised, they will indicate the quantity of carbonic acid that has been evolved, making allowance for what may still re- main within the apparatus. 288. Carbonic acid exists abundantly in nature, especially in combination with lime, forming T 4 4 5 of limestone, and other kinds of carbonate of lime. In the Grotto del Cano, and other parts of the globe, it flows out in a continued stream in the gaseous form ; it constitutes the characteristic ingredient of the carbonated mineral waters, and is formed in large quan- tities by the respiration of animals, during combustion and fermentation, and by those changes which dead vegetable and HYDRURET OF CAUBOK. 121 animal matter are continually undergoing at the surface of the earth. It is generally supposed that carbonic acid is prevent- ed from accumulating and the purity of the atmosphere main- tained by the vegetable world, the leaves of plants decom- posing carbonic acid in the sunshine and exhaling oxygen ; in the shade, however, they absorb oxygen, and produce car- bonic acid. Sect III. — Hydruret of Carbon or Olefiant Gas. Equivalent by zveight 7> (carbon 6 + 1 hydrogen) by vo- lume, □ (half a measure) ; specific gravity 0.972 weight of 100 cubic inches 29.652. 289. This gas is most easily prepared by mixing one part by measure of alcohol with three of strong sulphuric acid in a glass retort, and exposing the mixture to a gentle heat. The retort should not be filled more than a third full, and when only a small quantity of the gas is required, half an ounce of alcohol with a proper quantity of sulphuric acid will be found quite sufficient. The alcohol and the acid must be shaken together before the heat is applied. A little ether is formed at first, and towards the end of the process, sulphurous acid, carbonic oxide, and the bihydruret of carbon (another com- pound of carbon and hydrogen) are disengaged ; the mixture also becomes quite black from the deposition of carbon, and is very apt to boil over. 290. To understand the nature of the changes that take place in this process, it must be recollected that every 23 parts, or one equivalent of alcohol, is composed of three parts of hydrogen (three equivalents) twelve of carbon (two equivalents) and eight of oxygen (one equivalent), so that it may be regarded as a compound of one equivalent of water and two of olefiant gas, for the different elements are present exactly in the pro- portions necessary to form these compounds. The water then may be said to combine with the sulphuric acid, while the olefiant gas is disengaged ; the new arrangement which the 122 HYDRURET OF CARBON elements of the alcohol assume is represented in the following diagram. Before decomposition. Alcohol 23 LOxyg.8 After decomposition* 7 Olefiant Gas. 7 Olefiant Gas. 9 water. The two proportions of olefiant gas which are disengaged from each equivalent of alcohol at the commencement of the process, often combine with an equivalent of alcohol which is not de- composed, forming one equivalent of ether, which explains its appearance ; the black colour which the liquid assumes afterwards, and the formation of bihydruret of carbon arise from the elements of the alcohol arranging themselves in a diiferent manner, which will be readily understood from the annexed diagram : Before decomposition. fHyd. 1 —;;_;: Alcohol 23 Hyd. I Hyd. 1 Carb. 6 Carb. 6 lOxyg.8- After decomposition. 8 Bihydruret of Carbon. 6 Carbon precipitated. 9 Water. But no sooner is the carbon precipitated than it begins to react upon the sulphuric acid, taking one equivalent of oxygen from it, and being converted into carbonic oxide, while the sulphuric acid becomes sulphurous acid in consequence of losing this proportion of oxygen, a small quantity of carbonic acid is also formed towards the end of the process. The proportion of these gases that is disengaged in the succeeding stages of the process becomes greater and greater as it proceeds ; at first the olefiant gas is very pure, and the sulphurous and carbo- nic acids formed afterwards may be removed by caustic potash. 291 . A large quantity of this gas, mixed with other inflam- mable compounds of carbon and hydrogen, may be procured by exposing oil and resinous or fatty substances ito a red heat in close vessels. It is in this manner ^shat what is termed oil HYDHU11KT OF CARBON. 123 gas is prepared on the large scale, which owes its great illu- minating power principally to the olefiant gas which it con- tains. The process may be imitated on the small scale in the apparatus described in 45, (page 19) using oil instead of wa- ter, and putting in iron shavings or fragments of earthen ware, merely to extend the surface. The tube must be brought to a good red heat before the oil is allowed to drop into it. All these inflammable substances are composed almost entirely of carbon and hydrogen, and by exposure to a high temperature their elements are made to arrange themselves so as to form a large quantity of gaseous matter, while a consi- derable portion of carbon is deposited. 292. An inflammable gas may be obtained from alcohol in the same way, but it does not burn with such a rich flame, and contains carbonic oxide and bihydruret of carbon along with olefiant gas. Instead of having the apparatus constructed in the manner represented in 45, it is sometimes more conve- nient to have it made of cast iron in the form shown in the Fig. 49. annexed figure. Its construction and the manner of using it will be readily under- stood from the figure, and what has been [fjp :r -";;(r ^ explained in 45. It may be heated by placing it in a large chauffer with a piece cut out at the side, or in a furnace. 293. An inflammable gas from coal, containing a considerable quantity of olefiant gas, may be easily obtained in small quan- tity by heating some pieces of coal in an iron bottle placed in the fire, a quantity of tar, water, and carbonate of ammonia is at the same time distilled over. The proeess is an offensive one, and in town it will be better to procure a quantity for ex- periment by attaching an empty bladder, or the stopcock b of the gasometer represented in Fig. 5, page 4, to the extre- mity of a tube supplying gas to a burner from the coal gas works, by corks with holes pierced in them and flexible tubes ; the plug at c is taken out that the water may escape as the gas enters, and great care taken not to allow any air to mix with it. The stopcocks which admit the gas should be opened wide, but the water prevented from flowing out rapidly. The 124 HYDllURET OF CARBON. gas that is disengaged from coal by heat does not consist solely of compounds of carbon and hydrogen, but contains also carbonic oxide, carbonic acid, nitrogen and sulphureted hydro- gen ; the proportion of these is not very great, though suffici- ent to render the gas less luminous during its combustion, and impart other sensible properties to it. The ammonia is produced by the combination of part of the nitrogen and hydro- gen of the coal when the other products are formed, and part of the carbonic acid unites with it, and converts it into the car- bonate of ammonia. 294. Olefiant gas burns with a rich white flame when lighted with a match in contact with the air, and consumes a large quantity of oxygen, requiring three times its bulk of this gas for its complete combustion. With pure oxygen it deto- nates violently when the gases are mixed in the above pro- portion, a strong detonating bottle must be used in perform- ing this experiment, and it should be wrapped round with a towel, in case of accident. The products of its combustion are water and carbonic acid. In the following diagram the theory of the action is represented, the proportion of oxygen required both by weight and by measure, with the quantities of the resulting products : Before decomposition. After decomposition. M 1 n , i Carb. □ 6 ''-7 22 □ carbonic acid. 7 p olefiant gas = j Hyd p 1 ^ Fig- ^6), continuing the distillation as long as any inflam- PREPARATION OF ALCOHOL. 133 mable liquid comes over. When ale or porter is employed, a ca- pacious retort must be used, as the large quantity of carbonic acid which they contain is disengaged by the heat, and would cause part of the fluid to run over into the receiver, if the dis- tillation were conducted in a small retort. 316. By repeating the distillation, the alcohol may be se- parated from an additional quantity of water which is left in the retort, but it is impossible in this manner to separate the whole of the water, however often the distillation may be re- peated. 317- To prepare absolute alcohol, as it is termed, when completely deprived of water, heat subcarbonate of potash to the temperature of 300, and add it to spirit of wine in a glass bottle. Shake the mixture well, and then allow it to remain at rest for some time. If a sufficient quantity of the alkaline carbonate has been added, the liquid will divide into two parts ; that which floats above is the alcohol deprived of the most of the water previously combined with it, while that below consists of the water which has dissolved the sub- carbonate, and formed a dense oily-looking fluid. The alco- hol is decanted, or drawn off with a syphon, and more of the hot subcarbonate is added till it is no longer moistened. On decanting it again, and distilling it with a gentle heat, the al- cohol is obtained free from water. Nearly half a pound of subcarbonate is required for every pint of rectified spirit of wine. 318. Other substances are occasionally employed to sepa- rate the water from the alcohol instead of the subcarbonate of potash, as the chloride of calcium, lime, barytes, and alu- mina. Very strong alcohol may also be procured by suspend- ing a bladder full of spirit of wine in the air, the water pass- ing through the coats of the bladder and evaporating from its surface, while the alcohol is retained. Mr. Graham's process for preparing absolute alcohol may be easily conducted by those who have an air pump. A shal- low glass or earthen bason is filled with quick lime in coarse powder, and another, nearly full of spirit of wine, put over it; they are then placed on the plate of the air pump, and the 134 J'REI'ARATION OK ALCOHOL. air exhausted till the liquid appears as if it were beginning to boil. Both the water and alcohol evaporate at first, the watery vapour being absorbed by the lime, which does not affect the vapour of the alcohol ; but water does not remain in combina- tion with alcohol, unless covered by an atmosphere of its own vapour, and as this is condensed by the lime as speedily as it is formed, the water continues to evaporate till it is complete- ly removed, which usually requires three or four days, while the alcohol is prevented from evaporating by the pressure of its own vapour. 319- The quantity of alcohol in spirituous liquids may be ascertained by adding hot subcarbonate of potash to them in the manner already mentioned, after precipitating the colour- ing and mucilaginous matters by dropping into them a strong solution of the acetate of lead, or agitating them with the protoxide of lead in fine powder. By operating in this man- ner, Mr. Brande proved satisfactorily that alcohol really ex- ists in fermented liquors, and is not formed by any reaction taking place between their elements when heat is applied. A table of the results of Mr. Branded experiments, and the quantity of real alcohol in a variety of wines and other fer- mented liquors is published in his Manual of Chemistry. 320. Alcohol and water combine in every proportion, con- densation and an evolution of heat usually accompanying the combination, which may be easily seen by filling a tube ten or twelve inches long and already half full of water with alcohol, and shaking them together. Thenard found that when alco- hol of the specific gravity of 0.9707 ^ s mixed with an equal quantity of pure water, instead of any condensation taking place they occupy a larger volume after they have combined than before. With an equal bulk of water, it forms what is usually termed Proof Spirit, the specific gravity of which is 0.917- The Proof Spirit used for pharmaceutical purposes has usually a specific gravity of 0.930, and contains 43 per cent, of real alcohol. The following table by Lowitz shows the quantity of real alcohol in diluted alcohol at different densities, and will be found useful in making experiments with this li- quid. Though 1 have adopted the number 0-796 to represent ALCOHOL ANJJ WATER. 135 the specific gravity of absolute alcohol, perhaps Lowitz is the only one who has obtained it so light. According to the London College its specific gravity is 815. It is seldom pre- pared for commercial purposes with a less specific gravity than 835 or 830. Lowitz's Table, showing the quantity of absolute alcohol in 100 parts of spirit at different densities. Specific gravity at 60. Alco- hol in 100 pts Specific gravity at 60. Alco- hol in lOOpts Specific gravity at 60. Alco- hol in 100 pts Specific gravity at 60. Alco- lol in 100 pts Specific gravity at 60. Alco- hol in lOOpts 0.796 100 0.848 80 0.896 60 0.939 40 0.974 20 0.798 99 0.851 79 0.898 59 0.941 39 0.975 19 0.801 98 0.853 78 0.900 58 0.943 38 0.977 18 0.804 97 0.855 77 0.902 57 0.945 37 0.978 17 0.807 96 0.857 76 0.904 56 0.947 36 0.979 16 0.809 95 0.860 75 0.906 55 0.949 35 0.981 15 0.812 94 0.863 74 0.908 54 0.951 34 0.982 14 0.815 93 0.865 73 0.910 53 0.953 33 0.984 13 0.817 92 0.867 72 0.912 52 0.955 32 0.986 12 0.820 91 0.870 71 0.915 51 0.957 31 0.987 11 0.822 90 0.872 70 0.917 50 0.958 30 0.988 10 0.825 89 0.874 69 0.920 49 0.960 29 0.989 9 0.827 88 0.878 68 0.922 48 0.962 28 0.990 8 0.830 87 0.879 67 0.924 47 0.963 27 0.991 7 0.832 86 0.881 66 0.926 46 0.965 26 0.992 6 0.835 85 0.883 65 0.928 45 0.967 25 0.994 5 0.838 84 0.886 64 0.930 44 0.968 24 0.995 4 0.840 83 0.889 63 0.933 43 0.970 23 0.997 3 0.843 82 0.891 62 0.935 42 0.972 22 0.998 2 0.846 81 0.893 61 0.937 41 0.973 21 0.999 1 321. Absolute alcohol is a transparent and colourless li- quid, having a fragrant odour, and a hot pungent taste. It is not only lighter, but also much more volatile than water ; when its specific gravity is 810, it boils at 173.5. It is much more expansible than water by heat, and has been frozen by the cold produced by the evaporation of liquid sulphurous acid in vacuo. Mr. Walker exposed it to a temperature of — 91 without freezing it. Alcohol burns with a pale blue lambent flame, which be- comes yellow on diluting it with water, and every 23 parts consume 48 of oxygen. The products of the combustion are water and carbonic acid. A number of salts when mixed or 138 ETHERS. dissolved in it impart a particular colour to the flame, particu- larly the muriate of strontia and the muriate of copper, the former communicating a deep red colour, and the latter ren- dering it of a fine green. With a great number of substances it combines in definite proportions, according to Mr. Graham, forming a peculiar class of compounds, which he has termed alcoates. It is decomposed by potassium and sodium, which attract oxygen from it, and disengage hydrogen gas. 322. Alcohol is an agent that is constantly employed in the laboratory for affording a steady and powerful heat during its combustion, and in a great number of operations, where it is used as a solvent, or to afford particular compounds by the reaction of its elements on other substances. It is particular- ly useful in dissolving resins, camphor, volatile oils, vegetable acids, and alkalis, and many salts and other substances which are insoluble in water, enabling us to separate them from other bodies with which they may be mixed or combined. From the large quantity of hydrogen and carbon which it con- tains, it has been occasionally employed to deoxidate particu- lar substances, and from the rapidity with which it evaporates, it is sometimes used to produce cold. Sect. VII. — Ethers. 323. A variety of products may be obtained by the action of the different acids on alcohol, which have received the gene- ric term of Ethers, but which differ considerably in their pro- perties according to the nature of the acid by whose action they have been formed. The most important of these are Sul- phuric and Nitric Ether. SULPHURIC ETHER. 137 1. Sulphuric Ether. Equivalent by weight, 37, (Ox. 8 + Carb. 24 -f. hydrogen 5; or water 9 + olefiantgas 28J Equivalent by volume, □• Its specific gravity is .632 according to Lowitz, when pure, but it is seldom obtained of a less specific gravity, than .720. It boils at 98 in the open air, and in vacuo at 40. Specific gravity of vapour 2.569. Weight of 100 cubic inches, 78.36 grains. 324. To prepare sulphuric ether, equal weights of sul- phuric acid and alcohol are exposed to heat in a plain glass re- tort, pouring in the alcohol first and then the acid by a bent glass funnel, (Fig. 35, p. 53,) and adjusting the retort in a sand bath already heated to the temperalragfFpl f«$&J|in the manner shown in Fig. 36, (same page) Tfee *aerd ancithe al- cohol should be well mixed previously Jb^ shaking then^ to- gether in the retort, when the temperature rj|s$ "jgo^iieffjfcly, and the receiver should be rather larger,? in .arf*«®^^^he size of the retort represented, and tubul^StoH^tjii^elp^ay the atmospheric air, and any other gasewi^fjroducts t^J^may be formed towards the close of the operaiwfe^'^W^diexed F 'g- 5 ^ figure, (51.) sh(&5£^1rSgMC the ._ (T^ ^1) neck of which should fit closely to ^^_ — ^J3 i^Hf^l t ^ ie nec k °f ^ e retort ? anc * tne joint >! / J j| ! rendered tight by tying it round MZZJ Ik^U with a piece of linen or cotton cloth spread over with a paste made of flour or linseed meal. When a large quantity of materials is operated on, the bent tube should be made to pass into a second receiver, or to dip into a bottle in the manner represented, which is kept cold by placing it in a jar or basin full of water or ice ; the tube must not fit tightly to the neck of the bottle but allow any gas to be freely disengaged. The first receiver should be tied round with a piece of linen or cotton cloth, that it may be more 138 SULPHURIC ETHER. easily kept cold ; ice or snow should always be used when they can be procured. 325. The distillation is generally continued till a quantity of liquid has come over equal to one half of the alcohol em- ployed. More ether is said to be obtained when it is kept constantly boiling than at a lower temperature, though this has been disputed ; the retort should not be filled more than half full, and great attention must be paid to the heat applied during the whole of the operation, as the mixture is apt to boil over when urged with too strong a fire. By adding half the quantity of alcohol employed at first, an additional quantity of ether may be obtained, and this may be repeated again ; the acid soon becomes so diluted, however, that it is unable to pro- duce any more. 326. The ether that condenses in the receiver is never ob- tained pure at first, being always mixed with a little alcohol that distils over unaltered, and some sulphurous acid produced by the decomposition of part of the sulphuric acid. To remove these, it is mixed with fused potash, taking five or six grains for every ounce of alcohol employed, and distilled again from a retort with a very gentle heat till five or six sevenths of it shall have passed over. The potash retains the sulphurous acid along with some water and alcohol, and to separate the alcohol completely, the product of the second distillation may be shaken with about three-fourths of its bulk of water, which combines with all the alcohol and a little ether, the most of the ether separating from it in a short time and floating above. It is then decanted, and kept in bottles with ground glass stopples. 327. On the small scale, an ounce or two of alcohol with as much sulphuric acid by weight will be sufficient to show the process, condensing the product in a Florence flask. 328. The theory of the action has already been adverted to, being precisely similar to what takes place in the first stage for the preparation of olefiant gas, (See the diagrams repre- senting the composition of alcohol, &c. page 122.) In the present instance, however, a much smaller quantity of sul- phuric acid being used, instead of a minute portion of ether Water. defiant Gas. 9 + 14 = 23 Alcohol. 9 + 28 = 37 Ether. □ + B = □ Alcohol. □ + BB = □ Ether. SULPHURIC ETHER OIL OF WINE. 139 being formed, — almost all the water withdrawn from the alcohol and olefiant gas disengaged, for every equivalent of alcohol which loses one of water, two atoms of olefiant gas are set at li- berty and combine with an equivalent of alcohol which is not de- composed, forming an equivalent of ether. Hence, there will be a large quantity obtained ; and it is obvious also, that there must be twice as much olefiant gas combined with a given quantity of water in ether as there is in alcohol. Equivalents by weight Equivalents by weight Equivalents by volume Equivalents by volume And by examining the corresponding equivalents by weight and by volume, we see that the vapour of ether must be heavier than that of alcohol, containing twice as much olefiant gas as exists in alcohol condensed within the same space. 329- If the distillation is continued after a quantity of ether equal to one half of the alcohol employed has distilled over, a peculiar substance begins to rise in the retort, and condense in the form of an oily liquid, which has been called the Oil of Wine. It is composed of one equivalent of sulphuric acid and four of olefiant gas, and has no acid properties, the sulphuric acid which it contains being completely neutralized by the olefiant gas, a property which we certainly could not suppose it would possess. When exposed to heat, half of the olefiant gas is disengaged, and the compound which remains is what has been termed Sulpho-vinic Acid, consisting accordingly of one equivalent of sulphuric acid and two of olefiant gas. 330. Water can dissolve only a small quantity of ether, but alcohol and ether combine in every proportion. It is very in- flammable, and burns with a much more copious and richer flame than alcohol ; the products of its combustion are water and carbonic 'acid. A few drops put into a detonating bottle, full iof [oxygen gas, which is immediately corked, speedily diffuse themselves through the gas, and form an inflammable 140 SULPHURIC ETHER. mixture that detonates violently on bringing a lighted match to the mouth of the bottle. This is an experiment that should be performed with a very small and strong bottle, as detonat- ing bottles that have not been injured by any other explosive mixtures are frequently broken by this. When transmitted through a red hot tube, it is decomposed, and gives the same products as alcohol. 331. From the rapidity with which ether evaporates at na- tural temperatures, it is often used to produce an intense de- gree of cold. If a small quantity is poured into a jar, which is immediately covered with a tray, it will speedily eva- porate, and on applying a lighted candle to the mouth of the jar, it will be found to be full of an inflammable vapour. If a larger quantity of ether is put into an open jar, and a coil of thin platina wire heated to redness in a spirit lamp is sus- pended over it at a particular distance, which is easily found on trying the experiment, instead of becoming cold, it re- mains red hot till the whole of the ether is consumed. The platina being a bad conductor of caloric, it does not part with its excess of heat so rapidly as any other metal would do, and coming in contact with the vapour of ether and air in the jar, the high temperature which it is at causes a slow combus- tion to take place, by which a sufficient degree of heat is pro- duced to maintain it in a state of incandescence. 332. Sulphuric ether is not capable of dissolving so many substances as alcohol, still, however, it is often found useful in separating or extracting principles that are insoluble in al- cohol or water, more especially in vegetable chemistry. It combines with ammonia, camphor, resins, volatile oils, sul- phur, phosphorus and chloride of gold, but has little or no action on the fixed alkalis, earths, common metallic oxides, and the greater number of the salts. 2. Nitric Ether. 333. The best method of preparing nitric ether is by mixing equal weights of alcohol and the strong filming acid, PREPARATION OF NITRIC ETHER. 141 prepared by distillation from two parts by weight of sulphuric acid with three of nitre. The large quantity of nitrous acid which it contains re-acts on the alcohol, and converts it into ether in a day or two, which floats on the top of the remaining liquid, and may be easily removed by a small syphon. Pure nitrous acid, prepared by distillation from the nitrate of lead, would do still better, but it is not so easily obtained. Two or three ounces of alcohol will be sufficient to show the pro- cess ; the alcohol is put into a bottle first, and small quanti- ties of the acid poured into it at a time by a funnel with a long stem, which passes to the bottom of the bottle, mixing them thoroughly after each addition of acid, and then placing the bottle in cold water to prevent any violent reaction taking place. A drachm or two of the acid may be added every quarter of an hour in this manner, till it is all mixed with the alcohol. The bottle should be provided with a conical stopple to allow the gas that accumulates in it to be disengaged ; it is forced up in the same manner as the stopple in Nooth's appa- ratus, already described, and returns to its place when the ex- cess of gas has passed by it. Other methods for the preparation of nitric ether have been proposed. The Dublin College directs the alcohol to be mixed with sulphuric acid in a flask, and the mixture to be poured over bruised nitre in a retort, mixing a pound of the acid with nineteen ounces of alcohol by measure, and using three parts by weight of nitre for every two of sulphuric acid employed. The retort must be placed in a bason of cold water to prevent the action becoming too violent, and it should not be filled more than a third full of nitre. I have seldom found it necessary in repeating this process at ordinary temperatures, to apply any heat to commence the action, as is usually recommended. The sulphuric acid combines with the potash, and the nitric and nitrous acids acting on the alcohol in its nascent state produce the ether, which must be condensed in a large tubulated receiver kept very cold ; when a large quantity is required, a second tubulated receiver should be connected with it, and the gaseous products allowed 142 NITRIC ETHER. to escape by another bent tube. The first method of pre- paring nitric ether will be found preferable, however, as the reaction often becomes very turbulent when this process is adopted, though every precaution is taken to prevent it. 334. In all experiments with nitric acid and alcohol, great care must be taken not to mix a large quantity of acid with the alcohol at once, as the gaseous products that are imme- diately produced are apt to throw out the whole of the mix- ture with explosive violence. Though a small quantity of acid may be added to a large quantity of alcohol without any particular action being observed, a small quantity of alcohol cannot be mixed with a large quantity of acid without being completely decomposed, as the particles of the alcohol are sur- rounded by the acid on every side, which affords oxygen more readily to the inflammable elements that enter into its com- position. To see the truth of this, all that is necessary is to pour a little alcohol and acid into different glasses, and pour a few drops of the acid into the alcohol, and then of the alcohol into the acid, when the appearances described will be ob- served. 335. Nitric ether always contains a little acid as it is pro- cured at first, which may be removed by potash or lime. It has a very pale lemon yellow colour ; a pleasant smell similar t© that of apples, and a strong penetrating taste. It is hea- vier and more volatile than sulphuric ether, burns with a rich flame, and soon becomes acid by keeping. When it is puri- fied by distillation, the operation should always be carried on with a very gentle heat, as it is decomposed when distilled quickly at a higher temperature. Its atomic composition is still disputed, but it is admitted to contain a portion of nitrogen in addition to the other ele- ments which exist in sulphuric ether. Spirit of Nitric Ether. 336. The Spirit of Nitric Ether is a compound of nitric ether and alcohol, which is prepared by mixing nitric or SPIRIT OF NITRIC ETHER. 143 nitrous acids with a larger quantity of alcohol than is used in the process for ether, and distilling the mixture in a glass re- tort. The Edinburgh College directs one pound of their ni- trous acid (136) to be mixed with three of alcohol, and dis- tilled with a heat not exceeding 180, till a quantity of liquid has been obtained equal to the alcohol employed. Dr. Dun- can says the distillation may be commenced whenever the materials have been mixed ; the precautions already pointed out must be attended to, and the receiver kept cold in the usual manner. 337. A variety of other ethers have been prepared by the action of different acids on alcohol, but none of them are of any importance. Sect. VIII. — Pyroxilic and Pyroacetic Spirit. 338. Both these compounds consist of carbon, oxygen, and hydrogen ; they are lighter than water, volatile and inflamma- ble. The Pyroxilic Spirit is formed during the prepara- tion of acetic acid by exposing wood to heat in close vessels. It burns with a blue flame, leaving no residuum, and its spe- cific gravity is .828. Pyroacetic spirit, or ether, as it has been termed, is formed when the metallic acetates are exposed to heat in the preparation of strong acetic acid. It is lighter than the Pyroxilic spirit, and is easily distinguished from it by burning with a dense flame, and combining in all propor- tions with oil of turpentine. Neither of these substances can be prepared easily on the small scale, but pyroxilic spirit is frequently employed as a substitute for alcohol in the spirit lamp, when it can be procured, and affords a very steady heat during its combustion without producing any smoke. 144 PREPARATION OF CYANOGEN. Sect. IX. — Cyanogen or Bicarburet of Nitrogen. Equivalent by weight 26, (carbon 12 + 14 nitrogen,) by volume □. Specific gravity 1.804. Weight of 100 cubic inches, 55.06 grains. It requires a pressure of nearly four atmospheres to render it liquid at 45. 339. The bicarburet of nitrogen, discovered by Gay Laussac, received the name of cyanogen from its being one of the essential ingredients in the ferrocyanate of iron, which is of a rich blue colour. It is obtained in the gaseous form by ex- posing the bicyanide of mercury (a compound of metallic mercury and cyanogen) to heat in a small glass retort, and collecting the gas that is disengaged over the mercurial trough. Green glass retorts should be taken when they can be obtained, or an iron tube retort ; an ounce of the bicyanide gives a considerable quantity of gas, and when only a very small quantity is required, it may be procured by heat- ing a little of the bicyanide in a bent tube with a spirit lamp. 340. In conducting this process, the bicyanide employed should not fill the retort more than half full and be perfectly dry. The heat applied should be sufficient to expel the cyanogen slowly and steadily, as it is liable to be decomposed by a higher temperature. The mercury is volatilized as the gas is disengaged, the bicyanide melting and becoming black before it is decomposed. Towards the end of the process, a small quantity of nitrogen gas is disengaged, arising from the decomposition of a part of the cyanogen, the carbon previous- ly in combination with it remaining in the form of a light porous mass, very like lamp black. 341. The bicyanide of mercury is prepared by boiling pure Prussian blue with one and a half times its weight of the per- oxide of mercury in an earthen evaporating bason, reducing both to a fine powder previously, and mixing them with fif- teen or twenty parts of water. The Prussian blue is obtained sufficiently pure for this purpose by digesting the Prussian blue of commerce in muriatic acid diluted with ten times its PREPARATION OF CYANOGEN. 145 bulk of water, which removes the alumina and other foreign matters it usually contains, washing it repeatedly with water till the excess of acid has been removed. The precise nature of Prussian blue has not yet been satisfactorily demonstrated, but it contains hydrocyanic acid (a compound of cyanogen and hydrogen) and peroxide of iron, whatever other ingredi- ents may be present ; and in this process, the acid combines with the peroxide of mercury forming hydrocyanate of mer- cury, two equivalents of it uniting with one of the oxide, and the peroxide of iron is set at liberty. The hydrocyanate re- maining in solution is separated by filtration, and on evapor- ating the liquid till a pellicle appears on its surface, crystals of the bicyanide of mercury are obtained when it cools ; the two equivalents of hydrogen in the two of hydrocyanic acid (that combine with every equivalent of the peroxide of mercury) uniting with the oxygen which it contains, while the cyanogen goes to the metallic mercury, in the manner shown in the following diagram : f Hyd. 1 7 9 Water. Hydrocyanic acid | Hyd. 1 —/~y. Equivalent by weight, 34. (Cyanogen 2(5 -f- il Oxygen.) When cyanogen is transmitted through the solution of an alkali or alkaline earth in water, a part of this fluid i: decomposed, one portion of the cyanogen combining with the hydrogen and forming hydrocyanic acid, while the other com bines with the oxygen and is converted into cyanic acid, both of these uniting with the alkali or earth in solution. These HYDROCYANIC ACID. 147 salts arc not easily separated from each other, and it is diffi- cult to obtain the cyanic acid from any base with which it may be combined, as it is very apt to be converted into car- bonic acid and ammonia by the reaction of its elements. A cyanate of potash may be prepared by exposing the peroxide of manganese to a red heat with an equal weight of the ferro- cyanate of potash, the oxygen in the peroxide combining with the cyanogen which it contains, and the cyanic acid formed in this manner remaining in combination with the potash. 346. Cyanic acid has not been applied to any use. The most important of its compounds are the cyanates of silver and mer- cury, both of which detonate violently by heat or percussion, and when mixed with some of the acids. Before the nature of the acid which exists in these compounds was known, it was termed fulminic acid. 2. Hydrocyanic or Prussic Acid. Equivalent by weight 27 (Cyanogen 26 + 1 Hydrogen : ) by volume \ [ | (two measures); Specific Gravity of the liquid acid 0-7508 at 45 ,• it boils at the temperature of 80 and freezes at zero. Specific gravity of the vapour of hydrocyanic acid 0.9374. Weight of 100 cubic inches 28.50 grains. 347- This is a more important compound than the preceding, and as it is a very powerful poison, acting perhaps more in- stantaneously than any other, all experiments with it must be performed with the greatest caution. Several fatal acci- dents have already occurred from people operating with it who were not fully aware of its nature, and even the fumes of the acid are apt to induce a state of stupor when they are incau- tiously inhaled, though diluted with a large quantity of air. 348. The best process for preparing the strong acid was pointed out by Vauquelin, who procured it by transmitting a stream of sulphureted hydrogen slowly over the bicyanide of mercury in a tube (which may be about 18 inches long and 148 PREPARATION OF HYDROCYANIC ACID. Fig. 52. half an inch in diameter,) filled with fragments of this sub- stance, and placed horizontally, in the manner represented in the Figure (52.) The sulphureted hydrogen is passed over it till the whole of the cyanide has become black, none of this gas escaping through the other extremity of the tube till it is all decomposed, and whenever the odour of sulphureted hydrogen is perceived at the mouth of the receiver, the tube a, connected with the apparatus in which the sulphureted hy- drogen is produced, is withdrawn, and the extremity of the other tube closed with a little plaster of Paris. It is heated gently when the plaster of Paris has set, and the hydrocyanic acid which has been formed is volatilized and condensed in a small receiver placed in a freezing mixture. 368. One equivalent of the bicyanide requires two equiva- lents of sulphureted hydrogen for its complete decomposition, and two equivalents of hydrocyanic acid and one of the bisul- phuret of mercury are obtained ; the following diagram gives a view of the action that takes place : — Before Decomposition. Sulphureted Hydrog-. 2 equiv. = 17x2 - [Sulph Bicyanide of \ Jf mercury 252. } ^yan ( Merc After Decomposition. 27 Hydrocyanic Acid. Hydrocyanic Acid 232 Bisulphuret of Mercury. 349. The hydrocyanic obtained in this manner is very strong and pure, and equal in weight, when carefully collected, to about a fifth part of the bicyanide employed. 350. There is another method of preparing this acid in a concentrated state by pouring two parts of muriatic acid, by weight, on three of the bicyanide of mercury in a small glass retort, the beak of which is connected with a receiver or tube in the manner represented in Fig. 52, the tube being filled PREPARATION OF HYDROCYANIC ACID. 149 ■with fragments of marble and chloride of calcium. A reaction takes place between the bicyanide of mercury and the muriatic acid, (which is composed of chlorine and hydrogen,) exactly si- milar to what has been illustrated in the preceding diagram with sulphureted hydrogen ; the chlorine, in two equivalents of the acid, combining with the mercury in one equivalent of the bicyanide, and forming bichloride of mercury, while the cor- responding equivalents of hydrogen and cyanogen unite and produce two of hydrocyanic acid. The hydrocyanic acid pro- cured is always mixed at first with a little water and muriatic acid, condensing in the tube which should be kept cold ; on removing the retort and closing the extremity of the tube, it passes over into the receiver when a gentle heat is applied, the chloride of calcium retaining the water, and the marble the muriatic acid. The hydrocyanic acid formed by this process is not so easily collected as by Vau quean's. 351. Concentrated hydrocyanic acid is speedily decomposed by the reaction of its own elements, and a diluted acid is- ge- nerally employed for most chemical and medical purposes. In this state it may be procured much more easily than by any of the preceding processes. The ferrocyanate of potash is dissolved in a small quantity of water, and half its weight of sulphuric acid, previously diluted with twice its bulk of water and allowed to cool, is poured over it in a small glass retort connected with a receiver ; on applying a gentle heat, hydro- cyanic acid and watery vapour are disengaged, and condensed in the receiver. The sulphuric acid sets the hydrocyanic acid (which forms part of the ferrocyanic acid in the ferrocya- nate,) at liberty, by uniting with the potash, with which it was previously in combination. The distillation should be conducted slowly, and stopped when a quantity of liquid, equal to about a third of the water employed, has been condensed ; the receiver must be kept cold. The acid prepared in this manner often acquires a bluish tint on keeping, from a small quantity of iron carried over from the ferrocyanate during distil- lation being converted into Prussian blue ; it is easily remov- ed by repeating the distillation. 352. Another method, recommended by Dr. Ure, is to pass 150 PREPARATION OF HYDROCYANIC ACID. a stream of sulphureted hydrogen through a solution of the bicyanide of mercury till no more sulphuret of mercury is pre- cipitated, and to agitate the hydrocyanic acid which remains in solution with carbonate of lead as long as it is rendered black, to remove the excess of sulphureted hydrogen. The same reaction takes place that has been already described, and the solution which is obtained is transparent and colourless when properly prepared. 353. The diluted acid prepared at the Apothecaries' Hall in London is obtained, according to Brande, by distillation from one part of the bicyanide mixed with an equal weight of muriatic acid (spec, gravity 1.15,) and six parts of water, con- tinuing the distillation till the liquid condensed is equal to the water employed. 354. Pure and concentrated hydrocyanic acid is a limpid fluid' like water, but has a strong and penetrating odour, producing severe headach, with nausea, and even fainting, when the va- pour which it emits is incautiously inspired. I have seen a very stout young man so much affected by smelling some di- luted acid, which had been prepared three months before from the ferrocyanate of potash, by the process described, that the bottle containing it fell out of his hand, and for half an hour afterwards he was almost totally unconscious of what was go- ing on around him. It is seldom that the diluted acid affects any one so powerfully, but this shows the great care which should be taken in making any experiments with this sub- stance. A single drop of the strong acid, introduced into the throat of a large dog, kills it after a few hurried inspirations. Its odour is similar to that of the peach blossom, bitter al- mond, &c. which indeed derive their agreeable flavour from the presence of a small quantity of this acid. I have seen the diluted acid frequently used a year after it had been prepared, and its strength did not appear to be impaired, but the strong acid is sometimes decomposed in a few hours after it has been made, and can seldom be kept more than a fortnight at ordi- nary temperatures. Its taste is cool at first, but it soon becomes hot and irri- tating. It evaporates rapidly when exposed to the air ; if a HYDROCYANIC ACID. 151 drop is suspended at the extremity of a small rod, part of it is congealed by the cold produced by the evaporation of the rest. With water and alcohol it combines in all proportions ; it reddens the infusion of litmus faintly, and combines with the salifiable bases (but does not neutralize them) for which it has but a feeble affinity, and may be displaced even by the carbo- nic acid. 355. As the strong acid boils at the temperature of 80, it may be easily procured in the gaseous form, when disengaged in any of the first processes mentioned for its preparation, by receiving it in pneumatic jars over the mercurial trough, hav- ing previously brought the mercury to that temperature, by putting a red hot poker into it for a short time. Its vapour forms an inflammable mixture with atmospheric air, and de- tonates when mixed with a proper quantity of oxygen gas ; the products of its combustion are water, carbonic acid and nitrogen gases. On referring to its equivalent by volume, it is evident that 2 measures, (one equivalent,) will require 2| measures of oxygen (five equivalents,) for its complete com- bustion, four of these combining with the carbon of the cya- nogen, and forming two equivalents of carbonic acid, while the other converts the hydrogen into water ; the nitrogen gas is left mixed with the carbonic acid. 356. The specific gravity of the diluted acid varies accord- ing to the quantity of water which is combined with it, and Dr. Ure has well remarked that the density of the liquid is a criterion of greater nicety than most practitioners will be in- clined to appeal to in estimating its strength, diluted acid of the specific gravity 0.998, containing twice as much real acid as when it is 0.996. The test which he proposed for ascer- taining the proportion of real acid in the diluted acid is the peroxide of mercury, which is dissolved readily by it when reduced to a fine powder, shaking them together in a phial, and continuing to add small quantities of the peroxide till it is no longer dissolved. Every two equivalents of the acid, (27 X 2 = 54) dissolve one of the peroxide (216), which is ex- actly four times heavier than the acid required, (54 x 4 = 21 6), On dividing, therefore, the weight of the peroxide dissolved 152 HYDROCYANIC ACID. by four, the quotient expresses the quantity of real acid con- tained in the diluted acid employed. No heat must be ap- plied, as it might expel part of the acid at first in the gaseous form, or cause a larger quantity of the peroxide to be after- wards dissolved. If an excess of mercury has been taken up, the solution turns paper stained with an infusion of red cab- bage to a green. 357. If any muriatic acid is mixed with the hydrocyanic acid, it may be detected by adding ammonia till the liquid is neutralized, and evaporating it to dryness by a heat not ex- ceeding 212. Both acids combine with the ammonia, and the hydrocyanate is dissipated, but the muriate remains, re- quiring a temperature of 300 for its volatilization. Nitrate of silver cannot be employed in this instance, though the most delicate test of muriatic acid, as the hydrocyanic acid gives a precipitate with a solution of this salt, which it is not easy to distinguish from that produced by muriatic acid. 358. When hydrocyanic acid has been given in an over-dose, or administered as a poison, the best and indeed the only an- tidote, according to Dr. Herbst, is the cold affusion. He made a number of experiments on animals, and states that when the dose of the poison was not sufficient to prove fatal, two affusions of cold water in general removed every unplea- sant symptom ; when a larger dose was given, it was found necessary to repeat it more frequently, and to persevere for a considerable time. The certainty of success depends much on the early employment of the remedy. He tried liquid am- monia repeatedly, which has been much extolled as an anti- dote to this poison, but says that it will scarcely ever save life, where a dose sufficient to prove fatal has been given, and the symptoms have continued for some time, though he ad- mits, that where the quantity administered is not able to de- stroy life, it is of great benefit in mitigating the severity of the symptoms. Another evident objection to the use of ammo- nia, as Dr. Herbst remarks, is, that it excoriates the parts to which it is applied, and when sufficiently diluted to be free from this inconvenience, it is of very little use. The cold HYDROCYANIC. ACID — TESTS. 1 58 water was poured freely over the head and back, and after- wards over the whole body. 359- The tests proposed for detecting Prussic acid are the nitrate of silver, the sulphate of copper, and the prosulphate of iron. 360. Drop a solution of the nitrate of silver into diluted hydrocyanic acid ; a white curdy precipitate (cyanuret of silver,) falls, which cannot be easily distinguished from the precipitate that muriatic acid, or common salt, gives with the same solution. This test, therefore, is not much relied on. 361. Add a few drops of a solution of the sulphate of cop- per to the hydrocyanic acid, and then a slight excess of caus- tic potash, also in solution. The potash separates the oxide of copper, forming a blue precipitate which reacts on the hy- drocyanic acid, the oxygen of the oxide combining with the hydrogen of the acid, while the cyanogen unites with the cop- per. The cyanuret of copper is recognised by its white co- lour after muriatic acid has been added to the blue precipitate, taking care to add no more than is necessary to remove the excess of copper thrown down by the potash. 362. The prosulphate of iron is employed precisely in the same manner as the sulphate of copper. It is not necessary that the prosulphate should contain no persulphate of iron (which it generally does,) but the persulphate of iron alone should not be used, as Dr. Turner has observed, the hydro- cyanic acid having little or no action upon the oxide of iron precipitated from it by potash, while, with the prosulphate, a protoxide is precipitated, a small portion of which at least must be present, in order that the characteristic colour of Prussian blue may be speedily developed by the pure acid. 363. Dr. Ure states, that this acid may be detected by the sulphate of iron when mixed with 10,000 parts of water, and that the sulphate of copper produces a slight milkiness in water, containing only a 20,000dth part. According to M. M. Leuret and Lassaigne, two or three days after death, it is impossible to detect this poison, as it is soon decompos- ed or volatilized. Where it is suspected that death has 154 HYDROCYANIC ACID. been occasioned by it, they recommend the intestines u* be cut into small pieces, and put into a retort with their contents and some water, adding a small quantity of sul- phuric acid and applying a gentle heat, which should not exceed 212. The volatile products are condensed in a re- ceiver kept cold with ice, and tested in the manner we have described. The odour alone is often sufficient to indicate its presence. 3. Ferrocyanic Acid. 364. When dry animal matters mixed with half their weight of the sub-carbonate of potash are exposed to a dull red heat in an iron pot, and stirred constantly till the pasty mass which is produced at first ceases to give out fetid vapours, a peculiar compound is formed, which may be separated from the rest of the materials by water, and the solution gives large yellow co- loured crystals. They are composed of what is usually term- ed the ferroprussiate or ferrocyanate of potash and water, and it is this salt that is used to prepare the different substances from which cyanogen and its other compounds are usually ob- tained. 365. The process for preparing it is very offensive, but on the small scale, a sufficient quantity may be formed from an ounce or two of materials to show the nature of the salt obtained in solution, when the dry mass is digested in water and filter- ed. The minutiae of the reaction that takes place in the first stage of the process are still far from having been completely explained. The animal matter, which is composed of carbon, oxygen, hydrogen, and nitrogen, is completely decomposed, part of the nitrogen and carbon combining and forming cya- nogen, a portion of which unites with the hydrogen and pro- duces hydrocyanic acid, while the rest combines with some me- tallic iron, and these two compounds, uniting with one ano- ther, form what is termed ferrocyanic or ferroprussic acid ; the carbonic acid of the carbonate is at the same time expelled, and this new acid remaining in combination with the potash, forms the salt which is obtained by solution in water and crys- FERROCYANIC AClb. 155 tallization. According to the most recent experiments, it con- sists of one equivalent of ferrocyanic acid (108), two of pot- ash (96), and one of water (9), it is therefore represented by the number 197- The ferrocyanic acid, again, may be regarded as a compound of two equivalents of hydrocyanic acid and one of the cyanide of iron. The following diagram shows the quantity of cyanogen, iron, and hydrogen in one equivalent (108) of the ferrocyanic acid, and the manner in which they must be united according to this view. Composition of Ferrocyanic Acid. Hydrogen Hydrogen Iron 1 1 28 s./ -—y 27 of Hydrocyanic Acid, -/'-'-y 27 of Hydrocyanic Acid. Cyanogen Cyanogen Cyanogen 26.X< 28/ 26 \ 54 of Cyanide of Iron. 108 108 366. There are two processes for preparing this acid. One consists in adding a solution of 58 parts of crystallized tarta- ric acid dissolved in alcohol to 50 of the ferrocyanate of pot- ash dissolved in as small a quantity of water as possible. The tartaric acid combines with the potash of the ferrocyanate forming bitartrate of potash, which is precipitated in small crystals, not being very soluble in water, and the ferrocyanic acid remains in the liquid which may be separated by filtra- tion. 367- In the other process, a solution of the hydrosulphuret of barytes is added, in the first place, to a solution of the fer- rocyanate of potash, as long as any precipitation takes place, hydrosulphuret of potash remaining in solution, while ferro- cyanate of barytes is precipitated. It is washed on a filter with a small quantity of cold water, then dissolved in a 100 parts of this fluid, and on adding sulphuric acid to precipitate the barytes, taking care to avoid any excess, the ferrocyanic acid is obtained in solution. 368. This acid may be obtained in small cubic crystals of 156 FEEROCYANIC ACID. a yellow colour by allowing its solution to evaporate sponta- neously. It has a much greater affinity for the different sali- fiable bases than hydrocyanic acid, neutralizing them complete- ly, and reddens the vegetable blues ; it is not volatile or poi- sonous, at least in small doses, and is slowly decomposed when exposed to the light, the iron which it contains acquiring oxygen, and being ultimately converted into Prussian blue. M. Porrett gave the view of its composition which I have given, though many are inclined to doubt if this compound ought to be considered as a distinct acid, and have regarded it as a compound of the protoxide of iron with an excess of acid. His opinion has been generally adopted, and ap- pears the most probable, the iron accompanying the other elements that are associated with it to the positive pole, where acids are attracted, on decomposing salts by galvanism, and not going along with the other salifiable bases to the ne- gative pole, where metallic oxides are always found when they have been separated by its agency from acids with which they have been combined, and where the iron ought to have been disengaged, if it had been in combination with the hy- drocyanic acid, in the same manner as potash or any other base is united with an acid in a compound salt. It was called at first ferrureted chyazic acid, from the initial letters of carbon, hydrogen, and azote (nitrogen), but ferrocyanic acid is the term that is now adopted. 4. SuLPHOCYANIC AciD. Equivalent, 59 ; Hydrocyanic acid 27+32 sulphur. 369- This acid is obtained in combination with water by adding sulphuric acid to a solution of the sulphocyanate of potash, and distilling the liquid in a glass retort. The solu- tion of the sulphocyanate is prepared by a process introduced by Grotthus, which Dr. Turner recommends to be conducted in the following manner. A mixture of equal weights of the ferrocyanate of potash and sulphur in fine powder is exposed fehrocyanic acid. I57 to a strong heat over a charcoal chauffer, taking care however not to allow it to become red hot. It soon melts and takes fire, and must be withdrawn from the chauffer a few minutes after the combustion ceases. The residuum consists of sul- phur, sulphocyanuret of potassium, and sulphuret of iron ; a pure solution of the sulphocyanate of potassa is obtained on digesting it in water, the potassium combining with the oxy- gen of a portion of water, which is decomposed, while the hydrogen goes to the sulphocyanogen, and the sulphur and sulphuret of iron mixed with it remain undissolved ; the lat- ter is formed by the sulphur combining with the metallic iron of the ferrocyanic acid of the ferrocyanate. When the sul- phuric acid is added to this solution, it combines with the pot- ash, and sulphate of potash remains in the retort after the sul- phocyanic acid has been separated. 370. When its solution in water is concentrated, it boils at 216, and crystallizes at 54 in six-sided prisms. It reddens the vegetable blues, neutralizes the alkalis, and forms a solu- ble salt of a deep red colour with the peroxide of iron. When boiled with iron filings, sulphuret of iron is formed, and hy- drocyanic acid disengaged. 5. Cyanides of Chlorine, Iodine and Bromine. 371. When chlorine is transmitted through diluted hydro- cyanic acid till it has acquired the property of bleaching, one portion of it combines with the cyanogen, and another with the hydrogen of the acid, forming cyanuret of chlorine and muriatic acid. The excess of chlorine may be removed by agitating the liquid with the mercury, and on exposing it to heat, the cyanuret of chlorine is disengaged in the gaseous form, and must be collected over the mercurial trough, as it is soluble in water. It is always mixed with carbonic acid, when prepared in this manner, formed by the combination of the oxygen of a portion of the water with the carbon of part of the cyanogen which is decomposed. Another process for procuring this substance by M. Serullas is described in the 158 VEGETABLE ACIDS. Ann. de Ch. et Phys. vol. xxxv, and in the preceding and subsequent volumes of the same work, there are several in- teresting memoirs on this subject. 372. Cyanide of chlorine was formerly termed chlorocyanic acid, but it was found to possess no acid properties on more minute examination. It has a very pungent and irritating smell, is absorbed rapidly by solutions of the alkalis, alcohol, and water. When cooled by a freezing mixture, it becomes liquid at 10, and freezes at zero. 373. Cyanuret of Iodine is prepared by exposing the bicyanide of mercury mixed intimately with half its weight of iodine to heat in a small glass retort ; vapours of iodine are disengaged at first, and these are soon followed by white fumes of the cyanuret of iodine, which may be condensed in a cold receiver in the solid form, and having the appearance of wool. 374. Cyanuret of Bromine is prepared by a similar process, and bears a great resemblance to the cyanuret of iodine. It appears to be as powerful a poison as the prussic acid. Sect X. — Vegetable Acids. 375. The Vegetable acids include a variety of compounds which are found in the vegetable kingdom, and are composed principally of oxygen, hydrogen, and carbon. Several of these may be formed artificially, as the oxalic and hydrocyanic acids, and are not, therefore, always classed along with the rest, though it was at one time considered impossible to produce any thing by a simple physical action similar to any of the prox- imate principles formed by an organized structure. The greater number of them can be obtained in the solid form ; they are in general soluble in water and alcohol, have the same general properties as the mineral acids, but are more feeble in their action, and are all decomposed by a red heat, the carbon and hydrogen which they contain taking fire if they arc ex- posed freely at the same time to the air. When heated in ACETIC ACID. 150 close vessels, the principal products are carbonic acid, carbo- nic oxide, gases composed of carbon and hydrogen, water, acetic acid, and an empyreumatic oil. By nitric acid they are in general converted into oxalic acid, and when heated with sulphuric acid they take away a portion of its oxygen, and sul- phurous acid is evolved. The following table shows the composition of some of the most important vegetable acids, and it will be observed that the most of them contain a larger quantity of oxygen than is necessary to convert their hydrogen into water, a circumstance first pointed out by Gay Lussac and Thenard ; the oxalic acid contains no hydrogen, and the succinic and acetic acids are composed of the same weights of their respective elements. (See 305.) Acetic acid Number of Equivalents. Oxyg. Hyd. Carbon. 3+2+4 By Oxyg. == 24 + weight. Hyd. Carbon 2+24 Equivalents of Acids = 50 Succinic acid 3 + 2 + 4 : = 24 + 2 + 24 = 50 Citric acid 4 + 2+4 = 32 + 2 + 24 = 58 Tartaric acid 5 + 2+4 = 40 + 2 + 24 = 66 Gallic acid 3 + 3+4 == 24 + 3 + 24 = 51 Benzoic acid 3 + 6 + 15 '= 24 + 6 + 90 = 120 Malic acid 4 + 10 + 3 = 32 + 10 + 18 = 60 Oxalic acid 3 + 0+2 1. Acetic = 24 + Acid. + 12 = 36 Equivalent by weight, 50. The strongest acid that can he obtained when not in combination with a salifiable base is composed of one equivalent of dry acid and one of water. 376. Acetic acid exists in small quantity in the sap of many plants, and is usually prepared by exposing any liquids that have undergone the vinous fermentation freely to the air, at a temperature between 70 and 90. Many vegetable infu- sions which have never undergone the vinous fermentation are capable of passing at once to the acetic, and the action is promoted by a little ferment taken from a liquid in the same 160 PREPARATION OF ACETIC ACID. state of fermentation. A large quantity of oxygen is absorb- ed, and the vinegar which is produced consists of acetic acid, water, mucilaginous matters that have not been decomposed, and a little alcohol. Large quantities of acetic acid are now obtained also by the destructive distillation of wood, the im- pure acid obtained at first being purified by a second distilla- tion and combination with lime, from which it is afterwards separated by sulphuric acid. 377- To prepare strong acetic acid, pour sulphuric acid carefully and in small quantities at a time on twice its weight of the acetate of potash in a glass retort, waiting till the ebul- lition ceases after each successive addition of the acid, and dis- til to dryness with a heat gradually increased, but never very strong, condensing the product in a receiver surrounded with ice or very cold water. Instead of the acetate of potash, ace- tate of soda, lime, or lead may be employed, taking care to use rather less sulphuric acid than is necessary to combine with the salifiable base in the acetate employed ; the quantity re- quired may be easily found by referring to a table of equiva- lents. In the present process, which is the best, every forty parts of real sulphuric acid (one equivalent,) which are con- tained in 49 of the liquid acid, decompose one equivalent of the acetate (98) consisting of 48 parts of potash and 50 of acetic acid, combining with the potash and forming a sulphate which remains in the retort, while the acetic acid and water of the sulphuric acid are distilled over. It always contains a lit- tle sulphurous acid, from which it may be separated by a se- cond distillation, mixing it with a little of the acetate of lead. 378. The Edinburgh College directs it to be prepared by putting six parts of the dry sulphate of iron with five parts of the acetate of lead into a retort after they have been well mix- ed, and distilling from a sand-bath till no more acid is disen- gaged, condensing the product in a receiver. Here, the sul- phuric acid of the sulphate unites with the oxide of lead in the acetate, and disengages the acetic acid, oxide of iron and sul- phate of lead remaining in the retort. 379. Strong acetic acid may be procured also by exposing some of the metallic acetates to heat without any addition. PREPARATION OK ACETIC ACID. lGi To prepare a little in this manner, fill a small green glass re- tort half full of the acetate of copper, and expose it to heat over a good charcoal chauffer, condensing the product in the usual way ; if a green glass retort cannot be obtained, take a flint glass retort and heat it by a sand-bath, or coat it with plaster of paris, and then the chauffer may be used. The acid obtained in this manner is never pure, being always mixed with pyroacetic spirit formed by a part of it being decom- posed. 380. Acetic acid and water unite in all proportions, and the specific gravity of the compound is sometimes the same, though very different quantities of acid and water may be combined together. The following table shows its specific (gravity when combined with one, four, and seven atoms of water. (Dr. Thomson.) Specific gravity at 60. Acid. Water. 1.06296 1.07132 1.06349 1 equivalent 1 1 equivalent 4 7 _ Its density, therefore, cannot be taken as an index of its strength. 381. The weak acetic acid of the different colleges is pre- pared by distilling vinegar, rejecting the first part out of every eight or ten, as it contains very little acid ; the next five or six are the weak acetic acid of the pharmacopoeias, and the dis- tillation is stopped when they have come over, or the product collected in a different receiver, as it then has an empyreuma- tic odour, from the mucilaginous matters which it contains be- ginning to be decomposed. Its specific gravity varies from 1.006 to 1.009 ; 1000 grains of the latter specific gravity are neutralized according to Mr. Phillips by 145 grains of the crystallized subcarbonate of soda. It cannot be rendered stronger by distillation alone, as the acid and the water rise together on the application of heat. By exposing vinegar or a weak acid to cold, most of the water freezes, leaving a stronger acid which may be separated by straining. M 162 TARTARIC ACID. 382. The method of estimating the strength of acetic acid is by ascertaining the quantity of crystallized subcarbonate of soda which it can neutralize, 50 parts (one equivalent) of real acid being required for one equivalent of the subcarbo- nate. 383. Strong acetic acid has a very pungent and agreeable odour, and volatilizes rapidly when exposed to a moderate heat, producing an inflammable vapour, which is easily kind- led. It crystallizes at a low temperature, and remains solid till heated again to 50. Its acid properties are very well marked, neutralizing completely the different salifiable bases, and forming salts that are decomposed by heat, and easily distinguished by the odour of acetic acid which they emit when sulphuric acid is poured upon them ; it reddens the vegetable blues powerfully, oxidates iron, copper, lead, zinc, and some other metals, and raises a blister on the skin when kept in contact with it for some time. It dissolves volatile oils, camphor, and the active principles of some of the most powerful vegetable medicines. The smelling salts that are sold in the shops are sulphate of potash, mixed with this acid. 384. Acetic acid is often sold in a very impure state. Sul- phuric and sulphurous acids may be detected by acetate of lead, which gives a white precipitate when they are present. Copper will render it blue on adding an excess of ammonia, and lead may be detected by sulphureted hydrogen, which will give a black precipitate. 2. Tartaric Acid. Equivalent, 66. Equivalent of crystallized Tartaric Acid, 75, (dry acid 66+9 water-) It is soluble in Jive pai'ts of water at 60. 385, Tartaric acid is prepared by pouring 49 parts by weight of sulphuric acid on 94 of the tartrate of lime, diffused through three or four times its weight of boiling water, stir- TARTARIC ACID. 163 ring the mixture occasionally for a day or two after it has been well rubbed in a mortar, and evaporating the liquid ob- tained by filtration through a linen bag. One equivalent of the tartrate of lime (94) is composed of 66 of acid and 28 of lime, and the 40 of dry sulphuric acid in the quantity em- ployed combines with the lime, and forms 68 of the sulphate of lime, while the tartaric acid is disengaged, and remains in solution. Very little of the sulphate of lime is dissolved, as it requires a large quantity of water for its solution, and the tartaric acid crystallizes when the liquid is evaporated, which should be done in an earthen evaporating bason over a sand bath, with a very moderate heat. The sulphate of lime in the liquid is deposited after the evaporation has been conti- nued for some time, and should be separated by pouring it into another vessel ; when it has assumed a syrupy consis- tence, it may be set aside to crystallize. The crystals must be purified by a second crystallization. 386. The tartrate of lime is prepared by mixing chalk (carbonate of lime) in fine powder intimately with four times its weight of cream of tartar (composed of 180 bitartrate of potash + 18 water), and throwing the mixture into 10 or 12 times its weight of boiling water, adding small quantities at a time, that the effervescence which takes place may not be too violent ; 94 parts of solid tartrate of lime are precipitated, 114 parts of neutral tartrate of potash remain in solution, and 22 of carbonic acid are disengaged. The following diagram gives a view of the re-action that takes place. Before Decomposition. After Decomposition. ,„ n ^. ( Potash 48 "V--" 5 *" 114 Tartrate of potash. 180 Bitartrate 1 m , A nP . „---' of potash I Tartar. A. 66- t Tartar. A. 66 \ SO Carbonate f Carbonic A. 22 — -^~— 22 Carbonic acid. of lime | Lj me 28 -^ 94 Tartrate of lime. 387- An additional quantity of tartrate of lime may be ob- tained by adding a solution of the muriate of lime to the solu- tion of the tartrate of potash as long as any precipitation takes place, if it is not required for other experiments ; th e propor- lG-i CITRIC ACID. tions in which the materials re-act on one another are repre- sented below. Before Decomposition. After Decomposition. 114 Tartrate J Potash 48 -p? 85 Muriate of potash. of potash -( Tartar. A. W^-''' 65 Muriate f Mliriat. A. 37 '"N. of lime | L| me 28 — ^ 9-i Tartrate of lime. 388. Tartaric acid crystallizes in prisms ; its solution in water is very sour, but has an agreeable taste when sufficient- ly diluted ; it is also soluble in alcohol. When exposed to heat it is completely decomposed, and by destructive distilla- tion a peculiar acid is formed, which has been termed from its mode of preparation the Pyrotartaric acid. Tartaric acid is particularly distinguished by forming an insoluble salt with potash (bitartrate of potash) when added in excess to this al- kali, though the neutral tartrate of potash and the tartrate and bitartrate of soda are very soluble. 389. Tartaric acid and many of its salts have the property of dissolving many metallic oxides, and of preventing them from being precipitated from their solutions by substances which are in general capable of producing this effect. This may be easily seen by adding a little tartaric acid to a solu- tion of the sulphate of iron, and then some ammonia in ex- cess, which will not precipitate the oxide of iron after it has been mixed with the tartaric acid. 390. Tartaric acid decomposes carbonates with effervescence, and precipitates potash from its solutions when they are not diluted with water, small crystals of the bitartrate being formed. 3. Citric Acid. Equivalent, 58. Equivalent of crystallized citric acid 'JG (dry acid 58+18 wafer) ; if is soluble in less than its own weight of water at fiO, and boiling water dissolves about twice as much ; it is also soluble in alcohol. 391- Citric acid is prepared by mixing }{(> parts (one equi- OXALIC ACID. 165 valent) of the citrate of lime diffused through water with 49 of sulphuric acid, and conducting the process in the manner directed for the preparation of tartaric acid. The citrate of lime is obtained by adding chalk in fine powder to the juice of the lime or lemon as long as any effervescence takes place, and is separated from the mucilaginous matters which the juice contains along with the acid, by washing it repeatedly with water. In this process, the citric acid disengages the carbonic acid of the chalk as it combines with the lime, and the sulphuric acid mixed with the citrate of lime forms sul- phate of lime, separating the citric acid which remains in so- lution. By filtering and evaporating the solution crystals are obtained, which must be purified by dissolving them in water and crystallizing again after it has been filtered through paper. 392. Citric acid bears a great resemblance to tartaric acid, but may be easily distinguished from it by carbonate of pot- ash, with which its solution gives no precipitate when added in excess. Tartaric acid may be detected in this manner if it has been mixed with citric acid, a practice that is occasion- ally followed, as it is much cheaper than the citric acid. A solution of the same strength as lemon juice is obtained, according to Mr. Phillips, by dissolving nine and a half drachms of citric acid in a pint of water. The specific gravi- ty of the lemon juice varies considerably, and according to Dr. Henry, a wine gallon usually affords from six to eight ounces avoirdupois of the crystallized acid. 4. Oxalic Acid. Equivalent, 36. Equivalent of the crystallized acid 72 (dry acid 36 + 36 ivater). It is soluble in thrice its weight of cold water, and in its own weight of boiling ivater ; it is also soluble in alcohol. 393. Oxalic acid exists in the juice of the oooalis acetosella or wood-sorrel, and of many other plants in combination with 3 166 OXALIC ACID. potash or lime, but it is almost always prepared by digesting sugar or waste syrups in nitric acid. 394. To illustrate the process by which it is obtained, fill a flask or retort about a third full of nitric acid, (an ounce or two will be a sufficient quantity on the small scale), and add a sixth part of its weight of refined sugar coarsely powdered in small quantities at a time. Apply a gentle heat if necessary by a lamp or chauffer to commence the action, which must then be removed till it becomes feeble, evaporating the re- maining liquid afterwards till it acquires the consistence of sy- rup, when it may be set aside to crystallize. Every 100 parts of sugar give about 60 of crystallized oxalic acid ; it must be purified by solution in water and a second crystallization. 395. The precise nature of the re-action which takes place has not been very minutely investigated ; small quantities of malic and acetic acids are produced at the same time, and, as oxalic acid contains no hydrogen, and the quantity formed is much less than the weight of sugar employed, its formation must depend on the oxygen of the acid attracting the hydro- gen and part of the carbon from the saccharine matter. A large quantity of nitrous acid, nitric oxide and carbonic acid is disengaged; the fumes are very offensive, and the flask should be placed where they may be carried off. Many other substances give oxalic acid when treated in the same manner, as wool, hair, silk, tendon, alcohol and gum arabic. 396. Oxalic acid crystallizes in four and six sided prisms, has an extremely sour taste, and reddens sensibly the vegeta- ble blues even when dissolved in 3000 parts of water. It is resolved into carbonic acid and carbonic oxide when exposed to heat, (270). It gives a white precipitate with lime water, the oxalate of lime being very insoluble. Oxalic acid is a powerful poison and has proved fatal oc- casionally even when diluted with a large quantity of water and taken as an acidulous drink ; two or three drachms are sufficient to produce death. Drs. Christison and Coindet, in an able memoir on poisoning by oxalic acid in the Edinburgh Medical and Surgical Journal, have shown that chalk and mag- nesia are certain antidotes to this poison when administered in BENZOIC ACID. H>7 proper time, the oxalates of lime and magnesia which are form- ed being quite inert. 397* Most cases of poisoning by this acid have arisen from its having been mistaken^for Epsom Salts, (sulphate of mag- nesia) to which it bears a considerable resemblance in external appearance when the crystals are small ; they are easily distin- guished from each other, however, by a number of simple tests. Oxalic acid has a very sour taste, reddens the vegetable blues, effervesces with a solution of the carbonates of potash or soda, and is completely dissipated by heat ; sulphate of magnesia againhas a pure bitter taste, does not affect the vegetable colours, gives a white precipitate with solutions of the alkaline carbonates mentioned, but does not produce any effervescence, and parts with its water of crystallization on exposure to heat without undergoing any further change. An emetic should be taken and large draughts of warm water to promote its action, in the first instance, or the stomach pump may be employed. 398. All the oxalates are decomposed by heat ; those that are soluble in water give a copious precipitate with salts of lime, and on digesting it with a sufficient quantity of sulphu- ric acid, sulphate of lime is formed, the oxalic acid remaining in solution. 5. Benzoic Acid, Equivalent 120. Fuses at 230, and at the same time begins to sublime. It requires 24 parts of boiling water for its solution, but is more soluble in alcohol. 399- Benzoic acid is obtained by sublimation from gum benzoin in which it exists mixed with resin and other vegetable matters, and this is said to be the most productive process and also the least troublesome. An ounce or two of the gum re- duced to powder may be put into a glass or earthenware ves- sel, and a tall cone of paper placed over it. Heat is applied by a sand-bath and the temperature gradually raised till the 168 BENZOIC ACID. acid rises in white fumes and condenses on the sides of the paper. 400. Another process for obtaining this acid is preferred by many, as it is not then contaminated with any empyreumatic oil, which is always mixed with it when prepared by sublima- tion. The Edinburgh College directs three parts of the gum to be reduced to a fine powder and intimately mixed with one part of the subcarbonate of soda. The mixture is then boiled for half an hour in twenty-four parts of water, the liquor pour- ed off, and the residuum boiled again with nine parts of water. The benzoic acid combines with the soda of the subcarbonate, forming benzoate of soda, which remains in solution, and the carbonic acid is separated with effervescence ; the other parts of the benzoin are not dissolved. The mixed decoctions are then filtered and evaporated till only two parts remain, and on adding sulphuric acid previously diluted with seven parts of water as long as any precipitation takes place, the benzoic acid is thrown down and sulphate of soda remains in the liquid, from which it is separated by filtration. It is afterwards dried and sublimed to obtain it in the light feathery and crystalline form in which it is known by the name of Flowers of Benzoin. Both processes may be easily conducted with an ounce or two of the gum. 401. Benzoic acid exists in several other productions of the vegetable world, and in the urine of children and graminivor- ous animals. 402. Pure benzoic acid is very white, and has a shining lustre. Its odour is fragrant and peculiar, but M. Giese at- tributes this to the presence of a small portion of oil. It burns with a yellow flame when exposed suddenly to a strong heat. 403. Benzoic acid has the property of separating the per- oxide of iron completely from its neutral solutions when com- bined with soda or ammonia, and is vised frequently for this purpose in analytical chemistry, especially when the iron is associated with manganese, which it docs not precipitate. GALLIC ACID, &C: 169 C. Gallic Acid, Succinic Acid, &c. 404. As the remaining vegetable acids will seldom be made the subject of experiment by the beginner, excepting the gal- lic, succinic, kinic and meconic acids, it will be sufficient to enumerate them in this place, and refer to the different Jour- nals for a more detailed account of their properties, and the method of preparing them. 405. Gallic Acid is obtained usually by exposing an infusion of gall-nuts to the air for six or eight weeks, when it is deposited in small crystals. More may be obtained by evaporating the liquid still remaining to the consistence of sy- rup, mixed with colouring matter, however, and a peculiar acid which Braconnot has termed the Ellagic. Gallic acid is soluble in water and alcohol. It takes fire when exposed to heat, and is distinguished by the dark blue precipitate that it gives with salts of iron, which is the basis of black ink. When combined with tannin, with which it is usually associ- ated, it has the important property of precipitating most of the metallic oxides from their solutions, even when combined with the more powerful acids, and is accordingly much em- ployed as a re-agent. For this purpose an infusion of gall- nuts is generally used, being easily made by pouring a few ounces of boiling water over every ounce of galls, and allow- ing the mixture to stand for some time before nitration. The tincture is often preferred as it keeps better, and may be pre- pared by digesting the powder of the gall-nuts in alcohol. 406. Succinic Acid is prepared by exposing amber reduced to powder and mixed with an equal weight of sand to heat in a green glass or coated flint glass retort, heating the mixture by a good charcoal chauffer, or on the large scale by a sand bath, A considerable quantity of oily matter comes over, and succinic acid is deposited in crystals on the neck of the retort and sides of the receiver. They are purified by dissolving them in a solution of potash and boiling the solution with charcoal ; on adding nitrate of lead, succinate of lead is preci- 1^0 GALLIC ACID, &C. pitated, and nitrate of potash remains in the solution ; the succinate of lead is then decomposed by sulphuric acid, which combines with the lead and disengages the succinic acid. In combination with ammonia, it is used to separate iron from many of its combinations in analytical processes. 407« Boletic Acid is obtained from the juice of the Bo- letus pseudo igniarius. (Ann. of Philos. v. ii.) 408. Igasuric Acid exists in the nux vomica in combina- tion with strychnia. (See Strychnia.) 409. Camphoric Acid is prepared by digesting camphor in nitric acid. 410. Malic Acid is found in unripe apples and in the juice of a great number of fruits. The acid obtained from the berries of the sorbus acuparia was formerly termed Sorbic Acid, but it has now been proved to be malic acid. 411. Mucic or Saccholactic Acid is formed by digest- ing sugar of milk or gum in nitric acid. When exposed to heat in close vessels, a peculiar acid which has been termed the pyromucic is obtained. 412. Mellitic Acid is obtained by boiling the Honey- Stone in 60 or 70 parts of water and concentrating the solu- tion, when it is deposited in small crystals. The large quan- tity of water employed is found sufficient to separate it from the alumina with which it is combined in the honey-stone. 413. Moroxylic Acid was discovered in combination with lime exuding from the bark of the white mulberry tree. Me- nispermic Acid is found in the seeds of the rnenispermum coccolus, and Fungic acid in the merulius cantharellus and several other plants. 414. The Kinic and Meconic Acids will be'fconsidered when we come to Morphia and Quina. Several other vegeta- ble acids have been pointed out, but they are comparatively of very little importance. BISULl'IIURET OF CARBON. 171 Sect. XI. — Bisulphuret of Carbon. Fig. S3. Equivalent, 38. (Sulphur 32 + 6 Carbon). Specific gra- vity 1.272. It boils at 110. 415. To prepare this substance, a porcelain tube (an inch or more in diameter) coated with clay and wrapped round with iron wire is filled with fragments of charcoal, taking care to leave room for the passage of vapour, and made to traverse a furnace in the man- ner represented in the figure (53.) A retort filled about a third full of sulphur is then fitted to one end of the tube, sup- porting it by a re- tort stand, and us- ing a mixture of clay and sand to make the joining air-tight, covering it afterwards with a little plaster of paris. A bent glass tube about half an inch or rather less in diameter is attached in the same manner to the other extremity of the porcelain tube, and connected with a glass globe terminating in a small tube placed in a receiver half full of water, which must be kept cold ; instead of using a globe, the bent tube may be made to dip under water in one of the bottles of Woulfe's ap- paratus provided with a safety tube. When every thing has been properly adjusted, fire is put into the furnace, and the tube with the charcoal brought gra- dually to a strong red heat. The sulphur in the retort is then made to pass over it in vapour, and as it combines with it the bisulphuret which is formed condenses in drops that fall to the bottom of the water in the receiver. The use of the globe is to prevent any water passing back to the porcelain tube, air 172 BISULPHURET OF CARBON. passing through the water after it has been forced into the globe by the pressure of the atmosphere when the chauffer is removed from the retort. The charcoal employed should be well prepared, and not mixed with any undecomposed woody fibre. 416. The bisulphuret of carbon is never obtained perfect- ly pure at first, but may be easily rectified by a second dis- tillation, putting in a little chloride of calcium to retain any water that may be mixed with it. The temperature to which it is exposed must not exceed 110. It is then pro- cured in the form of a limpid and colourless liquid, remark- ably transparent, having a very offensive and fetid smell, and an acrid pungent taste. 417. Bisulphuret of carbon is very volatile, evaporating rapidly at natural temperatures and producing a great degree of cold. It is highly inflammable, and burns with a bluish flame. With oxygen gas, its vapour detonates violently, and with nitric oxide it burns very rapidly but does not detonate, producing a very brilliant and dazzling light ; these experi- ments are made most easily by filling a detonating bottle quite full of oxygen gas, putting in a few drops of the bisul- phuret, and shaking the bottle (after corking it tightly) till it is volatilized ; the mixture is then inflamed in the usual manner. Alcohol and ether combine with this substance, and it dissolves sulphur, phosphorus and iodine ; chlorine, however, decomposes it. It combines with the alkalis, forming com- pounds which have been termed carbo-sulphurets, and when agitated with an alcoholic solution of potash, a new acid is pro- duced called the Hydroxanthic Acid, from Xanthogen, (de- rived from ^avQog yellotv) the name given to its base, as it forms yellow coloured compounds with several metals. BOROX. 17-i CHAR VIII. BORON. Equivalent, 8. 418. Boiion was prepared by Sir H. Davy, who discovered it, by submitting boracic acid, a compound of boron and oxygen, to the action of a galvanic battery. Gay Lussac and Thenard improved the process and procured it in a greater quantity by exposing boracic acid to a red heat in a copper tube with its own weight of potassium, the latter attracting oxygen from it and forming potash, which is easily removed by washing it with water ; the boron remains in the solid form of a dark olive colour. The boracic acid ought pre- viously to be deprived of water as completely as possible by protracted fusion in a platina crucible, but as it soon attracts water from the air, a detonation takes place at the instant of reduction from the potassium reacting at the same time on the water combined with the acid and disengaging hydrogen gas. To avoid this, Berzelius recommends the dry borofluate of potash to be used instead of boracic acid ; it is prepared by adding a solution of the fluate of potash to a solution of borate of potash, and heating the gelatinous precipitate that is thrown down till it assumes the form of a fine white powder. The theory of the action is the same as in the preceding pro- cess, the potassium taking the oxygen from the boracic acid in the compound salt. : 419- Boron is insoluble in water and alcohol, undergoes no change when exposed to the air at ordinary temperatures, but inflames suddenly when heated to 600, and is converted into boracic acid by combining with the oxygen of the air. In oxygen gas it burns more brilliantly, and attracts oxygen from a number of substances that afford this element readily, as the sulphuric and nitric acids, the nitrate and chlorate of potash. 