< 
 

WITH COMPLIMENTS OF 
 
 A TEXT -BOOK 
 
 ELEMENTARY CHEMISTRY 
 
 THEORETICAL AND INORGANIC. 
 
 BY GEORGE F. BARKER, M. D. 
 
 PROFESSOR OF PHYSICS IN THE UNIVERSITY OF PENNSYLVANIA. 
 
 Second Editiou.'Rtvlsesfand Efr/tirgbd. 
 
 LOUISVILLE, KY: 
 
 JOHN P. MOKTON AND COMPANY 
 
 PUBLISHERS. 
 
 1891 
 
\ 
 
 /f 
 
 
 
 COPYRIGHT, 1891, BY JOHN P. MORTON & COMPANY. 
 
 Eleclrotyped 
 BY ROBERT ROW ELL, 
 
 LOUISVILLE, KY, 
 
PREFACE TO THE SECOND REVISED EDITION. 
 
 The gratifying success achieved by the first edition of this book 
 seems to make it undesirable, in revising it, to alter materially its gen- 
 eral plan. In this edition, therefore, the framework has been allowed 
 to remain in much the same form as that in which it was originally 
 constructed. Several important changes of detail will be noticed, 
 however, among which we may especially mention the following: In 
 the first place, the wide-reaching generalization of Mendeleeff, known 
 as the periodic law, has been adopted throughout. In the earlier por- 
 tion of the book the law itself has been discussed and illustrated at 
 some length. And in the later portions its classifications -have been 
 made use of in arranging the elements for the purposes of study, and 
 the marvelous predicting power of the law with reference to the 
 properties of the elements has been constantly kept in view. In the 
 second place, the relations of the laws of Thermo-chemistry to the 
 chemical changes in matter, and the importance of these laws in the 
 elucidation of chemical phenomena, have been clearly set forth in the 
 present edition, and the intimate connection between matter-changes 
 and energy-changes in general has been made emphatic. A third 
 change has been made, which is perhaps a little more radical. It 
 is the substitution of the word " mass " for " weight," in the terms 
 " atomic weight " and " molecular weight." The word " mass " in mod- 
 ern physics always means a quantity of matter, precisely as the word 
 " weight " always means a quantity of force. And the use of these 
 terms with these exact meanings has been productive of so much 
 clearer thought in physics as to leave no doubt that a similar advan- 
 tage will accrue to Chemistry from a similar use. True, mass in fact 
 is determined by weighing; but mass is not weight, and the funda- 
 mental idea of mass is utterly unlike that which attaches to weight. 
 Of course it will not be claimed that the term "atomic weight" means 
 the earth's attraction on an atom, since in that case it would be absurd 
 to speak of the atomic weight of hydrogen as having the same value 
 on the fixed stars as on the earth, The fact seems to be that the 
 
 237486 (iii) 
 
IV PBEFACE. 
 
 term "atomic weight" is already tacitly used in the sense of "atomic 
 mass ;" i. <?., as meaning the quantity of matter which goes to make 
 up an atom. Thus for example, Muir says in his Thermo-chemistry : 
 " The maximum atomic weight of an element is the smallest mass, 
 in terms of hydrogen as unity, of that element in a molecule of any 
 compound thereof." But it is precisely this use of the word " weight" 
 which seems unfortunate and which it is one of the purposes of this 
 book to avoid. To use the word ' weight " in the sense of " mass " i.s 
 to introduce a vagueness of statement into the language of science 
 which in its effect must be far more prejudicial to exact expression 
 than can ever be the slight embarrassment which rises from the use 
 of the new terms "atomic mass" and "molecular mass" until chem- 
 ists shall have become accustomed to them. Moreover it will be 
 observed, I think, that in the following pages these terms fall into 
 place very naturally, and thus bring the terminology of chemistry 
 into entire accord with that of the rest of the physical domain. 
 
 Lastly, in the present edition the book has been thoroughly revised 
 and brought up to date; the newer discoveries in physical chemistry, 
 such for example as the liquefaction and solidification of the gases, 
 being recorded from the data of the latest experiments. While there- 
 fore a considerable amount of new matter has been added, the size of 
 the book has not been materially increased. This is important, since 
 in the author's judgment the text-book should contain no more matter 
 than the student may be required to master; leaving to the instructor 
 the task of amplifying, explaining, and illustrating the text. Rep- 
 resenting as this book does one of the modern educational methods 
 which in the hands of the author has been found to produce most 
 satisfactory results, the new edition is offered in the hope that this 
 method may continue to be successful and these results continue to 
 be attained by those of his fellow teachers who are striving for a high 
 standard of excellence in scientific education. 
 
 PHILADELPHIA, January, 1891. 
 
PREFACE TO THE FIRST EDITION. 
 
 Within the past ten years Chemical science has undergone a re- 
 markable revolution. The changes which have so entirely altered 
 the aspect of the science, however, are not, as some seem to suppose, 
 changes merely in the names and formulas of chemical compounds; 
 for in this the science is but returning to principles long ago estab- 
 lished by Berzelius. They are changes which have had their origin 
 in the discovery, first, that each element has a fixed and definite com- 
 bining power or equivalence; and second, that in a chemical com- 
 pound the arrangement of the atoms is of quite as much importance 
 as their kind or number. The division of the elements into groups, 
 according to the law of equivalence, necessitated a revision, and in 
 some cases an alteration, of their atomic weights ; while, in obedience 
 to the second law, molecular formulas were reconstructed so as to 
 express this atomic arrangement. The importance of these laws can 
 not be overestimated. By the former, all the compounds formed by 
 any element may be with certainty predicted; by the latter, all the 
 modes of atomic grouping may be foreseen, and the possible isomers 
 of any substance be pre-determined. Instead, therefore, of being a 
 heterogeneous collection of facts, Chemistry has now become a true 
 science, based upon a sound philosophy. 
 
 The first part of this book is intended to be an elementary treatise 
 upon Theoretical Chemistry. It aims to present the principles of the 
 science as they are held by the best chemists of the day upon a new 
 plan of treatment which the author has found simple and satisfactory 
 in his own teaching. In studying it, it is desirable that the student 
 commit to memory the portions given in large type, while the exam- 
 ples given in small type he may recite in his own language. These, 
 it must be remembered, are to be extended by the teacher until the 
 principles they illustrate are clear to every mind. The questions and 
 exercises printed at the end of each chapter are intended to be sug- 
 gestive rather than exhaustive; these, therefore, should be amplified 
 by the teacher at his discretion. By means of the table on page 19, 
 
vi 
 
 the class should be thoroughly drilled in the rules of naming chem- 
 ical compounds ; and by this table, used in connection with those on 
 pages 16 and 21, a very thorough drill in chemical notation may be 
 secured. 
 
 The second part of the book contains the facts of Inorganic Chem- 
 istry, arranged systematically under appropriate heads. To as great 
 an extent as seemed desirable, theory has been applied to explain the 
 formation and properties of compounds. The unsatisfactory classifi- 
 cation of the elements into metals and metalloids is discarded, and 
 they are arranged electro-chemically, from negative to positive. The 
 problems given in the exercises should be conscientiously worked out 
 by the student. The metric system of weights and measures, and the 
 centigrade scale of thermometric degrees is used throughout the book. 
 Tables in the Appendix show the relation of these measurements to 
 those of our ordinary standards. 
 
 The entire book, it is believed, is a fair representation of the present 
 state of Chemical science. If much appears in it that is novel, much 
 more has been omitted because unsuited to a strictly elementary 
 book. 
 * * * ****** * 
 
 In conclusion, this text-book is offered as a contribution toward 
 making science disciplinary as well as instructive. If it be true that 
 Chemistry already excels in training the powers of perception and of 
 memory, it is unquestionably true that this science is capable of devel- 
 oping the reasoning faculties also. The present attempt to make it 
 available for this purpose, therefore, may fairly ask to be judged, not 
 in the light of its shortcomings alone, but also by the desirability of 
 the end at which it aims. 
 