174 BORACIC ACID. BORAC1G ACID. Equivalent, 24 (Oxygen 16 + 8 Boron). Equivalent of crystallized Boracic acid, 42 (Dry acid 24 + 18 water) ; specific gravity, 1.479- It is soluble in water and al- cohol. 420. To prepare boracic acid, dissolve an ounce or two of crystallized borax (a compound of water, boracic acid and soda) in four times its weight of boiling water, and add sul- phuric acid previously diluted with four or five parts of water till the solution becomes sensibly acid (using a test paper to ascertain when this is the case) and then set it aside to crys- tallize. The sulphuric acid combines with the soda forming sulphate of soda which remains in solution, and crystals of boracic acid are deposited, which are purified by placing them on a paper filter, and washing them with cold water to remove any sulphate of soda that may be mixed with them. A mi- nute portion of sulphuric acid is apt to adhere to them still, which can be removed only by repeated solution and crys- tallization, or fusing it in a platina crucible ; in all ordinary experiments its presence is of no consequence. 421. Boracic acid crystallizes in thin scales which have a shining appearance. Its taste is sour and bitter ; it reddens the vegetable blues, but produces the same effect on turmeric paper as the alkalis, turning it brown, as Mr. Faraday pointed out. Crystallized boracic acid loses its water of crys- tallization when exposed to a heat slowly increased, and the dry acid which remains is fused and forms a transparent and colourless glass on cooling. When a solution of boracic acid in water is boiled, or the crystallized boracic acid exposed suddenly to a high temperature, a considerable portion of it is carried along with the vapour of the water, but the dry acid may be exposed to a white heat without being volatilized. From the facility with which it is fused, and the power which CHLORINE. 175 it has of communicating this property to its compounds, it is much employed both in its pure state and in combination with soda as a flux. CHAP. IX. CHLORINE. Equivalent by weight, 36 ,■ by volume, □. Specific gravity, 2.5. Weight of 100 cubic inches 76.25 grains. It is liquefied by a pressure of about four atmospheres, and also by the cold produced by the evaporation of sulphurous acid, forming a transparent yellow coloured fluid. 422. This elementary substance was discovered by Scheele, and received the name of Oxygenized Muriatic or Oxymuriatic acid afterwards, from the opinion which was then prevalent that it was a compound of muriatic acid and oxygen. Till the re- searches of Sir H. Davy drew the attention of the philosophi- cal world to this subject, it was indeed considered as demon- strated that this was the case ; Gay Lussac and Thenard pointed out about the same time that it may be regarded either as a simple substance or as a compound of muriatic acid and oxygen, and though the views of Sir H. Davy, who has cer- tainly the merit of placing the question on a proper footing, have now been generally adopted, it is not a little singular that there is no fact connected with the chemical history of this substance which is not explicable according to either opi- nion, and in some cases the balance of evidence appears even to be in favour of the old view of its constitution. The following table showing the equivalents of the most important compounds which chlorine forms with the non- metallic substances will be found convenient to refer to while studying its different combinations :— 1JG CHLORINE. Compounds of Chlorine. Chlor. Oxyg. Chlor. Oxyg. Protoxide of chlorine 36 + 8 = 44, or □ + □ = Q_,* Peroxide of chlorine 36 + 32 = 68, or □ + E£=j = {JJ Chloric acid . . 36 + 40 = 76 Perchloric acid . . 36 + 56 = 92 Chlor. Hyd. Chlor. Hyd. Muriatic acid . . 36 + 1 = 37, or □ + Q = m Chlor. Nitrog- Chloride of nitrogen 144 + 14 =158 Chlor. Sulph. Chloride of sulphur . 36 + 16 = 52 Chlor. Carb. Chloride of carbon . 36 + 6 = 42 Sub-chloride . . 36 + 12 = 48 Perchloride . . 108 + 12 = 120 Chlor. C. Oxide. Chlor. C. Oxide. Chloro carbonic acid 36 + 14 = 50, or D + □ = □ Chlor. Olef. gas. Chlor. Olef. gas. Hydro carburet of chlorine 36 -f- 14 = 50, or □ + F] = □ Chlor. "Water. Hydrate of chlorine 36 + 90 = 126 The volumes represent the equivalents by measure of some of the compounds that have been examined in the gaseous form, and correspond with the equivalents by weight placed before them. 423. The best method of preparing chlorine is by mixing one part of the peroxide of manganese with four times its weight of muriatic acid in a glass retort, collecting the gas in wide mouthed bottles placed on the shelf of the pneumatic .trough, and conducting the process with all the precautions described in 9 and 17- The manganese should be reduced previously to a fine powder, and the water in the trough and in the bottles heated to the temperature of 90, to prevent it from absorbing a large quantity of the chlorine. The retort .should not be filled more than half full ; the gas begins to be evolved whenever the materials are mixed, and, on applying a gentle heat by a lamp or chauffer, it is disengaged more ra- " One measure and a quarter. PREPARATION OF CHLORINE. 177 pidly. Each bottle should have its stopple introduced under water whenever it is full, first drawing the finger round the edge with a little gas lute, that it may be taken out easi- ly afterwards. Common pneumatic jars may be employed to collect the gas when it is to be used immediately, but it must be recollected that it will be all absorbed if it is left for a long time over water. 424. In this process, one equivalent of chlorine is obtained from every two of muriatic acid and one of peroxide of manga- nese, the materials reacting on one another in these proportions. Muriatic acid is composed of one equivalent of hydrogen and one of chlorine, and the peroxide of manganese may be re- garded as a compound of one equivalent of the protoxide and one of oxygen. During the reaction which takes place, the protoxide of manganese combines with one proportion of mu- riatic acid forming muriate of manganese, the excess of oxygen at the same time combining with the hydrogen of the other equivalent of muriatic acid and disengaging the chlorine ; the annexed diagram gives a more precise view of the combinations and decompositions which take place. Before Decomposition. After Decomposition. 37 Muriatic Acid J ™« r * * ™f ne - 1 ( Hyd 1 — —-r 9 Water. 37 Muriatic Acid 37 44Perox.Mang. £ p^ox.Mang.36 ^73Mur.ofMang. 118 118 118 The common liquid muriatic acid containing more than its own weight of water, even in its most concentrated state, it is necessary to make allowance for this, and hence the large quantity which is directed to be mixed with the manganese in the preceding paragraph. An ounce of the manganese with the proper quantity of acid will give a sufficient quantity of chlorine for the greater number of the experiments usually performed with this substance, receiving it in wide-mouthed bottles capable of containing from 6 to 10 or 12 ounces of water. N 178 PREPARATION OF CHLORINE. 425. Another process for preparing chlorine consists in mixing 44 parts of the peroxide of manganese intimately with 50 of chloride of sodium (dried common salt, a compound of chlorine and sodium) in a mortar, and pouring 98 parts of sulphuric acid on the mixture previously diluted with half its weight of water and allowed to cool. Three or four hundred grains of salt will be a sufficient quantity on the small scale, using a proportional quantity of the other materi- als, and placing them in a retort or flask with a bent tube adapted to it ; the apparatus used for the preparation of hy- drogen gas (Fig. 16 page 17) does very well when a larger quantity is employed, supporting it on a retort stand that heat may be easily applied ; the sulphuric acid is diluted to pre- vent the copious disengagement of muriatic acid fumes which always takes place when strong sulphuric acid is poured upon chloride of sodium. All the other circumstances pointed out in 423 must be carefully attended to. 426. It will be observed, that the materials are directed to be taken in the proportion of two equivalents of sulphuric acid to one of the peroxide of manganese and one of the chloride of sodium. One equivalent of the acid reacting on the peroxide of manganese forms sulphate of the protoxide and disengages one equivalent of oxygen (see 19 ;) this com- bines with the sodium of the chloride forming soda, which immediately unites with the other equivalent of sulphuric acid producing sulphate of soda, while the chlorine is disengaged. In the following diagram representing the decomposition, the quantity of real sulphuric aeid is stated without the water that is usually combined with it, as it is not decomposed in the present instance. Before Decomposition. After Decomposition. 60 Chloride of j Chlorine 36" ~ 3(3 Chlorine. Sodium. ( Sodium 24 44 Perox. Mang.-! - * - tv/f oa & ( Frotox. Mang.«3o 40 Sulphuric Acid 40 — s ^ 72 Suiph. of Soda. 40 Sulphuric Acid 40 — ^76 Suiph. of Mang. 427. Chlorine gas has a greenish yellow colour, a pungent CHLORINE. 179 suffocating odour, even when diluted with a large quantity of air, and a disagreeable astringent metallic taste. In operating with it, care must be taken not to allow any to mix with the air, as it has often produced a degree of irritation in the lungs and an anxiety and difficulty of breathing with a total inabili- ty of taking a full inspiration which has lasted for days, even when a single inspiration has been made, though still mixed with several times its bulk of air. In larger quantity, it pro- duces a sense of strangulation with a discharge from the nos- trils, and in manufactories where large quantities are prepared, some of the workmen have occasionally fallen down quite sense- less in an instant, when they have been exposed accidentally to a current of the gas. In these cases they are removed imme- diately to the open air, and generally recover very quickly on dashing cold water upon them. It appears too, that some of those who have been affected in this manner never experienced any of the bad effects that accompany the inspi- ration of the gas when diluted with air, probably from the great irritation it occasions in a pure state causing a complete spasm of the glottis, and preventing any of it from passing into the lungs ; the individual, therefore, suffers from the tem- porary suspension of respiration alone. Where the gas has got into the lungs, it has been recommended to take a drink com- posed of the water of ammonia diluted with a very large quan- tity of water, to respire a little ammoniacal gas by keeping the mouth over some ammonia diluted with a less quantity of water, and to inhale the vapour of ether ; if nothing else can be procured at the moment, considerable relief may be obtained by holding the head over a large jar half full of hot water, and breathing into it. 428. Water absorbs one and a half times its volume of chlorine gas at the temperature of 68, according to Thenard. The solution is called in common language Liquid or Aque- ous Chlorine ; it has the colour, taste, and smell of chlorine, it is stimulant and antiseptic and gives chlorine gas when ex- posed to heat. This solution is most easily prepared in the manner directed for obtaining carbonic acid water in 277> or the gas may be transmitted through water placed in the third 180 CHLORINE. bottle of Woulfe's apparatus (Fig. 40, page 7^,) a small quantity of water being placed in the first and second to re- tain any muriatic acid that may be disengaged along with it. The Aqua Oxymuriatica of the Dublin College is merely chlo- rine water. 429- Expose a portion of this liquid to the temperature of 32 by placing it in ice cold water, or surrounding it with a freezing mixture ; it soon begins to congeal, and affords a solid mass of a yellow colour, composed of chlorine and water ; crystals of a definite compound of these substances are ob- tained easily free from any excess of water by dropping a small quantity of this liquid into a bottle filled with chlorine gas, and placing it in a freezing mixture, or in the dark at a tem- perature below 32 for a few days. They form dendritical crystals on the side of the bottle. 430. Aqueous chlorine has no acid properties, but when exposed to the light, part of the water is slowly decomposed, one portion of the chlorine combining with the hydrogen and forming muriatic acid, while the other combines with the oxy- gen, and is converted in chloric acid. From the great attrac- tion that subsists between chlorine and hydrogen, this liquid communicates oxygen to a number of metals and other sub- stances which have an affinity for this element, the chlorine uniting with the hydrogen of a portion of water which is de- composed, and liberating oxygen. 431. Chlorine is particularly distinguished by its power of destroying all vegetable and animal colouring matters, and de- composing effluvia produced by contagious diseases, or arising from vegetable and animal matter in a state of putrefaction. It is accordingly employed in large quantity for bleaching and fumigation, and it is used for those purposes either in the gaseous state, or in combination with lime or an alkali, and dissolved in water. Aqueous chlorine is also frequently em- ployed on the small scale, and a number of experiments may be made with the solution already directed to be prepared by pouring it into solutions of vegetable colouring matter, as litmus, tumeric, indigo, and to others in a state of putrefac- tion, when their colour and odour will be completely destroy- 6 CHLORINE. 101 ed, if added in sufficient quantity. The method of making chloride of lime and Labarraque's disinfecting soda liquor will be described under their respective bases. 432. Suspend some coloured flowers in a bottle of chlorine gas after putting in a few drops of water ; in a short time they will in general have become of a pure white colour, but some are much more speedily deprived of colour than others. 433. When chlorine gas is perfectly dry, vegetable colour- ing matter is not at all affected by it, and from a variety of experiments made with substances of this nature, it appears that chlorine acts principally by decomposing water, combin- ing with its hydrogen and forming muriatic acid, while the oxygen that is eliminated acts directly on the colouring mat- ter and destroys it. 434. A number of inflammable substances burn in chlorine gas, and many of them take fire when mixed with it at natu^ ral temperature. 435. Light a candle suspended by a wire (Fig. 4, page 3,) and put it into a bottle of chlorine gas. It will continue to burn, but with a dull red flame, and a large quantity of car- bon is deposited. The combustion is sustained by the chlo- rine combining with the hydrogen of the inflammable matter, while the carbon is precipitated. 436. Pour some oil of turpentine on the lower part of a piece of thin gray paper folded into a match, allow any excess to drop off, and then put it into a bottle of chlorine, hold- ing it with a pair of pincers. The oil of turpentine will immediately take fire and burn with a lurid flame, the same reaction taking place as in the preceding instance,, and with a similar deposition of carbon. 437- Mix half a measure, or one equivalent, of olefiant gas (a few cubic inches of the gas or a much larger quantity may be employed) with a whole measure or one equivalent of chlo- rine in a glass jar, and apply a light to the mixture ; it will burn quickly with a flame similar to what is produced by the combustion of oil of turpentine in chlorine, the hydrogen com- bining with the chlorine and forming muriatic acid, while the carbon is precipitated. (See Hydrocarburet of Chlorine.) 438. Introduce a piece of phosphorus (well dried, 224) 182 CHLORINE. into another bottle of chlorine, using the copper cup repre- sented by Fig. 32, (page 48.) It immediately takes lire and continues to burn for a considerable time with a pale flame, combining with the chlorine and forming bichloride of phos- phorus ; a grain or two will be quite sufficient for a small bot- tle of the gas. 439- All the metals can combine with chlorine ; many of them take fire in this gas at natural temperatures, when in- troduced into it in a minute state of division, and the greater number of them when exposed to heat, with the exception of gold, silver, lead, cobalt, and nickel. To see the phenomena attending the combination, put some leaves of Dutch gold, a compound of copper and zinc, into the cage represented by Fig. 33, (page 48,) and introduce it into a bottle filled with chlorine ; it immediately inflames, and chlo- rides of copper and zinc are formed. 440. Throw some antimony or arsenic reduced to powder in a mortar into another bottle of chlorine ; the metal imme- diately inflames and combines with the chlorine. 441. Put some mercury into a copper cup (Fig. 32.) rub- bed over with a little gas lute to prevent them from combin- ing, and place it in a bottle of chlorine after heating it in the flame of a spirit lamp. It takes fire, burning with a reddish coloured flame, and is converted into bichloride of mercury. 442. Chlorine can decompose many of the metallic oxides (including the alkalis and earths) at a high temperature ; and, in general, an equivalent of oxygen is disengaged for every equivalent of the oxide that is decomposed, one equivalent of a metallic chloride being at the same time formed. The me- tallic oxide to be decomposed is placed in a coated porcelain tube, which is made to traverse a furnace in the usual man- ner, the chlorine being prepared in a flask or retort, and pass- ed over fragments of fused chloride of calcium (to remove any water before it comes in contact with the oxide) placed in a small globe or tube attached to its beak, and luted with plaster of paris to the porcelain tube. The oxygen evolved is collected in a jar over the pneumatic trough, to which it is conducted by a bent glass tube fixed to the other extremity of the porcelain tube. The current of chlorine PREPARATION OF PROTOXIDE OF CHLORINE. 183 should be passed slowly but steadily over the oxide, and it is better to employ a tubulated retort. 443. Chlorine is detected by a solution of the nitrate of sil- ver, which gives a dense white curdy precipitate with it, com- posed of chlorine and metallic silver ; it is soluble in ammonia, but insoluble in acids, and becomes of a dark colour on expo- sure to the light. Sect. I. — Protoxide of Chlorine. Equivalent by weight 44 (Owyg. 8+36 Chlor.) ; by volume f~l— , (One measure and a quarter) Specific Gravity 2.4 ; weight of 100 cubic inches, ^ '4.5 grains. 444. The protoxide of chlorine is prepared by pouring one part of muriatic acid, diluted with an equal weight of water, on two parts of the chlorate of potash, (one or two drachms will be quite sufficient,) and collecting the gas that is disen- gaged over the mercurial trough, applying a very gentle heat by a small spirit lamp. Great care ought to be taken in pre- paring this gas, as it explodes violently when exposed to a moderate heat, though nothing is mixed with it ; the spirit lamp should be held immediately below the retort, so as not to play on its sides, and the gas should then come slowly away, producing a very moderate effervescence. A portion of chlorine is always disengaged along with it, and is removed by the mercury which immediately combines with it, but does not affect the protoxide. 445. When it is not required particularly pure, it may be collected in small bottles or tubes by displacement, in the Fig. 54. manner represented in the annexed Fig. (54.) For this purpose, the extremity of the neck of a tubulated retort is fixed to a tube bent at right angles, and introduced into a bottle to be filled with the gas ; or a flask with a bent tube adapted to it, in the manner represented in the figure, may be employed. When the materials have been put in, and the gas begins to be disengaged. 184 PREPARATION OF PROTOXIDE OF CHLORINE. it occupies the lower part of the bottle, being much heavier than the atmospheric air, which is gradually displaced ; the blocks supporting the bottle are removed when it is full, which is easily known by the deep colour of the gas, and more bot- tles filled in the same manner. 446. The protoxide of chlorine is formed in this process by the mutual action of the muriatic and chloric acids. One part of the muriatic acid employed combines with the potash of the chlorate of potash and disengages chloric acid, a compound of chlorine and oxygen ; and another portion of the muriatic acid (which is composed of chlorine and hydrogen,) reacts on it in its nascent state, the hydrogen taking away part of its oxygen, while its chlorine combines at the same time with another portion of this element, forming part of the protoxide which is evolved, and the chlorine of the chloric acid, still re- taining one equivalent of oxygen, gives an additional quantity of this gas. The following diagram is intended to illustrate the decomposition, supposing one equivalent of chloric acid to have been already set at liberty by a corresponding pro- portion of muriatic acid, and reacting on two other equivalents of this acid: — Before decomposition. After decomposition. f Hyd. 1 — y 9 Water. 71 Muriatic acid, J Hd> J ./.. 7 9 Water. = 37x2. -< Chlor>36 CChlor. 36 Chlor. 36 Oxyg. 8 76 Chloric acid, < Oxyg. 8 I Oxyg. 8 \\\ 44 Protoxide of Chlorine. Oxyg. 8 AA 44 Protoxide of Chlorine. .Oxyg. g_ \ 44 Protoxide of Chlorine. The free chlorine that is always mixed with the protoxide must arise from the muriatic and chloric acids reacting on each other in different proportions. When a great excess of strong muriatic acid is mixed with the chlorate of potash, the chloric acid loses all its oxygen, and nothing but chlorine gas is disengaged. It is evident on inspecting the above diagram, PREPARATION OF PEROXIDE OF CHLORINE. 185 that if one equivalent of chloric and five of muriatic acid mu- tually decompose each other (instead of the two represented there,) five equivalents of water will be formed, and six of chlorine disengaged. 447. The protoxide of chlorine has a rich greenish yellow colour, from which Sir H. Davy gave it the name of Euchlo- rine ; its odour resembles that of burned sugar. It has no acid properties, destroys the vegetable colours, and is absorb- ed in considerable quantity by water, which can take up about ten times its volume of this gas. 448. Introduce a red hot iron wire bent at one end, or a lighted candle, into a strong tube or detonating bottle filled with the protoxide of chlorine ; an explosion immediately takes place, and a flash of light is at the same time perceived. The detonation arises solely from the separation of the elements of this compound, in which they exist in a condensed state, and certainly no one could have anticipated that this would have been accompanied by an evolution both of heat and light. If the explosion has been occasioned by a combustible substance, it will continue to burn afterwards in the mixed gases. Every measure and a quarter of the gas expands during decomposi- tion to a measure and a half, one measure of which (one equivalent) is chlorine, and the remaining half measure cor- responds with the equivalent of oxygen. 449. Phosphorus takes fire in this gas, and with hydrogen a detonating mixture is formed. The proper proportions are two measures (two equivalents) of hydrogen to every measure and a quarter of the protoxide ; the mixture must be inflamed by an electric spark, or a lighted match ; the products are water and muriatic acid. Sect. II. — Peroxide of Chlorine. Equivalent by weight 68 (occyg. 32+36 chlor.J; Equivalent by volume, I I 1 (two measures) ; Specific gravity, 2.36; weight of 100 cubic inches, *J2 grains. 450. This is another gas which must be prepared with the greatest caution, and only in small quantities at a time ; it 186 PREPARATION OF PEROXIDE OF CHLORINE- will be better for the beginner to pass on to the succeeding experiments, and defer preparing it till he shall have become more familiar with chemical manipulation, if he is left entirely to his own resources in conducting the process. It has the same general properties as the protoxide of chlorine, but has a deeper colour, explodes with much more violence, and at a lower temperature ; every two measures (one equivalent) ex- panding to three measures, one of which is chlorine (one equi- valent,) and the other two consist of oxygen, (four equiva- lents.) 451. It is obtained by mixing powdered chlorate of potash (60 grains may be taken) with no more sulphuric acid than is necessary to convert it into a solid paste ; the mixture is put into a small tubulated retort, the body of which is placed in hot water, taking care not to allow it to arrive at a boiling temperature, in case of the peroxide exploding ; it may be col- lected as it is disengaged over mercury, which has no action on it. 452. Instead of preparing a considerable portion of gas in a retort, a sufficient quantity to show the facility with which it may be exploded may be obtained by putting a few drops of sulphuric acid on a grain or two of the salt at the bottom of a glass tube, and holding it over a spirit lamp when the tube is full of gas, or introducing a hot iron wire. (Faraday.) The tube I generally employ is made of light green glass, very stout, about three inches long, and half an inch in diameter. No cork is put in ; the explosion is very loud, and a flash of light is at the same time perceived ; a mask should always be put on while performing this experiment, and a glove on the hand, as I have repeatedly seen a tube about the same size blown to pieces, notwithstanding the small quantity of gas which it contained. 453. To understand the theory of the process, it must be recollected that chloric acid is composed of five equivalents of oxygen and one of chlorine, so that it may be regarded as a compound of one equivalent of the peroxide of chlorine and one of oxygen. Two equivalents of sulphuric acid decompos- ing two of the chlorate of potash, two of sulphate of potash are formed and two of chloric acid are disengaged ; these react on CHLORIC ACID. 187 another equivalent of chloric acid in combination with potash, each losing one equivalent of oxygen, and being converted into peroxide of chlorine, and the oxygen combining with the other forms perchloric acid, which still remains united with the po- tash. The following diagram gives a clearer view of this com- plicated action. Before decomposition. After decomposition. f Perox. Chi. 68 68Perox. of chlorine. 2 Equiv. of j Perox. Chi. 68 68 Perox. of chlorine. Chloric acid j Oxygen . . 8\ [Oxygen . . 8^\. Chloric acid . . . ^6— _£^92 Perchloric acid. 454. Peroxide of chlorine has an aromatic smell, and none of the peculiar odour of chlorine. It is not affected at common temperatures by any of the simple inflammables except phos- phorus, which inflames and decomposes it, burning brilliantly afterwards in the mixture of chlorine and oxygen that remains. 455. It is even capable of inflaming phosphorus under wa- ter, which may be easily done by putting 30 or 40 grains of the chlorate of potash into a long narrow glass, filling it with cold water and pouring sulphuric acid on the chlorate through a funnel that reaches to the bottom of the glass, after throw- ing in a few grains of phosphorus cut into thin slices ; small quantities of acid must be added at a time, and the peroxide is disengaged, inflaming the phosphorus as it rises through the water. Sect. III. — Chloric Acid. Equivalent *]6 (Oxygen 40 + 36 Chlorine.) 456. This acid was at one time termed the hyperoxymuria- tic acid, from the opinion that it was composed of muriatic acid and oxygen, but it is now regarded as a compound of chlorine and this element. To prepare chloric acid, sulphuric acid diluted with ten or twelve times its weight of water is added to a weak solution of 188 PREPARATION OF CHLORIC ACID. the chlorate of barytes, as long as it gives any precipitate, taking care not to add an excess. The precipitate which falls is sulphate of barytes, and the chloric acid remains in solution. 457. The chlorate of barytes is prepared by transmitting a current of chlorine through a solution of barytes in water, placing it in one of the bottles of Woulfe's apparatus, (Fig, 40, p. 74)* Muriate of barytes is formed at the same time, every six equivalents of chlorine decomposing five of water, and producing five equivalents of muriatic and one of chloric acid, both of which remain in combination with the barytes ; the following table shows the proportions in which the chlorine and the water react on one another in equivalent numbers, and the quantity of resulting products : Water. Chlorine, New compounds. , Hyd. 1 + 36 = 37 Muriatic acid. 1 Hyd. 1 4- 36 = 37 Muriatic acid. 5 equivalents of wa- J Hyd. 1 + 36 = 37 Muriatic acid, ter = 9 x 5 = 45. \ Hyd. 1 + 36 = 37 Muriatic acid. I Hyd. 1 + 36 = 37 Muriatic acid. VOxyg. 40 4- 36 == 76 Chloric acid. 458. The muriate of barytes is separated from the chlorate by boiling the solution with phosphate of silver, phosphate of barytes and chloride of silver being formed by double decom- position, both of which are insoluble, while the chlorate of ba- rytes remains in solution. 459. Instead of preparing chlorate of barytes and decom*. posing it by sulphuric acid to obtain chloric acid, which is not applied to any particular use in its pure state, it will be more interesting to the beginner to prepare some chlorate of potash, the most important of the salts of this acid, by transmitting chlorine through a solution of caustic potash in the same man- ner as in the preparation of the chlorate of barytes. The re- action that ensues is exactly the same in both cases, muriate and chlorate of potash being formed in the present instance. The chlorate is deposited in crystals from the solution, but the muriate being more soluble remains dissolved. Instead of using caustic potash, a strong solution of the carbonate is gc MURIATIC ACID. 189 nerally employed ; the siliceous matter which the common car- bonate always contains is deposited first, rendering the liquid cloudy and mixing with the chlorate of potash ; it is separated by dissolving the crystals in the smallest quantity of hot water that will take them up, which deposits crystals again as it cools. The carbonic acid of the carbonate is separated with efferves- cence. 460. Five parts by weight of the peroxide of manganese with a proper proportion of muriatic acid may be taken for every eight parts of the carbonate of potash. 461. Chloric acid reddens the vegetable blues, is decompos- ed by a number of substances which have a great affinity for oxygen, and forms an important class of salts, all of which are decomposed by heat, and distinguished by the violent action that takes place when they are exposed to heat along with in- flammable matter ; with many of them it detonates at natural temperatures by friction or percussion. Perchloric Acid is formed by the reaction of sulphuric acid on chlorate of potash (see 473) ; its properties have not been very particularly examined. Sect. IV. — Muriatic Acid. Equivalent by weight, 37 ,* (chlorine 36+1 Hydrogen); by volume f I I (2 measures). Specific gravity 1.28. Weight of 100 cubic inches 39-18 grains. It requires a pressure of 40 atmospheres to render it liquid at 50. 462. This important compound, the Hydrochloric Acid of the French chemists, exists always in the gaseous state at natural temperatures and under ordinary pressure, and this term is commonly applied to a compound of it and water also known by the name of Spirit of Salt, being usually prepared by distillation from common salt (chloride of sodium) and sul- phuric acid. 463. The best process for the preparation of the common PREPARATION OF MURIATIC ACID. liquid muriatic acid is that adopted by the Edinburgh College. Common salt is exposed for an hour or two to a red heat in an earthen vessel to decompose any nitrates which it may con- tain, (a small quantity of these salts being occasionally found in it), and one part of it mixed with an equal weight of sul- phuric acid, previously diluted with a third of its weight of water, in a glass retort, pouring the acid upon the salt by a long funnel. (Fig. 34, p. 53). The retort is then placed in a sand bath and a receiver adapted to it, containing water equal in weight to two-thirds of the salt employed. The ma- terials should not occupy more than a third of the body of the retort, as it is apt to boil over when exposed to heat. The furnace is kindled after every thing has been properly adjust- ed, and the distillation continued to dryness ; the receiver is kept cold and the apparatus arranged in the manner repre- sented in Fig. 35, (p. 53), and when the atmospheric air in the retort and receiver has been expelled, which usually takes place a short time after the mixture begins to boil, the receiver may be luted to the neck of the retort with a little clay, tak- ing care always to keep it sufficiently cold by a constant stream of water. One equivalent of sulphuric acid (49) is capable of decomposing one equivalent of chloride of sodium and giving an equivalent of muriatic acid, but Dr. Hope found that when equal weights are employed the decomposition, as it is usually effected, is more complete, and a larger quantity of muriatic acid more easily procured. The acid gas produced by the action, and the water previously mixed with the materials are condensed in the receiver, and considerable heat is produced not only by the condensation of the watery vapour, but also by the combination of the muriatic acid gas with the water in the receiver. The specific gravity of the liquid obtained is 1.117 and contains about 34 per cent, of dry acid. 464. In this process, each equivalent of muriatic acid is formed by one equivalent of the chlorine of the chloride com- bining with the hydrogen of the water in the common sulphu- ric acid, the sodium taking the oxygen and forming soda, with which the sulphuric acid at the same time unites, and is PREPARATION OF MURIATIC ACID. 191 converted into sulphate of soda : the excess of sulphuric acid (which is not represented in the following diagram) combines with part of the sulphate of soda and forms a bisulphate. Before decomposition. After decomposition. Hyd. . .1 "7'37 Muriatic Acid. 49 Common j £ ' ' " 8 v Sulphuric Acid1 Dr ^ ci ' d4{) \ 60 Chloride off Chlorine 36 •'' Sodium \ Sodium 24 — ^7^ Sulphate of Soda. Dilute some of the acid with an equal bulk of water, and drop into it a solution of the muriate of barytes ; if any preci- pitation takes place, it contains sulphuric acid from which it is separated by a second distillation with a small quantity of the chloride of sodium, (see 147). Bottles may be filled with- out a mercurial trough by displacement, in the manner de- scribed in 445. 465. Muriatic acid may be formed also by detonating a mixture of equal measures of chlorine and hydrogen ; the bottle should be filled half full of hydrogen first, and then filled up with chlorine, corking it immediately to prevent the absorption of any of the chlorine by the water. A lighted match is then applied in the usual manner, the mixture de- tonates with flame and a loud report, but no condensation at- tends the combination, two measures of muriatic acid gas be- ing formed. Pour in an infusion of litmus into the bottle im- mediately after the detonation ; it will be reddened by the muriatic acid ; if it had been poured in before the combination was effected, the chlorine would have rendered it colourless. 466. Fill the detonating bottle again with hydrogen and chlorine in the same manner and in the same proportions, cork it and expose it to the direct rays of the sun. A detonation takes place, and if the cork is not forced out, the muriatic acid gas will be completely absorbed on taking it out under water* If the mixture is kept in the dark no action takes place, and, in the shade, the chlorine and hydrogen combine slowly with- out detonation. 192 MURIATIC ACID. 467- When muriatic acid is required in the gaseous form it must be collected in jars or bottles over the mercurial trough, as it is instantly absorbed in large quantity by water. The easiest method of obtaining it is by exposing a strong so- lution of muriatic acid in water, (common liquid muriatic acid,) to a gentle heat in a small tubulated retort capable of contain- ing three or four ounces ; it may be filled half full, and a spirit lamp held in the hand will be found the most convenient me- thod of applying the heat. Muriatic acid gas is soon disengaged in large quantity, and may be collected after the air has been expelled from the retort ; no water is distilled over along with it till a considerable portion of gas has been expelled. A suf- ficient quantity should be collected at once for all the experi- ments it is intended to perform with it. 468. Muriatic acid gas has an acrid, pungent, and suffocat- ing odour, and has a strong acid taste even when combined with a large quantity of water. It is transparent and colour- less, produces fumes when mixed with the air combining with the watery vapour which it contains, and cannot support com- bustion or respiration. Muriatic acid gas has a very great affinity for water, which can absorb 480 times its bulk of this gas, considerable heat being produced by the combination, and the specific gra- vity of the resulting liquid being 1.21. 469- Take a long tube filled with the acid gas at the mer- curial trough, close it with the thumb or finger, transfer it to a bason of water coloured blue by an infusion of cabbage or litmus, and remove the finger under the surface of the water ; the gas is immediately condensed, the coloured water forced up into the tube with explosive violence by the pressure of the atmosphere, and reddened at the same time by the acid ; if any common air has been mixed with the gas, the absorption goes on more slowly and the air remains in the tube. 470. Fill a small test tube with water, and introduce a little (175) into a jar of muriatic acid gas over the mercurial trough ; observe the large quantity of gas it condenses, which is indicated by the rising of the mercury. MURIATIC ACID. 193 471. Put a piece of ice into another jar ; it is melted almost immediately and a solution of muriatic acid formed. 472. Take 300 grains (or any other quantity,) of the acid procured by distillation in the manner described, dilute it with an equal quantity of water, and drop into it fragments of mar- ble from a given weight of this substance till it will not dissolve any more. Then ascertain the quantity dissolved by weigh- ing what remains (washing with water and drying what may still be mixed with the liquid) and calculate the quantity of real muriatic acid which it contains, allowing 37 per cent, for every 50 grains of marble dissolved ; for 37 parts (one equi- valent) of real muriatic acid act on 50 parts of marble (= car- bonic acid 22 -\- 28 lime,) combining with the lime and disen- gaging the carbonic acid. 473. Fill a long tube half full of strong liquid muriatic acid, and pour water gently over it till the tube is full, then close the mouth with the finger rubbed over with a little wax lute and invert it till the two fluids are completely mixed. Heat is evolved, and when the mixture is cooled it will be found to occupy a smaller volume than the liquids before they were combined. 474. Strong liquid muriatic acid is transparent and colour- less when perfectly pure, emits copious fumes on exposure to the air, boils at 110, giving off muriatic acid gas, and freezes when exposed to a very low temperature. It has usually a light greenish yellow colour, from the pre- sence of a small quantity of chlorine or oxide of iron ; the for- mer is produced by a very minute portion of nitric acid (disengaged from some nitrates mixed with the salt by the sulphuric acid used in its preparation,) reacting on part of the muriatic acid, and the latter also from some impurities in the materials employed, or from the iron vessels in which it is prepared on the large scale. Ammonia added in excess pre- cipitates any oxide of iron that may be present ; chlorine may be occasionally detected by the smell, or by gold leaf which it speedily dissolves, pure muriatic acid having no action on it. 475. The following table, (abridged from Dr. lire's Dic- tionary,) shows the quantity of real acid in common muriatic acid at different densities. 194 MUKIATIC ACID. Table of Muriatic Acid by Dr. Ure. Specific Dry acid in [ Specific Dry acid in Specific Dry acid in Specific Drv acid in Gravity. li t* parts. j Gravity. 10W parts. | Gravity. 1CU parts. Gravity. lull parts. 1.2000 40.777 1.1515 30.528 ! 1.1000 20.388 1.0497 10.194 1.1982 40.369 1.1494 30.174 1.0980 19.980 1.0477 9.786 1.1964 39.961 1.1173 29.767 1.0960 19.572 1.0457 9.379 1.1946 39.554 1.1452 29.359 1.0939 19.165 1.0437 8.971 1.1928 39.146 1.1431 29.951 1.0919 18.757 1.0417 8.563 1.1910 38.738 1.1410 28.544 1.0899 18.349 1.0397 8.155 1.1S93 38.330 1.1389 28.136 1.0879 17.941 1.0377 7.747 1.1875 37.923 1.1369 27.728 1.0859 17.534 1.0357 7.340 1.1857 37.516 1.1349 27.321 1.0838 17.126 1.0337 6.932 1.1846 37.108 1.1328 26.913 1.0818 16.718 1.0318 6.524 1.1822 36.700 1.1308 26.505 1.0798 16.310 1.0298 6.116 1.1802 36.292 1.1287 26.098 1.0778 15.902 1.0279 5.709 1.1782 35.884 1.1267 25.690 1.0758 15.494 1.0259 5.301 1.1762 35.476 1.1247 25.282 1.0738 15.087 1.0239 4.893 1.1741 35.068 1.1226 24.874 1.0718 14,679 1.0220 4.486 1.1721 34.660 1.1206 24.466 1.0697 14.271 1.0200 4.078 1.1701 34.252 1.1185 24.058 1.0677 13.863 1.0180 3.670 1.1681 33.845 1.1164 23.650 1.0657 13.456 1.0160 3.262 1.1661 33.437 1.1143 23.242 1.0637 13.049 1.0140 2.854 1.1641 33.029 1.1123 22.834 1.0617 12.641 1.0120 2.447 1.1620 32.621 1.1102 22.426 1.0597 12.233 1.0100 2.039 1.1599 32.213 1.1082 22.019 1.0577 11.825 1.0080 1.631 1.1578 31.805 1.1061 21.611 1.0557 11.418 1.0060 1.224 1.1557 31.398 1.1041 21.203 1.0537 11.010 1.0040 0.816 1.1536 30.990 1.1020 20.796 1.0517 10.602 1.0020 0.408 476. The most delicate test of muriatic ?cid is a solution of the nitrate of silver, which gives a copious curdy precipitate of the chloride of silver, the hydrogen of the acid combining at the same time with the oxygen of the oxide ; chlorine, indeed, gives a similar precipitate, but its action on the vegetable co- louring matter distinguishes it sufficiently from the acid. 477- Muriatic acid combines with the salifiable bases and forms an important class of salts termed muriates. They are, in general, decomposed by heat, the hydrogen of the acid unit- ing with the oxygen of the oxide, the resulting products being water and a metallic chloride ; they are decomposed also by sulphuric acid. CHLORIDE OF NITROGEN. 195 Sect. V. — Chloride of Nitrogen. Equivalent 158 (chlorine 144 + 14 Nitrogen). 478. This compound detonates with great violence when touched with many inflammable substances, or exposed to heat, and probably also from several other causes which have not yet been discovered, as many accidents have taken place during its preparation, which have been attended with very serious consequences. 479. It is prepared by inverting a jar or wide-mouthed bottle (capable of containing about 12 or 14 ounces) full of chlorine over a dilute solution of the muriate of ammonia, made by dissolving an ounce of the salt in ten or twelve ounces of water. One portion of the chlorine takes the hydrogen of the ammonia forming muriatic acid, and the other combining with the nitrogen is converted into the chloride, which collects in the form of an oil on the surface of the liquid, and drops into a very strong shallow leaden cup on which the bottle is placed, resting on a plate containing the solution previously heat- ed to the temperature of 90 ; an additional quantity must be ready to fill up the plate as the absorption of the chlorine pro- ceeds. Great care must be taken not to shake the bottle, and any gas lute or fatty matter adhering to it must be removed by washing it with a dilute solution of potass before it is filled with chlorine. When it has fallen into the leaden cup, the bottle is carefully moved from the cup to the plate, and the matter taken cautiously away. 480. The liquid remaining above the chloride in the cup is withdrawn by dipping small pieces of filtering paper into it ? and on touching it with a drop of olive oil at the end of a stick at least two or three feet long, a loud explosion takes place, though the quantity of the chloride does not exceed the bulk of a pea. It is resolved at the same time into chlorine and nitrogen ; the manner in which inflammable substances act when they cause an explosion with it has not been ascertain- ed. 196 NITR0-MUHIAT1C ACID. 481. Its odour is extremely penetrating and almost insup- portable, affecting the eyes very much on leaning over it even for a second or two ; at natural temperatures it volatilizes rapidly, and explodes when heated to 200. Sect. VI. — Nitro-Muhiatic Acid. 482. There is no chemical compound of nitric and muriatic acids, (or at least it can exist only at low temperatures) these two substances decomposing each other and forming chlorine, water, and nitrous acids. Nitric acid may be regarded as a compound of nitrous acid and oxygen, and in the following table its composition is stated in this manner, that the nature of the reaction which takes place between it and muriatic acid may be more easily perceived : Before decomposition. After decomposition. Chlorine . 36 36 Chlorine. 1 9 Water. 37 Muriatic Acid < „ , ~ ' l Hydrogen 54 Nitric Acid | Nitrous Ac> 46 46 Nitrous Acid. This compound, then, though still called the Nitro-Muria- tic Acid (known also by the name of Aqua Regia, from its power of dissolving gold), is in reality composed of chlorine, water and nitrous acids ; its characteristic properties depend or* the presence of free chlorine. 483. It is prepared usually by mixing two measures of nitric with one of muriatic acid, but various proportions are employed for different purposes. The nature of the reaction, the deep red colour which the liquid assumes, and the disen- gagement of chlorine, may be easily seen by mixing half an ounce by measure of muriatic acid with an ounce of the ni- tric, and exposing the mixture to a gentle heat in a flask. CHLORIDE OF SULPHUR. 197 Sect. VII. — Chlorides of Sulphur, Phosphorus, Carbon, Hydrocarburet of Chlorine, and Chlorocarbonic Acid. 484. Chloride of Sulphur is prepared by transmitting chlorine over flowers of sulphur in a coated glass or porcelain tube moderately heated. It is a reddish coloured liquid, easily volatilized, and emits very acrid irritating fumes. It decom- poses water, alcohol, and ether, a portion of sulphur being deposited and the remaining sulphur converted into sulphur- ous and sulphuric acids by the oxygen which it takes from these substances, the chlorine at the same time uniting with hydrogen and forming muriatic acid. 485. The method of preparing the Protochloride of Phosphorus, and the only use to which it has been applied is described in 283. The Bichloride of Phosphorus is formed when phosphorus is introduced into chlorine ; water and the bichloride mutually decompose each other, the two proportions of chlorine taking two of hydrogen and giving two of muriatic acid, while the phosphorus combining with two of oxygen is converted into phosphoric acid. 486. Hydro-Carburet of Chlorine is prepared by mixing two measures of chlorine with one of olefiant gas, and leaving the mixture over water. The gases combine slowly together forming a few drops of an oily liquid which must be washed with water, and purified by distillation after mixing it with some chloride of calcium to retain any water that may be adhering to it. Its taste is sweet ; it boils about 150, and is completely decomposed by a red heat. 487- By exposing this compound repeatedly to the action of chlorine gas exposed to the rays of the sun, Mr. Faraday succeeded in obtaining a compound of chlorine and carbon, the hydrogen being removed and converted into muriatic acid. It has received the name of Perchloride of Car- bon, for the details of the process for preparing this com- 198 IODINE. pound, I must refer to Mr. Faraday's paper in the Philoso- phical Transactions for 1821. When its vapour is passed through a red hot porcelain tube a large quantity of chlorine is disengaged, and a liquid is obtained which is composed of one equivalent of carbon and one of chlorine, the Proto- chloride of Carbon. Another compound of chlorine and carbon, the Subchloride of Carbon, has been described in the first volume of the new series of the Annals of Philo- sophy. 488. Chlorocarbonic Acid is a compound of chlorine and carbonic oxide gas discovered by Dr. John Davy, it has been called Phosgene gas from its being formed by the action of light on the mixed gases. It is transparent, and colour- less, reddens litmus paper, combines with ammonia and is de- composed by water, when carbonic and muriatic acids are produced, the hydrogen of a portion of water combining with the chlorine, and the oxygen with the carbonic oxide. The composition of these substances is stated in the table of equivalents in page 176. CHAP. X. IODINE. Equivalent by weight 124 ; by volume, Q. Specific gra- vity of solid iodine 4.948 ? Specific gravity of the vapour of iodine 8.61. Weight of 100 cubic inches 262.26 grains. It requires 7000 parts of water for its solution, but is 'much more soluble in alcohol and ether. It volatilises at natural temperatures, melts at 227, an & sublimes at 350. 489- Iodine is a substance that bears a great resemblance to chlorine in all its chemical relations ; it was discovered by PREPARATION OF IODINE. 199 M. Courtois in 1812. It is obtained usually from the ashes of incinerated marine plants. 490. The process usually followed for the preparation of iodine was proposed by Dr. Ure. The liquid that remains after most of the saline matter has been extracted from kelp* is heated to the temperature of 230, poured into a stone ware bason (which should not be filled more than half full) and an ounce by weight of sulphuric acid, previously diluted with an equal bulk of water, mixed with every eight ounces by measure of the liquid employed ; a brisk effervescence im- mediately takes place, a large quantity of sulphur is at the same time precipitated, and crystals of the sulphate of soda are deposited when the mixture is cold. 491. The salts which this fluid contains are composed principaHy of soda combined with sulphureted hydrogen, carbonic, sulphurous and hydriodic acids, a 1 ! of which are se- parated by the sulphuric acid, which combines with the soda and forms the sulphate that is afterwards crysta^.ized. The carbonic acid mixed with part of the sulphureted hydrogen and sulphurous acids produces the effervescence as they are disengaged, the rest of the latter acids mutually decomposing each other, the hydrogen of the one combining with the oxygen of the other, while the sulphur of both is precipitated ; the hydriodic acid which remains in the liquid, is separated from the sulphur by filtration through paper. 492. In the last stage of the process, the iodine is obtained by mixing 1000 grains of the peroxide of manganese with every 12 ounces by measure of the filtered liquid in a glass retort (capable of containing at least 24 ounces when quite full), condensing it in a receiver which is kept cold in the usual manner. Dr. Ure recommends a glass flask to be used, and the iodine, which is deposited in small crystals, to be condensed in a large globe or receiver placed above it in the * Kelp is the term applied to the ashes of incinerated sea-weed prepared on the coast of Scotland, and is used in large quantities by many of the soap manufacturers in this country from whom the above liquid is generally pro- cured. 200 PREPARATION OF IODINE. Fig. 55. manner represented in Figure 55, inter- posing a disc of wood (a tin plate does better) with a hole in the centre between the flask and the receiver, that the latter may not be heated too much by the hot air ascending from the chauffer ; a mix- ture of cinders and charcoal gives a better fire for this purpose than either of them separately. When the globe becomes warm from the condensation of iodine and watery vapour, it must Jbe removed and another put in its place, washing the iodine out with a small quantity of water, that it may be ready to replace the other. When the prepared iodine liquor has been kept some weeks before it is used, sometimes little or no iodine is ob- tained on heating it with peroxide of manganese ; in such cases I have found that the addition of a little caustic potash causes the iodine vapours to appear in as large a quantity as if the liquid had been newly prepared. From 80 to 100 grains of pure iodine are obtained from this quantity of liquid. 493. The theory of the process is similar to the theory of the preparation of chlorine from muriatic acid. Hydriodic acid is composed of one equivalent of hydrogen and one of iodine, and water, iodine, and hydriodate of manganese result from the mutual reaction of two equivalents of this acid and one of the peroxide of manganese ; the following diagram gives a more precise view of the nature of the action which takes place : Before decomposition. 125 Hydriodic V Hydrogen acid . "^ Iodine . 125 Hydriodic acid U Peroxide of (Oxygen . Manganese j ProtOX.Mang.3o After decomposition. 9 Water. 124 Iodine. 161 Hydriodateof Maiij 494. If, however, an excess of sulphuric acid is present in the liquid, which is generally the case, then all the hydriodic PREPARATION OF IODINE. 201 acid is decomposed, sulphate of manganese being formed, and the oxygen disengaged from the peroxide uniting with the hydrogen of the hydriodic acid. 495. As the liquid directed to be used in the preceding process cannot be so easily procured now, all the soap manu- facturers in the neighbourhood of this town at least usins: very little kelp, and obtaining the soda they require principally from other sources, a little pure hydriodic acid may be mixed with the peroxide of manganese in a small tube or glass re- tort, to show the action that takes place.* 496. Iodine is a solid substance of a dark bluish black colour and metallic lustre ; when slowly sublimed, its vapour condenses in rhomboidal plates. It has a pungent odour, an acrid taste, stains the skin of a deep brownish yellow colour, and destroys the vegetable colours, though it acts more feebly upon them than chlorine. With oxygen, hydrogen, nitrogen, sulphur, phosphorus, and the metals, it forms an important class of compounds, similar in their general chemical relations to those which chlorine forms with the same substances. 497- Put a f ew grains of iodine into a large glass flask, and expose it to a gentle heat. The iodine will be sublimed and form a rich violet coloured vapour, which condenses in crystals as it cools. 498. Boil a little more with live or six ounces of water in a Florence flask. The vapour of iodine rises along with the vapour of the water at. 212. 499- Cut three or four very thin pieces of phosphorus and throw a little iodine upon them after they have been well dried, placing them on a tin cup. They combine together, considerable heat is produced, and part of the phosphorus is generally inflamed. If the mixture is made in a small tube filled with mercury and inverted in a cup of the same liquid, or over the mercurial trough, they immediately combine together, but no light is disengaged ; it appears only when * The kelp liquor which I use for showing the method of preparing iodine is procured from Glasgow, Dunfermline, and other places where it is still employed by soap manufacturers. 202 PREPARATION OF IODINE, part of the phosphorus is inflamed by the heat produced, and combines with the oxygen of the air. 500. Make a strong solution of starch in boiling water, and mix some iodine with it ; a compound is formed immedi- ately of a very deep blue colour. Pour some boiling water upon it and the mixture will become quite colourless ; the nature of the changes that take place on the addition of the hot water have not been minutely examined. Starch is the most delicate test of iodine which we possess, and it is stated, that with this substance, one part of iodine may be detect- ed in 450,000 of water ; and if we drop a solution of starch into a solution of iodine in water, and observe the deep blue colour which is immediately produced, though this liquid can dissolve only -gyodth part of its weight of iodine, we shall not be inclined to doubt the accuracy of the statement. 501. The best method of detecting minute proportions of iodine in solution was pointed out by M. Balard. The Fquid suspected to contain it is mixed with a solution of starch, and sulphuric acid added in excess, chlorine water is then poured over it ; a blue band is perceived where the two liquids meet if any iodine is present, and though it may be very feeble, it is in general distinctly recognised on contrasting it with the liquids above and below. The sulphuric acid sepa- rates the hydriodic acid (for this is the form in which iodine usually exists) from any base with which it may be combined, and the chlorine taking the hydrogen disengages the iodine, which immediately combines with the starch. The blue com- pound is produced solely by their combination ; pure hydrio- dic acid has no action on starch. 502. If the proportion of hydriodic acid in solution is not exceedingly small, the sulphuric acid reacts on it and dis- engages a portion of iodine which immediately produces the characteristic blue colour with the starch, though no chlorine is added. To see this, dissolve a grain of the hydriodate of potash in a few ounces of water, and pour a solution of starch into it after adding a drop or two of sulphuric acid. If the solution is strong, iodine vapour is disengaged on adding strong sulphuric acid ; Dr. Fyfe found that this takes place PREPARATION OF IODIC ACID. 203 also when the acid is added to a concentrated infusion of algae in hot water. 503. In all these experiments for detecting iodine, cold water must be employed, as the blue compound of iodine and starch is decomposed by hot water. 504. Iodine is frequently employed in medicine and acts as a virulent poison when given in an over dose. The pro- per antidotes are large quantities of starch and other muc :i : - ginous substances dissolved in water. Sect. I. — Iodic Acid. Equivalent 164. (Oxygen 40 + 124 Iodine.) 505. Two compounds of iodine and oxygen are usually described, only one of which has hitherto been obtained in a pure state, viz. Iodic Acid. The other, termed Iodous Acid was supposed to be formed when equal parts of iodine and chlorate of potash are triturated together in a glass mortar and the mixture exposed to heat, but more recent investiga- tions have not confirmed this opinion. 506. Iodic acid is obtained most easily by a process pointed out by Sir H. Davy. Protoxide of chlorine, prepared by pouring 400 grains of muriatic acid, specific gravity 1.105 on 100 of the chlorate of potash in a tube retort and applying a gentle heat (See 444.) is distilled into a small thin glass re- ceiver containing about 40 grains of iodme, a few pieces of chloride of calcium being put into the neck of the retort. An evolution of heat and light takes place when the protoxide comes in contact with the iodine, one portion of which com- bining with its oxygen is converted into iodic acid, and the rest unites with the chlorine, forming a compound which is easily separated from the iodic acid by a moderate heat. 507- It is a white semitransparent solid substance, having a very acid astringent taste, and is decomposed when heated to 390. It is soluble in water and deliquescent, reddens and then destroys the vegetable blues. Its salts are termed iodates. Many of them may be prepared by the mutual action of their 204 PREPARATION OF HYDRIODIC ACID. bases on water and iodine, the same reaction taking place that has been already described with respect to chlorine (457?) every six equivalents of iodine decomposing five of water and forming one of iodic and five of hydriodic acid, both of which remain in combination with the oxide employed. They deton- ate with inflammable substances and have the same general properties as the chlorates. Sect. II. — Hydriodic Acid. Equivalent by weight 125, (Iodine 124 + 1 Hydrogen.} Equivalent by volume, 1 I [ . Specific gravity 4.337, weight of 100 cubic inches 132.189 grains. Specific gravity of common liquid hydriodic acid (hydriodic acid gas dissolved by water) 1.5 ? 508. Hydriodic acid gas is prepared by mixing one part of phosphorus with ten of iodine moistened with water, and put pre- viously into a very small glass retort or flask, applying a gen- tle heat with a spirit lamp. In a very short time, a brisk reaction commences, a slight explosion generally taking place within the retort from the heat produced inflaming a portion of phosphorus, and also from the disengagment of a little phosphureted hydrogen. Dense vapours are at the same time disengaged, and the hydriodic acid gas may be collected by displacement (445, Fig. 54.) after these have been expelled. Water absorbs it as rapidly as muriatic acid gas, and it cannot be kept long over mercury, as this metal begins to act upon it whenever they come into contact, mercury combining with the iodine, and leaving hydrogen gas. A few drops of water should be introduced from time to time by a small pipette, as phosphuret of iodine is sublimed into the neck of the retort when the materials are dry and no gas is produced. Phos- phureted hydrogen is disengaged in considerable quantity to- wards the end of the operation ; when it begins to come, it is recognised by the acid gas with which it is mixed, producing a whiter coloured vapour than usual with the air ; the process PREPARATION OF HYDRIODIC ACID. 205 should then be stopped to prevent it from accumulating. Con- stant attention must be paid to this operation while it is going on. 509. A number of complicated changes take place during the preparation of this gas, from the reaction of the different substances mixed together and part of the newly formed pro- ducts. The hydriodic acid gas is produced by the iodine com- bining with the hydrogen of a portion of water which is de- composed, the oxygen going to the phosphorus and forming phosphoric acid which remains in the retort and acts upon the glass if the heat is urged after it has been formed. Supposing the reaction to take place between two equivalents of iodine, two of water, and one of phosphorus, and no other compounds to be produced, the following diagram will convey a clearer view of the manner in which the different substances arrange themselves. Iodine .... 124 ~>'~ 125 Hydriodic Acid. Iodine ...» 124 ~-~s-~p* 125 Hydriodic Acid. 9 Water x 2 / Hyd. . 1 Hyd. . 1 Oxyg. . 8 Oxyg. . 8 Phosphorus . 12 — ^"^ gO Phosphoric Acid. Fifty or a hundred grains of iodine with the proper quantity of phosphorus will be found quite sufficient, using a retort ca- pable of containing about five or six ounces of water. 510. When a solution of hydriodic acid in water is requir- ed, in which state it is usually kept as a test, the process which I have found most convenient is to decompose the iodide of starch suspended in water by a stream of sulphureted hy- drogen. (Journal of Science, New Series, No. viii.) Sixty grains of iodine are dissolved in three ounces of alcohol (in the cold) and an ounce of starch reduced to a very fine powder dif- fused in four ounces of water, adding this, drop by drop, to the first solution, and stirring it constantly at the same time ; iodide of starch is formed, and the clear liquid is decanted after it has subsided. A little water is then poured on it to remove any 6 206 PREPARATION OF HYDRIODIC ACID. alcohol that may be still mixed with it, and after it has been removed, the iodide is diffused through an ounce of water, and a stream of sulphureted hydrogen from 400 or 500 grains of the sulphuret of iron (196) passed through it till it becomes white. The liquid is then filtered to remove the starch and sulphur that are disengaged, and boiled for a short time to ex- pel any excess of sulphureted hydrogen. The iodide of starch may be put into a common precipitate glass or jar when it is diffused through water, and the sulphureted hydrogen prepar- ed in a bottle with a bent tube fitted to it, (Fig. 44, p. 91), or any of the other forms of apparatus that may be preferred. 511. In this process, the hydrogen of the sulphureted hy^ drogen combines with the iodine of the iodide of starch and forms the hydriodic acid, which remains in solution, the sul- phur and starch being separated ; none of the starch is taken up by the solution, as it is insoluble in cold water. The mix- ture passes through a variety of shades of colour from the deep blue of the iodide to a rich brownish red, orange and yellow colour before it becomes ultimately white ; these changes suc- ceed each other rapidly and present a very beautiful appear- ance when the sulphureted hydrogen is quickly evolved. 512. A solution of hydriodic acid in water may be obtained also by transmitting sulphureted hydrogen through iodine re- duced to a fine powder and suspended in water, the hydrogen combining with the iodine and the sulphur being deposited. I prefer the process already described, as the iodine is obtain- ed in a much more minute state of division than it can be pro- cured by trituration, and the sulphureted hydrogen acts more readily upon it in this state. In both cases, the liquid acid may be concentrated by evaporation till it is obtained of the specific gravity of 1.5, continuing the application of the heat for this purpose till its boiling point rises to 260 or 262. 513. In this state, it is a transparent and colourless liquid, having very strong acid powers and effervescing with carbon- ates. It acquires a deep colour on exposure to air and light, from the decomposition of a minute portion of acid and the se- paration of iodine. HYDUIODIC ACID TESTS. 2U/ 514. Pour in a small quantity of the acid into a solution of litmus ; the colour immediately changes to a red. 515. Pour a few drops into seven glasses, each containing an ounce or two of water. To the first, add a single drop of a solution of the chloride of platina, the whole liquid will im- mediately become of as deep a reddish brown colour as the strong solution of the chloride employed, and after some time a dark brownish black precipitate is formed. The chloride of platina is the most dedicate test of hydriodic acid which we possess. Into the other glasses pour a few drops of the foUowing li- quids : — 1. A solution of the nitrate of silver ; a yellow precipitate immediately appears. 2. A solution of the bichloride of mercury gives a precipi- tate which appears yellow at first, but soon becomes of a brick red colour. 3. A solution of pernitrate of mercury gives a similar preci- pitate. 4. A solution of the acetate of lead gives a yellow precipi- tate. All these precipitates are compounds of the iodine of the acid with the metal of the solution employed. 5. Strong nitric or sulphuric acid decomposes it. 6. Chlorine water produces the same effect, the hydrogen being withdrawn and the iodine set at liberty ; a solution of starch may be added afterwards to produce the characteristic blue precipitate. 516. With the hydriodic acid gas co^ected by displace- ment, several experiments may be performed. If any has been collected over mercury, it should be used as soon as it is prepared, leaving one jar to show its complete decomposition by this metal, and that half its bulk of hydrogen remains. 517- Remove a tube filled with the gas in the manner di- rected in 469, and take the finger off the mouth under water ; the gas will be absorbed as rapidly as muriatic acid gas, if it is perfectly pure. 518. Introduce a small quantity of water into a jar full of 208 HYDRIODIC ACID. the gas over mercury (175) to show the large quantity which it can absorb. 519- Fill a small jar half full of chlorine over the mercurial trough, and transfer it immediately under the mercury to an- other jar half full of hydriodic acid gas ; the chlorine com- bines immediately with the hydrogen of the hydriodic acid forming muriatic acid gas, and the iodine is deposited. 520. Invert ajar full of hydriodic acid gas with an earthen tray, and pour into it a little of the strong fuming acid com- posed of nitric and nitrous acids. The hydrogen of the hy- driodic acid immediately combines with the oxygen of the acid and iodine is set at liberty ; the mixture often inflames, and I have seen this when the experiment has been made with no more than two or three cubic inches of the gas. Sect. III. — Iodide of Nitrogen, Ci-iloriodic Acid, &c. 521. Iodide of Nitrogen is prepared by triturating iodine with ammonia, allowing the mixture to remain for 24 hours. Ammonia is composed of hydrogen and nitrogen ; part of the iodine combines with the nitrogen forming the iodide, which assumes the form of a black powder, and another portion un- iting with the hydrogen is converted into hydriodic acid, which remains in combination with the water of the ammonia. It detonates by slight pressure or on exposing it to a moderate heat over a chauffer, its elements being separated from one another. It may be prepared in a small evaporating dish, and detonated in the same vessel, after pouring off the solution of hydriodic acid. A few grains of iodine and a drachm or two of ammonia will afford a sufficient quantity to show its detonat- ing properties. 522. The action that takes place between iodine and phos- phorus has been already described (499)- A small quantity of the iodide of phosphorus i.s generally sublimed during the preparation of hydriodic acid gas (508), condensing in the neck of the retort ; if a little water is poured upon it an im- BROMINE. 209 mediate effervescence takes place, and a large quantity of hydriodic acid gas is produced, the iodide reacting on the water in the same manner as the mixture of iodine and phos- phorus. 523. Iodide of Sulphur is prepared by mixing iodine and sulphur together and exposing them to a gentle heat. 524. Chloriodic Acid or Chloride of Iodine is the name given to a compound of chlorine and iodine discovered by Sir H. Davy. It is prepared by admitting chlorine into an exhausted flask containing a fixed quantity of iodine. It has not been applied to any use. CHAP. XL BROMINE. Equivalent 75? 525. Bromine was discovered only a few years ago by M. Balard ; it is obtained by passing a stream of chlorine through bittern (the liquid that remains after boiling down sea-water to prepare common salt,) and exposing it afterwards to heat, when bromine is distilled and may be collected in a receiver. Another method is to shake sulphuric ether with the bittern after the chlorine has been passed through it; the ether dissolves bromine, and when it is left at rest it collects at the top, having a very rich hyacinthine colour. On digest- ing it with a strong solution of potash, two new salts are formed, the bromate and hydrobromate of potash ; the latter is obtained in cubical crystals by evaporation, and on mixing it with peroxide of manganese and sulphuric acid in a glass retort, the bromine is disengaged by the application of heat. Bittern consists principally of sulphates and muriates of soda and magnesia, with a small quantity of the hydrobromate of magnesia, a compound of hydrobromic acid and magnesia. 210 BROMINE. The hydrobromic acid is composed of hydrogen and bromine, and when the chlorine is transmitted through the bittern, it combines with the hydrogen and disengages the bromine, which imparts a yellow colour to the liquid. The vapour of the bromine has a deep reddish brown colour, bearing a great resemblance to nitrous acid vapour, and condenses into a very dark coloured liquid. 526. In the second process, the bromate and hydrobromate of potash are formed by one portion of the bromine combining with the oxygen and another with the hydrogen of a portion of water which is decomposed. When the hydrobromate is after- wards mixed with sulphuric acid and peroxide of manganese, sulphates of potash and manganese are formed, oxygen gas being disengaged and taking hydrogen from the hydrobromic acid which is eliminated at the same time, and the bromine which is set at liberty is collected in the receiver. I have found a few ounces of bittern sufficient to show the first process for the preparation of bromine, though little more than a grain or two is obtained, but for the second, a larger quantity must be employed. In preparing the liquid, the chlorine must be transmitted through the bittern till the orange yellow colour which it acquires ceases to become deeper. 527. Bromine is the only elementary substance that is liquid at natural temperatures, with the exception of mercury. Its present appellation is derived from its disagreeable smell, (/Sg&Yios, faetor.) In all its chemical relations it bears a great resemblance to chlorine and iodine, and its compounds are ana- logous to those which they form with the same bases ; they may be prepared in the same way. For a more particular ac- count of its properties, I must refer to the different scientific journals. PREPARATION OF FLUORIC ACID. 211 CHAP. XII. FLUORINE. 528. The existence of a peculiar elementary substance in the mineral commonly known by the name of Derbyshire spar is admitted by all chemists, though it has not been obtained in an insulated state. It has received the name of Fluorine, as it is the base of Fluoric Acid. Fluoric Acid. Colourless and transparent, emits copious dense white fumes on exposure to the air. Specific gravity, 1.06. 529. To prepare fluoric acid, fluor spar (Derbyshire spar) is reduced to a very fine powder, and put into a leaden re- tort into which its own weight of sulphuric acid has been pre- Fig. 56. viously poured ; the materials are mixed together with an iron rod, and on applying a mode- rate heat by a chauffer, fluoric acid is disengaged ; a receiver of the same metal must be used to condense it. Instead of a leaden retort of the usual shape, an apparatus similar to what is represented in the annexed figure will be found more con- venient. It is composed of a deep leaden cup, with a rim of lead sol- dered round the top, a small space being left between it and the upper part of the cup for fixing in the head of the appa- ratus when the materials have been put in ; the easiest me- thod of proceeding is to fill this intervening space with plaster 212 PREPARATION OF FLUORIC ACID. of Paris, and put in the cover when it begins to set, taking care to have the tube and the bottle receiver, which are used along with it, properly adjusted at the same time, that it may not be necessary to shift it afterwards. The receiver is placed in a jar or bason, and surrounded with ice or very cold water. The heat ought to be cautiously applied ; a very small chauf- fer is all that is required, and as beginners generally melt the bottom of the leaden cup by using too great a heat, they ought to examine it occasionally with an iron rod, and with- draw the chauffer for a little if they should find it beginning to turn soft, or yield much more readily than usual to the iron. The body of the retort in the apparatus which I generally use is rather more than two inches in diameter, and between seven and eight inches long ; it is supported by an iron ring- resting on three iron rods, and bound together at the bottom by a plate of sheet iron, on which the chauffer is placed. Two, three, or four ounces of fluor spar may be used in it at a time, or even more, if it is required. 530. Until the nature of the fluoric acid has been satisfac- torily ascertained, it will be impossible to give the true theory of the reaction that takes place in the process we have describ- ed. Fluor spar is regarded by many as a compound of dry fluoric acid and lime, and, according to this view, the dry sulphuric acid in the liquid acid employed combines with the lime, and the fluoric acid uniting with the water previously in combination with the sulphuric acid forms the liquid that is condensed in the receiver. The more common opinion, however, is, that fluor spar is composed of fluorine and calcium, (the metallic base of lime) and that the water of the sulphuric acid is decomposed, the oxygen combining with the calcium and forming lime which remains in combination with the sulphuric acid in the leaden cup, while the fluoric acid is formed by the fluorine combining with the hydrogen. 531. The greatest caution must be taken while experiment- ing with this substance, as its vapours are not only highly irritating, but it acts also more violently on animal substances than any of the other acids. A single drop falling on the FLUORIC ACID. 213 skin instantly destroys the part with which it comes in con- tact, producing a deep ulceration, which is not easily cured. 532. Fluoric acid has all the properties of a very powerful acid, and is particularly distinguished by its action on silica, com- bining with it, and forming a gaseous compound, which has been termed fluosilicic acid. Hence, it cannot either be pre- pared or preserved in glass vessels ; silver and platina vessels are preferred, but those made of lead, being much cheaper, are generally employed. 533. From this property it is used for etching on glass, and it may be employed in the gaseous state, or the strong acid diluted with four or five parts of water may be taken. The whole of the glass is coated in the first place with bees wax, which is not acted upon by this acid, and figures traced upon it with a sharp pointed instrument. When exposed to the vapour of the acid as it is disengaged from the retort, the glass is immediately corroded where the wax has been removed, the fluoric acid combining with the silica and forming fluosilicic acid. 534. On the small scale, the experiment may be performed by mixing one, two, or three hundred grains of fluor spar with its own weight of sulphuric acid in a small iron cup, holding it over the fire till its vapours begin to be disengaged, and then placing the glass over it, covering the whole with a wooden or paste-board box, to prevent the vapours from escaping. 535. When the diluted liquid acid is used, it is poured on the coated glass after figures have been traced on it, a small edging of wax haying been raised all round the glass to pre- vent it from running off. The vapour renders the glass rough and less transparent than before, but the transparency is not diminished with the liquid acid. By allowing it to re- main on for a longer or shorter period, the lines may be mp,de more or less deep. 214 1'LUOBORIC ACID. Sect. II. — Fluoboric Acip. 536. This is a compound of fluoric and boracic acid, which is obtained by exposing boracic acid and fluor spar in a tube to a red heat. It may be procured more easily by mixing inti- mately fused boracic acid with twice its weight of fluor spar, (having previously reduced them both to a fine powder) and twelve parts of sulphuric acid in a glass retort, heating the mixture by a chauffer. Half an ounce or an ounce of the fused boracic acid, with the corresponding proportions of fluor spar and acid, affords a considerable quantity of the compound. 537. It exists in the gaseous state, and is largely absorbed by water, which condenses 700 times its volume of this gas, and acquires a specific gravity of 1-77- So great is its affinity for water, that it abstracts it from all gases containing any, forming very dense white fumes when it is allowed to mix with atmospheric air. Sect. III. — Fluosilicic Gas. Specific gravity 3.611 grains. Weight of 100 cubic inches 110.13 grains. 538. This is the compound that has been so frequently alluded to in this chapter, and it will be better therefore to describe the method of obtaining it in this place, than post- poning it till we come to silica. It is composed of silica and fluoric acid, and is a permanent gas at natural temperatures and under the usual pressure. 539. It is prepared most easily by mixing intimately one part of pounded glass with an equal weight of fluor spar and two parts of sulphuric acid, the fluoric acid disengaged by the action of the sulphuric acid on the fluor spar combining with the silica of the glass, and forming the fluosilicic gas. 540. It must be collected in jars over mercury > as it is de- composed by water, and about a third part of the silica deposited, while the whole of the acid and the remaining two FLUOSILICIC GAS. 215 thirds of the silica are dissolved by this fluid, which can take up 365 times its volume of fluosilicic acid gas. 541. Fluosilicic acid gas is extremely pungent and irritating. It does not corrode dry glass vessels, cannot support combus- tion, and forms white fumes with air containing watery va- pour. Its composition is still involved in considerable obscu- rity, some regarding it as a compound of fluorine and silicum, the base of silica, while others are inclined to consider it as a compound of fluoric acid and silica. 216 CLASS II. METALS, AND THEIR COMBINATIONS WITH NON- METALLIC SUBSTANCES, AND WITH ONE ANOTHER. ORDER I.— ALKALIFIABLE METALS. CHAP. I. POTASSIUM. Equivalent 40 ; specific gravity 0.865. At 32, it is hard and brittle, becomes soft and malleable at 50, quite fluid at 150, resembling mercury, and is volatilized below a red heat. 542. Potassium was discovered by Sir H. Davy, who obtained it by exposing the hydrate of potassa to the action of galvanism between two discs of platina, oxygen appearing at the positive surface and minute metallic globules of potassium at the negative, arising from the decomposition of the potassa, which is composed of oxygen and potassium. A galvanic battery of 200 pairs of plates is quite sufficient to show these globules, but only a very minute portion of potassium is pro- cured in this manner. 543. Gay Lussac and Thenard prepared it by fusing the hydrate of potassa and allowing it to flow over iron turnings heated to whiteness in a gun-barrel, the oxygen of the potash rilEPAUATION OF POTASSIUM. 217 combining with the iron, and the potassium being at the same time volatilized and condensed in a receiver connected with the gun-barrel. 544. The process by which it is procured most easily is by distillation from a mixture of potassa or carbonate of potassa and charcoal, without the addition of any iron filings or turn- ings.* M. Brunner pointed out this process ; it has since been modified by Wohler, and the method of conducting it with the form of apparatus which I shall now describe is what I have been led to prefer from a number of trials, most of which were made along with my friend and former pupil Mr. Gloag. 545. An iron pot is made of the best malleable iron, of the Fig. 57. form represented in the annexed Figure, about 1 2 inches long and 5 or 6 in diameter ; the iron r= ^} — < should be at least |ths of an inch thick. The Otop is turned a little outwards, and a lid of the same metal and about the same thickness fitted accurately to it ; it is secured in its place by an iron rod which is passed through two holes in the upper part of the opposite sides of the pot, where they are made to project for the purpose. A hole at one side admits a wide bent gun-barrel intended to convey the potassium to a receiver. 546. The mixture of charcoal and potassa is prepared most easily by exposing six or seven pounds of cream of tartar (crude tartar may be used) to a red heat in large earthen or iron crucibles till no more gas is disengaged, reducing it to powder when cold in a mortar. The gases that are disengag- ed arise from the complete decomposition of the tartaric acid, its oxygen and hydrogen combining with part of its carbon and forming carbonic acid, carbonic oxide, and inflammable compounds of carbon and hydrogen ; part of the carbonic acid remains in combination with the potassa with which the rest of the carbon is mixed. It is reduced to powder when- * Quarterly Journal of Science, vols. xv. and xxii ; or Bib. Aniv. xxi. and Annales des Mines xii. 218 rilEPARATION OF POTASSIUM. ever it has become cold, and transferred immediately to the iron pot that it may be prevented from attracting water from the air. Brunner states that when the tartar is mixed with ^th of its weight of charcoal a larger quantity of potassium is obtained. 547. The iron pot should be luted before it is used, as it is apt to be melted, or at least speedily destroyed by the ac- tion of the air at the high temperature to which it must be exposed. The best method is to bind the iron vessel round on every side in the first place with iron wire, covering it after- wards to the depth of a quarter of an inch with a stiff lute made of Stourbridge clay (the common fire clay found in the vicinity of this place does very well) with about a fifteenth part of iron filings and charcoal, using no more water than is necessary to allow it to be easily worked, and mixing all the materials with a little thread (cut into small pieces not more than an inch long) before adding the water. This is bound round again with iron wire and the whole rubbed over with an additional quantity of lute. The lower part of the appa- ratus should be luted first; it is easily covered with wire by cutting a number of pieces a little longer than is necessary to allow them to go round both sides and the bottom of the iron pot, bending them in the form of the letter U, and put- ting a thick piece of the lute on the bottom of the iron pot, that they may be kept in their place till they have been fixed by the wire which is then wound round its sides. The mouth must be turned downwards all this time, and, when it has been inverted and the materials put in, the finger is drawn round the edge of the lid with a little common clay (to pre- vent it adhering to the body of the iron vessel when it is at a high temperature), and fixed in its place by the iron rod which is passed above it through the rings that project from the top of the iron pot, a small piece of scrap iron (such as the end of a broken chissel) being hammered in between it and the lid to drive it home. The bent gun-barrel (luted in the same man- ner as the iron pot where it is to be exposed to the fire), is then introduced, and the ends of the iron wire still projecting over the top of the pot are then turned in over the lid and PKEPA RATION OV POTASSIUM. 219 properly luted, taking care to protect the whole of the appa- ratus. If the furnace wont admit of the tube and the rest of the apparatus to be put in together, it will be necessary to place the iron vessel in the furnace after the tube has been put in, and to finish the luting there. I have never seen this lute fail when properly put on, though the apparatus may have been used immediately afterwards ; it is better, however, to allow it to dry a day or two previously before the fire, filling up any cracks that may be observed then with a fresh quan- tity of lute. 548. In Wohler's process, the iron bottle which he uses is placed horizontally ; but I prefer the upright position, as the tube is then not so apt to be filled up by the carbonaceous matter and other substances that are carried over during the distillation, and in no case have I found any obstruction to take place in the bent part of the tube when placed so as to be within the furnace. A plain bottle may perhaps in many cases be used with advantage, but as I found it often difficult to withdraw the materials that remain in the iron vessel after distillation, I have been induced to prefer the apparatus now described. 549. The iron retort is placed above a piece of fire brick resting on the branders of the furnace, and fixed to it with some fire clay. The body of the furnace I use for an ap- paratus of the size described is about 18 inches long, 15 broad, and 18 deep : the walls may be from 5 to 10 inches thick, and the flue rising from it 6 inches square (internal diameter), and carried up about fif- teen feet ; in convenient, situ- ations it may be connected with a common flue. The upper part of the furnace is covered by a flat cast iron plate about Fig. 58. 'ZZ7? □ «3m 1 I; -A g-^j%S=3i *r 220 PltErAHATION OF POTASSIUM. fths of an inch thick and with an opening in the centre through which fuel is introduced, a moveable cover of the same metal being fitted to it by an iron bolt passing through a hole bored in it and in the plate ; it allows us also to see very convenient- ly the state of the apparatus within the furnace. Another opening is made on a level with the branders to allow the fire to be withdrawn whenever it may be necessary, constructed in such a manner as to allow it to be easily closed up with a brick and a little mortar, and removed again with the same facility. A door is also placed below to regulate the admission of the air, and a damper in the vent to diminish the draught if this should be necessary. The aperture in the side of the furnace for the gun-barrel must not be forgotten. 550. After every thing has been properly adjusted, the fire may be put on. A little water comes away when the appara- tus becomes red hot ; soon after carbonic oxide gas is evolv- ed, and when it is at a white heat a very dense vapour is disengaged which burns with a brilliant flame. The receiver intended to condense the potassium may then be fixed to the extremity of the gun-barrel without the furnace by a little plaster of Paris ; and here I shall describe the receiver recom- mended by Berzelius which should be kept cold by ice. 551. It is about a foot high, six inches wide, one and a half thick, made of copper or sheet iron, and composed of two separate pieces which are represented in Figures 59 and 60. Fig. 59. The first is open at the bottom and close at the top, divided in the middle by a partition (tp ^|°i j \3) (a) with a small hole in it, and provided with three openings, — one for connecting it with the gun-barrel, another immediately opposite this for the introduction of an iron rod or the blade of a sword to clear the gun-barrel when • Flg * 60, it begins to be closed up by a black matter collecting in it, and another for carrying off the gas that is disengaged, by a glass tube (b) which allows us to judge how the process is go- ing on. The other is filled half full of naphtha, and made of such a size that the upper one shall fit accurately i A / i / / PREPARATION OF POTASSIUM. 221 to it, and not pass into it without some degree of friction. The receiver must be kept quite cold by ice or very cold water ; the most of the potassium is deposited before the gas that comes along with it escapes by the glass tube. 552. When the gas begins to be disengaged slowly, this arises in general from the tube being so obstructed as to pre- vent it from passing out readily ; the plug is then taken out and the obstructing matter removed as completely as possible, but if the gas does not appear then to increase in quantity, it will be better to withdraw the fire and allow the apparatus to cool. Too much caution cannot be taken in endeavouring to clear the tube either during the distillation or after the appar- atus has been allowed to cool, for the tube being frequently obstructed while the materials are at a high temperature and still producing gas, it is obvious that a large quantity must be accumulated in a short time, and the moment the impediment to its free passage is removed, it often expands with explosive violence, and gives rise occasionally to serious accidents. I recollect on one occasion where the apparatus was not touched till 36 hours after the fire had been withdrawn, on tapping the gun-barrel to remove it more easily, the whole of the glass tube was broken to pieces so excessively small that no trace of it was after to be found ; a peculiar detonating compound ap- peared to have been formed within the tube this time, small quantities of which were found in almost every part of the room, which exploded with very little friction. 553. The operator ought accordingly always to be protected in the most complete manner and never to be without a mask ; processes like this also should be excluded from class-rooms, where there is not an experienced assistant to give them that constant and undivided attention which they require. 554*. Occasionally too, when the tube becomes completely obstructed, I have seen the vapours of potassium forced through between the lid and the top of the iron vessels, burning with a rich violet coloured flame, easily distinguished by its beautiful colour from the flame produced by the combustion of the fuel. The fire must be withdrawn immediately whenever this ap- pears. 222 PREPARATION OF POTASSIUM. 555. I have tried subcarbonate of potassa mixed with char- coal after it had been fused to dry it as completely as possible, but I prefer the calcined cream of tartar, as the potassa is ob- tained in this manner more intimately mixed with the carbon of the decomposed tartaric acid. On every occasion where I employed a mixture of charcoal and iron turnings, a higher tem- perature appeared to be necessary to disengage the potassium, and a smaller product was obtained. 556. The potassium collects principally in the first division of the receiver, part of it is deposited in the second, and a small quantity is sometimes found in the jar of naphtha in which the extremity of the glass tube is placed. It is never perfectly pure, being always mixed with a small portion of carbon ; I have often found the purest part of the potassium lining the gun-barrel before it has entered the receiver, and am inclined to believe that considerable improvements may still be made in this part of the apparatus, but shall defer saying more of them till I have repeated the trials which I have already made. 557. It is usually recommended to purify potassium by distillation in a common glass retort, but on repeating the operation, it will be found that the temperature required for the volatilization of the potassium generally enables it to de- compose the glass, which is often completely destroyed, and a considerable proportion of the potassium lost. A green glass retort is less apt to be destroyed, or foreign white glass retorts may be used, some of which contain no lead, and can bear as high a temperature as the green glass retorts made in this country. It will perhaps be better always to distil from a small iron vessel or tube retort heated by a chauffer. 558. In condensing potassium in the receiver, naphtha is the liquid that must be employed, as potassium can decompose every fluid which contains even a minute quantity of oxygen, combining with it and forming potassa. The same fluid must also be employed to prevent the potassium from being oxidated by the air. 559- The leading character of potassium is the great affinity which it has for oxygen. Take a small piece of potassium POTASSIUM. 223 (about a grain) remove the naphtha adhering to it by blotting paper, and place it with a pair of pincers on a piece of red hot iron. It will immediately take fire, combining with the oxygen of the air and is converted into peroxide of potassium. 560. Put another piece into a brass or copper cup (Fig. 32, page 48) already at a high temperature, and introduce it the moment it is inflamed into a jar or bottle of oxygen gas, when it will burn more brilliantly than before. Throw a little water on the orange coloured matter that remains after either of these experiments, part of its oxygen is disengaged with effer- vescence, and potassa remains in solution ; on pouring a little of the infusion of red cabbage into the solution, it will imme- diately become green ; potassa turning the vegetable blues to a green. 561. Throw a few pieces of potassium into a bason full of water ; one portion of it immediately combines with the oxy- gen of part of the water which is decomposed forming potassa, while the other uniting with the hydrogen forms a very in- flammable gas, — potassureted hydrogen, which takes fire as it is disengaged and is converted into potassa and water. The potassium rolls along the surface of the water till the whole of it is oxidated, burning with a rich rose-coloured flame, and producing a very beautiful appearance. 562. Put another piece of potassium on a mass of ice ; the same action takes place and a similar light is produced. 563. Take a piece of potassium (about a grain) wrap it up in a small piece of paper and introduce it quickly into a glass test tube inverted under water and full of this fluid. It will immediately rise to the top, and the moment the water reaches it through the paper, part of it will be decomposed, the oxy- gen combining with it and forming potassa, while an equiva- lent portion of hydrogen gas is found in the tube, and may be inflamed by applying a lighted match in the usual way. 224) POTASSA. Sect. I. — Potassa or Potash. Equivalent, 48 ; (Oxygen 8 + 40 Potassium.) Very solu- ble in water and alcohol. The hydrate fuses before it is heated to redness. 564. Very pure potassa is obtained when potassium is ex- posed to the action of air or water, as in any of the preceding experiments ; the expense of this process, however, must al- ways preclude its being adopted for ordinary purposes. 565. The common process for obtaining potassa consists in preparing a solution of it in the first place from the sub-car- bonate, and evaporating it to dryness to expel the water in a silver or iron bason carefully protected from the air, urging the heat afterwards till the dry mass is fused and begins to flow like oil. The process recommended by the different col- leges for the preparation of Potassa Fusa is conducted in the same manner. For this purpose, pearl ashes (the sub-carbonate ^of potash that is met with in the shops) may be dissolved by rubbing them with four times their weight of water in an earthen mortar, and the solution decanted and mixed with a quantity of newly slaked lime equal in weight to the pearl ashes employed, boiling it for a few minutes and then filtering to separate the solution of potash that is procured in this man- ner from the carbonate of lime with which it is mixed. The throat of the funnel is obstructed by a glass stopper or a piece of quartz, covering it closely with a piece of linen to prevent any lime passing through with the clear solution. As potassa speedily attracts carbonic acid from the air and becomes car- bonated, the solution must be protected from it as much as possible during the operation ; the best method of effecting Fig. 61. this is by using a funnel with a narrow mouth which may be easily closed by a cork or stopper, and putting a small tube through the throat of the funnel, placing pieces of quartz or broken glass round it, and covering it with linen, so that while the solution of potassa is dropping into the bottle below, air passes through the tube at the same time from the lower to the upper vessel, PHEPAUATION OF POTASSA, 225 and supplies its place. This ingenious method was proposed by Dr. Duncan, (Dispensatory, 538) and is an excellent sub- stitute for a more complicated apparatus. When a common funnel is employed, it should be covered with a plate or tin tray, and a towel thrown over the whole. 566. The whole of the solution of potassa is not obtained in this manner, as a considerable portion of it adheres me- chanically to the lime ; to procure it, a small quantity of wa- ter is poured on the top of what remains in the funnel after it has ceased to drop ; that presses upon the liquid it still con- tains, and causes it to pass slowly into the receiver below. This is continued till a quantity of liquid is obtained equal to five or six times the weight of the salt employed. It must be kept in glass bottles with good stopples. 567- In this process, the lime having a greater affinity for carbonic acid than potassa, immediately combines with it, carbonate of lime being formed, which is insoluble and remains in the funnel, while the potassa passes through in solution. It is impossible in this manner to remove the carbonic acid com- pletely from all the potassa ; it is sufficiently pure, however, for most chemical purposes, when the precautions which have been mentioned are carefully attended to. 568. If the solution contains little carbonic acid, it will give a very slight precipitate with lime water, and scarcely present any appearance of effervescence with sulphuric acid. If it is free from lime also, (which is occasionally present,) it will not be rendered turbid on blowing through it with a bent tube. 569. It is from this solution that solid potassa is usually formed, evaporating it to dryness, and then fusing the mass that remains with a heat gradually increased till it flows like oil, when it may be poured into moulds or on a plate of iron, breaking it into pieces and putting it into a bottle, to prevent it attracting water or carbonic acid from the air. In this state it forms the fused potassa, or common caustic of the different colleges. Potassa with lime, or the milder caustic of the Edinburgh and Dublin Colleges, is made by mixing the solu- tion of potassa (prepared from the subcarbonate,) with slaked 226 PREPARATION OF POTASSA. lime in fine powder till it becomes of a thick consistence, after expelling about two-thirds of the water by evaporation. 570. When prepared in a silver vessel, it is usually of a white or greyish white colour, but when iron vessels are used, (which should always be bright and clean,) a portion of oxide of iron is always mixed with it, giving it a brownish colour, and separating from it when it is dissolved in water. Hence the origin of the brownish matter which is usually deposited in dis- solving this substance in water. 571. Though it is generally termed potassa, or caustic pot- ash, it is really a compound of dry potassa and water, one equivalent of the alkali retaining one equivalent of water in combination, which cannot be separated by exposing it even to a temperature far above a red heat. Hydrate of Potassa is therefore its strict chemical appellation. It has been found also that part of the potassa attracts an additional quantity of oxygen during its fusion, and is converted into peroxide of potassium, but this is not of any consequence, as the excess of oxygen is again disengaged when it is dissolved in water. 572. Perfectly pure and dry potassa has been prepared by exposing potassium spread out into thin layers to the action of the air, or by decomposing nitrate of potassa by heat, but it has not been applied to any use. The common hydrate is what is used for almost all chemical purposes. 573- As it is obvious the fused potash prepared from the solution obtained by decomposing the carbonate must always contain any carbonic acid that has not been withdrawn by the lime, the latter must be separated by digesting it in strong alcohol, when this substance is required perfectly pure, which dissolves the potassa, but leaves any carbonate that may be mixed with it ; the alcohol is afterwards separated by distilla- tion. 574. Throw some pieces of fused potassa into water ; it will dissolve speedily, and considerable heat is produced if the quantity of water is not great. The solution has a very acrid alkaline taste, even when largely diluted with water. 575. Pour a little of the solution into a glass of water tinged with the blue infusion of cabbage ; it immediately be- POTASSA. 227 comes of a fine green colour, which speedily passes to a yel- lowish brown, the caustic potash, especially when the solution is strong, completely destroying the vegetable colouring matter. 576. Pour some of the solution of potassa into two glasses of water, the one coloured by an infusion of turmeric, and the other by a solution of litmus. The turmeric immediately becomes brown and the litmus remains unaltered ; if, however, it should previously have acquired a reddish tint, it will be rendered blue. 577- Fill a number of glasses nearly full of water, and drop into them small quantities of the solutions of a number of salts, as the muriate of barytes, the muriate of lime, the sulphate of magnesia, the sulphate of iron, the sulphate of copper, and the acetate of lead ; then drop into each a small quantity of the solution of potassa. It combines with the acid in combination with these different salifiable bases, all of which are completely separated if a sufficient quantity of the alkali is employed, as potassa has a much greater affi- nity for the sulphuric, muriatic, acetic, and most other acids when in solution and at natural temperatures, and forms so- luble salts with them, while the bases which it separates are either insoluble or require a large quantity of water for their solution, and are thrown down in the form of precipitates. 578. The student should perform a number of similar ex- periments with the rest of the alkalies, &c. as he proceeds, till he becomes more familiar with the different substances with which they are incompatible, and their general chemical agency. Thus potassa is incompatible with acids, neutralizing them im- mediately, and forming salts of various kinds, according to the nature of the acid ; it is incompatible in general with so- luble salts of the earths and common metallic oxides, precipi- tating them from their solutions, and combining with the acids previously in combination with them ; it decomposes the chloride and bichloride of mercury, (calomel and corrosive sublimate,) producing compounds which will be described un- der mercury, &c. ; he need not attend, however, to the minu- tiae of its action on different bodies, till he come to study the different substances themselves. 228 POTASS A. 579. Potassa is used in medicine as a caustic, and is occa- sionally administered internally in calculous diseases. For chemical purposes it is extensively employed in the arts, and is an important analytical re-agent. It is the basis of common soft soap, forms glass with silica, and its solution in water can dissolve a number of metallic oxides. 580. The tests by which potassa is most easily distinguish- ed from soda, the substance that it is most likely to be mis- taken for, are the chloride of platina, and tartaric acid. The former gives a yellow coloured precipitate with salts of potash when they are sufficiently concentrated, but does not affect those of soda ; the action of tartaric acid has been already ex- plained, (408.) 581. The potash or potashes of commerce is obtained by digesting the ashes of burned wood in water to extract the so- luble matters which they contain, and boiling down the liquid afterwards to expel the water. It consists principally of the hydrate of potassa with carbonate of potassa, and small quan- tities of the sulphate and muriate of potassa, sulphuret of po- tassium, and earthy substances. When it is exposed to heat in a reverberatory furnace, stirring it constantly at the same time, it is more completely carbonated, and forms what is termed Pearl Ash, from its acquiring a white colour. A small quan- tity of alkaline matter, sufficient at least to indicate its pre- sence, may be obtained in solution by pouring water on the ashes of a wood fire and filtering the liquid, which will then turn the infusion of red cabbage to a green. Sect. II. — Salts of Potassa ; Sulphuret, Chloride, and Iodide of Potassium. 582. In describing the salts of the different alkalis, earths, &c. I shall at the same time consider the sulphurets, chlo- rides and iodides of their respective bases, and other analogous compounds when they are of sufficient interest. 583. Nitrate of Potassa or Nitre, crystallizes in six sided prisms, and is soluble in seven parts of water at CO, and in its own weight of boiling water. NITRATE OF POTASSA. 229 584. Add nitric acid to a solution of potassa or sub-carbonate of potassa till it is completely neutralized, and evaporate the so- lution till it shall not exceed three or four times the bulk of the nitric acid employed ; crystals of the nitrate will be formed as it cools. Nitre is never prepared in this manner, however, for commercial purposes, as it is an abundant product of nature, appearing in the form of an efflorescence on the sur- face of the earth, particularly in the East Indies. It is also formed in large quantities in artificial nitre beds by mixing lime and carbonate of lime with animal and vegetable substances and exposing them to the air, the nitrogen of the nitric acid which is formed being derived from the animal matter and the air, and the oxygen from the same sources ; the lime unites with the acid as it is produced and forms nitrate of lime, a salt which is easily dissolved by water, and on adding sub- carbonate of potassa, a double decomposition immediately takes place, nitrate of potassa remaining in solution while car- bonate of lime is precipitated. 585. Nitre parts easily with oxygen when heated, especial- ly if mixed with metals and the simple inflammables. In the arts it is used principally for the preparation of nitric acid and gunpowder, and a number of fulminating and deflagrating compounds. It is easily melted by exposure to heat, and when thrown into moulds in this state, so as to have the form of flat cakes or round balls, it forms what is usually sold under the name of Sal-Prunelle. In practical chemistry, nitre is used principally for oxidating a number of substances, and occa- sionally for producing cold by dissolving it in water ; the tem- perature falls about 15 degrees. A few experiments may be made with it to show its general properties. 586. Mix intimately 300 grains of nitre, 60 of sulphur and 40 of charcoal, previously reducing them to a fine pow- der. These are the proportions of nitre, sulphur and char- coal in some of the best kinds of shooting powder, and though the mixture cannot be made to have the same appearance with- out appropriate machinery, it will be found to deflagrate in the same manner on applying a light. 230 SULPHATE OF POTA3SA. 587- The port-fire used for firing artillery is made of three parts of nitre, two of sulphur, and one of gunpowder, well mixed and rammed in cases ; a small quantity of materials will he sufficient to show the appearance which it presents on burn- ing. 588. Signal lights are generally composed of nitre and sul- phur with a small quantity of some metallic sulphuret, as that of arsenic or antimony. Mix^600 grains of nitre^with 200 of sulphur and 100 of the yellow sulphuret of arsenic ; put the mixture into a cone of paper, and touch it (out of doors or under a large chimney) with a red hot iron ; it deflagrates ra- pidly with a brilliant white light. 589- Mix 100 or 200 grains of the sulphuret of antimony with the same proportions of nitre and sulphur, and inflame it in the same manner. It deflagrates immediately with a vivid light which has a bluish tinge. 590. Sulphate of Potassa crystallizes in six-sided prisms terminated by six-sided pyramids, does not contain any water of crystallization, and is soluble in sixteen parts of cold and five of boiling water. This salt is easily obtained from the residuum of the distilla- tion of nitric acid (135,136,) dissolving it in water and adding sub-carbonate of potash till the excess of acid is completely neu- tralized. The solution is then evaporated to expel part of the water, and small crystals of the sulphate are deposited on cooling. Carbonate of lime is occasionally employed instead of carbonate of potash to remove the excess of acid, conti- nuing to add it to the solution of the super-sulphate as long as any effervescence takes place. The following dia- gram shows the action that takes place, supposing all the po- tash to be in the state of bi-sulphate. Before decomposition. After decomposition. ( Potash 48 -jr--- 88 Sulphate of potash. 128 Bisulphate J o i i • • j Ar , --"" of potash i bulphuricacid 40 -- (. Sulphuric acid 40 s. 50 Carbonate J Carbonic acid 32 --^-~-. ^ Q of lime \ L ime 28 ^ G8 Sulphate of lime. SULPHATE OF POTASSA. 231 Most of the sulphate of lime remains undissolved, the car- bonic acid is expelled with effervescence, and the neutral sul- phate of potash is obtained in solution. On the small scale, it will be much better to employ subcarbonate of potash, as it saves the trouble of filtering the solution to separate it from the sulphate of lime, and no sulphate of lime is present to in- terfere with the crystallization. The Sulphas Potassce cum Sulphure of the Edinburgh College is prepared by throwing equal weights of nitre and sulphur into a red hot crucible ; the sulphur reacts on the oxy- gen of the nitre, and forms a compound the precise composition of which is still undetermined, but it is very different from a mere mixture of sulphate of potash and sulphur, of which its name would lead us to suppose it is composed of. 591- Sulphuret of Potassium may be obtained by put- ting a small quantity of potassium into a glass tube, cover- ing it with a little sulphur, and exposing it to heat ; the sulphur and potassium combine, and heat and light are evolv- ed during the combination. Sulphuret of potassium is usually prepared by decomposing the sulphate of potash with char- coal ; the sulphate is reduced to a very line powder, mixed with about a fourth part of this substance in fine -powder, and the mixture exposed to a strong heat in a furnace ; carbonic oxide and carbonic acid gases are disengaged, the oxygen both of the sulphuric acid and of the potassa combining with the carbon, while the sulphur of the acid and the potassium of the potassa remain in combination. Two or three hundred grains of the sulphate with the proper quantity of charcoal will be sufficient to show the nature of the process. The annexed diagram represents the theory of the decom- position, supposing no carbonic acid to be formed, which is probably the case when a sufficient quantity of carbon is em- ployed : 232 SULPHURET OF POTASSIUM. Before decomposition. Carbon 24 Carbon 40 Sulphuric acid 48 Potassa Carbon Carbon Carbon Oxygen Oxygen Oxygen Sulphur 16 ( Oxygen 8 / ( Potassium 40 6- 6- 6- 6-- 8'' 8/ 8/ 112 112 After decomposition. 7 1 4 Carbonic oxide. -7 14 Carbonic oxide. - 7 14 Carbonic oxide. 1.14 Carbonic oxide. .56 Sulphuret of potassium. 112 Sulphuret of potassium may be prepared also by heating the subcarbonate of potassa with sulphur in a large crucible ; the heat ought to be applied cautiously, and continued till the mixture is completely fused. It is in this manner that the different colleges prepare what they term sulphuret of potash, but it is in reality a mixture of sulphuret of potassium and other compounds produced by the action of the sulphur on the po- tassa and its oxygen. From its colour resembling that of the liver, it is often called Hepar sulphuris. 592. Digest the sulphuret obtained in the manner first de- scribed in water. A reaction immediately takes place between it and a portion of the water, and a solution of the hydrosul- phuret of potassa is obtained, the potassium taking the oxygen and the sulphur the hydrogen in the manner represented in the diagram. 9 Water 56 Sulphuret of potassium 65 Before decomposition. f Hydrog.l "" \ Oxygen 8 f Sulph. 16/ \ Potass. 40. 65 After decomposition. IT Sulphureted hydrogen. 48 Potassa. 65 Hydrosulphuret of potassa. 593. Boil 64 grains of sulphur with 118 grains of the hy- drate of potassa in an ounce of water. The whole of the sul- phur and potassa is dissolved, and a solution is obtained of a CARBONATE OF POTASSA. 233 dark greenish colour. It contains the sulphureted hydrosul- phuret of potassa, and a portion of the sulphate, sulphite, or hyposulphate of potassa, both these being formed by part of the sulphur combining with the hydrogen, and another part with the oxygen of a portion of water which is decomposed, and the acids produced in this manner remaining in combina- tion with the potassa. The annexed diagram gives a view of the reaction, supposing hyposulphurous acid to be produced by the combination of the sulphur with the oxygen of the water decomposed. Before decomposition. After decomposition. f Oxy. 8 \ 9Water JHyd.lO\ Sulphur 32 — ~^-->-> Hyposulphite of potash. Sulphur 32 > ■ — J> .Sulphureted hydrosulphuret of potash. Potassa 48 S s^ Potassa 48^ An additional quantity of sulphur may be dissolved with the same quantities of water and alkali ; the solutions have a deep amber colour when they have become clear, attract oxy- gen from the air, and are decomposed by the acids with disen- gagement of sulphureted hydrogen, and a copious precipitation of sulphur. 594. CarbonxVte of Potassa is very deliquescent, and soluble in less than its weight of water. It is usually termed Subcarbonate of Potassa, as it possesses decided alkaline pro- perties, the acid which it contains not being able to neutralize the alkali ; I have hitherto adopted the term that is generally made use of in speaking of it, that it might not be mistaken for the bicarbonate, which is called carbonate of potassa by those who term the present compound subcarbonate, but as the nomenclature of the different compounds is regulated by their atomic constitution, I must here use the terms of carbo- nate and bicarbonate. 595. The Pearl Ash of commerce is an impure carbonate of potassa, containing siliceous matter and a little sulphate of potassa, with a small quantity of other salts. A solution suf- ficiently pure for ordinary experiments may be obtained by 234 CARBONATE OF POTASSA. stirring it with water, the greater part of the other salts being left undissolved, as they are less soluble in cold water. A pure carbonate is obtained most easily by decomposing the bitartrate of potash (crude tartar may be used) by heat. It is occasionally mixed with nitre before it is decomposed, and the appearance and nature of the product varies according to the quantity employed, and the manner in which the operation is conducted. 596. When equal weights of nitre and cream of tartar are mixed together and thrown into a red hot crucible, a rapid deflagration ensues, and a white matter remains, which is usually termed White Flux. It is a pure carbonate, the nitric and tartaric acids of the two salts being* completely de- composed, and part of the carbonic acid produced remaining in combination with the potash. 597- If two parts of the bitartrate are mixed with one of nitre, and the mixture thrown in quickly, and in successive portions, into a red hot crucible, which is covered by a lid whenever the materials have been introduced, a small aperture being left for the disengagement of gas, then a black mass re- mains in the crucible composed of carbonate of potassa and charcoal, the oxygen in the nitric acid of the nitre not being sufficient to carry off all the excess of carbon which the tarta- ric acid contains. It is usually termed Black Flux. 598. The white flux is used in several chemical operations to impart fluidity to different substances with which it is mix- ed at a high temperature ; the black flux may be employed for similar purposes, but it is used chiefly as a deoxidating agent, as in the reduction of arsenious acid. When a pure solution of carbonate of potassa is required as a test, it should always be prepared from cream of tartar, and if nitre is pre- viously mixed with it, it should be free from muriatic salts and other impurities. In preparing both these substances, a cru- cible capable of containing twice the quantity of materials used should be employed. 599- This salt must always be kept in close vessels, to pre- vent it becoming liquid by attracting water from the air. Its solution renders the infusion of red cabbage green, and being much less caustic than pure potassa, the green colour remains BICARBONATE OF POT ASS A. 235 for a considerable time. It is usually obtained in the form of an amorphous mass, and may be fused by exposure to a good red heat. 600. To prepare the Bicarbonate of Potassa, a stream of carbonic acid must be transmitted through a solution of the carbonate in Woulfe's or Nootlfs apparatus. The solution must be evaporated by a very gentle heat, as its excess of acid is expelled by a boiling temperature, and it crystallizes slowly in prisms. It is not altered by exposure to the air, and is used principally for effervescing draughts. Every ^5 grains of crys- tallized tartaric acid, and 76 grains of crystallized citric acid can decompose 101 of the crystallized bicarbonate, combining with the potassa, and forming tartrate or citrate of potassa, which remains in solution, while the carbonic acid is disen- gaged with effervescence. Thirty or forty grains of tartaric acid, and a corresponding quantity of the bicarbonate, dissolv- ed in separate glasses of water along with a few pieces of sugar, form an agreeable and refreshing draught when mixed to- gether. 601 . When the bicarbonate is exposed to a red heat it parts with all its water of crystallization, and half its carbonic acid. If the subcarbonate is required quite pure and perfectly dry, it is prepared most easily from the bicarbonate by fusing it in a platina crucible. 602. Ferrocyanate of Potassa. — The composition of ferrocyanic acid has been explained, and also the method of preparing this salt in 384, 385. It is soluble in three parts of water at 60, and in its own weight of boiling water. The so- lution affords large crystals of a beautiful yellow colour ; it is not affected by the air, becomes black when exposed to a red heat, and is completely decomposed if kept at this temperature for some time. Its most important chemical relations have already been considered under cyanogen. Its solution gives no precipitate with alkalis or alkaline salts, but it decomposes some of the soluble earthy salts and most of the salts of the common metals when in solution, and is much employed as a reagent for detecting them. 603. Acetate of Potassa is prepared by adding the 236 POTASSA. purified acetic acid procured from the distillation of wood to subcarbonate of potassa in solution till it is neutralized, eva- porating the solution with great care afterwards, till the water is expelled ; the fused salt becomes a solid crystalline mass on cooling. By a high temperature it is completely decomposed. It is very soluble in water and deliquescent, and must be kept in close vessels. 604. Tartrate of Potassa is very soluble in water, and is easily prepared from the bitartrate by decomposing it with chalk in the manner described for the preparation of tartaric acid. Its solution affords crystals on evaporation. 605. The Bitartrate of Potassa may be prepared by adding tartaric acid to a solution of the tartrate, but it is ge- nerally prepared from the crude tartar that is deposited in wine casks, which consists of crystals of the bitartrate and co- louring matter. It requires about seventy parts of cold and fifteen of boiling water for its solution. Its most important uses have been already described. 606. Chlorate of Potassa is soluble in about eighteen parts of cold and five of boiling water. It contains no wa- ter of crystallization ; the theory of its formation and the method of preparing it have been minutely described under chloric acid. It is particularly distinguished by the facility with which it gives oxygen to inflammable substances, and when exposed to heat, a large quantity of oxygen is disengag- ed, and chloride of potassium remains, (30.) 607. Mix a grain or two of the chlorate with a little sul- phur in a mortar, and triturate them together ; loud explosions take place, and the sulphur combines with the oxygen of the chloric acid. 608. Mix half a grain of dry phosphorus with a grain of chlorate of potassa, put the mixture into a small piece of paper, and strike it with a hammer after folding it into a small packet and laying it in on a stone or a block of iron ; a larger quantity of materials should not be used, at least by the be- ginner, as part of the phosphorus is then apt to be thrown out in sparks. The detonation is violent, and the same reaction l'OTASSA. 237 takes place as in the former case, the phosphorus combining with the oxygen of the acid. 609- Introduce a little potassium into a jar of chlorine, us- ing the copper cup represented by Fig. 32, (page 48) ; it takes fire immediately, combining with the chlorine, and form- ing Chloride of Potassium. The same compound is ob- tained when muriatic acid is added to a solution of the car- bonate of potassa, and the solution obtained in this manner evaporated and crystallized ; the carbonic acid of the carbo- nate is disengaged in the first place with effervescence, and the hydrogen of the acid unites with the oxygen of the ox- ide forming water, while chloride of potassium remains. It is soluble in three parts of cold water, and has a bitter saline taste ; it has seldom been applied to any use. 610. Iodide of Potassium may be formed by heating io- dine and potassium in a small tube, heat and light being disen- gaged during their combination. 611. The best method of preparing this important com- pound, usually termed the Hydriodate of Potassa, though it is affirmed that such a combination can exist only in solution in water, is by the action of iron and iodine on water, and de- composing the clear liquid obtained in this manner by carbo- nate of potassa, evaporating the solution that remains, after separating the precipitate that is thrown down by filtration through paper. To see the nature of the process, 124 grains of iodine and 50 or 60 of iron may be mixed in a Florence flask, with two or three ounces of water, and heat applied by a lamp till the liquid becomes clear. 612. Every equivalent of iron and iodine decompose one equivalent of water and forms hydriodate of the oxide of iron, a reaction taking place in the manner shown in the annexed diagram. Before decomposition. After decomposition. 9 Water { H y dro g en 1 /^ 125 Hydriodic Acid. \ Oxygen 8 *< f S' Iodine 124 ''' "\ Iron 28 — ^ 36 Oxide of Iron. 161 161 Hydriodate of Iron. 238 sodium. An excess of iron does no harm, presenting a large surface and causing the action to proceed more rapidly, and is easily- removed by nitration. The hydriodate of iron being soluble is dissolved by the water, and on adding a solution of the car- bonate of potassa to it, taking care to use no more than is ex- actly necessary to decompose it completely, (the quantity re- quired is easily found out by adding small portions at a time as long as any precipitate takes place), carbonate of iron is pre- cipitated, and hydriodate of potassa remains in solution. When it is evaporated, the hydrogen of the hydriodate unites with the oxygen of the potassa, forming water, and iodide of potas- sium remains. 613. Hydriodate of potassa may also be prepared in the manner described in 507, separating it from the iodate that is formed at the same time by alcohol ; or it may be pro- cured by the action of sulphureted hydrogen on a solution of potash, a process which I suggested, and which was also pro- posed by Dr. Turner, but the method already described is the best. Iodide of potassium is obtained also when the iodate of potassa is decomposed by heat, both the iodic acid and the po- tassa parting with their oxygen in the same manner as the chlorate of potassa. 614. It deliquesces in a humid atmosphere, and is soluble both in water and alcohol. CHAP. II. SODIUM. Equivalent 2L Specific gravity 0.972. It is soft and ?nal- leable at 32, completely fused by a temperature of 200, presenting the appearance of silver or mercury, and re- quires a good red heat to convert it into vapour. 615. Sodium may be prepared in the same manner as po- tassium, or by mixing chloride of sodium with potassium, and SODA. 239 distilling from an iron retort, when the potassium combines with the chlorine, and the sodium is volatilized. 616. Sodium bears a great resemblance to potassium in all its chemical relations, and the experiments directed to be made with potassium may be repeated with it, proceeding in the man- ner we have already described. It does not take fire, however, like potassium when thrown on water, but in other respects the action is precisely the same in both cases. Sect. I. — Soda. Equivalent 32, (Oxygen 8 + 24 Sodium.) 617- Soda may be obtained from the sub-carbonate of soda by following the process described for the preparation of potassa from its carbonate. By evaporating its solution in water and fusing the dry mass that remains, a hydrate of soda is obtained, similar to the hydrate of potassa in its general chemical re- lations. 618. Most of the experiments described under potassa may also be repeated with soda, but its solutions give no precipitate with tartaric acid or chloride of platina, (580.) Sect. II. — Salts of Soda, Chloride of Soda, and Sul- PHUKET AND CHLORIDE OF SODIUM. 61 9- The salts of soda have the same general properties as those of potassa, but are for the most part more soluble in wa- ter, and all of them may be decomposed by this alkali. To see the greater affinity which potassa has for the acids, pour a strong solution of this alkali into a saturated solution of the sul- phate of soda ; crystals of sulphate of potassa are soon formed and soda remains in solution. 620. The Sulphate of Soda (Glauber's Salt) is prepared from the residuum of the preparation of muriatic acid in the 240 soda. same manner as the sulphate of potassa is procured from the residuum of the distillation of nitric acid. See 590. It cry- stallizes in prisms which are soluble in three parts of water, fuse on exposure to heat and part with their water of crystallization ; they effloresce when exposed to the air. 621. Experiments may be made with sulphate of soda and charcoal, with sulphuret of sodium and water, and with fused soda, sulphur and water, analogous to those described in the paragraphs after sulphate of potassa. 622. The Carbonate of Soda of commerce is obtained by digesting Kelp or Barilla, the ashes of incinerated sea plants in water, and crystallizing the solution ; or by soaking saw dust or other carbonaceous matter in a strong solution of the hydrosulphuret of soda and exposing the mixture to heat in a reverberatory furnace. The water is soon dissipated, the sulphureted hydrogen decomposed and expelled, and the soda combines with carbonic acid formed by the combustion of the fuel or of the materials with which the solution is mixed. The solution of the hydrosulphuret used for this purpose is prepar- ed from the sulphuret of sodium procured by decomposing sulphate of soda with charcoal, in the same manner as the sul- phuret of potassium is obtained from its sulphate, (592.) 623. Carbonate of soda is easily obtained in large crystals, from its solution in water. They are soluble in two parts of cold water, and in less than their own weight of boiling wa- ter ; on exposure to the air they effloresce, and fuse when heated, losing their water of crystallization, the quantity of which has been found to vary according to the temperature at which the crystals are formed. Its solution turns the ve- getable colours to a green. 624. The Bicarbonate of Soda may be obtained in the same manner as the bicarbonate of potassa, and has similar properties. 625. Phosphate of Soda is prepared by adding carbo- nate of soda to a solution of the superphosphate of lime (21 7) The excess of phosphoric acid in the superphosphate combines with the soda of the carbonate and remains in solution, disen- gaging carbonic acid with effervescence, while the phosphate of CHLORIDE OF SODIUM. 24<1 lime having now lost its excess of acid becomes insoluble and is precipitated. In the following diagram representing the ac- tion that takes place, two equivalents of acid are supposed to be combined with one of lime in the superphosphate. Before decomposition. After decomposition. f Carb. Acid 22 22 Carbonic Acid. Carbonate of Soda -j y Q( j a 32 --=- 60 Phosphate of Soda. fPhosph. Acid 28-"'"" B Lime Phate ° f 1 Ph o s P h - Acid 28 -<_ « Lime 28 — — ^^»- 56 Phosphate of Lime. The superphosphate of lime, however, is generally prepared with a much greater excess of acid, and every additional equi- valent which it contains enables it to decompose another equi- valent of the carbonate of soda. The latter ought to be add- ed till the solution can render the test paper green, as a slight excess of alkali favours the crystallization. The solution is filtered to separate the phosphate of lime, and evaporated af- terwards till a pellicle appears on its surface, when it may be set aside to crystallize. 626. Phosphate of soda is soluble in four parts of cold, and two of boiling water. It has a saline taste unaccompanied by the disagreeable bitterness of sulphates of magnesia and soda. By exposure to a moderate heat it loses most of its water of crystallization, and its properties are considerably al- tered. 627- Chloride of Sodium, usually called Muriate of So- da, or common salt, exists abundantly in the mineral kingdom, forming immense beds or strata, which are several hundred miles long in some places, and when obtained from these sources, it is termed rock salt. It may be prepared also in large quantity from sea-water, of which it constitutes the prin- cipal saline ingredient. In warm climates, the water is al- lowed to evaporate spontaneously in reservoirs made for the purpose, and is known by the name of bay salt in commerce ; in more northern regions, the water is partly dissipated in large pans or boilers, and occasionally a large portion of it is previous- R 242 CHLORIDE OF SODIUM. ly separated when the temperature is very low, part of the water freezing and leaving a stronger brine still liquid. 628. The salt procured by the spontaneous evaporation of sea water is in larger crystals, and much purer than what is prepared by rapid evaporation. The latter always contains a considerable quantity of magnesian salts, one of which, the muriate of magnesia, renders it deliquescent and impairs its antiseptic properties. 629- The presence of magnesia may be easily detected by adding a solution of the carbonate of soda to a solution of a few grains of common salt in water, a white precipitate ap- pearing immediately if magnesia is present, (See Magnesia,) while the liquid remains transparent and colourless if there is none. 630. When sodium is heated in chlorine, or muriatic acid gas, the same compound is formed, hydrogen gas being dis- engaged when the latter is taken. 631. Chloride of sodium crystallizes in cubes which con- tain no water of crystallization chemically combined with them, but a small portion between the layers of the crystals, which is separated with decrepitation on exposure to heat ; when a handful of bay salt is thrown in the fire, it decrepi- tates with loud reports, and the larger crystals are thrown about with great violence. 632. Chlorine and soda combine and form a compound which is much employed in solution as a disinfecting agent ; Labarraque's disinfecting liquid owes its properties to this sub- stance. Mr. Phillips and Mr. Faraday have examined it, and the latter has given the following formula for its preparation ; 2800 grains of crystallized subcarbonate of soda are dissolved in 1.28 pints of water, and chlorine transmitted through the solution in Woulfe^ apparatus, preparing it from 967 grains of common salt, 7^0 of the peroxide of manganese, and 960 of sulphuric acid, diluted previously with an equal quantity of water ; the chlorine should be transmitted through a bottle of pure water first, to remove any muriatic acid that may be mixed with it. No carbonic acid is disengaged, and though TARTRATE OF POTA8SA AND SODA. 243 the solution contains chloride of soda, its precise composition has not been accurately ascertained. By long keeping it is in a great measure decomposed, chlorate and muriate of soda being formed by the reaction of the chlorine on part of the water, in the same manner as has been explained in 457. 633. Tartrate of Potassa and Soda is prepared by add- ing the bitartrate of potassa, (cream of tartar,) in fine powder, to a solution of the subcarbonate of soda in boiling water as long as any effervescence takes place. Three hundred grains of the subcarbonate dissolved in ten or twelve parts of water will be sufficient to show the process, and for this about 400 grains of cream of tartar are required. The excess of acid which it contains unites with the soda of the carbonate, the carbo- nic acid being disengaged with effervescence, and the tartrate of soda remains in combination with the tartrate of potash, the solution crystallizing when it is evaporated to a pellicle and set aside to cool. The following diagram gives a view of the reaction. Before decomposition. After decomposition. Carbonate of f Carbonic Acid.. .22 22 Carbonic Acid. Soda ... \ Soda 32 -------,---- 98 * ( Tartaric Acid. . .66 " Tartrate of Potassa PoSsa 1 Tartaric Acid. ..66 <^- f and Soda. (.Potassa 48 — =: ^114 The solution gives large prismatic crystals, which are so- luble in five parts of water. 634. The Biborate of Soda, or Borax, is a native pro- duction, existing in the water of some lakes in Thibet and Persia. The crude Borax met with in commerce, and known by the name of Tincal, is refined by solution and crystalliza- tion. It is often termed subborate of soda, as its solution turns the vegetable blues to a green, two equivalents of bo- racic acid not being sufficient to neutralize one equivalent of soda. 635. This salt crystallizes in prisms, which are soluble in six parts of boiling and twenty of cold water. When ex- LITHIUM. posed to heat, its water of crystallization is expelled, and a transparent glass obtained; it is employed principally as a flux. CHAP. III. LITHIUM. 636. Lithium is the metallic base of lithia, an alkali that was discovered by Arfwedson in 1818. Its chemical equiva- lent is 10, and the equivalent of lithia is 18, consisting of one equivalent of lithium and one of oxygen. 637- Lithia has been procured only in very small quanti- ties, and has not been applied to any use. It is distinguish- ed from potassa and soda by forming compounds with phos- phoric and carbonic acids which are only sparingly soluble in water. CHAP IV, AMMONIA.* Equivalent by weight 17, hydrogen 3-+-14 nitrogen ; by vo- lume, |"T~1 (two measures.) Specific gravity nearly 59, weight of 100 cubic inches 18 grains. It is gaseous at na- tural temperatures, but becomes liquid when exposed to a pressure of six and a half atmospheres. 638. Ammoniacal gas is prepared most easily from common liquid ammonia, (a compound of ammonia and water) in the same manner as has been directed for the preparation of mu- * This substance is placed along with the metals, though it contains no metallic matter in its composition, as it bears a great resemblance to the ox- ides of the alkaline metals in all its leading chemical relations, and as the student will find it more convenient to examine its properties along with those of the other alkalies. PREPARATION OF AMMONIA. 245 l'iatic acid gas, collecting it over the mercurial trough, as it is absorbed in large quantity by water. 639- The water of ammonia (common liquid ammonia,) usually termed spirit of hartshorn, or volatile alkali, is prepar- ed on the large scale by the decomposition of animal matter exposed to heat in close vessels, condensing the product in water ; but it is obtained most conveniently by decomposing muriate of ammonia by slaked lime, receiving the product in- to water kept cold in a bottle receiver. For this purpose, equal weights of quicklime and muriate of ammonia are taken and mixed together, after the former has been slaked with a proper quantity of water, and allowed to cool ; they should both be in fine powder, and intimately blended, taking care to avoid the pungent fumes that are disengaged. The mixture is then put into an iron retort, (or an iron bottle with a bent tube fitted to it, will do equally well,) and placed in a sand- bath. The beak of the retort is then luted to a quilled globe, Fig. 62. of tne f° rm represented in the annexed fig- s — x ure, making the joining tight with a little ( v^r^^'^ plaster of Paris, and a quantity of water put %> 7 724. Fuse three parts of Lynn sand (purified previously by washing it with water and exposing it to a red heat) with one part of purified subcarbonate of potassa in a crucible, placing it in a furnace so that it may be exposed to a very strong heat. A transparent brittle glass is obtained, quite insoluble in wa- ter, and having usually a greenish tinge, derived from a mi- nute portion of iron in the materials or in the crucible. The sand and the carbonate should be well mixed together, and the crucible should not be filled more than a third full, placing it on a piece of brick so as to rest an inch and a half above the branders of the furnace ; a cover should also be placed loosely over it. The glass is formed by the silica of the sand uniting with the potassa, the carbonic acid being disengaged. About 800 or 1600 grains of materials give a very good specimen of glass. 725. Fuse another portion of the same materials with one or two grains of the peroxide of manganese. The glass will be found to have acquired a light tinge of purple, and to be free from the green or greenish yellow tinge which the iron communicates. 726. In another crucible, fuse 3 parts of the subcarbonate of potassa with 6 of the red oxide of lead and 10 of sand. The mixture will melt at a much lower temperature than the for- mer, and the glass formed is of the same nature as the flint glass prepared at the different glass works. The same mate- rials, with the addition of a small quantity of manganese gives a rich purple coloured glass, and with the oxide of cobalt it may be obtained of a fine blue colour. 727- Fuse one part of sand with three of the subcarbonate of potassa, and pour the liquid on an iron plate after all effer- vescence has ceased. The compound procured in this manner has the same appearance as glass, but it deliquesces speedily on exposure to the air, and is very soluble in water ; it is usually called silicated potassa. In this case all the carbonic acid of the alkali is not expelled, and its solution effervesces on the addition of acids. It must be kept in close vessels. 728. Add some sulphuric or muriatic acid to a solution of silicated potassa ; the acid unites with the alkali, and the si- 268 SILICA GLASS. lica is precipitated in combination with a part of the water ; the silica is often redissolved immediately, especially when the solution is very diluted ; if, however, it is evaporated to dry- ness, the silica becomes insoluble, and by digesting the mass in water, the salt mixed with it may be removed. 729. Add a solution of the muriate of ammonia to a solu- tion of the silicated potassa ; the muriatic acid combines with the potassa, and the whole of the silica is precipitated, and is not in this case liable to be redissolved. (Faraday.) 730. Crown or window glass is made usually of kelp and Lynn sand. Bottle glass is made of very impure materials, as the refuse of the salt employed by soap-makers and common sand. 731. Though flint glass is quite insoluble in water in the state in which if is usually obtained, it may be dissolved in small quantity if reduced to a very fine powder, and commu- nicates a green colour to the blue infusion of cabbage. In specimens of glass reduced to an impalpable powder at the glass works here for analysis, test paper was rendered green immediately on rubbing it with a little of the glass and water. 732. Glucinum, Ittrium, Zirconium, and Thorinum, are the metallic bases of the earths Glucina, Ittria, Zirconia, and Thorina. Glucina is found in the beryl and in the emer- ald ; Ittria was discovered by Gadolin in a mineral now called Gadolinite, zirconia by Klaproth in the zircon of Ceylon, and Thorina was discovered only a very short time ago by Berze- lius. {Jameson's Journal, October 1829). As none of these, however, are likely to be made the subject of experiment by beginners, it will be unnecessary to say more of them in this place. ikon. 269 ORDER IV— COMMON METALS WHOSE OXIDES CANNOT BE REDUCED BY HEAT ALONE. CHAP. I. IRON. Equivalent 28. Specific gravity, 7-7« 733. For most experiments with this substance, a quantity of iron filings, wire, or turnings should be procured, which will be found much more convenient than larger masses of metal. Put a quantity of iron filings into a plate, and moisten them with water as they become dry. The iron is oxidated after some time, and at the same time attracts a small portion of carbonic acid from the air, so that the rust which is formed is composed of oxide of iron, with a small portion of the carbonate. 735. Throw some iron filings into the flame of a lamp or candle, or of any combustible matter. The filings take fire as they combine with the oxygen of the air, and burn with bril- liant scintillations. 736. Procure a quantity of harpsichord wire, and coil seve- ral folds of it (twisted together) round a piece of wood, an iron tube, or the neck of a retort. Fix one end of the coil into a cork made to fit a wide glass jar of the form represent- Fig. 63. ed in the figure, and tie a little thread round f-g^ the other extremity, dipping it afterwards into flowers of sulphur; a small portion adheres to the thread, and is melted by holding it over a candle, taking care not to allow it to take fire, and blowing out the flame imme- -7 diately if it should. By dipping it again in the sulphur, and melting what adheres the 270 PROTOXIDE OF IRON. second time in the same manner as before, the thread acquires a coating of sulphur. If the sulphur is then kindled, and the wire introduced in this state into a jar full of oxygen, the heat produced by the rapid combustion of the sulphur is sufficient to inflame the iron, which burns brilliantly, and gives out a number of sparks. 737- The jar containing the oxygen may be from four to six inches in diameter, and from ten to fourteen long, open below, and provided with a cork or stopper, fitting accurately to the opening above. When the cork is put in, it may be inverted full of water on the shelf of the pneumatic trough, and filled with oxygen in the usual manner. It is then removed on a tray to a shallow iron bason filled with water, (or an earthen bason with some sand at the bottom does equally well) supporting it directly by two or three small pieces of brick or tile, to prevent the globules of melted oxide of iron that are produced during the combustion breaking the jar if they should run to the side when they have fallen under the water. When every thing has been adjusted, the cork is taken out, the sulphur at the end of the iron wire inflamed, introducing it steadily, and pressing the cork tightly into its place. As the combustion proceeds, the pressure of the air forces the water in the bason (which must be always kept full) into the jar to supply the place of the oxygen as it is consum- ed. 738. Much thicker wire than what is used for harpsichords may be made to burn in oxygen gas, and indeed if the extre- mity of a thick rod or bar of iron is heated to whiteness in a furnace, and put immediately into a large vessel full of oxygen, it will burn in the same manner as the thin iron wire. 739. Protoxide of Iron (Equivalent 36 = Oxyg. 8+28 Iron) is not easily procured in a pure state, from the great affinity which it has for oxygen, and the facility with which it attracts an additional portion of this element even from at- mospheric air when moistened. This compound, however, is the principal product of the combustion of iron in oxygen gas, and it may be procured also by transmitting watery vapour over metallic iron in the manner directed for the preparation of hy- drogen ffas. The black oxide of iron that falls in scales from PEROXIDE OF IRON. 271 iron when it is at a high temperature, and hammered on the anvil, appear from recent experiments to be composed of the protoxide and peroxide of this metal. 740. Add a solution of potassa or soda to a solution of the sulphate of iron ; if it contains no peroxide, a precipitate of a white colour is thrown down, which is a compound of the protoxide of iron and water. It soon becomes green, how- ever, and ultimately assumes a red colour on exposure to the air, attracting an additional quantity of oxygen. 741. To prepare Peroxide of Iron,* a crucible may be filled with green sulphate of iron, and exposed to a good red heat in a furnace or open fire for one or two hours, luting a cover on with a little clay previously, and leaving a small aperture for the escape of gaseous matter. The water of crystallization in the green sulphate is completely expelled with part of the sulphuric acid, the rest of which is decom- posed, communicating part of its oxygen to the protoxide of iron, while sulphurous acid is disengaged. It is of a red colour, very dark at first, but becoming lighter when it cools. Some other compounds of iron and oxygen have been de- scribed, but their composition is still uncertain. 742. Put a drop of nitric or muriatic acid on steel, and wash it afterwards with water. A black spot remains on the sur- face, steel being composed of carbon and iron, and the acid; acting on the latter while the former remains. The same ap- pearance is presented with cast iron, which contains still more carbon than steel, but forged iron containing no carbon (or at least only a very minute portion), still presents a bright me- tallic surface after it has been acted on by an acid. Steel con^ tains from T | 5 to j 5 of its weight of carbon, and east iron from 2V to iV It is evident from this also, that when steel or cast iron is used for the preparation of hydrogen gas, a smaller- quantity will be obtained from a given weight of materials than when forged iron is used. * Its proper equivalent number is 80, being composed of two equivalents of iron (56) and three of oxygen (24.) It is usually represented, however, by the number 40, and is said to consist of one equivalent of iron, and one and a half of oxygen, a mode of expressing its composition which has crept into ge- aeral use, though it is certainly very incorrect. 272 TESTS OF IltON, 743. Expose a piece of soft steel to a bright red heat and plunge it suddenly in cold water. It will be found to have be- come so exceedingly hard as scarcely to be affected by a file, and to have lost its toughness and elasticity, being also very brittle. 744. Expose a piece of hard steel to a temperature between 400 and 600 by placing it in hot oil or melted pewter ; it re- gains its toughness and elasticity, and by varying the tempera- ture to which it is exposed, it acquires various degrees of hard- ness, so as to be rendered fit for the different purposes to which it is applied. It is in this manner that steel is tempered; in- stead of using hot oil and a thermometer to regulate accurate- ly the temperature to which it is exposed, it is often heated in the open air, judging of the temperature by the colour it pre- sents, as it then assumes a variety of tints from a very faint yellow to a dark blue according to the degree of heat. These different shades are produced by a little oxide of iron forming on its surface, gradually increasing in quantity as the tempera- ture rises. Instead of plunging a piece of hard steel into hot oil, it may be held over a spirit lamp till all the different tints have been produced. 745. A number of tests have been proposed for detecting iron. The most delicate test of iron in solution is the gall- nut, which produces a black colour with solutions containing a very minute quantity even when no indication of the presence of iron has been obtained by using the infusion of galls, though the cause of this has not been explained. All that is necessary in using it for this purpose is to bruise it and throw it into the liquid under examination, part of which assumes a black or bluish colour in a day or two if any iron is present. It is pro- duced by the tannin and gallic acid of the gall nut which are slowly dissolved by the water combining with the oxide of iron. 746. Pour a little of the infusion of galls into sevsral glasses of water to which different quantities of a solution of sulphate of iron have been added to sec the different shades of colour which they present : the precipitate is of a very dark blue or black colour. 747- The ferrocyanate of potassa is another very delicate SALTS or ikon. 273 test of iron, throwing clown a rich blue coloured precipitate when dissolved in water and added to a solution of a salt of iron in which the metal is in a high state of oxidation. 748. With salts of the protoxide of iron it gives a white precipitate, and when the solution contains both protoxide and peroxide of iron, which is generally the case, the precipitate presents a variety of shades between a white and a deep blue according to the proportion of the different oxides. 749. If it is required to show the pure white precipitate which the protoxide gives with this test, the best method is to use a solution of the hyposulphate of iron made by shaking iron filings in a small bottle nearly full of a solution of sul- phurous acid in water, the iron attracting oxygen from the sul- phurous acid and being dissolved without any effervescence. 750. Add a solution of the sulphocyanate of potassa (369) to a solution of a salt of iron containing this metal in the form of a peroxide ; it immediately becomes of a deep red colour. 751. In examining a liquid with the view of detecting iron, any portion of this metal in the state of protoxide may be easi- ly converted into peroxide by boiling it for a short time with a little nitric acid. 752. Add solutions of the pure alkalis or their carbonates to solutions of the salts of iron ; the alkalis unite with the acids previously in combination with the oxide of iron, forming salts which remain in solution, while the latter is precipitated ; if the carbonated alkalis have been employed, it will be com- bined with carbonic acid. SALTS OF IRON, &C 753. Nitrate of Iron may be obtained by putting an ounce or two of iron turnings into a glass flask or bottle with an ounce of nitric acid, previously mixed with seven or eight ounces of water. The iron is slowly oxidated and dissolved, and on concentrating the solution with a gentle heat, green crystals of the nitrate may be obtained. They are seldom applied to any use. T 274 SALTS OF IRON. 754. If the acid is not diluted with so much water, the iron attracts a larger" quantity of oxygen, and the liquid acquires a reddish brown colour, pernitrate of iron being formed, which does not crystallize on evaporating the liquid. 755. When only a small quantity of water is added to the acid, and the iron in a minute state of division, the action is very turbulent. Put three or four drachms of nitric acid into a glass, add two drachms of water, and throw into it 200 or 300 grains of iron filings. Part of the acid is immediately de- composed, the iron is oxidated and combines with another por- tion of acid, and a large quantity of fumes are disengaged, which must be carefully avoided, being composed principally of nitrous acid and nitric oxide ; what remains consists of nitrate of iron with an excess of acid. 756. The Sulphate of Ikon is prepared in large quanti- ty for commercial purposes by exposing the native sulphuret of iron to air and moisture, the iron being converted into an oxide and the sulphur into sulphuric acid by attracting oxy- gen. On the small scale it may be prepared by mixing 6 parts of iron with 10 of sulphuric acid and 60 of water, evaporating the solution in a glass or earthen vessel, after the effervescence arising from the disengagement of hydrogen gas has ceased, till a rod dipped into it presents appearances of crystallization when held in the air. The solution may then be filtered, and green crystals of the sulphate will be formed as it cools. The reaction that takes place between the iron, the sulphuric acid, and the water has been explained in 51 and 52. The crys- tals contain nearly fths of their weight of water, and are solu- ble in two parts of cold and in less than their weight of boiling water. 757. Pour some strong sulphuric acid on iron filings in a glass flask. Instead of a turbulent action taking place as in the preceding instance, scarcely any traces of decomposition are observed ; if, however, the flask is now exposed to heat (a chauffer is better than a lamp in the present instance), the iron takes oxygen from part of the acid and sulphurous acid is dis- engaged, the oxide of iron combining with another portion of the sulphuric acid which is not decomposed, and forming sul- SALTS OF IRON. 275 phate of iron. This process is never adopted for preparing the sulphate, but merely for experimental illustration. A /58. Sulphate of iron is sometimes required free from its water of crystallization, as in the preparation of strong acetic acid (398.) For this purpose, it may be exposed to heat in an earthen vessel till it becomes quite dry and of a greenish white colour ; almost all the water is expelled in this manner, and the salt becomes at the same time quite opaque ; the heat must be applied by placing it over a furnace or good chauffer, taking care however not to allow it to be so great as to expel any of the sulphuric acid, otherwise it will acquire a red co- lour, from the formation of some peroxide of iron. 759. Dissolve some of the green crystals of the sulphate in spring water ; the solution appears quite turbid from the free oxygen which it contains converting part of the protoxide of iron in the sulphate into peroxide of iron, a portion of which is deposited ; the acid that is sufficient to retain a given quan- tity of iron in the state of protoxide in solution not being able to dissolve it all when it acquires an additional portion of oxy- gen. Drop a little sulphuric acid into the solution and it will become quite clear, the precipitated oxide being dissolved again. 760. Boil a solution of an ounce of the crystallized green sulphate of iron in two or three ounces of water with a drachm or two of nitric acid, and evaporate the solution to dryness in an earthen vessel. Whenever the nitric acid is added to the solution, it assumes a very dark colour, and the dry mass which is afterwards obtained consists principally of the per- sulphate of iron, the oxide having attracted an additional por- tion of oxygen from the nitric acid. On digesting it in water the persulphate is dissolved and a solution of a reddish brown colour is obtained. 761. A similar solution may be obtained by exposing a so- lution of the green sulphate to the air for a long time, part of the peroxide that is formed being deposited. 702. The different methods of preparing Sulphuret of Iron have been described in 96, 197? and 198. 763. Carbonate or Iron may be obtained by dissolving 144 grains of the crystallized subcarbonate of soda and pour- 276 SALTS OF IRON. ing the solution into an ounce of water in which 139 grains of the crystallized green sulphate of iron have been dissolved, collecting the precipitate on a filter. The reaction that takes place is represented in the diagram, the salts being mixed in equivalent proportions, making allowance for the water of crystallization. Before decomposition. After decomposition. a'u .■' r««j (Soda 32 /- 72Sulph. of Soda, Carbonate ot soda -< ^ , » ac% ' r ( Carb. Ac. 22 w' o'i i, '•-■* n fSulph. Ac.40'-- \. Sulphate of Iron j / Iron 36 _\> 58Carb . of Iron . The sulphate of soda remains in solution, and the precipitated carbonate is washed on a filter with hot water which has been boiled to expel the air it usually contains. It soon attracts oxygen from the air, and assumes the same appearance as the rust of iron, losing also the greater part of its carbonic acid. 764. Put some of the precipitated carbonate as soon as it has been washed with hot water, and while still moist, into a bottle half full of carbonic acid water, and shake them to- gether. A solution of the bicarbonate of iron is obtained, which possesses the same properties as the carbonated chalybeate mineral waters, and in which the iron may be detected by the usual reagents. Expose part of it to heat in a Florence flask ; the excess of carbonic acid is disengaged, and the carbonate again precipitated. 765. Put some iron filings into a small flask or bottle, after exposing them to a red heat in a crucible to decompose any oily matter, and pour in carbonic acid water till it is about two-thirds full. On shaking it for a few minutes, part of the iron will be found to have been dissolved. In this case, the iron is oxidated at the expense of a portion of water which is decomposed, and is then dissolved by the carbonic acid. Dr. Marshall Hall found that when water is completely deprived of carbonic acid, iron does not decompose it at natural tem- peratures. 766. Dr. Ure recommends a similar solution to be prepared by dissolving a little sulphate of iron and bicarbonate of potas, sa in cold water, agitating them together in a close vessel. SALTS OF IKON. 277 The sulphuric acid of the sulphate may be supposed to com- bine with the potassa forming sulphate of potassa, which does not particularly affect the rest of the liquid, the two equiva- lents of carbonic acid going to the oxide of iron and retaining it in solution. 767. The Liquor Ferri Alkalini of the London Col- lege may perhaps be classed along with the carbonate of iron, as its medicinal properties may be presumed to depend upon a bicarbonate of iron from the mode of its preparation, though other opinions have been entertained with respect to the peculiar state of combination in which the iron exists ; the following is the formula for preparing it : — Mix two drachms and a half of iron with two fluid ounces of nitric acid diluted previously with six fluid ounces of water, and after all action has ceased, pour off the clear liquid, which is a solution of the nitrate of iron with excess of acid, and add it in small quantities at a time to six fluid ounces of a solution of the subcarbonate of potassa, made by dissolving four parts of the salt in three of water. The iron is thrown down at first of a reddish brown colour, the nitric acid previously in combination with it uniting with part of the potassa, and disengaging carbonic acid, part of which escapes with effervescence, while the rest combines with a portion of the carbonate of potassa that is not decom- posed, and converts it into bicarbonate of potassa. On stir- ring the mixture with a glass rod, the precipitated oxide or carbonate of iron is redissolved by the bicarbonate, and a so- lution obtained of a very deep red colour ; it is then allowed to stand for six hours, when some crystals of nitrate of potassa are deposited, and the clear liquid decanted. This solution is extremely apt to be decomposed, and the iron is thrown down even by diluting it with several times its bulk of water ; it must be kept in close vessels. 768. Acetate of Iron maybe prepared by digesting iron in diluted acetic acid, or by adding a solution of the sulphate of iron to a solution of the acetate of lead, sulphate of lead being precipitated, while acetate of iron remains in solution. The tincture of the acetate of iron of the Dublin College is made by mixing two parts of the acetate of potassa and one of zyo SALTS OF IRON, INK. sulphate of iron in an earthen mortar till a soft mass is ob- tained, and digesting it afterwards in alcohol ; sulphate of potassa remains. 769- The Tartrate of Potassa and Iron is prepared by mixing two parts of the super-tartrate of potassa and one of iron filings intimately together, and exposing the mixture for 15 or 20 days to the air, moistening it frequently with water. The iron is oxidated, and combining with the excess of acid in the cream of tartar forms tartrate of iron, which remains in combination with the neutral tartrate of potash that is left, and on boiling it for a short time in four times its weight of water, it is dissolved. It may be obtained in the solid form by filtering and evaporating the solution, but it does not crystallize. 77^. Gallate of Iron may be formed by adding a solu- tion of gallic acid to a solution of a salt of iron, being thrown down in the form of a dark coloured precipitate, which is the basis of writing ink ; gallic acid is never used, however, for this purpose in a pure state. 771- Many receipts have been given for the preparation of ink ; the following is M. Ribaucourfs ; (Ure's Diction- ary). Boil two ounces of logwood in small chips with four ounces of galls reduced to a coarse powder, in six pounds of water, till half the liquid is evaporated. Strain the decoc- tion through a linen cloth, and then add in fine powder two ounces of the sulphate of iron, half an ounce of the sulphate of copper, an ounce and a half of gum arabic and half an ounce of sugar. The mixture must be stirred till the liquid acquires a uniform appearance ; after allowing it to stand for 12 hours the ink should be decanted and put into bottles. 772. In this process, the gallic acid of the logwood and galls along with the tannin unites with the oxides of iron and copper of the salts, forming the dark coloured precipitate which is diffused through the liquid, and kept in suspension by the gam and the sugar which are added to render it of a proper consistence. The sulphate of copper gives a deeper shade to the mixed precipitate, but it is not always used. When ink contains copper, it may be easily detected by metallic iron, INK. 279 a portion of which is taken up on dropping a little ink upon it, and replaced by a coating of metallic copper. 773. Pour a solution of chlorine in water into a little ink mixed with water ; the dark colour immediately disappears. The chlorine acts on the vegetable matter alone, however, and if a solution of an alkaline hydrosulphuret is then added to it, sulphuret of iron will be precipitated. 774«. Write on some paper with common ink, and when it is dry, divide it into four pieces and put them into a solution of chlorine in water till the writing disappears. 775. The iron of the ink being still left where it was, the characters may be recalled ; put one of the pieces of paper into an infusion of galls, another into a solution of the hydro- sulphuret of ammonia, and a third into a dilute solution of the ferrocyanate of potassa. The oxide of iron will be rendered black by the infusion of galls and the hydrosulphuret, and blue by the ferrocyanate, and the characters can in general be distinguished as easily as before. 776- Place the last piece of paper in muriatic acid diluted with 12 or 15 parts of water. All the iron will be dissolved in a short time, and then it will b>e impossible to recall the characters. 777* Oxalic acid and some other acids can also dissolve the iron, and hence they are constantly employed for taking iron moulds from linen, being less corrosive than the muriatic acid. 778- If paper be written on with a weak infusion of galls, no characters will be visible when it is dry, but on dipping it into a solution of the sulphate of iron, they will immediately appear. 779- Similar experiments may be made by writing on paper with a solution of a persalt of iron, and dipping it into a so- lution of the ferrocyanate or sulphocyanate of potassa. The former renders the characters of a fine blue colour, and with the latter they become of a deep red. 780. Ferrocyanate of Iron (pure Prussian blue), is prepared by adding a solution of a persalt of iron to a solution 280 SALTS OF IRON. of the ferrocyanate of potassa as long as any precipitation takes place. If a solution of a protosalt of iron is taken, the pre- cipitate that is thrown down is of a light colour at first, but absorbs oxygen when it is exposed to the air and becomes blue. There is every reason to believe, however, that the blue co- loured compound obtained in this manner must differ in its composition from that which is precipitated blue at first, as we know that oxides in a high state of oxidation combine with a larger quantity of acids than when they contain less of this element. It is indeed soluble to a certain extent in water, and cannot therefore be washed on a filter without considera- ble loss. 781. When very pure and dry Prussian blue is exposed to heat, it soon begins to undergo a kind of slow combustion, and is completely decomposed. Its use in the preparation of cy- anogen and hydrocyanic acid has already been considered. 782. Muriate of Iron may be formed by putting iron filings or turnings into muriatic acid diluted with half its bulk of iron. Part of the water is decomposed ; the oxygen goes to the iron forming a protoxide of iron which is dissolved by the acid, and hydrogen gas is disengaged. The solution has a green colour, attracts oxygen when exposed to the air, and the iron is converted into a permuriate, part of the oxide being deposited. 783. Digest some of the peroxide or rust of iron in about four times its weight of muriatic acid ; a permuriate (almost always with an excess of acid) is obtained in solution. It is this which is employed for the preparation of the tincture of iron, the protomuriate being insoluble in alcohol. 784. When muriate of iron in solution is mixed with muri- ate of ammonia and evaporated to dryness, a compound is obtained which has been called the Muriate of Ammonia and Iron. It is recommended to be prepared by subliming- mixtures of the two salts, or of muriate of ammonia and per- oxide of iron, but it is seldom used. 785. Chloride of Iron may be prepared by evaporating a solution of the muriate to dryness, the oxygen of the LEAD. 281 oxide uniting with the hydrogen of the acid, and leaving the chloride in combination with the iron. CHAP. II. LEAD. Equivalent 104. Specific gravity 11.55. It melts at about 600. 786. Lead is generally obtained from galena, the native sulphuret of lead. To prepare a small quantity from this ore, reduce 120 grains to a fine powder, mix them with 56 grains of iron filings, and expose the mixture to a bright red heat for five or ten minutes in a chauffer with a chimney (15) or in a furnace. Part of the iron unites with the sulphur of the sul- phuret of lead, forming sulphuret of iron, and the metallic lead is melted and may be poured out when the crucible is removed from the furnace. In the diagram giving a view of the theory of the decomposition, only half the quantity of iron is repre- sented, as 28 parts of iron are sufficient to combine with all the sulphur in 120 of the sulphuret, and an excess is em- ployed solely for the purpose of bringing the sulphur of the sulphuret into more intimate contact with the iron, which is not easily reduced to a minute state of division. Before decomposition. After decomposition. 1 20 Sulphuret f Lead 104 1 04 Lead. of Lead . . . ( Sulphur 16 i ^- > _ 28 Iron 28 — — ^ 44 Sulphuret of Iron. 787- When lead is required particularly pure for delicate experiments, it may be obtained by precipitation from a solu- tion of any of its soluble salts. Dissolve an ounce of the crys- tallized acetate of lead in 34 ounces by measure of water, and put a piece of zinc into the solution, suspending it at the top 4 282 LEAD. by a string fixed to a wire laid across the mouth of the jar or glass containing the solution ; part of the zinc is immediately dissolved and the rest coated with metallic lead, which conti- nues to be precipitated till the acetate has been completely decomposed, 34 parts of zinc (one equivalent) being taken up for every 104 of metallic lead (one equivalent) thrown down, so that a solution of the acetate of zinc remains. If the solu- tion is put into a long glass or jar, and not agitated, the lead is deposited in an arborescent form, presenting a very beautiful appearance ; it is in this manner that the Lead Tree, as it is termed, is commonly prepared. The following diagram shows more precisely the nature of the reaction : Before decomposition. After decomposition. 84 Zinc 34 --^jr 92 Acetate of Zinc. f Acetic Acid . 50 '"/'' 162 Acetate of Lead \ Lead 104 - - 10 * Lead - 196 196 196 r a r° f i ^ide of | Oxyg.^ 8 (. Lea 788. Melt some metallic lead and expose it to a red heat in an iron ladle. A film collects speedily on its surface, which consists of metallic lead mixed with the protoxide. 789- Put some phosphate of lime (prepared from bones, 675) in powder on a flat piece of dried clay or on any earthen dish, place 100 or 200 grains of lead above it, making a very slight depression in the centre that the lead may not run over when melted, and expose it to a strong heat in a muffle, so that the air may have free access to it, while it is at the same time excluded from the action of the fuel. The lead soon melts, acquires oxygen from the air, and is converted into pro- toxide of lead which is also melted, and absorbed by the bone ashes. As long as any metallic lead remains, it still rests on the top, the bone ashes not absorbing any metallic parts but only the melted oxide. 