 NEW HAVEN, October, 1870. 
 
TABLE OF CONTENTS. 
 
 PART FIRST: THEORETICAL CHEMISTRY. 
 
 CHAPTER I. INTRODUCTION. PA(;E 
 
 Section 1. Physical and Chemical Properties of Matter, . 1 
 
 CHAPTER II. ELEMENTAL MOLECULES AND ATOMS. 
 
 Section 1. Molecules in general, 9 
 
 Section 2. Elemental Molecules, . . . . 10 
 Section 3. Properties of Atoms' . . . . . .14 
 
 Section 4. The Periodic Law, 23 
 
 Section 5. Atomic Notation, ....... 27 
 
 CHAPTER III. COMPOUND MOLECULES. 
 
 Section 1. Binary Molecules, 31 
 
 Section 2. Ternary Molecules united by Dyads, ... 39 
 
 Section 3. Ternary Molecules united by Triads, . . 49 
 
 CHAPTER IV. VOLUME-RELATIONS OF MOLECULES. 
 
 Section 1. Relation of Density to Atomic Mass, ... 56 
 
 Section 2. Relation of Gaseous Diffusion to Atomic Mass, 58 
 
 Section 3. Combination by Volume, ..... 60 
 
 CHAPTER V. CHEMICAL REACTIONS, STOICHIOMETRY. 
 
 Section 1. Chemical Equations, 68 
 
 Section 2. Stoichiometrical Calculations, .... 79 
 
 PART SECOND: INORGANIC CHEMISTRY. 
 
 CHAPTER I. HYDROGEN . . . 99 
 
 CHAPTER II. NEGATIVE MONADS. 
 
 Section 1. Chlorine, 107 
 
 Section 2. Bromine, Iodine, and Fluorine, . . . 116 
 
 Section 3. Relations of the Halogen group, .... 123 
 
 (vii) 
 
vin 
 
 CHAPTER III. NEGATIVE DYADS. 
 
 Section 1. Oxygen, 126 
 
 Section 2. Sulphur, 149 
 
 Section 3. Selenium and Tellurium, . . . . . 171 
 
 CHAPTER IV. NEGATIVE TRIADS. 
 
 Section 1. Nitrogen, . .170 
 
 Section 2. Phosphorus, . 200 
 
 Section 3. Arsenic and Antimony, . . . . . .210 
 
 Section 4. Bismuth, . . 218 
 
 Section 5. Relations of the Nitrogen group, . . 221 
 
 CHAPTER V. NEGATIVE TETRADS. 
 
 Section 1. Carbon, . . : 224 
 
 Section 2. Silicon, . 251 
 
 CHAPTER VI. BORON, ALUMINUM. 
 
 Section 1. Boron, ........ 257 
 
 Section 2. Aluminum, 259 
 
 CHAPTER VII. POSITIVE TETRADS. 
 
 Section 1. Tin, 264 
 
 Section 2. Lead, 267 
 
 CHAPTER VIII. THE PLATINUM GROUP. 
 
 Section 1. Platinum, 274 
 
 CHAPTER IX. THE IRON GROUP. 
 
 Sub-group A. Chromium, 278 
 
 Sub-group B. Manganese, 281 
 
 ,. (Section 1. Iron, 284 
 
 ,b-group C. \ Sect . (m 2 N . okcl Rnd Cobalt> . . . 293 
 
 CHAPTER X. COPPER, SILVER, GOLD. 
 
 Section 1. Copper, 299 
 
 Section 2. Silver, 302 
 
 Section 3. Gold, . .305 
 
 CHAPTER XI. GALLIUM, INDIUM, THALLIUM. 
 
 Section 1. Gallium, 308 
 
 Section 2. Indium, 308 
 
 Section 3. Thallium, . 309 
 
TAIiLK OF CONTEXTS. IX 
 
 CHAPTER XII. ZINC, CADMIUM, MERCURY. 
 
 Section 1. Zinc, 311 
 
 Section 2. Cadmium, 314 
 
 Section 3. Mercury, 314 
 
 CHAPTER XIII. POSITIVE DYADS. 
 
 Section 1. Magnesium, ..... 
 
 Section 2. Calcium, ..... 
 
 Section 3. Strontium and Barium, .... 324 
 
 CHAPTER XIV. POSITIVE MONADS. 
 
 Section 1. Lithium, ...... . 327 
 
 Section 2. Ammonium, 328 
 
 Section 3. Sodium, 329 
 
 Section 4. Potassium, 
 
 Section 5. Rubidium and Caesium, ..... 335 
 
 APPENDIX, 339 
 
 INDEX, 348 
 
PART FIRST. 
 
 THEOEETICAL CHEMISTEY. 
 
Part First. 
 THEORETICAL CHEMISTRY. 
 
 CHAPTER FIRST. 
 
 INTRODUCTION. 
 1. PHYSICAL AND CHEMICAL PROPERTIES OF MATTER. 
 
 1. Natural and Physical Science. Science is system- 
 atized knowledge of nature. It is commonly divided into 
 Natural and Physical Science. 
 
 Natural Science considers the external form and the 
 internal arrangement or structure of natural objects. 
 
 Physical Science concerns itself with the matter of 
 which these objects are made up and with the energy-changes 
 which this matter may undergo. 
 
 EXAMPLES. Geology, Mineralogy, Botany, and Zoology, which 
 treat of the form and structure of the earth, of minerals, of plants, 
 and of animals, respectively, are called Natural Sciences. 
 
 Physics and Chemistry, which study the properties of matter 
 itself, whether hard or soft, heavy or light, combustible or non-com- 
 bustible, are called Physical Sciences. 
 
 2. In studying- Matter, Physical Science considers : 
 1st. The divisions of which it is capable. 
 
 2d. The attractions by which the divided particles are 
 held together. 
 
 3d, The motions which these particles may have. 
 
 (1) 
 
2 ^ THEORETIC A i; CHEMISTRY. 
 
 3. Divisions of Matter. Three divisions of matter are 
 recognized in science : masses, molecules, and atoms. 
 
 A Mass of matter is any portion of matter appreciable by 
 the senses. 
 
 A Molecule is the smallest particle of matter into which a 
 body can be divided without losing its identity. 
 
 An Atom is the still smaller particle produced by the 
 division of a molecule. 
 
 EXAMPLES. The sun and the sand-grain are equally masses of 
 matter. The smallest particles of sugar or of salt which can exhibit 
 the properties of these substances, respectively, are molecules of sugar 
 or of salt. The still more minute particles of carbon, of hydrogen, and 
 of oxygen which make up the molecule of sugar, or those of chlorine 
 and of sodium which compose the molecule of salt, are atoms. 
 
 A mass of matter is made up of molecules, and a molecule 
 itself is composed of atoms. 
 
 Mass and Density. The term mass is also used to in- 
 dicate the quantity of matter in a body expressed in grams. 
 Absolute density is the mass of unit volume i. e., the 
 number of grams in one cubic centimeter of a substance. 
 Relative density is the ratio of the mass of unit volume of 
 a given substance to the mass of unit volume of some stand- 
 ard. This, in the case of solids and liquids, is water ; and 
 in the case of gases, is hydrogen. Since one cubic centime- 
 ter of water has the mass of one gram, the absolute density 
 of a solid or liquid is represented by the same number as the 
 relative density. The specific gravity of a gas is referred to 
 air as unity. 
 
 4. Attractions of Matter. The forms of matter-attrac- 
 tion admitted in science are three in number : 
 
 1st. That form of attraction which is exerted between 
 masses of matter, called gravitation. 
 
 2d. That which binds molecules together, called cohe- 
 sion. When the molecules are unlike, it is frequently called 
 adhesion. 
 