790. A muffle is an earthen vessel arched above and closed in at every side except in front, so that it may be exposed to a very high temperature by building it in a furnace in the man- PROTOXIDE OF LEAD. 283 Fig. C4. ner represented in the figure, while any substance to be exposed to a high temperature, and to the action of the air at the same time, may be introduc- ed at the open end. This furnace with the muffle is used in the process of cupellation, and if it should not be found convenient to construct one for 'M= <*~F yS the purpose, a portable furnace with — ' — — * an opening at the side for putting in a small muffle may be employed. Muffles are used of all sizes from two or three inches long and an inch and a half broad (to be used with a chauffer furnace) to fifteen or eighteen inches long and seven or nine broad. The one I generally use is ten inches long, five broad, and about four and a half high. 791. A muffle should never be exposed suddenly to a strong heat, as it is then very apt to crack. The fire must be raised very gradually, beginning at first with little more than may be necessary to prevent it from going out. The fuel is introduced from an opening above, and great care must be taken not to allow any of it to fall directly upon the muffle. The bottom should rest on a brick about four or five inches above the branders, and its sides should be at least two inches from the side walls of the furnace, that the fuel may fall readily below. 792. To prepare protoxide of lead, (equiv. 112 = oxyg. 8 -f- 104 lead), the nitrate of lead may be exposed to heat in a crucible placed in the fire, taking care not to urge the heat, otherwise the oxide will melt and soon destroy the crucible, the siliceous matter which it contains forming a very fusible glass with the oxide of lead. The Massicot of commerce, which is of a fine yellow colour, is a protoxide of lead, and is prepared by exposing the crust that forms on the surface of melted lead to heat and air. By heating it till it has been partially fused, it is obtained in the form of scales, which have usually a reddish colour, arising from the formation of a small 28i TESTS OF LEAD. portion of the red oxide of lead, and in this state it is termed Litharge. 793. Add a solution of potash, soda, or ammonia, to a solu- tion of the acetate or nitrate of lead. The alkali combines with the acid, and protoxide of lead is immediately precipitated in combination with a portion of water, and of a white colour. The protoxide of lead is the only oxide that forms salts with the acids. 794. The Red Oxide or Deutoxide of Lead cannot be prepared easily on the small scale ; it is formed by directing a stream of air upon the protoxide till it acquires a red colour, taking care not to melt it. By exposure to a stronger heat it parts with a portion of its oxygen, and protoxide of lead remains (21.) 795. To prepare Peroxide of Lead, 232 grains of the red oxide (which may be regarded as a compound of the protoxide and of the peroxide) may be digested in a Florence flask for a short time with a drachm of nitric acid, and an ounce of water. The protoxide is dissolved, combining with the acid, and forming nitrate of lead which remains in solu- tion, and the brown peroxide may be separated by filtration. It is not applied to any use. 796. Mix 200 or 300 grains of any of the oxides of lead with a ninth part of its weight of charcoal, and expose it to a good red heat in a furnace or open fire. The carbon com- bines with the oxygen of the oxide, forming carbonic oxide or carbonic acid gas, and metallic lead remains in the crucible. 797- Salts of lead in solution are easily detected by a stream of sulphureted hydrogen gas applied in the usual way, the sulphur of the gas combining with the metallic lead, and forming a dark coloured sulphuret which is precipitated, while the hydrogen unites with the oxygen of the oxide and forms water. Instead of passing a stream of the gas through the solution, many prefer adding a solution of the subcar- bonate of soda or potassa in the first place, the carbonic acid of the carbonate uniting with the oxide of lead, and forming SALTS OF LEAJ). 285 a white coloured precipitate (carbonate of lead), and on shak- ing it with sulphureted hydrogen water, it immediately be- comes black. A solution of the hydro-sulphuret of ammonia may be used instead of sulphureted hydrogen gas. 798. Exposed to heat before the blowpipe and on charcoal, most of its salts readily give a globule of metallic lead. 799- Solutions of the soluble salts of lead are transparent and colourless, and give copious precipitates of a white colour with alkalis and alkaline carbonates, consisting of oxide and carbonate of lead. Sulphuric acid and solutions of the sul- phates throw down a white precipitate of the sulphate of lead ; muriatic acid and the solutions of muriates give a white pre- cipitate of chloride of lead, the chlorine of the acid uniting with the metallic base of the oxide, while its hydrogen com- bines with the oxygen ; hydriodate of potassa gives a rich yellow- coloured precipitate which is composed of iodine and metallic lead, a reaction taking place similar to what has just been explained with respect to muriatic acid and oxide of lead. 800. When silver, bismuth, or mercury are suspected to be present in the same solutions with lead, the black preci- pitate thrown down by sulphureted hydrogen cannot be relied on as an indication of the presence of lead, these metals also giving a dark precipitate with this gas. Zinc and iron precipitate metallic lead from solutions of any of its salts containing no excess of acid (7&7) ■ 801. Nitrate of Lead may be obtained by digesting metallic lead in nitric acid diluted with seven parts of water, continuing the heat as long as any effervescence takes place, and evaporating the solution after filtration till a pellicle ap- pears on its surface, when it may be set aside to crystallize. The crystals contain no water, and deflagrate when heated with inflammable matter. 802. Sulphate of Lead is formed whenever sulphuric acid or a solution of a sulphate is added to a solution of a salt of lead; it is very insoluble, and every 152 parts (one equi- valent) contain exactly 104 of metallic lead. The quantity of lead in a solution of a salt of lead may be ascertained ACETATE OF LEAD. easily by precipitating it in the form of sulphate of lead, and carefully drying and weighing the precipitate. 803. Phosphate of Lead is also a very insoluble salt, and may be obtained by adding a solution of the phosphate of soda to a solution of the acetate of lead. 804. Carbonate of Lead may be prepared by adding a solution of an alkaline carbonate to a solution of the nitrate or acetate of lead. On the large scale it is prepared by exposing metallic lead to the vapour of vinegar. It is usually called Ceruse or White Lead. 805. Acetate of Lead, or Sugar of Lead, may be ob- tained by boiling Carbonate of Lead in diluted acetic acid, but it is seldom made on the small scale, as there are several very extensive manufactories where it is prepared. The car^ bonate should be boiled with the acid till it ceases to take up any more, the solution filtered through paper, and evapora- ted till a pellicle appears on its surface, crystals of the acetate being deposited as it cools. They are soluble in about four parts of water, and the solution has a sweet but styptic taste. 806. Dissolve some acetate of lead in spring water ; the so- lution will be quite turbid, the muriatic and sulphuric salts which it generally contains precipitating part of the oxide of lead ; the carbonic acid also produces the same effect. Filter the solution and add some carbonic acid water to the clear liquor ; a copious precipitate is thrown down, consisting of carbonate of lead, and if a stream of carbonic acid is passed through the solution for some time, half of the oxide will be precipitated, the acetic acid previously in combination with it combining with the acetate which is not decomposed, and con- verting it into binacetate of lead, which remains in solution, and is not decomposed by carbonic acid. 807. The Subacetatjs of Lead is prepared by boiling the yellow oxide of lead, or litharge reduced to a fine powder, in diluted acetic acid ; or a solution of the acetate may be used which will afford a similar solution with the oxide of lead more speedily ; 189 grains of the crystallized acetate may be taken with 112 of the protoxide of lead, and about nine ounces of coprER. 287 water, previously boiled for some time to expel all the carbo- nic acid which it may contain. It bears a considerable re- semblance to the acetate in all its leading chemical relations, but is more easily decomposed, does not crystallize so readily, and is less soluble in water. CHAP. III. COPPER. Equivalent 64 ; Specific gravity 8.8. It melts at a bright red lieat. 808. When copper is required extremely pure, or in a very minute state of division, it may be obtained by putting a piece of zinc into a solution of the sulphate of copper, the zinc taking the oxygen of the oxide of copper and the sulphuric acid, and sulphate of zinc remaining in solution, while the eopper is precipitated in the metallic form. Iron may be used instead of zinc ; in either case the metal employed to preci- pitate the copper from the solution may be left in the liquid till its blue colour almost entirely disappears. 809. If a piece of copper is wanted with a bright metallic surface, it may be easily obtained by exposing it to a red heat in an open fire for ten minutes, and then quenching it sud- denly in cold water. The copper speedily attracts oxygen when heated in the fire, and scales of a red-coloured oxide are formed on its surface. On putting it into the water, the metal that still remains immediately contracts, and the oxide is thrown off. 810. Protoxide or Copper may be procured by mixing a solution of an alkali with a solution of the protomuriate of copper, the acid combining with" the alkali and remaining in solution, while the oxide is precipitated in combination with a portion of water. 811. The usual method of obtaining the Peroxide of Copper is by exposing the nitrate to a red heat in a crucible. 288 tests or cotter. All the nitric acid is expelled, and nothing remains but the peroxide of copper, quite free from water, and of a very dark colour. 812. Expose some of the peroxide of copper to a bright red heat in a crucible with a seventh part of its weight of charcoal ; carbonic oxide is disengaged and a button of me- tallic copper remains. 813. Put some of the peroxide of copper into a small bot- tle nearly full of the water of ammonia, and shake it frequent- ly. Part of the oxide is dissolved, and the solution has a very rich blue colour. If a quantity of copper filings be added to the solution, and the bottle well closed, so as completely to ex- clude the access of the air, one portion of the metallic copper will combine with part of the oxygen in the peroxide, reduc- ing it to the state of protoxide, while it is also converted into protoxide, and a clear and colourless solution is obtained in a few days, consisting of water of ammonia and protoxide of copper. If the cork is then opened, and air allowed to enter freely, the blue colour will again return, the protoxide attract- ing oxygen and being converted into peroxide. 814. Put some metallic copper into water of ammonia and allow them to remain mixed together for some hours ; the copper acquires oxygen from the water and a small portion of oxide is formed which is speedily dissolved by the jimmonia, and the usual blue colour appears, 815. Copper is easily detected when in solution by the dark reddish brown precipitate which is thrown down by so- lutions of the ferrocyanate of potassa and hydrosulphuret of ammonia. Ammonia added to a solution of any of its salts unites with the acid and precipitates oxide of copper, which may be re-dissolved by an additional quantity of ammonia, the solution acquiring the characteristic blue colour. By zinc and iron metallic copper may be obtained- salts or copper, &c. 816. To prepare Nitrate of Copper, put six parts of cop- per clippings into four of nitric acid, diluting it with twice its SALTS OF COPPER. 289 bulk of water, and digest the mixture for a short time till all effervescence ceases. Then pour off the clear solution, and evaporate it till a pellicle begins to appear on its surface, when it may be set aside to crystallize. During the solution of the copper in the acid a large quantity of irritating fumes are pro- duced which ought to be carefully avoided ; they are formed by the nitric oxide that is disengaged attracting oxygen from the air and being converted into nitrous acid, (see 113). Nitrate of copper is a very deliquescent salt, and must accord- ingly be kept in close vessels. It has been used lately with great success as an escharotie. 817- Spread a drachm or two of the nitrate in powder on a piece of tin foil several inches square, moisten it with two or three drops of water, and fold it up quickly, taking care to throw it down whenever it begins to grow hot. The tin de- composes it, attracting oxygen from the nitric acid; great heat is produced at the same time and a quantity of gas evolved ; a number of sparks are also seen, small portions of the tin burning with a red light. 818. Sulphate of Copper is seldom prepared in the labo- ratory, as it is manufactured in large quantity for commercial purposes. Its solution in water crystallizes readily when eva- porated till a pellicle appears on its surface. The crystals are soluble in four parts of cold and two of hot water. They con- tain a little more than a third of their weight of water of crys- tallization. 819- The Ammoniated Copper of the different colleges is prepared by mixing two parts of the crystallized sulphate of copper with three of the common carbonate of ammonia, rubbing them in a mortar till they become quite moist, and the mixture acquires a very rich blue colour ; it should then be dried with a very gentle heat, and put immediately into bottles which must be well stopped. In this process, the ammonia of part of the carbonate unites with the sulphuric acid and oxide of copper in the sulphate, and carbonic acid is disengaged with effervescence, the water of crystallization in the sulphate being set at liberty and rendering it quite moist, u 2Q0 SALTS OF COPPER* If it is exposed to the open air, for some time, all the ammonia is disengaged, and nothing remains but dry sulphate of copper. 820. Sulphuket of Copper may be prepared by mixing one part of sulphur with three of copper filings in a glass flask, and exposing the mixture to heat in the manner describ- ed for the preparation of sulphuret of iron in 1 98. A vivid glow of light attends the combination. 821. Carbonate of Copper is easily obtained by adding a solution of the carbonate of potassa to a solution of the sul- phate of copper, as long as any precipitation takes place. It is of a greenish blue colour, and dissolves with effervescence in diluted sulphuric, nitric, muriatic, and acetic acids. 822. Digest verdegris (which is composed of acetic acid and the peroxide of copper) in five or six times its weight of water for half an hour in a Florence flask ; it is resolved into two salts, a subacetate which is insoluble, and a binacetate which remains in solution ; they may be easily separated by filtra- tion, and the solution of the binacetate gives crystals on eva- poration. Every three equivalents of verdegris give one equi- valent of each of these salts ; the reaction that takes place is represented in the annexed diagram, omitting the water which the verdigris contains, as it does not suffer any material change. Before decomposition. After decomposition. J Acetic acid 50 -;;."?" 180 Binacetate of Copper. er egns-^ p erox CO pp er 80 -"''V' . r , . f Acetic acid 50 •-'' Verdegris < -[> on ° ( .rerox. copper 80 v. f Acetic acid 50 *^\^ Verdegris J p crQX CO pp cr 80 ^^-^> 210 Subacetate of Copper. 823. Verdegris is frequently adulterated with chalk or plas- ter of Paris. To detect either of the substances, all that is necessary is to mix some with water in a glass, adding a little sulphuric acid, and stirring the mixture with a glass rod. All the verdegris will be dissolved, and a blue coloured solution of the sulphate of copper formed, the acetic acid of the verdegris remaining in the liquid; if any sulphate of lime or chalk .SALTS OF COPPER. 29l should have been mixed with it, a white powder will remain at the bottom of the liquid. 824. Binacetate or Copper is usually prepared by dissolv- ing carbonate of copper or verdegris in distilled vinegar, evapo- rating the solution till a pellicle appears on its surface. It gives octohedral crystals on cooling, which contain about a ninth part of their weight of water, and are soluble in nearly five parts of boiling and twenty of cold water. 825. Put some Dutch gold leaf (which is composed of cop- per and zinc) into a bottle of chlorine gas, using the apparatus represented in Figure 33, page 48. It immediately takes fire, and burns with a red light ; chloride of copper and chloride of zinc being formed. 826. The bichloride of copper may be obtained by exposing a solution of the permuriate of copper to a temperature not exceeding 400, continuing the heat till it is evaporated to dryness. 827- The Permuriate of Copper is prepared by digest- ing the peroxide of copper in muriatic acid, diluted with an equal bulk of water ; precipitated carbonate of copper may be used instead of the pure peroxide. The solution acquires a very dark green colour. 828. The Protomuriate of Copper may be obtained in solution by mixing copper filings with a solution of the per- muriate in a bottle, shaking it frequently, and excluding the action of the air ; in a few days the decomposition is complete, and the solution becomes transparent and colourless. 829. The salts of the protoxide are generally free from colour, but those of the peroxide have a deep blue or green colour. 830. All the salts of copper communicate a green tint to inflammable matter in a state of combustion when they are moistened. This is shown best by mixing ten or twelve grains of the permuriate of copper with half an ounce of alcohol, and exposing the mixture to a good heat over a chauffer, inflam- ing the alcohol whenever it begins to boil. 292 ZIKC. CHAP. IV. ZINC Equivalent 34. Specific gravity 7- It melts at a tempera- ture about 700. 831. Mix 500 grains of the oxide of zinc with 100 of char- coal, make the mixture into a paste with oil, and expose it to a bright red heat in a furnace. The carbonaceous matter com- bines with the oxygen of the oxide, forming carbonic acid or carbonic oxide, and metallic zinc is at the same time volatilized, burning with a fine bluish green-coloured flame, and being again converted into oxide of zinc. Hence, the difficulty of obtaining zinc in the metallic form by the usual process for reducing a metallic oxide ; in manufactories, the pots or crucibles con- taining the mixture from which it is procured are closed at the top, and a tube open at both ends made to pass through the bottom, the metallic zinc and carbonic acid disengaged en- tering at one of the extremities of the tube within the cruci- ble, and being conveyed away by the other, to which another tube is fitted when the zinc begins to appear, condensing in it and dropping into a tub of water which is placed below. 832. When zinc is required in small fragments, it is easily obtained by melting it in an iron ladle and dropping it into water. Though classed along with the brittle metals, it can- not be easily broken into very small pieces by a hammer. 833. Put half an ounce of zinc into a crucible capable of containing eight or nine ounces of water, and expose it to a good red heat in a furnace or open fire. A crust of oxide soon gathers on its surface, and in a short time part of the metallic zinc begins to be volatilized, burning with a rich bluish green flame ; if it is then removed from the fire, inclining the cru- cible to one side, and the oxide removed from the surface as fast as it is formed, a considerable quantity may be obtained : a portion of the oxide is at the same time carried up mechan- ically by the current of hot air arising from the crucible, and SULPHATE OF ZTtfC. 293 1ms usually the appearance of very fine wool. This is one of the pharmaceutical processes for preparing oxide of zinc. 834. Another method of obtaining oxide of zinc is by add- ing a solution of potassa, soda, or ammonia to a saturated so- lution of the sulphate of zinc, diluted with fifteen times its bulk of water. Care must be taken not to add an excess of any of these precipitants, as it would redissolve the precipita- ted oxide. The best method of proceeding, when the quan- tity of alkali in a given weight of the solution employed is not known, is to add small quantities at a time, taking out a little of the clear solution at the top with a pipette, after shak- ing the mixture well and allowing it to remain at rest for a short time, testing this by itself with a little of the alkaline solution ; if any precipitate is thrown down, more alkali must be added, but if none appear, this shows that all the oxide has been already precipitated. 835. Zinc is easily distinguished from any of the preced- ing metals when in solution by the yellowish white precipitate which it gives with solutions of the hydrosulphuret of ammo- nia, hydriodate and ferrocyanate of potassa. By precipitating the oxide with a solution of potassa, and heating it on char- coal at the blow-pipe, the oxide is reduced, and the metal burns at the same time with its characteristic flame. 836. Nitrate of Zinc may be obtained by pouring ni- tric acid diluted with five or six times its weight of water on metallic zinc, evaporating the solution till a pellicle ap- pears on its surface. If the nitric acid is diluted with a very small quantity of water, as half its bulk, a very violent reaction takes place, and a large quantity of gaseous matter is disengaged ; in both cases the zinc is oxidated by the decom- position of part of the acid and water. 837- Sulphate of Zinc is easily procured in crystals by evaporating the solution that remains after the preparation of hydrogen gas by zinc, water, and sulphuric acid (51), after it has been digested for a short time with an excess of zinc. In the crystals, every equivalent of the sulphate (82) is combined with seven equivalents of water (63.) 838. Carbonate of Zinc and sulphate of potassa are 294 ACETATE OF ZINC. formed when a solution of the subcarbonate of potassa is add- ed to a solution of the sulphate of zinc, a mutual decomposi- tion taking place. The carbonate, being insoluble, is preci- pitated, and the sulphate of potassa remains in solution. The salts should be dissolved separately in eight or nine times their weight of water, that there may be sufficient to retain the sul- phate of potassa in solution when they have been mixed to- gether ; 70 parts of the subcarbonate of potassa are required for the decomposition of 145 of the crystallized sulphate. 839. Acetate of Zinc may be obtained by digesting me- tallic zinc or the oxide in acetic acid, and concentrating the solution by evaporation, when it is deposited in small crystals. It may also be formed by mixing a solution of the acetate of lead with a solution of the sulphate of zinc, a double decom- position taking place in the manner represented in the dia- gram. Before decomposition. After decomposition. , T ■..'. f Ox. Zinc 42 .-■ ^ Acetate of Zinc. bulphate of zinc ■< „ , , . . . _ ( Sulphuric A. 40k y' rT 3 ( Acetic A. 50 -- > \. Acetate of Lead ■{ r\ r •* -n c\ ^^ ( Ox. Lead 112 ^ 152 Sulphate of Lead. The sulphate of lead being insoluble is precipitated, and the acetate of zinc remains in solution. As both salts contain water of crystallization, in the form they are usually met with, allow- ance must be made for this in weighing out the materials. The solution of the acetate of the Edinburgh College is pre- pared by mixing 60 grains of the sulphate of zinc with 80 of the acetate of lead, dissolving each previously in ten ounces of distilled water, and filtering the liquid afterwards to separate the sulphate of lead. 840. Muriate of Zinc may be obtained in solution by mixing muriatic acid and zinc in a glass vessel, diluting the acid with a third of its bulk of water ; hydrogen gas is disen- gaged. ANTIMONY. 295 CHAP V. ANTIMONY. Equivalent 44 ; Specific gravity 6.8. It melts at a tempe- rature a little below a red heat. 841. Mix 400 grains of nitre with 800 of cream of tartar, and 1200 of the sulphuret of antimony, all of them reduced previously to powder, and throw the mixture in small quanti- ties at a time into a red hot crucible capable of containing at least 12 or 14 ounces of water. A rapid deflagration takes place, a large quantity of fumes are disengaged, and metallic antimony is formed at the bottom of the crucible ; allow it to rest in one position after the mixture is completely fused till it becomes cold, before taking the metal out. If the materials should not fuse as the deflagration takes place, the crucible must be returned to the furnace till the mass that remains be- comes quite liquid. 842. In this process, the potassa of the nitre and cream of tartar is fused, and attracts the sulphur of the sulphuret, the metallic antimony being at the same time melted, and falling through the saline matter that floats above. It is evident then, that if the temperature is not sufficient to render the whole completely fluid, instead of obtaining a large button of metal- lic antimony at the bottom, it will be diffused through the mass in minute globules, which will not be easily separated. The nitric acid of the nitre assists the reduction by oxygenat- ing the carbonaceous matter of the tartaric acid and part of the sulphur of the sulphuret of antimony. 843. Another method by which metallic antimony is often prepared from the sulphuret, is by fusing it along with iron filings, and adding a small quantity of nitre. For this purpose 800 grains of the sulphuret may be mixed with 400 of iron filings, exposed to a red heat in a crucible which need not be so large as the one required for the preceding process, and 200 grains of nitre added when the mixture is fused. The sulphur 296 ANTIMONY. combines with the iron, forming sulphuret of iron, which is melted by the heat, and the potassa of the nitre renders the whole more liquid, the metallic antimony collecting at the bot- tom of the crucible as before j after the nitre is added the mix- ture should be stirred with an iron rod before taking it from the fire ; the nitric aeid is completely decomposed. 844. Instead of leaving the materials in the crucible, they may be poured out into an iron mould which should be heat- ed previously to prevent them from cooling too quickly, and to render it completely dry. A small mould may be easily made by folding a piece of sheet iron into the form of a cone. 845. In both cases the heat must never be continued longer than may be necessary to render the mixture liquid, as the an- timony soon begins to be dissipated, burning with a bluish white flame. 846. Expose two or three hundred grains of metallic anti- mony to a bright red heat in a crucible placed in a furnace ; the blue flame with which it burns will be seen very distinct- ly, and a large quantity of white fumes are produced, formed by the combination of the antimony with the oxygen of the air. If the melted antimony is poured out of the crucibls at this high temperature, from a height of ten or twelve feet, and al- lowed to fall upon a stone floor, it instantly divides into an in- finite number of minute globules, all of which run from the part on which it falls, like radii from a common centre, still burning, and leaving a black mark as they roll along, lined on both sides with a white smoke, and producing a very large quantity of fumes. 847- Several methods have been proposed, for the prepara- tion of the protoxide of antimony. The Dublin College recom- mends it to be prepared by throwing a solution of the muriate into a large quantity of water ; but in this case, it is a submu- riate that is precipitated, the oxide retaining a small portion of muriatic acid. To get the whole of the oxide precipitated, (a little remaining in solution, when water alone is used,) and free from muriatic acid, we must pour the muriate into a solution of potassa, taking care to have a slight excess of alkali, the ox- ide is precipitated in the form of a white bulky powder, which ANTTMONY. 297 must be washed repeatedly with water, and then dried. In this case, the alkali unites with the acid, forming muriate of potash, which remains in solution. For most purposes, the submuriate precipitated by water alone, does very well. 848. By digesting the submuriate in a solution of potassa, the acid may be entirely removed. 849- Mix 1000 grains of the sulphuret of antimony, with an equal weight of nitre, put it into a cone of paper, and touch it at the top with a red hot iron wire, after placing it on an earthen dish or iron plate. A rapid deflagration immediately takes place, a large quantity of fumes are disengaged, and a dark brown substance remains mixed with a quantity of saline matter, the latter being composed principally of the potassa of the nitre ; the nitric acid affords oxygen to the greater part of the sulphuret, the sulphur being acidified, and combining with the potassa, while the antimony is converted into a pro- toxide. By reducing it to a fine powder, and washing it re- peatedly with boiling water, all the saline matter is dissolved, and the protoxide is obtained, still mixed, however, with a portion of the sulphuret of antimony, which is not decomposed. In this state, it is employed in the process of the Edinburgh College, for the preparation of tartar emetic, and was formerly called crocus of antimony. 850. Protoxide of antimony may also be obtained, by ex- posing the sulphuret in powder to heat in the open air, the sulphur being converted into sulphurous acid at the same time, and escaping in the gaseous form. By exposing it to a stronger heat in a crucible, it is fused into a glass, commonly called glass of antimony, which has a reddish colour, and is quite transparent. It combines, at the same time, with part of the earthy matter of the crucible in which it is fused, silica being always detected in it, though the quantity varies consi- derably. Glass of antimony is used in the process of the Lon- don College, in the preparation of tartar emetic. 851. If the protoxide is still exposed to heat, after all the sulphur has been burnt off, it absorbs a larger quantity of oxy- gen, and is converted into deutoxide of antimony. This oxide may also be prepared by exposing the peroxide of antimony 298 ANTIMONY. to a red heat. The white fumes that are formed when metal- lic antimony is heated till it inflames, have been usually re- garded as deutoxide of antimony ; but Berzelius affirms, that they are composed of the protoxide, i 852. To prepare Peroxide of Antimony, metallic anti- mony in fine powder, or the pure protoxide, may be added to hot nitric acid, in a green glass flask or evaporating bason, evaporating the solution to dryness, and heating what remains to the temperature of 500 or 600, to expel any water which it may still contain. The temperature must not be increased beyond this, otherwise part of its oxygen will be disengaged ; 200 grains of metallic antimony, and an ounce and a half of acid by measure, will be a sufficient quantity of materials to show the nature of the process, and the appearance of the peroxide. 853. The Oxide of Antimony with Phosphate of Lime, or Pulvis Antimonialis, which was introduced as a substitute for James' powder, is prepared from a mixture of equal weights of hartshorn shavings and sulphuret of antimony. The mixture is exposed to heat in a shallow iron or earthen vessel, till it assumes an ash grey colour, when it may be con- sidered as composed of protoxide of antimony and phosphate of lime, the latter being derived from the hartshorn shavings, while all the animal matter is burnt away. It is reduced to powder, and put into a crucible, which may be coated with clay, and wrapped round with iron wire, luting on a cover, but leaving a small opening at the side ; the crucible is then put into a furnace, and exposed to a white heat for two hours, after which it may be removed. This is the process which is recommended by the Edin- burgh and Dublin Colleges ; the London directs two parts of hartshorn shavings to be used along with one of the sulphuret of antimony. 854. According to the analyses of Pearson, Brande and Phillips, it is usually composed of peroxide of antimony and phosphate of lime, the proportion of these ingredients varying in different specimens, but occasionally a small quantity of the protoxide is found along with the peroxide, which explains the circumstance that it sometimes proves an active medicine, ANTIMONY. 20!) while in other cases it has been found to be perfectly inert, the peroxide having little or no action on the animal economy. It has not yet been determined whether the oxide is merely intimately mixed with the phosphate of lime, or in some pecu- liar state of combination ; nor can we see very well why the antimony should be in the state of a peroxide, after exposure to a white heat for two hours, as the peroxide, at least when prepared in the usual manner (848), parts with a portion of its oxygen on exposure even to a red heat, and is converted into deutoxide of antimony. Salts of Antimony ; Sulphuret and Chloride of Antimony. 855. None of the salts of antimony are of any importance except the sulphate, the muriate, and the tartrate of antimony and potassa, or tartar emetic. 856. The sulphate is easily prepared by boiling metallic antimony reduced to a very fine powder with twice its weight of sulphuric acid in an iron vessel, heating the mixture over an open fire, and stirring it frequently with an iron rod till it becomes quite dry. In this process, the metallic antimony attracts oxygen from part of the sulphuric acid, and sulphur- ous acid gas is disengaged, the oxide of antimony that is formed combining with part of the sulphuric acid that is not decomposed ; the excess of acid is expelled by the heat. The annexed diagram gives a view of the theory of the action, not taking into account the small excess of sulphuric acid that is employed, and the water which the common sulphuric acid always contains. Before decomposition. After decomposition. Sulphur 16 ---^"32 Sulphurous Acid. Sulphuric Acid . Oxygen 8- Oxygen 8 Oxygen 8 Antimony 44 - Sulphuric Acid 40 —^-92 Sulphate of Antimony. 300 SULPHURET OF ANTIMONY. Mr. Phillips has proposed to prepare tartar emetic with the oxide, or rather the subsulphate which is obtained on throwing it into a large quantity of water. 857- Sulphuret of Antimony occurs native, and is the ore of antimony from which the metal is usually procured ; it is separated from the stony matter with which it is mixed by exposing the ore to heat in a crucible with an aperture in the bottom, another crucible being placed below it to receive the melted metal as it flows out. It is better always to purchase it in the form in which it is taken out of the crucible, the pounded sulphuret being frequently adulterated with a large quantity of earthy matter ; I have met with it containing at least a third part of its weight of earthy substances, the greater part of which was silica. 858. By transmitting a stream of sulphureted hydrogen through a solution of tartar emetic, or of any other solutions of antimony, a copious precipitate of a deep reddish brown colour is thrown down, which is composed of sulphuret of antimony and water, the hydrogen of the sulphureted hydro- gen combining with the oxygen of the oxide, and the sulphur with the metallic antimony. 859. To prepare the precipitated sulphuret of the Edin- burgh and London Colleges, the common sulphuret is boiled with a solution of caustic potassa for an hour or two in an iron vessel over a common fire, adding water from time to time that there may be the same measure of liquid on moving it from the fire as at first. It is filtered immediately through a double linen cloth, and sulphuric acid, previously diluted with six or seven parts of water dropped into the filtered liquid (while still warm) as long as any precipitation takes place. 860. In this process a portion of water is decomposed, the hydrogen combining with the sulphur of the sulphuret, and the oxygen with the metallic antimony, both of which are dis- solved, so that the solution may be regarded as a compound of sulphureted hydrogen, oxide of antimony, and potassa. On adding the diluted acid, sulphate of potassa is formed, which remains in solution, and the hydrosulphuret of the oxide of antimony is precipitated. Such is the general nature of the TARTRATE OF ANTIMONY AND POTASSA. 301 reaction which is generally supposed to take place, but many arc inclined to believe that the precipitate which is thrown down by the sulphuric acid is composed of sulphuret of anti- mony and water, the sulphureted hydrogen and oxide of anti- mony reacting on each other when the potash is withdrawn, and producing these compounds. 861. The proportions recommended by the Edinburgh Col- lege are four parts by weight of their solution of potassa, three of water, and two of the sulphuret of antimony. If a solution of potassa of the same strength should not be at hand, equal weights of sulphuret of antimony and fused potassa may be taken and boiled with eight times their weight of water ; an excess of the sulphuret does no harm, as it is not dissolved, and affords a larger surface for the action of the potassa and the water. 862. If the solution is allowed to cool without the addition of any acid, a considerable quantity of a similar precipitate is gradually deposited, the solution of potassa not being able to dissolve so much when it is cold ; it is called Kermes mine- ral. 863. If the liquid is then filtered, and diluted sulphuric acid added, an additional precipitate is thrown down, more of a golden yellow colour than that of any of the other precipi- tates. It is usually termed the Golden Sulphuret of Anti- mony. 864. Tartrate of Antimony and Potassa, or Tartar Emetic, is prepared by boiling together equal weights of cream of tartar and oxide of antimony in four times their weight of water, filtering the solution afterwards, and evapo- rating the clear liquid till a pellicle appears on its surface. Both the cream of tartar and the oxide of antimony should be reduced to a fine powder before they are mixed, and the water made to boil before they are put in ; the boiling must be con- tinued at least for half an hour. 865. The protoxide obtained by precipitation from the muriate is perhaps preferable to that prepared in any of the other methods, as it requires little trouble to reduce it to a minute state of division ; the glass of antimony is not so easily 302 TARTRATE OF ANTIMONY AND POTASSA. reduced to an impalpable powder. I have tried the oxide prepar- ed, as Mr. Phillips directs, from the sulphate, frequently, and the process succeeds very well, if proper attention is paid to the pounding of the metallic antimony before digesting it in the acid, and the separation of the subsulphate from any me- tallic antimony that may not have been oxidated. 866. Though equal weights of the oxide and cream of tar- tar are recommended to be used, the whole of the oxide is not dissolved. One equivalent of cream of tartar, 198, which contains 18 parts, or two equivalents, of water, combines with three equivalents of the protoxide of antimony to form tartar emetic, and the crystals contain three equivalents of water ; the chemical equivalent of the crystallized tartrate must ac- cordingly be 363. Tartaric Acid (66x2) 132 Potassa 48 Protoxide of Antimony (52x3) 156 Water (9x3) 27 363 867- Tartar emetic is soluble in three times its weight of boiling water, and in fifteen parts of cold water ; its solution in water is decomposed by a number of acids, by alkalis and alkaline earths, and by a great many vegetable infusions and decoctions. 868. Add some nitric, sulphuric, or muriatic acid, to a strong solution of tartar emetic ; a copious precipitate is thrown down, consisting principally of cream of tartar. 869. To a similar solution, add a small quantity of a so- lution of potassa, soda, or ammonia. The alkali combines with the tartaric acid, and oxide of antimony is precipitated. 870. A precipitate is also thrown down by lime water, and by a solution of barytes ; it consists of oxide of antimony and tartrate of lime or barytes. 871- When a solution of the hydrosulphuret of ammonia or of any other soluble hydrosulphuret, is added to a solution of TARTRATE OF ANTIMONY AND POTASSA. 303 tartar emetic, or of any other salt of antimony, a copious pre- cipitate is thrown down, similar to what is obtained on adding sulphuric acid to the solution of the hydrosulphuret of antimony and potassa, the same reaction taking place between the sul- phureted hydrogen and the oxide of antimony that has been already described. 872. When too large a dose of this salt has been given, the best antidotes are sulphureted hydrogen water, solutions of the hydrosulphurets, and infusions of cinchona bark, galls or tea. In a case treated by Dr. Duncan, where a dose suf- ficient to have caused death had been taken, he gave a solu- tion of the hepar sulphuris with complete success. 873. The most delicate test of tartar emetic in solution is sulphureted hydrogen, which produces a very deep and cha- racteristic reddish brown precipitate even in solutions contain- ing a very minute quantity of this salt. The student should now transmit a stream of sulphureted hydrogen through so- lutions of tartar emetic of different strengths, and mixed with a number of other liquids, as milk, tea, porter, &c, till he becomes familiar with the appearance it presents. 874. In applying this test for the detection of antimony in mixed solutions where it may have been suspected to have been administered as a poison, Dr. Turner recommends the liquid to be boiled for a few minutes with a drachm or two of muriatic and tartaric acids before filtration ; the tartaric acid retaining the antimony in solution, and dissolving any of the oxide that may have been precipitated by an infusion of tea, bark, or galls, while the muriatic acid promotes the coa- gulation of any caseous matter that may be present. The metallic sulphuret is then to be dried and put into a small glass tube, about three inches long and a quarter of an inch in diameter, transmitting a stream of hydrogen gas slowly over it by connecting one end of the tube by a cork with an apparatus from which this gas is disengaged, and adapting a bent tube to the open end, the other extremity of which is made to dip under water. The tube must be heated by a spirit lamp at the part where the sulphuret is placed, and great care must be taken not to apply the heat till the air of 304 ANTIMONY the apparatus has been completely expelled, to prevent an ex- plosion taking place. Towards the end of the process, the temperature ought to be increased to bright redness by direct- ing the flame of the lamp upon the part of the tube immedi- ately below the sulphuret with the blow-pipe. 875. By this process the sulphuret is completely decom- posed, the hydrogen combining with the sulphur and forming sulphureted hydrogen, while the metallic antimony is melted, and forms a film upon the internal surface of the glass, or collects in minute globules. A light green glass tube should always be preferred, containing no lead, and being less easily softened. 876. Throw some tartar emetic upon some red hot cinders ; the tartaric acid will be completely decomposed, and the car- bon combining with part of the oxygen of the oxide, metallic antimony is set at liberty and appears in the form of minute globules. 877- By exposing a very small quantity to heat on charcoal before the flame of the blow-pipe, the metallic antimony is seen more distinctly, and white fumes of the oxide of antimo- ny are at the same time produced. 878. To prepare the Muuiate of Antimony, from which the protoxide is obtained according to the process of the Dub- lin College, two ounces of the sulphuret of antimony, (in fine powder,) are to be boiled for an hour in a glass vessel with eleven ounces of muriatic acid ; the solution always contains a slight excess of acid, and should be filtered when cold through a double linen cloth, or allowed to remain at rest till all the particles of sulphuret of antimony that have not been acted upon shall have been deposited. The Dublin College recom- mends a drachm of nitric acid to be mixed with the eleven ounces of muriatic acid to promote the oxidation of the anti- mony. The following diagram represents the action that takes place when the common muriatic acid is employed, every equivalent of sulphuret of antimony decomposing one of wa- ter, and a corresponding quantity of sulphureted hydrogen gas and oxide of antimony being formed, the latter remaining in combination with muriatic acid. ANTIMONY. 305 Before decomposition. After decomposition. f Hvdroo-en 1 V-"' 17 Sulphureted Hydrogen. Water . . i r\ b o >2 X i y f n !fiV' Sulphuret of J Sulphur JO Antimony | Antimony 44 Muriatic acid 37 — ^^. 89 flr uriate of Antimorty. 879. Chloride of antimony may be formed by pouring me- tallic antimony in fine powder into a bottle of chlorine gas. The best method of proceeding is to take a glass funnel and put a little paper round the tube, if it should not fit closely to the neck of the bottle containing the chlorine ; the antimony should then be thrown in, taking very small quantities at a time, and keeping the funnel sufficiently high to allow the metal to fall through as much of the chlorine as possible ; the antimony takes fire whenever it comes into contact with the chlorine. 880. Another method of preparing the chloride of antimony is by mixing it with three times its weight of the bichloride of mercury, and heating the mixture in a glass retort by a chauffer. A receiver must be fitted to the retort to condense the chloride that is distilled over, the metallic antimony combining with all the chlorine and the mercury being disengaged. It is usually called butter of antimony from its soft con- sistence, melts when exposed to a gentle heat, and assumes a crystalline texture on cooling. CHAP. VI. ARSENIC. Equivalent, 38. Specific gravity, 5-7 It is volatilized at 388. 881. Metallic arsenic may be prepared by exposing arseni- ous acid, or the white oxide of arsenic, as it is sometimes termed, 306 ARSENIC. to heat along with charcoal in fine powder, the oxygen of the acid uniting with the carbon, and forming carbonic acid, which escapes in the gaseous form, while the metal is at the jsame^time volatilized, and must be condensed in a close vessel, so that it may not be exposed to the action of the air. The best me- thod of conducting the process, when a small quantity is re- quired, is to mix the arsenious acid intimately with about twice its weight of the black flux, (597>) taking care to have them both perfectly dry, and expose the mixture to heat in a crucible, luting another over it in an inverted position, to col- lect the product, and leaving a small aperture for the escape of gas. The lower crucible should be placed in a sand bath furnace, and the upper one kept as cool as possible, and com- pletely out of the sand, that the arsenic may condense ; the pro- cess may be easily conducted with a small chauffer or furnace, taking care always to protect the upper crucible from the heat as much as possible. 882. Instead of using a crucible, the reduction may be ef- fected more easily, in operating with small quantities, by heat- ing the mixture in a glass tube, held in the flame of a spirit lamp. The tube should be perfectly dry, and the mixture placed in a small piece of paper, so as to slide readily down the tube, when held in an inclined position. The student should repeat this process frequently, in tubes of different sizes, from half an inch to a quarter of an inch in diameter, and from two to four inches long, using different quantities of the mixture, from the ^th f a grain to seven or eight grains, till he has become quite familiar with the appearance which the metallic arsenic presents. 883. The black flux is preferred to pure charcoal, as the pot- ash is supposed to prevent the arsenious acid from being volatil- ized, retaining it till it is decomposed by the charcoal which is mixed with it. When the crust is to be removed from the tube, a file should be drawn across it immediately below the part where the metallic arsenic has collected ; a slight pressure will then be sufficient to break off the lower part of the tube, and the metallic arsenic may be separated by a penknife. It has a steel gray colour, and is very brittle. A USE NIC. 307 884. Put a grain or two of metallic arsenic on a plate of iron, and expose it to heat ; the metallic arsenic is speedily vo- latilized, and produces a strong odour, similar to that of gar- lic. It sublimes at the temperature of 388. At a high tem- perature, it burns with a blue flame. Expose another portion to heat in a glass tube, and sublime it repeatedly from one part to another ; it attracts oxygen from the air, and is con- verted into arsenious acid. 885. Arsenious Acid is the most important compound of arsenic, and as it is frequently administered as a poison, the student should perform a number of experiments, to render himself familiar with the appearances which the different re- agents that have been recommended for detecting it pre- sent with arsenious acid when pure, or mixed with a num- ber of other substances, such as are usually found in the contents of the stomach, or are likely to have been given at the same time, either as an antidote, or for any other purpose. 888. Make a solution of arsenious acid, reducing it to fine powder, and boiling it for twenty minutes, in twenty-five or thirty parts of water. Sixteen parts of boiling water are said to dissolve one of arsenious acid, fths of which are deposited in the form of crystals as it cools, the rest remaining in solu- tion. When arsenious acid is merely mixed with water at na- tural temperatures, the solution does not contain more than 550 part of arsenious acid. 887- Mix equal weights of arsenious acid and subcarbonate of potassa, and boil the mixture in ten or twelve times its weight of water ; the arsenious acid unites with part of the potassa, and is very speedily dissolved, the arsenite of potassa being much more soluble than pure arsenious acid ; as the excess of alkali which the solution contains, (when the materials have been mixed in the above proportion,) must re-act upon many of the tests used for the detection of arsenious acid, the stu- dent must always bear in mind the precise composition of the fluid on which he is operating. 888. Mix a few drops of the saturated solution of arsenious acid, with seven or eight ounces of water, and pass a stream of sulphureted hydrogen through the liquid. The sulphur of the 308 ARSENIC. sulphureted hydrogen combines with the metallic arsenic, ren- dering the liquid of a yellow colour, but very faint, from the small quantity of materials present, and the hydrogen com- bines with the oxygen of the arsenious acid, forming water. Boil the liquid to expel the excess of sulphureted hydrogen, and then set it aside for several hours, when a minute quanti- ty of sulphuret of arsenic will be gradually deposited at the bottom. The sulphureted hydrogen may be prepared in a bottle with a bent tube fitted to it by a cork, the other extre- mity being introduced into a glass containing the solution. 889- Pass a stream of sulphureted hydrogen gas through a strong solution of arsenious acid in water ; observe the large quantity of the sulphuret of arsenic which is precipi- tated of a rich yellow colour ; place it on a filter, when no far- ther precipitation takes place, and after washing it several times with water, set it aside, that it may dry. 890. Transmit a stream of sulphureted hydrogen through a solution of the arsenite of potassa, taking care to have a slight excess of alkali. No precipitate is thrown down, nor does the gas appear to have any effect upon the liquid ; sulphureted hydrogen gas not being capable of decomposing arsenious acid when in combination with potassa. Add an excess of muriatic acid, and immediately the characteristic yellow coloured pre- cipitate will appear. 891- Put a few drops of the solution of arsenious acid in water into an ounce or two of water, and add a small quantity of a solution of the sulphate, nitrate, or acetate of copper. The liquid remains quite transparent and colourless, the arsenious acid not having so great an affinity for the oxide of copper, as the acid with which it is already combined. If a small quan- tity of an alkaline solution be now added, the alkali will unite with the acid of the salt employed, and remain in solution, and the arsenious acid combining with the oxide of copper, will form arsenite of copper, which is insoluble in water, and is precipitated of a grass green colour. 892. If the arsenious acid shall have been previously com- bined with potassa, the grass green precipitate appears imme- diately. Mix a drop or two of the solution of arsenite of ARSENIC. 309 potassa with a solution of the sulphate of copper in a glass of water. If a great excess of potassa be employed, the oxide of copper alone will be precipitated, and of a blue colour, very dif- ferent from the grass green precipitate of arsenite of copper. Add a solution of potassa to a solution of the sulphate of copper, and compare the colour of the precipitate with that of precipitated arsenite of copper. 893. Instead of using potassa to combine with the acid of the salt of copper, and allowing the arsenious acid to unite with the oxide, a solution of ammonia is frequently employed, and indeed it is to be preferred, as it is easy to combine the salt of copper with the exact quantity of ammonia that may be required for the precipitation of the arsenious acid ; the precipitate that is thrown down in this case, however, has not such a rich green colour as when potassa is used. 894. To prepare a solution of a salt of copper for this pur- pose, ammonia must be added to it till the precipitate that is thrown down at first is almost entirely redissolved, decanting the deep blue coloured liquid that is obtained in this manner, and keeping it in a bottle accurately closed, otherwise the ammonia will soon escape on exposure to the air. The am- monia unites with the acid of the salt, forming a salt which remains in solution, and the precipitate that is thrown down consists of oxide of copper, which is redissolved by the ammo- nia that is afterwards added. If more ammonia be used than is sufficient to redissolve the whole of the precipitated oxide, the solution will not give any precipitate with arsenious acid, the arsenite of copper being soluble in an excess of ammonia. 895. Add a few drops of a solution of the ammoniaco-nitrate of copper, prepared in the manner described, to a solution of ar- senious acid. Arsenite of copper will be immediately precipitat- ed. Diffuse the precipitate through the liquid, and divide it into two portions ; then add a little nitric acid to the ©ne and some ammonia to the other ; the precipitate in each will be re-dis- solved, the arsenite of copper being soluble both in nitric acid and ammonia. 896. Drop a solution of nitrate of silver into a solution of arsenious acid in distilled water. No precipitate is thrown 310 ARSENIC down, nitric acid having a stronger affinity for oxide of silver than arsenious acid ; if a little potassa be now added, it com- bines with the nitric acid and forms nitrate of potassa, which remains in solution, and the arsenious acid combining with the oxide forms a yellow coloured precipitate-— the arsenite of silver. 897- Add a solution of the nitrate of silver to a solution of phosphate of soda. Phosphate of silver is precipitated, of a yellow colour, and nitrate of soda remains in solution. The nitrate of silver cannot therefore be used as a test of the pre- sence of arsenious acid in solutions which may be suspected to contain phosphate of soda, as in liquids obtained from the stomachs of people supposed to have been poisoned by arsenic. 898. Prepare a solution of the ammoniaco-nitrate of silver by adding ammonia in small quantities at a time to a solution of the nitrate of silver, proceeding in the same manner as in the preparation of ammoniaco-nitrate of copper. Then drop a little into a very diluted solution of arsenious acid ; the ammonia remains in combination with the nitric acid, and the arsenious acid combining with the oxide gives the characteris- tic yellow coloured precipitate of arsenite of silver. 899- If the ammoniaco-nitrate be mixed with a solution of the phosphate of soda, a white precipitate will be thrown down instead of the yellow coloured precipitate which the nitrate of silver gives with a solution of this salt, and accordingly the ammoniaco-nitrate of silver is always preferred to the nitrate in testing any liquid for the presence of this poison. 900. Precipitate some arsenite of silver from a solution of arsenious acid by the ammoniaco-nitrate of silver, diffuse the precipitate through the liquid, divide it into two portions, and add ammonia to one and nitric acid to the other ; both will be redissolved, and accordingly great care must be taken to have no excess either of acid or alkali in using the nitrate of silver as a test of the presence of arsenious acid, otherwise no precipitate will appear, even though a considerable quantity of arsenious acid should exist in solution. 901. Mix some lime water with a small quantity of a solu- ARSENIC. 31 I tion of arsenious acid ; arsenite of lime is immediately pre- cipitated in the form of a white powder. Put a few drops of a solution of the bichromate of potassa into a solution of arsenious acid. The liquid will assume a rich pea-green colour after standing for some time ; heat a little of it by a spirit lamp, and the green colour will be developed immediately. The change of colour is owing to the arsenious acid attracting oxygen from part of the chromic acid and converting it into oxide of chrome. 902. Drop a little of the solution of bichromate of potassa in- to a solution of tartar emetic ; the liquid will assume the same green colour as in the preceding experiment, a circumstance that was pointed out by Mr. Lawrence Reid, and accordingly the bichromate of potassa cannot be used as a test of arsenic in any solution which may be suspected to contain tartar emetic. 903. The student having now made himself familiar with the appearances which the most important tests for the detec- tion of arsenious acid produce when mixed with a solution of this substance, and the precautions which he must take in applying them, should perform a number of experiments in the next place with liquids containing animal and vegetable matter, and mixed with arsenious acid both in solution and in the solid form, till he is able to detect it when the liquid upon which he is operating contains only a very minute portion of arsenious acid. He must recollect, however, that in operating with mixed liquids such as are generally met with in cases of poisoning by arsenious acid, where a variety of animal and vegetable principles are generally intimately blended together, and where various kinds of saline matter are also likely to be present, he cannot expect that he will be able to recognise it so easily as in a solution of pure arsenious acid in water. It is now admitted, indeed, that we cannot depend upon the appearances which any of the tests present when mixed with these liquids, as unequivocal indications of the presence of arsenious acid, as it has been proved that they often fail in producing the characteristic precipitates in such compound fluids, though arsenious acid may be present, and occasionally 312 AnsENie. they cause the same appearance as when arsenious acid is present, though the liquid does not contain any. A num- ber of important experiments and observations on this point are stated in the Edinburgh Medical and Surgical Journal for July 1824, in an excellent paper by Dr Christison. 904. Though considerable information may be obtained, by applying the tests we have described to mixed solutions, sus- pected to contain the poison, and when they all concur, in the indications which they give of arsenious acid, little doubt can be entertained of its presence ; still, in order to avoid every source of fallacy, it will be necessary to continue our investi- gation still farther, separating the matter that appears to have produced the characteristic precipitate with the arsenious acid, and extracting the metal itself, if any arsenious acid shall have been present. 905. For this purpose, Dr. Christison recommends sulphur- eted hydrogen to be employed, dispensing with the other tests ; the liquid should be boiled and filtered in the first place, and then acidulated with muriatic or acetic acid, to prevent any alkaline matter that may be present from interfering with the precipi- tation (890), passing a stream of sulphureted hydrogen through the liquid and continuing it at least for half an hour ; it is then to be boiled for a few minutes to expel any excess of sul- phureted hydrogen, and the precipitate collected on a filter, wash- ing it repeatedly with water, and drying it afterwards by heat- ing it to a temperature about 212. On mixing it intimately with about twice its weight of black flux, and exposing it to heat in a glass tube over a spirit lamp, the potassium in the black flux combines with the sulphur, and the metallic arsenic is su- blimed in the same manner as in the reduction of arsenious acid by the same substance. The size of the tube must be adapted to the quantity of the precipitate which has been pro- cured ; the most convenient size is about three or four inches long, and about a quarter of an inch in diameter; the mixture should not fill more than half an inch of the lower part of the tube, and smaller tubes should be used when only a very mi- nute quantity of matter has been precipitated. 906. If a crust of metallic arsenic should be obtained, its ARSENIC. 313 steel gray lustre, its brittleness, the facility with which it is volatilized, and the garlic odour that is at the same time pro- duced, will be sufficient to distinguish it from any other sub- stance ; if, however, there are only very indistinct appearances of the metallic arsenic, the following is the method that I have in general found most convenient for ascertaining if arsenic is present. The tube is to be exposed again to heat over the spirit lamp, till the matter that has been su- blimed is carried a little farther up the tube and completely separated from the black matter that remains at the bottom ; the lower part of the tube must then be broken off, drawing a file across it previously that it may be easily removed, and the upper part put into another glass tube and boiled for five or ten minutes with a little water to which a few drops of nitric acid have been added. If the tube be coated with any arsenious acid, it will be immediately dissolved, and if any metallic ar- senic should be present, it also will be converted into arseni- ous acid, attracting oxygen from the nitric acid and being dis- solved at the same time, so that the liquid may now be consi- dered as a solution of arsenious acid in water with a small quantity of nitric acid ; and accordingly, on neutralizing the ex- cess of acid by dropping ammonia into it through a test tube drawn out at the extremity over a spirit lamp, so as to repre- sent a small funnel terminating in a capillary tube, the am- moniaco-nitrates of copper and silver will produce the charac- teristic green and yellow precipitates. If they should give no precipitates, then we may conclude that the mixture which we have examined contains no arsenic. 907- Digest a quarter of a grain of metallic arsenic in a test tube with a drachm of water and two or three drops of nitric acid ; neutralize the solution with ammonia in the manner de- scribed in the preceding paragraph, then put a number of drops of the solution on different parts of a sheet of white pa- per, and touch them with glass rods dipped in the different solutions used for the detection of arsenious acid ; the charac- teristic colour will appear in each ; care must be taken not to dip the same glass rods into different solutions, without pre- viously removing any liquid that may be still adhering to them. 314 ARSENIC 908. The indications given by the different tests are free from every source of fallacy when they are added to solutions prepared in this manner, as the arsenious acid is thus removed from all the animal and vegetable matter that might have in- terfered with their action in the mixed liquid. Infusions of astringent matter and some other vegetable and animal sub- stances, which are frequently met with in the liquid contents of the stomach have been shown by Dr. Christison to be ca- pable of retaining in solution the precipitates that arsenious acid gives with the ammoniaco-nitrates of copper and silver. Tartaric and acetic acids appear to be solvents in some cases, arsenite of silver being soluble in both. 909. Orfila has proposed to use chlorine, and Mr. Phillips animal charcoal to decolorize mixed fluids suspected to contain arsenious acid, and allow the usual tests to be applied in the liquid way without previously removing the arsenious acid and subjecting it to some process of reduction ; biit though both may occasionally be used with advantage, it will be better to adopt the method we have already mentioned. It appears also, from the experiments of Dr. Christison and Dr. Paris, that charcoal is capable of precipitating arsenious acid from its solution in water. 910. If a quantity of solid powder be obtained among the contents of the stomach, the following experiments may be made. 911. Expose a small quantity to heat on a thin plate of copper or on the blade of a knife over a spirit lamp ; it will be completely volatilized if it be arsenious acid. Mix another portion with twice its weight of black flux, and if any crust be obtained which has the character of metallic arsenic, it will be unnecessary to proceed any farther. Should the appearance of the crust be unsatisfactory, it must be treated in the manner described in 906, and if no indication of arsenious acid be then obtained, we may conclude that the white powder does not contain any. 912. Arsenic Acid is prepared by digesting metallic ar- senic or arsenious acid in strong nitric acid mixed with a little ARSENIC. 315 muriatic acid, evaporating the solution afterwards to dryness in a glass or earthen vessel. 913. If equal parts of nitre and arsenious acid are fused in a crucible, the nitric acid is completely decomposed, part of the arsenious acid attracting oxygen from it and being con- verted into arsenic acid, which remains in combination with the potassa, while the rest is volatilized. The arseniate of po- tassa is speedily dissolved on digesting it in water ; it gives a brick red precipitate with a solution of the nitrate of silver. Mix half a grain of arsenious acid with an equal weight of nitre, fuse it slowly in a platina spoon over a spirit lamp, then put the spoon into a test tube with a little water, and add a drop of a solution of the nitrate of silver to the solution of arseniate of potassa obtained in this manner, when the charac- teristic brick coloured precipitate will be thrown down. 914. Arsenureted Hydrogen is a gaseous compound of arsenic and hydrogen gas, which may be prepared by digest- ing an alloy of tin and arsenic in common liquid muriatic acid ; a portion of water is decomposed, the tin uniting with its oxygen and forming oxide of tin which remains in solution combined with the muriatic acid, while the hydrogen unites with the arsenic and escapes in a gaseous form. It is ex- tremely deleterious, and has already proved fatal to M. Gehlen, a German chemist ; it will be better therefore for the beginner to pass over this process. 915. Another compound of arsenic and hydrogen has been discovered by Davy ; it exists in the solid form, but its exact composition has not been ascertained. 916. The Protosulphuret of Arsenic, or Realgar, may be obtained by mixing arsenious acid with f ths of its weight of sulphur, and exposing the mixture to heat in a co- vered crucible till it is fused ; part of the sulphur unites with the oxygen and the rest with the metallic arsenic forming the deep red coloured mass that remains. It is sublimed when exposed to heat in a retort, and condenses in the neck in the form of a very rich red coloured powder. 917- The Yellow Sulphuret of Arsenic, or Orpi- ment, contains more sulphur than the red, and may be pre- 316 TIN. pared in the same manner from a mixture of equal weights of sulphur and arsenious acid, or by transmitting sulphureted hydrogen through a solution of this substance. 918. Another sulphuret of arsenic has been described which contains more sulphur than either of the preceding compounds^ it is obtained by transmitting a stream of sulphureted hydro- gen through a solution of arsenic acid. 919- Throw some metallic arsenic reduced to powder into a bottle of chlorine gas. The arsenic immediately takes fire, and chloride of arsenic is formed ; it has not been ap- plied to any use. 920. Sulphureted hydrogen water has been recommended by Orfila as the best antidote to arsenious acid, the yellow sul- phuret of arsenic that is formed being comparatively inert ; it is not free from danger however, and has sometimes produced death, though it is certainly much less virulent in its action than arsenious acid. Lime water is also recommended, to prevent the solution of the poison, but the great object in all cases must be to excite vomiting as speedily as possible ; and to give large quantities of mucilaginous liquids to involve and. suspend the poison till it has been rejected. CHAP. VII. TIN. Equivalent 58. Specific gravity 7-3. It melts at the tem- perature of 442. 921. Mix 1200 grains of the oxide of tin with 100 grains of charcoal, and expose the mixture to a good heat in a cruci- ble placed in a furnace for twenty minutes. The carbon unites with the oxygen of the oxide, and metallic tin will be found in the crucible. 922. When tin is required in a minute state of division, it TIN. 317 may be procured by melting it in a ladle, and stirring it con- stantly with an iron pestle as it cools. An iron mortar does better than a ladle, and is more easily kept in a fixed position. It has also been prepared by shaking melted tin in an iron box well rubbed over with chalk in the inside. The fine powder obtained by any of these methods should be separated from the larger particles by passing it through a sieve ; these may be melted again, and reduced to powder as before. 923. Melt some tin in an iron ladle and expose it freely to the air, a crust soon gathers on its surface, composed princi- pally of the protoxide of tin. 924. The Protoxide of Tin may be obtained by adding a solution of potassa to a solution of newly prepared muriate of tin, taking care to avoid an excess of alkali, the protoxide being soluble in a solution of potassa. . 925. Take another portion of tin and expose it to a full white heat in a crucible placed in a furnace, and resting about an inch and a half above the branders. It soon takes fire, burning with a white flame, and combining with a larger por- tion of oxygen, so that it is converted into peroxide of tin. 926'. Put half an ounce of nitric acid into a deep glass, add a drachm of water to it, and pour in two or three hundred grains of the powder of tin ; the metal attracts oxygen both from the acid and the water, and hydrogen and nitrogen gases meeting in a nascent state unite and form a portion of ammo- nia ; this combines with a portion of nitric acid which is not decomposed, forming nitrate of ammonia, which explains the appearance of the white fumes that are mixed with the large quantity of ruddy vapours of nitrous acid that are at the same time disengaged. Considerable heat is also produced, and the tin is left in the form of a bulky white powder- — the per- oxide of TIN. 927. Take a common tin plate, (which is in reality a plate of iron coated with tin,) about a foot square, hold it over a chauifer or before the fire with a pair of pincers till a drop of water allowed to fall upon its surface begins to boil immedi- ately, and then wash one of its sides with a mixture of four parts by measure of water, one of nitric, and one of muriatic 318 MURIATE OF TIN. acid. Its surface will immediately assume a beautiful crys- talline appearance, and by heating the plate at particular parts with the blow-pipe, or exposing different parts to higher and lower temperatures, a great variety of figures may be produc- ed, which will be seen better on washing it with water. The moiree inetallique, or crystallized tin plate as it is some- times termed, of which a great number of hardware articles are now made, is prepared in this manner, and the various colours which it is made to assume are communicated by giving it a thin coating of different coloured varnishes. The tin plates used for this purpose should have a good coating of metallic tin, otherwise most of the tin will be removed during the preparation of the moiree, and nothing will remain but the iron below, which has a very dark colour. 928- None of the salts of tin are of any importance except the Muriate of Tin, which may be prepared by mixing tin with liquid muriatic acid, and exposing it to heat in a Flo- rence flask ; part of the tin takes oxygen from a portion of water which is decomposed and forms oxide of tin which re- mains in combination with the muriatic acid, while another portion of the metal combines with the hydrogen, forming the fetid gas that is disengaged ; it may be collected in jars over a pneumatic trough by heating the mixture in a retort, and burns with a blue flame. By exposing the solution of the muriate to the open air, it soon attracts oxygen, and permu- riate of tin is obtained in solution. A similar solution may be procured more speedily by adding tin in small quantities at a time, to two parts of nitric mixed with one of muriatic acid. 929. Tin is detected easily in solution when in the form of a protoxide, giving a deep purple precipitate with the chloride of gold, commonly called the purple of Cassius ; an orange coloured precipitate with a solution of the chloride of platina ; a black precipitate with a solution of the bichloride of mer- cury ; and a dark brown precipitate with alkaline hydrosul- phurets. The bichloride of mercury gives a white precipitate, and the alkaline hydrosulphurets a golden coloured precipi- tate with a solution of the peroxide. UISMUTU. 319 CHAP. VIII. BISMUTH. Equivalent 72. Specific gravity 9-850. It melts at 480. 930. Bismuth exists native, and the specimens that occur in commerce have in general been melted solely for the pur- pose of separating the metal from the stony matter with which it is usually mixed when it is first procured. 931. Melt some bismuth in a crucible, and expose it freely to the open air. A ! crust soon collects on its surface, com- posed principally of the oxide of bismuth. Expose it to a high temperature in a furnace ; the bismuth is volatilized, and burns with a bluish white flame. 932. Melt some bismuth in a crucible, and when the surface becomes solid while the greater part of the metal is still melted within, make a small hole in the middle and invert the cru- cible till all the liquid metal has been poured out. On break- ing into the hollow mass that is left, its internal surface will be found studded with crystals of metallic bismuth. Another method of proceeding is to melt the bismuth in an iron ladle, cooling the bottom by immersing it in cold water, before breaking the crust above, and taking care not to allow any wa- ter to fall upon the melted metal, lest some of it should be thrown about with explosive violence. 933. Reduce half an ounce of bismuth to powder, and dis- solve it with a gentle heat in six drachms by measure of nitric acid diluted with half its bulk of water. Part of the acid is decomposed, affording oxygen to the metal which unites with the rest of the acid, and nitric oxide gas is disengaged. Crystals of the nitrate of bismuth are deposited on concentra- ting the solution. 934. Throw half of the solution obtained in the manner directed in the preceding paragraph, into twelve ounces of water ; a copious precipitate will be thrown down consisting of 320 MANGANESE. Subnitrate of Bismuth, (often called Oxide of Bismuth), and a supernitrate of bismuth will remain in solution. The diagram explains the reaction more particularly, supposing a binitrate to be formed. Before decomposition. After decomposition. Nitric Acid 54 ; — ^-188 Binitrate of Bismuth. f Nitric Acid 54- Nitrate of Bismuth | Qx Bigmuth g0 .. f Nitric Acid 54- Nitrate of Bismuth j Qx Bismuth80 Nitrate of Bismuth/ JJitric Acid 54- ( Ox. Bismuth 80 _^^214.Subnitrate of Bismuth. 935. Pour a little of the supernatant liquid into a glass, and transmit a stream of sulphureted hydrogen through it ; the dark coloured precipitate of sulphuret of bismuth that immediately appears proves that there is still some bismuth in solution. To the other half of the solution of the nitrate of bismuth, add a solution of the tartrate of potassa as long as any pre- cipitation takes place ; nitrate of potash remains in solution, and Tartrate of Bismuth is precipitated, formerly known by the name of pearl white, and much employed as a cos- metic. CHAP. IX. MANGANESE. Equivalent 28. Specific gravity 6.8. 936. Metallic manganese is not easily obtained, as it has a very great affinity for oxygen ; it has been procured in small grains by exposing the peroxide mixed with charcoal to the greatest heat of a smith's forge. The sides of the crucible must be lined previously with a stiff paste made of charcoal, otherwise part of the oxide will combine with the earthy mat- 6 OXIDES OF MANGANESE. 321 ter and fuse into a glass after part of its oxygen has been expelled. 937- The Protoxide of Manoanese may be obtain- ed by mixing any of the other oxides of manganese inti- mately with charcoal, and exposing the mixture to a white heat in a furnace ; the carbon combines with part of the oxy- gen, and protoxide of manganese is left with the excess of charcoal. 938. It may be obtained also by passing a stream of hy- drogen gas over any of the oxides of manganese at a bright red heat, placing them in a gun-barrel or porcelain tube made to traverse a furnace in the usual manner. One end of the tube must be connected with an apparatus from which a con- stant stream of hydrogen gas is disengaged, and the other with a tube dipping under water to carry off the superabun- dant hydrogen. The excess of oxygen in the oxide unites with part of the hydrogen, and is converted into water, the protoxide remaining in the tube in the form of a green powder. 939- The Deutoxide of Manganese may be obtained by exposing the peroxide to heat in an iron bottle ; oxygen gas is disengaged, and the deutoxide remains of a dark brown colour. See 19- It is regarded as a compound of one equi- valent of the protoxide and one of the peroxide of manganese. 940. The Red Oxide of Manganese may be obtained by exposing the deutoxide to a white heat in an open vessel, when an additional quantity of oxygen is disengaged. It may be considered as a compound of one equivalent of the per- oxide with two of the protoxide of manganese. 941. The Peroxide of Manganese occurs abundantly in the mineral kingdom, and is the compound from which all the other preparations of manganese are usually obtained. Its use in the preparation of oxygen, chlorine, and in several other processes has been already described. 942. Manganeseous Acid, which contains still more oxy- gen than the peroxide of Manganese, may be obtained easily in combination with potassa by mixing one part of the per- Y 322 MANGANESE.— MINERAL CHAMELEON. oxide of manganese intimately with three or four of nitre, and exposing the mixture to a bright red heat for half an hour in a crucible. The mixture should not fill more than a third of the crucible. In this process, the nitric acid of the nitre is completely decomposed, part of its oxygen combining with the peroxide of manganese and converting it into manganeseous acid, which remains in combination with the potassa, and the rest is disengaged along with the nitrogen. The manganesite of po- tassa prepared in this manner has a very green colour, and must be kept in close vessels, as it usually contains an excess of alkali, which renders it very deliquescent. It is usually called the Mineral Chameleon, from the different colours which its solution presents when diluted with different quanti- ties of water, or exposed freely to the air for some time. 943. Reduce ten or twelve grains of the mineral chameleon to powder, put it into a deep glass vessel, and pour in a little water ; it will immediately become of a very deep green co- lour, dissolving the manganesite of potassa, and by pouring in an additional quantity of water, it will pass through various shades of green, blue, and purple, and at last become of a red colour. These changes arise from the manganeseous acid at- tracting oxygen from the water, and being converted into Man- ganesic Acid, which has a deep red colour when dissolved in water, and communicates the same tint to this liquid when combined with potassa. 944. The peroxide of manganese being usually mixed with oxide of iron, which is dissolved along with the oxide of man- ganese when digested in sulphuric or muriatic acid, the follow- ing process, pointed out by Mr. Faraday, will be found con- venient when a pure solution of manganese is required. Mix one part of muriate of ammonia in fine powder with twice its weight of the peroxide of manganese, and expose the mixture to a dull red heat in a crucible for a quarter of an hour, the am- monia is disengaged, the oxide loses oxygen, and the chlorine of the muriatic acid combines with metallic manganese alone, having a much greater affinity for this metal at a red heat than for iron ; as a great excess of peroxide is used, no chloride CHROME. 323 of iron is formed, and a solution of muriate of manganese is obtained on digesting the remaining mass in water, and separ- ating the iron and excess of manganese by nitration. 945. Drop a little of the solution of ferrocyanate of potassa into the solution of muriate of manganese prepared in this man- ner ; a white precipitate is thrown down immediately — the fer- rocyanate of manganese : add a little of the same solution to a diluted solution of the muriate or sulphate of manganese pre- pared by digesting the peroxide as it is usually procured in muriatic or sulphuric acids ; a precipitate immediately appears, but it has a rich blue colour, from the large quantity of ferro- cyanate of iron that is thrown down with the ferrocyanate of manganese. 946. A solution of the Muriate or Manganese, for esti- mating the strength of a solution of the chloride of lime may be obtained by evaporating to dryness the solution that re- mains after the preparation of chlorine by common muriatic acid and peroxide of manganese, digesting it afterwards in water and filtering the solution. CHAP. X. CHROME. Equivalent 28. Specific gravity 6 ? 947« It is not easy to procure chrome in the metallic form, as it has a great affinity for oxygen at all temperatures. Small quantities have been obtained from a mixture of the oxide with charcoal, exposing it to heat in the manner directed for the preparation of metallic manganese (936). 948. Protoxide of Chrome is easily prepared by expos- ing the chromate of mercury to a strong red heat for half an hour in a crucible ; the oxide of mercury is decomposed and volatilized, and the chromic acid parting with a portion of its oxygen is converted into oxide of chrome, which has a fine 324 CHROME. green colour. The solutions of its soluble salts have the same colour. 949- Chromic Acid may be obtained in solution by di- gesting 126 parts of dry chromate of barytes with 49 parts of sulphuric acid diluted with seven or eight times its bulk of water. The sulphuric acid combines with the barytes, form- ing the insoluble sulphate which remains mixed with the li- quid, and the chromic acid is dissolved, imparting to it a very deep ruby colour. By concentrating the solution, it may be obtained in small crystals. It parts with a portion of oxygen when exposed to a red heat, and even when its solution in water is boiled or left in contact for some time with acids and many substances that have an affinity for oxygen, as alcohol and other liquids containing a considerable quantity of inflam- mable matter, the carbonaceous matter or hydrogen uniting with the excess of oxygen in the chromic acid, and the green oxide being retained in solution by the other aeid that is mix- ed with it. 950. Chromic acid can combine with fluoric and muriatic acids, producing gases of a rich red colour. Chloro-chro- mic Acid is easily prepared by mixing intimately one part of common salt with two and a half of the chromate of lead, and exposing the mixture to heat in a glass retort containing about an equal quantity of sulphuric acid. Sulphates of soda and lead are left in the retort, and the mixed acids unite together and are disengaged in the gaseous form. It has a rich red co- lour, and may be collected in glass jars over the mercurial trough. The experiment may be made easily on the small scale with a few grains of the mixture in a test tube. 951. Fluochromic Acid Gas is not so easily prepared, from the facility with which it is decomposed by glass vessels, the fluoric acid uniting with the silica, while chromic acid is set at liberty ; it is prepared by heating a mixture of fluor spar, chromate of lead, and sulphuric acid, the fluoric and chromic acids combining as they are separated, and sulphates of lime and of lead remaining. A leaden retort should be used when it is prepared, similar to what has been recommended for the preparation of fluoric acid. SALTS OF CHIIOME. 