PHYSICAL /AT) CHEMICAL CHANGED. 3 
 
 3d. That which takes place between atoms, called chem- 
 ical attraction or chemism. 
 
 EXAMPLES. The planets are held to the sun and the pehble is held 
 to the earth by the attraction of gravitation. The molecules of gold 
 or of salt are held together by cohesive attraction; those in granite 
 or in gunpowder which are unlike are sometimes said to be held to- 
 gether by adhesion. The atoms which make up a molecule of gold or 
 of .salt are united by chemical attraction. The nature of attraction 
 Hself, however, is unknown. 
 
 Like molecules Avhen united by cohesion, form homogene- 
 ous matter ; unlike molecules when thus united, form hete- 
 rogeneous matter. There are as many kinds of molecules as 
 there are kinds of homogeneous matter. 
 
 5. Motions of Matter. Three kinds of motion are 
 recognized in science : 
 
 1st. Mass motion, or visible mechanical motion. 
 
 2d. Molecular motion, or the motion of the molecules 
 within the mass, which is commonly called Heat. 
 
 3d. Atomic motion, or the motion upon which spectrum 
 analysis is assumed to rest. 
 
 6. Province of Physics. Physics is that department 
 of Physical Science which studies the results which flow from 
 the molar and molecular conditions of matter. 
 
 EXAMPLES. Weight, which is a consequence of mass-attraction, 
 and impact, which is a result of muss-motion ; tenacity, hardness, and 
 elasticity, which depend upon cohesion ; and solution, capillarity, and 
 diffusion, which result from adhesion ; and the phenomena of heat, 
 which is a molecular motion, are all objects of Physical study and 
 investigation. 
 
 7. Province of Chemistry. Chemistry, on the other 
 hand, studies matter in its atomic condition. Its province is 
 to account for the differences observed in the various kinds 
 of homogeneous matter, and to investigate the changes in its 
 identity which this matter may undergo. 
 
 8. Physical and Chemical changes. Physical changes 
 in matter are those which take place outside the molecule. 
 
THEOEETICA L CHEMISTR T. 
 
 They do not affect the molecule itself, and therefore do not 
 alter the identity of the matter operated on. 
 
 Chemical changes take place within the molecule. They 
 alter the character of the molecule, and hence cause a change 
 iu the identity of the matter itself. 
 
 EXAMPLES. "Water, which is a liquid, may change to iee, a solid, 
 or become steam, a gas. In all these forms, however, the molecule is 
 identically the same ; these changes are therefore physical. But when 
 water is subjected to the influence of electricity, it undergoes a more 
 radical change ; the water disappears, and in its place appear two gas- 
 eous substances, oxygen and hydrogen, with entirely unlike molecules, 
 and hence with entirely different properties from the water in either 
 of its physical states. Such a change as this is a chemical change. 
 
 Any change in matter which destroys the identity of the 
 substance acted on, is a chemical change. All others are 
 physical changes. 
 
 9. Physical and Chemical Properties. Physical prop- 
 erties are those which bodies possess in virtue of their molar 
 or molecular condition. Chemical properties are those which 
 are a result of the atomic composition of the molecule. 
 
 EXAMPLES. Specific weight, the attraction of the earth's mass for 
 the unit of volume of any body; tenacity, which measures the 
 strength of cohesive attraction; color, a result of the action of the 
 molecules of a body upon light; physical state, depending upon the 
 character of the molecular motion. These are examples of physical 
 properties. 
 
 Combustibility, explosibility, capability of union with and of action 
 upon other bodies, are examples of chemical properties. 
 
 10. Differences in Molecules. Molecules differ from 
 each other because the atoms of which they are composed are 
 different. This difference may be : 
 
 1st. In kind. 
 
 2d. In number. 
 
 3d. In relative position. 
 
 EXAMPLES. A molecule of salt, made up of atoms of chlorine and 
 of sodium, differs from a molecule of water, composed of oxygen and 
 
l>Kn.\Kf). 5 
 
 of hydrogen atoms, because the kind of atoms in each molecule is dif- 
 ferent. A molecule of corrosive sublimate and one of calomel arc very 
 distinct bodies, though both are composed of atoms of mercury and 
 of chlorine; the former containing only half as many mercury atoms 
 as the latter to the same quantity of chlorine; the difference in this 
 case being due to the number of the component atoms. Methyl ether 
 and ethyl alcohol, substances obviously different, contain in their 
 molecules, not only carbon, oxygen and hydrogen atoms, but pre- 
 cisely the same number of each; the differences in these substances, 
 therefore, can be due only to a difference in the relative position of 
 these atoms in the molecule of each substance. 
 
 11. Chemistry Defined. Chemistry is that branch 
 of Physical Science which treats of the atomic compo- 
 sition of bodies, and of those changes in matter -which 
 result from an alteration in the kind, the number, or 
 the relative position of the atoms which compose the 
 molecule. 
 
 TABULAR RECAPITULATION. 
 
 Sciences. Divisions. Attractions. Motions. 
 
 [Masses Gravitation Kinetic Energy. 
 
 Ph >' sics ( Cohesion 
 
 [ Molecules Heat. 
 
 ( Adhesion 
 
 Chemistry Atoms Chemism Atomic Vibration. 
 
 12. Matter and Energy. Changes in matter neces- 
 sarily involve changes in the energy with which the matter 
 is associated. Hence, although in general the consideration 
 of energy-transformations belongs to Physics, yet, since purely 
 chemical changes, such as combustion and the like, involve 
 these transformations, it is evident that any study of chem- 
 ical phenomena which leaves them out of the account would 
 be incomplete. The most important energy-relations,Mii the 
 chemical sense, are those which involve the absorption and 
 the evolution of heat, and which constitute, therefore,, the 
 department of Thcrmo-chemistry. 
 
6 THEORETICAL CHEMISTRY. 
 
 EXAMPLES. "When carbon burns, the amount of heat set free is 
 perfectly definite. Calling the quantity of heat required to raise the 
 temperature of one gram of water from to 1 a unit of heat, we 
 find that one gram of carbon in burning produces 8080 units of heat. 
 Conversely, to separate one gram of carbon from its combuslion-prod- 
 uct, requires the absorption of 8080 heat-units. Again, if one gram 
 of zinc be dissolved in sulphuric acid, 1670 units of heat are set free. 
 But if the solution take place in a voltaic cell, the evolved energy 
 takes the form of an electric current ; 2973 coulombs being set free 
 for each grain of zinc dissolved. 
 
 -ffither-energy. But besides the energy resident in mat- 
 ter proper, the aether itself is a store-house of energy. Light 
 is aether-vibration ; electric attraction and repulsion are forms 
 of aether-stress ; electric currents are due to aether-flow, and 
 magnetism is aether vortex-motion. 
 
 13. Physical States of Matter. According to the tem- 
 perature, matter exists in one or another of three distinct 
 physical states, called, respectively, the solid, the liquid, and 
 the gaseous states. There is good reason to believe that at a 
 sufficiently high temperature all substances would be gaseous; 
 and at a sufficiently low temperature, all would be solid. 
 The point of temperature at which a solid becomes a liquid is 
 called its melting- point ; and that point at which, under the 
 pressure of the atmosphere, a liquid becomes a gas or vapor 
 is called its boiling- point. The number of units of heat 
 required to convert unit mass of a solid into a liquid is 
 called its heat of liquefaction ; and the number required to 
 convert unit mass of a liquid into gas or vapor, its heat of 
 vaporization. The fraction of a unit of heat required to 
 raise the temperature of unit mass of any substance from 
 to 1 is called its specific heat. 
 