325 SALTS OF CHIIOME. 962. The salts of chrome are divided into two classes, viz. those in which the protoxide acts the part of a salifiable base, and those where some other salifiable base is combined with chromic acid ; the latter are the most important. 953. Chroma te or Potassa is prepared from a mixture of nitre and the common chrome iron ore, usually termed chromate of iron, but which is composed of the oxides of chrome and iron mixed with earthy matter. The ore must be reduced to a very fine powder, and mixed with an equal weight of nitre, exposing the mixture to a bright red heat in a crucible for about half an hour, when a small quantity of materials, as one or two ounces, is used. The nitric acid is completely decomposed, converting the oxide of chrome into chromic acid, and the protoxide of iron into peroxide. The chromic acid unites with the potassa, forming chromate of potassa, and on boiling what remains in the crucible in water and filtering through paper, a clear solution of the chromate of potassa is procured, and the iron and earthy matter re^ main on the filter. The free potassa which the solution air- ways contains must then be neutralized by nitric acid, con- centrating it afterwards by evaporation that the nitrate of potassa may crystallize, after which, the remaining liquid will deposit crystals of the chromate of potassa when allowed to evaporate spontaneously. They have a lemon-yellow colour, and are soluble in twice their weight of cold water and in a, much smaller quantity of boiling water, 954. The Bichromate of Potassa is prepared by adding sulphuric acid to a solution of the neutral chromate, sulphate of potassa being formed, while the chromic acid set at liberty unites with another portion of the chromate of potassa which is not decomposed. The solution at the same time assumes a deep red colour, and red crystals of the bichromate are pro- cured by spontaneous evaporation. They are less soluble than the crystals of the neutral chromate of potassa, requiring about ten parts of cold water for their solution. 326 fcALTS OF CHllOME. Add a solution of the subcarbonate of potassa to a solution of the bichromate of potassa till the excess of acid is neutra- lized ; the liquid will become of a yellow colour. Then drop in sulphuric acid that it may combine with the potash which has been added, when the bichromate of potassa will be form- ed, the red colour returning again. 955. Fill a small crucible half full of the bichromate of potassa, invert a larger crucible over it, and expose it for half an hour to a bright red heat in a crucible placed in a furnace. The excess of acid will be decomposed, being re- solved into oxygen gas and protoxide of chrome, which re- mains mixed with the neutral chromate of potassa that is left. Reduce the green mass in the crucible (which has a glittering appearance) to powder, boil it for a short time with five or six times its weight of water, and filter the liquid through paper. The green oxide of chrome will remain upon the fil- ter, and the liquid which passes through will have a deep yellow colour, the water having dissolved the chromate of potassa. 956. Chromate or Barytes is precipitated when a solu- tion of the chromate of potassa is added to a solution of the muriate of barytes, muriate of potassa remaining in solution. 957. Chromate of Lead is prepared by adding a solu- tion of the chromate or bichromate of potassa to a solution of the acetate of lead, as long as any precipitation takes place. It has a fine yellow colour, and is the pigment well known by the name of Chrome Yellow. 958. Boil a solution of the chromate of potassa with car- bonate of lead reduced to a very fine powder; Subchromate of Lead is obtained, which has a very rich red colour. 959. Chromate of Mercury, which has an orange red colour, is easily prepared by adding a solution of the chro- mate of potassa to a solution of the nitrate of the protoxide of mercury as long as any precipitation takes place ; nitrate of potassa remains in solution. COBALT. 32/ CHAP XL COBALT, &c. Equivalent 26. Specific gravity 8.5. It fuses at a tem^ perature a little below the melting point of iron. 960. Cobalt may be prepared from zaffre, an impure oxide of this metal, the residuum of one of the principal ores of cobalt, after exposing it to heat to drive off the sulphur and arsenic which is usually combined with it. The cobalt of commerce generally contains small portions of arsenic, iron, nickel, and copper. 961. Several processes have been proposed for the prepara- tion of metallic cobalt from zaffre. Any arsenious acid may be removed by dissolving it in dilute nitric acid and passing a stream of sulphureted hydrogen through the solution, which will precipitate sulphuret of arsenic ; a plate of iron will re- move any copper ; and on filtering the liquid, evaporating it to dryness, and digesting the dry mass in water of ammonia, nothing is dissolved but the oxides of cobalt and nickel. Ex- pel any excess of ammonia from the clear liquid by heat, add a solution of potassa cautiously, which will precipitate the nickel; filter the liquid immediately and boil it, when the oxide of cobalt is separated, from which metallic cobalt may be obtained by exposing it to a strong heat along with char- coal in a crucible, (Dr. Ure.) It is attracted by the magnet. 962. Metallic cobalt is not much employed in the arts ; the impure oxide fused with silica and potassa gives a fine blue coloured glass, which has received the name of Smalt. 963. The solution of the Muriate of Cobalt is used as a sympathetic ink, characters traced with it on paper leaving no mark when dry, if the solution be not very strong, and appearing of a blue colour when it is exposed to a gentle heat, which fades again as it cools, or if it be put into water, 328 MERCUIIY. The solution is obtained easily by digesting cobalt in one part of muriatic acid mixed with half its bulk of nitric acid, and two or three parts of water, evaporating the liquid obtained in this manner to dryness, and then dissolving the residuum in water. 964. If a quantity of common salt, equal in weight to the cobalt employed, be added to the solution, traces made with it on paper will have a very beautiful green colour, instead of the blue appearance they usually present. All the other metals belonging to this class are compara- tively very rare, and as it is not likely that any of them will be made the subject of experiment by the beginner, it will be unnecessary to take any notice of them in this place. ORDER V— METALS WHOSE OXIDES CAN BF 4 REDUCED BY EXPOSURE TO HEAT WITH, OUT INFLAMMABLE MATTER. CHAP I. MERCURY. Equivalent 200. Specific gravity 13.5. // becomes solid at — 39-5, and is volatilized at 650. 965. Mix four or five ounces of the native or prepared sul- phuret of mercury with an equal weight of lime or iron filings, throwing an additional quantity of lime or iron over the mix- ture, and expose it for an hour or two to a dull red heat in an iron retort, or in an iron bottle with a bent gun-barrel or other iron tube adapted to it. The sulphur combines with the iron or the calcium of the lime, and metallic mercury is dis- engaged, being slowly volatilized and condensing in drops in 4 PREPARATION OF MKUCURY FROM THE SULPHURET. 329 the iron tube, the open extremity of which should be put into water. 966. This process may be imitated on a still smaller scale by mixing twenty or thirty grains of the sulphuret with as much iron filings, and exposing them to heat in a glass tube, holding the part containing the mixture in a horizontal position over a spirit lamp, or placing it on the top of a chauffer, and sur- rounding it with small pieces of charcoal. I find a chauffer with a piece cut out at the top of one of the sides extremely convenient for performing a number of experiments like this on the small scale, the tube resting on the edge and being sup- ported within the chauffer by the fuel and without by a brick or a piece of wood. The temperature can be easily regulated ; if the mixture is to be exposed only to a moderate heat, it will be unnecessary to cover it with charcoal, but if it must be sub- jected to a high temperature, then the tube shoiild be coated in the manner described in 220, completely covered with a mixture of small cinders and pieces of charcoal, and a chimney put over it (15), which may be prolonged if necessary by another tube of nearly the same diameter fitted to the top. The size of the glass tube must correspond with the quantity of materials used ; it need not be larger than the tube employed for the reduction of arsenic, or it may be an inch in diameter, and ten or twelve inches long. The mixture should not occupy more than one or two inches of the sealed end of the largest size of tubes ; and should always be placed in an inclined po- sition, so that any watery vapour which may be disengaged and condensed on the side may not fall back upon the hot part of the tube, otherwise it will be broken. 967- When a very small quantity of materials is used, the metallic globules are not seen very distinctly at first, but if the matter that is sublimed be taken out and rubbed gently on a dry plate with a piece of paper, the metallic globules will become apparent. 968. When the materials are not well mixed, or the heat incautiously applied, a good deal of the sulphuret is sublimed without decomposition, and is very apt to obstruct the tube, condensing principally a little way beyond the part to which 330 FUKE MEKCURY. the heat is applied, and as serious accidents might take place from the accumulation of vapour while there is no opening by which it may escape, the student cannot be too cautious in attending to this circumstance in making experiments of this kind, especially in narrow glass tubes ; when the temperature however is sufficiently high to soften the glass, no danger need be apprehended, as the glass will then be slowly blown out by the vapour within till some part of it gives way and al- lows it to escape. An iron tube closed at one end by welding, as a piece of a gun barrel, or an earthen tube closed with some clay or plas- ter of Paris, may be used instead of a tube made of glass. 969- In this process, supposing iron alone to be used, it combines with the sulphur of the sulphuret of mercury, form- ing sulphuret of iron, while metallic mercury is disengaged. The following diagram gives the most probable view of the atomic proportions in which the materials act upon one ano- ther, though I am not aware that this lias been minutely ex- amined. Before decomposition. After decomposition. ( Mercury 200 20 ° Mercury. Bisulphuretofj Sul hur 16 Mercury j ^^ jg^^ Iron • • • 28 — ^^^^^ 44 Sulphuret of Iron. Iron .... 28 -^ 44 Sulphuret of Iron. 970. Metallic mercury being frequently adulterated with a considerable quantity of other metals, such as lead, tin, zinc, and bismuth, it will be necessary to state the characters by which it may be distinguished when pure, and the method of purifying it from any foreign matter with which it may be adulterated. 971- Pure mercury has a bright white metallic lustre, and appears extremely mobile when poured from one vessel to ano- ther or thrown upon a level surface, the globules in the latter case being round, having a very high edge, and being easily divided into a number of smaller globules, all of which appear equally mobile. It does not tarnish on exposure to the air, no impure MEiteunw 331 film collects on its surface when shaken in a bottle, and when exposed to heat it is completely volatilized. 972. When mercury has acquired a crust of oxide from the action of acid fumes, or a quantity of dust collected on its sur- face, it is purified easily by folding a piece of writing paper into a cone, leaving a small aperture at the bottom about the size of the point of a pin, or a little larger, and pouring the mercury into this cone, supported in a glass funnel ; the pure mercury will pass through in a very slender stream, and the greater portion of the dust and oxide remains on the sides of the cone. A small quantity of mercury always remains at the bottom of the cone ; it should not be forced through and mixed with the rest, but set aside by itself or with other portions of impure mercury. When a large quantity of mercury is to be filtered in this manner, fresh portions should be poured into the filter from time to time, before what has already been put in ceases to drop, otherwise part of the dust or oxide will be forced through along with the mercury. The vessel into which the mercury is received should be perfectly dry, otherwise it may not appear so pure as it really is, moisture preventing the globules that first fall through from coalescing so easily toge- ther. 973. If the mercury be adulterated with any of the metals we have mentioned, it has not that bright metallic appearance which pure mercury always presents ; a film soon collects on its surface, and another reappears whenever it is removed. It is not nearly so mobile as pure mercury ; when a small quan- tity is thrown on a flat surface, it does not divide so readily in- to globules, and they are not so round, but have an irregular appearance, and their edges instead of being high and promi- nent are nearly on a level with the surface itself; while, when it is very impure, it presents more the appearance of a soft solid. To separate these, the usual process is to distil it in an iron bottle with a bent iron tube adapted to it. The Edinburgh College directs the mercury to be mixed with a sixth part of its weight of iron filings, and the mercury is obtained in a purer state in this manner than when it is distilled without any 332 METHOD OF PURIFYING MERCURY. admixture. The effect of the iron in this process is not very well understood ; it has no great affinity for any of the other metals with which mercury is usually adulterated ; perhaps it acts principally by allowing the mercury to be converted more easily into vapour, and in smaller quantities at a time, lessen- ing the risk of any being carried over mechanically during the ebullition, as we know that water and other liquids can be made to boil several degrees below their usual boiling point by introducing some pieces of wire or other solid matter, and that thus a constant stream of vapour may be made to arise from them instead of the liquid entering only occasionally into a state of violent ebullition, and then ceasing for a short time to give any more vapour till it is produced with the same vio- lence as before. Advantage is taken of this fact in the distil- lation of sulphuric acid, and it is probable, that in the distilla- tion of impure mercury, the other metals which are mixed with it may have a tendency to pass over when the distillation is conducted without the assistance of the iron filings. In all cases the distillation should be conducted with a very gentle heat, and the materials should never fill more than a third of the retort or bottle in which it is carried on ; the ex- tremity of the tube should be made to dip under water, and taken out when the last portions of mercury have passed over. For distilling large quantities of mercury, one of the iron bot- tles in which it is sold will do extremely well, fitting a bent gun barrel accurately to it by grinding ; it may be heated by an open fire, placing it on a piece of brick or on one or two bars of iron laid across each other, to raise it an inch or two above the grating, surrounding it about half way up with burn- ing fuel, (a mixture of charcoal and cinders should be used) and taking care to moderate the heat whenever it begins to boil. Mr. Faraday recommends copper filings to be mixed with the iron filings. 974. The iron filings being generally mixed with a little oil, this is decomposed during the distillation, and a small quan- tity of an empyreumatic oil passes over with the metallic mer- cury and condenses in the water, often preventing the globules from uniting together, so that they assume the appearance of PROTOXIDE OF MERCURY. 333 a soft solid. When tins takes place, the water should be poured off, and a small quantity of a solution of caustic po- tassa poured over them ; this removes the oil, and on washing them with water, they readily unite, after which they should be passed through a paper filter, (972-) 975. Though mercury is obtained sufficiently pure for ordi- nary experiments by distilling it cautiously in the manner that has been described, it still frequently contains a small portion of zinc ; this may be removed by shaking it with diluted nitric acid in a bottle, and then pouring both into a plate, where they may be left together for a few days, after which the mercury must be washed and filtered as before ; the acid may be diluted with ten or twelve parts of water. 976. When only a small quantity of mercury is to be purified, as an ounce or a pound, Dr. Priestley's method will be found most convenient. It consists merely in shaking the mercury briskly in a bottle capable of containing four or five times as much, blowing into it occasionally with bellows to re- new the air, and continuing till a black matter gathers together, which may be easily separated from most of the metallic mer- cury by a paper funnel, after which it should be returned again, and the operation repeated till no more oxidation takes place, when the mercury will become extremely clean and mobile, the brightening taking place all at once as the last portions of the other metals are oxidated. 977- Protoxide of Mercury, called also Black or Ash- Coloured Oxide of Mercury, is prepared most easily by mixing chloride of mercury with a solution of potassa in a mortar, rubbing them together for a quarter of an hour or twenty mi- nutes, and taking care to have an excess of alkali that the decomposition may be complete. For every 236 grains of the chloride employed, 100 grains of fused potassa may be taken and dissolved in two or three ounces of water, allowing the solution to stand till it becomes clear, when it may be decanted for use. Muriate of potash remains in solution, and the protoxide may be separated by filtration, washing it with cold water, and keeping it in a dark place, as it soon begins to be decomposed on exposure either to heat or light, one 331' PROTOXIDE OF MERCURY. portion losing oxygen which combines with another, so that small quantities of the metallic mercury and peroxide of mer- cury are then found to be mixed with the protoxide. 978. Instead of using a solution of potassa, the Edinburgh and London Colleges prepare their protoxide from the chloride of mercury (formerly called muriate of mercury) by lime water. The same reaction takes places as when potassa is used ; half an ounce of the chloride may be used with every five pounds of lime water, boiling them together for a quarter of an hour after rubbing them together in a mortar, mixing a small quantity of the lime water at first with the dry pow- der that it may be easily moistened. Muriate of lime remains in solution, and the oxide must be washed on a filter with dis- tilled water ; the following diagram shows more precisely the nature of the reaction. Before decomposition. After decomposition. 28 Lime . . . 28 -z&? 65 Muriate of Lime. . „ r ( Hydrogen 1 -""" / 9 Water \ „•' & „ ( Oxygen . 8 -v-- 236 Chloride of j Chlorine 36 '^v Mercury j Mercury 200 ~^208 Protoxide of Mercury. 979. The protoxide of mercury may be obtained also by adding a solution of potassa or soda to a solution of the nitrate of mercury, the alkali uniting with the acid while the oxide is precipitated. 980. By triturating metallic mercury with manna, sugar, lard, and a number of other vegetable and animal substances, the metallic globules disappear, and a mass is obtained of a dark colour ; many consider the metallic mercury to be merely reduced to a very minute state of division in this manner, while others affirm that it is at the same time oxidated. 981. When the protoxide of mercury is quite pure, it has a dark colour, and is completely dissolved by acetic acid, but is quite insoluble in muriatic acid. 982. Peroxide of Mercury maybe obtained by dissolv- ing three parts of metallic mercury in four of diluted nitrous acid, (made by mixing equal weights of the strong acid pre- pared in the manner described in 139 and water,) evaporating PEROXIDE OF MEItCURY. 335 the solution to dryness, and then reducing it to powder and exposing it to a stronger heat in an evaporating bason over a good chauffer till it assumes a deep red colour. It should be covered by a flat glass plate which allows the progress of the decomposition to be observed ; a large quantity of ruddy fumes are disengaged, which cease to come when all the pow- der has acquired a dark colour, after which it must be re- moved from the fire, otherwise it will be resolved into metallic mercury and oxygen gas. As it cools, it assumes a bright red colour, and the lowest portion is usually obtained in the form of brilliant scales, this appearance depending probably on the pressure of the superincumbent mass, as it is always seen more distinctly the larger the quantity of peroxide pre- pared. 983. In this process, the metallic mercury decomposes part of the nitric acid and is converted into peroxide of mercury, which combines with the rest of the acid, so that the dry mass which is obtained in the first stage of the process is a nitrate of the peroxide of mercury. The nitric acid is afterwards almost entirely expelled, being resolved by the heat into nitrous acid and oxygen gas. The quantity of nitric acid that remains in combination with the oxide is extremely small. Another method of preparing peroxide of mercury consists in exposing metallic mercury to air at a temperature between 500 and 600, when it combines slowly with oxygen and is converted into red scales ; these were formerly called Precipi- tate per se, and are larger than those procured by the decom- position of the nitrate ; they have not the same shining ap- pearance, however, and not containing any nitric acid, they are not so acrid. As upwards of a fortnight is required to prepare a few grains of peroxide in this manner, it is a process that is seldom resorted to. 984. Peroxide of mercury is frequently adulterated with oxide of lead, which may be easily detected by exposing it to heat on charcoal before the blow-pipe. If the peroxide be pure, it will be completely dissipated, oxygen gas being dis- engaged and metallic mercury volatilized ; if, however, any oxide of lead should have been mixed with it, a globule of 33G tests or MEncuiiY. metallic lead will remain on the charcoal. If it he purchased in the form of scales, it is generally obtained perfectly pure, and any foreign admixture could easily he detected by bare inspection, but when it has been reduced to powder, it may then be suspected to have been adulterated. 985. There are several tests by which mercury may be detected in solution. The most delicate, perhaps, is that pro- posed by Mr. Sylvester. A drop of the liquid suspected to contain it is to be placed on a piece of gold leaf, or any piece of solid gold, and the point of a nail or penknife or of any small piece of iron or zinc placed in contact with the moisten- ed surface ; if any mercury be present, the gold will immedi- ately become white where it is touched by the other metal, uniting with the mercury and forming a solid amalgam, which retains its white colour after the fluid has been wiped off. 986. Put a piece of copper into a solution of any salt of mercury ; part of the copper will be dissolved, combining with the oxygen of the oxide of mercury and the acid with which it was previously united, while an equivalent quantity of metallic mercury will be precipitated. Add a solution of potassa to a solution of a salt of mercury ; oxide of mercury will be immediately precipitated. If the mercury in the liquid shall have been in the form of a pro- toxide, the precipitate will be of a dark colour, but when it contains the peroxide alone, the precipitate has sometimes a reddish colour but is generally yellow, the peroxide disengag- ed combining with a portion of water and forming a hydrate. Collect the precipitate on a filter, dry it, and expose it to heat at the bottom of a small test tube over a spirit lamp, when globules of metallic mercury will be seen. Put a small quantity of a solution of a salt of the protoxide of mercury into a glass, and fill it up with lime water ; pro- toxide of mercury will be immediately thrown down and give a dark colour to the liquid. Into another glass, put a similar quantity of a solution of a salt of the peroxide of mercury, and add lime water as be- fore ; the solution will become of a yellow colour from the separation of peroxide of mercury in combination with water. SALTS OF MERCURY. 337 987- Add some hydrosulphuret of ammonia or pass a stream of sulphureted hydrogen gas through a diluted solution of a mer- curial salt, a copious black precipitate will be thrown down of sulphuret of mercury, probably in combination with water. 988. Add a solution of the muriate of tin (muriate of the protoxide) to a solution of a salt of the protoxide of mercury ; a copious ash-grey coloured precipitate will immediately appear, consisting principally of metallic mercury, the oxide of tin combining with the oxygen with which the mercury was pre- viously united, and passing to a higher state of oxidation. 989. A solution of the ferrocyanate of potassa gives a white precipitate with salts of mercury ; muriatic acid and solutions of the muriates give a white precipitate with salts of the pro- toxide, composed of the chloride of mercury. 990. All the salts of mercury are completely decomposed or volatilized by exposure to a dull red heat. SALTS OF MERCURY ; CHLORIDES, IODIDES, AND SULPHURETS OF MERCURY, &C. 991. Nitrate of Mercury, (protonitrate), may be ob- tained by digesting metallic mercury in one and a half times its weight of diluted nitric acid, (prepared by mixing one part of acid with fovir of water), allowing the mixture to eva- porate spontaneously, and adding a small portion of metallic mercury if the quantity employed should have been com- pletely dissolved. The crystals that are deposited are not completely dissolved by water unless they contain a slight excess of acid. 992. Perkitrate of Mercury is obtained by heating metallic mercury in an excess of strong nitric acid, a large quantity of nitric oxide gas being disengaged ; it is deposited in transparent crystals as the liquid cools ; if thrown into a large quantity of water, it is decomposed, a nitrate of the peroxide with an excess of acid remaining in solution, while a subnitrate is precipitated, composed of two equivalents of the peroxide and one of nitric acid. 338 PERSULPHATE OF MERCURY. 993. In preparing nitrate of mercury for different purposes, great attention must be paid to the strength of the acid em- ployed, the temperature to which the mixture is exposed, and the relative proportions in which the acid and the metal are mixed together, as all these circumstances have an important influence upon the oxidation of the mercury and the nature of the resulting salt. If the acid be strong and a larger quan- tity employed than is necessary to dissolve the mercury, and if the solution be assisted by heat, the mercury always at- tracts two equivalents of oxygen and a pernitrate of mercury is obtained ; but when the acid is diluted with three or four parts of water, the solution allowed to go on at natural tem- peratures, or assisted only by a very gentle heat, and more mercury is used than the acid can dissolve, a protoxide will be obtained, which unites with a smaller quantity of acid. 994. Persulphate of Mercury is prepared by boiling two parts of metallic mercury to dryness with two and a half of sulphuric acid, exposing the mixture to heat in a glass vessel over a common fire. On the small scale, an ounce of mercury with the proper quantity of acid may be boiled to dryness over a common fire or good chauffer, taking care to avoid the fumes that are evolved, not to boil the mixture violently, otherwise a quantity of the sulphate will be thrown out, and to remove it from the fire whenever it is dry. It is obtained in the form of a white crystalline powder when well prepared, perfectly dry, and not deliquescing on exposure to the air ; the following diagram represents its composition and the theory of its formation, one portion of the sulphuric acid affording oxygen to the mercury, while sulphurous acid is dis- engaged, while the greater part of the rest unites with the oxide, the excess being dissipated along with the sulphurous acid, and producing very pungent suffocating fumes. Before decomposition. After decomposition. (Sulph. Acid 32 32 Sulphurous Acid. Sulphuric Acid | Qxygen g, _' ( Sulpll. Acid 32— \~ • 32 Sulphurous Acid. Sulphuric Acid -i r\ o 1 ( Oxygen 8 Sulphuric Acid 40 ■ Sulphuric Acid 40 - Mercury 200 — :^k gflf, l'crsulph. of Mercury. SUBSULPHATE OF MERCURY. Four equivalents, accordingly, of sulphuric acid are requir- ed to convert one equivalent of mercury into persulphate, two of these affording oxygen to the metal, while the other two combine with this oxide as it is formed. 995. Mix 296 grains of the persulphate of mercury with 200 of metallic mercury, and rub them intimately together in a mortar ; the metallic mercury divides the oxygen and acid in the persulphate with the 200 parts of mercury which it already contains, and 496 parts of Sulphate of the Protox- ide of Mercury are obtained, the different materials arranging themselves in the manner represented in the annexed diagram. Before decomposition. After decomposition. 200 Mercury . . 200 -;.;--:? = -'24,8 Sulphate of Mercury. Oxygen 8'".-'''' Sulph. Acid 40"'' 296 Persulph of Mercury Oxygen Sulph. Acid 40- Mercury 200 1^*248 Sulphate of Mercury. 996. Throw half an ounce or an ounce of the persulphate of mercury, heated to the temperature of 400 or 50O, into five or six pounds of boiling water, in a large glass flask or earthen bason. A yellow coloured precipitate will be immediate- ly thrown down, composed of one equivalent of sulphuric acid and one of the peroxide of mercury, another portion of the peroxide remaining in solution with an excess of acid. I am not aware that the latter has been very accurately examined ; the annexed diagram gives a precise view of the nature of the reaction, supposing the salt that remains in solution to contain only one more equivalent of acid than the persulphate ; the yellow coloured precipitate is usually termed Subsul- phate of Mercury, or Turpeth Mineral. Before decomposition. After decomposition. 296 Persul- ( Sul P h - Acid 40 --;,~; r 336- Supersulph. of Mer. phate of-< Sulph. Acid 40 """,.-'''/ Mercury ( p er0 X. of Mer. 216 -''''/ 296 Persul- i Sulph. Acid 40 / phate of J Sulph. Acid 40^^^ Mercury ^ p erQX of Mef 216__^=^256 Subsulph. of Mer. It should be washed repeatedly with water on a filter, and then set aside to dry. 340 SULPHURETS OF MERCURY. 997- Sulphuret (Protosulphuret) of Mercury may be obtained by passing a stream of sulphureted hydrogen through a diluted solution of, the protonitrate of mercury, or through water in which chloride of mercury reduced to fine powder is suspended. The following diagram shows the reac- tion that takes place when the latter is employed. Before decomposition. After decomposition. Sulphureted f Hydrogen 1 >- 37 Muriatic Acid. Hydrogen j Sulphur 16. Chloride of J Chlorine 36. Mercury j Mercury 200 __ ^ 216 Sulphuret of Mercury, The sulphuret is precipitated in the form of a black powder and muriatic acid remains in solution. When exposed to heat, metallic mercury and bisulphuret of mercury are obtained. 998. The Black Sulphuret of Mercury of the differ- ent colleges, which is prepared by rubbing together equal weights of mercury and sulphur till the globules disappear, and frequently called Ethiops Mineral, is a mixture of sul- phur and bisulphuret of mercury. (Brande.) 999. There are several methods of preparing Bisulphuret of Mercury. The easiest method of obtaining it in a pure state is by passing a stream of sulphureted hydrogen gas through a solution of the nitrate of the peroxide of mercury, or through a solution of the bichloride, as long as any preci- pitation takes place ; collecting the black precipitate on a filter, and subliming it afterwards in a tube or any other apparatus that may be found convenient, when it will assume a crystalline form, and become of a purplish red colour, which is seen more distinctly on reducing it to powder on a white ground ; the annexed diagram represents the theory of the action when a solution of the bichloride of mercury is employed : Before decomposition. Hydrogen Hydrogen 2 Equivalents of sulphur- eted Hydro- j Sulphur gen, 34. { Su l phur l Equivalent f Chlorine ififfl Chlorine 272. I Mercury After decomposition. 37 Muriatic Acid. 37 Muriatic Acid. 232 Bisulpluuct of Mercury. CARBONATE OF ME11CURY. 341 The whole of the mercury is precipitated in this process, and if the solution contained a considerable quantity of the bichloride, the muriatic acid that remains in the liquid will impart a deep red colour to the blue infusion of cabbage, and decompose carbonate of lime rapidly with effervescence. 1000. The common method of preparing bisulphuret of mer- cury or Artificial Cinnabar, is by melting 40 parts of sulphur in an iron cup over a chauffer, and adding 200 of metallic mercury, stirring constantly with an iron rod till the mixture has assumed a uniform appearance, and taking care to apply only a moderate heat, to prevent it from taking fire ; the mix- ture is extremely apt to take fire when the heat is too great, and the iron cup must be covered when this takes place, re- moving the chauffer for a short time. It must afterwards be reduced to powder, and sublimed in a close vessel. Eight parts more of sulphur are recommended to be taken than is absolutely necessary to convert the metallic mercury into bi- sulphuret, to make up for a portion of sulphur which is always lost ; the bisulphuret is always obtained, however, of a finer colour when there is an excess of mercury, metallic mercury being sublimed along with the bisulphuret ; the sublimation should be conducted slowly, the bisulphuret condensing in a crystalline cake having a radiated appearance. 1001. Bisulphuret of mercury is sometimes adulterated with red lead or chalk, either of which may be easily detected by exposure to heat on an iron plate, the pure bisulphuret being volatilized, while the chalk or oxide of lead remains, the latter losing a portion of its oxygen and being converted into yellow oxide of lead if the temperature has been sufficiently high. When the bisulphuret of mercury is reduced to a fine powder, it presents a very beautiful colour, and is well known in this form by the name of vermilion. 1002. Carbonate or Mercury may be obtained by add- ing a solution of the nitrate of mercury to a solution of the subcarbonate of potassa as long as any precipitaton takes place, nitrate of potassa remaining in solution while the mer- curial carbonate is precipitated ; the reaction that takes place is represented in the diagram. PERCARBOUATE OF MERCURY Before decomposition. Subcarbonate f Potassa ... 48 -- ©f Potassa | Carbonic Acid 22 Nitrate of { Nitric Acid... 54 Mercury | Protox. Merc. 208 After decomposition. y 102 Nitrate of Potassa. 230 Carbonate of Mercury. 1003. Percarbonate of Mercury is formed when a solu- tion of the subcarbonate of potassa is added to a solution of the pernitrate or bichloride of mercury ; the following diagrams show the nature of the reaction when bichloride of mercury is employed. One equivalent of the bichloride reacting on two of water is converted into peroxide of mercury and muriatic acid. 9 Water x 2 272 Bichloride of Mercury Hydrogen... 1 Hydrogen... 1 Oxygen 8 Oxygen 8 Chlorine 36 r Chlorine 36 {Mercury... 200 37 Muriatic Acid. 37 Muriatic Acid. 216 Peroxide of Mercury. Again, the muriatic acid and peroxide of mercury reacting on two equivalents of the subcarbonate of potassa, percarbo- nate of mercury is precipitated, and muriate of potassa remains in solution. TO Subcarbonate . of Potassa x 2 Potassa 48 -/ 85 Muriate of Potas. Potassa 48— — ■/--? 85 Muriate of Potas. Carbonic Acid.. 22 Carbonic Acid.. 22 Muriatic Acid ( Muriatic Acid .. 37/) and Peroxide < Muriatic Acid .. S] / of Mercury . { Perox. Mercury 216 \ 260 Percarb. of Merc. The subcarbonate of potassa, bichloride of mercury, and water probably react on one another whenever the solutions are mixed together, but the reaction will be more easily under- stood by the two diagrams than if it had been represented in one. FULMINATING MERCURY. 343 1004. Expose a small quantity of any of the precipitated carbonates of mercury to heat in a tube over a spirit lamp ; carbonic acid and oxygen gases will be disengaged, and small globules of metallic mercury soon appear a little above the part of the tube that is held over the flame. 1005. Acetate of Mercury is easily prepared according to the process of the Edinburgh College. Three parts of mercury are to be dissolved in four and a half of their diluted nitrous acid, (composed of equal weights of water and the strong fuming acid obtained in the manner described in 136), and the solution must be added to an equal weight of the acetate of potassa dissolved in thirty-two times its weight of water ; nitrate of potassa remains in solution, and acetate of mercury is deposited in small crystals as the liquid cools. Before decomposition. After decomposition. Acetate of f Potassa 48 ;/ 1° 2 Nitrate of Potassa. Potassa. ( Acetic Acid 50\ ,,-'' Nitrate of f Nitric Acid 54 v - > \ s _ Mercury j Oxide of Merc. 208 _\„ 258 Acetate of Mercury. In preparing the nitrate, the usual precautions must be taken to prevent the formation of peroxide of mercury. 1006. Peracetate of Mercury may be obtained by di- gesting the peroxide of mercury in acetic acid till it will not dissolve any more. 1007- The method of preparing Bicyanide of Mercury has been already described in 341. 1008. Cyanate of Mercury, or Fulminating Mercury? as it is usually termed, is prepared by mixing pernitrate of mercury dissolved in an excess of acid with alcohol. For this purpose, 100 grains of mercury may be digested with an ounce and a half by measure of strong nitric acid in a Florence flask till they are dissolved, and the solution, after it has been allowed to cool a little, added in small quantities at a time to two ounces of alcohol in another flask, exposing it afterwards to a very gentle heat over a chauffer till white fumes begin to appear. If the action should proceed very 344 CHLORIDE OF MERCURY violently, it must be moderated by adding a little alcohol ; and if it do not commence soon after the mixture is exposed to heat, a few drops of strong nitric acid poured in by a pipette, will soon cause the white fumes to appear. These fumes are extremely heavy, and may be poured from one vessel to ano- ther, or through a funnel ; their composition has not been ascertained. When the reaction has ceased, a quantity of a white crystalline powder is found to have been deposited, which is the fulminating mercury ; it must be washed on a filter with water, and allowed to dry by exposure to the open air. It should never be put into a bottle with a ground stopper, as it detonates by friction and percussion, but should be merely folded in a piece of paper, and kept in a wide-mouthed phial with a cork fitting loosely to it. The cyanic acid in this compound is formed by the decomposition of part of the nitric acid and the alcohol, the nitrogen being derived from the acid and the carbon from the alcohol. 1009- Place ten or twelve grains of fulminating mercury on a block of iron and touch it with a red hot cinder ; it will imme- diately detonate with a quick but not a sharp or loud report, and a bluish white flame, its elements being separated from one another. It may be detonated also by striking it with a hammer, and is the basis of the detonating mixture employed for the anti-corrosive percussion caps. 1010. If two or three grains be put into a dry Florence flask to which a brass cap and stop-cock have been fitted, and exposed to heat over a spirit lamp after the air has been exhausted as completely as possible, a flash of light will soon be perceived, but no report heard, and metallic mercury is deposited on the in- side of the flask. If the air of the apparatus be not exhausted, a loud explosion will take place, and the flask be blown to pieces. Seven grains of fulminating mercury were found sufficient to produce the same effect when the flask had been exhausted of air as completely as possible. 1011. Chloride of Mercury or Calomel, formerly called Submuriate or Mild Muriate of Mercury, may be easily prepared from the bichloride of mercury, the sulphate of mercury, or the nitrate of mercury, CIILOH1DL OF MEKCUHY. 345 1012. When the bichloride is employed for this purpose, every equivalent (272) must be mixed with an equivalent of mer- cury, rubbing them together in a Wedgwood's mortar, and continuing till the metallic globules of the metal completely disappear, and the mixture is converted into an ash-grey co- loured powder. It should be turned over from time to time with a spatula, when it appears to cake together at the bottom of the mortar, and great care must be taken to avoid the small particles of the bichloride that are carried up at first when it is reduced to powder, as they are extremely deleterious ; a few drops of water added to the mixture prevent these particles from being disengaged, and facilitate the action of the mer- cury on the bichloride. 1013. The grey-coloured mass must then be sublimed in a cucurbit, a glass vessel with a capital that is accurately fitted to it by grinding ; a small tube proceeding from it carries off any watery vapour that may be condensed. It is heated most conveniently by placing it in a sand bath, the lower part of the body of the cucurbit being covered by sand, and the calomel condensing in the upper part as it is sublimed ; the mixture should never occupy more than a third of the cucurbit. 1014. On a smaller scale, the sublimation may be easily effected in a glass tube, proceeding in the manner directed in 966 ; the diagram explains the theory of the action. Before decomposition. After decomposition. f Mercury .. .200 ~^ 236 Chloride of Mercury. 272 Bichloride? Chlorine'. 1 .. 36 ° fMerCUry lchlorine... 36 200 Mercury 200 "/>■<, 236 Chloride of Mercury. 1015. A small quantity of the bichloride of mercury is al- ways formed during the decomposition, and a little metallic mercury also appears generally between the sides of the cu- curbit and the crystalline cake of calomel. By repeating the sublimation it is usually obtained in a pure state, or the me- tallic mercury may be separated mechanically, and the bi- 346 CHLORIDE OF MERCU1U". chloride removed by reducing the cake to a fine powder and digesting it with water, which dissolves the bichloride but has no action on calomel. The London College directs a solution of the muriate of ammonia to be used for this purpose instead of water, the bichloride being much more soluble in it than in water. 1016. If calomel be suspected to contain bichloride of mer- cury, a small quantity should be boiled in distilled water for a few minutes, or in a solution of the muriate of ammonia, and the liquid filtered. If any bichloride of mercury be mixed with the calomel, it will be dissolved, and on adding a solution of potassa to the clear liquid, peroxide of mercury will be preci- pitated of an orange colour, if water alone has been employed, but the precipitate will be of a white colour if the calomel has been boiled in a solution of the muriate of ammonia. 1017. Chloride of mercury is decomposed by solutions of potassa, soda, and ammonia, sulphureted hydrogen water, and solutions of the hydro-sulphurets. 1018. The next method of preparing chloride of mercury is from a mixture of the sulphate of mercury (sulphate of the protoxide, See 995) and common salt, (chloride of sodium). The materials must be intimately mixed together, and exposed to heat in the manner we have already described in 1013. Every 248 parts of the sulphate (one equivalent) require 60 parts of chloride of sodium (one equivalent), sulphate of soda remaining in the bottom of the cucurbit, while chloride of mer- cury is sublimed as before. The diagram gives a more precise view of the nature of the reaction : Before decomposition. After decomposition. ( 208 ProtOX. f MerC.200 v 236 Chloride of Merc. 24 o 8 fS*1 of Mercury. \ Oxyg. 8^ t Sulphuric Acid 40 « 60 Chloride f Chlorine 36 ofSodium ( Sodium 24 ^ 72 Sulphate of Soda. 308 308 308 CHLOIUDK OF MKItCURY. 34'7 1019- The last method of preparing chloride of mercury which we shall describe is by precipitation from the nitrate, (nitrate of the protoxide). For this purpose, a solution of the nitrate of mercury, prepared with the usual precautions (993) must be added to a solution of chloride of sodium in 50 or 60 parts of water ; chloride of mercury will be immediately precipitated, and nitrate of soda remain in the liquid. The quantity of chloride of sodium recommended to be dissolved in the water is equal in weight to the mercury employed in the preparation of the nitrate ; a much smaller quantity would be sufficient, if the nitrate could be easily procured free from pernitrate, 262 parts of the nitrate reacting on 60 of the chloride ; a small quantity of pernitrate of mercury is always formed, however, if the solution be not kept for a long time in contact with an excess of mercury, and every equivalent of the pernitrate reacts on 120 of the chloride, producing bi- chloride of mercury instead of calomel. The diagram repre- sents the reaction that takes place between the nitrate of mercury and the chloride of sodium. Before decomposition. After decomposition. 60 Chlo. f Sodium 24 ~pr 86 Nitrate of Soda. of Sodium ( Chlorine 36 \ ,-'/'' C Nitric Acid 54 -'V S25M 2°8 P™tox. f Oxyg. 8 / \ (.of Mercury ( Merc.200 ^ 236 Chloride of Merc. The chloride is precipitated in the form of a white powder, and must be washed and filtered with pure water. 1020. The following diagram gives a view of the reaction that would take place between the mercurial salt and the chloride, supposing the whole of the mercury to be converted into pernitrate, (composed of two equivalents of nitric acid and one of the peroxide ?) and a sufficient quantity of chloride of sodium to be in solution. 34-8 BICHLORIDE OF MERCURr / Mercury... 200 324PernUrateoflO X ygen 8 Mercury . < Nitric Acid 54 J Oxygen.... 8 V. Nitric Acid 54 ( Chlorine 36 1 20 Chloride of ) Chlorine 36 Sodiuru=60x2 j Sodium 24 ' Sodium 24 444 444 272 Bichloride of Mercury. 86 Nitiate of Soda. 86 Nitrate of Soda. 444 1021. The student will now perceive the great importance of attending to the quantity of oxygen and acid combined with the metal, as in the present instance, nothing would be obtained but bichloride of mercury and nitrate of soda instead of chloride of mercury and nitrate of soda, if the mercury were converted into a pernitrate instead of a nitrate of the pro- toxide ; and, moreover, no precipitate would take place, bi- chloride of mercury being soluble in water. He will likewise remark, that though chloride of mercury is prepared from a mixture of chloride of sodium and sulphate of mercury, bi- chloride of mercury is formed when persulphate of mercury is used. 1022. Bichloride of Mercury, or Corrosive Sublimate, formerly called Muriate or Oxymuriate of Mercury, is usual- ly obtained by exposing a mixture of one equivalent of the persulphate of mercury (296) to heat along with two equiva- lents (120) of chloride of sodium, and conducting the process in the manner described for the preparation of calomel from the sulphate of the protoxide. The fumes and watery vapour that are disengaged are loaded with bichloride of mercury, and must be carefully avoided, as they arc extremely delete- rious ; the sand bath should be placed under a chimney, or taken out into the open air ; several students have been se- verely affected while preparing the bichloride by themselves from not attending to this circumstance. BICHLORIDE OF MERCURY. 349 The following diagram shows the nature of the reaction that takes place. Before decomposition. ! Mercury 200 Oxygen. ;• 8 Sulphuric Acid 40 Oxygen 8 Sulphuric Acid 40 ( Chlorine 36 120 Chloride of J Chlorine 36 Sodium=60x2 "S Sodium 24 vSodium 24 416 416 After decomposition. 272 Bichloride of Merc, ^ 72 Sulphate of Soda, —^- 72 Sulphate of Soda. 416 The bichloride is sublimed and condenses in a crystalline cake lined with a beautiful net-work of prismatic crystals, the sulphate of soda remaining at the bottom, as in the preparation of calomel from the sulphate of the protoxide. The heat should be moderate and not more than is required to volatil- ize the bichloride slowly, to prevent as much of it as possible from being carried off in the form of a vapour ; towards the end of the process, the heat may be increased for a short time. 1023. Instead of conducting the sublimation of these differ- ent compounds in a glass cucurbit, an earthen bottle, or com- mon glass bottle coated with clay and sand may be used, filling about a third of it with the mixture to be sublimed, the product condensing in the upper part which must be kept out of the sand. 1024. Pure bichloride of mercury is completely volatilized by heat, and is easily distinguished from calomel by its solu- bility it water, and the yellow precipitate which it gives with lime water. 1025. The student should now make a number of experiments with a solution of the bichloride of mercury and solutions of the alkalis, alkaline earths, sulphureted hydrogen water, solu- tions of the hydrosulphurets, of chromate of potash, acetate 350 IODIDES OF MERCURY. of lead, and several astringent vegetable solutions — by all of which it is decomposed. Copper and some other metals pre- cipitate metallic mercury. 1026. Muriate of Ammonia and Mercury, the Hy- drargyrum Frecipitatum Album of the London College, and the Sal Alembroth of the older chemists, may be prepared by adding a solution of subcarbonate of potassa to a solution of the bichloride of mercury in muriate of ammonia as long as any precipitation takes place ; the following are the proportions recommended, Four ounces of the muriate of ammonia are to be dissolved in four or five pints of distilled water, and six ounces of the bichloride of mercury must then be dissolved in this solution, separating the white precipitate that is thrown down on adding the solution of subcarbonate of potassa by filtration, and washing it with water on the filter. 1027. In this process, the bichloride maybe considered to have been converted into muriatic acid and peroxide of mercury by reacting on two equivalents of water (1003), and the potassa of the subcarbonate uniting with the acid, the peroxide is preci- pitated in combination with the muriate of ammonia. 1028. Iodide of Mercury may be obtained by adding a solution of the hydriodate of potassa to a solution of the nitrate of mercury (protonitrate), being immediately precipitated in the form of a yellow powder ; the potassa combines with the nitric acid of the nitrate, the hydriodic acid and oxide of mer- cury mutually decomposing each other, and forming water and iodide of mercury. 1029. Peiiiodide of Mercury is formed and precipitated of a red colour when a solution of pernitrate of mercury is add- ed to a solution of hydriodate of potassa, two equivalents of the latter being decomposed by one of the pernitrate, and the usual reaction taking place between the acid and the oxide. 1030. It may also be obtained very easily by heating iodine with rather more than twice its weight of mercury in a glass tube ; a brisk ebullition takes place, and periodide of mercury is sublimed, condensing on the sides of the tube, and assuming a very rich crimson colour as it cools. An excess of mercury METHOD OF OBTAINING PUKE SILVER. 351 should be used as the periodide is not then liable to be mixed with any uncombined iodine, which would prevent its bright colour from being so distinctly seen. CHAP. II. SILVER. Equivalent 110. Specific gravity 10.5. A strong heat is required to fuse it, and by a very high temperature it may he dissipated in vapour. 1031. Pure silver is usually obtained on the small scale by precipitation from a solution of the nitrate, introducing a piece of metallic copper for this purpose, which unites with the oxygen and acid of the nitrate, while the silver is precipitated in small crystalline grains, which must be washed on a filter with distilled water. 1032. It may be precipitated in the metallic form by mer- cury also, exposing the silver that is obtained in this manner to heat afterwards in a crucible till it is melted,, that the mer» cury which is mixed with it may be expelled. This process is seldom resorted to, however, except for the purpose of showing the arborescent form in which the silver is separated by the mercury. It is in this manner that the Arbor Dianae as it has been termed is usually prepared ; 50 grains of the fused nitrate of silver dissolved in two or two and a half ounces of water, and put into a glass with 1 00 grains of mercury, do very well for this purpose, the crystals of silver being deposited above the mercury and rising slowly in the liquid, part of it being slowly dissolved, as it combines with the oxygen and acid previously in combination with the silver. 1033. Silver being frequently alloyed with a small quantity of copper, we may now state the processes by which they may be separated. The one usually followed consists in exposing 352 PURE SILVER BY CUPELLATION. the alloy to the action of the air at a high temperature along with several times its weight of lead, the copper and the lead being oxidated and fused, while metallic silver remains. For this purpose, the alloy must be placed on a cupel, a small po- rous crucible made of bone ashes, and exposed to heat in the muffle of the cupellation furnace (790) ; or some bone ashes may be spread on a tile or flat- earthen dish, if a cupel cannot be procured, in the manner described in 789. The quantity of lead required depends on the richness of the alloy ; if it con- tain about a tenth part of copper, which is usually the case, six or seven times its weight of lead will be found quite suffi- cient ; but if more copper be present, it will be necessary to use a larger quantity of lead. 1034. The use of the lead in this process is to form a fusible compound with the copper during the oxidation of both metals, which is speedily absorbed by the bone ashes, while the pure silver remains above. If too small a quantity of lead be employed, a brown crust gathers on its surface which is not fused, and prevents the farther oxidation of the rest of the lead and cop- per. The usual precautions must be taken in bringing the muffle to a proper temperature, and the process is known to be completed by the fulguration or brightening as it is termed, which is seen when the last portions of lead and copper are oxidated and removed. 1035. On taking out the cupel, the silver is seen in the form of a metallic globule of a rich white colour and great lustre ; the fused oxides give the cupel a very dark appearance where they have been absorbed, deeper in proportion to the quantity of copper which the alloy may have contained. The appearance which it presents should be compared by the beginner with the result of the process described in 789, where pure lead is di- rected to be exposed to heat on bone ashes till it is oxidated. The experiment may be made with a few grains of the al- loy, or a much larger quantity may be employed. 1036. Another process for separating silver from copper may be adopted where there is no cupellation furnace. Digest the alloy with three parts of nitric acid diluted with twice its bulk of water in a glass flask or evaporating bason till it is 5 SILVER. 353 dissolved, and pour the liquid into a dilute solution of chloride of sodium, containing a quantity of the chloride equal to about twice the weight of the alloy. The nitrates of copper and silver react upon the chloride of sodium, nitrate of soda and chloride or muriate of copper being formed and remaining in solution, while chloride of silver is precipitated. The diagram represents the reaction that takes place between the nitrate of silver and chloride of sodium. Before decomposition. After decomposition. 60 Chloride of f Sodium 24 — — ;;f' 86 Nitrate of Soda. Sodium | Chlorine 36' ( Nitric Acid 54 ^^SrM ^^ 8 t Silver 110 -X H6 Chloride of Silver. 1 037- The chloride of silver is then to be washed on a filter with water till the liquid that passes through gives no traces of copper, mixed with its own weight of dry subcarbonate of potassa, and put into a bottle or any kind of a glass vessel, which must be placed in a crucible and surrounded with sand, exposing it to a strong heat in a furnace. The potassium of part of the subcarbonate unites with the chlorine of the chlo- ride forming chloride of potassium, which fuses along with the rest of the subcarbonate, the glass of the bottle or tube containing the mixture and part of the sand forming a well defined ball of glass, and on breaking into it the metallic silver will be found generally in a solid mass at the lower part of the ball. 1038. It is generally stated tliat there is a considerable portion of the silver lost in reducing the chloride by subcarbonate of potassa, but I have found that almost the whole of it is ob- tained from the chloride by conducting the process in the manner I have described. The diagram represents the re- action that takes place between the potassa of the subcarbon- ate and the chloride of silver. 2 A 354 FULMINATING SILVER. Before decomposition, After decomposition. 48 Potassa i °Wn 8 "~ ™ 8 ^^ ikea ^ eA ' ( Potassium 40 76 Chloride of Potassium. 146 Chloride f Chloride 36 of Silver \ Silver . . 110 110 Silver. 194 194 194 1039. To prepare metallic silver from the chloride Dr. Ure recommends 100 of it to be fused in a crucible with 19.8 of pure lime and 4.2 of charcoal. 1040. Mr. Keir discovered that an acid liquor composed of eight parts of sulphuric acid and one of nitre has the pro- perty of dissolving silver while it does not act upon copper, and has accordingly recommended it to be employed for re- moving silver from plated goods. The action of the liquid should be assisted by a moderate heat, not exceeding that of boiling water, and the silver precipitated by a solution of com- mon salt, reducing the chloride that is precipitated in the usual manner. 1041. Oxide of Silver may be obtained by adding a so- lution of the nitrate of silver to a solution of baryta, the oxide being immediately precipitated, while nitrate of baryta remains in solution ; solutions of the alkalis and other alkaline earths also precipitate oxide of silver from the nitrate. 1042. Fulminating silver is a compound of ammonia and oxide of silver, which is usually prepared by pouring water of ammonia on oxide of silver precipitated from the nitrate by lime water, after washing it on a filter. In twelve hours the liquid must be cautiously decanted, and the black fulminating compound that remains allowed to dry spontaneously on small pieces of filtering paper. 1043. As many accidents have occurred during the preparation of this compound, even with those who have been accustomed to chemical manipulations, it will be better for the beginner to pass over this process. It detonates when touched with any hard body, and if any quantity be used, the explosion is ex- NITRATE OF SILVER LUNAR CAUSTIC. 355 tremely violent. The liquid, also, when gently heated, affords a still more dangerous compound, which explodes even when touched under the surface of the liquid. 1044. The most delicate test of silver in solution is muriatic acid, or a solution of any muriate, chloride of silver being immediately precipitated in the form of a white curdy preci- pitate, which becomes of a dark purple colour on exposure to the air. Sulphureted hydrogen and solutions of the hydro- sulphurets give a black precipitate of sulphuret of silver ; arsenite of potassa a yellow precipitate of arsenite of silver. Small metallic globules of silver obtained by decomposing any of its compounds on charcoal before the blow-pipe are easily recognised by their brilliant white colour, their hardness, and the manner in which they rest above the surface of the char- coal, not being imbedded in it like many other metals reduced on charcoal, but rising above it, and adhering only by a small point. 1045. The most important salt of this metal is the Nitrate or Silver. It is prepared by digesting silver in a glass vessel with one and a half times its weight of nitric acid, diluted with an equal bulk of water, and evaporating the solu- tion to dryness. One portion of the acid affords oxygen to the silver and nitric oxide gas is disengaged, the oxide formed in this manner combining with the acid that is not decom- posed. When dissolved in less than its weight of hot water, the solution affords tabular crystals as it cools. 1046. The fused nitrate of silver of the different colleges, or Lunar Caustic, is prepared by melting the crystallized nitrate in a porcelain crucible, capable of containing four or five times as much as is employed, heating it very gently at first to prevent it from boiling over and pouring it whenever it becomes quite liquid into cylindrical moulds well greased with a little tallow. The operator must take care to avoid the very caustic sparks that are occasionally thrown out of the crucible during the fusion of the nitrate. 1047- Nitrate of silver is soluble in its own weight of water, stains the skin black, and is decomposed by sulphuric and 356 DETONATING SILVER. muriatic acids, solutions of the alkalis and earths, sulphureted hydrogen, hydrosulphurets, by many of the metals, and a great number of astringent vegetable solutions. The action of ammonia has been described in 898. 1048. Common marking ink is composed of a solution of this salt thickened with a little mucilage, and the prepara- tory liquid with which the part to be marked is previously moistened is a solution of subcarbonate of soda also thickened with a little mucilage. 100 grains of the fused nitrate may be dissolved for this purpose in distilled water, and two or three drachms of mucilage added to the solution, keeping it in a bottle; for the preparatory liquid, again, half an ounce of the subcarbonate of soda may be dissolved in two or three ounces of water, adding half an ounce of mucilage to the solution. 1049. Sulphate of Silver may be obtained by digesting metallic silver in sulphuric acid, one portion of the acid being decomposed, affording oxygen to the metallic silver while sul- phurous acid is disengaged, and the rest combining with the oxide. It may be prepared also by adding a solution of the sulphate of soda to a solution of the nitrate of silver, nitrate of soda remaining in solution and sulphate of silver being preci- pitated. 1050. Phosphate of Silver is precipitated when a solu- tion of the phosphate of soda is added to a solution of the nitrate of silver, a double decomposition taking place and nitrate of soda remaining in solution. 1051. Carbonate of Silver may be obtained by adding a solution of an alkaline carbonate to a solution of the nitrate of silver. 1052. Cyanate of Silver, another detonating compound of silver, less dangerous than the one already described, may be prepared by dissolving metallic silver in strong nitric acid, and adding the solution to alcohol, proceeding in the manner directed for the preparation of cyanate of mercury and using the same proportions of metal, acid and alcohol. It explodes much more violently than cyanate of mercury, and should be Ijandled with still more precaution, never touching it with any GOLD, 357 thing but a piece of paper or a card, except for the purpose of experiment. It is detonated by heat, friction, percussion, and several of the acids, producing a very sharp report. 1053. Chloride of Silver is always formed when muria- tic acid or a solution of any muriate is added to a solution of a salt of silver, being precipitated in the form of a white curdy looking powder. Exposed to the direct rays of the sun it soon becomes of a purple or black colour from the de- composition of a portion of the chloride ; it is easily fused by a temperature about 500, forming a mass like a piece of horn as it cools, and hence it is often called Luna Cornea or Horn Silver. CHAP. nr. GOLD. Equivalent 200. Specific gravity 19-3. It requires a tem- perature above 1200 for its fusion, when it has a bluish green colour. 1054. When gold is alloyed with copper, it maybe separated by the process of cupellation, proceeding in the manner that has been described for the cupellation of silver; 15 or 20 grains of an alloy containing about a tenth of its weight of copper will be sufficient to show the nature of the process on the small scale. 1055. Silver and platina cannot be removed in this manner, as neither of these metals is oxidated by exposure to a high temperature. Platina is not often alloyed with gold, and silver may be separated by the operations of Quartation and Parting. Quartation consists in fusing the alloy with three times its weight of silver, by which the particles of the gold are sepa- rated to a greater distance from each other, and prevented from covering or protecting any of the particles of silver from 358 CHLORIDE OF GOLD the action of nitric acid. Parting again consists in boiling the alloy in seven or eight times its weight of nitric acid to remove the silver, diluting the acid with an equal bulk of water or rather more, and repeating the operation with a smaller quantity of acid till the whole of the silver has been extracted. Gold not being soluble in nitric acid, all that the alloy may have contained is left in a porous mass of the same form as the original alloy, or reduced to powder. 1056. When gold is exposed to an intense heat by the oyxhydrogen blow-pipe, it is dissipated in vapour, and a purple powder may be collected, which has been regarded as an oxide of gold. Its composition is still uncertain. 1057- Peroxide of Gold may be obtained by adding a solution of pure potassa to a solution of the chloride of gold, taking care not to add excess of alkali ; muriate of potassa remains in solution, and the peroxide is precipitated in com- bination with a portion of water, the usual reaction taking place between the metallic chloride and part of the water that is decomposed. 1058. Chloride of Gold may be obtained by digesting small fragments of gold in a mixture of one part of nitric acid and two of muriatic acid, evaporating the solution to dryness with a very gentle heat to expel any excess of acid. The gold is dissolved by the chlorine evolved by the mutual re- action of the nitric and muriatic acids (482). If the heat be too strong, the chlorine will be dissipated, and nothing will remain but metallic gold ; great caution is therefore required in evaporating the chloride to dryness. 1059. A weak solution of the chloride of gold may be ob- tained by shaking gold leaf with a solution of chlorine in water. None of the acids act upon gold except the nitro- muriatic, and a mixture of chromic and muriatic acids, and in both cases chlorine may be considered the actual solvent, part of the oxygen of the nitric or chromic acid combining with the hydrogen of a portion of muriatic acid and disengag- ing this element. 1060. Digest the dry chloride of gold in water, and filter the liquid ; a solution of chloride of gold is obtained of a deep GOLD. 359 reddish brown colour. If it is concentrated and then set aside to cool, small crystals of chloride of gold are deposited. 1061. Ammoniuret of Gold, or Fulminating Gold, may be obtained by adding ammonia to a solution of the bichlo- ride of gold ; a portion of water being decomposed and per- oxide of gold precipitated in combination with ammonia, while muriate of ammonia remains in solution. It is of a reddish brown colour, and should be allowed to dry on a filter at natural temperatures after washing it with water. It deton- ates violently by friction and percussion, or when exposed to heat, its elements being separated from one another, and must never be touched with any hard substance except for the pur- pose of experiments. It should be kept in a wide-mouthed bottle, closed tightly with a cork, and in small packets of paper. 1062. Add a solution of the green sulphate of iron (proto- sulphate) to a solution of the chloride of gold ; metallic gold is precipitated, water being decomposed and its hydrogen combining with the chlorine, while the oxygen converts the protoxide of iron into peroxide. Digest the precipitate thrown down in this manner in dilut- ed sulphuric or muriatic acid to remove any oxide of iron that may have been thrown down along with the gold, and the latter will be obtained in a state of great purity. 1063. Add a solution of the muriate of tin (protomuriate) to a solution of the chloride of gold ; a purple precipitate is immediately thrown down, which has been regarded as a com- pound of peroxide of tin and the oxide of gold. It is well known by the name of Purple of Cassius, and is used for communicating a rich red or pink colour to glass. 1064. Touch a piece of crystallized borax with a glass rod that has been dipped into a solution of the chloride of gold, and on exposing it to heat before the blow-pipe on a piece of earthen ware or baked clay, or fusing it in a crucible, a glass will be obtained which will have a very rich red or pink co- lour. 1065. Ethereal Solution of Gold, which is used for gilding a number of substances, may be easily prepared by shaking a 360 PLATINA. strong solution of the chloride with an equal bulk of pure ether, the ethereal solution collecting above, and a heavier li- quid remaining below. It should be decanted immediately and kept in a stoppered bottle enclosed in a case to protect it from the action of the light. CHAP. IV. PLATINA. Equivalent 96. Specific gravity 21.5, 1066. It is not fused on exposing it to the strongest heat of a smith's forge ; small portions may be easily melted how- ever by drawing it into thin wires, and holding them in the flame of the oxyhydrogen blow-pipe. It may be welded like iron by exposing it to a high temperature, and it is in this manner that platina crucibles and other vessels made of this substance are formed. 1067- Platina may be obtained from its ores by digesting them in a mixture of three parts of muriatic and one of nitric acid, adding a solution of the muriate of ammonia to the so- lution of the chloride of platina obtained in this manner, and exposing the yellow precipitate that is thrown down to a red heat in a crucible, placing it in a chauffer on the open fire. It is regarded as a compound of muriate of ammonia and per- chloride of platina, and is completely decomposed by heating it, muriate of ammonia and chlorine being disengaged, while nothing remains but metallic platina of a dull leaden colour, and in the same minute state of division in which it is precipi- tated. It is in this manner also that the spongy platina which becomes incandescent on bringing it into contact with air and hydrogen gas is prepared. See 63 — "JO. 1068. Oxide or Platina may be obtained by decompos- PLATINA, 361 ing the chloride of platina with a solution of potassa, the same reaction taking place between the water and the chloride. 1069- The Peroxide of Platina is not easily obtained in a pure form, from its tendency to form triple salts when thrown down from any solution in which it may exist. It has been procured by boiling the perchloride of platina with sul- phuric acid, and decomposing the persulphate formed in this manner by a solution of potassa. 1070. Platina may be detected in solution by the dark port wine colour which solutions of hydriodic acid communicate to any liquids containing it. A solution of the muriate of tin renders the liquid of a bright red colour. A solution of po- tassa gives an orange-coloured precipitate ; but with soda the liquid remains perfectly transparent. Sulphureted hydrogen gives a black precipitate ; and on evaporating any of the solu- tions of this metal to dryness, metallic platina may be obtain- ed by exposing the residuum to a strong heat. 1071. Sulphate of Platina may be formed by trans- mitting a stream of sulphureted hydrogen gas through a solu- tion of the chloride of platina, and digesting the precipitate in nitric acid. It is soluble in water, alcohol, and ether. 1072. Fulminating Platina may be obtained by adding ammonia to a solution of the sulphate of platina, and boiling the precipitate that is thrown down in a solution of potassa ; it must then be washed on a filter with water and allowed to dry. It explodes violently when heated to the temperature of 400. 1073. Chloride of Platina. may be prepared by digest- ing metallic platina in a mixture of nitric and muriatic acids, in the proportions recommended for separating it from its ores, (1046) evaporating the solution to dryness by a gentle heat, dissolving the residuum in water, and filtering the solution. 1074. In this process, the chlorine set at liberty by the reaction of the nitric acid muriatic acids dissolves the platina, none of the acids having any action upon this metal when per- fectly pure, though it has been ascertained that nitric acid can dissolve it when an alloy containing a small portion of this metal is digested in it. 362 XICKEL, &c. 1075. A singular compound has been described by Mr. J. Davy, composed of platina, oxygen, nitrous acid, and carbon. It is prepared by boiling sulphate of platina prepared in the manner described in 1050, in strong alcohol, and drying the black powder that is precipitated. It is distinguished by be- coming incandescent and being completely decomposed when it is put on a piece of bibulous paper moistened with alcohol, a hissing noise being produced at the same time, and nothing remaining but metallic platina. CHAP. V. NICKEL, &c. Equivalent 26. Specific gravity 8.2 to 8.8. A very high tem- perature is necessary to fuse it ; less, however, than is necessary to melt manganese. It is attracted by the mag- net. (See note to Nickel in the table of equivalents.) 1076. Nickel is usually obtained from the impure native sulphuret of this metal, the ore being heated to drive off the sulphur and arsenic, and the residuum intimately mixed and exposed to a very high temperature with twice its weight of black flux. 1077- The nickel obtained in this manner is still very im- pure ; it may be separated from the other metals with which it may still be combined by the following process. Reduce a quantity of the alloy of arsenic and nickel well known in commerce by the name of Speiss to powder, and boil it in di- luted sulphuric acid till it is dissolved, adding small quantities of nitric acid from time to time to promote the oxidation ; a deep green coloured liquid is obtained in this manner, contain- ing sulphate of nickel in solution, which must be decanted from the arsenious acid that remains undissolved. After con- centrating it by evaporation, and putting it aside to cool, green crystals of sulphate of nickel arc deposited. These must be NICKEL, &C. 363 dissolved in water and carbonate of nickel precipitated from the solution by carbonate of soda, and on exposing the light green coloured powder which is precipitated to a very strong heat for one or two hours with charcoal in a crucible, a button of metallic nickel is obtained. 1078. By evaporating the liquid that remains after the first crystallization of sulphate of nickel more crystals of this salt are procured ; but when this has been repeated two or three times, the crystals that are deposited are composed of sulphate and arseniate of nickel. From these pure sulphate of nickel may be obtained by dissolving them in water, passing a cur- rent of sulphureted hydrogen through the solution as long as any precipitation takes place, filtering and evaporating the clear solution, concentrating the liquid that is obtained after dissolving the green residuum in water, and filtering it. 1079. Oxide of Nickel may be obtained by heating the carbonate of nickel to redness in an open crucible. Its co- lour is gray, and the most of its salts have a green colour. 1080. Peroxide of Nickel may be prepared by trans- mitting chlorine through water in which the protoxide is dif- fused in fine powder, a portion of this liquid being decompos- ed, the hydrogen combining with the chlorine and the oxygen with the oxide of nickel. 1081. The nitric and nitromuriatic acids are the best sol- vents of this metal ; sulphuric acid has little action on it, but combines readily with the oxide that is formed on adding a little nitric acid. The other metals belonging to this class are comparatively rare productions, and as they are not likely to be made the subject of experiment by the beginner, it is not necessary to take any notice of them in this place. ALLOYS. AMALGAMS. 1082. Alloys are usually prepared by melting together the different metals of which they are composed ; and those in 364 ALLOYS. AMALGAMS. which mercury forms a constituent part, which are termed amalgams, may be formed by dissolving the different metals which they may contain in mercury when a large proportion of this metal is required ; and by adding it to them, if the quan- tity be comparatively small. In the following paragraphs, the composition of some of the most important alloys is stated, small quantities of which may be easily prepared in the manner we have described. 1083. Brass is composed of copper and zinc, usually in the proportion of three to one, and occasionally contains a small quantity of other metals. A small quantity may be easi- ly prepared by melting two parts of copper and one of zinc in a crucible, covering the mixture with a little salt and charcoal to protect it from the action of the air, and pouring out the alloy as soon as the metals have been completely melted, and stirred together with an iron rod. It is better to use an ex- cess of zinc, as a considerable quantity is always volatilized by the heat. 1084*. On the large scale, brass is prepared in a different manner, as there would be a great loss of zinc if the pure metals were melted together in a crucible. The impure oxide of zinc is mixed with charcoal and exposed to heat in a cover- ed crucible, pieces of sheet copper being laid over the mixture. The zinc is reduced and converted into vapour, combining with the copper as it is disengaged and forming brass ; when the process is conducted in this manner, the brass is said to be prepared by cementation. 1085. Dutch Gold and Pinchbeck are composed of the same metals, and contain a large quantity of zinc. 1086. Bronze is an alloy of copper and tin, and is used for making statues, cannons, bells, and for a variety of other purposes. The proportions usually employed are nine parts of copper to one of tin. 1087- Speculum Metal, the alloy used for making the specula of reflecting telescopes, is composed of two parts of copper and one of tin ; a small quantity of zinc and arsenic, about one part of each to fifty of the alloy, may be added to it to improve its lustre. ALLOYS. AMALGAMS. 365 1088. Pewter is composed of about 20 parts of tin and one of copper ; small quantities of antimony and bismuth are occasionally melted along with it, and give it a whiter colour. Inferior kinds of pewter are made with about a fifth of its weight of lead. 1089. Plumber's Solder is composed of equal parts of tin and lead. 1090. The alloy used for making printing types consists principally of about three parts of lead and one of antimony. 1091. The Fusible Alloy is prepared by melting in a crucible eight parts of bismuth, five of lead, and three of tin. It fuses at the temperature of 210. 1092. Gold Coin is composed of eleven parts of gold and one of copper. 1093. Standard Silver is an alloy of twelve parts and a third of silver and one of copper. 1094. Mercury amalgamates readily with a number of me- tals. Gold and silver are rendered very brittle when combin- ed with a very small quantity of this metal. 1095. Various compositions have been used as an amalgam for the electrical machine ; one part of zinc with an equal weight of tin and two parts of mercury does very well for this purpose. 1096. When mercury is poured on tin foil it spreads ra- pidly over its surface, forming an amalgam which is used in making looking glasses. 1097- An amalgam composed of one part of tin, one of lead, two of bismuth, and four of mercury, is employed for silvering the inside of hollow globes of glass. 1098. If one part of mercury be added to the fusible alloy (1081) an amalgam will be obtained which becomes soft at 162, and quite fluid at 170. This is the compound of which fusible spoons are made. 1099. Iron is coated with tin by dipping it in a melted allov consisting of ten parts of tin and one of copper. The copper prevents too large a quantity of tin from adhering to the iron ; the melted metal should be covered with a little tallow to pre- vent it from oxidating. It is in this manner that Tinned 366 ALLOYS. AMALGAMS. Iron is prepared, consisting of thin sheet iron coated with tin. 1100. Copper vessels are coated with tin by rubbing them over with muriate of ammonia, throwing a little powdered resin on them to prevent the copper from acquiring any crust of oxide, and spreading a little melted tin on their surface after exposing them to heat. 1101. Copper may be coated with silver by rubbing it with the following mixture made into a paste with water, after boiling it in water with cream of tartar and alum ; — one part of the bichloride of mercury, four of silver precipitated from a so- lution of the nitrate of copper, sixteen of common salt, and an equal quantity of the muriate of ammonia. The copper must then be exposed to a red heat to drive off the mercury, after which the coating of metallic silver may be polished. 1102. Silver, copper, and brass are easily gilded by an amalgam composed of eight parts of mercury and one of gold, prepared by heating a mixture of the above metals in these proportions till the gold is completely dissolved, and pouring- it immediately into cold water to prevent any loss of mercury. The metal to be gilded is previously washed with a dilute solu- tion of the nitrate of mercury containing an excess of acid, and the amalgam laid over as uniformly as possible with a brush made of brass wire. By exposing it to heat in a furnace or over an open fire, the mercury is dissipated, and the coat- ing of gold left in combination with the metal, after which it may be polished. 1103. Steel may be gilded by dipping it into the ethereal solution of gold prepared in the manner described in 1065, dipping it into the liquid and washing it immediately in water. 1104. The gold powder used in painting is prepared by ex- posing an amalgam of gold and mercury to heat (1102) till all the mercury is volatilized, or by triturating gold leaf with a solu- tion of gum, washing away the gum afterwards with a large quantity of water. 367 DIVISION II. VEGETABLE AND ANIMAL SUBSTANCES. 1105. The vegetable acids and several other substances, as alco- hol and ethers, usually arranged under vegetable chemistry, having been placed under carbon in this work, this division will include a series of experiments and processes connected with the other classes of vegetable proximate principles, and some important compounds in animal chemistry. 1106. Vegetable substances being composed principally of carbon, oxygen, and hydrogen, retained together by nicely balanced affinities, they are in general very easily decomposed ; none of them can bear even a dull red heat, and most of them suffer decomposition at a much lower temperature. Hence in all experiments with bodies belonging to this class, great at- tention must be paid to the temperature to which they are ex- posed : the same remark applies to all the proximate principles peculiar to the animal kingdom, composed of oxygen, hydro- gen, carbon, and nitrogen. 1107- The ultimate analysis of vegetable and animal sub- stances being one of the most complicated operations of ana- lytical chemistry, it will be sufficient to state here that the proportions of carbon and hydrogen is generally ascertained by converting these elements into carbonic acid and water, 22 of carbonic acid and 9 of water, indicating respectively the presence of 6 of carbon and 1 of hydrogen ; — the quantity of nitrogen by separating the carbonic acid from the rest of the gas evolved; — and the proportion of oxygen by deducting the weight of the two or three preceding elements as they may happen to be present from the total weight of the vegetable or animal sub- stance subjected to examination, taking into account the quantity of oxygen that is consumed in the operation. Per- oxide of copper is the compound that is preferred in processes 368 gum. of this kind, having the property of parting readily with oxy- gen when heated with inflammable matter, while it can be ex- posed to a white heat without losing any of this element. CHAP. I. GUM, SUGAR, STARCH, GLUTEN, TANNIN, LIGN1N. GUM. 1108. Dissolve some gum arabic in water, and pour the solution into alcohol ; the water combines with the alcohol, and the gum is precipitated. Gum is insoluble in alcohol, and all infusions and decoctions containing a quantity of this principle in solution, give a precipitate with alcohol, when it is mixed with them in sufficient quantity. 1109. Add a solution of oxalic acid to a solution of gum in water ; the acid will unite with the small quantity of lime which gum always contains, forming oxalate of lime, which is separated in the form of a white precipitate. 1110. Expose a portion of gum arabic to the flame of the blow-pipe till nothing remains but a white or greyish white ash, which is composed principally of carbonate of lime ; dis- solve it in diluted muriatic acid in a test tube, and precipitate oxalate of lime from the solution by oxalate of ammonia. 