 EXAMPLES. Water cooled to becomes ice, and heated to 100 
 is converted into steam ; hence, is said to be the melting point of 
 ice, and 100 the boiling point of water. When one gram of ice is 
 melted, 80 units of heat are absorbed in the process; and, conversely, 
 when one gram of water is frozen, 80 heat-units are set free. When 
 
CRITICAL TEMPERATURE AND PRESSURE. ( 
 
 one gram of water at 100 is converted into steam at 100, heat corre- 
 sponding to 536 units must be supplied to it; and when the one gram 
 of steam is again condensed, the 536 heat-units are again set free. 
 One unit of heat will raise the temperature of thirty units of mass of 
 mercury i. e., thirty grams from to 1. Hence, it will require 
 one thirtieth of a heat-unit to raise one gram from to 1. One 
 thirtieth, or 0-033, therefore, is the specific heat of mercury. 
 
 14. Critical Temperature and Pressure. Physics 
 teaches us that at the boiling point the pressure of a vapor 
 exactly balances the pressure on its liquid ; and hence, that 
 the boiling point is higher as this pressure is greater. By 
 Boyle's law, the density of a vapor subjected to pressure 
 steadily increases, and ultimately becomes equal to that of 
 its liquid. Now, Andrews has shown, on the other hand, 
 that no amount of pressure will liquefy a gas unless the tem- 
 perature at the same time is below a fixed point, which is 
 called the critical temperature. The critical temperature 
 is, therefore, the lowest temperature which permits the vapor 
 to acquire the density of the liquid without condensation. 
 The pressure at which this takes place, the temperature 
 being the critical temperature, is called the critical press- 
 ure. It is the pressure required to liquefy a gas at the crit- 
 ical temperature. At the critical point the gaseous and 
 liquid states are indistinguishable from each other. Andrews 
 concludes that the one passes by insensible gradations- into 
 the other, and is continuous with it. 
 
 EXAMPLES. The boiling point of water is taken at 100, because 
 at this temperature its vapor-pressure is 760 millimeters, the atmos- 
 pheric pressure. If, however, the pressure on the liquid he increased 
 to ten atmospheres, the boiling point will rise to 205. At a pressure 
 of 195-5 atmospheres, at 370, water vapor and liquid water have the 
 same density. This pressure and this temperature are, therefore, the 
 critical pressure and temperature for water. The critical temperature 
 and pressure for ammonia are 130 and 115 atmospheres; for acety- 
 lene, 37 and 68 atmospheres; for ethylene, 10-1 and 51 atmospheres; 
 for marsh-gas, 81-8 and 54-9 atmospheres; for oxygen, 118 and 
 50 atmospheres. 
 
THEORETICAL CHEMISTRY. 
 
 EXERCISES. 
 
 1. What is science? 
 
 2. How is natural distinguished from physical science? 
 
 3. Under which head would astronomy be classed? 
 
 4. Is physiology a natural or a physical science? 
 
 5. What are the divisions of matter? 
 
 6. Define a molecule of water 
 
 7. What is meant by the mass of a body? What is relative 
 density? 
 
 8. Define gravitation, cohesion, chemism. 
 
 9. What is the difference between homogeneous and heterogene- 
 ous matter? 
 
 10. Define mechanical motion, heat. 
 
 11. Are the atoms of bodies in motion? 
 
 12. What are the objects of physical study? Illustrate. 
 
 13. What is the province of chemistry? 
 
 14. Is the explosion of gunpowder a physical or a chemical change? 
 
 15. How are physical properties distinguished from chemical? 
 
 16. Why is weight a physical property? 
 
 17. Why is combustion a chemical phenomenon? 
 
 18. In what ways may molecules differ from each other? 
 
 19. Why do water and calomel differ from each other? 
 
 20. Give the definition of chemistry. 
 
 21. What phenomena accompany chemical changes? Illustrate 
 
 22. In what three physical states does matter exist? To what are 
 they due? 
 
 23. Define melting point, heat of vaporization, specific heat. 
 
 24. What is the critical temperature of a gas? Illustrate. 
 
CLASSIFICATION OF MOLECULES. 
 
 CHAPTER SECOND. 
 
 ELEMENTAL MOLECULES AND ATOMS. 
 
 1. MOLECULES IN GENERAL. 
 
 15. Chemical Definition of Molecule. A molecule 
 is a group of atoms united by chemism. It is the smallest 
 particle of any substance which exists in a free or imcom- 
 bined state in nature. . 
 
 16. Analysis and Synthesis. The chemist ascertains 
 the composition of molecules by two methods : 
 
 1st. By analysis, which consists in separating the mole- 
 cule into its constituent atoms. 
 
 2d. By synthesis, which consists in putting together the 
 constituent atoms to form the molecule. 
 
 17. Classification of Molecules. Molecules are di- 
 vided into two classes : 
 
 1st. Elemental molecules, in which the atoms are alike. 
 
 2d. Compound molecules, in which the atoms are un- 
 like. 
 
 Matter made up of molecules containing like atoms is 
 called simple or elementary matter ; matter whose mole- 
 cules are made up of dissimilar atoms is called compound 
 matter. 
 
 EXAMPLES. A mass of iron, of charcoal, or of sulphur, is formed 
 of molecules whose atoms are alike; these substances, therefore, are 
 examples of simple or elementary matter. The molecules which com- 
 pose a mass of glass, of marble, or of water, are made up of dissimilar 
 atoms; these substances are examples of compound matter. To the 
 latter class by far the larger number of substances belong. 
 
10 THEORETICAL CHEMISTRY. 
 
 2. ELEMENTAL MOLECULES. 
 
 18. Mode of distinguishing' Elemental from Com- 
 pound Molecules. Elemental molecules may be distin- 
 guished from those which are compound by causing a re- 
 arrangement of the atoms between two similar molecules. 
 Elemental molecules, under this treatment, yield no new 
 kinds of matter ; compound molecules yield elemental mole- 
 cules, which, of course, are different in kind. 
 
 EXAMPLES. Let act and a a bo two molecules, each composed of 
 the similar atoms a; then by re-arrangement a a and aa will be pro- 
 duced, differing not at all from the original molecules. If, however, 
 the molecules be ab and ab, composed of dissimilar atoms, then by 
 re-arrangement aa and bb are produced, both elemental molecules. So, 
 ar. and ac would give aa and cc ; bd and bd, bb and dd. 
 
 From simple matter only simple matter comes ; but from 
 compound matter simple matter is obtained. 
 
 Silver, oxygen, copper, yield in this way only silver, oxygen, cop- 
 per. But salt gives chlorine and sodium, water gives oxygen and 
 hydrogen, blende gives zinc and sulphur by this re-arrangement. 
 
 19. Number of Elemental Molecules. By effecting 
 this re-arrangement with the molecules of all the various 
 kinds of homogeneous matter known, the number of differ- 
 ent elemental molecules has been ascertained. This number 
 is probably about seventy. Moreover, since every distinct 
 elemental molecule is made up of atoms peculiar to itself, it 
 is obvious that the number of different kinds of atoms must 
 be about seventy also. 
 
 This is the number at present known. Should some new molecule 
 of compound matter be examined hereafter, or should some molecules 
 not now supposed compound be proved to be so, others might be 
 added to the list. 
 
 Of these seventy kinds of atoms all molecules, and there- 
 fore all masses of matter, are made up. 
 
ELEMENTAL MOLECULES. 11 
 
 20. Meta-elements. Recent researches have rendered 
 uncertain the criteria hitherto adopted for elementary bodies, 
 and in consequence have rendered doubtful the number of 
 the elements. A study of the absorption-spectra of didym- 
 ium has shown that this substance is capable of resolution 
 into nine separate components ; and yttrium, by proper treat- 
 ment, may be made to yield five or six constituents, each 
 giving a different phosphorescent spectrum. Crookes con- 
 cludes, therefore, that substances like didymium, yttrium, 
 samarium, gadolinium, and mosandrum, for example, are 
 not actual chemical elements, as they have hitherto been 
 assumed to be, but are compounded of certain simpler bodies, 
 which he calls, provisionally, meta-elements. Besides these, 
 decipium, philippium, holmium, thulium, dysprosium, terbi- 
 um, and gnomium are yet classed as doubtful. 
 
 21. Names of Elemental Molecules and Atoms. 
 Both the elemental molecules and their constituent atoms 
 have the same name. In many cases this name is the one by 
 which the simple substance is familiarly known. But in 
 general the name is given by the discoverer, either in allu- 
 sion to some special property of the body or to its origin or 
 association. In a few instances the names are fancifuL 
 
 EXAMPLES. The name gold is applied equally to the molecules 
 which make up the mass and to the atoms which form the molecule. 
 This name, like that of lead, tin, or iron, is the name of the substance 
 in common use. 
 
 Chlorine, a greenish-yellow gas, gets its name from ^/Iwpdf, greenish- 
 yellow. Hydrogen comes from ikfwp, water, and yevvdu, I produce, 
 because it generates water by its combustion. Calcium conies from 
 calx, lime, because it is obtained from that substance. Caesium is 
 from ccesius, sky-blue, because there are two bright blue lines in its 
 spectrum. Cerium, palladium, and uranium are named from the cor- 
 responding planets. And titanium and tantalum from mythological 
 deities. 
 
 (A. list of the simple substances now known, with the derivation of 
 their names and the names of their discoverers, is given in the ap- 
 pendix.) 
 
12 THEORETICAL CHEMISTRY. 
 
 22. Size and Mass of Elemental Molecules. Ac- 
 cording to the law of Avogadro (1811) or Ampere (1814), 
 equal volumes of all substances in the gaseous state contain 
 the same number of molecules. From which it follows : 
 
 1st. That the molecules of all substances, when in the 
 gaseous state are of the same size. 
 
 2d. That the mass of any molecule, compared with that 
 of hydrogen, is proportional to the mass of any given vol- 
 ume also compared with the same volume of hydrogen. 
 
 EXAMPLES. If one liter of oxygen the mass of which is 16 times 
 as great as that of a liter of hydrogen contains the same number of 
 molecules, then it is obvious that the mass of each molecule of oxygen 
 must be 16 times the mass of a molecule of hydrogen. If the relative 
 density of nitrogen be 14, the mass of a molecule of nitrogen must 
 be 14 times that of a molecule of hydrogen. 
 
 23. Number of Atoms in the Hydrogen Molecule. 
 
 Assuming that one volume of hydrogen contains 1000 mole- 
 cules, then by Avogadro's law, one volume of chlorine will 
 contain 1000 molecules also. If these volumes be mixed 
 together and exposed to sunlight, they combine to form two 
 volumes of a new substance- hydrochloric acid gas which 
 two volumes, of course, by the same law, will contain 2000 
 molecules. Upon analysis, each molecule of hydrochloric 
 acid gas is found to consist of two atoms, one of hydrogen, 
 the other of chlorine. The 2000 molecules, therefore, will 
 contain 2000 hydrogen-atoms and 2000 chlorine-atoms ; but 
 the 2000 hydrogen-atoms came from the 1000 molecules in 
 the original volume, and the 2000 chlorine-atoms came from 
 the 1000 chlorine molecules. Each molecule of hydrogen 
 must, therefore, have furnished two hydrogen-atoms ; and 
 each molecule of chlorine, two chlorine-atoms. Hence, a 
 molecule of hydrogen is made up of two atoms. 
 
 24. Molecular Masses. If the mass of the hydrogen 
 atom be taken as 1, then, since its molecule contains two 
 atoms, its molecular mass will be 2. The molecular mass of 
 
KLEM ENTA L MOL EC VL ES. 
 
 13 
 
 any other substance may be obtained by multiplying its 
 relative density in the state of gas, by the molecular mass 
 of hydrogen. 
 
 EXAMPLES. The relative density of nitrogen gas, for example, is 
 14; that is, a given volume of it say one liter has 14 times the mass 
 of one liter of hydrogen. Its moleeule must, therefore, have 14 times 
 the mass; and si/ice the molecular mass of hydrogen is 2, the molecu- 
 lar mass of nitrogen is 14x2; that is, 28. Again, the relative den- 
 sity of phosphorus vapor is 62; its molecular mass is 62x2, or 124. 
 
 25. Number of Atoms in Elemental Molecules. 
 
 The number of atoms in any elemental molecule is obtained 
 by dividing the molecular mass by the atomic mass. 
 
 EXAMPLES. The molecular mass of nitrogen being 28, and its 
 atomic mass obtained by a method to be described hereafter 14, the 
 number of atoms in its molecule is 28 14, or 2. The molecular mass 
 of phosphorus being 124, and its atomic mass 31, its molecule must 
 contain four atoms. 
 
 2G. Atomicity of Elemental Molecules. The atom- 
 icity of a molecule is the number of atoms which it contains. 
 Molecules are mon-atomic, di-atomic, tri-atomic, tetr-atomic, 
 or hex-atomic, according as they contain one, two, three, four, 
 or six atoms. Most elemental molecules are di-atomic. 
 
 (Many simple substances, not being volatile, can not be weighed in 
 the gaseous state. They are usually classed as di-atomic, however, 
 their di-atomicity being assumed.) 
 
 Those elemental molecules whose atomicity has been exper- 
 imentally determined, are given in the following table : 
 
 Kfon-dtomic. 
 
 Di-atomic, 
 
 Tri-atomic. 
 
 Teir-atomic. Hex-atomic. 
 
 Mercury 
 
 Hydrogen 
 
 Oxygen 
 
 Phosphorus Sulphur 
 
 Cadmium 
 
 Oxygen 
 
 (as ozone) 
 
 Arsenic (about 550) 
 
 Zinc 
 
 Fluorme 
 
 Selenium 
 
 
 Barium (?) 
 
 Chlorine 
 
 (below 800) 
 
 
 Iodine 
 
 Bromine 
 
 
 
 (at ir>00 ) 
 
 Iodine 
 
 
 
 Bromine 
 
 (below 1000) 
 
 
 
 (at 1800 ') 
 
 Nitrogen 
 
 
 
 
 Sulphur 
 
 
 
 
 (above 800') 
 
 
 
 
 Selenium 
 
 
 
 
 (above lilixn 
 
 
 
 
 Tellurium 
 
 k 
 
 
14 THEORETICAL CHEMISTRY. 
 
 Since all molecules are of the same size, molecular atomic- 
 ity may be thus represented : 
 
 000 
 
 3. PROPERTIES OF ATOMS. 
 
 27. Definition of Atom. An atom is the smallest par- 
 ticle of simple matter which enters into the composition of a 
 molecule. 
 
 28. Classification of Atoms. Atoms differ from each 
 other : 
 
 1st. In mass. 
 
 2d. In the quality of their combining power. 
 
 3d. In the quantity of their combining power. 
 
 29. Atomic Mass. The relative mass of any atom re- 
 ferred to that of the atom of hydrogen as unity is its atomic 
 mass. It is the smallest mass of any simple substance which 
 actually takes part in the formation of any chemical com- 
 pound. 
 
 30. Method of fixing- the Atomic Mass. In order to 
 fix an atomic mass we must know : 
 
 1st. The relative mass of the substance which combines 
 with one unit of mass, i. e., one atom of hydrogen. 
 
 2d. The molecular mass of the hydrogen compound. 
 
 I. Analysis of the compound which any element forms with 
 hydrogen will give the absolute mass of each constituent in 
 any given quantity say 100 grams. The mass of the body 
 which unites with unit mass of hydrogen may then be ob- 
 tained by a simple proportion. 
 
 EXAMPLES. Analysis shows that hydrochloric acid gas the hy- 
 drogen compound of chlorine contains, in 100 grams, 97-26 grams of 
 chlorine and 2-74 grams of hydrogen. By the proportion 2-74 : 97-26 
 : : 1 : 35-5, it is ascertained that in this compound the quantity of 
 
PROPERTIES OF ATOMS. 15 
 
 chlorine which combines with unit mass i. e., one atom of hydrogen 
 has a mass 35-5 times as great. 
 