1111. Add a solution of gum arabic to a solution of the subacetate of lead; the gum is immediately precipitated in combination with pari; of the oxide of lead. Gum is precipi- tated from its solution by some other salts, as the persulphate of iron and pernitrate of mercury. 1112. Adda solution of silicatcd potassa to a solution of gum arabic ; a precipitate is thrown down immediately which has been regarded as a compound of the lime which the gum SUGAR. 369 contains, and silica. The pure alkalis form soluble compounds with gum. 1113. Mix some powdered gum with nitric, sulphuric, or muriatic acid, diluted with a considerable quantity of water ; the gum will be dissolved, but no farther change will take place, at least for some time. Mix some powdered gum with strong sulphuric and nitric acid. It will soon be completely decomposed ; the sulphuric acid causing a deposition of charcoal, and the nitric acid con- verting it into oxalic acid, if a large quantity be employed. SUGAR. 1114. Dissolve sugar in hot water till a strong syrup is obtained, and put the solution aside in a warm place. Crys- tals of sugar (candied sugar) are slowly deposited. Large crystals of sugar may be obtained by dissolving it in alcohol, and setting aside the solution for some time ; four parts of hot alcohol take up about one of sugar. 1115. Rub two pieces of white sugar briskly on one another in the dark, a green phosphorescent light is seen at the point of contact. 1116. Mix equal weights of sugar and chlorate of potassa, and touch the mixture with a glass rod dipped in sulphuric acid. A rapid deflagration immediately takes place, a small quantity of sulphate of potassa is formed and peroxide of chlo- rine disengaged, (453) the heat produced being sufficient to inflame the mixture, and the chlorate of potassa affording oxygen to support the combustion of the sugar. 1117. Sugar decomposes strong nitric acid, a large quan- tity of fumes of nitrous acid being disengaged, while it is con- verted into oxalic acid. 1118. Digest some slaked lime in fine powder in a solution of sugar in water ; a considerable quantity is dissolved and may be precipitated again by oxalic, tartaric, carbonic, and sulphuric acids. 1119. Sugar, like tartaric acid, has the property of pre- 2 E 370 STARCH OR FECULA. venting oxide of iron and some other metallic oxides from being precipitated from their solutions by some of those rea- gents that usually throw them down ; it possesses this pro- perty, however, only when it has been boiled along with the solution of the metallic salt. Sugar has also the property of partially deoxidating a number of the metallic oxides when their solutions are heated together. 1120. A number of vegetable and animal substances may be converted into sugar by the action of sulphuric acid, such as wood, gum, starch, linen, glue, &c. The usual process consists in mixing the animal or vegetable substance with about twice its weight of sulphuric acid, diluting the mixture in a day or two with a large quantity of water, and boiling it for six or more hours, adding more water from time to time as it may be required. The liquid is then to be neutralized with chalk, and filtered, and the clear liquid evaporated till it at- tains a syrupy consistence, after which it may be set aside to crystallize. STARCH OR FECULA. 1121. A small quantity of starch may be easily prepared from potatoes, by diffusing through a large quantity of water the pulpy mass that is obtained on grating them, and allow- ing it to remain at rest. In this process, the saccharine and mucilaginous matters that exist in the potatoes are dissolved by the water ; the starch being heavier than water, and insoluble in this fluid, is deposited at the bottom in the form of a fine pow- der, and the fibrous matter floats above. It may be purified by washing it repeatedly with cold water, and pouring off the supernatant liquid. On the large scale, the supernatant liquid is net poured off till it begins to ferment, a larger quantity of starch being procured in this manner, and the fibrous matter more easily separated. Common starch is prepared from wheat by a similar process. 1122. Starch is easily distinguished from gum and sugar by its insolubility in cold water, and by forming a jelly with hot GLUTEN LI ON IN. 371 water. Its solution in water decomposes the solutions of several metallic salts, but gives no precipitate with silicated potassa. Its action on iodine, which is the most delicate test of this substance, has been already stated, (500-1-2-3.) GLUTEN. 1123. Gluten may be obtained from wheat flour by making it into a stiff paste with water, and washing it in a linen cloth or bag with a large quantity of this fluid as long as any white powder passes through the interstices of the cloth. The gum and sugar are dissolved by the water, the starch is carried away in suspension in the form of a white powder, and the gluten remains in the cloth. It is very tenacious and ductile. It is insoluble in water, and is speedily decomposed when moist from the reaction of its elements. It is considered the most nutritious part of wheat flour, and contains nitrogen in addition to the usual elements of vegetable matter. 1124. Gliadine and Zimome, the two principles of which gluten is composed, according to M. Taddey, may be separa- ted by rubbing gluten with successive portions of alcohol in a mortar as long as the fluid becomes milky on diluting it with water ; the alcohol dissolves the gliadine and leaves the zimome. 1125. Zimome is particularly distinguished by the bluish green colour which it assumes when moistened with water and triturated with powdered gum guaiac. The same colour appears when wheat flour or gluten is treated in a similar man- ner with gum guaiac, the colour of the flour being deeper in proportion to the quantity of gluten which it contains. LIGNIN. 1126. Lignin is the term applied to the woody fibre which forms the basis of all the products of the vegetable kingdom. It is insoluble in water and alcohol. 372 COLOURING MATTER. TAN OR TANNIN. 1127. Tannin exists in a great number of vegetable sub- stances, and is usually associated with gallic acid ; it may be obtained in a pure state by precipitating it from an infusion of galls by permuriate of tin, diffusing the precipitate of oxide of tin and tannin in a large quantity of water, and separating the oxide by a stream of sulphureted hydrogen ; sulphuret of tin is formed in this manner, and tannin remains in solution. 1128. Mr. Hatchett has pointed out that tannin may be formed artificially by digesting charcoal, and a number of vege- table substances containing a large quantity of this element in nitric acid ; some, however, suppose that this is merely a com- pound of charcoal and nitric acid. Tannin is distinguished by its astringent taste, precipitating; a number of metallic oxides from their solutions, and forming a copious precipitate with solutions containing gelatine, similar in its composition to leather, which is a compound of tannin and gelatin. It is very soluble in alcohol, and in hot water, and is precipitated from its solution by acids. CHAP. II. COLOURING MATTER. 1129. To prepare the coloured test papers which have been so frequently referred to in this work, a red cabbage must in the first place be cut into slices and boiled for half an hour in a pint or two of water, adding more water from time to time if it should be required, to prevent any of the vegetable matter from being decomposed by the heat. The liquid is then to be decanted from the fibrous matter that remains, and concentrated by evaporation till it is reduced to five or six ounces by mea- sure, pouring it afterwards into a flat plate or bason, and steeping in it pieces of unsized writing paper (common print- ing paper does very well) taking care to moisten every one COLOURING MATTER. 3.^3 thoroughly by drawing it backwards and forwards several times through the liquid before they are laid above one another. In half an hour they may be taken out to dry, hanging them on a piece of cord drawn tight between two nails on the op- posite side of a room where they will not be exposed to dust or acid fumes. The paper may be cut into pieces about the size of an octavo page before they are immersed in the solu- tion, and each of them may be divided across into thirty or forty pieces, putting them into a tin case or any other conve- nient vessel that they may be always at hand, as they are con- tinually required in a great variety of operations. A suffici- ent quantity may be made at once in this manner to serve for a year or two even where a great number of experiments are performed. 1130. Paper dyed blue with the colouring matter of the cabbage is used for indicating the presence of acids and alkalis, being turned red by the former and green by the latter. It is sufficiently delicate for all ordinary experiments, and is pre- ferable to litmus paper, which is not affected by alkalis, unless previously reddened by an acid, when the original blue is restored. 1131. When the colouring matter of the cabbage is required in solution, it may be easily obtained by infusion in water. It begins to pass into a state of putrefaction in a few days, however, exhaling a very disagreeable smell, and the colour fading at the same time. The concentrated solution may be kept for a long time when put in bottles which have been com- pletely filled with it, after mixing every ounce or two with a drachm of sulphuric acid. Mr. Faraday states that it may be preserved in this manner for a year. 1132. Litmus and Turmeric test papers may be prepared by a similar process. The litmus must he reduced to fine powder and boiled with water to procure a solution fit for the purpose ; turmeric water again may be obtained sufficiently strong by pouring boiling water over this substance in powder. Litmus paper is used as a test for the presence of acids which immediately redden it, and as a test for alkalis when it has been previously reddened by an acid. Turmeric paper again 374 COLOURING MATTER. is rendered of a reddish brown colour by alkalis and alkaline earths, but is not affected by the acids ; it may be used, how- ever, as a test of acids when it has been turned brown by an alkali, the acid combining with the alkali and restoring its original yellow colour. It cannot be relied on, however, as a test for the presence of alkalis, a number of compound salts, and other substances affecting it in the same manner as these bodies, as Mr. Faraday has pointed out. EXPERIMENTS WITH COLOURING MATTER. 1 133. Put a small quantity of a strong solution of the mu- riate of tin into seven or eight ounces of a solution of litmus, and add a solution of potassa as long as it produces any precipi- tate. The potassa combines with the muriatic acid, forming muriate of potassa which remains in solution, and the oxide of tin uniting with the litmus forms an insoluble compound which is immediately precipitated. It is in this manner that the pigments called Lakes are usually prepared. 1134. Make a similar experiment with solutions of alum (sulphate of alumina and potassa) and litmus ; on adding the solution of potassa, the alkali combines with the sulphuric acid previously in combination with the alumina, which is thrown down in combination with the litmus. As the oxide of tin and alumina can combine only with a certain quantity of colouring matter, if the whole of the litmus be not precipitated at first, and the liquid left transparent and colourless, by adding an additional quantity of muriate of tin or alum to the solution, and precipitating as before by potassa, all of it may be thrown down. 1135. Make a strong solution of cochineal in water, and precipitate the colouring matter in combination with alumina or oxide of tin, by a solution of potassa. A rich coloured lake is immediately precipitated well known by the name of Carmine. 1136. Acetate of alumina is generally preferred to alum in processes where alumina is to be separated in combination with colouring matter, as the acetic acid that is disengaged is COEOORlNG MATTER. 37'5 not so liable to react upon cloth or colouring matter as sul- phuric acid, which often proves troublesome when alum i s used. It may be easily obtained by adding a solution of the acetate of lead to a solution of alum as long as any precipita- tion takes place, filtering the liquid to separate the sulphate of lead that is thrown down, and concentrating the solution by evaporation. U37. Digest some indigo reduced to powder for an hour or two in sulphuric acid ; a solution will be obtained which has a greenish yellow colour at first, and passes to a deep blue when it has been kept for several hours. Dilute the solution with^a large quantity of water, and put a piece of silk, linen, or cotton into it, taking it out immediately and allowing it to dry. Part of the indigo will combine with the cloth, and it will be found to be dyed blue, the shade being more or less deep according to the strength of the solution. 1138. Dissolve some sulphuret of arsenic in a hot solution of potassa, and digest indigo reduced to a fine powder in the liquid. The metallic sulphuret attracts oxygen from the in- digo, when it will become of a green colour, and be immediately dissolved. Put a piece of cloth into the solution, and take it out to dry, exposing it freely to the air. The cloth will combine with a portion of deoxidated indigo immediately, and appear of a green colour when taken out of the liquid ; it soon at- tracts oxygen from the air however, the indigo recovering its original colour, and it is in this manner that cloth is usually dyed blue. 1139- Expose some indigo to heat over a chauffer in a glass vessel ; it is sublimed at the temperature of 550, a reddish violet coloured vapour being formed, which bears a consider- able resemblance in its appearance to iodine, and condenses in minute crystalline grains. 1140. Boil half an ounce of powdered brazil wood for a quarter of an hour in eight or ten ounces of water ; filter the solution of the colouring matter obtained in this manner through a double linen cloth, and dip a piece of cotton cloth into the liquid. It immediately combines with part of the 376 COLOURING MATTER. colouring matter, but the colour is neither bright nor perman- ent. 1141. Take another piece of the same cloth, pass it through a dilute solution of the muriate of tin, and allow it to dry. Then put it into the same solution of the colouring matter of the Brazil wood ; the compound of the cloth and the oxide of tin that is formed in the preceding part of the process attracts colouring matter from the solution and is immediately dyed red, the colour is also much brighter and more permanent than before, the oxide of tin retaining it more strongly in com- bination with the cloth by the great attraction which it has for both ; when a common metallic oxide or earth is used for this purpose, it is in general termed a Mordant or Basis. 1142. Similar experiments may be made with cochineal, madder, logwood and safflower, all of which are red dyes and termed Adjective Colours, as they require the intervention of some basis to render them permanent, having a feeble affinity for different kinds of cloth. When the affinity of colouring matter for cloth is so great that no basis is required to effect a permanent combination, it is usually termed a Substantive Colour, of which indigo is a very good example. 1143. Cloth maybe dyed yellow by proceeding in the same manner with solutions of the colouring matter of saffron, fus- tic, quercitron bark, or American hiccory. There are seve- ral other substances used for dyeing yellow ; the infusion of saffron will perhaps be found more convenient than any other for performing a few experiments of this kind. 1144. Cloth is dyed black with the same materials that are used in the preparation of writing. Steep a piece of cotton cloth in an infusion of galls or decoction of logwood ; dry it and then pass it through a solution of the sulphate of iron. It will be dyed black, the tint deepening on exposure to the air. 1145. By dyeing cloth first with one colour and then with another, or with mixtures of different kinds of colouring mat- ter in various proportions, it may be obtained of any particu- lar shade that may be required. 1146. Dip a piece of cloth dyed blue (by indigo) in an infu- VEGETABLE ALKALIS. 377 sion of saffron ; it will immediately become green, and retain this colour permanently. 1147. Put a number of stuffs dyed with different kinds of vegetable colouring matter into a solution of chlorine in water, or of the chloride of lime ; the colour will soon disappear, but those adjective colours which have been put on without any basis are destroyed before any of the rest. CHAP. III. VEGETABLE ALKALIS. The most important of the vegetable alkalis are morphia, quinia, cinchonia and strychnia, the method of preparing which and also the peculiar proximate principles with which they are associated in the different vegetable products from which they are obtained, will be described in the following sections. 1148. These alkalis are found in combination with vege- table acids, constituting a peculiar class of salts. By digest- ing them in water or alcohol these salts are dissolved, and on adding one of the common alkalis, or an earth, such as lime or magnesia, the vegetable alkali is separated, the other sali- fiable base combining with the acid. Various modifications of this process are adopted in the preparation of the different alkalis, and as they are not obtained in a pure form in this manner, being usually combined with a considerable quantity of colouring matter, further operations are required to separate it. Animal charcoal is usually employed for this purpose, and ether and alcohol may be sometimes used with advantage. By repeatedly dissolving them and precipitating or crystalliz- ing them from their solutions, the separation of the colouring matter may sometimes be effected without any foreign admix- ture, but it is in general preferable to employ animal char- coal. 37$ MORPHIA. Sect. I. — Morphia — Meconic Acid — Narcotine. 1149- Opium is composed essentially of a peculiar vegeta- ble alkali which has received the name of morphia, a vegetable acid which has been called meconic acid, and another vegeta- ble proximate principle which possesses neither acid nor alka- line properties, and has been termed narcotine. These are mixed in opium with several more common vegetable princi- ples, as gum, resin, gluten, a bitter matter, a dark colouring matter, and also with a small quantity of sulphate of lime. 1150. A number of processes have been proposed for ex- tracting morphia from opium ; the beginner will find the fol- lowing process of Robiquet's more easily conducted than any other. 1151. Take 1200 grains of the best Turkey opium, cut it into small pieces and rub it with water in a mortar, adding a little more from time to time till a uniform pulpy mass is ob- tained. Then add more water till about ten ounces altogether shall have been mixed with the opium. The mixture is to be left in this state for five days, shaking it occasionally, or it may be digested with a gentle heat for a day or two, taking care not to raise its temperature above 100, after which it may be filtered. The liquid that passes through the filter has a very dark colour, and contains the meconic acid and the mor- phia in solution, combined together in the form of meconiate of morphia. On boiling this solution for ten or twelve mi- nutes with 60 grains of magnesia, taking care to have it com- pletely decarbonated, (7^2), the meconic acid will dissolve part of the magnesia and remain in solution, meconiate of mag- nesia being formed, which is a soluble salt, and the morphia will be precipitated. It is still mixed, however, with a consi- derable quantity of colouring matter, which may be removed by washing it with cold water till it no longer affects the wa- ter, then alternately with a little hot and cold alcohol till no more colouring matter is taken up, and on boiling the residuum in an ounce or two of alcohol till it is dissolved, crystals of morphia. 379 morphia will be deposited from the solution as it cools, in a great measure free from colouring matter. 1152. Instead of treating it alternately with hot and cold alcohol before dissolving it in this liquid, the precipitated morphia may be boiled at once in alcohol with some animal charcoal, which will decompose most of the colouring matter, and crystals of morphia nearly deprived of colouring matter will be deposited as the liquid cools ; in both cases it is neces- sary to filter the solution before setting it aside to crystallize, to remove the excess of magnesia which is not dissolved by the alcohol. It is only by repeated solution and crystalliza- tion, however, that the morphia is obtained perfectly pure, though the product of the first crystallization has only a light fawn colour when a sufficient quantity of animal charcoal has been employed. 1153. In preparing morphia, the student should always avoid the vapours that are disengaged from the different solu- tions which he may require to boil, when he is operating on a considerable quantity of materials, as I have repeatedly seen them produce the same effects as an overdose of opium where this has not been attended to. 1154. By treating opium with muriatic acid, and preparing a solution of the muriate of morphia, more of this substance may be obtained, it has been lately affirmed, than by the usual process. Lime is also said to precipitate a larger quan- tity of morphia from the solution of the meconiate than mag- nesia. 1155. Morphia is the vegetable principle on which the narcotic property of opium more immediately depends, and its taste is intensely bitter. From its sparing solubility in water, it does not act so violently on the animal economy in its pure form as might have been anticipated, but when combined with an acid or any other substance which can render it solu- ble, it acts with great energy, half a grain given to a man in good health having produced symptoms which excited consi- derable alarm at the time, though he ultimately recovered. 1156. Put a test paper coloured by the blue infusion of 380 MORPHIA. cabbage into a solution of morphia in alcohol ; it will be im- mediately rendered green. 1157- Put another test paper coloured yellow by turmeric into the same solution ; it will be turned to a reddish brown. 1158. Shake some morphia with a small quantity of diluted sulphuric acid ; heat the mixture gently, and continue to add morphia till it is no longer dissolved. The sulphuric acid will be completely neutralized, and a solution of the Sulphate of Morphia will be obtained. It is very soluble in water. 1159. Acetate of Morphia, and the other salts of this vegetable alkali may be prepared in a similar manner. The mineral acids must always be diluted with water before com- bining them with morphia, as, in their concentrated form, they are very liable to decompose it. 1160. The Nitrate, Sulphate, Muriate, Acetate, Tartrate, Meconiate, and Carbonate of Morphia are all soluble and crystallizable. 1161. Add a solution of potassa, soda, or ammonia to a solution of a salt of morphia. The mineral alkali will com- bine with the acid, and the morphia be precipitated ; mor- phia is precipitated also when a solution of any of these alkalis is added to a watery infusion of opium, a meconiate of the alkali remaining in solution ; with the exception of ammonia, however, none of them can be used so advantageously for the preparation of morphia as magnesia, as any excess would react on other matters in solution and tend to decompose them, or dissolve the precipitated morphia. 1162. Put a small quantity of morphia into a test tube, pour a little nitric acid on it and expose it to a gentle heat. The solution will acquire a red colour, and a portion of oxalic acid be ultimately formed. 1163. Neutralize the liquid obtained in the above manner by ammonia, after diluting it with three or four times its bulk of water, and drop into it a solution of the muriate of lime. A copious precipitate of oxalate of lime will immediately ap- pear. 1164. Pour some nitric acid into a solution of the sul- MECONIC ACID. 3^1 phate of morphia, or of any other salt of this substance ; the solution will acquire the same deep colour as in the preced- ing experiment (1162). 1165. Add a small quantity of a solution of potassa to a solution of the sulphate of morphia ; the sulphuric acid will combine with the potassa, and the morphia will be precipi- tated. 1166. Pour in some more of the solution of potassa into the above liquid and the morphia will be redissolved. Similar ex- periments may be made with solutions of soda and ammonia. 11 67. Expose a little morphia to heat in a test tube over a spirit lamp ; in a short time it will be completely decomposed, a little carbonate of ammonia being disengaged along with the other products of the decomposition, morphia containing a little nitrogen besides the usual products of vegetable and animal matter, the ammonia being formed by the combination of nitrogen with part of the hydrogen, and the carbonic acid by the union of part of the carbon and oxygen. A little oily matter is also produced, and some carbonaceous matter is left in the tube. 1168. Throw some morphia on a piece of iron heated to redness, or on some red hot cinders ; it burns in the same manner as other vegetable substances. MECONIC ACID. 1169- Several processes have been pointed out for the pre- paration of Meconic Acid ; the following method, by which it is easily obtained, was recommended by Dr. Hare. Add a solution of the subacetate of lead to a watery infusion of opium as long as any precipitation takes place, wash the pre- cipitate on a filter till the water passes through colourless, then diffuse it through a quantity of water and pass a brisk stream of sulphureted hydrogen through it for a quarter of an hour or twenty minutes. The precipitate that is thrown down by the subacetate of lead is composed principally of meconiate of lead, which is decomposed afterwards by the sulphureted hy- 382 MECONIC ACID. drogen gas, sulphuret of lead and water being formed, while the meconic acid that is disengaged remains in solution. The sulphuret of lead must be separated by filtration, when the solution will appear of a reddish amber colour, and afford crystals on expelling the excess of sulphureted hydrogen and concentrating it by evaporation. 1170. The meconic acid may be separated from the me- coniate of lead by sulphuric acid ; the sulphate of lead that is formed being insoluble, it may be easily separated by filtration from the meconic acid that remains in solution as before. An excess of sulphuric acid interferes with the crystallization of the meconic acid, which is not then obtained so easily in crys- tals as when the decomposition of the meconiate has been effected by sulphureted hydrogen. 1171. When morphia is prepared from opium by magnesia, a considerable quantity of meconiate of lead may be easily procured by adding a solution of the acetate of lead to the so- lution of the meconiate of magnesia that remains after the precipitation of morphia by this earth (1151), acetate of mag- nesia remaining in solution. 1172. Meconic acid is soluble in water and alcohol; has a sour taste, reddens litmus paper, and is particularly distin- guished by the dark red colour which it produces when added to a solution of a persalt of iron. Drop a small quantity of the watery solution of meconic acid into a glass of water contain- ing a little of the muriate or sulphate of the peroxide of iron. The deep colour which it causes will immediately appear, and so delicate a test is a persalt of iron of the presence of meconic acid, that Dr. Hare was enabled to detect the presence of meco- nic acid by means of it in a gallon of water to which no more than ten drops of laudanum had been added ; the following is the manner in which he proceeded. A few drops of a solution of the acetate of lead were added to the water containing the laudanum, which was placed in a conical glass vessel, that the precipitate, which appeared in several hours, and was de- posited on the sides of the vessel, might be easily collected at the bottom by stirring it gently from time to time with a glass rod. The most of the supernatant liquid was then de- naucotini:. .'383 canted, or removed by a syphon, taking care that none of the precipitate was drawn up along with it, after which thirty drops of sulphuric acid were poured over the meconiate by means of a dropping tube, and an equal quantity of a solution of the persulphate of iron added in the same manner, when the cha- racteristic deep red colour appeared. 1173. Add a small quantity of a solution of the sulpho- cyanate of potassa to a wine glass of water, into which a drop of a solution of the persulphate of iron has been put, and com- pare the colour (750) with that produced by the meconic acid, which is very similar to it. NARCOTINE. 1174. Narcotine, known also by the name of the Salt of Derosne, may be easily prepared by evaporating a watery in- fusion of opium to the consistence of an extract, rubbing it with sulphuric ether in a mortar till a uniform mixture is ob- tained, and digesting it in a large quantity of ether for several hours. The meconiate of morphia is not affected by the ether, but the narcotine is dissolved, and the solution deposits it in crystals by spontaneous evaporation. 1175. Narcotine is soluble in alcohol, ether, and oils, but insoluble in water ; the addition of a small quantity of acid, however, renders it soluble, and in the watery infusion of opium it is supposed to be retained in solution by the meconic or some other vegetable acid. 1176. As the unpleasant sensations which the exhibition of opium so often produces, independent of its narcotic action, have of late been attributed to the narcotine alone, it may be deprived of this principle before it is made into laudanum by digesting it in ether for several hours in a close vessel, as a Papin's digester. 1177- When opium has been given as a poison, it may in general be 'detected by its peculiar odour, and by the deep red colour which a solution of a persalt of iron gives on treating the precipitate thrown down by acetate of lead from the liquid 384 NARCOTINE. procured by filtering the contents of the stomach, in the manner described in 1172- 1178. From the number of different principles which the infusion and tincture of opium contain in solution, they are decomposed by a great number of substances, many of which must occasionally be present in the liquid contents of the sto- mach ; metallic salts in particular, and astringent matter pro- duce this effect, so that it is necessary to examine also the solid matter that is obtained when laudanum has been ad- ministered as a poison, even though it should have been satis- factorily ascertained that no solid opium has been given along with it. 1179. In a case of poisoning by laudanum in which I exa- mined the contents of the stomach for Dr. Monro, no trace of opium could be discovered by any chemical reagents, though I suspected the presence of opium from the smell before I was told of the cause of death, being very similar to what I had noticed in another case which I was called to examine a few months before. In the present instance, the stomach-pump had been used, and the stomach repeatedly emptied and filled with fresh fluid, but the patient unfortunately was beyond recovery though the whole of the poison had been extracted. 1180. With respect to the antidotes to be employed when an over dose of opium has been given, there is no chemical remedy on which we can depend ; the carbonate of potassa has been proposed to precipitate the morphia from its solu- tion, and prevent it from acting so energetically as it other- wise would do. Recourse should always be had to the stomach-pump when it can be procured, and powerful emetics should be administered till vomiting is excited, giving at the same time large quantities of warm water, and prevent- ing the individual from falling into a state of sleep or stupor if possible, by forcing him to walk up and down till its effects have passed off. Diffusible stimuli should be given at the same time, taking care to avoid every thing which may render the morphia more soluble, as vinegar or acids, which would only increase its deleterious effects ; though, when the poison has QUINA. 385 been completely removed, some of them assist materially in restoring the tone of the whole system. Sect; II. — Quina, 1181. The beginner cannot be too particular in procuring the different specimens of the different varieties of bark which he may require from a source on which he can depend, as there is nothing that is more frequently adulterated than cin- chona bark. It is not only often mixed with barks of an inferior quality, or of a totally different kind, but offered for sale after its active principles have been in a great mea- sure extracted for particular preparations. This is not an imaginary case, as I have not only seen it noticed in other works, but have myself met with specimens of bark in this condition ; it is usually reduced to powder, mixed up with a fresh quantity of bark, and sold as a cheap bark to country apothecaries, a practice which cannot-be too much reprobated, and which the medical practitioner ought to be able to detect. 1182. Quina is found in the Cinchona Cordifolia or Yel- low Bark, in the Cinchona Lancifolia or Pale Bark, in the Cinchona Oblongifolia or Red* Bark, and in several other species of bark, all of which contain cinchonia likewise, ano- ther vegetable alkali. The yellow bark is usually employed for the preparation of quina, as it contains a considerable quantity of this principle, but very little cinchonia. In the pale bark, again, cinchonia is the alkali that predominates, while in the red bark a larger quantity of cinchonia and quina is said to exist than in each of the other varieties of bark. 1183. Quina and cinchonia are the principles on which the peculiar properties of Peruvian bark depend, and the existence of a peculiar principle in which its characteristic qualities reside was pointed out by Dr. Duncan, who gave it the name of cinchonine. 1184. Quina may be easily procured by decomposing a solution of the sulphate of quina in water by slaked lime, sul- 2 c 386 QUINA. phate of lime and quina being precipitated together, and di- gesting the precipitate in alcohol, which dissolves the quina, and leaves the sulphate of lime. 1185. Evaporate the alcoholic solution of quina till it is concentrated ; quina will be deposited, but it does not crys- tallize. 1186. Put a blue test paper into a solution of the quina ; it will be immediately rendered green, in the same manner as by solutions of the common alkalis. 1187- Add quina to a small quantity of sulphuric acid diluted with five or six times its bulk of water ; the quina will neutralize the sulphuric acid, and a solution of the sul- phate of quina will be obtained, which will yield crystals on evaporation * 1188. Throw a little quina on a red hot iron plate, or on some red hot cinders. It will inflame and be completely de- composed, the usual products of the combustion of vegetable matter being formed, and nitrogen gas disengaged. Heat a little in a close vessel, or in a glass tube, that it may not be exposed freely to the action of the air ; in addition to the products that are generally obtained during the decom- position of vegetable matter by heat in close vessels, a small quantity of carbonate of ammonia will be disengaged indicat- ing the presence of nitrogen. 1189. The Sulphate of Quina is the most important compound of this vegetable alkali, and is preferred for medical purposes to the quina itself, as it possesses all its virtues, while its solubility enables it to act more powerfully and uni- formly, quina being very sparingly soluble in water, though it is readily dissolved by alcohol and ether. It has an intense- ly bitter taste, similar to that of pure quina. 1190. The method of preparing sulphate of quina, though usually considered a difficult process by the beginner, may be easily conducted on the small scale in the following manner : Reduce half a pound of yellow bark (1181) to a very coarse powder, (or bruise it in a mortar), boil it for twenty minutes in a large earthen evaporating bason, (heating it over a fur- SULPHATE OF QUINA. 387 nace or chauffer), with four or five pints of water acidulated with half an ounce by measure of sulphuric acid. Strain the decoction through a large woollen or linen cloth ; return the bark and boil it again with the same quantity of water and acid, straining it as before and washing it afterwards with a little water. The decoctions are then to be mixed, and slaked lime in fine powder added to them till the liquid assumes a dark colour, and a precipitate begins to appear, leaving a clearer liquid above. This is the first stage of the process, and when the bark is good, about two ounces of lime are in general required to produce the effect described. The bark contains the quina in combination with kinic acid, a peculiar vegetable acid with which it is generally associated, and by boiling it with the sulphuric acid and water, this salt is de- composed, the sulphuric acid combining with the quina, and forming sulphate of quina which remains in solution, along with the other matters that the bark contains which are solu- ble in water, the woody fibre being scarcely affected by the acid. In this manner then, we separate the quina from it, and the solution which we obtain contains essentially sul- phate of quina with a considerable excess of sulphuric acid which promotes its solubility in the water. When the lime is added, it combines with the excess of sulphuric, and also with the sulphuric acid of the sulphate of quina forming sul- phate of lime, and the quina now losing the sulphuric acid that retained it in solution is also precipitated. By filtration, the quina and the sulphate are separated from the liquid, which still retains most of the other matters in solution that were dissolved at first by the water. 1191. The next stage of the process consists in digesting the mixture of quina and sulphate of lime in alcohol, after it has been completely dried by exposure to a gentle heat on a sand bath, or by placing it on a plate before the fire. It should be reduced to powder for this purpose, and mixed intimately with a small quantity of alcohol in a mortar, after which four or five times its bulk of this fluid may be added, decanting the clear liquid that is obtained on allowing it to remain at rest for a short time after two or three hours' diges- 388 PREPARATION OF tJon, which should be repeated two or three times with fresh alcohol till it ceases to acquire a bitter taste. The alcohol dissolves the quina, and leaves the sulphate of lime, and by evaporating the mixed liquids, the quina is obtained sufficient- ly pure for the preparation of the sulphate. 1192. The alcoholic solution of quina should be evaporated in a glass retort, that the alcohol may not be lost, as it may be used repeatedly for the same process, and the evapora- tion must not be continued to dryness, as part of the quina would thus be decomposed, and give the rest a dark brown or black colour. When a considerable portion of the alcohol has been distilled over, the liquid boils irregularly, a violent ebullition taking place, which soon ceases altogether until it is again renewed as violently as before ; this may be in a great measure prevented by putting in small coils of platina wire, or of any solid matter that will not be affected by the liquid ; a few small pieces of iron wire do very well. None of these must be put in, however, while the ebullition is actually going on, otherwise a large quantity of vapour will rise imme- diately in the retort, and carry a portion of the liquid over into the receiver ; after allowing it to cool for a few minutes, the wire may be safely introduced. In general, the evapora- tion may be carried on till a quantity of solid matter begins to be deposited on the sides of the retort, which will appear some time after small globules of an oily looking matter are seen on the surface of the liquid, rolling about in a very sin- gular manner. On the large scale, the alcohol is usually distilled in a water bath, or by a pipe conveying steam made to pass through the interior of the still, but when only a small quantity of materials is employed for illustrating the nature of the process, this may be done more conveniently with a glass retort heated by a chauffer. 1193. If the distillation be stopped when the appearances that have just been described are seen, the fluid that remains in the retort will divide into two parts as it cools. The upper part is a bitter milky liquid, which has an alkaline reaction, turning the vegetable blues to a green ; and the lower part is composed of a viscid substance, which also contains a consi- SULPHATE OF QUINA. 389 derable quantity of quina. Both these may then be put into hot water, and sulphuric acid diluted with four or five times its bulk of water is to be added cautiously to the liquid till it is completely neutralized, using a small pipette for this purpose, and examining it constantly with a test paper, that no excess may be added. The solution of sulphate of quina thus pro- cured must be concentrated by evaporation, after which stel- lated crystals of the sulphate will be deposited as it cools. By mixing a little animal charcoal with the solution, the crystals may be obtained quite pure by the first crystallization. 1194. If the solution should not deposit crystals, but remain thick like gum water, by diluting it with a little water, and again heating it for a short time, the sulphate will be deposited in crystals ; they have a fine pearly lustre, are completely de- composed by heat, alkalis, and alkaline earths, the latter pre- cipitating quina from its solution in water. 1195. Sulphate of quina may be prepared without alcohol, by a process pointed out by M.M. Henry and Plesson, the details of which may be seen in the fourth volume of the Quarterly Journal of Science. 1196. Heat some sulphate of quina in a glass bottle, by putting it cautiously into hot water. It will assume a phos- phorescent appearance, a pale light being evolved. 1197- Sulphate of quina bearing a very high price, it is frequently adulterated with a variety of substances. Earthy matter may be detected, by exposing it to a red heat, when all the sulphate of quina will be decomposed or volatilized, no- thing remaining but the earthy matter with which it may have been mixed. 1198. It has lately been adulterated to a considerable ex- tent with stearine, one of the component parts of most fatty matters, and which bears a considerable resemblance in its ex- ternal appearance to this salt. They are easily separated, however, by digesting the mixture in water acidulated with sulphuric acid, a sulphate of quina with excess of acid being formed, which is very soluble, and is dissolved by the water, while the stearine is left, and may be melted into a greasy fluid by a gentle heat. 390 CINCHONIA— -KINIC ACID. 1199- Sulphate of quina is also occasionally adulterated with sugar, which may be detected in the following manner. Dissolve the suspected sulphate in water, and add a solution of the subcarbonate of potassa, which will immediately preci- pitate the quina ; filter the liquid, evaporate it, and digest the residuum in alcohol. If any sugar should have been mixed with the sulphate, it will be dissolved by this fluid, and its amount may be ascertained by evaporating the" liquid. 1200. Acetate of Quina may be prepared in the same manner as the sulphate. Oxalate, Tartrate, and Gallate of Quina, may be obtained by mixing solutions of the oxalate, gallate, and tar- trate of potassa, with a solution of sulphate of quina. They are all insoluble in cold water, but soluble in hot water and in alcohol. CINCHONIA. 1201. This vegetable alkali may be prepared in the same manner from the pale bark as quina is procured from the yel- low bark, and bears a great resemblance to it in all its leading properties. It differs from it principally in being easily crystallized, in the quantity of acid which it can neutralize, and in a number of other minor circumstances. It is said to be composed of the same elementary substances as quina, but contains no nitrogen, according to Mr. Brand's analysis. KINIC ACID. 1202. This acid may be procured in combination with lime by the spontaneous evaporation of the liquid obtained by the maceration of bark in water. Oxalic acid separates the lime when added to it, and the kinic acid may be obtained in crys- tals by evaporation. 1203. Pour an infusion of galls into a decoction of bark, a copious precipitate will appear, the gallic acid which it contains STRYCHNIA. 391 uniting with the alkali and forming insoluble gallate of quina or cinchonia. If, however, the alkali has been extracted from the bark before the decoction with which the experiment is made shall have been prepared, little or no precipitate will be thrown down. An infusion of galls, therefore, may be used with advantage for distinguishing between good and bad va- rieties of bark. Sect. III. — Strychnia. 1204. This vegetable alkali is usually prepared from nux vomica, in which it exists in combination with a peculiar ve- getable acid which has received the name of Igasuric acid, mixed also with a little brucia, (another vegetable alkali,) gum, colouring matter, a fatty matter, and woody fibre ; the following is the method of procuring it. The nux vomica is to be bruised in a mortar and macerated in successive por- tions of water, and the liquid evaporated to the consistence of an extract after it has been filtered ; the igasurate of strychnia will be dissolved and the solution will also con- tain a portion of gum, colouring matter, fatty matter, and bru- cia. By digesting the extract in alcohol, the gum will be se- parated while the other substances will be dissolved ; and by evaporating the alcoholic solution to the consistence of an ex- tract, and macerating it in cold water, the fatty matter will be left undissolved. The solution is then to be heated, and an excess of lime water added to it. The strychnia and brucia will be precipitated along with the colouring matter, and on macerating the precipitate in weak alcohol, the brucia and colouring matter are dissolved, while the strychnia is left. If the strychnia be then dissolved in hot alcohol, minute crystal- line grains of strychnia will be deposited as it cools. 1205. Strychnia possesses the usual properties of a vege- table alkali, and has an intense bitter taste. It is one of the most powerful narcotic poisons belonging to the vegetable kingdom. 392 OILS, ItESINS, &c. CHAP. IV. OILS, RESINS, &c. 1206. Steep some almonds in hot water, and bruise them in a mortar after peeling them ; then compress the almond paste in a strong linen bag, when a considerable quantity of a clear and colourless oil will be obtained. All the common fixed or expressed vegetable oils are prepared in a similar manner. 1207. Expose a small quantity of a fixed oil to cold by a freezing mixture ; part of it will soon consolidate, and a thinner part remain above. The solid part is called Stearine and the fluid portion Elain, and Chevreul has shown that all fixed oils and fats are composed of these two principles. The stearine is obtained pure by compressing fat between folds of bibulous paper so as to remove the elain. 1208. Soak some cotton in linseed oil, and put it aside af- terwards in a safe place, where it cannot do any harm if it should take fire. The oil absorbs oxygen from the air, and being spread over an extensive surface on the fibres of the cotton, a considerable degree of heat is produced, and fre- quently it takes fire in the course of a day or two. 1209- Mix some sulphuric acid with half its bulk of a fixed oil ; the mixture will immediately become black, and a con- siderable quantity of sulphurous acid will soon be disengaged. 1210. Mix some nitric acid with another portion of the same oil in a deep glass, taking care to avoid the sparks that are thrown out. A more violent reaction will take place than in the preceding case, and a large quantity of gaseous matter be disengaged. 1211. Mix some castor oil and alcohol in a glass or bottle, shaking them together ; they unite in any proportions, and form a transparent and colourless liquid. None of the other fixed oils are soluble in alcohol. Throw some of the above compound into water ; the alcohol will combine with the wa- ter, and the oil will be set at liberty. OILS, RESINS, &C ?> ( ,VS 1212. Expose some linseed oil to the air for some time ; the mucilaginous matters which it contains will be decompos- ed, attracting oxygen and acquiring acid properties. Linseed oil may be converted into a drying oil in this manner ; the same object may be effected more speedily by exposing it to heat in an open vessel. 1213. Expose a quantity of some fixed oil to heat in a re- tort, over a good chauffer, collecting the liquid products in a receiver. A large quantity of inflammable gaseous matter will be disengaged, and a thin empyreumatic oily liquid will condense in the receiver, very different from the fixed oil sub- jected to distillation. 1214. Mix one part of the water of ammonia and eight parts of olive oil. A soap or liniment will be immediately formed, called oleum ammoniatum by the Edinburgh Col- lege. 1215. By boiling oil with a solution of potassa or soda, soaps of different kinds may be obtained, the potassa giving a soft, and the soda a hard soap. From the recent experiments of Chevreul, it appears that the alkali does not combine di- rectly with the oil, but that the latter is decomposed, the stearine and elain being converted into what are now termed margaric and oleic acids, which form soap by uniting with the alkali. Good soap is not easily prepared on the small scale ; if the student should still wish, however, to make a little, he must take care to shake the vessel frequently, as it does not boil in a regular manner, and the materials are apt to be thrown out when this is not attended to. 1216. Digest some soap in alcohol ; a solution is obtained which is frequently used as a test for the presence of earthy salts in water ; by distilling the greater portion of the alcohol, and allowing the residuum to consolidate, transparent soap may be easily obtained. 1217. Make a solution of soap in water, and pour in a little sulphuric or muriatic acid. The alkali of the soap will unite with the acid, and the oil will be disengaged. 1218. Pour a little of the solution of soap in alcohol into a glass of distilled water. The solution of the soap will diffuse 394 OILS, RESINS, &C. itself through the water, which will remain quite transparent and colourless. 1219- Add some of the solution of soap in alcohol to a glass of water, in which a little of the sulphate or muriate of lime has been dissolved. The acid in combination with the lime will unite with the alkali of the soap, forming a salt which will remain in solution, and oil or rather the margaric and oleic acids will unite with the lime, an imperfect soap being pro- duced, insoluble in water, which is deposited in the form of a white curdy precipitate. Similar experiments may be made with a solution of soap and other soluble earthy salts, and also with solutions of most of the metallic salts. 1220. Fixed oils combine also with oxide of lead, forming thick tenacious compounds or plasters. In preparing them, the oxide of lead should be reduced to a very fine powder, and exposed to heat with the oil and water till they have com- bined into a mass of a uniform consistence. The combination may be effected by heating the mixture without water, but then a portion of the oil is almost always decomposed from the high temperature which the materials are apt to acauire when no water is used, and the compound has a black colour from a portion of carbon which is disengag- ed. They may be obtained of various degrees of consistency by mixing them with different proportions of wax and resin. 1221. Put ten or twelve grains of phosphorus into a Florence flask with three or four ounces of olive oil, and digest the mix- ture for some time with a very gentle heat. Part of the phos- phorus will be dissolved, and the oil will appear luminous in the dark whenever it is exposed to the air, the phosphorus combining with the oxygen of the air. 1222. Pour a little oil of turpentine and fixed oil on two pieces of paper, and expose them to heat before the fire. The oil of turpentine will soon be volatilized, and no stain will be left upon the paper, but the fixed oil will not disappear unless the paper be exposed to a temperature sufficient to destroy it. 1223. Mix a small quantity of any of the volatile oils with three or four times its bulk of water, and expose the mixture OILS, RESINS, &C. 305 to heat in a glass retort placed over a chauffer, condensing the product in a receiver kept cold by water. The volatile oil will rise in vapour at the same temperature as the water, and collect in the receiver, although, when distilled alone, they in general require a temperature upwards of 300 to volatilize them. 1224. The sulphuric and nitric acids act violently upon the volatile oils, and all experiments made with these substan- ces must be cautiously performed. Considerable heat gener- ally accompanies the action, a large quantity of gaseous mat- ter is suddenly extricated and the mixture often inflames. Mix one drachm of sulphuric acid by measure with four drachms of strong fuming nitrous acid (186) in a glass, tied to one extremity of a stick or iron rod at least three feet long, and pour the mixture upon two drachms of oil of turpentine placed in a small cup or evaporating bason under the chimney ; the turpentine will be immediately inflamed, and a large quan- tity of gas will be disengaged. 1225. Pour a little oil of turpentine over a piece of paper, put a small crystal or about a grain of the powder of chlorate of potassa on a part of the paper over which the turpentine has been poured, and touch it with a glass rod dipped in sul- phuric acid. Sulphate of potassa is formed, and peroxide of chlorine disengaged, which immediately causes the oil of tur- pentine to take fire. 1226. Transmit a current of muriatic acid gas (prepared from chloride of sodium and common sulphuric acid without the addition of any water) through oil of turpentine placed in one of the bottles of Wolfe's apparatus, and kept cold by being immersed in a mixture of snow and salt. The oil of turpen- tine will condense about a third of its weight of muriatic acid gas, and a solid crystalline compound will be obtained, similar in its general properties to camphor. 1227- Dissolve camphor in alcohol, and pour the solution into water. The alcohol -will combine with the water, and the camphor will be precipitated. When camphor is to be reduced to powder, a few drops of alcohol added to it enable it to be easily pulverized. 396 FIBRINE. 1 228. Expose some common resin to heat in an iron cup ; it will soon melt, and by increasing the heat it will be com- pletely decomposed, a large quantity of gaseous matter being disengaged which burns with a rich flame producing a large quantity of smoke, and leaving a small quantity of a black matter composed principally of carbon. 1229. Reduce some resin to powder, and throw a spoonful of it into a deep glass containing an ounce of nitric acid. A large quantity of ruddy vapours will be disengaged, more dense and of a deeper colour than are usually evolved by the action of inflammable substances or metals on this acid. 1230. Dissolve some resin in alcohol, and throw the alcoholic solution into water ; a copious precipitate will be thrown down immediately, the water combining with the alcohol which had dissolved the resin and separating it. CHAP. V. ANIMAL SUBSTANCES. Sect. I. — Fibrine. 1231. Fibrine may be easily procured in a pure form by pouring off the serum from coagulated blood, and washing the crassaiiientum in a linen or cotton bag with a large quantity of water till all the colouring matter is carried away ; the fibrine remains of a white colour with a tint of yellow which is more apparent in some kinds of fibrine than others. It may be obtained in a state of sufficient purity for all ordinary pur- poses by cutting muscular fibre to small pieces and washing it repeatedly with water. 1232. Put some fibrine into alcohol of the specific gravity of 0.80, and set it aside for several weeks ; the fibrine is slowly converted into a fatty matter, which is dissolved by the alco- hol, and may be precipitated again from its solution by water. FIBRINE. 397 1233. Put some muscular fibre into a wooden box with holes in it, and place it where it will be exposed to a stream of water for two or three weeks ; a change will take place similar to what is effected by the alcohol, the fibrine being converted into adipocere. 1234. Fibrine may be easily converted into a fatty matter by the action of diluted nitric acid. Mix three or four ounces of nitric acid with one and a half times their weight of water, and expose the liquid to heat over a chauffer with two or three parts of muscular fibre. Nitrogen gas v/ill be disengaged, not mixed with any nitric oxide at first, and appearing to arise solely from the decomposition of the fibrine, In a short time however, the acid itself will begin to be decomposed, a large quantity of fatty matter will be formed, and nitric oxide and vapours of nitrous acid will be evolved. The nitrogen disen- gaged in the first stage of the process may be collected, if re- quired, by heating the mixture in a glass retort, the beak of which is introduced under the surface of water in a pneumatic trough with jars arranged in the usual manner. 1235. Pour some concentrated acetic acid over fibrine in a Florence flask, and allow them to remain mixed together for some time ; the fibrine gradually softens, and on exposing it to a gentle heat, it will be dissolved, and a gelatinous mass ob- tained, which is soluble in water ; the fibrine appears, however, to be partially decomposed as a little nitrogen gas is disengag- ed during the solution of the jelly in water. 1236. Put some fibrine into a solution of potassa or soda at ordinary temperatures, and allow them to remain mixed to- gether. The fibrine will be slowly dissolved, and may be pre- cipitated again from the solution by neutralizing the alkali with an acid. Sect. II. — Albumen. 1237 Put a piece of blue test paper (1129) into the white of an egg, and it will soon turn green, the albumen and water of which it is almost entirely composed containing a portion of 398 ALBUMEN. free soda. A similar experiment may be made with the serum of the blood, which also is composed principally of water and albumen with a little free soda. 1238. Expose some of the white of an egg or the serum of the blood to a temperature which need not exceed 160 ; in a short time it will be converted into a firm coagulum. Mix some albumen with a considerable quantity of cold water, and expose it afterwards to heat ; the albumen will be coagulated and the water will, become opaque even though the liquid should not contain more than i^ooth part of albumen. J 239- From the property which albumen has of being miscible with cold water while it is coagulated by hot water, it is used in many chemical operations for clarifying saline solu- tions which do not coagulate it at natural temperatures. For this purpose, the albumen is added to the liquid to be clarified while cold, and on exposing it to heat, the albumen coagulates slowly as the temperature increases, forming a kind of net- work which envelopes the dust and any other extraneous mat- ters which the liquid may contain, and collecting as a scum at the surface which is easily removed. 1240. Put the white of an egg into a Florence flask and pour an ounce or two of sulphuric acid upon it ; the albumen will be immediately coagulated, and on applying a gentle heat, it will be completely dissolved ; it is partly decomposed, how- ever, at the same time, and the liquid assumes a very dark co- lour having a purple tint. When the heat is very carefully applied, Dr. Hope found that the liquid becomes of a very beautiful red colour, which may be regarded as one of the characteristic properties of albumen. 1241. Mix the white of an egg with a considerable quanti- ty of water, and pour the liquid into a number of glasses ; then add a solution of the bichloride of mercury to one ; a solution of the subacetate of lead to another, and a solution of several other metallic salts to the rest. The albumen will decompose the solutions of a great number of metallic salts, combining with the metallic oxide and forming an insoluble compound which is precipitated. With the bichloride of mercury, again, the precipitate that is thrown down is regarded as a compound ALBUMEN. 399 of the protochloride of mercury and albumen, and smaller quan- tities of albumen may be detected in this manner than in any other way, a single drop of a saturated solution of the bichlo- ride rendering water turbid when it contains only a 2000th part of albumen in solution. 1242. Add an infusion of galls to a similar solution of al- bumen in water, a copious precipitate will be immediately thrown down, composed of albumen and tannin. 1243. Expose an ounce or two of the serum of the blood to a very gentle heat till it is coagulated ; cut the coagulum into small pieces and put it on a filter. A watery fluid (usually termed the Serosity) will exude, which may be separated easi- ly by pouring more water on the coagulum, and which con- tains in solution the greater part of the salts of the blood ; muriatic acid may be easily detected in it by a solution of the nitrate of silver, which gives a copious white curdy precipitate with this liquid. Sect. III. — Gelatine. 1244. Dissolve one part of dry gelatine in a 100 parts of hot water, and a liquid will be obtained which will become a tre- mulous jelly when cold. Add an infusion of galls to a solu- tion of gelatine in water ; a copious precipitate will be imme- diately thrown down, composed of tannin and gelatine, similar in its composition to leather. 1245. Add a solution of the bichloride of mercury to a so- lution of gelatine and albumen as long as any precipitation takes place ; the albumen will be precipitated and the gelatine will remain in solution ; it may be removed afterwards by a solution of tannin. If the tannin be added to the liquid con- taining the albumen and gelatine before precipitating the for- mer by bichloride of mercury, both the albumen and the ge- latine will be thrown down in combination with it. 1246. For all ordinary experiments where gelatine is re- quired, common glue will be found to do very well ; where it is necessary to have a purer gelatine, isinglass should be employ- 400 OSMAZOME. CHOLESTERINE* ed. It may be procured by boiling animal substances in water, and evaporating to dryness. Sect. IV. — Osmazome. 1247. This proximate animal principle may be obtained by macerating muscular fibre in cold water, evaporating the liquid procured in this manner to the consistence of an extract after separating the coagulated albumen, and digesting it into alcohol. The water dissolves the albumen, osmazome, and saline matter which are associated along with fibrine in the muscular fibre ; the albumen is coagulated by the heat, and the osmazome is separated by the alcohol from the extract ob- tained on evaporation, being soluble both in water and alco- hol. Its solution does not gelatinize on cooling. Sect. V. — Miscellaneous Experiments, illustrating THE METHOD OF EXAMINING THE MOST IMPORTANT VA- RIETIES of Calculi. 1248. Cut one or two biliary calculi into small pieces, tritu- rate them afterwards in a mortar, and boil them for ten minutes in a test tube or small flask, with twenty times their bulk of alcohol. On filtering the solution, a clear and colourless li- quid is usually obtained, which deposits pearly looking crystals of Cholesterine as it cools. If the solution be very strong, a layer of cholesterine will be left upon the paper by the alco- hol as it passes through, and on drying the filter and bending it backwards, it may be detached in the solid form, still retain- ino 1 the figure of the filter on which it had collected, and ha- vino- the appearance of a fine membrane with a pearly lustre. 1249. In preparing cholesterine from biliary calculi, it is necessary to filter the solution as speedily as possible, as this substance is very sparingly soluble in cold alcohol, and a great portion of it is deposited on the filter in operating with small quantities if this precaution is not attended to. EXAMINATION OF CALCULI. 401 1250. Reduce a portion of a Umc Acid calculus to pow- der, and digest it in a diluted solution of potassa. Urate of potassa will be formed and remain in solution, while any phos- phate of lime or phosphate of ammonia and magnesia that may have been mixed with it will remain undissolved. 1251. Filter the solution of urate of potassa prepared in the manner described in the preceding paragraph, and add acetic acid to it as long as any precipitation takes place. The acetic acid combines with the potassa and uric acid is precipi- tated in very small crystals. 1252. Mix some uric and nitric acids, and expose the mix- ture to a gentle heat till it becomes dry, taking care not to al- low the temperature to become so high as to decompose the products ; a solid mass is obtained of a deep red colour. When a very small quantity of materials is employed so as to leave only a very thin pellicle on the surface of the glass on which it is heated, it has a vivid pink colour. 1253. Expose a small piece of a uric acid calculus to heat in a platina spoon held in a flame of a spirit lamp ; it soon blackens and emits a fetid odour, and in a short time it en- tirely disappears, when composed of nothing but uric acid ; in general, however, an ash-coloured matter remains, composed of some of the saline substances, that form a number of other calculi, and occur in variable proportions in the uric acid cal- culus. 1254. The Urate of Ammonia calculus is comparatively rare ; and till lately the formation of calculi of this kind was disputed. It may be easily distinguished from the uric acid calculus, however, when not mixed with a large quantity of uric acid, by its greater solubility in water, its clay colour, the ammoniacal odour which is exhaled when gently heated with a strong solution of potassa, and its solubility in solutions of the carbonates of potassa and soda, which do not dissolve pure uric acid. 1255. The Oxalate of Lime, or mulberry calculus, is in general easily known by its rough tuberculated surface, and its chemical composition may be easily proved by a few simple experiments. 2d 402 EXAMINATION' OF CALCULI. 1256. Expose a portion of this calculus to heat over a spirit lamp, holding it in the flame till nothing remains but a grey coloured ash ; it will become black at first, and the residuum will be found to be composed of carbonate of lime, dissolving with effervescence in muriatic acid, and forming a solution of muriate of lime, with which the experiments described in 67O, 671, 672, &c. may be performed, after neutralizing any excess of acid by an alkali. 1257. Place another portion of this calculus on a piece of charcoal, and expose it to a strong heat before the flame of the blow-pipe ; nothing will remain but caustic lime, which will slake in the usual manner, and render turmeric paper brown, and paper tinged with the blue infusion of cabbage green, on rubbing it on them with a little water. 1258. If it be required to show the presence of the oxalic acid in the calculus, it must be reduced to a fine powder, and digested with a very gentle heat in diluted sulphuric acid ; sulphate of lime will be formed, and oxalic acid will be found in solution. In general, however, this process may be dis- pensed with. 1259. Reduce a portion of the Phosphate of Lime or Bone Earth calculus to powder, and digest it in diluted nitric or muriatic acid. In a short time it will be completely dis- solved ; and if the acid be neutralized by an alkali, it will again be precipitated. 1260. Expose another portion of this calculus to heat be- fore the flame of the blow-pipe ; it will soon become black from the decomposition of a little animal matter with which it is always mixed, and the separation of part of the carbon ; this will soon be burnt off, however, and nothing will remain but the phosphate of lime of a pure white colour, which docs not suf- fer any farther change unless it be exposed to a very intense heat, by which it may be fused. 1261. Digest another portion of this calculus in a solution of potassa after reducing it to powder ; if it consist solely of phosphate of lime, no reaction will take place, phosphate of lime being insoluble in a solution of potassa ; but if any uric acid should have icon mixed with it, urate of potassa Mill be EXAMINATION OF CALCULI. 403 found ill the solution, from which the uric acid may be pre- cipitated by an acid. 1262. Uric acid may be detected also in calculi composed principally of phosphate of lime by evaporating its solution in nitric acid to dryness in the manner described in 1251, when the characteristic red tint will appear, though only a very minute quantity of this substance should have been present in the calculus. There are few urinary calculi, which do not give traces of uric acid when treated in this manner, whatever may be the nature of the ingredient of which they are princi- pally composed. 1263. When the calculus is supposed to consist of Phos- phate of Ammonia and Magnesia, this may be easily ascertained by heating a portion in a solution of caustic po- tassa after reducing it to powder, when ammonia will be dis- engaged, the phosphoric acid in combination with it uniting with the potassa ; and by treating another portion with cold acetic acid, the phosphate of ammonia and magnesia will be dissolved, leaving the greater portion of any phosphate of lime that may have been mixed with it. 1264. When the calculus is composed of a mixture of phosphate of ammonia and magnesia and phosphate of lime^ it fuses readily before the blow-pipe, and hence it is usually termed the Fusible Calculus. 1265. The Cystic Oxide calculus is easily distinguished from all the preceding varieties of calculi by its solubility in solutions of acids, alkalis, alkaline carbonates and in lime water ; it is also completely decomposed by heat 5 being composed of the usual elements of animal matter. 1266. The Xanthic Oxide calculus is so rare that few students can expect to have an opportunity of operating with it. It is distinguished by the lemon yellow coloured residuum that is left on exposing its solution in nitric acid to heat. The Fibrinous Calculus is still more rare, and is composed en- tirely of fibrinc 404 ULTIMATE ANALYSIS OF VEGETABLE CHAP. VI. EXPERIMENTS ILLUSTRATING THE PRINCIPLE ON WHICH THE PRESENT IMPROVED PROCESS FOR THE ULTI- MATE ANALYSIS OF VEGETABLE AND ANIMAL SUB- STANCES DEPENDS. 1267- Though the exact analysis of animal and vegetable substances is a process far too complicated for the beginner, and requires a knowledge and dexterity of manipulation that can be acquired only by long practice, it may be interesting for him to imitate the process, that he may see a practical il- lustration of the principle on which it depends. The two fol- lowing experiments will be sufficient for this purpose, and they may be performed easily by the beginner. 1268. Mix five grains of sugar with 50 grains of the per- oxide of copper prepared by decomposing the nitrate of copper by heat ; (See 811.) Put this mixture into a glass tube about six or eight inches long, and a third of an inch in diameter ; then join to the extremity a smaller tube, bent in Fig. 65. the manner represented in the figure, making the joining tight with plaster of Paris, protecting g^H3T~ ~\^f ^ by tying a piece of Unen round it after covering it with a little clay made up with mucilage, and securing the whole with some stout thread. The extremity of the tube containing the mixture is then to be coated with clay, and wrapped round with harpsichord wire, after which it may be put into a chauffer with an aper- ture at the side, placing the extremity of the small tube under mercury, and holding over it another tube closed at one end previously filled with mercury that the gas disengaged may be collected in the same manner as in a jar over the mercurial AND ANIMAL SUBSTANCES. 405 trough ; this tube need not be above ten or twelve inches long, nor more than half an inch in diameter, so that the operator may hold it easily in one hand while he directs the extremity of the tube from which the gas is escaping with the other. He should also have a tin plate to protect his hand from the heat of the chauffer, and a chimney to increase the tempera- ture if the chauffer should not burn well. 1269. If it be required to collect more than one tube of gas, the other tubes to be used should be filled with mercury before commencing the process, and arranged in another cup containing this fluid, supporting them at the top within the ring of a retort stand. He will thus be enabled to remove each tube as it is filled with gas into this cup, closing it com- pletely with his thumb as he transfers it from the one to the other, and replacing it by a tube full of mercury which must be taken in the same manner to the first cup to be filled with gas as in the preceding instance. 1270. The pressure which the gas that is disengaged has to overcome in rising through the mercury being about thirteen times greater than it meets with in rising through a column of water of the same height, the two tubes which are joined together must be luted with great care ; the student who has attended to the method of adjusting tube apparatus may save himself the trouble of attaching another tube to the one con- taining the mixture, by bending and drawing out the extremity p. 66 till it is obtained of the form represented in the annexed figure ; this must not be done, however, till the mixture has been in- troduced, as it would be troublesome to pass it through the small aperture at the extremity, which need not exceed the sixteenth part of an inch in diameter. 1271. When the gas ceases to come, a few drops of a solu- tion of caustic potassa may be introduced into one of the tubes filled with gas under the surface of the mercury by means of a pipette ; in a short time it will be completely absorbed, if all the atmospheric air shall have been allowed to escape before col- lecting any gae, nothing being produced by the decomposition but carbonic acid and water, and the latter being deposited in 406 MISCELLANEOUS EXPERIMENTS. the tube ; the quantity of water is ascertained in delicate ex- periments by placing chloride of calcium in fragments within part of the apparatus through which the carbonic acid is made to pass, this substance having a great affinity for water, and retaining it in combination ; the weight which it gains during the operation denoting the quantity of water produced. 1272. The theory of the process will be readily understood from what has been stated in 1107. The sugar being com- posed of carbon, hydrogen, and oxygen, the only products are carbonic acid and water, the peroxide of copper supplying the additional quantity of oxygen necessary to convert all the carbon and hydrogen into carbonic acid and water. By weighing, then, the carbonic acid, we may ascertain the quan- tity of carbon, every 22 parts indicating the presence of 6 of this element ; 9 parts of water denote the presence of 1 of hydrogen ; and by comparing the quantity of oxygen which these products contain with the weight of the sugar employed and the quantity of carbon and hydrogen which it has been found to contain, we may easily ascertain the proportion of oxygen : the latter may be found out also by comparing the quantity of oxygen in the carbonic acid and water with the loss of weight which the peroxide has sustained. 1273. For the second experiment alluded to, the beginner may mix intimately five grains of dried gelatine with fifty grains of peroxide of copper, covering the mixture with an ad- ditional quantity of the peroxide after putting it into the tube, and then proceeding in the manner directed in the preceding experiment. It will be better, however, to heat the part of the tube containing the peroxide of copper put over the mixture in the flame of a spirit lamp before putting the coated extre- mity into the chauffer, the peroxide heated in this manner de- composing any oily matter or impure carbonate of ammonia that is sometimes disengaged before the rest of the peroxide is heated sufficiently to afford it oxygen with facility. In this process, carbonic acid, water, and nitrogen are the only pro- ducts, the two first being formed in the same manner as in the preceding process, while the nitrogen is disengaged and is col- lected in the tube along with the carbonic acid. On intro- MISCELLANEOUS EXPERIMENTS. 407 during a solution of caustic potassa, the whole of the carbonic acid gas will be absorbed, and the residual gas will be found to be nitrogen, being uninflammable, not supporting combus- tion, and giving no precipitate with lime water. 1274. When a number of experiments of this kind are to be performed, a copper tube will be found more convenient, which may be conveniently heated by a number of spirit lamps ; but for the above experiments, a coated glass tube will be found quite sufficient : green glass tubes should be preferred as they are not so apt to soften and give way when exposed to a red heat, 408 FART II CHAP. I Description of an improved sliding scale of chemical equivalents, with directions for using it, and a copious table of chemical equivalents.* 1275. Since the existence of chemistry as a science, no principle has been pointed out so broadly connected with the whole range of its investigations, as the doctrine of Definite Proportions. It embodies not only some of the most brilliant discoveries, but also many of the most useful practical appli- cations of the science, and has enabled us to reduce to a more systematic form, the accumulated mass of facts which it now embraces. 1276. It is not therefore surprising, that it should have effected a very important change in the character of the science, and been so assiduously cultivated by every eminent chemist of the present day. Scarcely, indeed, have twenty * This explanation, and the general Tahle of Equivalents, were published several years ago along with the Scale ; they have now been revised and en- larged to adapt them to the present state of Chemical Science. CHEMICAL EQUIVALENTS. 409" years elapsed since Mr. Dalton made known his Views of Che- mical Combination, and though they were blended with an ingenious hypothesis, concerning the atoms or ultimate par- ticles of matter which has not been universally adopted, they now form the basis of every scientific work on chemistry. 1277* Dr. Wollaston soon appreciated the importance of the laws pointed out by Mr. Dalton, and founded on them his Scale of Chemical Equivalents, one of the most valuable in- struments which has been invented for assisting the analytical researches of the practical chemist, and facilitating the study of the most important laws and facts of chemical science. Dr. Thomson, in his late work, has observed, that to it we owe, in a great measure, the general adoption of the views of Mr. Dalton in Great Britain. It is one of those happy inventions, which by a singular felicity of adaptation, condenses, in one- view, a vast mass of information, and it is quite invaluable to the practical chemist, saving him a multiplicity of calculations which must otherwise engross a large portion of his time ; while, from the present state of chemistry, it is no less useful to the student, exhibiting, in the most striking manner, many of the most important relations of the science, and rendering him familiar, by mere inspection, with a wide range of Che- mical Combinations. 1278. To render it as extensively useful as possible, a great many additions have been made, while, at the same time, it has been very much simplified, by taking hydrogen as a stand- ard of comparison, instead of oxygen, by which fractional num- bers are avoided, formerly a source of very great inconveni- ence. 1279. In order to explain satisfactorily the nature of the scale, we shall, in the first place, give a brief sketch of the chemical principles on which it is founded, then explain the manner of using it, and subjoin, for the sake of reference, a table of the Chemical Equivalents of the different elements, and their most important compounds, exhibiting at the same time their atomical constitution. 1280. The doctrine of definite proportions is the term which 410 IMPROVED SLIDING SCALE has generally been employed to express the laws implied in Mr. Dalton's Atomic Theory. It includes three general pro- positions, each of which will be separately considered. 1281. The first of these propositions is, that bodies combine in certain fixed or definite proportions. Thus, 36 parts of chlorine combine with 1 of hydrogen, and form 37 of muriatic acid ; and 84 parts of zinc combine with 8 of oxygen ; but these bodies do not combine in any other proportion. 1282. There are many substances which can combine in more than one determinate proportion ; but no combination can be formed intermediate between these : the only com- pounds which copper and oxygen form with each other, are in the proportion of 64 of the former with 8 or 16 of the latter. Mercury also can combine with oxygen in the proportion of 200 of the former with 8 or 16 of the latter,— but no other combination of these elements has been observed. 1283. These examples will serve to show the nature of the first proposition, which has been established by the rigorous analyses of the first chemists of the day. Berthollet, how- ever, maintained an opposite opinion in his elegant work on Chemical Statics, conceiving that bodies were disposed to unite with each other in any proportion between two certain points, that is, between the greatest and smallest quantities of any one substance which can combine with a given weight of any other, or, as it has been sometimes termed, between the maxi- mum and minimum of combination. The inaccuracy of his views on this subject is now universally admitted, and Proust was among the first who brought forward a series of experi- ments disproving them. 1284. We cannot pass over this proposition, however, with- out alluding to the well-known fact, that there are some cases where the combining substances can unite apparently in any proportion. This is very well exemplified in the case of water and alcohol, or water and sulphuric acid, and in the formation of metallic alloys. These have been regarded by some as com- pletely overturning the doctrine of definite proportions, but they have not usually been viewed in this light ; and the ap- OF CHEMICAL EQUIVALENTS. 411 parent combination of these different bodies, in unlimited pro- portions, is now generally considered as depending on the combination of a few definite compounds with each other. 1285. The second proposition included in the doctrine of definite proportions is, that when any two bodies are combined with a given weight of a third substance, and then brought into combination with each other, they combine together in the same proportion in which they had previously united with this third substance. For instance, one part of hydrogen combines with six of carbon, and eight of oxygen ; in what proportion, then, will carbon and oxygen combine with each other ? From the doctrine of definite proportions, we infer that they will combine with each other in the same proportion in which they combined with the hydrogen, or six parts of car- bon will combine with eight parts of oxygen. 1286. As this is an extremely important law, we subjoin the following table, which will place it perhaps in a still clearer point of view :— Olefiant gas consists of hydrogen 1+6 carbon. Water . . hydrogen 1+8 oxygen. Carbonic oxide . carbon 6 + 8 oxygen. Here we see plainly the remarkable fact, that carbon and oxygen unite together in the very same proportion in which they combine with hydrogen, and the same law extends throughout the whole series of chemical combinations.* Thus, 16 parts by weight of sulphur combine with 1 of hydrogen ; accordingly, we presume that the same quantity of sulphur will combine with 8 parts of oxygen ; for, as we have already seen, 8 parts of the latter combine with 1 part of hydrogen. On the same principle, we infer that 36 parts of chlorine will combine "with 8 of oxygen, both combining with the same quantity, viz. one part of hydrogen. * It may be necessary to observe, that this law applies only to the first com- bination which different bodies form with each other, when they unite together in more than one proportion. The reason of this will be easily understood when we have considered the next proposition. 412 IMPROVED SLIDING SCALE 1287- I n this manner we determine the combining quanti- ties of the different elements, and their compounds ; and, if we take any one of them as a standard of comparison, and number the rest in relation to it, we shall be able to perceive at one glance, the proportions in which different bodies com- bine with it, and also with each other ; for, according to the law we have just been illustrating, two bodies combine together in the same proportion in which they combine with a given Weight of a third substance. 1288. Dr. Wollaston introduced the term Chemical Equi- valent to denote the numbers representing the proportions in which different bodies combine together ; and, accordingly, if hydrogen be taken as a standard of comparison and reckoned Unity, carbon will then be represented by 6, oxygen by 8, sul- phur by 16, chlorine by 36, &c. and these numbers will ac- cordingly be styled their Chemical Equivalents. The Chemi- cal Equivalents of compounds, again, are represented by the numbers formed by the addition of the Chemical Equivalents of their elements ; thus, that of water is represented by the number 9, for it is composed of one equivalent of oxygen = 8, and one of hydrogen = 1.