 Again, the analysis of water shows it to be composed of 88'89 per 
 cent of oxygen and 11-11 per cent of hydrogen; whence 11-11 : 88-8'J 
 : : 1 : 8. Eight parts of oxygen unite with one part of hydrogen. 
 
 So ammonia gas contains in 100 parts, 82-35 parts of nitrogen and 
 17-65 parts of hydrogen ; or 17-65 : 82-35 : : 1 : 4-7. Hence, 4-7 parts 
 of nitrogen combine with 1 part of hydrogen. 
 
 Now, if in a molecule of hydrochloric acid, water, or ammonia 
 there is but one atom of hydrogen, then 35-5, 8, and 4-7, being the small- 
 est musses of chlorine, oxygen, and nitrogen which combine, will be 
 the atomic masses of these bodies respectively. 
 
 II. The molecular mass of any substance is the sum of 
 the masses of its constituent atoms. The combining masses 
 obtained by analysis, when added together, therefore, must 
 give either the molecular mass or some number of which the 
 molecular mass is a multiple. In this way the number of 
 hydrogen atoms in the compound may be determined ; and 
 the mass of the other constituent which is united with these 
 hydrogen atoms is its atomic mass. 
 
 EXAMPLES. The relative density of hydrochloric acid gas, of 
 steam, and of ammonia gas, respectively, is 18-25, 9, and 8-5; their 
 molecular masses, therefore, are 36-5, 18, and 17. The sum of the 
 combining masses of hydrogen and chlorine, obtained by analysis 
 (35-5-f- 1), is 36-5. But this is the molecular mass of hydrochloric acid 
 gas. Hence one molecule of this gas contains one atom of chlorine 
 and one of hydrogen, and the atomic mass of chlorine is 35-5. 
 
 Again, the sum of the combining masses of oxygen and hydrogen 
 (8-(-l) is 9. But 9 is one half the molecular mass of water; hence, a 
 molecule of water contains twice as much of each constituent i. e., 
 2 parts of hydrogen and 16 of oxygen. 16 is, therefore, the atomic 
 mass of oxygen. 
 
 So, if the combining masses of nitrogen and hydrogen be added 
 together, the sum is (4-7-f 1 ) 5-7. But 5-7 is only one third the molec- 
 ular mass of ammonia, which is 17. Ammonia, therefore, contains 
 three times as much hydrogen and nitrogen in one molecule as the 
 smallest value given by analysis. It must contain, therefore, 3 parts 
 of hydrogen and 14 (4-7X3) parts of nitrogen; and the atomic mass 
 of nitrogen is fixed at 14. 
 
16 
 
 THEORETICAL CHEMISTRY. 
 
 ELEMENTAL SYMBOLS AND ATOMIC MASSES. 
 
 
 Symbol. 
 
 At. mass. 
 
 Symbol. 
 
 At. mass. 
 
 Hydrogen 
 
 H 
 
 1 
 
 Chromium Cr 
 
 52-45 
 
 Fluorine 
 Chlorine 
 
 F 
 01 
 
 19-06 
 3537 
 
 Molybdenum Mo 
 Tungsten ( Wolfram)V? 
 Uranium U 
 
 95-9 
 183-6 
 2398 
 
 Bromine 
 
 Br 
 
 79-76 
 
 
 
 Iodine 
 
 I 
 
 126-54 
 
 Osmium Os 
 
 191-0 
 
 
 
 
 Iridiiim Ir 
 
 1925 
 
 Oxygen 
 
 
 
 15-96 
 
 Platinum Pt 
 
 194-3 
 
 Sulphur 
 
 s 
 
 31-98 
 
 
 
 Selenium 
 
 Se 
 
 78-87 
 
 Ruthenium Ru 
 
 103-5 
 
 Tellurium 
 
 Te 
 
 125-00 
 
 Rhodium Ro 
 
 1041 
 
 
 
 
 Palladium Pd 
 
 1062 
 
 Nitrogen 
 
 N 
 
 14-01 
 
 
 
 Phosphorus 
 
 P 
 
 3096 
 
 Iron (Fcrrum) Fe 
 
 55-88 
 
 Arsenic 
 
 As 
 
 71-9 
 
 Nickel Ni 
 
 58-50 
 
 Antimony (Stibium)Sb 
 
 119-6 
 
 Cobalt Co 
 
 58-74 
 
 Bismuth 
 
 Bi 
 
 207-3 
 
 
 
 
 
 
 Manganese Mn 
 
 54-8 
 
 Carbon 
 
 C 
 
 11-97 
 
 Gallium Ga 
 
 69-9 
 
 'Silicon 
 
 Si 
 
 280 
 
 Indium In 
 
 113-4 
 
 Titanium 
 
 Ti 
 
 48-0 
 
 Thallium Tl 
 
 203-7 
 
 Zirconium 
 
 Zr 
 
 90-4 
 
 
 
 Cerium 
 
 Ce 
 
 141-2 
 
 Copper (Cuprum) Cu 
 
 63-4 
 
 Thorium 
 
 Th 
 
 232-4 
 
 Silver (Argention) Ag 
 
 107-G6 
 
 Boron 
 
 B 
 
 10-95 
 
 Gold (Aurunt) An 
 
 196-7 
 
 Aluminum 
 
 Al 
 
 27-04 
 
 Zinc Zn 
 
 64-9 
 
 Scandium 
 
 Sc 
 
 44-04 
 
 Cadmium Cd 
 
 111-7 
 
 Yttrium 
 
 Y 
 
 89-6 
 
 Mercury (Hydrar- 
 
 
 Lanthanum 
 
 La 
 
 138-5 
 
 gyrum} Hg 
 
 199-8 
 
 Ytterbium 
 
 Yb 
 
 172-6 
 
 Beryllium Be 
 
 9-08 
 
 Vanadium 
 
 V 
 
 51-2 
 
 Magnesium Mg 
 
 23-94 
 
 Columbian! 
 
 Ob 
 
 93-7 
 
 Calcium Ca 
 
 3991 
 
 Didymium 
 Tantalum 
 
 Di 
 Ta 
 
 142-1 
 182-0 
 
 Strontium Sr 
 Barium Ba 
 
 87-3 
 136-9 
 
 
 
 
 Erbium E 
 
 166-0 
 
 Germanium 
 
 Ge 
 
 7332 
 
 Lithium Li 
 
 7-01 
 
 Tin (Stannum) 
 Lead (Plumbum) 
 
 Sn 
 Pb 
 
 1178 
 206-4 
 
 Sodium (Natrium) Na 
 Potassium ( Kalium] K 
 
 23-0 
 
 39-03 
 
 
 
 
 Rubidium Rb 
 
 852 
 
 
 
 
 Caesium Cs 
 
 132-7 
 
ATOMIC MASS. 17 
 
 31. Indirect Methods of Fixing' Atomic Masses. 
 
 In some cases elements do not unite directly with hydrogen. 
 The comparison with hydrogen is then made by means of a 
 middle term, generally chlorine. 
 
 EXAMPLES. No hydrogen compound of silver is known. But sil- 
 ver combines with chlorine to form the well-known ore, horn-silver. 
 On analysis, this horn-silver yields 75-2G per cent of silver and 24-74 
 per cent of chlorine. As 35 5 parts of chlorine combine with one of 
 hydrogen, the quantity of silver which combines with 85-5 parts of 
 chlorine is its atomic mass, 24-74 : 75-26 : : 35-5 : 108, the atomic mass 
 of silver. 
 
 32. Atomic Heat. Dulong and Petit (1819) pointed 
 out the fact that the product of the specific heat by the 
 atomic mass is constant for nearly all the elements ; or, what 
 is the same thing, the specific heat of an element is inversely 
 proportional to its atomic mass. This constant product is 
 called the atomic heat ; and, since it has the same value for 
 all the elements, it follows that the specific heat of all atoms 
 is the same. Since the average value of this product is 6*4, 
 it is evident that the atomic mass of an element may be ap- 
 proximately obtained by dividing 6'4 by the specific heat of 
 the element. 
 