- 1289- We may likewise observe that many authors use the word atom to represent what others do by the terms Chemical Equivalent, Combining Quantity, Proportional, Prime Num- ber, &c. It matters little indeed which of them be employed, provided we annex the same meaning to them all, and perhaps the term atom is, after all, as convenient as any of the for- mer. 1290. Different chemists have assumed different standards in drawing up their tables of Chemical Equivalents ; oxygen, for example, being, at the present moment, represented by the different numbers, 8, 1, 10, and 100. Dr. Wollaston assume cd oxygen as a standard of comparison in his Scale of Chemi- cal Equivalents, and represented it by the number 10; and almost all the scales which have been made have been con- structed on this plan. A most important discovery, however, was made by Dr. Prout, who showed, that if hydrogen be taken as a standard of comparison, and reckoned one, all the OF CHEMICAL EQUIVALENTS. 413 other elementary substances, (with the exception of one or two, whose equivalents still form a subject of investigation), and consequently their compounds, will be represented by whole numbers ; whereas, according to the other system, many of them are represented by fractional numbers, which is extremely inconvenient. This singular fact will probably lead all che- mists ultimately to adopt hydrogen as a standard of compari- son, and, indeed, this has already been done in the leading phi- losophical journals of the day. 1291. We now come to the third proposition included in the Doctrine of Definite Proportions, which is, When one body combines with another in more than one definite proportion, the quantity of one of them, in the different combinations, will be found to be double, triple, or some simple multiple of the smallest proportion in which it combines with a given quantity of the other substance. Thus, if five parts be the smallest quantity of A which can combine with 100 of B, 10 parts will be the next, and so on in succession, as in the fol- lowing table : The First combination consists of - A 5 + 100 B Second - , - - A 10 -j- 100 B Third - - - - A 15 + 100 B Fourth - - - - A 20 + 100 B, &c. 1292. It is no doubt true that there are several cases which seem to be exceptions to this law, but it is extremely probable that these are only apparent exceptions, and arise from our not being acquainted with the whole series of combinations which are formed by any individual element. 1293. We shall now give one or two examples, which will show the nature of this law. Oxide of copper consists of oxygen 8+64 copper. Deutoxide .... oxygen 16 + 64 copper. Oxide of mercury . . oxygen 8 + 200 mercury. Deutoxide . . . oxygen 16 + 200 mercury. il4 IMPROVED SLIDING SCALE Nitrous oxide . . . oxygen 8 -f 14 nitrogen. Nitric oxide . . . oxygen 16 + 14 nitrogen. Hyponitrous acid . . oxygen 24 -f 14 nitrogen. Nitrous acid . . . oxygen 32 + 14 nitrogen. Nitric acid .... oxygen 40 -J- 14 nitrogen. 1294. Many more examples might have been given, but these are quite sufficient to show the nature of this law. We must remark, however, that in drawing up a table of chemical equivalents, or in consulting it, for the purpose of ascertaining the proportions in which different bodies combine, or the com- position of any compound, the student must take care to ob- serve, whether the compound consists of one atom, or chemi- cal equivalent of one substance united with one, two, or more atoms of another ; this can only be attained by a reference to the scale, or a knowledge of the different compounds which different substances form with each other. 1295- Before concluding this subject, we may remark, that an interesting discovery was made by Gay Lusac with regard to the combinations of gases. He found, that when they unite together, the bulk of the one always bears a simple ratio to the bulk of the other. Thus, half a volume of oxygen combines with 1 of hydrogen and 1 of nitrogen ; 1 volume of nitrogen again combines with 3 of hydrogen. It has also been ascer- tained, that when they unite in more than one proportion, the quantity of one of the combining substances is increased by some simple multiple of the smallest quantity of it which enters into the first combination. These general laws have received the appellation of the Theory of Volumes, and they agree strictly with the Doctrine of Definite Proportions, as will be seen clearly in the following table : Volumes. Atoms. Oxygen ...... 8 Hydrogen ..... D 1 Nitrogen □ 14 Chlorine □ 36 Here the first column represents the proportion in which these OF CHEMICAL EQUIVALENTS. 415 different gases combine with each other by volume ; while the second represents their chemical equivalents by weight : it is obvious, therefore, that the numbers in the last column indi- cate the comparative weight of the volumes of the different gases in the first column, and that one volume of oxygen will unite with two of hydrogen, two of nitrogen, and two of chlo- rine, in the first combination which it forms with these bodies, while hydrogen will combine with an equal volume of chlorine. These observations will serve to show the necessary connec- tion between the theory of volumes and the equivalents of dif- ferent substances by weight ; and the student will find it ne- cessary to study this subject in operating with gases. A num- ber of tables have been drawn up in which the composition of all the gases by weight and by volume are expressed in figures, which may be consulted with great advantage ; in the table which I have inserted after the general table of chemical equi- valents, the composition of a number of important compounds is stated with their equivalents both by weight and by volume. 1296. After having explained, in as brief a manner as pos- sible, the nature of the doctrine of definite proportions, the construction and manner of using the scale of chemical equi- valents will be easily understood. 1297- It consists of a table on which the names of the dif- ferent elementary substances, and their most important com- pounds are written ; the numbers representing their combining quantities, or chemical equivalents, being placed opposite them on a sliding rule, so that at one view we can see the propor- tions in which these different substances combine with each other. These numbers are so arranged with regard to each other, (being placed at particular distances from one another by means of a table of logarithms,) that we have always the same space between any two numbers which are at proportion- ate distances from each other. If we take a pair of compasses, for example, we shall find that there is the same space between 8 and 16, 16 and 32, 32 and 64, 64 and 128, &c. Or if we take the space between 10 and 20, we shall then find that there is the same distance between 20 and 40, 40 and 80, 80 and 160. In short, if we fix upon any number whatever on the 416 IMPROVED SLIDING SCALE scale, and take the distance of any number above it, we shall find that the number below, at the same distance, has the same proportion to the one first taken, as it has to the number above it. For instance, if we fix upon the number 12, and take any number above it, say 8, then at the same distance below 12 as 8 is above it, we shall find the number 18, but 18 : 12 : : 12 : 8. 1298. From these observations it will be easily perceived, that though the scale, as it is drawn up, represents the com- position of only one fixed quantity of any of the compounds which are written on it, we have only to shift the moveable slider on which the numbers are written, and then we can as- certain the composition of any quantity of any of the com- pounds, according to the length of the scale. 1299. For example, on looking at the scale, we see that 20 parts of magnesia consists of 8 of oxygen and 12 of magne- sium ; but if we wish to know the composition of 100 parts of magnesia, we have merely to shift the slider until the number 100 stands opposite magnesia, and then we see, on looking to oxygen and magnesium, that it is composed of 40 of the former and 60 of the latter ; oxygen and magnesium standing opposite these respective numbers, when 100 is opposite mag- nesia. 1300. Again, it is obvious, that as the scale is drawn up, it will not only show us the quantity of any salt which will de- compose one given quantity of another on which it may act ; but, by moving the slider, we may ascertain the quantity that will be required to decompose any given quantity of the second salt. Thus, on looking at the scale, we see that sulphate of pot- assa and muriate of barytes, are represented by the numbers 88 and 115 = 203 ; and these salts will accordingly be completely decomposed when they are mixed together in that proportion ; and, on examining the new-formed salts, sulphate of barytes and muriate of potassa, we find that there are 118 of the former and 85 of the latter, = 203, the quantity of materials originally operated on. If, however, we should wish to know the quantity of muriate of barytes requisite to decompose any quantity of the sulphate of potash, we have merely to move the slider till the number representing the quantity in qucs- 6 OF CHEMICAL EQUIVALENTS. 417 tion stand opposite the sulphate of potash, and then, on proceed- ing as before, we shall find the quantity of muriate of barytes necessary for the decomposition, the quantities of the new- formed salts, and the proportion of their different constituents. 1301. On looking along the scale, it will be observed, that some substances are represented two, three, or even more times, with the figures 2, 3, &c. prefixed. This is to show that these bodies can enter into combination with others in more than one proportion. Thus, we have seen that oxygen combines with many of the metals in more than one propor- tion ; 64 parts of copper, for example, combining with 8 or 16 of oxygen. Accordingly, opposite 72, we find the protox- ide of copper, indicating that it consists of 64 parts of copper and 8 of oxygen ; but lower down the scale, and opposite the number 80, we find the peroxide of copper. This contains exactly the same quantity of copper (64 parts,) as the 72 parts of the protoxide ; it must, therefore, contain 16 parts of oxy- gen, and opposite 16 we find 2 oxygen. The same observa- tions apply to water, and many other substances which enter into combination in more than one proportion. 1302. With regard to muriatic acid, it has been considered as a compound of hydrogen and chlorine, according to the views of Sir. H. Davy, and Gay Lussac and Thenard. The scale does equally well, whether we consider the compounds called chlorides, as compounds of chlorine and a metallic base, or of dry muriatic acid with a metallic oxide. For example, when a solution of the nitrate of silver is added to a solution of the muriate of soda, a white precipitate is obtained ; and, .supposing that it weighs 146 grains, it will be considered as a metallic chloride, according to the new doctrine, consisting of 110 grains of silver -f 36 of chlorine. Those, however, who maintain the old view of the constitution of muriatic acid, will legard it as a dry muriate, or a compound consisting of 28 parts of dry muriatic acid, and 118 of the oxide of silver.* * It may be necessary to remind those who are beginning the study of che- mistry, that muriatic gas is regarded as a compound of hydrogen and chlorine by those who regard chlorine as a simple substance ; those again, who do not, 2 E 418 IMPROVED SLIDING SCALE 1303. Again, according to the old doctrine, it is evident that the atom of dry muriatic acid will be represented by the number 28 ; for, according to this view of the subject, the muriatic acid gas, the equivalent of which is 37? (and which is commonly regarded as dry muriatic acid,) is considered as a compound of 1 atom of water = 9, with 1 atom of real muria- tic acid, but 37 — 9 = 28. Accordingly, whenever we wish to ascertain the quantity of muriatic acid in a salt, according to the old view of its constitution, we must refer to the num- ber 28, while those who are inclined to support Sir H. Davy's opinion, will consider 37 as the equivalent of the dry acid. These observations will also serve to show why the different metallic chlorides will still be represented by the same num- bers when they are considered as dry muriates, for we have seen, that, according to the old view of the constitution of mu- riatic acid, its atom is represented by 28, which is nine less than the atom of the dry muriatic acid of Davy. But when a muriate is converted into a chloride, the same weight of water is given off; for the 8 parts of oxygen combined with the base, unite with the hydrogen = 1 in muriatic acid, and form 9 parts of water. The following statements will be found use- ful in showing the constitution of muriatic acid and the metallic chlorides according to both views : 1304. According to the old opinion, 37 parts of muriatic acid gas consist of dry acid 28 + 9 water, and the real dry acid has never yet been obtained in an insulated state. When this is combined with 32 parts of soda, 60 parts of real muriate of soda are formed ; the 9 parts of water that were combined with the acid remaining in combination, and forming altogether 69 parts, but these may be expelled by heat, and then we shall obtain 60 parts of the dry muriate of soda, consisting of 28 acid + 32 soda. 1305. According to the other view of this subject, muriatic acid gas is itself the pure dry acid containing no water nor oxygen, and 37 parts consist of chlorine 36 + 1 hydrogen. regard it as a compound of water and real muriatic acid, which they maintain has never yet been obtained in an insulated state. OF CHEMICAL EQUIVALENTS. 419 These 37 parts combine with 32 of soda, forming 69 parts of real muriate of soda, and if this be exposed to heat, a decom- position will ensue, the 8 parts of oxygen contained in 32 of soda combining with the hydrogen, = 1 in the muriatic acid, forming 9 parts of water which are liberated, while the chlor- ine — 36 combines with the sodium = 24, and forms 60 parts of the chloride of sodium.* 1306. From the manner in which the numbers are placed with regard to each other, it is evident, that if the scale had begun with the number 1, it must have been prolonged to a very great length, as the distance between 1 and 8 must have been the same as between 8 and 64, (See 1296.) . To obviate this, and at the same time include those bodies whose chemical equivalents are less than 8, as hydrogen and car- bon, we begin with oxygen, which is represented by 8, and 10 atoms of hydrogen are represented by the number 10, while 2 atoms of carbon are represented by the number 12. Accordingly, whenever we are examining the constitution of any compound containing hydrogen or carbon, we must di- vide the number representing the former by 10, and the latter by 2, in order to ascertain the true quantity of these substances. Thus 14 parts of the oxide of carbon consist of 8 parts of oxygen, -f \ 2 parts of carbon = 6. Again, ole- fiant gas consists of 1 atom of carbon = 6 + 1 atom of hy- drogen, = 1. Its prime equivalent is therefore 7» but as the scale does not extend so low, 2 atoms of it are taken, = 14. We must accordingly always divide the number representing * In order to render the constitution of these compounds as easily under- stood as possible, I have, in general, stated their composition on the scale, both according to the new and the old view of the constitution of muriatic acid ; — the name of Sir H. Davy being annexed to the compound in the former case, and that of Dr. Murray in the latter, as they were great advocates of these different opinions. It is easy to Bee, from what has already been stated, that the dry muriate of Sir H. Davy will always be represented by a number exceeding the dry muriate, according to the old view, by 9, for the latter is synonymous with a metallic chloride ; and to convert it into a muriate, according to the general opinion of the day, we have merely to add an atom of water = 9, its hydrogen combining with the chlorine, and its oxygen with the metallic base of the chloride. 420 TABLE OF EQUIVALENTS. olefiant gas by 2, when comparing it with the other substan- ces on the scale. 1307- If? however, it should be an object to any individual chemist, to have a particular class of compounds arranged along the scale, which, in the present instance, may have been omitted in order to retain some of more general utility, he has merely to refer to the Table of Chemical Equivalents, where he will find the number by which they are represented according to the hydrogen scale, and write them on the mar- gin opposite the proper number on the sliding scale, and then their combinations may be investigated in the usual manner. 1308. It is necessary to observe that though hydrogen has been taken as the standard of comparison in the scale, any other substance may be substituted in its place. Thus if the student, or manufacturer, should prefer taking oxygen, as many do, and call it 10, he has only to shift the slider till that number shall have been placed opposite oxygen, and then he can proceed with the calculations as before. TABLE OF EQUIVALENTS. 1309- In this table of equivalents I have been induced to prefer a systematic to an alphabetical arrangement, as no table of equivalents has hitherto been published in this manner, and as it appears to me that it must tend more to facilitate the study both of theoretical and practical chemistry. With respect to the nomenclature of the different compounds, I have adopted those terms which will prevent the student from having any difficulty with respect to the precise nature of the materials required for the experiments, though in one or two cases, other terms might have been adopted with ad- vantage, were there not a considerable difference of opinion with respect to the most appropriate method of designating them. 1310. It is much to be regretted also, that it has not been customary to express the compositions of a number of impor- tant compounds in regular equivalent numbers, as it must prove very perplexing to the beginner to find them represent- TABLE OF EQUIVALENTS. 421 ed as being composed of an equivalent of one element and an equivalent and a-half of another, a mode of expression common in many of our best works on chemistry, and which general use forces us to adopt, though it is certainly very de- sirable that another mode of expression should be adopted consistent with what the student is taught when he com- mences the study of chemistry. The annexed table gives a corrected view of the composition of some of these com- pounds, which will enable the student to perceive the man- ner in which a series of equivalent numbers may be ar- ranged, consistent with the ideas usually attached to the term. The first line shows the constitution of the com- pound, as it is usually represented, and the second the cor- rected view. In the first examples two different methods of stating the composition of these compounds have been ex- pressed. Deutoxide of Manganese. 1. — 1 Manganese 28 + li Oxygen 12 = 40 2.-2 Manganese 56 + 3 Oxygen 24 = 80 3.— 1 Protoxide 36 + 1 Peroxide 44 = 80 Deutoxide of Lead. 1.— 1 Lead 104 + 1£ Oxygen 12 = 116 2.-2 Lead 208 + 3 Oxygen 24 = 232 3.— 1 Protoxide 112 + 1 Peroxide 120 = 232 Peroxide of Iron. 1.— 1 Iron 28 + H Oxygen 12 = 40 2.-2 Iron 56 + 3 Oxygen 24 = 80 Persulphate of Iron. l._l Peroxide 40 + l£ Sulphuric acid 60 = 100 2.-2 Peroxide 80 + 3 Sulphuric acid 120 = 200 Deutoxide of Antimony. 1. — 1 Antimony 44 + 1^ Oxygen 12 = 56 2.-2 Antimony 88 + 3 Oxygen 24 = 112 It will be observed here, that though the equivalents of the compounds are represented by different numbers, accord- ing to these views, the proportion of the different elements are present in the same ratio in each. 422 CHEMICAL EQUIVALENTS. HYDROGEN = 1. Abbreviations — W. Water; C. Crystallized; A. Acid. DIVISION I— SIMPLE SUBSTANCES. Class I. — simple substances not metallic, and their combinations with each other- Oxygen, 8 Hydrogen, 1 Protoxide of, ( Water) 1 Oxygen 8+1 Hydrogen 1 . 9 Deutoxide of, 2 Oxygen 16 + 1 Hydrogen 1 ... 17 Nitrogen, 14 Atmospheric Air, 1 Oxygen 8 + 2 Nitrogen 28 . . 36 Protoxide of Nitrogen, (Nitrous Oxide), 1 Oxygen 8+1 Nitrogen 14 22 Deutoxide of Nitrogen (Nitric Oxide), 2 Oxygen 16+1 Nitrogen 14 30 Hyponitrous Acid, 3 Oxygen 24+1 Nitrogen 14 . . 38 Nitrous Acid, 4 Oxygen 32 + 1 Nitrogen 14 . . . 46 Nitric Acid, 5 Oxygen 40 + 1 Nitrogen 14 ... . 54 Sp. Gr. 1.5. 2 W. 18 72 Ammonia, 3 Hydrogen 3+1 Nitrogen 14 ... . 17 Sulphur, 16 Hyposulphurous Acid, 1 Oxygen 8+2 Sulphur 32 .40 Sulphurous Acid, 2 Oxygen 16 + 1 Sulphur 16 . . 32 Sulphuric Acid, 3 Oxygen 24 + 1 Sulphur 16 . . . 40 Sp. gr. 1.845. 1W.9 49 Hyposulphuric Acid, 1 Sulphurous Acid 32 + 1 Sulphuric Acid 40 ; or 5 Oxygen 40 + 2 Sulphur 32 . . 72 SELENIUM PHOSPHORUS—* CARBON. 423 Sulphureted Hydrogen, 1 Sulphur 16+1 Hydrogen 1 17 Bisulphureted Hydrogen, 2 Sulphur 32+1 Hydrogen 1 33 Selenium 4,0 Oxide of, 1 Oxygen 8 + 1 Selenium 40 . . 48 Selenious Acid, 2 Oxgyen 16+1 Selenium 40 . . . 56 Selenic Acid, 3 Oxygen 24+1 Selenium 40 ... 64 Selenureted Hydrogen, 1 Hydrogen 1+1 Selenium 40 41 Phosphorus 12 ? Hypophosphorous Acid, 1 Oxygen 8+ 2 Phosphorus 24 32? Phosphorous Acid, 1 Oxygen 8 + 1 Phosphorus 12 . 20 ? Hydrophosphorous Acid, 2 Phosphorous Acid 40+1 Water 9 49 ? Phosphoric Acid, 2 Oxygen 16 + 1 Phosphorus 12 . 28 ? Hydruret of PJwsphorus (Phosphureted Hydrogen), 1 Hy- drogen 1 + 1 Phosphorus 12 13? JBihydruret of Phosphorus, 2 Hydrogen 2+1 Phos- phorus 12 14? Phospuret of Sidphur, 1 Sulphur 16 + 1 Phosphorus 12 28 Carbon 6 Oxide of, (Carbonic Oxide) 1 Oxyg. 8+1 Carbon 6 14 Carbonic Acid, 2 Oxygen 16 + 1 Carbon 6 ... 22 Oxalic Acid, 3 Oxygen 24+2 Carbon 12 ; or, 1 Carbonic Oxide 14+1 Carbonic Acid 22 36 C. 4, W. 36 72 Bicarburet of Hydrogen, 1 Hydrogen 1 + 1 Carbon 12 13 Hydruret of Carbon, ( Olefiant gas) 1 Hyd. 1 + 1 Carbon 6 7 Bihydruret of Carbon (Light Carbureted Hydrogen), 2 Hydrogen 2 + 1 Carbon 6 8 Alcohol, I Oxygen 8 + 2 Carbon 12 + 3 Hydrogen 3 ; or, 1 Water 9 + 2 Olefiant gas 14 23 Sulphuric Ether, 1 Oxygen 8+5 Hydrogen 5+4 Carbon 24 ; or, 1 Water 9 + 4 Olefiant gas 28 ... . 37 Formic Acid, 3 Oxyg. 24 + 1 Hydrog. 1+2 Carb. 12 37 Acetic Acid, 3 Oxyg. 24 + 2 Hydrog. 2 + 4 Carb. 24 50 C. 1, W. 9 59 Succinic Acid, 3 Oxyg. 24 + 2 Hydrog. 2 + 4 Carb. 24 50 Gallic Acid, 3 Oxyg. 24 + 3 Hydrog. 3 + 4 Carb. 24 51 424 BORON— CHLORINE. Citric Acid, 4 Oxyg. 32 + 2 Hydrog. 2 + 4 Carb. 24 58 C. 2, W. 18 76 Malic Acid, 4 Oxyg. 32 + 10 Hydrog. 10 + 3 Carb. 18 60 Tartaric Acid, 5 Oxyg. 40+2 Hydrog. 2 + 4 Carb. 24 66 C. 1, W. 9 75 Saccholactic, or Mucic Acid, 8 Oxyg. 64 + 4 Hydrog. 4+ 6 Carb. 36 104 Benzoic Acid, 3 Oxyg. 24 + 6 Hydrog. 6 + 15 Carb. 90 120 Bicarburet of Nitrogen, ( Cyanogen) 1 Nitrogen 14 + 2 Carbon 12 26 Cyanic Acid, 1 Cyanogen 26 + 1 Oxygen 8 . . . 34 Hydrocyanic Acid, (Prussic Acid) 1 Cyanogen 26+1 Hydrogen 1 27 Ferrocyanic Acid, 2 Hyd. 2+1 Iron 28 + 3 Cyanogen 78; or, 2 Hydrocyanic A. 54 + 1 Cyanide of Iron 54 108 Sulphocyanic Acid, 1 Hydrocyanic Acid 27+2 Sulphnr 32 59 Bisulphuret of Carbon, 2 Sulphur 32+1 Carbon 6 . 38 Sulphovinic Acid, 1 Sulphuric A. 404-2 Olefiant Gas 14 54 Phosphuret of Carbon, 1 Phosphorus 12+1 Carbon 6 18 Boron, 8 Boraic Acid, 2 Oxygen 16 + 1 Boron 8 24 C. 2 W. 18 42 Chlorine, 36 Protoxide of Chlorine, 1 Oxygen 8 + 1 Chlorine 36 . 44 Peroxide of Chlorine, 4 Oxygen 32+1 Chlorine 36 . 68 Chloric Acid, 5 Oxygen 40 + 1 Chlorine 36 .... 76 Perchloric Acid, 7 Oxygen 56+1 Chlorine 36 . . . 92 Muriatic Acid, 1 Hydrogen 1 + 1 Chlorine 36 . . . 37 Hydrate of Chlorine, 10 Water 90 + 1 Chlorine 36 .126 Chloride of Nitrogen, 1 Nitrogen 14+4 Chlorine 144 158 Chloride of Sulphur, 1 Sulphur 16 + 1 Chlorine 36 . 52 Subchloride of Carbon, 2 Carbon 12 + 1 Chlorine 36 . 48 Chloride of Carbon, 1 Carbon 6 + 1 Chlorine 36 . . 42 Per chloride of Carbon, 2 Carbon 12+3 Chlorine 108 120 Chlorocarbonic Acid, 1 Carbonic Oxide 14+1 Chlorine 36 50 Hydrocarburet of Chlorine, 2 Olefiant Gas 14 + 1 Chlorine 36 50 Chlorovyanic Acid, 1 Cyanogen 26 + 1 Chlorine 36 . 62 IODINE POTASSIUM. 425 Chloride of Phosphorus, 1 Phosphorus 1 2 -J- 1 Chlorine 36 48 Bichloride of Phosphorus, 1 Phosph. 12 -j- 2 Chlorine 72 84 Iodine, 124 Iodic Acid, 5 Oxygen 40-j-l Iodine 124 164 Hydriodic Acid, 1 Hydrogen 1 + 1 Iodine 124 . . 125 Tritiodide of Nitrogen, 1 Nitrogen 14 + 3 Iodine 372 386 Iodide of Sidphur, 1 Sulphur 16 + 1 Iodine 124 . . 140 Iodide of Phosphorus, 1 Phosphorus 12 + 1 Iodine 124 136 Hydriodide of Carbon, 2 Hydrogen 2 + 2 Carbon 12 + 1 Iodine 124 . . 138 Iodide of Chlorine, (Chloriodic Acid,) 1 Chlorine 36 + 1 Iodine 124 160 Bromine, 75 Hydrobromic Acid, 1 Hydrog. 1 + 1 Bromine 75 ... 76 Fluorine, 16? Fluoric Acid, 1 Fluorine 16+1 Hydrogen 1 . . 17? Fluoboric Acid, 1 Fluoric Acid 17+1 Boracic Acid 24 41? Fluosilicic Acid, 1 Fluoric Acid 17 + 1 Silica 16 . 33? Class II. — metals and their combina- tions WITH NON-METALLIC SUBSTANCES. ORDER I.— ALKALINE METALS. Potassium^ Chloride, 1 Chlorine 36 + 1 Potassium 40 . . Iodide, 1 Iodine 124+1 Potassium 40 . . . Phosphuret, 1 Phosphorus 12+1 Potassium 40 Sulphur et, 1 Sulphur 16 + 1 Potassium 40 . . Bisulphuret, 2 Sulphur 32+1 Potassium 40 . Oxide, (Potassa), 1 Oxygen 8 + 1 Potassium 40 Potassa, Acetate of, 1 Acetic Acid 50 + 1 Potassa 48 98 Arseniateof, 1 Arsenic Acid 62 + 1 Potassa 48 110 Binarseniate of, 2 Arsenic A.124+ 1 Potassa48 172 Binarseniate of, C. 1 W. 2 Arsenic A. 124 + 1 Potassa 48 + 1 W. 9 181 Arsenite, 1 Arsenious Acid 54 + 1 Potassa 48 102 40 76 164 52 56 72 48 426 SALTS OF POTASSA SODIUM. Potassa, Benzoate, 1 Benzoic Acid 120 + 1 Potassa 48 168 Carbonate, (Subcarbonate), 1 Carbonic Acid 22 + 1 Potassa 48 70 C. 2 W. Carbonate of Potassa 70 + 18 Water 88 Bicarbonate, (Carbonate), 2 Carbonic Acid 44 + 48 Potassa 92 C. 1 W. Bicarbonate of Potassa 92 + 1 Water 9 101 Chlorate, 1 Chloric Acid 76 + 1 Potassa 48 . 124 Hydrate, 1 Water 9 + 1 Potassa 48 ... 57 Perchlorate, 1 Perchloric A. 92 + 1 Potassa 48 140 Chromate, 1 Chromic Acid 52 + 1 Potassa 48 100 Bichromate, 2 Chromic A. 104 + 1 Potassa 48 152 Ferrocyanate, lFerrocyanic A. 108+1 Pot. 48 156 Hydriodate, 1 Hydriodic A. 125 + 1 Potassa 48 173 Nitrate, 1 Nitric Acid 54+1 Potassa 48 .102 Oxalate, 1 Oxalic Acid 36 + 1 Potassa 48 . 84 Binoxalate, 2 Oxalic Acid 72+1 Potassa 48 120 Quadroxalate, 4 Oxalic Acid 144+1 Potassa 48 192 C. 7 W. 1 Quadroxalate of Potassa 192 + 7 Water 63 .... 255 Pliosphate, 1 Phosphoric Acid 28 + 1 Potassa 48 76 C. 1 W. 1 Phosphate of Potassa 76 + 1 Water 9 85 Succinate, 1 Succinic Acid 50+1 Potassa 48 98 Sulphate, 1 Sulphuric Acid 40+1 Potassa 48 88 Bisidphate, 2 Sulphuric Acid 80 + 1 Potassa 48 128 C. 2 W. 1 Bisulphate of Potassa 128 + 2 Water 18 146 Tartrate, 1 Tartaric Acid 66 + 1 Potassa 48 114 Bitartrate, 2 Tartaric Acid 132 + 1 Potassa 48 180 C. 2 W. 1 Bitartrate of Potassa 180 + 2 Water 18 198 Peroxide of Potassium, 3 Oxygen 24 + 1 Potassium 40 64 Sodium, 24 Chloride, 1 Chlorine 36 + 1 Sodium 24 60 Iodide, 1 Iodine 124 + 1 Sodium 24 148 Fluoride, 1 Fluorine 16 + 1 Sodium 24 40 SALTS OF SODA LITHIUM. 427 P/wsphnret, 1 Phosphorus 12+1 Sodium 24? . . 36 Sulphuret, 1 Sulphur 16 + 1 Sodium 24 .... 40 Bisidphuret, 2 Sulphur 32 + 1 Sodium 24 ... . 56 Oxide of (Soda), 1 Oxygen 8 + 1 Sodium 24 ... 32 Soda, Hydrate of, 1 Soda 32 + 1 Water 9 . . . . 41 Acetate of, 1 Acetic Acid 50 + 1 Soda 32 . . 82 C.6W.1 Acetate of Soda 82 + 6 W. 54 136 JBiborate, (Borax; Subborate) C. 8 W. 2 Boracic A. 48 +1 Soda 32 +8 Water 72 152 Carbonate, 1 Carbonic Acid 22+1 Soda 32 . 54 C. 10 W. 1 Carbonate of S. 54 + 1 W. 90 144 Bicarbonate, 2 Carbonic Acid 44+1 Soda 32 . 76 Sesquicarbonate, Carbonate 54+76 Bicarbonate 130 ? Chlorate, 1 Chloric Acid 76 + 1 Soda 32 . . 108 lodate, 1 Iodic Acid 164 + 1 Soda 32 ... 196 Nitrate, 1 Nitric Acid 54 + 1 Soda 32 . . . 86 Oxalate, 1 Oxalic Acid 36 + 1 Soda 32 . . . 68 Phosphate, 1 Phosphoric Acid 28 + 1 Soda 32 60 C. 12, W., 1 Phosphate of Soda 60 + 12 Water 108 168 Biphosphate, C. 3 W., 2 Phosphoric Acid 56 + 1 Soda 32 + 3 Water 27 115 Succinate, 1 Succinic Acid 50+1 Soda 32 . 82 Sulphate, 1 Sulphuric Acid 40 + 1 Soda 32 . 72 C. 10 W., 1 Sulphate of Soda 72 + 10 Water90 162 Tartrate, 1 Tartaric Acid 66 + 1 Soda 32 . . 98 and Potassa, Tartrate of; C. 8 W., 1 Tartrate of Potassa 114+1 Tartrate of Soda 98 + 8 W. 72 284 Peroxide, l£ Oxygen 12+1 Sodium 24 . . 36 Lithium 10 Chloride, 1 Chlorine 36 + 1 Lithium 10 46 Iodide, 1 Iodine 124+1 Lithium 10 134 Phosphuret, 1 Phosphorus 12+1 Lithium 10 . . . 22 Sulphuret, 1 Sulphur 16 + 1 Lithium 10 ..... 26 Oxide (Lithia), 1 Oxygen 8+1 Lithium 10 ... 18 Lithia, Carbonate, Carbonic Acid 22+18 Lithia . 40 Nitrate, 1 Nitric Acid 54 + 1 Lithia 18 . . 72 Phosphate, 1 Phosphoric Acid 28 + 1 Lithia 18 46 428 SALTS OF AMMONIA. Lithia, Sulphate, 1 Sulphuric Acid 40 + 1 Lithia 18 . 58 C. 1 W., 1 Sulphate of Lithia 58 + 1 Water 9 . . . . 67 Ammonia* 17 Acetate of, 1 Acetic Acid 50 + 1 Ammonia 17 67 C. 7 W . Acetate of Ammonia 67 + 7 Water 63 130 Benzoate, C. 1 W., 1 Benzoic Acid 120+1 Ammonia 17 + 1 Water 9 146 Carbonate, 1 Carbonic Acid 22+1 Ammonia 17 39 Bicarbonate, 2 Carbonic Acid 44 + 1 Ammonia 17 61 2 W., Bicarbonate of Ammonia 61+2 Water 18 79 Sesquicarbonate, 1 Carb te . 39 + 1 Bicarbonate 61 100 Hydriodate, 1 Hydriodic A. 125 + 1 Amnion. 17 142 Hydrosulphuret, 1 Sulph. Hyd. 17+1 Amm. 17 34? lodate, 1 Iodic Acid 164 + 1 Ammonia 17 .181 Muriate, 1 Muriatic Acid 37 + 1 Ammonia 17 54 Nitrate, 1 Nitric Acid 54 + 1 Ammonia 17 . 71 C. 1 W., 1 Nitrate of Am. 71 + 1 W. 9 80 Oxalate, 1 Oxalic Acid 36 + 1 Ammonia 17 53 C. 2 W., 1 Oxalate of Am. 53 +2 W. 18 71 Binoxalate, C. 8 W., 2 Oxalic Acid 72 + 1 Ammonia 17 + 8 Water 72 161 Phosphate, 1 Phosphoric A. 28+ 1 Ammonia 17 45 C. 2 W., 1 Phosphate of Ammonia 45 + 2 Water 18 63 Biphosphate, 2 Phosphoric A. 56 + 1 Amm. 17 73 Succinate, 1 Succinic Acid 50+1 Ammonia 17 67 C. 2 W.j 1 Succinate of Ammonia 67 + 2 Water 18 85 Sulphate, 1 Sulphuric Acid 40 + 1 Ammonia 17 67 C. 1 W. 1 Sulphate of Ammonia 67 + 1 Water 9 76 Sulphite, 1 Sulphurous Acid 32+1 Ammonia 17 49 Urate, 1 Uric Acid 72 + 1 Ammonia 17 . . 89 * See page 244. CALCIUM SALTS 01? LIME BARIUM. 12 ( J ORDER II.— ALKALINE GEOFIABLE METALS. 54 Calcium . Chloride, 1 Chlorine 36 + 1 Calcium 20 Iodide, 1 Iodide 124+1 Calcium 20 . . . Fluoride, 1 Fluorine 16 + 1 Calcium 20 ? Phosphuret, 1 Phosphorus 12+1 Calcium 20 ? Sulphuret, 1 Sulphur 16 + 1 Calcium 20 . . Oxide (Lime), 1 Oxygen 8 + 1 Calcium 20 Lime, Hydrate, 1 Lime 28 + 1 Water 9 . . Acetate, 1 Acetic Acid 50 + 1 Lime 28 C. 6 W. 1 Acetate of Lime 78 + 6 W Arseniate, 1 Arsenic Acid 62 + 1 Lime 28 Arsenite, 1 Arsenious Acid 54+1 Lime 28 Carbonate, 1 Carbonic Acid 22 + 1 Lime 28 Chlorate, 1 Chloric Acid 76 + 1 Lime 28 Chloride, 1 Chlorine 36+1 Lime 28 . . Citrate, 1 Citric Acid 58 + 1 Lime 28 Muriate, C.5W. 1 Muriatic Acid 37+1 Lime 28 +5 Water 45 Nitrate, 1 Nitric Acid 54+1 Lime 28 C. 3 W. 1 Nitrate of Lime 82+3 W. 27 Oxalate, 1 Oxalic Acid 36+1 Lime 28 dried at 100°, Oxalate of L.64 + 2W, Phosphate, 1 Phosphoric Acid 28+1 Lime 28 Biphosphate, 2 Phosphoric Acid 56 + 1 Lime 28 Sulphate, 1 Sulphuric Acid 40+1 Lime 28 C. 2 W., 1 Sulphate of L. 68 + 2 W. 18 Tartrate, 1 Tartaric Acid 66 + 1 Lime 28 . . dried at 70°, 1 Tartrate of Lime 94+4 Water 36 . Barium . . Chloride, 1 Chlorine 36 + 1 Barium 70 .... . C. 2 W. 1 Chloride of Barium 106+2 W. 18 Sulphuret, 1 Sulphur 16 + 1 Barium 70 .... . Oxide (Baryta), 1 Oxygen 8 + 1 Barium 70 . „ „ Baryta, Acetate of, 1 Acetic Acid 50+1 Barytes 78 C. 3 W. 1 Acetate of Baryta 128 + 3 Water 27 ..... Carbonate^ 1 Carbonic Acid 22+1 Baryta 78 20 56 144 36 32 36 28 37 78 132 90 82 50 104 64 86 110 82 109 64 82 56 84 68 86 94 130 70 106 124 128 155 430 SALTS OF BARYTA STRONTIUM— MAGNESIUM. Baryta, Chlorate, 1 Chloric Acid 76 + 1 Baryta 78 . 154 Chromate, 1 Chromic Acid 52 + 1 Baryta 78 130 Jodate, 1 Iodic Acid 164+1 Baryta 78 . . 242 Muriate, C. 1 W. 1 Muriatic Acid 37+1 Ba- ryta 78 + 1 Water 9 124 Nitrate, 1 Nitric Acid 54 + 1 Baryta 78 . . 132 Oxalate, 1 Oxalic Acid 36 + 1 Baryta 78 . . 114 Binoxalate, Oxalic Acid 72+ 1 Baryta 78 . 150 Phosphate,! Phosphoric Acid 28 + 1 Baryta 78 ? 106 Sulphate, 1 Sulphuric Acid 40+1 Baryta 78 118 Tartrate, 1 Tartaric Acid 66 + 1 Baryta 78 . 144 Peroxide of Barium, 2 Oxygen 16 + 1 Barium 70 . . 86 Strontium 44 Chloride, 1 Chlorine 36 + 1 Strontium 44 .... 80 C. 5 W., 1 Chloride of Strontium 80 + 5 W. 45 125 Iodide, 1 Iodine 124 + 1 Strontium 44 168 Phosphuret, 1 Phosphorus 12 + 1 Strontium 44 . . 56 Sulphur et, 1 Sulphur 16+1 Strontium 44 .... 60 Oxide (Strontia), 1 Oxygen 8+1 Strontium 44 . . 52 Strontia, Acetate, 1 Acetic Acid 50 + 1 Strontia 52 . 102 Clf.l Acetate of Strontia 102+1 Water 9 111 Carbonate, 1 Carbonic Acid 22 + 1 Strontia 52 74 Muriate, 1 Muriatic A. 37+1 Strontia 52 . . 89 Phosphate, 1 Phosphoric Acid 28+1 Strontia 52 80 Sulphate, 1 Sulphuric Acid 40 + 1 Strontia 52 92 ORDER III.— COMMON GEOFIABLE METALS. Magnesium Chloride, 1 Chlorine 36 + 1 Magnesium 12 . . Iodide, 1 Iodine 124+1 Magnesium 12 ... Phosphuret, I Phosphorus 12+1 Magnesium 12 Sidphuret, 1 Sulphur 16 + 1 Magnesium 12 . . Oxide {Magnesia), 1 Oxygen 8+1 Magnesium 12 Magnesia, Ammoniaco-Phosphate, 1 Phosphate of Mag. 48+ 1 Phosphate of Ammonia 45+4 W. 36 129 Borate, 1 Boracic Acid 24+1 Magnesia 20 44 Biborate (Boracite) 2 Boracic A. 48 + 1 Mag. 20 68 Carbonate,! Carbonic Acid 22 + 1 Magnesia 20 42 12 48 136 24 28 20 SALTS OF MAGNESIA ALUMINUM, &C. 431 Magnesia, Hydrate, 1 Water 9+1 Magnesia 20 . . 29 Muriate, I Muriatic Acid 37 + 1 Magnesia 20 57 C. 5 W. 1 Muriate of M. 57 + 5 W. 45 102 Nitrate, 1 Nitric Acid 54+1 Magnesia 20 . 74 C. 6 W., 1 Nitrate of M. 74+6 W. 54 128 Phosphate, 1 Phosphoric Acid 28+1 Mag. 20 48 C. 7 W., 1 Phosphate of Magnesia 48 + 7 Water 63 .... Ill Sulphate, 1 Sulphuric Acid40 + 1 Magnesia 20 60 C. 7 W., 1 Sulphate of Magnesia 60 + 7 Water 63 123 Tartrate, 1 Tartaric Acid 66 + 1 Magnesia 20 86 Aluminum 10 Oxide of (Alumina) 1 Oxyg. 8+1 Aluminum 10 18 Alumina, Sulphate, 1 Sulphuric Acid 40 + 1 Alumina 18 58 Potassa Sulphate (Alum), 1 Sulphate of Potassa 88 + 3 Sulphate of Alumina 174 + 25 W. 225 487 SlLICUM 8 Oxide of (Silica), 1 Oxygen 8+1 Silicum 8 . . . . 16 Fluo- Silicic Acid, 1 Fluoric A. 17+1 Silica 16 . . 33 ? Glucinum, 18 Oxide of , (Glucina), 1 Oxygen 8 + 1 Glucinum 18 . 26 Ittrium 34 Oxide of, (Ittria) 1 Oxygen 8 + 1 Ittrium 34 ... 42 Zirconium, 40 Oxide of, (Zirconia) 1 Oxygen 8+1 Zirconium 40 . 48 Thorinum, ? ORDER IV.— COMMON METALS WHOSE OXIDES CAN- NOT BE REDUCED BY HEAT ALONE. Iron, 28 Chloride, 1 Chlorine 36 + 1 Iron 28 64 432 IRON SALTS OF IRON. Perchloride, 1J Chlorine 54 + 1 Iron 28? 82 Iodide, 1 Iodine 124+1 Iron 28 152 Sulphuret, 1 Sulphur 16 + 1 Iron 28 . • . . . . 44 Bisulphuret, 2 Sulphur 32 + 1 Iron 28 60 Phosphuret, 1 Phosphorus 12 + 1 Iron 28 ? ... 40 Protoxide, 1 Oxygen 8 + 1 Iron 28 36 Protoxide, Acetate, 1 Acetic A. 50 + 1 Protox. of Iron 36 86 Carbonate, 1 Carbonic A. 22 + 1 Prot. of Iron 36 58 Muriate, 1 Muriatic A. 37 + 1 Prot. of Iron 36 73 Nitrate, 1 Nitric A. 54 + 1 Protox. of Iron 36 90 C.7W.1 Protonitrate of Iron 90+7 Water 63 153 Oxalate, C.2W.1 Oxalic Acid 36 + 1 Protox. Iron 36 + 2 Water 18 90 Phosphate, 1 Phosphoric A. 28 + 1 Protox. 36 64 Sidphate, 1 Sulphuric A. 40 + 1 Protox. 36 76 C. 7 W. 1 Protosulphate of Iron 76+ 7 Water 63 139 Sulphite, 1 Sulphurous Acid 32+1 Protox. of Iron 36 68 Tartrate, 1 Tartaric A. 66 + 1 Prot. of Iron 36 102 C. 2 W. 1 Prototartrate of Iron 102 + 2 Water 18 120 Protoxide and Potassa, Tartrate of, 1 Tartrate of Potassa 114 + 1 Tartrate of Iron 102 216 Peroxide of Iron, 1| Oxygen 12+1 Iron 28 . . . 40 Acetate of\\ Acetic A. 75 +1 Perox. of Iron 40 115 Carbonate, 1 \ Carbonic A. 33 + 1 Pe- rox. of Iron 40 73 Muriate, \\ Muriatic A. 54.5 + 1 Pe- rox. of Iron 40 94.5 Nitrate, 1| Nitric A . 81 1 Perox. of Iron 40 121 C. 8 W. 1 Pernitrate of Iron 121 + 8 Water 72 . . 193 Sulphate, 1^ Sulphuric A. 60 + I Pe- rox. of Iron 40 100 lead salts of lead. 433 Lead 104* Chloride, 1 Chlorine 36 + 1 Lead 104 ..... 140 Iodide, 1 Iodine 124 + 1 Lead 104 228 Sulphuret, 1 Sulphur 16 + 1 Lead 104 120 Phosphuret, 1 Phosphorus 12 + 1 Lead 104 ... 116 Protoxide, 1 Oxygen 8 + 1 Lead 104 112 Protoxide of Lead, Acetate, 1 Acetic Acid 50 + 1 Pro- tox. of Lead 112 ..... 162 C.8W.1 Protacetate of Lead 162 + 3 Water 27 . . 189 Subacetate, 1 Acetic Acid 50 + 3 Protox. of Lead 336 ... . 386 Carbonate, 1 Carbonic Acid 22 + 1 Protox. of Lead 112 .... 134 Chromate, 1 Chromic Acid 52 + 1 Protox. of Lead 112 .... 164 Subchromate, 1 Chromic Acid 52 + 2 Protox. of Lead 224 ... . 276 lodate, 1 Iodic Acid 164+1 Pro- tox. of Lead 112 276 Malate, 1 Malic Acid 60 + 1 Protox. of Lead 112 172 Molybdate, 1 Molybdic Acid 72+1 Protox. of Lead 112 .... 184 Nitrate, 1 Nitric Acid 54 + 1 Pro- tox. of Lead 112 166 Subnitrate, 1 Nitric A. 54 + 2 Pro- tox. of Lead 224 278 Oxalate, 1 Oxalic Acid 36 + 1 Pro- tox. of Lead 112 148 Phosphate, 1 Phosphoric Acid 28 + 1 Protox. of Lead 112 . . . . 140 Sulphate, 1 Sulphuric Acid 40 + 1 Protox. of Lead 112 . . . . 152 Tartrate, 1 Tartaric A. 66 + 1 Pro- tox. of Lead 112 178 Bitungstate, 2 Tungstic A. 240+1 Protox. of Lead 112 .... 352 Deutoxide of Lead, 1| Oxygen 12+1 Lead 104 . . 116 Peroxide of Lead, 2 Oxygen 16+1 Lead 104 ... 120 2 F 434 copper— salts of copper— zinc. Copper, 64 Chloride, . 1 Chlorine 36+1 Copper 64 10O Perchloride, 2 Chlorine 72+1 Copper 64 136 Iodide, 1 Iodine 124+1 Copper 64 188 Sulphuret, 1 Sulphur 16 + 1 Copper 64 80 Bisidphuret, 2 Sulphur 32 + 1 Copper 64 96 Phosphuret, 1 Phosphorus 12 + 1 Copper 64 .... 76 Protoxide, 1 Oxygen 8+1 Copper 64 ..... . 72 Peroxide, 2 Oxygen 16 + 1 Copper 64 80 Peroxide of Copper, Subperacetate, 1 Acetic Acid 50+1 Perox. Copper 80 130 C. 6 W. ( Verdigris} 1 Suhacetate, 130 + 6 W. 54 . 184 Acetate, 2 AceticA.100 + 1 Per. Cop. 80 180 C.3 W. 1 Peracetate of Copper 180 + 3 Water 27 207 Arseniate, 2 Arsenic A. 124 + 1 Pe- rox. Copper 80 204 Subcarbonate, 1 Carbonic Acid 22+1 Perox. Copper 80 . . . . , 102 C. 2 W. (Malaehite), 1 Subcarb. of Cop. 102 + 2 Water 18 120 Nitrate, 2 Nitric A. 108 + 1 Perox. 80 188- Phosphate, 2 Phosphoric Acid 56 + 1 Perox. of Copper 80 .... 136 Subphosphate, 1 Phosphoric A. 28 + 1 Perox. of Copper 80 + 2 Water 18 126 Sulphate, 2 Sulphuric A. 80 + 1 Peroxide Copper 80 .... 160 C. 10 W. 1 Persulphate of Copper 160+10 W. 90 ... 250 2Tino, 34 Chloride, 1 Chlorine 36 + 1 Zinc 34 70 Iodide, 1 Iodine 124 + 1 Zinc 34 158 Phosphuret, 1 Phosphorus 12 + 1 Zinc 34 ... . 46 Sulphuret, 1 Sulphur 16+1 Zine 34 50 Protoxide, 1 Oxygen 8 + 1 Zinc 34 42 Acetate, 1 Acetic Acid 50 + 1 Protox. Zinc 42 92 C. 7 W. 1 Acetate 92+7 Water 63 155 Carbonate, 1 Carbonic A. 22 + 1 Protox. Zinc 42 64 ANTIMONY AUSENIC. 435 Protoxide, Muriate, 1 Muriatic A. 37 + 1 Protoxide 42 79 Nitrate, 1 Nitric Acid 54 + 1 Protoxide 42 96 C. 6 W. I Nitrate of Zinc 96 + 6 Water 54 150 Phosphate, 1 Phosphoric Acid 28+1 Pro- toxide Zinc 42 70 Sulphate, 1 Sulphuric A. 40 + 1 Prot. Zinc 42 82 Sulphate, C. 7 W. 1 Sulphate of Zinc 82 + 7 Water 63 145 Tartrate, 1 Tartaric A. 66 + 1 Protox. Zinc 42 108 Antimony, 44 Chloride, 1 Chlorine 36+1 Antimony 44 80 Perchloride, 2 Chlorine 72 + 1 Antimony 44 . . . 116 Iodide, 1 Iodine 124+1 Antimony 44 168 Phosphuret, 1 Phosphorus 12 + 1 Antimony 44 . . 56 Sulphur et, 1 Sulphur 16 + 1 Antimony 44 ... . 60 Protoxide, 1 Oxygen 8+1 Antimony 44 52 Hydro-sulphuret (Kermes Mineral) 1 Sulphu- reted Hydrogen 17+1 Protox. Antimony 52 69 Sulphur eted Hydrosulphuret ( Golden Sulphu- retj 1 Bisulphureted Hydrogen 33 + 1 Protoxide Antimony 52 85 and Potassa, Tartrate of ( Tartar Emetic) 2 Tartaric Acid . . . 132 ] 1 Potassa 48 ( 3 Protox. Antimony . . 156 j 3 Water 27 J Muriate, 1 Muriatic Acid 37+1 Protoxide Antimony 52 89 Deutoxide, (AntimoniousA.) 1 § Oxyg. 12+1 Antimony 44 56 Peroxide, (Antimonic A.) 2 Oxygen 16 + 1 Antimony 44 60 Arsenic, 38 Hydruret, ( Arsenureted Hydrogen) 1 Hydrogen 1 + 1 Arsenic 38 39 ? Chloride, 1 Chlorine 36+1 Arsenic 38 74? Sidphuret, (Realgar) 1 Sulphur 16+1 Arsenic 38 . 54 Sesquisulphuret, ( Orpiment) 1| Sulphur 24+1 Ar- senic 38 62? Bisulphuret, 2 Sulphur 32 + 1 Arsenic 38 70 436 TIN— BISMUTH— SALTS OF BISMUTH. Protoxide , ? Deutoxide, (Arsenious Acid, or White Oxide of Arsenic ) 2 Oxygen 16 + 1 Arsenic 38 54 Peroxide (Arsenic Acid) 3 Oxygen 24 + 1 Arsenic 38 62 Tin, 58 Chloride, 1 Chlorine 36 + 1 Tin 58 ...... . 94 Perchloride, 2 Chlorine 72 + 1 Tin 58 . ..... 130 Iodide, 1 Iodine 124 + 1 Tin 58 182 Sulphuret, 1 Sulphur 16+1 Tin 58 74 Bisulphuret, 2 Sulphur 32 + 1 Tin 58 90 Phosphuret, 1 Phosphorus 12 + 1 Tin 58 . . . . 70 Protoxide, 1 Oxygen 8 + 1 Tin 58 66 Muriate, 1 Muriatic A. 37 + 1 Protox. Tin 66 103 Peroxide, 2 Oxygen 16 + 1 Tin 58 74 Bismuth, 72 Chloride, 1 Chlorine 36 + 1 Bismuth 72 ..... 108 Iodide, 1 Iodine 124 + 1 Bismuth 72 196 Phosphuret, 1 Phosphorus 12 + 1 Bismuth 72 . . . 84 Sidphuret, 1 Sulphur 16 + 1 Bismuth 72 88 Protoxide, 1 Oxygen 8 + 1 Bismuth 72 80 Acetate, 1 Acetic A. 50 + 1 Ox. of Bismuth 80 130 Carbonate, 1 Carbonic A. 22 + 1 Oxide of Bismuth 80 102 Subnitrate, 1 Nitric Acid 54 + 2 Oxide of Bismuth 160 . . 214 Nitrate, 1 Nitric A. 54 + 1 Ox. of Bismuth 80 134 C. 3 W. 1 Nitrate of Bismuth 134 + 3 Water 27 .161 Binitrate, 2 Nitric Acid 108 + 1 Oxide of Bismuth 80 188 Oxalate, 1 Oxalic A, 36 + 1 Ox. of Bismuth 80 116 Phosphate, 1 Phosphoric A. 28 + 1 Oxide of Bismuth 80 108 Sulphate, 1 Sulphuric Acid 40+1 Oxide of Bismuth 80 120 Tartrate, 1 Tartaric Acid 66+1 Oxide of Bismuth 80 146 MA-NGANESE- ■CHKOME COBALT. 437 Manganese, 28 Chloride, 1 Chlorine 36 + 1 Manganese 28 ... . 64 Iodide, 1 Iodine 124 + 1 Manganese 28 152 Phosphuret, 1 Phosphorus 12 + 1 Manganese 28 . . 40 Sidphuret, 1 Sulphur 16 + 1 Manganese 28 ... 44 Protoxide, 1 Oxygen 8 + 1 Manganese 28 ... . 36 Acetate, 1 Aeetic A. 50 + 1 Protox. Manganese 36 86 C. 4 W. 1 Acetate of Manganese 86 + 4 Water 36 ..... 122 Carbonate, 1 Carbonic A. 22 + 1 Protoxide Manganese 36 58 Nitrate, C. 7 W. 1 Nitric Acid 54 + 1 Px-otox- ide Manganese 36 + 7 Water 63 . . . 153 Oxalate, 1 Oxalic A. 36 + 1 Protox. Manganese 36 72 Phosphate, 1 Phosphoric Acid 28+1 Pro- toxide Manganese 36 64 Sulphate, 1 Sulphuric Acid 40 + 1 Protox- ide Manganese 36 . . . .... 76 Sulphate, C. 5 W. 1 Sulphate of Manganese 76 + 5 Water 45 121 Deutoxide, 1J Oxygen 12 + 1 Manganese 28 . . . 40 Red Oxide ? Peroxide, 2 Oxygen 16+1 Manganese 28 ... . 44 Manganeseous Acid, 3 Oxygen 24+1 Manganese 28 52 Manganesic Acid, 4 Oxygen 32+1 Manganese 28 . GO Chrome, . 28 Sulphur et, 1 Sulphur 16 + 1 Chrome 28 .... 44 Protoxide, 1 Oxygen 8+1 Chrome 28 36 Deutoxide, 2 Oxygen 16 + 1 Chrome 28 44 Peroxide, ( Chromic Acid) 3 Oxygen 24+1 Chrome 28 52 Chlorochromic Acid ? Fluochromic Acid ? Cobalt, 26 Chloride, 1 Chlorine 36+1 Cobalt 26 62 Iodide, 1 Iodine 124 + 1 Cobalt 26 150 Phosphuret, 1 Phosphorus 12 + 1 Cobalt 26 . . . 38 Sulphuret, 1 Sulphur 16+1 Cobalt 26 42 Protoxide 1 Oxygen 8+1 Cobalt 26 34 438 SALTS OF COBALT URANIUM, &C. Protoxide, Acetate, 1 Acetate A. 50 + 1 Prot. of Cobalt 34 84 Carbonate, 1 Carbonic A. 22 -f- 1 Protox. of Cobalt 34 56 Muriate, 1 Muriatic A. 37 + J Protoxide Co- balt 34 4- 1 Water 9 80 Nitrate, 1 Nitric A. 54 + 1 Prot. of Cobalt 34 88 C. 6 W. 1 Nitrate of Cobalt 88 + 6 Water 54 142 Sulphate, I Sulphuric A. 40 + 1 Protox. of Cobalt 34 74 C. 7 W. 1 Sulphate of Cobalt 74 + 7 Water 63 . . ...... 137 Tartrate, 1 Tartaric A. 66 + 1 Protoxide of Cobalt 34 100 Peroxide, 1$ Oxygen 12 + 1 Cobalt 26 38 Uranium, P . 208 Protoxide, 1 Oxygen 8 + 1 Uranium 208 216 Peroxide, 2 Oxygen 16 + 1 Uranium 208 .... 224 Cerium, 50 Protoxide, 1 Oxygen 8 + 1 Cerium 50 58 Peroxide, 1J Oxygen 12 + 1 Cerium 50 62 Titanium, 32 Protoxide, 1 Oxygen 8 + 1 Titanium 32 40 Peroxide, (Titanic A.) 2 Oxygen 16 + 1 Titanium 32 48 Tungsten, 96 Deutoxide, 2 Oxygen 16 + 1 Tungsten 96 . . . . 112 Peroxide, ( Tungstic A.J S Oxygen 24+1 Tungsten 96 120 Cadmium, 56 Chloride, 1 Chlorine 36 + 1 Cadmium 56 ... . 92 Iodide, 1 Iodine 124 + 1 Cadmium 56 180 Phosphuret, 1 Phosphorus 12 + 1 Cadmium 56 . . 68 Sulphuret, 1 Sulphur 16 + 1 Cadmium 56 ... . 72 Protoxide, 1 Oxygen 8+1 Cadmium 56 64 Carbonate, 1 Carbonic A. 22 + 1 Ox. of Cad- mium 64 86 TELLURIUM, &C. MERCURY. 439 Protoxide, Nitrate, 1 Nitric A. 54 + * Ox. of Cadmium 64 + 4 Water 36 154 Oxalate, 1 Oxalic A. 36 + 1 Ox. of Cadmium 64 + 3 Water 27 127 Phosphate, 1 Phosphoric A. 28 + 1 Ox. of Cadmium 64 92 Sulphate, 1 Sulphuric A. 40 + 1 Ox. of Cad- mium 64 104 C. 4 W., 1 Sulphate of Cadmium 104 4 + Water 36 140 Tellurium, 32 Hydruret, 1 Hydrogen 1 + 1 Tellurium 32 ... . 33 Chloride, 1 Chlorine 36 + 1 Tellurium 32 .... 68 Oxide, 1 Oxygen 8 + 1 Tellurium 32 40 Molybdenum, 48 Protoxide, 1 Oxygen 8+1 Molybdenum 48 ... . 56 Deutoxide, (Molybdous A.) 2 Ox. 16+1 Molybdenum 48 64 Peroxide, (Molybdic A.) 3 Ox. 24 + 1 Molybdenum 48 72 COLUMBIUM, ........... x .. . 144 Oxide, (Columbia A.) 1 Oxygen 8 + 1 Columbium 144 152 Pluranium ? ORDER V.— METALS WHOSE OXIDES CAN BE REDUCED BY EXPOSURE TO HEAT WITHOUT INFLAMMABLE MATTER. Mercury, . , 200 Chloride, (Calomel) 1 Chlorine 36 + 1 Mercury 200 236 Bichloride, (Corrosive Sublimate) 2 Chlorine 72 + 1 Mercury 200 . 272 Iodide, 1 Iodine 124+1 Mercury 200 324 Periodide, 2 Iodine 248 + 1 Mercury 200 .... 448 Sulphuret, 1 Sulphur 16+1 Mercury 200 ... . 216 Bisulphuret, 2 Sulphur 32 + 1 Mercury 200 . . 232 Picyanide, 2 Cyanogen 52 + 1 Mercury 200 . . 252 Protoxide, 1 Oxygen 8 + 1 Mercury 200 . . 208 440 SALTS OF MERCURY SILVER. Protoxide, Acetate, 1 Acetic A. 50 + 1 Prot. Mercury 208 258 C. 4 W. 1 Protacetate of Mercury 258 + 4 Water 36 294 Carbonate, 1 Carbonic Acid 22+1 Protox. Mercury 208 230 Chromate, 1 Chromic Acid 52 + 1 Protox. Mercury 208 260 Nitrate, 1 Nitric A. 54 + 1 Prot. Mercury 208 262 C.2W.1 Protonitrate of Mercury 262 + 2 Water 18 280 Subnitrate, 1 Nitric Acid 54 + 2 Protox. Mercury 416 470 Oxalate, 1 Oxalic A. 36 + 1 Prot. Mercury 208 244 Phosphate, 1 Phosphoric Acid 28 + 1 Protox. Mercury 208 236 Sulphate, 1 Sulphuric Acid 40+1 Protox. Mercury 208 248 C. 2 W- 1 Protosulphate of Mercury 248 + 2 Water 18 .... 266 Peroxide, 2 Oxygen 16 + 1 Mercury 200 .... 216 Acetate, 2 Acetic A. 1 00 + 1 Perox. Mercury 216 316 Carbonate, 2 Carbonic Acid 44+1 Perox. Mercury 216 260 Nitrate, 2 Nitric A. 108 + 1 Perox. Mercury 216 324 Phosphate, 2 Phosphoric Acid 56+1 Perox. Mercury 216 272 Sidphate, 2 Sulphuric Acid 80 + 1 Perox. Mercury 216 296 Subsulphate, 1 Sulphuric Acid 40+1 Perox. Mercury 216 256 Silver 110 Chloride, 1 Chlorine 36 + 1 Silver 110 146 Iodide, 1 Iodine 124+1 Silver 110 234 Fluoride ? Phosphuret, 1 Phosphorus 12 + 1 Silver 110 ... 122 Sidphuret, 1 Sulphur 16 + 1 Silver 110 126 Suboxide, 1 Oxygen 8+1^ Silver 165 173 Protoxide, 1 Oxygen 8 + I Silver 110 118 Acetate, 1 Acetic Acid 50 + 1 Ox. Silver 118 168 GOLD PLATINA NICKEL. 441 Protoxide, Arsenite, 1 Arsenious A. 54 + 1 Ox. Silver 118 172 Carbonate, I Carbonic A. 22 + 1 Ox. Silver 1 18 140 Chlorate, 1 Chloric A. 76 + 1 Ox. Silver 118 194 Nitrate, 1 Nitric Acid 54+1 Ox. Silver 118 172 Oxalate, 1 Oxalic Acid 36 + lOx. Silver 118 154 [', . . Phosphate, 1 Phosphoric Acid 28+1 Ox. Sil- ver 118 146 Sulphate, 1 Sulphuric A. 40 + 1 Ox. Silver 1 18 158 Gold 200 Chloride, 1 Chlorine 36 + 1 Gold 200 236 Bichloride, 2 Chlorine 72 + 1 Gold 200 .,,... 272 Chloride of Gold and Sodium, 1 Chloride of Gold 236 + 1 Chloride of Sodium 60 296 Iodide, 1 Iodine 124 + 1 Gold 200 324 Sulphuret, 3 Sulphur 48 + 1 Gold 200 248 Protoxide, 1 Oxygen 8 + 1 Gold 200 208 Peroxide, 3 Oxygen 24 + 1 Gold 200 ...... 224 Platinum 96 Chloride, 1 Chlorine 36 + 1 Platinum 96 132 Perchloride, 2 Chlorine 72 + 1 Platinum 96 .... 168 Phosphuret, 1 Phosphorus 12 + 1 Platinum 96 . . . 108 Sulphuret, 1 Sulphur 16 + 1 Platinum 96 .... 112 Bisulphuret, 2 Sulphur 32 + 1 Platinum 96 . . . . 128 Protoxide, 1 Oxygen 8+1 Platinum 96 .... . 104 Peroxide, 2 Oxygen 16 + 1 Platinum 96 112 Nickel* 26 Chloride, 1 Chlorine 36 + 1 Nickel 26 ..... . 62 Iodide, 1 Iodine 124 + 1 Nickel 26 ....... 150 Sulphuret, 1 Sulphur 16 + 1 Nickel 26 42 Phosphuret, 1 Phosphorus 12 + 1 Nickel 26 ... . 38 Protoxide, 1 Oxygen 8+1 Nickel 26 34 Acetate, 1 Acetic Acid 50+1 Prot. Nickel 34 84 Carbonate, 1 Carbonic A. 22 + 1 Prot. Nickel 34 56 Nitrate, 1 Nitric Acid 54 + 1 Protox. Nickel 34 88 * A very intense heat is required to expel oxygen from nickel ; and it has been placed by some chemists in the preceding order of metals. 442 PALLADIUM ItHODIUM, &C Protoxide, Sulphate, 1 Sulphuric A. 40 + 1 Prot. Nickel 34 74 C. 7 W. 1 Sulphate of Nickel 74 + 7 Water 63 137 Palladium , . 56 Oxide, 1 Oxygen 8 + 1 Palladium 56 64 Rhodium 44 Protoxide, 1 Oxygen 8 -J- 1 Rhodium 44 52 Peroxide, 2 Oxygen 16 + 1 Rhodium 44 60 Osmium ? Iridium 30 Chloride, 1 Chlorine 36 + 1 Iridium 30 66 Protoxide, 1 Oxygen 8+1 Iridium 30 38 Peroxide, 2 Oxygen 16 -{- 1 Iridium 30 4(? MISCELLANEOUS APPARATUS. 443 CHAP. II. MISCELLANEOUS APPARATUS. 1311. Most of the apparatus required for performing the different experiments having been described along with the experiments themselves, it will be sufficient in this chapter to make some general observations on miscellaneous apparatus that may be useful to the beginner. 1312. A portable furnace constructed in the same manner as Dr. Black's (2-3), two or three chauffers of different sizes, and as many spirit lamps, constitute all the apparatus that is required for the application of heat in performing the greater number of these experiments. The furnace should have two openings near the top to allow a gun barrel or porcelain tube to be transmit- ted through it, and plugs made to fit closely to them, which may be made quite tight with a little clay when it is not required for this purpose. There should also be a large opening in front to allow a small muffle to be put in when a separate furnace for the process of cu- pellation cannot be conveniently built. The annexed figure gives a representa- tion of a section of a furnace provided with these openings, and a cover for the \^ top when the sand bath is not in use. 1313. Where a very high temperature is frequently requir- ed, a blast furnace (which is supplied with air solely by a pair of double bellows that must be connected with it) should be 444 MISCELLANEOUS APPARATUS. Fig. 68. constructed. The figure represents a modification of a small blast fur- nace which will be found very con- venient where there is no proper place for erecting a larger one. It is built of common fire bricks, using fire clay for mortar, and leaving two openings below the grating, one for the nozzle connected with the pair of double bellows, and the other for re- moving the ashes ; it is scarcely ne- cessary to mention that both these apertures must be com- pletely closed when the furnace is in use, the former by the nozzle of the bellows and the latter by brick, closing any small opening afterwards with a little clay. 1314. Instead of constructing a blast furnace of fire bricks, Mr. Aikin contrived a very convenient one which may be made of three large crucibles or melting pots ; the lower part of the first one serves as a resting place for the body of the F'g- 69. furnace, and a hole drill- ed in it admits the nozzle of the bellows. A larger portion of another crucible is plac- ed above this and forms the body of the furnace, four or five holes being drilled in it to admit the air ; and the upper part is a similar portion of the third crucible with a large hole cut at the side to allow the flame and gaseous matter to escape. Blast furnaces of this kind are usually made about 16 or 18 inches deep, from the bottom of the lower part to the top of the cover, and their greatest diameter seven or eight inches. The cover is not absolutely necessary, though it is certainly better to use it, as it protects the eyes from the light. 3 MISCELLANEOUS APPARATUS. 445 1315. No luting is required for this furnace; a small pair of double bellows will be found quite sufficient, and when it is well managed, which a little practice will soon enable the be- ginner to do, a thick piece of cast iron may be easily fused in it. The best kind of fuel for a furnace of this kind is coke, or red hot cinders taken from a common fire, they should be free from dust and ashes, in small pieces, and as nearly of one size as can be conveniently had. The bellows should be fixed to a strong frame, and the crucible furnace adjusted to a cor- responding height. 1316. A sand-bath will be found extremely convenient where a great number of experiments are performed ; but as there are not many students who have an opportunity of con- structing a proper sand-bath furnace, I shall now describe a method of arranging a common fire-place, which will be found very useful by those who can only have the use of a common apartment for carrying on their experiments. 1317. Instead of putting in a grate of the usual form, let one be built of brick of the form representedin the Figure (70), no iron work being required for it ex- cept the grating to support the fuel, which should be proportioned to the size of the fire - place, and two or three bars which may bs -placed in front so Fig. 70. as to rest in grooves left for the purpose, from which they may be easily taken out by a pair of tongs if required. A large and powerful fire may be kindled in this fire-place, which will not only be easily accessible and very convenient for a great number of common furnace operations, but of which advan- 446 MISCELLANEOUS APPARATUS. tage may also be taken to heat a sand-bath placed above. For this purpose an iron plate must be fixed in the chimney in the manner represented, a funnel pipe conveying the smoke from the fire below into the vent, which ought to be closed in on every side by a thin plate of sheet iron, so that no smoke can pass into the vent except through the funnel pipe connected with the sand-bath. In this manner, a constant draught is maintained, and the fire burns well ; and though the hottest part of the sand-bath seldom reaches a temperature above 500 or 600, still this is more than sufficient for the greater number of operations where a moderately hot sand-bath is required, and by placing the same substance on different parts of the plate, it may be exposed to the action of various degrees of heat. The sand on the plate need not be more than an inch and a half deep, and a small piece of sheet iron should be fixed in front to prevent any of the sand from falling off, and any hot air from escaping below ; it will be better also to place the plate in an inclined position. Such a sand-bath will be found particularly useful for digestion, slow evapora- tion, and a variety of other operations where a moderate heat is required. When disagreeable fumes are disengaged during any process, the vessel containing the materials from which they arise may often be placed under the sand-bath, when they will be carried up into the vent ; coated vessels may be dried slowly by placing them on the bricks at the side, and a cruci- ble placed in the fire may be exposed to a considerable heat by placing a chimney over that part of the fire in which it may be put. I am not aware of any plan which will render a common fire place so generally useful for performing a great number of experiments. 1318. Besides furnaces of different kinds which the student can procure according to the series of operations he intends to perform, he should be provided with two or three hundred bricks of different sizes and figures, with which, if he be an active experimenter, he will soon be able to construct a number of different temporary furnaces as they may be required. A ball of well worked fire clay will also be found of great use, and will save much trouble; it should be kept in a box made for MISCELLANEOUS APPARATUS. 447 Figs. 71. the purpose, or wrapped round with a moist cloth, pouring a little water upon it from time to time to prevent it from get- ting dry. 1319. A variety of tongs and pincers, straight and bent iron rods, will be found necessary for a number of experiments and processes. The annexed figures show one or two of the most convenient forms of these that have not been already described, all ordinary purposes, Hessian Crucibles will be found most convenient, as they resist a very high tem- perature, and are not so apt to be fluxed when heated with saline substances as any of the crucibles made in this coun- try, with the exception of Cornish crucibles, which are not easily procured ; they must not be exposed suddenly either to heat or cold however, as they are very apt to crack. Crucibles are made of a great variety of shapes ; the trian- gular form of the Hessian cru- cible is well known, and the a nnexed figures represent the other forms of which they are usually made. 1321. Black Lead crucibles may be procured of all sizes, as they are much employed in the arts ; they are made of a mixture of plumbago and clay, and may be used in general more frequently than Hessian crucibles, as they are not so liable to crack ; they are destroyed, however, by long ex- posure to a current of heated air and by nitre and some other saline substances. Crucibles made of Wedgwood's ware are very compact, and should be placed in a common crucible when they are used as they are apt to crack. 1322. A small platina crucible will be found necessary for a number of experiments, and is used principally for the pur- pose of fusing substances with potassa which contain a consi- derable quantity of silica. Cast iron crucibles may be easily procured at any iron foundry, and a common crucible may be given as a pattern to make a mould to cast it in. 443 MISCELLANEOUS APPARATUS. 1323. Evaporating vessels may be made of glass, Wedg-^ wood's ware, or metal. Vessels made of the first kinds of ware are generally employed for chemical purposes, as they are not so liable to be acted on as metallic vessels ; in eva- porating large quantities of liquids, however, which do not act upon metallic vessels, they should always be preferred. Fig. 77. They are usually made broad and shallow, that an extensive surface of liquid may be exposed J;o heat during evaporation. 1324. Instead of flat evaporating glass vessels, Florence flasks and wine flasks may be substituted with advantage in a num- ber of processes ; they will be found preferable to flasks made of flint glass as they are extremely thin, bear sudden altera- tions of temperature much better, and are not nearly so liable to be broken in the ordinary course of chemical operations. 1325. Small flasks made of very thin glass about two or three inches in diameter, and of the form repre- sented in the figure, are very useful in a number of chemical operations where it is necessary to expose a liquid for a short time to a boiling temperature : though made of flint glass, they may be put with safety on the cinders of a small chauffer if they are half full of the liquid. They may be used also for ascertaining the quantity of solid matter in a given weight of a saline solution, evaporat- ing it slowly on a sand bath. 1326. When a solid is to be digested for a long time in a liquid, flasks with a long neck (Fig. 79) are sometimes pre- ferred ; but for ordi- nary purposes they may be made of a taper or globular shape, as in Fig. 80 and Fig. 81. 1327. In the process of distillation, it is often necessary to prolong the neck of a retort before connecting it with a re- ceiver, that the different parts of the apparatus may be con- MISCELLANEOUS APPARATUS. 449 veniently arranged, or to facilitate the condensation of the vapour ; this is usually effected by means of a glass tube, sometimes blown into a globular shape in the centre, one ex- tremity fitting or being luted to the beak of the retort, while the other is introduced into the receiver. Fig- 82. This tube is termed an Adopter, and the method of adjusting it will be readily under- stood from the annexed figure. 1328. Fig. 83 represents the form of a bent tube which is frequently employed in the process of distillation and in a number of other operations, where it is necessary to pour in small quantities of liquid at a time into a vessel without shifting the apparatus with which it is connected, or taking out any stopper that might ex- pose its contents to the action of the air, the liquid that remains in part of the tube acting as a valve, which pre- vents the ingress or egress of air, but does not present any obstacle to the introduction of more liquid. In operating with corrosive liquids, instead of fitting it to the tubulure of glass vessels with a cork, it must be fixed in its place with a proper cement, or the tube may be made thicker at its lower extremity, and ground to the tubulure in the same manner as a stopper. 1329. For subliming benzoic acid, chloride and bichloride of mercury, and a number of other substances, a glass vessel of the form represented by Fig. 84 will be found very useful. Fig. 84. I' i s usually termed an Alembic, and con- sists of two parts ; the materials to be sub- limed being put into the lower part, and the upper part ground to it or joined with a proper cement. The small tube proceeding from the lower part of the capital carries off any watery vapour that may be condensed, which would otherwise drop into the lower part and break it. When the alembic is 2 G 450 MISCELLANEOUS APPARATUS. used for the sublimation of benzoic acid or of any other sub- stance where only a very gentle heat is required, it may be ap- plied in the usual way by a chauffer, supporting it by a retort stand. When a higher temperature is necessary, it may be placed in a sand bath. 1330. In many cases, two crucibles may be employed for a similar purpose, as in the sublimation of metallic arsenic from Fig, 85. a mixture of arsenious acid and black flux. The mixture must be put into the larger crucible which may be placed in a sand bath and exposed to a strong heat, inverting the other crucible and luting it to the first ; a small aperture must be left at the edge for the escape of gaseous matter, or a hole may be bored in the smaller crucible, and a glass tube inserted in it. 1331. For separating liquids of different specific gravities which have no chemical action on each other, a glass vessel termed a Separator is generally employed, consisting of a Fig. 86. funnel-shaped ball open at the top, and terminating in a long tube (Fig. 86.) A funnel with a long stem does very well for the same purpose, allowing the liquid to pass slowly through after filling the vessel and leaving it at last till the lighter portion has collected above, transferring it to another ves- sel as the last part of the heavier portion descends in the stem. 1332. An assortment of glass funnels of different sizes will be found necessary where many experiments are performed ; they are used not only for pouring liquids from one vessel to ano- ther, but also for supporting filters in the process of filtra- tion. 1333. Filters are usually made of unsized paper, doubling Fig. 87. a S( l uare piece by two opposite corners, so as to make it have a triangular shape, and then folding it alternately outwards and inwards from the cen- tre till it assumes the appearance represented in the figure on blowing upon it so as to separate the opposite sides, and cutting off the projecting points. MISCELLANEOUS APPARATUS. 451 1334. Precipkates left on a filter are washed merely by pouring water upon them till it passes through without taking up any soluble matter. A pipette of the form seen in Fig. 88, will be found very useful in separating precipi- tates from filters after they have been washed, and while they are still moist, filling it with water and then blowing a small stream of this fluid through the extremity till it is washed into a vessel placed be- low, after which the water may be dissipated by heat. Pipettes are also extremely useful for pour- ing or dropping small quantities of liquid upon any substance, as they can be easily made to terminate in a tube sufficiently large to give a slender stream, or drawn out into a fine capillary bore in the flame of a spirit lamp. It is not necessary for most purposes to have a ball blown in the cen- tre ; a piece of a common test tube, about 12 or 18 inches long, held in the flame of the lamp till it is softened and then drawn out gently, will give two pipettes on breaking it through the middle, which will be found quite sufficient for all ordinary operations in which they are required. 1335. In addition to the glass funnels required for filtering a number of liquids and other purposes, a square wooden frame with a brass point at each corner for fixing on a woollen or Fig. 89. linen cloth is frequently required, espe- cially in filtering bulky precipitates, as the precipitated oxide of antimony (847) or the mixture of quina and sulphate of lime obtained on adding lime to the acid decoction of yellow bark (1190). 1336. In many cases, where the precipitate is not very soluble in water, any soluble saline matter that may be mixed with it can be easily removed by agitating it with a con- siderable quantity of water, allowing it to subside, decanting the clear liquid, and repeating this several times. 1337- Instead of pouring off the clear liquid, it is often more convenient to run it off by a syphon. This is merely a 1 452 MISCELLANEOUS APPARATUS. J. Fig. 90. bent tu |3 6 wn i cn i s filled previously with water or any other liquid, and on introducing the shorter limb into the vessel containing the liquid to be drawn off and under its surface, it will rise in the syphon and pass out by the other extremity. Syphons are very useful in chemical operations, and are made of a great variety of shapes and materials, though the principle on which they are constructed is the same in all. A very sim- ple experiment which will render the student familiar with the method of using them may be performed by filling a plain sy- phon (made with both limbs of the same size and in the form of the letter U) with water, and putting each extremity into a jar of water at the same time. If the water be at the same height in both jars, none will pass from the one to the other though the syphon tube should be perfectly full ; if one of the jars be lifted up with the syphon in it, water will immediately flow from it to the other, and by alternately raising or depressing one of them, the water may be made to pass in either direction through the syphon, always how- ever from the jar in which it is at a higher level to the other, and ceasing to flow whenever the liquid acquires the same level in both. 1338. Phillips'' precipitate glasses will be found very useful Fig. 91. f or allowing small precipitates to be deposited, as, y*-^ from their form, little can adhere to the sides. / \ When made of this glass they may be used for a / \ number of operations in the same manner as a Flor- / \ ence flask, and liquids may be heated in them by C_ _Jj placing them on a sand bath. 1339. Flasks and funnels, and a number of other pieces of apparatus being usually supported on retort stands or rings (1040) when in use, and many requiring to be kept for some time, several shelves should be fitted up with a number of holes of different sizes and at different distances from each other, so that they may be set aside where they will not occasion any inconvenience. When this cannot be done, wooden stands of different sizes may be made to serve the same pur- MISCELLANEOUS APPARATUS. 453 pose ; the an- nexed figure represents one of the simplest methods of con- structing them. 1340. In places where a great number of experiments with gases are made, large quantities of those that are most in use should be made at a time, and stored in convenient vessels from which a supply may be easily procured as it is required ; the gasometers which have been already described may be used occasionally for this purpose, when the gas is not absorbed by water ; but the apparatus employed by Dr. Hope, and which he has permitted me to describe, will be found much more convenient. It consists of a large oil of vitriol bottle with a brass cap cemented to the mouth, in which two tubes with stop-cocks are fitted, water being introduced and forced out again when necessary by one and gas by the other. In the figure, it is represented in connection with the ex- tremity of a bent gun-bar- rel, fixed in an iron retort in which oxygen is pre- pared from the peroxide of manganese by heating it in a furnace. It is ob- vious that a large bottle of this kind could scarce- ly be moved when full of water without being broken, unless properly supported, and nothing does better for this than a tub made to fit the bottle, covering the bottom for the depth of an inch or two with saw-dust, and packing the space between the bottle and the sides with the same material. This will allow it to be 454 MISCELLANEOUS APPARATUS. moved easily from one place to another, and it has not been re- presented in this manner in the figure merely that the arrange- ment of the tubes connected with it may be seen more dis- tinctly. 1341. To explain the method of using it, I shall now de- scribe the manner in which it is filled with oxygen gas. After filling it with water, a bent tube is to be connected with the gun-barrel by a flexible leaden tube, about two or three feet in length, though represented much smaller in proportion to the size of the rest of the apparatus in the figure ; but no gas is to be allowed to pass into it unless it is sufficiently pure, the stop-cock at the extremity of the gun-barrel being kept shut, while the other one is to be opened, and the gas that is disengaged at first collected by means of a bent tube fitted to it, in small bottles over a pneumatic trough, so that its state of purity may be easily ascertained. When it is thought proper to commence collecting it, this stop-cock is to be shut and the other opened, so that the oxygen will now pass on to the gasometer, entering by one of the first mentioned tubes. Here it will press upon the surface of the water, which will be forced up through the tube seen in the interior of the bottle, continuous with the second stop-cock attached directly to the cap, and another bent tube being then placed over it, a syphon is formed, through which the water will continue to flow as long as any gas is disengaged ; and by using a large quantity of materials at a time, several bottles may be filled successively in this manner without undoing any part of the apparatus, except the leaden pipe that connects them directly with the gun-barrel. One bottle may be detached and re- placed by another in a few seconds when every thing is pro- perly adjusted ; and, if a longer time should be required, a few jars of oxygen may be collected from the tube attached to the stop-cock fixed to the upper part of the gun-barrel, or that tube may be adjusted to the second bottle gasometer while the first one is filling. The stop-cocks attached to the brass cap of these gasometers must be shut as the tubes connected with them are detached. MISCKLLANEOUS APPARATUS; 455 1342. Again, Fig. 94 shows the method in which the gas Fig. 94. j| s transferred from a gasometer of this kind when required for use. The syphon being detached, a tin funnel is placed above the stop-cock to which it was previously fixed, and it is evident, that on pouring water in- to it and opening the stop-cocks, it will de- scend through the tube in the interior of the bottle, and force the oxygen out at the other stop- cock by which it had entered, which opens immediately below the cap itself ; by connecting a flexible tube, accordingly, with this stop-cock, and pouring water into the funnel, the gas may be easily transferred to other vessels. It is in the same manner also that the air is expelled, and the gasometer filled with water, before connecting it with the oxygen gas apparatus. 1343. In describing the different apparatus required for the various processes and experiments, I have always pointed out those that are best adapted for the purpose. After a little practice, however, the student will soon learn to substitute one kind of apparatus for another, so that, with a few flasks, crucibles, test tubes, or precipitate glasses, a spirit lamp and a chauffer, he will be enabled to perform a great number of experiments. 1344. In addition to the apparatus more immediately re- quired for conducting his experiments, he will require a bal- ance with a set of weights and a liquid measure. A balance that turns with the ^th of a grain when empty, and in which Fig. 95. s i x or eight ounces of different materials can be con- veniently weighed, will be found amply sufficient for all ordinary purposes, and may be procured at a moderate price. The weights should be expressed 1 in grains and ounces, and the liquid measure (Fig. 95,) should be divided into ounces and drachms. 1345. A syringe for exhausting flasks and retorts will be found necessary for several experiments, though it is seldom much employed by those who are merely commencing the study of practical chemistry ; its construction will be readily under- 456 MISCELLANEOUS APPARATUS. Fig. 97. w Fig. 96. gtood from the annexed Figure (96). The piston moves in a cylinder closed at the top in the usual manner, with an opening at the side for fixing it to the vessel to be exhaust- £*£} ed, and another provided with a valve through which the air is expelled. When the piston is made to descend, the air be- tween it and the opening being compressed, its elasticity is so much increased that it pushes open the valve and escapes, but no air can enter again with the returning stroke \y\ of the piston, the valve being placed so as to prevent this, while it allows any air within to pass easily outwards. But the air in the flask, (which must be screwed to the open- ing next the top,) expands as the piston descends, and divides itself between the flask and the space included within the cylinder (between the upper part of it and the piston ;) with the returning stroke of the piston it is compressed to its original volume, but expands again as be- fore when the piston passes the opening ; and the second time it descends, the air now included in the cylinder is forced out in the same manner as the air it at first contained, and by every succeeding descent of the piston, an additional quantity of air is extracted, though it is impossible in this manner to procure an absolute vacuum. Fig. 97 represents the valve. 1346. Air is extracted from the receiver of the common air Fig. 98. pump exactly on the same principle. The annexed figure (98) represents the arrangement of the apparatus for the slow evaporation of liquids in vacuo by means of the air-pump, and for performing Pro- fessor Leslie's experiment of freezing water by the cold produced by its own evaporation. A shallow glass plate filled to the depth of half an inch with strong sulphuric acid is placed on the brass plate, and a stand for supporting the watery solution to be evaporated is placed above it, resting LUTES AND CEMENTS. 457 on legs made of glass or some other substance that is not af- fected by the acid. A receiver is then placed over it, and the air extracted in the usual manner. When the barometer gage connected with the air-pump rises to about thirty inches, it will be unnecessary to work it any longer when the air-pump is good, the sulphuric acid condensing the watery vapour as it is formed, so that more is immediately produced. A porous earthen vessel must be used in freezing water by the cold pro- duced by its own evaporation, part of the liquid exuding and presenting in this manner a more extensive surface, which fa- cilitates the evaporation.* CHAP. III. LUTES AND CEMENTS. 134<7. A great variety of lutes and cements are required for different chemical operations, and as most of those that are peculiar to particular processes have been already described along with the method of applying them, it will be sufficient in this place to state those that are more generally useful. They are employed principally with the view of rendering joinings tight so as to confine liquids or gases, or to give sup- port to and protect from the action of the fire vessels that are apt to be destroyed by exposure to a high temperature. 1348. In a great number of operations joints may be made sufficiently air tight by a paste made of linseed meal, pease meal, flour or starch (using hot water with the latter), covering them occasionally where it may be necessary with a small piece of linen cloth dipped in prepared glue, which may be rendered still more secure by tying a stout thread round them. Small slips of bladder or gum paper will often be found sufficient for all that is required. Powdered gum is frequently used, and a strong solution of it in water should always be kept, which may be thickened with finely pounded chalk to form the chalk * A description of an improved air-pump by Mr. Dunn will be found in the Edinburgh New Philosophical Journal for April 1829. It is much more simple and less expensive than any of the other more perfect forms of tills in. fitrument, and effects as complete an exhaustion. . 458 LUTES AND CEMENTS. lute that has already been so frequently referred to, and which does extremely well for connecting all kinds of glass or earthen tubes that are not to be exposed to a high temperature, or to the action of corrosive liquids or vapours. 1349. Another class of lutes which are used for rendering the joinings of apparatus for experiments with the gases air tight, are composed principally of wax with various quantities of olive oil, resin, oil of turpentine, or other substances of a similar nature. The gas lute referred to in this work is com- posed of one part of wax and three of lard, heating them toge- ther till a fluid of a uniform consistence is obtained. 1350. By increasing or diminishing the proportion of wax, it may be easily rendered of various degrees of consistence, so as to make it more fit for a number of different purposes. 1351. For fixing glass tubes into retorts or bottles not to be exposed to the action of corrosive liquids, common sealing wax may be employed, tying the glass tube round with thread till it fits the aperture in which it is to be fixed. A better cement for this purpose, however, is obtained by melting bees wax with an eighth part of common turpentine, which may be made into sticks like sealing wax, melting it and spreading it with a hot iron when required for use. It is less brittle than common sealing wax, and by using a larger portion of turpen- tine, a soft cement may be obtained, very useful for closing bottles accurately that contain substances which must not be exposed to the action of the air. 1352. Four parts of resin melted with one of bees wax and mixed with one part of brick dust, give a cement that is much employed in joining pieces of apparatus that are to be per- manently fixed together. 1353. Varnishes may often be employed with advantage for rendering a number of joinings tight, as in fastening a bladder or oiled silk bag to a stop-cock, dipping a piece of stout linen cloth in them, and tying it with thread after rolling it round. Thick copal varnish made by dissolving copal in oil of turpentine will be found better adapted for this purpose than most other kinds of varnishes ; it should be purchased from the painters, as the student will find considerable diffi- culty in preparing it. LUTES AND CEMENTS. 450 1354. To confine acrid vapours, glaziers putty may be em- ployed ; it is made by beating up chalk with drying linseed oil, and is similar in its qualities to the fat lute, as it is termed, which is made by treating clay in the same manner after drying it thoroughly and reducing it to a fine powder. 1355. A great number of useful lutes and cements are made by mixing lime with mucilaginous, albuminous, and gelatinous liquids. Slaked lime in fine powder made into a paste with the white of an egg after beating it in a cup, or with a strong solution of glue, sets very quickly and may be applied most conveniently by spreading it on slips of cloth. 1356. Plaster of Paris is used in the manner described in the note at page 55 ; and by mixing it up with a mucila- ginous liquid, or a solution of gelatine instead of water, it may be kept for a longer time before it begins to set. 1357. For coating glass vessels so as to enable them to bear a red heat, a mixture of dry sand, powdered clay, and cut thread is to be made into a stiff paste with water, using no more clay than is necessary to make the sand adhere, and mixing the cut thread with the other materials before adding any water ; the paste is then to be put equally round the re- tort and allowed to dry slowly before it is used. Thin iron wire wrapped round the coating serves to bind it together when it becomes hot. 1358. If an iron or earthen vessel is to be coated before ex- posing it to a high temperature, the directions already given for coating the iron retort used for the preparation of potassium show the best method of proceeding in cases of this kind. Most earthen vessels become very porous, however, at a high tem- perature, and in particular processes a great portion of the products that would otherwise be obtained are lost. To ob- viate this ; Mr. Willis succeeded in preparing a lute which is well known by his name ; the following is the method of ap- plying it. An ounce of borax is to be dissolved in half a pint of water, and slaked lime added to the solution till a thin paste is obtained. This is to be spread over the retort with a brush, and covered when dry with a lute made of linseed oil and slaked lime. It may then be put aside for a day or two to dry slowly, when it will be fit for use. The first coating 460 OF THE BLOW-PIPE. fuses at a high temperature, and forms a glazing over the earthen retort that prevents vapours from passing through it during distillation, and the second protects it from the fuel, and renders it less liable to be broken as it cools. CHAP. IV. OF THE BLOW-PIPE. 1359- The blow-pipe is an instrument of great value, both to the practical chemist and the student, assisting the former in his analytical investigations, and often enabling him to obtain in a few minutes, and without the assistance of any more compli- cated apparatus, all the information he may desire, while the student who knows how to use it, may, at little or no expense, either of time or materials, perform a very wide and interest- ing range of experiments, which will impress upon his mind the most important chemical relations of the materials with which he operates. It is also the instrument with which tube apparatus is made, which will be attended to in the following chapter. 1360. For all ordinary purposes, a common brass blow-pipe will be found quite sufficient, if it be well made, and the aper- ture at the extremity, which need not exceed the fortieth of an inch in diameter, round and smooth ; it should be tipped with Figs. 99. 100. 101. ivory, Fig.! 102. ^ where it is held in the mouth. 3 shows the common form of this blow-pipe. Fig. 1 00 represents Dr.BlacFs blow-pipe, the hollow conical vessel serving not only to condense the mois- ture of the breath, which is often found troublesome in working with the com- mon blow-pipe, but also to regulate the pressure. Fig. 101 shows Dr. Wollas- ton's blow-pipe, the extremity of which, has a platina nozzle and which can be taken to pieces that are made so as to fit into one another, and occupy less OF THE BLOW-PIPE. 401 room than a common pencil case, Fig. 102. Glass blow-pipes are also frequently used, but they are very apt to be broken. 1361 . The first thing that the student ought to do with the blow-pipe, should be to learn to keep up a continued blast at a candle with his mouth, while he breathes freely through his nostrils. For this purpose, he must, in the first place, distend his cheeks like a trumpeter, and breathe solely through his nostrils, never allowing his cheeks to collapse. When he can do this easily, he should put a blow-pipe with a very small aperture into his mouth, placing the pointed extremity in the flame of a candle ; during expiration, a small part of the ex- pired air will pass through the tube, and during inspiration, also, air will continue to pass through the tube, if he shall have made his cheeks sufficiently tense and elastic, by distend- ing them previously with air, and the same process goes on at each successive expiration and inspiration. Such is the me- chanical rule for learning the method of keeping up a conti- nued blast of air with this instrument, which I have seldom seen fail in enabling the beginner to acquire this art in five or ten minutes, and as considerable practice is necessary before he can be able to use it freely, he cannot commence too early with it. At first, he should take it up frequently at intervals of an hour or two, and not continue working with it for more than a quarter of an hour ; he will soon, however, learn to keep up a continued blast without any difficulty, or distending his cheeks so much as to make it feel tiresome. It is neces- sary, indeed, to do so, only when he begins, as he will not otherwise be able to acquire the method of blowing speedily. 1362. During inspiration, the passages connecting the mouth with the lungs and the nostrils, are completely closed, and the blast kept up solely by the air, from the reservoir within the cheeks, from which it is pressed out by the contrac- tion of the muscles, and the stock renewed at each successive expiration. 1363. The flame of an oil or spirit lamp, or of a large can- dle, does very well for blow -pipe experiments ; but nothing will be found so convenient as a gas lamp, which is not only easily managed, and requires none of the trouble necessary for 462 OF THE BLOW-PIPE. adjusting the others, but allows the flame to be increased or diminished to any convenient size, by merely turning the stop- Fig. 103. cock. The figure represents a gas lamp constructed for blow-pipe expe- riments, which I have now used for several years. It is connected by a flexible tube, fitted to the lower part with the main pipe supplying the rooms with gas ; and when it is on full cock, it gives a flame about three inches long, and an inch and a half broad, the gas escaping through a double row of small apertures, placed along the top. With a little practice, the whole of this flame may be easily thrown into one blast with a common blow-pipe having a larger nozzle than usual, and the heat produced is so great, that a piece of silver of the size of a shilling may be melted in it in a few seconds, though held in the open air by a pair of pincers, and not supported by any charcoal to increase its power. It is seldom that so large a flame is required ; the blow-pipe is shown in the figure in the manner it should be arranged, when the use of both hands is required in making and adjusting tube apparatus ; the extremity is put through a small ring, made by fixing a bent iron wire in a piece of lead, which is supported to a proper height by blocks of wood placed below. When the height of the flame has been pro- perly adjusted, the position of the extremity of the blow-pipe may be easily regulated by the mouth, while blowing through it, so that both hands are left free for managing the tube ap- paratus. The same contrivance may be adopted also in ope- rating with an oil or spirit lamp. 1364. When it is necessary to heat an extensive surface, a blow-pipe with a wider aperture should be used, and held at a little distance from the flame, or the blast made to strike upon the wick, when a lamp or candle is employed. On the other hand, when it is necessary to concentrate the heat upon a sin- gle point, the extremity of the blow-pipe should be introduced a little way within the flame, so as to give a well-defined and luminous cone, surrounded by a wavering flame, which pro- OF THE BLOW-PIPE. 463 jects beyond it ; the interior portion has a blue colour, while the exterior is much lighter, and possesses very different pro- perties, the point of greatest heat being at the extremity of the interior or blue cone. 1365. The inner flame is usually termed the deoxidating flame, containing less air than is necessary for the combustion of the inflammable matter, of which it is principally composed ; any substance that is placed within it being subjected, not on- ly to a high temperature, but also to the action of the excess of inflammable matter, which has a great affinity for oxygen. Any substance placed in the exterior flame, again, which, con- tains more air than is necessary for the combustion of the in- flammable matter, is exposed to the action of the excess of oxygen at a high temperature, and it is accordingly usually termed the oxidating flame. 1366. The effect produced by the flame of the blow-pipe, depends very much not only upon the management of the flame, but also upon the nature of the support on which the substances that may be examined with this instrurrient are placed. A charcoal support not only increases the heat, but assists materially in deoxidating a number of ^compounds. Supports made of earthenware, again, favour the action of the oxidating flame. A small platina spoon, (Fig. 104) is often necessary, and platina foil and platina wire are frequently employed. 1367- Alder wood charcoal is better than most other kinds, being very soft, and easily procured free from rents ; when common charcoal is used, the bark should be carefully remov- ed, as it is extremely apt to fly off in sparks before the flame of the blow-pipe, occasioning serious injury to the eyes. For a support of earthenware, flat tiles of fire clay are very useful, Fig. 105. which may be made about six inches square, and half an inch thick, breaking a small piece of one i of these, about the size of a shilling with a hammer t, the rough fractured surface always presents some point or depression on which the substance to be operated with may be placed. Pumice stone is frequently employed for the same purpose, but is too porous for a number of operations. ^ 464 OF THE BLOW-IMIE. Fig. 106. 1368. Though the mouth blow-pipe is sufficient for all or- dinary purposes, many contrivances have been made for in- creasing its power, and avoiding the necessity of supplying the stream of air for the blast by the lungs, one or two of which may now be mentioned, along with some useful modifications in the method of applying the heat. 1369- In the water pressure blow-pipe, the method of con- structing which will be understood from the annexed figure* a cylindrical iron vessel is placed within a cistern of water, two tubes being fitted to the upper part, and a wide opening made below, so that there may be a free communication between the water within the cylinder, and the rest of the wa- ter in the cistern. When the bellows are worked, air is forced into the cylinder through the tube connected with them, a-, valve preventing its return, the water forced out of the cy- linder rising in the cistern. On opening the stop-cock con- nected with the other tube attached to the top of the cylinder, the water returns slowly to its ori- ginal level, and if made to pass through a blow- pipe aperture of the usual size, a cylinder capable of containing a cubic foot of air,, will give a continued stream of air for upwards of ten minutes, which may be renewed from time to time, as it is required. A large lamp should be used with this blow-pipe, the wick being made about an inch thick, and se- parated at the top to the depth of a quarter of an inch to ex- tend the flame, the point of the nozzle, which is usually made of glass, being introduced a little way within it. The glass nozzle is fitted to the bent brass tube, (continuous with the upper part of the stop-cock,) merely by tying it round with* thread, and pressing it gently in, when it has been made to fit to it. The stop-cock is fixed in a ball and socket-joint, so> that it may be moved easily in any direction. XH M ^S^ X^ fA yy i i i i ST X A iWKSmz gpfi j -> X c : ! i | ,%X~ l" -xx L / X OF THE BLOW-PiriS. 4& 1370. In the oxyhyclrogen blow-pipe, a mixture of oxygen and hydrogen gases is inflamed as it issues from a brass noz- zle connected with two flexible tubes, one supplying oxygen, and another hydrogen, from separate gasometers. The hydro- gen should be put on first and inflamed, and the oxygen allow- ed to mix gradually with it, increasing the quantity slowly, till the large flame of the hydrogen is reduced to a small pale blue pencil. Iron wire is melted instantly when held in this flame, and by directing it upon a small piece of any solid substance, we can expose it to a higher temperature than in any other way, except by subjecting it to the action of a powerful galva- nic battery. 1371- The gases have sometimes been mixed in the same gasometer, and many contrivances have been made to pre- vent the flame returning through the nozzle, which would cause a violent and dangerous explosion ; but though se- veral of them are extremely ingenious, and must obviate every chance of explosion in the hands of an operator who has had some experience, it will be proper for the beginner to use a separate gasometer for each of the gases, allowing them to mingle only in the nozzle into which the flexible tubes are fixed. In most cases, the operator will have sufficient command over this blow-pipe by merely holding the nozzle in his hand ; A support will often be found useful, however, which may be constructed in the manner represented in the figure. It consists of a brass stand, with a move- able brass rod made to slide up and down in it, and which can be adjusted to any height by a screw fixed to the side. On the top of this rod, there is a moveable joint supporting a sheath for the brass noz- zle, so that by moving the sheath, or turn- ing round the brass rod in the stand, the nozzle may be made to point in any direc- tion, and kept steadily in any position in which it may be required. 2 H ^k 466 OF THE BLOW-PIPE. 1372. For a full detail with respect to the method of using the mouth blow-pipe, I must refer to the treatises which have been written on this subject, mentioning only a few experi- ments which will enable the beginner to commence experi- ments with it, and subjoining a table of the effects which it pro- duces on inorganic substances, taken from Mr. Children's translation of BerzehWs Essay on the use of the Blow-pipe. The size of the substance submitted to the flame of the blow- pipe need not be larger than a pea, and in most cases it will be found advantageous to take a much smaller portion; this, however, must be regulated in a great measure by the nature of the substance to be operated on, the size of the flame which can be commanded, and the dexterity of the experimenter. 1373. Take a small piece of lead, not exceeding half a grain, and expose it to the oxidating flame on a fragment of a broken tile (1367) » when it is melted, a beautiful iridescent appear- ance will be seen on its surface, the lead speedily attracting oxygen and being converted into the yellow oxide of lead, which is melted at the same time and forms a glazing over the earthen ware. 1374. Expose another piece of lead to the deoxidating flame, and if it be completely surrounded with this part of the flame, no oxide will be formed. 1375. Put some red oxide of lead on a piece of tile, and expose it to heat in the outer flame ; it will part with a portion of its oxygen at this high temperature, and be converted into the yellow oxide of lead, though surrounded with an excess of oxygen ; but it will not part with any more oxygen, though the heat may be sufficient to melt what remains. 1376. Put another portion of this oxide on a piece of char- coal to assist its reduction by the deoxidating flame ; globules of metallic lead will be immediately obtained. Expose some metallic antimony to heat on charcoal in the usual manner ; it will soon melt, revolve rapidly round its centre, and burn with a pale blue flame, producing a large quantity of white fumes. 1377- Zinc treated in the same manner burns with its characteristic rich coloured flame. Expose some borax to heat on a tile, and continue the heat till the water of crystallization is expelled and a bead of glass obtained. OF THE BLOW-FIl'E. 407 1378. Repeat this several times, mixing the borax succes- sively with portions of the peroxide of copper, peroxide of manganese, oxide of chrome, chloride of gold, and a number of other substances. The glass that is formed in this manner will be rendered bluish green by the peroxide of copper, purple by the peroxide of manganese, green by the oxide of chrome, and of a beautiful pink colour by the chloride of gold. A large piece of borax receives a very deep tint when it is merely touched with a glass rod dipped in a very dilute solution of the chloride of gold. 1379. Expose some metallic tin to the flame of the blow- pipe ; it will soon be melted and acquire a crust of oxide on its surface ; then endeavour to reduce the oxide on charcoal. This will not be easily effected, unless the operator has ac- quired considerable command over the blow-pipe, but if a little carbonate of soda or potassa be put over the oxide of tin, glo- bules of metallic tin may be obtained with great facility. 1380. These experiments will be sufficient to guide the student in studying the subjoined table, from which he should select and perform all those that may appear most interesting. 1381. The great value of Borax as a flux, depends princi- pally upon its tendency to form very fusible compounds with a number of substances, after its water of crystallization has been expelled, from the appearance of which their nature may in general be inferred. Subcarbonate of soda is used for the same purpose, and also to promote the reduction of metallic oxides (1379.) Phosphate of soda and ammonia (salt of phos- phorus) is prepared by mixing equal parts of phosphate of soda and phosphate of ammonia in solution, crystallizing af- terwards by evaporation, or exposure to heat at the blow-pipe ; the ammonia is disengaged, and the excess of acid now in com- bination with the soda, combines with salifiable bases, and renders them more easily fusible. Nitre imparts oxygen readily; Tin, again, is used as a deoxidating agent ; Iron precipitates many metals, as copper, lead, and antimony ; and Nitrate of Cobalt serves to distinguish alumina from mag- nesia, producing a blue colour with the one, and a rose red with the other. SYNOPTIC TABLE THE PRINCIPAL CHARACTERS OF THE EARTHS AND METALLIC OXIDES BEFORE THE BLOW-PIPE, EXTRACTED FROM BERZE- LIUS' TREATISE ON THE BLOW-PIPE, AS TRANSLATED BY MR. CHILDREN. Abbreviations. — O. F. Oxidating Flame. — R. F. Reducing or Deoxidating Flame. — == parts, Equal parts of the Assay and Flux. — N. C. Nitrate of Cobalt. — Fl. Flaming. — C. under the column of either of the Fluxes, means that the support is charcoal. P. F. Platina Foil. P. W. Platina Wire A Brace {, refers to the first column only, and includes all those which are con- tained in the space it comprehends. Heated alone on Assay. Platina. Charcoal. 1. Alkalies, 2. Baryta, . . 2. Infusible. 2. Infusible. a. Hydrate, . . a. Bubbles up and fuses. a. Is absorbed. b. Carbonate, 1. Fuses readily into a b. Becomes caustic and clear glass enamel, is absorbed. white on cooling. 3. Strontia, . . • 3. Infusible. 3. Infusible. o. Hydrate. . . a. Like baryta. b. Carbonate, . b. Fuses with moderate heat at the surface, —great brilliancy ; tinges strong R. F. red ; becomes alka- line. 4. Lime, 4. No change. a. Carbonate, a. Becomes caustic and alkaline ; emits bril- liant white light. SYNOPTIC TABLE. 469 Heated alone on Assay. Platina, Charcoal, 5. Magnesia, . . 5. No change. 5. No change. 6. Alumina, ., 6. No change. 6. No change. 7. Glucina, . • 7. No change. 7. No change. 8. Yttria, 8. Like Glucina. 8. Like Glucina. 9. Zircona, 9. Infusible ; emits in- 9. Infusible, emits in- tense light. tense light. 10. Silica, 10. No change. 10. No change. 11. Molybdic acid, . 11. Fumes and fuses; 11. Fuses, and is ab- brown-yellow on cool- sorbed, and partly re- ing ; in R. F. blue ; duced. intense heat, brown. 12. Tungstic acid, 12. R. F. blackens, but not reduced. 12. The same. 13. Oxide of chrome, 13. No change. 13. The same. 14. Antimony, 14. Fuses readily ; white fumes, which condense into pearly crystals. x. Oxide of Antimony, a. Fuses readily, and a. Fuses readily, and sublimes in white reduces ; colours the fumes ; precipitated flame greenish. oxide burns like tin- der into antimonious acid. I. Antimonious Acid, b. Does not fuse, nor reduce ; gives a bright light. c. Antimonic acid, c.Whitens ; is changed to antimonious acid. 15. Oxide of Tellurium, 15. F. fuses and fumes. 15. Fuses, effervesces, and reduces. 16. Oxide of Columbium. 16. No change. 16. The same. 17. Oxide of Titanium, 17. No change. 17. The same. 18. Oxides of Uranium, 18. Peroxide becomes protoxide ; blackens, but does not fuse. 19- Oxides of Cerium, 19. Protoxide becomes 19. Peroxide does not Peroxide. alter. 20. Oxide of Manganese, 20. Not fused ; becomes brown in a strongheat. 21. Oxide of Zinc, 21. Yellow while hot; white when cold ; does not fuse, but gives out great light when very hot, and white fumes, which condense like wool. 22. Oxide of Cadmium, 22. F. no change. 22. Soon dissipates, leaves a red or orange yellow powder on the char- coal. 23. Oxide of Iron, 23. 0. F. no change. 23. R. F. blackens, and becomes magnetic. 24. Oxide of Cobalt, 24. No change. 24. The same. 25. Oxide of Nickel, 25. No change. 25. The same. 470 SYNOPTIC TABLE. SYNOPTIC TABLE. 471 Assay. 4. Lime, . . a. Carbonate, 5. Magnesia, 6. Alumina, f. Glucina, 8. Yttria, 9. .Zircona, 10. Silica. ll.MolybdicAcid, 4. J No sensible a. ( quantity dis 12. TungsticAcid, 13. Oxide of Chronie. Soda. Heated with Fluxes. Borax. Salt of Phosphorus. quantity solved. 5. No action. 6. Swells up ; forms an infusi- ble compound. '• No action. 8. Like Glucina. 9. Similar to Glu- cina. 10. Fuses with brisk efferves- cence ; clear glass. 11. P. W. effer- vesces, clear glass ; becomes milky on cool- ing. C. fuses, absorbed and reduced. 12. P. W. dark yellow glass ; crystallizes on cooling: opaque white or yellow- ish. C.andR.F. reduced. 13.P.W. and O.F. dark orange glass : opaque and yellow on cooling. R.F. opaque; glass green on cooling. C. absorbed, but not reduced. 4. Clear glass ; opaque by FL a. fuses with ef- fervescence ; with more car bonate clear glass ; crystal lizes on cooling 5. Like lime. Fuses slowly ; permanently clear glass. 7. Clear glass, with a large propor- tion of the assay; opaque by Fl. 8. Like Glucina. 9. Like Glucina. 10. Fuses very slowly ; perma- nently clear glass. 11. P. W. clear glass in O. F. C. and in R. F. glass becomes dirty brown, but not opaque. 12. P. W. and O.F. clear glass : not opaque by Fl R. F. glass becomes yellow, 13. C. fuses dim cultly, glass emerald green ; on P. W. and O. F. the colour flies and glass becomes brown yellow ; on cool- ing, assumes a faintgreen tinge. 4. Fuses in large quantity ; clear glass. a. fuses with ef- fervescence. 5. Fuses readily : clear glass : satu- rated with mag- nesia, opaque on cooling. 6. Permanently clear glass. 7. As with Borax. 8. Like Glucina. 9. Like Glucina, but dissolves more difficultly. 10. Very small portion dis- solves ; clear glass. 11. P. W. and in O. F. greenish glass while hot; colourless, cold. In R. F. be- comes opaque : dull blue while hot : clear and fine green on cooling. C.same phenomena. 12. O.F. yellowish glass. R.F. fine blue glass. 13. Green glass in both flames. 472 SYNOPTIC TABLE. Heated with Fluxes. Borax. Salt of Phosphorus, 14. Antimony . a. Oxide of An- timony. 15. Oxide of Tel lurium. 16. Oxide of Co- lumbium. 17. Oxide of Ti- tanium. P. W. fuses : clear colourless glass, becomes white on cool- ing. C. is reduced, 15. P. W. colour, less glass; white on cooling. C. reduced. 18. Oxides of Ur. 16. Combines with effervescence, but not fused or reduced. 17. Fuses into a clear dark yel low glass ; white or grey on cool- ing, and crystal- lizes with evo- lution of great heat. C. not reduci ble 18. C brown yel- low ; not fused. t. C. dissolves in large quantity ; glass, yellowish, hot ; almost co- lourless, cold. If saturated, part reduced and sublimed : strong R. F. the glass becomes opaque and greyish. 15. P. W. clear, colourless glass, white on cool- ing. C. becomes grey and opaque, 16. Colourless, clear glass ; be comes opaque by Fl. P.W. and O.F. glass, yellowish, hot, colour flies on cooling. 15. The same. 16. Fuses easily ; glass, perma- nently clear. 19. Oxides of Ce- rium. 17. P. W. fuses easily : glass co, lourless ; be- comes milk white by Fl. R.F. glass as. sumes a dark amethyst colour but transparent. In large quan- tity on C. and R. F. glass, dull yellow ; when cold, deep blue. 18. P. W. dark yellow glass ; in R. *F. becomes dirty green. 19. C. not fused, soda absorbed ; white or grey white protoxide remains on the surface. 19. O. F. fine red, or deep orange yellow glass ; colour flies on cooling ; cold, yellowish tint Enamel white by Fl. In R. F. loses its colour. 17. O.F. clear, co- lourless glass. R. F. and on C. glass, yel- lowish, hot; on cooling, first red, then very fine bluish vio- let. 18.P.W.andO.F. clear yellow glass ; cold, straw yellow, slightly green. C. and R. F. fine green glass. 19. O. F. fine red glass ; colour- less when cold, and quite lim- pid. SYNOPTIC TABLE. 473 Assay. 20. Oxide of Man. ganese. 21. Oxide of Zinc. 22. Oxide of cad- mium. 23. Oxide of Iron. Soda. 24. Oxide of co- balt. 25. Oxide of Nic kel. 26. Bismuth. a. Oxide of Bis muth. 27. Oxides of Tin. 20. P. F. fuses, green glass, clear ; cold, bluish green. C. not reduced. 21. C. not fused, but reduced, with flame ; white fumes which cover the charcoal. 22. P. W. not fused C. reduced, sublimes, and leaves a circular yellowish mark. 23. C. absorbed and reduced not fused. 20. O.F.clear ame- thyst colour glass ; colour flies in R. F. 21. O. F. fuses easily, clear glass becomes milky by Fl. 24. P.W. pale red by transmitted light ; grey, cold. 25. C. absorbed and reduced ; not fused. Heated with Fluxes. Eorax. Salt of Phosphorus. 20. The same, but colour not so deep. Infusion in O. F. boils and gives off gas. In R. F. fuses quietly. 21. Nearly the same. 22. P. F. yellow ish glass, colour flies on cooling ; on C. glass bub. bles, cadmium reduced, sub. limes and leaves yellow oxide. 23. O. F. dull red glass becomes clear and yel- lowish or col- ourless by cool- ing. C.andR.F. bot- tle green glass, or bluish green. 24. Fuses readily, deep blue glass. 22. Dissolves in large quanti- ties, clear glass; on cooling, milk white. 23. Similar to bo- rax. 27. P. W. effer. vesces, tumified infusible mass. C. readily re duced. 25. O. F. orange yellow, or red- dish glass ; be comes yellow or nearly colour. less on cooling. a. O. F. colour, less glass. R. F. partly reduced, muddy greyish glass. 27. Fuses with great difficulty ; permanently clear glass. 24. The same, the colour appears violet by candle light. 25. As with bo- rax, but the co- lour flies almost wholly on cool- ing. a. O. F. yellow- ish-brown glass, hot ; colourless, but not quite clear, cold. R. F. clear and colourless glass, hot ; opaque, and greyish black, cold. 27. As with bo- 474 SYNOPTIC TABLE. Assay. Soda. Heated with Fluxe Borax. Salt of Phosphorus. 1 28. Oxide of Lead 29. Oxide of Cop- per. 30. Oxide of Sil- ver. 28. P. W. clear glass becomes yellowish and opaque on cool- ing. C. instantly reduced. 29. P. W. fine green glass, hot; on cooling co- lourless and opaque. C. absorbed and reduced. 28. P. W. clear glass, yellow, hot ; on cooling colourless. C. flows over the surface and reduces. 29. O. F. fine green glass, which in R. F. becomes colour- less, hot ; but cinnabar-red and opaque when solid. 30. O. F. glass becomes milky, or opaline, on cooling. R. F. greyish. 28. Clear colour- less glass. 29. 0. F. similar to borax. R. F. glass usually red, opaque, and like an enamel. 30. O. F. yellow- ish glass viewed by transmitted light by day, by candle light reddish. R. F. greyish. Assay. With other Re-agents. Remarks. 1. Alkalies, 2. Baryta, a. Hydrate, b. Carbonate, 3. Strontia, a. Hydrate, b. Carbonate, 4. Lime, a. Carbonate, 5. Magnesia, 2. ( N. C. ; a globule of a. -j different shades b. 1 of red; colour flies on cooling. 3. r N. C. exhibit a a. J blackish colour; b. (^ do not fuse. 4. f N. C. black or dark a. 1 grey mass, infusi- ble. 5. N. C. ; flesh colour when quite cold. I. The Alkalies are not readily distinguishable by the blow-pipe. Li- thia leaves a dull yel- low stain, when heat- ed to redness on plati- na foil. Ammonia may be known by heating the assay with soda; it gives off a pungent vapour, which turns the yellow colour of moistened turmeric paper brown. SYNOPTIC TAJ? L1C. 475 Assay. G. Alumina, . 7. Glucina 10. Silica, 11. Molybdic acid, 6. N. C. fine blue glass, with strong heat when cold. 7. N. C. ; black, or dark grey mass. 10. N. C. ; blue glass when perfectly fused. 12. Tungstic acid, 14. Antimony, With other Ue-aprenls. 6. The blue colour is only distinctly seen by day light. «. Oxide of Antimony, b. Antimonious acid, c. Antimonic acid, 15. Oxide of Tellurium, 17. Oxide of Titanium, 20. Oxide of Manganese, 23. Oxide of iron, 17- N. C. black or grey, ish black. Remarks. 10. The part not perfect, ly fused with nitrate of cobalt, has a reddish blue disagreeable co- lour. 11. In the inclined glass tube, fuses, gives off vapour, which con- denses partly on the tube as a white powder partly on the assay in brilliant pale yellow crystals. 12. If tungstic acid con- tain iron, the glass with salt of phospho- rus is blood-red in 11. F. Tin makes it green or blue. 14. Antimony does not sublime at the fusing point of glass. On charcoal, when red, ignition continues spontaneously. In a tube open at both ends, it gives off white fumes. f The oxides and b. < acids of antimony C behave alike with the fluxes. 15. Metallic tellurium heated in a glass mat- trass, first gives off vapour, and then a grey metallic sublimate of tellurium. In a tube open at both ends, emits abundant fumes, which condense in a white fusible powder. 20. A very minute por- tion of manganese gives a green glass with so- da. 23. The reduction of iron from the peroxide to protoxide, is facili- tated by tin. 476 SYNOPTIC TABLE. With other Re-agents. Remarks. 24. Oxide of Cobalt, 26. Bismuth, 24. With sub-carbonate of potassa, black glass when cold. 30. Mercury, 32. Gold, 33. Platina, 34. Iridium, 35. Rhodium, 36. Palladium, ! 26. In a glass mattrass does not sublime at the fusing point of glass. In an open tube scarcely gives off any fumes; the metal be comes covered with a dull brown fused ox- ide, of a slight yellow- ish tint, when cold. 30. All the compounds of mercury are vola tile ; mixed with tin or iron filings, and heated in a glass tube, metallic mercury dis- tills over. 32.~\ These metals have 33. f no action on the 34. V fluxes, which can 35. 1 only serve to de. 36.,/ tect the foreign metals with which they may be combined They are best examin- ed by cupellation with lead. TUBE APPARATUS. 477 CHAP. V. TUBE APPARATUS. 1382. Next to the blow-pipe, there is no piece of appa- ratus which the student can procure, however costly, that will be of so much use to him as a case of test tubes. Although with these he can neither operate on a large quantity of ma- terials, nor be so exact with respect to the relative quantity of the substances that are brought to act on each other, still there are perhaps few chemical experiments where glass ves- sels are required, which cannot be imitated with this apparatus, so as to give the student an opportunity of seeing the manner in which they may be formed on a large scale when he may not have time or opportunities for using more appropriate apparatus. 1383. A case of test tubes should include seven or eight of different sizes for miscellaneous opera- tions ; a small funnel of a corresponding size ; a longer test tube bent so that it may be used as a retort ; and several tubes with balls blown at the ex- tremity. Fig. 108 represents the size and form of the test tubes I find most convenient, being made of thin flint glass. Fig. 109 repre- sents a wooden case for holding them, which may be made about four and a half inches long, three and a half inches broad, and one and a half inch thick ; and Fig. 110 shows the form of another stand for holding glass rods, long test tubes, tubes with balls, &c. It should be about ten inches long, and six inches broad, a space of three or four inches intervening between the upper and lower boards of which it is made. ^ Fig. 109. /OOOOO/ /ooooo/ /OOOOO/ 'ooooo/ 478 TUBE APPARATUS. 1384. A spirit lamp will in general be found most conveni- ent for heating liquids or solids in test tubes ; but when any mixture is to be sublimed in a large tube, it will often be more convenient to place it in a horizontal position across the top of a chauffer, having a piece cut Out at the side in the manner Fig. ill. seen in Fig. Ill, and coating it with a mixture of sand and clay when it is to be exposed to Qa high temperature. A chim- xjj l°^oo3 ne y ma y be P ut above Jt ' if ne ~ cessary, surrounding the coated tube completely with small pieces of charcoal. 1385. It will also be found advantageous occasionally to have some other pieces of apparatus constructed on a smaller scale, which may be used in connection with the tubes them- selves. Thus an apparatus such as is represent- ed in the annexed figure, will be found useful in Fig. 112. operating with solutions with which the student may exercise himself in endeavouring to detect small quantities of arsenic, lead, antimony, opium, and other poisonous substances in mixed ( ^-^ ) liquids, preparing sulphureted hydrogen in it, though it should not be more than an inch or an inch and a half in diameter, and transmitting it through the liquid on which he is operating in a wine glass, as in the process for precipitating sulphurets of arsenic, lead, and antimony, or for decomposing the meconiate of lead precipitated by a solution of the acetate from a very diluted solution of the tincture of opium, so as to separate the meconic acid. 1386. To make a common test tube, the flame of the blow- pipe must be directed upon a proper piece of tube, at the dis- tance of four or five inches from one of its extremities, turning it constantly round that it may be exposed equally on all sides to the action of the heat ; and drawing the one portion away from the other slowly ; by directing the flame upon the closed end of the tube, and heating it till it is soft, it may ELECTRICITY AND GALVANISM. 479 be made smooth and uniform in its appearance on blowing into it.* CHAP. VI. ELECTRICITY AND GALVANISM. 1387- An electrophorus, or small electrical machine, will be quite sufficient for performing the experiments described in this work, in which, it is necessary to transmit an electric spark through an inflammable gaseous mixture, and it is seldom that the electrical machine is required for any other chemical purpose by the student. Fig, 1J3. 1388. The electrophorus (Fig. 113) con- sists of a resinous cake (prepared by melting together equal weights of common resin, shellac, and Venice turpentine, and pouring the compound while still hot upon a metal- lic plate or marble slab), and of a conductor in which the electricity is collected. The resinous cake should be placed upon a me- tallic plate, and struck lightly with a piece of folded warm flannel, (nothing does better than a fox's tail), when required for use. The conductor which is usually made of a piece of thin wood covered with tin-foil, and provided with a glass handle, is to be placed upon the resinous cake, touched with the finger while in this position, and removed by the glass handle ; it will now be charged with electricity, and on bring- ing any substance near it a spark will be given off which may be transmitted through the gaseous mixture to be subjected to its action. Many inflammable gases mixed with oxygen in the proper proportion may be analysed in this manner, the * For a particular description of the method of making tube apparatus, the reader is referred to Mr, Faraday's Treatise on Chemical Manipulations. 480 ELECTRICITY AND GALVANISM. quantity of the resulting products indicating their composition. For this purpose Volta's or lire's eudiometer is generally em- ployed. Fig. 114 1388. Volta's eudiometer (Fig. 114) is made of /'—n a stout glass tube with two platina wires fixed r _>% into it near the top where it is closed, and ap- "" proaching till they are at a very little distance from each other within it. The mixture to be detonat- ed is then introduced into the eudiometer over wa- ter or mercury, as may be necessary, keeping it in an upright position and wiping the upper part with a cloth to remove any adhering water or mer- cury; on connecting one of the wires with the ground by a chain, or touching it with the finger, and bringing the tube near the conductor after it has been properly charg- ed, an electric spark will be immediately transmitted through the mixture, passing between the terminations of the wires within the tube and causing it to explode. 1389- If it be required to examine any of the resulting pro- ducts the tube should not be filled more than a third full, and depressed in the liquid to prevent any of the contents being thrown out. Fig. lis. o o W 1390. Dr. lire's eudiometer (Fig. 115) is more convenient than Volta's for detonating small quan- tities of inflammable mixtures by means of the elec- tric spark. It consists of a bent tube, closed at one end, with wires fixed into it in the usual man- ner ; the mixture is introduced after filling it with mercury, after which the greater portion of the liquid still remaining in the open extremity of the tube is poured out ; it is then placed in the position repre- sented in the cut. One or both of the wires should terminate in a brass ball without the eudiometer, that a larger spark may be drawn from the conductor than can be obtained with the wire alone. 1391. Close the open end with the thumb which is to be placed so as to touch one of the balls ; charge the conductor and apply it to the other end. The gaseous mixture at the ELECTRICITY AND GALVANISM. 481 top expands as the spark passes through it, and presses upon the mercury below, forcing a portion of it into the other ex- tremity of the tube, where the air acts as a spring, and mo- derates the violence of the explosion. It is necessary to leave as much mercury in the open extremity as will completely fill the other should a complete condensation accompany the de- tonation. 1392. Should the spark not be sufficiently strong to inflame the mixture a larger quantity of electricity must be collected in a leaden jar by charging the conductor repeatedly, and bringing it in contact with the ball at the top, discharging it in the usual manner. 1393. When it is required to pass a strong electric spark through any substance, a discharger constructed for the purpose should be employed ; these are made of various sizes and forms, the figure represents a temporary one made byfixing two pieces of p. 116 brass rod to the rings of two retort stands with iron wire, ,' — N and the manner in which it is used. One end of a chain is connected with one J of the retort stands, the y' other end being placed be- \ low the Ley den jar after it } has been charged ; the sub- >•* stance through which the C£=2> electricity is to be passed is then placed on a piece of wood or an earthen dish, and the points of the brass rods brought into contact on either side. Another chain is then to be fixed to the second stand, attaching one end of it to a common elec- trical discharger, and on completing the circuit by bringing it in contact with the ball of the Leyden jar, the electricity im- mediately passes through the substance placed between the brass wires. 1394. By proceeding in this manner a number of substan- ces may be easily inflamed or decomposed. Thus, if some powdered resin be thrown on some cotton and placed in the 2 i n*rv 482 GALVANIC BATTER Y. position we have just described, it will immediately take fire on completing the circuit, and fulminating silver and mercury may be exploded in the same manner. GALVANIC BATTERY. 1395. The galvanic battery is much more frequently em- ployed than the electrical machine for chemical purposes, and though a variety of improvements have been made of late in the method of constructing apparatus of this kind, perhaps there is no modification of it that will be found more conve- nient for performing a few experiments than the common gal- vanic trough, in which the plates are arranged in a horizontal position in the manner proposed by Mr. Cruickshanks. There are few experiments which cannot be performed with 120 plates, each about four or six inches square charged with acid liquor of different strengths according to the purpose for which it may be required. For ordinary experiments a mixture of 2 parts of sulphuric acid, 1 of nitric acid and 80 of water may be em- ployed, but when it is necessary to produce intense heat or light, 1 part of sulphuric acid may be mixed with 3 of nitric acid and 15 or 20 of water. 1396. When a single pair of plates is employed, the copper is always the positive pole (if an acid liquor be used) the electric current flowing in the man- ner represented in Fig. 117» viz. from the zinc to the copper through the li- quid, and from the copper to the zinc when the wires between the two plates are connected together. 1397- In compound galvanic arrangements the extremity of the battery terminating with the plate of zinc becomes the positive pole ; here, however, it must not be forgotten that depends solely upon the copper plate to which it is fixed ; OAI.VANIC BATTERY 4«:j 1 ' i -- lis - for, as is represented in r ,..,_>. cz the annexed figure, the electric fluid moves from the zinc through the li- quid to the copper, as in the preceding case, and the zinc and the copper plates at the extremity of the battery do not con- tribute in any degree to the action, and might be removed al- together without in any degree affecting it ; still, however, it is useful to have them attached to the other plates, for the purpose of connecting different troughs together. No diffi- culty can be experienced by the student in understanding why the zinc extremity of the battery should be the positive pole in a compound galvanic arrangement ; if he looks on a galvanic trough of the usual construction, he must perceive that it is not by the mutual action of the plates that are sol- dered together and the liquid on either side that the galvanic electricity is produced, but that it is developed by the action of the liquid on the plates between which it is interposed ; these are represented as connected together by the dotted lines in the figure, and the plates at the extremity may be consi- dered merely as a part of the connecting wires. Fig. 119. 1398. When several troughs are to be connected to- gether, great care ~~7j must be taken to '-< place them in such -<0- V a position that the plates shall all be situated in the same manner with respect to each other as if they had been placed in a single trough ; the zinc extremity 484 &ALVANIC BATTERY. of the one being connected with the copper extremity of another ; the figure represents the best method of arranging eight small troughs together so as to have the opposite poles brought within a convenient distance of each other. 1399. To detonate gunpowder, fulminating mercury, or any other compound of a similar nature, the best method of proceeding is to put it on a metallic plate connected by a wire with one of the poles of a battery, touching the upper portion with a similar wire connected with the other extremity. 1400. When leaves of gold, silver, or copper, are to be in- flamed, a thick brass rod bent at right angles, is used to sus- pend them, fixing it at the positive or negative pole of the bat- tery, and touching the metallic leaf with a plate of iron or zinc connected with the other pole of the battery, gilded previously to reflect the light better. 1401. When the galvanic electricity is transmitted through charcoal, small pencils, about two or three inches in length, and one-tenth of an inch in thickness, may be employed ; they are prepared most conveniently by heating pieces of willow, cut to a proper size, in a covered crucible filled with powdered charcoal. A few experiments, illustrating the power of galvanism in effecting decomposition, may be easily performed. 1402. Fill a tube with a diluted solution of sulphate of so- da, and invert it under water, fixing it into an apparatus simi- Fig. 120. lar to what is represented in the annexed figure, (one of the bottles of Woulfe's ap- & paratus may be easily adjusted for this pur- "~"\- ^A. ^^~ pose, if the beginner should not have a rv /? globe with a tube ground to it ;) then put V J two gold or platina wires, (connected with ^y~ (C^ the positive and negative poles of the bat- r tery by copper wires,) into the tubulures at the side through corks, and immediately a stream of gas will rise from both wires, and collect in the tube ; the wires must not close the apertures in the cocks com- pletely, but allow part of the liquid to pass out, as it is displaced by the gas. On examining the mixture, it will GALVANIC BATTERY. 485 be found to be composed of one measure of hydrogen, and half a measure of oxygen, (a portion of water being decom- posed,) which may be easily detonated by withdrawing the tube and applying a light. Oxygen is evolved at the positive, and hydrogen at the negative wire, and they may be collect- ed in separate vessels, by a modification of the apparatus, re- presented in the above figure. Fi S- 121 - 1403. Take two glasses filled with the same diluted solution of the sulphate of soda, connecting them together by a piece of moistened cloth, and putting a wire attached to the positive pole of the battery into one of the glasses, and one connected with the negative pole into the other. Water will be decomposed, as in the preceding experiment, and also the sulphate of soda ; in the preceding experiment, however, the sulphuric acid and soda detached from one another, meet- ing again in the same vessel, immediately combine and form sulphate of soda, so that they cannot be obtained separate from one another ; but in the present case, all the acid passes into the glass connected with the positive pole, and the alkali into the other. If the solution be tinged with a little of the blue infusion of cabbage, the usual changes of colour will take place, and indicate the change that is going on. 1404. By changing the position of the wires, the acid may be made to pass into the glass which previously contained the alkali in excess, while the latter takes the place of the acid. 1 405. In both these experiments, the copper wire connect- ed with the positive pole of the battery, must have a piece of gold or silver wire attached to it, which alone is to be intro- duced into the liquid, a copper wire being speedily oxidated as the water is decomposed, and the oxide combining at the same time with the acid of the sulphate, which is separated at the same pole. ACIDI?.IETltY AND ALKALIMETRY, CHAP. VII. AGIDIMETRY AND ALKALIMETRY. 1406. The method of ascertaining the exact quantity of free acid or alkali in a given weight of any solution or mix- ture of solid substances, is a subject of great importance, as it not only enables us to determine their value in a commercial point of view, but also to adjust the quantities of materials re- quired for different processes and experiments. The strength, indeed, of every acid and alkaline solution used for chemical experiments should be known, and it will be found to save a great deal of time, if the solutions that are employed, are always prepared of the same strength. 1407- To ascertain the strength of any acid, an operation that is now termed Acidimetry, all that is necessary, is to take a given weight of an alkali, and see what quantity it can neutralize. Thus, if we wish to ascertain how much real sul- phuric acid there is in diluted sulphuric acid, we have only to take a given quantity of an alkali, or alkaline carbonate, that of potassa for example, and ascertain what weight of the acid liquid is required to neutralize it ; and as we know that 40 parts of sulphuric acid neutralize exactly 48 of potassa, we must allow 40 parts of acid for every 48 of potassa neutralized. If sub- carbonate of potassa be employed, then every 70 parts neutralized indicate the presence of 40 of acid, containing ex- actly 48 of potassa. 1408. For example, suppose we dissolve 70 grains of the sub- carbonate of potassa in water, and find that it requires exactly 160 grains of the diluted sulphuric acid to neutralize it ; then these 160 grains must have contained exactly 40 of dry sulphuric acid, or 25 per cent. ; consequently, in all experiments where a given weight of acid is required, we must take four times its weight of this solution, to have the proper quantity. 1409- In the same manner, we may easily ascertain the quantity of real acid in most other strong or diluted acid li- ACIDIMET11Y AND ALKALIMETRY. 487 quids ; 48 parts of real potassa (or 'JO of the carbonate) indi- cating the presence of 54 of nitric acid, 37 of muriatic, and quantities of other acids represented by their respective equi- valents, when they are capable of completely neutralizing pot- assa. 1410. It must be obvious, that on the same principle, we may ascertain the quantity of free alkali in any alkaline solid or liquid ; and the process for this purpose has now received the name of Alkalimetry. Thus, if we should wish to ascertain the quantity of soda in a specimen of kelp, the value of which depends principally on the quantity of this ingredient which it contains, we have only to extract all the soluble matter from a given weight of it, — by digesting it in water, washing the resi- duum repeatedly with water, till no more soluble matter is taken up, and in neutralizing the mixed liquids with a dilmted acid of a given strength, we may easily calculate the quantity of free soda which it contains. For example, if the soluble matter extracted from 500 grains of kelp should require 80 grains of diluted sulphuric acid, containing 25 per cent, of real acid, to neutralize it, then they must have contained 16 grains of soda ; for 80 parts of the diluted acid contain 20 of real acid, and 40 of this acid neutralize 32 of soda ; but if 40 of sulphuric acid neutralize 32 of soda, then half the quantity will neutralize 16 of this alkali. 1411. On the same principle the quantity of potassa in pearl ash and potashes may be ascertained, and of real ammo- nia in the water of ammonia, substituting the respective equi- valents of these substances for that of soda. 1412. For ascertaining when the neutralization is complet- ed in these processes, nothing will be found more convenient than the blue infusion of cabbage, as a very slight excess of acid or alkali changes its colour to red or green. Test papers prepared in the manner described in 1129 may be used for the same purpose. 1413. A pure subcarbonate of potassa may be easily pre- pared for these experiments by fusing the crystallized bicar- bonate in a platina crucible. The best method of proceeding, is to pour it out on a clean iron plate after it has been kept in 488 ACIDIMETRY AND ALKALIMETRY. a state of fusion for five or ten minutes in a platina crucible, putting a fragment of it into a small cup of water accur- ately equipoised in a balance, and ascertaining its weight by again counterbalancing the cup. The object of proceeding in this manner is to prevent it gaining any increase of weight by attracting water from the air, and both the cup and the water having been previously balanced, the additional weights re- quired to bring the scales again to an equilibrium represent the exact weight of the fragment put into the water. 141 4. Instead of using the pure subcarbonate, the bicar- bonate itself is occasionally employed for the same purpose, and as every 101 parts contain 48 of potassa, (see the table of equivalents) we must allow 40 parts of sulphuric acid for every 101 parts of this salt which are neutralized. 1415. Crystalized subcarbonate of soda is occasionally used for the same purpose, but the quantity of water of crystalliza- tion in it is said to vary, sometimes containing 10 and some- times 11 equivalents of water, combined with one of the dry subcarbonate. All the specimens of the crystallized subcarbo- nate of soda which I have examined were composed of 10 equi- valents of water and one of the dry subcarbonate of soda. 1416. With respect to the method of measuring the quan- tity of the acid liquid employed in ascertaining the quantity of free alkali in any solution, there are two methods of proceed- ing. According to one, a liquid measure is used divided into tenths of a cubic inch, the diluted acid being made of such a strength, that every tenth of a cubic inch shall contain a suf- ficient quantity of real acid to neutralize half a grain or a grain of potassa or soda. 1417- The other method consists in adding a given weight of the acid to the alkaline solution, and calculating the quan- tities in the manner described. This is the method I am in- clined to prefer, and those who adopt this plan will find it con- venient to proceed in the following manner. Take a glass bottle of a conical form, flat at the bottom and not very tall, that it may rest steadily upon one of the scales of a balance. Put a pipette with a very fine point and some of the test acid with which the strength of the alkaline solution is to be ascer- SPECIFIC GRAVITY. 489 tained into it, and counterpoise this scale with weights, or shot and sand. Then fill the ball of the pipette (1334) with the diluted acid by sucking out part of the air, remove it care- fully, and hold it over the solution to be neutralized in such a manner that the acid liquid shall drop out slowly ; the small- est portion of acid can be added in this manner with facility, and on replacing the pipette after the neutralization of the li- quid, the weights necessary to restore the former equilibrium indicate the quantity of diluted acid employed, from which the strength of the alkaline solution may be calculated as be- fore. CHAP. VIII. METHODS OF ESTIMATING THE SPECIFIC GRAVITIES OF SOLIDS, LIQUIDS, AND GASES. 1418. Water has been fixed upon as the standard of com- parison in estimating specific gravities ; and its specific gravity has been called 1. Fig. 122. 1419. To find the spe- cific gravity of a solid body heavier than water, — First, weigh the solid in air; then weigh it in water by a hydrostatic balance in the manner re- presented in the accom- panying figure, using a very fine thread, or a hair to suspend it from the bottom of the balance. The difference in the re- sults will express the weight of a quantity of water equal in bulk to the solid whose specific gravity is to be deter- mined, and the following proportion will give us its specific gravity in relation to water,— as the weight of the water equal 4-90 SPECIFIC GRAVITIES OF SOLIDS. in bulk to that of the solid is to the weight of the solid itself, so is the specific gravity of water to the specific gravity of the solid. Thus, If the solid weigh 100 grains in air, and 60 grains in water, then 100—60, or 40 : 100 : : 1 : 2.5— The specific gravity of the solid is therefore 2.5 compared with that of water. 1420. If the solid should be lighter than water, a more com- plicated process will be necessary. Attach to the light solid by a slender thread another body of such a weight that when tied together they will sink in water, having previously weighed the heavier solid in water, and each in air ; then weigh them together in water, and from the difference between their weight in water and their weight in air, subtract the difference between the weight of the heavy solid in air and its weight in water — the remainder will show the weight of a quantity, of water equal in bulk to the light body, and we can then find its spe- cific gravity in the way directed above. Thus, If the weight in air of the light solid be 10 and of the heavy solid 20 ; and if the weight of the heavy solid, in water be 18, and of the two together 7? — then From their weight in air, . 20 + 10 = 30 Subtract their weight in water, . . 7 23 And from this subtract 20—18 = 2 2 The remainder ..... 21 will express the weight of a quantity of water equal in bulk to the light solid and the following proportion will give us its specific gravity, 21 : 10 : : 1. : -47619 — the specific gravity of the lighter solid. 1421. Where a hydrostatic balance cannot be procured, the following method may be adopted — weigh the solid and put it into a vessel full of water, the weight of which with the water is known ; the solid will displace a quantity of water equal in bulk to its own ; weigh the vessel again, having SPECIFIC GRAVITIES OF SOLIDS. 491 either taken out the solid body, or put an equal weight in the opposite scale — the difference between the present weight of the vessel, and its former weight will express the weight of a quantity of water equal in bulk to the solid body, from which, by the same proportion as in the former instances, we can estimate the specific gravity of the solid body. Thus if the vessel when full of water weighed 1000, and after some of the water had been displaced by the solid body, it weighed 900 grains — 100 grains of water were displaced by the solid body — and if the solid body in air weighed 300 grains, then the following proportion will give its specific gravity : 100 : 300 : : 1. : 3. 1422. If the solid body be soluble in water, some other fluid, as wine, alcohol, or a saturated solution of the substance itself must be used, its specific gravity being previously ascer- tained. We must first find the specific gravity of the body, considering the fluid used as a standard of comparison, and making the number representing its specific gravity the third term in the proportion, in the same manner as when water is used; and then, by simple, proportion, reduce the product to the standard of water. Thus, if the specific gravity of the fluid used be 1.2, and, considering it as a standard of com- parison, the specific gravity of the body be 1.8, then the fol- lowing proportion will give us its real specific gravity : 1.2:1.8::!. : 1.5. 1423. When the substance, the specific gravity of which is to be ascertained, is in the form of a powder, the following me- thod recommended by Professor Leslie will be found most Fig. 123. convenient. Take a glass tube bf, three feet in a ^ length, and open at both ends. The wide part be is to be about •-$% of an inch in dia- meter, and the narrow part cf about T 2 , com- municating with each other by a very small aper- ture at c, which allows air to pass, but is suffi- ciently small to prevent any powder from going through. The upper opening at b is to be ground, so that it can be accurately closed by a glass plate a. The substance, whose specific gravity is to be determined, is put into the wide part of the A 492 SPECIFIC GRAVITIES OF LIQUIDS. tube & e, after which it is placed in a wider tube containing mercury g, making it descend till the fluid metal shall have reached the aperture at c. Then fix the cover, making it air tight with a very small quantity of lard, and lift it perpen- dicularly out of the mercury till the aperture at c shall have been raised above the surface of the mercury in the tube to a height exactly equal to half the height of the barometer at the time the experiment is made, and mark the point at which the smaller tube is cut by the fluid, which we shall suppose in the present instance to be d. The air within that part of the tube in which the powder has been placed being now subjected to the pressure of only half an atmosphere, it expands to double its former volume, one half still remaining within 6c, while the rest occupies cd, the space it includes representing therefore the total bulk of air included along with the powder in be. The powder is now withdrawn, and the process repeated with be full of air only, when it is obvious that the mercury will not stand so high within the tube cf as before, and supposing it to rise only to e, then the space ce will contain a quantity of expanded air, equal in bulk exactly to what would be contained before lifting up the tube. Since cd then represents a space exactly equal to that within be, and cd a space equal to the volume of air in be when the powder was in it, then de, the difference between them, shows the space occupied by the powder when it was in be. In this manner, then, we are enabled to find out a space exactly equal in bulk to that of the solid matter in the powder, and if the stem is graduated so as to express in grains the quantity of water which it can contain, we have only to weigh the powder in air and compare its weight with that of the equal bulk of water to ascertain its specific gravity. SPECIFIC GRAVITY OF LIQUIDS. 1424. Take a bottle of a known weight, fill it with distilled water, and weigh it carefully ; then pour out the water, and after drying the bottle, fill it with the liquid to be tried. The SPECIFIC GRAVITIES OF GASES. 493 following proportion will give its specific gravity : As the weight of the distilled water, is to the weight of the liquid, so is 1 to the specific gravity required. Thus, if the weight of the distilled water be 150, and that of the liquid 200, the following is the proportion we must use : — 150: 200::!.: 1.333. 1425. The areometer is a convenient instrument for ascer- taining the specific gravities of liquids. It consists of a long, straight graduated stem, on which numbers are marked at the points to which the instrument sinks in liquids of the specific gravities marked at these points. Thus, in distilled water it will sink to 1., and in nitric acid to 1.5. It is made of different materials according to the nature of the liquids whose specific gravities are to be ascertained with it. 1426. Lovrs beads are also very useful for ascertaining the specific gravities of liquids. These are small balls made of glass, with numbers marked on them indicating the specific gravity of those liquids in which they float without any ten- dency either to sink or rise to the top. Those that float on the surface show that the liquid has a greater specific gravity than the number marked on them expresses, while those that sink indicate the reverse, being heavier than an equal bulk of the fluid. SPECIFIC GKAVITY OF GASES. 1427- Atmospheric air is taken as a standard of comparison in estimating the specific gravity of gases, and represented by the number 1. Their specific gravities are found out in the same manner as those of other substances, viz. by comparing the weight of equal bulks of them and of the substance which is taken as a standard of comparison. 1428. For this purpose, a flask provided with a stop-cock is accurately weighed and attached to an air pump or exhaust- ing syringe, which is worked in the usual manner ; and, when the gas whose specific gravity is to be tried has no action on atmospheric air, it is not necessary to exhaust it to a very 494 SPECIFIC GRAVITIES OF GASES. great degree. The stop-cock fixed to the flask is then turned, when it is weighed again to ascertain the quantity of air ex- tracted. It is then screwed on to a jar placed over a pneu- matic trough containing the gas whose specific gravity is to be determined, and on opening the stop-cock, a quantity of gas is forced by the pressure of the atmosphere into the flask, exactly equal in bulk to the air which had been withdrawn, if the jar is depressed in the liquid till it shall be at the same level both within and without. If the flask be then detached from the jar, it is obvious that by weighing it again we can find out the weight of a measure of gas exactly equal in bulk to that of the air whose weight was found out by the first operation. 1429. For example, if the flask should weigh 570 grains when full of air, and 560 after the exhaustion, then the quan- tity of air which has been withdrawn weighs 10 grains. Weight of flask with air 570 grains. Weight of flask after exhaustion.. 560 do. Weight of air withdrawn 10 do. And if it shall weigh 580 grains after admitting an equal volume of the gas whose specific gravity is to be determined, then it must be twice as heavy, or its specific gravity must be twice as great as that of atmospheric air. Weight of flask with gas 580 grains. Weight of flask after exhaustion... 560 do. Weight of gas introduced 20 do. 1430. When the gas whose specific gravity is to be ascer- tained acts chemically on atmospheric air, the latter must be withdrawn as completely as possible by repeated exhaustions filling it after each with some gas which is not affected by the other, and then proceeding in the usual manner. 1431. In all experiments for ascertaining the specific gra- vities of different substances, particularly of gases, great at- tention must be paid to the temperature, as their volume va- ries with the degree of heat to which they are exposed. Ac- WEIGHTS AND MEASURES. 495 cordingly in stating the specific gravities of bodies, the tem- perature at which they have been ascertained is always men- tioned at the same time. 1432. In operating with gases, it is also necessary to attend to the pressure of the atmosphere as indicated by the baro- meter, and the quantity of watery vapour which they may contain. Formulae have been given for making corrections when the barometer is not at the jDoint adopted as a standard of comparison, and for the quantity of watery vapour which they may contain, but it will be unnecessary to insert them here, as it will be sufficient for the beginner to imitate the process by which their specific gravities are ascertained, sup- posing the barometer to indicate the usual pressure, and the gases to be perfectly dry. 1433. It may be also necessary to remark, that when the specific gravity of a gas is ascertained in the manner that has been described, no variation in the pressure of the atmosphere of any consequence can take place in the short space of time necessary for this purpose, and equal bulks of air, and the gas whose specific gravity is to be found out, having been weigh- ed in this manner, precisely under the same circumstances with respect to pressure, no corrections on this account are required. CHAP IX. TABLES OF WEIGHTS AND MEASURES, OF THE CORRES- PONDENCE BETWEEN FAHRENHEIT'S, REAUMUR'S, AND THE CENTIGRADE THERMOMETERS, AND OF FREEZING MIXTURES. Weights and Measures. WEIGHTS. The standard according to which the present system of weights is regulated, is the Troy brass pound, made in 1758, and now in 496 WEIGHTS AND MEASURES. the charge of the Clerk of the House of Commons. It contains 5760 grains. Imperial or Troy Weight. 24 grains == 1 pennyweight, 20 pennyweights = 1 ounce, 12 ounces = 1 pound, or, Grains. Pennyweights. Ounces. Pound. 24 = 1 ' Z= i 2o = i 240 480 — 20 = 1 = 1 12 5760 — 240 ~ 12 — 1 The pound avoirdupois contains 7000 grains, each of which is equal to a Troy grain, being thus heavier than the Troy pound by 1240 grains. 16 drachms 16 ounces 28 pounds 4 quarters 20 cwts. Pounds. 1 Avoirdupois Weight. 1 ounce = 437-5 troy grains. 1 pound = 7000 1 quarter = I96OOO 1 cwt. or 112 lb. = 784000 or, = 1 ton Ounces. = T5 = = 15680000 Drachms. 256, = 16, = 1 . = Troy weight. 7000 grains. 437-5 27-34375 The pound in Apothecaries' weight is equal to the Troy pound, containing 5760 grains, but is differently subdivided. Apothecaries' Weight. 1 pound lb = 12 ounces 1 ounce § = 8 drachms 1 drachm 3 = 3 scruples 1 scruple 9 = 20 grains =: 5760 Troy grains, = 480 = 60 = 20 or, Pounds. Ounces. Drachms. 1 = 12 = 96 = Scruples. 288 = Grains. 5760 1=8 = 24 = 480 1 == 3 = 60 1 — 20 WEIGHTS AND MEASURES. 497 The following tables show the correspondence between the Troy, Avoirdupois, and Apothecaries' Weights. ' oz. = 13 Troy weight. 1 pound 1 ounce — 1 1 pennyweight ss Avoirdupois, dr. grains. 2 17-8125 a 15-1562 = 24- = Apothecaries'. 1 pound. 1 ounce. 1 scruple, 4 grains. Avoirdupois. Troy weight. Apothecaries'. 1 pound s=llb. 2oz^ lldwt. I6gr. = lib. 2oz* 4dr. 2sc. 1 ounce =:=0 18 5-5 =0 7 l7-5gr. I draclnn= 1 3-34 == 1 7-34 Apothecaries'. Troy weight. . Avoirdupois. 1 pound = 1 pound = 13oz. 2dr. 17-8125 gr 1 ounce = 1 ounce = 1 1 15-1562 1 drachm — 2dwt. 12gr. = 2 5-3125 1 scruple = 20 = 20- French Decimal Measure of Weight- Grains. 'Gramme ss 15.4440 Troy Milligramme Centigramme Decigramme Gramme Decagramme Hecatogramme Kilogramme Myriagramme — - .0154 = .1544 = ■ 1.5444 = 15.4440 S3 154.4402 = 1544.4023 = 15444.0234 ss 154440.2344 Lbs. 2 26 IMPERIAL, OR TROY WEIGHT. Ozs. 3 8 9 Dwts. 6 4 3 15 Grains. 15.4 10.44 8.40 12 Measures. The Imperial Standard Gallon contains ten pounds Avoirdupois weight of distilled water, weighed in air at 62° Fall, and 30° Barom., or 277.274 cubic inches — or 121b., 1 ounce, 16 penny- weights, and 16 grains Troy, = 70,000 grains of distilled water. IMPERIAL MEASURE. 1 Quarter = 8 Bushels 1 Bushel == 4 Pecks. 1 Peck • = 2 Gallons. 1 Gallon ss 4 Quarts. 1 Quart = 2 Pints. 2 K 498 WEIGHTS AND MEASURES. or, Troy grs. Avoird. lb. Cub. inch. Pint. Quar. Galls: Pecks. 8750 = 1.25 = 34.659 = 1 17500= 2.5 = 69.318 = 2 = 1 70000 = 10. = 277.274 = 8 = 4=1 20 = 554.548 = 16 = 8=2=1 80 = 2218.192 = 64 = 32 = 8 = 4 Bushels* 1 640 = 17745.536 = 512 = 256 = 64 = 32 = 8 = 1 The gallon of the former wine measure and of the present Apo- thecaries' measure contains 58.443 Troy grains weight of distilled water, or 231 cubic inches, the ratio being nearly as 6 to 5, or as 1 to 0.8331. Apothecaries' Measure. Gallon = 8 Pints. Pint =16 Ounces. Ounce = 8 Drachms. Drachm = 60 Drops, or Minims, or, Drachms. Minims. Grains Troy. Cub. Inch. = 1024 = 61440 = 58463. =231 = 128 = 7680 = 7292.3 = 28.8 = 8 = 480 = 455.6 = 1.8 1 = 60 = 56.9 = 0.2 French Decimal Measure of Capacity, Litre = 61.028 British cubic inches, or 2.113 Apothecaries' pint, or 1.7608 Imperial pint, or 31.104 Troy ounces of water. Millilitre == .0610 IMPERIAL MEASURE. Pints. Quarts. Gallons. Pecks. Bushels. 1.7608= 17.608=8.804=2.201= 1.100 Hecatolit re = 6102.8000= 176.08=88.04=22.01 = 11.005 Kilolitre = 61028.0000=1760.8=880.4=220.1 = 110.05=27.51 Myrialit re =6 10280.0000= 17608 =8804 =2201 =1100.5 =275.1 * 1 1 1 Gallon. Pints. Ounces. 1 = 8 = 128 1 = 16 1 Centilitre = .6102 Decilitre = 6.1028 Litre = 61.0280= Decalitre = 610.2800= WEIGHTS AND MEASURES. 499 TABLE showing the Weight in Grains of various Measures of different Fluids. Sp. gf . lPint. I Ounce; 1 Drachm. 1 Minim. Distilled Water . . 1000 7305 45,6.5 57 •9 Sulphuric Ether . . 720 5259 328.6 41.07 .68 796 5814 363.4 45.0 .78 Solution of Ammonia 926 6825 425 53.2 0.84 Muriatic Acid . . . 1280 9450 590.6 73.8 1.23 Nitric Acid .... 1500 10957 654 85.5 1.35 Sulphuric Acid . . 1845 13477 840 105. 1.65 TABLES SHOWING THE CORRESPONDENCE BE- TWEEN FAHRENHEIT'S, REAUMUR'S, AND THE CENTIGRADE THERMOMETERS. The space between the boiling and freezing points of water is divided into 180 parts or degrees in Fahrenheit's Thermometer. 100 80 Therefore in the Centigrade. in Reaumur's. Cent. Reaum. 100 = 80 Fahrenh. 180 degrees 1 — 5 4 j. . — s — y 1* — 1 — 4 91 — 11 — I In Fahrenheit's Thermometer the graduation begins at 32 de- grees below the freezing point of water. The Centigrade and Reaumur's commence at this point. Accordingly, 1 . To reduce Centigrade degrees to Fahrenheit's, multiply by 9, divide by 5, and add 32. Thus, 360 40 C. X 9=360 ; —-—=72 ; 72 + 32= 104 Fahrenh. o Formula ~ 9 + 32=F. o 2. To reduce Fahrenheit's to Centigrades, subtract 32, multiply by 5, and divide by 9. Thus, 104 Fah.— 32=72 ; 72x5=360 ; -^-=40 Centigrade. . F.— 32x5 Formula — — ^ =C. 500 WEIGHTS AND MEASURES. i 8 A =33 E. S. To reduce Reaumur's to Fahrenheit's, multiply by 9, divide by 4, and add 32. Thus, 288 R. 32 x 9=288 ; — —=72 ; 72 + 32= 104 Fah. 4 ft vQ Formula^— +32=F. 4 ' 4. To reduce Fahrenheit's to Reaumur's, subtract 32 ; multiply by 4 ; and divide by 9. Thus, Fah. 104—32=72; 72x4=S Formula — - — ^ =R. 9 5. To reduce Reaumur's to the Centigrade, multiply by 5. and divide by 4. Thus, 160 R. 32 x 5=160 ; ——=40 Centigrade. Formula — = C. 4 6. To reduce the Centigrade to Reaumur's, multiply by 4, and divide by 5. Thus, C. 40 x 4= 160 ; J^- = 32 Reaum. 5 Formula -^i = R. 5 TABLE SHOWING THE CORRESPONDENCE BE- TWEEN FAHRENHEIT'S, REAUMUR'S, AND THE CENTIGRADE THERMOMETERS. F. C. R. F. C. R. F. C. R. F. C R. F. C. R. —40 —40 —32 +14—10 —8 + 68 +20 +16 +122 +50 +40 f 176 +80 +64 —31 —35 —28 +23 —5 —4 + 77 +25 +20 +131 +55 +44 +185 +85 +68 —22 —30 — 24 +32 + 86 +30 +24 +140 +60 +48 + 194+90 +72 —13 —25 —20 + 41 +5 +4 + 95 +35 +28 + 149+65 +52 +203 +95+76 — 4—20—16 +50 +10 +8 + 104 +40 +32 + 158 +70+56 +212+100 + 80 + 5—15—12 +59 +15 +12 + 113 +45 +36 +167 +75 +60 &c. It will be observed, that in this table the numbers in Fahren- heit's scale advanced by 9, in the Centigrade by 5, and in Reau- mur's by 4. Wedgewood's pyrometer begins at 1077 Fahrenheit ; and each degree is equal to 130 of Fahrenheit. Therefore, W. X 130. -j-1077=Fah. ; or according to Morveau, who af- firms that the degrees in Wedgewood's pyrometer are estimated too high; W. X62-5, + 517-579= Fah. ; and also Fah. —1077-5- 130= W. ; or according to Morveau, Fah. — 517-579-H32-5=W- Tt is an instrument, however, that is scarcely ever used now, as the indications which it gives cannot be depended upon. 501 TABLE FRIGORIFIC MIXTURES WITHOUT ICE OR SNOW. Mixtures. Quantity of Materials by Weight. Reduction of Temperature. Number of degrees the thermome- ter falls. From + 50 to + 3. 47 Sulphate of soda, .....8 From -f 50 to 0. 50 Diluted nitric acid,* 4 From +50 to — 12. 62 From + 50 to + 4. 46 "Water, 16 From + 50 to +10. 40 From + 50 to — 10. 60 * Composed of equal weights of strong sulphuric acid and water allowed to cool before using it. t Crystallized sulphate of soda, which should be reduced to powder before it is used. $ Prepared by mixing one part of water and two of the strong acid describ- ed in paragraph 136* 502 TABLE FRIGORIFIC MIXTURES WITH ICE OR SNOW. Mixtures, i Quantity of Materials by Weight. Reduction of Temperature. Number of degrees the thermome- ter sinks. From + 32 to— 23. 55 From +[32 to — 30. 62 Snow, 8 From + 22 to— 27. 59 « u 93 ft i; Hi >> c cS a o to — 5,f to — IS. Crystallized muriate of lime,... 3 From + 32 to — 50. 82 Crystallized muriate of lime,... 3 From — 40 to — 73. 33 Diluted sulphuric acid, 10 From— 68 to — 91. 23 * When snow cannot be procured, pounded ice may be substituted for it. + I have seen the temperature of a mixture of common salt and snow fall to -D when a very large quantity of materials were mixed together. INDEX. Acetic acid, adulterations of, weak, . . acetous fermentation, Acid, acetic, arsenic, arsenious, benzoic, boletic, boracic, camphoric, • carbonic, ! chloric, chloriodic, chlorocyanic, chlorocarbonic, j chlorochromic, chromic, citric, cyanic, ellagic, ferrocyanic, fluoboric, fluochromic, fluoric, . • fluosilicic, fulminic, (cyanic,) gallic, hydrochloric. See muriatic, 189 hydrocyanic, . I* 1 * hydriodic, . 204 hydroxanthic, • 172 hyperoxymuriatic (chloric) 187 hyponitrous, hypophosphorous, hyposulphuric, h y posxilp hurous , jgasuric, Page 159 162 161 159 159 314 307 167 170 174 170 116 187 209 158 198 324 324 164 146 169 154 214 324 211 214 146 169 51 101 82 83 170-391 Acid, iodic, . kinic, lithic. See Uric, malic, ... manganesic, • manganeseous, margaric, meconic, mellitic, menispermic, moroxylic, niucic, muriatic, nitric, . nitrous, nitro-muriatic, oleic, oxalic, oxymuriatic (chlorine) perchloric, phosphatic, . phosphoric, phosphorous, prussic, » pyroligneous, pyrotartaric, saccholactic, selenic, succinic, sulphuric, • sulphurous, sulphocyanic, sulphonaphthalic, sulphovinic, tartaric. uric, Acidimetry, Acids, vegetable, table of, page 203 390 401 170 322 321 393 381 170 170 . 170 170 189 53 51 196 393 165 175 189 104 102 102 147 160 . 16* 170 94 169 75 70 156 129 139 162 401-403 486 159 504 INDEX. Page Page Adipocire, 396-7 Aqua regia, . . 64, 195 Adopter, 449 Apparatus, miscellaneous, 443 Air, atmospheric, 64 "VToulfe's, 73 Albumen, 397 Nooth's 118 Alcoates, 136 Arbor Dianae, 351 Alcohol, 130 Areometer, . 493 absolute, 133 Arsenic, 305 ammoniatum, 246 reduction of, 305 Lowitz's table of, 135 protosulphuret (realgar) 315 quantity of in liquors , 134 yellow sulphuret (orpi- Alembic, 449 rnent) 315 Alkalimetry, 486 Arseniate of potassa, . ib. Alkalis, vegetable, 377 A rse Pi° acid, 314 method of preparing, 377 Arsenious acid, 307 Alloys, 363 antidotes to, 316 fusible, 365 method of detecting the Alum, 265 presence of, 307-14 Alumen exsiccatum, 266 solution of, 307 Alumina, 264 Arsenite of potassa, ib. Aluminum, 264 Atmospheric air, 64 Amalgams, 363 discovery of. 65 for electrical machines, 365 properties of, 67 — looking glasses, 365 Azote. See Nitrogen, 37 — gilding silver, copper, or brass, 366 Balance, 455 Amber, acid from, 169 hydrostatic, 489 American hiccory, 376 Barilla, 240 Ammonia, 244 Barium, 258 characters of, . 247 peroxide, 259 muriate, . 249 hydrosulphuret, 260 nitrate, 40, 248 sulphuretj 260 phosphate, 218 Baryta, 258 subcarbonate, 248 carbonate, 260 bicarbonate, 248 muriate, 260 ' carbonate, . 248 nitrate, 259 sulphate, ib. sulphate, 260 water of, 245 tests of, 259 table of the strength of, 246 Basis. See Mordant, 376 Animal substances, ' 396 Benzoic acid, 167 ultimate analysis of, 367, 406 Bicarburet of hydrogen, 129 Antimony, 295 Biliary calculi,' 400 chloride, 305 Biphosphureted hydrogen, 109 crocus of, 297 Bismuth, 319 glass of, 297 hi nitrate, 320 golden sulphurct of, 301 nitrate, 319 muriate, 304 oxide, 319 oxide with phosphate subnitrate, 320 of lime, • 298 tartrate (pearl white,) 320 and potassa, tartrate, 301 Bisulphureted hydrogen, 91 precipitated sulphuret,300 Bisulphuret of carbon, 171 protoxide, 296-7 characters of, 172 sulphate, 299 Blacklead crucibles, 447 native sulphurct, 300 Blast furnace, 144 Aqua. . '. 59 Blow-pipe, 4G0 INDEX. 505 Page Blow-pipe, art of using, . 461 Beraelius' table of its effects, • 468 Dr. Black's blow-pipe, 460 cbarcoal support for, 463 earthen-ware support for, .. . 463 common, . 460 deoxidating, flame of, 463 experiments with^ 466 gas lamp for, . 462 oxidating flame of, 463 oxyhydrogen . 465 • support for, . 465 water pressure, . 464 Dr. Wollaston's, . 460 Boletic acid, . . 170 Borax, ■ . 243 Boracic acid, . . 174 Boron, . . .173 Brass, . . . .364 Brazilwood, -. . 375 Bromine, • ... 209 cyanide of, . 158 Bronze, • • 364 Blue, Prussian, . . 279 Calcium, 250 chloride, 256 phosphuret, 255 Calculi, analysis of, 400 biliary . . 400 cystic oxide, 403 fibrinous, 403 fusible, 403 phosphate of lime, . 402 phosphate of ammonia and magnesia, . 403 oxalate of lime, . 401 urate of ammonia, . 401 uric acid, . . 401 xanthic oxide, . 403 Calomel. See Chloride of Mercury,344 Camphor, artificial, . 395 Camphoric acid, . . . 170 Carbon, . .110 characters of, . 112 bihydruret, . 125 bisulphuret, . 1 71 hydruret (olefiant gas,) 121 perchloride, . . 197 power of absorbing gases, 112 preparation, of, . 110-1 protochloride, . 198 subchloride, . 198 Carbonic acid, . . 116 Page Carbonic acid, characters of, 117 chemical relations of, 118 preparation of, . 116 Carbonic oxide, . . 114 characters of, . 116 modes of preparing, 114 Carmine, . . . 374 Cassius, purple of . 318 Caustic, lunar. See nitrate of sil- ver. Cements, . . . 457 Ceruss, ... . 286 Chalk, . . . .255 Chameleon mineral, . 325 Charcoal, '. . 110 animal, (Ivory black) 111 Chauffer, . . . 8 chimney for, ; 8 pincers for, . 8 black lead crucible, 9 Chemical equivalents, scale of, 408 table of, 422 equivalents, doctrine of, 411 by weight and by vo- lume, . . 442 Chloric acid, . . 187 Chloride of nitrogen, , 195 carbon, . 197-8 lime, • , 256 Chlorine, . 175 characters of, . 178 cyanide of, . 158 experiments with, 181 hydrocarburet of, 197 preparation of, . 176 peroxide of, . 185 protoxide of, (euchlo- rine) . 183 table of its compounds, 176 Chloriodic acid, . . 209 Chlorocarbonic acid, (Phosgene gas) . . 198 Chlorochromic acid, . 324, Chlorocyanic acid, . . 158 Cholesterine, . . 400 Chrome, . . 323 protoxide, . 323 Chrome yellow. See chromate of lead. Chromate of baryta, . 326 lead, . 326 Subchromate of lead, . 326 Chromate of mercury, . 326 potassa, . 325 bichromate of potassa, 325 Chromic acid, . . 324 506 INDEX. Page Cinchona, active principles of, 385 Cinchonia, . . 390 Cinnabar, artificial, - 341 Citric acid, . • 164 Coal gas, . . 123-126 Coating of glass jmd iron vessels, 459 Cobalt, muriate, oxide, Cochineal, Coke, Colouring matter, Colours, adjective, substantive, Copal varnish, Copper, acetate (verdigris) ammoniaco-sulphate bichloride, binacetate, carbonate, experiments with, gilding of, nitrate, permuriate, peroxide, protomuriate, protoxide, silvering of, subacetate, sulphate, sulphuret, tests of, tinned, Corrosive sublimate. See bichlo- ride of mercury, Cream of tartar, Crocus of antimony, Crucibles, black-lead, cast-iron, Hessian, platina, sublimation by, Wedgewood's ware, Cupellation, . 283 Cyanic acid, '. Cyanide of iodine, Cyanogen, . • preparation of, characters of, 327 327 327 374 112 372 376 ib. . 458 287 290 289 291 290, 291 290 Digesting flask, Distillation, with flasks, Dobereiner's lamp, modification of, Dutch gold, Dyeing, Elaine, Electricity, Page 448 53, 449 55 25 27 364 374-6 392 479 method of transmitting through bodies, Electrical discharger, Electrophorous, Emetic, tartar, Ellagic acid, Epsom salts, Ethers, nitric ether, sulphuric ether, Ethiops mineral, 288 Euchlorine, 366 . Eudiometer, 288 291 287 481 481 479 301 169 263 136 140 137 340 183 65 66 480 291 287 366 290 289 290 288 366 348 236 297 447 447 447 447 447 450 447 352 146 158 144 ib. 146 Definite proportions," doctrine of, . . 410-1 Dcrosne, salt of, • 383 Diamond, . . 113 Dr Hope's Dr. Ure's Volta's ; method of detonating gases by 480 Eudiometry, . . . 65-6 Evaporating vessels, . 448 Evaporation of liquids in vacuo, 456 Exhausting syringe, . . 455-6 Fecula. See starch, . 370 Ferment, . . . 132 Fermentation, . . 130 Ferrocyanic acid, . • 154 Fibre, woody . . 371 Fibrine, .... 396 Filtering frame, . . . 451 Filters, .... 450 Fire damp, . . . 125 Fire place, mode of adapting one for chemical experiments, 445 Fixed oils, . . .392 Flasks, . . . • 448 Florence flasks, . . 448 Fluoboric acid, . . . 214 Fluoric acid, . . 211 its action on glass, 213 Fluorine, . . 211 Fluosilicic gas, . . 214 Flux, black . . 234 white . . 234 Freezing mixtures, . 501 water in vacuo, 4.57 Fulminating gold, . 359 INDEX. 507 Page Fulminating mercury, . 343-4 platina, . 36 1 silver, . 354-6 Fulminic acid. See Cyanic acid, 146 Funnels, . . 450 Fustic, . . . 376 Furnace, Dr. Black's . 2, 3 blast • • 444 Avith crucibles, 444 portable . 443 Galena, .... 201 Gallic acid, ... 169 Galvanic battery, . . 482 explanation of me- thod of using, 4S3 experiments with, 484 Gas lute, . . . 458 Gases, mode of finding the speci- fic gravity of, . . 493 Gas-holder, Dr. Hope's, . 453-6 Pepy's, . . 4 Gasometer for hydrogen, . 19 Gelatine, . . 399 Gilding, . 366 Glass, . . . 266-7 of antimony . 297 Glasses for precipitates, . 452 Glauber's salts, . . 239 Gliadine, . . . 371 Glucina, ... 268 Glucinum, • . . 268 Gluten, . . . . 371 Gold, .... '357 ammoniuret (fulminating) 359 chloride, . . . 35S ethereal solution of, . 359 oxide, . . . 358 peroxide, . . . 358 Gold coin, . . 365 Gold powder, . . 366 Dutch gold, . . 364 Golden sulphuret of antimony, 301 Gum, .... 368 Gunpowder, . . . 229 Hydrogen, . . . bi carburet of, chemical relations of, deutoxide of, . mode of ascertaining its purity, preparation of, Hydrosulphuric acid, Hyponitrous acid, Hypophosphorous acid, Hyposulphuric acid, . Hyposulphurous acid, Igasuric acid, Indigo, .... Ink, ..... marking, sympathetic, Iodic acid, Iodide of nitrogen, Iodide of sulphur, Iodine, preparation of, tests of, Iron, acetate, and ammonia, muriate of, carbonate, chloride, ferrocyanate, gallate, muriate, . . nitrate, . . peroxide, protoxide, sulphate, sulphuret, and potassa, tartrate of, tests of, . . tinned, Ittria, Ittrium, . Ivory black, Hepai? sulphuris, . . 231 Hydriodic acid, . . . 204 tests of, • 207 experiments with, 207 Hydrocarburet of chlorine, 197 Hydrochloric acid. See muriatic acid. Hydrocyanic acid, . • 147 action of, on animals, 1 50 tests of, . 153 Kelp, Kermes mineral, Page 16 127 23 35 r 28 17-20 79 51 101 83 . 85 170 375 278 356 327 203 208 209 198 199 202 269 277 280 275 280 279 278 280 273 271 270 274 84 278 272 365 268 268 111 240 301 Labarraque's disinfecting liquid, 242 Lac sulphuris, . 93 Lakes, . . 374 Lamp, safety, Sir H. Davy's, 127 gas, for the blow-pipe, 462 Lead, . . 281 acetate, . 286 subacetate, . 286 carbonate, . 286 508 Lead, deutoxide, (red oxide,) nitrate, . phosphate, peroxide, protoxide, tests of, sugar of, sulphate sulphuret, white (ceruss), Leslie, Prof, his method of freez- ing water - , his method of ascer- taining the specific gravity of powders, 491 Light carbureted hydrogen, 125 Lignin, ... . 371 Litmus, . • 373 Lime, .. . . 251 carbonate, . 255 chloride, . 256 lutes with, . 459 muriate, . 255 nitrate, . • 255 phosphate, . 255 sulphate, . 254 sulphureted hydrosulphu- ret, . 254 Liquor ferri alkalini, . 277 Litharge, . . 284 Lithia, . . . 244 Lithium, ,. . 244 Luna cornea, . 357 Lunar caustic, . 355 Lutes and cements, . 457 chalk lute, . 457 clay and sand lutes, 459 gas lute, . 458 wax lutes, . 458 Willis' lute, . 459 INDE Page X. Page 284 Marking ink, . 356 285 Massicot,- 283 286 Measure, for liquids, ('* 455 284 Measures and weights, . 495 283 Meconic acid, 381 284 - tests of, 382,3 286 Mellitic acid, 170 285 Memispermic, 170 281 Mercurial trough, 71 286 Mercury, • . 328 z- acetate, 343 456-7 peraeetate, 343 Magnesia, 262 bicarbonate, 264 carbonate, 264 sulphate, 263 Magnesium, 262 Malic acid, 170 Manganese, 320 deutoxide, 321 protoxide, 321 peroxide, 321 red oxide, 321 muriate, 323 Manganeseous acid, 321 Manganesic acid, 322 Manganesite of potassa, 322 adulterations of, 331 and ammohia, muriate of, (hydrargyrum preci- pitatum album), 350 bichloride, . 348 from the pernitrate, 348 persulphate, 349 bicyanide, . 144 ■bisulphuret, 340, 341 black sulphuret, 340 carbonate, . 341 percarbonate, 342 characters ■ of when pure, . • 330 chloride, . 344 from the bichloride, 345 sulphate, 346 protonitrate, 347 cyanate, • . 343 ■ distillation of, 331 iodide, •. 350 periodide, . 350 muriate. See chloride, 344 peroxide, . 334 adulterations of, 335 pernitrate, . 337 persulphate, . 338 protonitrate, . 337 protoxide, . 333 protosulphate, . 339 purification of, 331-3 subsulphate, . 339 -sulphuret, • . 340 tests of, . 336-7 Mineral. chameleon, , . 322 Minium. See Deutoxide of lead, 284 Miscellaneous apparatus, 443 Mordant, in dyeing, . 376 Moroxylic acid, . 170 Morphia, . . 378 characters of, 379-81 preparation of, 378-9 sulphate of, . 380 Mucic acid, . . 170 INDEX. 509 Muffles, . . 282 Multiple proportions, law of, 413 Muriatic acia\ . 189 experiments with, 192 preparation of, , 190 table of by Dr. Ure, . 194 tests of, . 194 Naphtha, . . 128 Naphthaline, . . 129 Narcotine, . . 3S3 Nickel, .. . 362 purification of, . 362 oxide, . . 363 peroxide, 363 sulphate, . 362 Nitre, . . 228 Nitric acid, . . 53 adulterations of, . . 62 oxygenated, . . 64 preparation of, . 53 table of by Dr. Thomson, 57 Dr. Ure, 58 tests of, . . 63 Nitric ether, . . 140 preparation of, . 140 spirit of, . 142 Nitric oxide, . . 46 chemical relations of, 48 preparation of, . 46 Nitrogen, . 37 bicarburet, . 144 chloride, . 195 deutoxide, . 46 preparation of, 37-8 protoxide, . 40 Table of its compounds, 40 Nitro-muriatic acid, . 196 Nitrous acid, . . 51 chemical relations of, 52 preparation of, . 51-2 Nitrous oxide, . 40 Effects on the animal eco- nomy, . . 43-4 mode of inhaling, 45 preparation of, . 40-1 Nooth's apparatus,. . 118 Oils, 392 fixed or expressed, 392 of wine, 139 volatile or essential, 394 Olefiant gas, 121 characters of, 124 Opium, active principle of, 378 antidotes to, 384 Orpiment, Osmazome, . Oxalic acid, tests of Oxygen, Page 315 400 165 167 1 from chlorate of potassa, 14 manganese by heat, . 2 sulphuric acid, 6 nitrate of potassa, 12 red oxide of lead, 11 red oxide of mercury, 125 Oxyhydrogen blow-pipe, 465 Oxymuriate of. Mercury. See Chlo- rine, . 175 Parting, Pearl ash, Pearl white, Perchloric acid. Pewter*, 358 233 320 189 365 Opium, detection of, 382-3-4 Phosgene gas. See chlorocarbonic acid. Phosphatic acid, . 104 Phosphorus, . . 94 bichloride, . . 197 characters of, . 98 preparation of, . 94 protochloride, . 197 Phosphoric acid, - . 1 02 characters of, . 104 preparation of, . 103 Phosphorous acid, . 102 Phosphureted hydrogen, 104 preparation of, . 105 properties of, . 107 Pincers, . 447 Pinchbeck, . . . 364 Pipette, . . 451 Platina, . . . 360 chloride, . ^361 fulminating, . 361 oxide, . 360 peroxide,. . 361 sulphate, . 361 Platina spoon, . 463 Plaster of Paris, . . 254 .lute with, 55, 459 Plasters, . S94 Plumber's solder, . 365 Pneumatic trough, . 6 Portable fxirnace, . 444 Potassa, . 224 acetate, . . 235 bicarbonate, . 235 bitartrate, . 236 carbonate, . 233 chlorate, . . 236 5 510 INDEX. Page Potassa, experiments with, 226, 229 ferrocyanate, . 235 fusa, . 225 hydrate, . 226 hydriodate, . 237 nitrate, . 228 sulphate, . 230 with sulphur, 231 tartrate, . 236 tests of, . 228 Potassium, . 216 characters of, . 222 chloride, . 237 experiments with, . 223 iodide, . 237 preparation of, . 217 improved process for the pre- paration of, . 219 sulphuret, . 231 Potato, starch from, . 370 Precipitate glasses, . 452 Precipitates, mode of drying, 35 mode of washing, 451 Proof spirit, . 134 Prussian blue, • 145 Prussic acid, . 147 Pulvis antimonialis, .. 298 Purple of Cassius, . 318 Putty, lute with, t 459 Pyroacetic spirit, . 143 Phosphorous, • 265 Pyroxilic spirit, • 143 Quadro -carbureted hydrogen, 128 Quartation, • 357 Quercitron bark, • 376 Quicksilver, • 328 Quina, • • 385 acetate, . 390 gallate, . 390 oxalate, • 390 preparation of, • 385-6 sulphate, . 386-9 tartrate, . 390 Realgar, Resins, 315 395 Saccholactic acid, . 170 Safety lamp, Sir H. Davy's, 126-7 Scale of equivalents, description of, 408 Sal-ammoniac, . 249 Salt, . . 241 Sand bath, . . 445 Selenium, . 93 3 Selenic acid, Separator, Serosity, Silica, Silicum, Silver, 94 450 399 2C6 266 351 ammoniuret (fulminating) 354 carbonate, . 356 chloride, . 353, 357 cyanate (fulminate) 366 nitrate, . 355 fused, . 355 oxide, . 354 phosphate, . 356 standard, . 365 sulphate, . 356 tests of, . 355 Smalt, , .327 Soap, . 393 Soda, . . 239 biborate, . 243 bicarbonate, . 240 carbonate, . . 240 muriate, . : 241 phosphate, . 240 sulphate, . 239 and potassa, tartrate, 243 Sodium, . • 238 chloride, . 241 Specific gravities, method of tak- ing, . . 489 of gases, . 493 of liquids, . . 492 of powders (Prof. Leslie's mode) • 491 of solids, . . 489 Speculum metal, . 364 Spirit of salt, . 189 of wine, . • 130 proof, . . 134 Starch, . . 370 Stearine, . . 392 Steel, ' .271 Strontia, . . 261 Strontium, . • 261 Strychnia, . 391 Sublimation, . . 449 by crucibles, 450 Succinic acid, . 169 Sugar, . • 369 of lead, . 286 Sulphoeyanic acid, . 156 Sulphonaphthalic acid, 129 Sulphovinic acid, . 139 Sulphur, • 68 INDEX. 511 Sulphur, chloride of, . 197 precipitated, . 92 sublimation of, . 68 Sulphureted hydrogen, . 84 action on the animal eco- nomy, . • 87 chemical relations of, 89 mode of using as a test, 478 tests of, . 9 J Sulphureted hydrosulphurets, 92 Sulphuric acid, . 75 anhydrous, 76 characters of, 79 preparation of, 76 on a small scale, 77 purification of, 82 table of by Dr. Ure, 80 Sulphuric ether, . 137 Sulphurous acid, . 70 chemical relations of, 73 its effects on colours, ib. preparation of by mercury, 71 Sympathetic ink, . 327 Syphon, . . 452 Syringe, exhausting, . 456 Tannin, . . 372 artificial, . 372 Tartar emetic, . 301 antidotes to, 303 experiments with, 302 tests of, . 303 Thermometers, mode of convert- ing degrees of into those of each other, . 499 Tartaric acid, . . 162 Test papers, . 372 Test tubes, . . 477 Page Trough, mercurial, . 71 pneumatic, . 6, 7 Uric acid, . . 401-403 calculus, . 401 Urinary concretions, . 401 Vacuo, evaporation in, . 456 freezing in, . 457 Varnishes, . . 458 copal, . 458 Vegetable acids, . 158 alkalis, . 377 Vegetable substances, . 367 ultimate analysis of, 367 Verdigris, . 290 Vermilion, . . 341 Vinegar. See Acetic acid. Vinous fermentation, . 131 Vitriol, glacial oil of, . 76 Volta's eudiometer, . "* 480 Water, artificial formation of, chemical agency of, distillation of, in glass vessels, power of absorbing gases, Water -pressure blow-pipe, Wax lutes, Weights and measures, White lead, Wine, oil of, Woulfe's apparatus, Xanthic oxide calculus, Xanthogen, mode of forming. 478 Yeast, stands for, 477 Yellow, chrome, Thorina, 268 dyes, Thorinum, ib.. Tin, 316 Zaffre, muriate, 318 Zimome, peroxide, 317 Zinc, protoxide, ib. acetate, tests of, 318 carbonate, Tincal, 243 muriate, Tongs, 447 nitrate, Tube apparatus, 477 oxide, Turmeric, 373 sulphate, Turnsol. See Litmus. Zirconia, Turpeth mineral, 339 Zirconium, 29 29 34 31 32 33 464 458 495 286 139 73 403 172 132 326 376 327 371 292 294 293 294 293 292 293 268 268 FINIS. EDINBURGH : PRINTED BY A. BALEOUR AND CO. NIDDRY STREET. DATE DUE 1 UNIVERSITY PRODUCTS. INC »859 5503 BOSTON COLLEGE 3 9031 021 43881 7