 (The exact atomic masses of the best-known elements are 
 given on the opposite page.) 
 
 33. Quality of Atomic Combining' Power. Atoms 
 are divided into two classes, according to the quality of their 
 combining power. These are : 
 
 1st. Positive atoms, or those which are attracted to the 
 negative electrode in electrolysis, and whose hydroxides are 
 bases. 
 
 2d. Negative atoms, or those which go to the positive 
 electrode, and whose hydroxides are acids. 
 
 EXAMPLES. Salt, under the influence of electricity, is decomposed 
 into chlorine and sodium. The chlorine atoms collect at the positive 
 electrode, and are therefore called negative. The sodium atoms are 
 
18 THEORETICAL CHEMISTRY. 
 
 found at the negative electrode, and are hence called jyositive. Again, 
 all the hydroxides of chlorine are acids, while the hydroxides of so- 
 dium and potassium substances like chlorine in all other chemical 
 characters are entirely different bodies, called bases. 
 
 In the table on the next page the more common elements 
 are arranged according to their electro-chemical characters, 
 each atom being positive to any atom which is placed above 
 it, and negative to any one given below it. These distinc- 
 tions, although entirely relative, are yet important, since 
 upon them rest not only the. principles of chemical nomen- 
 clature and notation, but also, as seems probable, the nature 
 of chemical attraction itself. 
 
 34. Quantity of Atomic Combining- Power. If the 
 combining power of the atom of hydrogen be taken as 1, 
 the combining power of other atoms will be 1, 2, 3, 4, 5, 6 
 or 7. That is, some atoms have a combining power equal to 
 that of hydrogen and can unite with one atom of it. Other 
 atoms have a higher combining power and can unite with 2, 
 3, 4, 5, 6 or 7 hydrogen atoms or their equivalents. Quan- 
 tity of combining power should not, however, be confounded 
 with intensity of combining power. 
 
 EXAMPLES. Atoms combine with other atoms in virtue of their 
 chemism, an attraction mutually satisfied by the union. Taking 
 the chemism of an atom of hydrogen as the unit, any other atom whose 
 chemism is completely satisfied by uniting with the hydrogen-atom, 
 is its equal in the quantity of its combining power. Other atoms 
 there are, whose chemism requires for saturation, two, three, four, five, 
 six, or seven hydrogen-atoms; hence the quantity of their combining 
 power which is the same for all other similar atoms is said to be 
 one, two, three, four, five, six, seven. 
 
 A chlorine-atom is completely satisfied with one atom of hydrogen ; 
 but an oxygen-atom requires two, a nitrogen-atom, three, a carbon- 
 atom, four, and so on. This is entirely consistent with the fact that 
 the intensity of the attraction between hydrogen and chlorine atoms 
 is greater than that which either hydrogen or chlorine atoms have for 
 each other. 
 
ELECriiO-CHKMICAL SERIES. 19 
 
 Negative End Oxygen. 
 Sulphur. 
 Nitrogen. 
 Fluorine. 
 Chlorine. 
 Bromine. 
 Iodine. 
 Selenium. 
 Phosphorus. 
 Arsenic. 
 Chromium. 
 Vanadium. 
 Molybdenum. 
 Tungsten. 
 Boron. 
 Carbon. 
 Antimony. 
 Tellurium. 
 Tiintalnm. 
 Columbium. 
 Titanium. 
 Silicon. 
 Tin. 
 
 Hydrogen. 
 Gold. 
 Osmium. 
 Iridium. 
 Platinum. 
 Rhodium. 
 Ruthenium. 
 Palladium. 
 Mercury. 
 Silver. 
 Copper. 
 Uranium. 
 Bismuth. 
 Gallium. 
 Indium. 
 Germanium. 
 Lead. - 
 Cadmium. 
 Thallium. 
 Cobalt. 
 Nickel. 
 Iron. 
 Zinc. 
 
 Manganese. 
 Lanthanum. 
 Didymium. 
 Cerium. 
 Thorium. 
 Zirconium. 
 Aluminum. 
 Scandium. 
 Erbium. 
 Yttrium. 
 Ytterbium. 
 Beryllium. 
 Magnesium. 
 Calcium. 
 Strontium. 
 Barium. 
 Lithium. 
 Sodium. - 
 Potassium. - 
 
 r, -j . r> j t Rubidium. 
 rositive E,na -j- Caesium. 
 
20 THEOItKTH'AL CIIKMISTRY. 
 
 35. Valence. The valence of an atom in any case is 
 the quantity of its combining power, expressed in hydrogen 
 units. Since the equivalent mass of an atom is that fraction 
 of its mass which is equivalent to one atom of hydrogen, the 
 valence of an atom, which is the ratio of its atomic mass to 
 its equivalent mass, expresses the number of hydrogen-atoms 
 it can combine with or be exchanged for. 
 
 EXAMTLKS. The valence of carbon is four, when one atom requires 
 four atoms of hydrogen to satisfy its chemisin. The valence of phos- 
 phorus is five, when it forms a compound in which one atom combines 
 with five of chlorine. The valence of sulphur is two, when it can 
 replace two atoms of hydrogen. 
 
 36. Classification of Atoms according' to their Va- 
 lence. Atoms are called monads, dyads, triads, tetrads, 
 pentads, hexads, and heptads names derived from the 
 Greek numerals according to their valence. For the adjec- 
 tive terms, the Latin numerals are generally used ; atoms are 
 univalent, bivalent, trivalent, quadrivalent, quinquiva- 
 lent, sexivalent, and septivalent. 
 
 Atoms whose valence is even, are sometimes called arti- 
 ads ; those whose valence is odd, are frequently termed 
 perissads. 
 
 (A table of the valences of atoms is given on the opposite 
 page.) 
 
 37. Variation in Valence. Since one given element 
 may form several compounds with another given element, 
 valence is evidently not invariable. It generally increases 
 or diminishes by two, however ; so that an atom of the same 
 element may in different compounds have a valence of 1, 3, 
 5, or 7, or of 2, 4, or 6. A perissad atom, as a rule, never 
 becomes an artiad atom by such a change, nor does an artiad 
 atom become a perissad. 
 
 EXAMPLES. Iron in green vitriol is a dyad, in pyrite it is a tetrad, 
 and in ferric acid it is a hexad. Chlorine forms a series of compounds 
 with oxygen in which its valence is one, three, five, and seven. 
 
I'AI.KXCK OF ATOMS. 
 
 21 
 
 PKKISSADS. 
 
 A KTIADS. 
 
 Monads : 
 
 Dyad* : 
 
 
 Hydrogen 
 
 Oxygon 
 
 
 Fluorine i, m. 
 
 Sulphur 
 Selenium 
 
 II, IV, VI. 
 11, IV, VI. 
 
 Chlorine ], in, v, vn. 
 
 Tellurium 
 
 11, IV, VI. 
 
 Bromine I, in, v, vn. 
 Iodine I, in, v, vn. 
 
 Calcium 
 
 II, IV. 
 
 
 Strontium 
 
 II, IV. 
 
 Sodium i, in. 
 
 Barium 
 
 II, IV. 
 
 Lithium 
 
 Magnesium 
 
 
 Potassium i, in, v. 
 
 Zinc 
 
 
 Rubidium 
 
 Cadmium 
 
 
 Caesium 
 
 Beryllium 
 
 
 Silver I, in. 
 
 Mercury 
 
 
 Thallium i, 111. 
 
 Copper 
 
 
 Triad* : 
 
 Tetrads : 
 
 
 Nitrogen i, in, v. 
 
 Carbon 
 
 II, IV. 
 
 Phosphorus J, in, v. 
 
 Silicon 
 
 
 Arsenic i, 111, v. 
 
 Germanium 
 
 
 Antimony in, v. 
 
 Titanium 
 
 II, IV. 
 
 Bismuth in, v. 
 
 Tin 
 
 II, IV. 
 
 Boron 
 
 Thorium 
 
 
 Gold i, in. 
 
 Zirconium 
 
 
 Aluminum 
 Gallium 
 
 Platinum 
 Palladium 
 
 II, IV. 
 
 11, IV. 
 
 Indium 
 
 Lead 
 
 II, IV. 
 
 Yttrium 
 
 
 
 Scandium 
 
 Eexads : 
 
 
 Ytterbium 
 
 Molybdenum 
 
 II, IV, VI. 
 
 Cerium 
 
 Tungsten 
 
 IV, VI. 
 
 Lanthanum 
 Didymium 
 Erbium 
 
 Ruthenium 
 Rhodium 
 Iridium 
 
 IT, IV, VI. 
 II, IV, VI. 
 
 ii, iv, vr. 
 
 Pentads : 
 
 Osmium 
 
 II, IV, VI. 
 
 Columbium 
 
 Chromium 
 
 11, IV, VI. 
 
 Tantalum 
 
 Manganese 
 
 II, IV, VI. 
 
 Vanadium in, v. 
 
 Iron 
 Cobalt 
 
 II, IV, VI. 
 11, IV. 
 
 
 Nickel 
 
 II, IV. 
 
 
 Uranium 
 
 11, IV, VI. 
 
22 THEORETICAL CHEMISTRY. 
 
 Moreover, it would appear that variability in valence is 
 dependent not only upon the given atom itself, but also upon 
 the atoms with which it combines. In all hydrogen com- 
 pounds, the valence of the atom which is joined to the hydro- 
 gen is invariable, only a single valence being known in the 
 hydrogen compounds of any given element. When united 
 to chlorine, how r ever, the valence is variable, several chlo- 
 rides being known of the same element. It is, however, in 
 oxygen compounds that valence reaches its greatest variabil- 
 ity, as well as its maximum value. Mendele'eff has noted 
 the fact that when a substance forms compounds with both 
 hydrogen and oxygen, the sum of the equivalents of the 
 hydrogen and the oxygen in the highest compounds is equal 
 to eight. Thus chlorine forms HC1 with hydrogen, and C1 2 O. 
 with oxygen ; carbon gives CH 4 and CO r Since oxygen is 
 bivalent, there is in the oxygen compound of chlorine 7x2 
 or fourteen equivalents of oxygen for two atoms of chlorine ; 
 or seven equivalents for each. In the oxygen compound of 
 carbon, the oxygen has 2x2 or four equivalents. Uniting 
 in each case the oxygen equivalents per atom with the hydro- 
 gen equivalents, we see that in the first case we have seven 
 plus one ; and in the second we have four plus four ; so that 
 in both cases the sum of the equivalents is equal to eight. 
 
 The compounds formed by an atom with one valence are 
 often widely different in properties from those formed by the 
 same element with a different valence. Sometimes the iden- 
 tity of the atom can be established only by the conversion 
 of the one compound into the other. 
 
 EXAMPLES. The compounds of tin in which this metal acts with 
 a valence of two are quite distinct both in physical and chemical 
 properties from the compounds which contain the same metal with 
 a valence of four. Lead as a tetrad forms a dark brown solid with 
 oxygen ; while as a dyad its compound with oxygen is an orange- 
 yellow powder, 
 
THE I'EIUOIUr LAW. 23 
 
 4. THE PERIODIC LAW. 
 
 38. Elemental Grouping's. For many years similarity 
 of properties has been observed between certain elements, 
 which has led to their being grouped together in what are 
 called natural families. Moreover, a gradation in properties 
 was also observed in these groups, which was easily seen to 
 be connected with a successive increase in the atomic mass. 
 
 EXAMPLES. Thus, chlorine, bromine, and iodine have long been 
 classed together as a natural group, having similar properties in gra- 
 dation. Chlorine is a gas, bromine a liquid, and iodine a solid. Chlo- 
 rine, with an atomic mass of 35-37, is the least dense and the most 
 active; while iodine, with an atomic mass of 1*26-54, is the least active 
 and the most dense. Moreover, the atomic mass of bromine, the 
 middle term, 79-76, is very nearly the mean of the atomic masses of 
 chlorine and iodine. In the same way potassium, sodium, and lithium 
 form a natural group, having a similar gradation of properties. But 
 in this case, since these elements are electro-positive, the chemical 
 activity, instead of diminishing, increases with the atomic mass. 
 
 39. Periodicity in Properties of Elements. In 
 
 1869 and 1870, Mendeleeff and Lothar Meyer independently 
 called attention to the fact that if the elements be arranged 
 in the order of their atomic masses, and then be divided into 
 series of sevens, placing the elements of the second series 
 immediately under the corresponding elements of the first, 
 those of the third under those of the second, and so on, it 
 will be found that, calling the elements in each vertical col- 
 umn a group, each of these groups corresponds to a natural 
 family of elements, having common properties, varying in 
 degree throughout the group. Since a phenomenon is called 
 periodic when it recurs at definite intervals while the circum- 
 stances upon which it is conditioned vary continuously, it is 
 evident that the properties of the elements which recur thus 
 definitely as the atomic mass steadily increases must have 
 a periodic dependence upon this atomic mass. Hence the 
 law : The properties of the elements are periodic func- 
 tions of the atomic masses, 
 
24 THEORETICAL CHEMISTRY. 
 
 In the table on the following page, the elements are 
 arranged substantially according to Mendeleeff's classifica- 
 tion, a horizontal row indicating a series, and a vertical 
 one, a group. That these groups constitute natural families 
 and contain closely allied elements appears from the table 
 on page 16, in which this classification has been closely fol- 
 lowed. The elemental properties which are thus periodic 
 include all the properties of the elements so far as known, 
 both physical and chemical. Their hardness, malleability, 
 and ductility ; their density and consequent atomic volume ; 
 their crystalline form ; their fusibility, volatility, and specific 
 heat ; their expansion by heat, their conductivity for heat, 
 and their heat of combination ; their refractive power and 
 the character of their spectra ; their electro-chemical position, 
 their magnetic or diamagnetic character, and their electrical 
 conductivity ; as well as their combining power or their va- 
 lence are all periodic functions of their atomic masses. 
 
 EXAMPLES. Thus the periodicity of density and of atomic volume 
 (which is the quotient of the atomic mass by the density) appears 
 clearly in the third series of elements in the table, as follows : 
 
 Na Mg Al Si P S Cl 
 
 Density, 0-97 1-74 2-56 2-49 2-8 2-04 1-38 
 
 Atomic vol., 23-7 13-8 10-6 11-2 13-5 15-7 25-6 
 
 In the same way, the refraction-equivalent is shown to be periodic. 
 Thus in the second series : 
 
 Li Be B C N O F 
 
 Eefr. equiv_, 3-8 5-7 4-0 5-0 4-1 2-9 1-4? 
 
 And in the fourth series : 
 
 K Ca Sc Ti V Cr Mn 
 
 Kefr. equiv., 8-1 10-4 ? 25-5? 25-3 15-9 12-2 
 
 The periodicity of valence is clearly seen in the first and the 
 seventh series: 
 
 First, Li Be B C N O F 
 
 Seventh, Ag Ca In Sn Sb Te I 
 
 Valence, 1 2-3 4 3 2 1 
 
 Graphic construction, however, is the best method for showing- 
 periodicity. 
 
THE PERIODIC LA W. 
 
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 4O. Prediction of Properties. The strongest evidence 
 of the truth of a law of nature is its power to predict. In 
 the periodicity table certain gaps will be noticed to which no 
 known element belongs. Mendeleeff undertook to predict 
 the properties of some of these undiscovered elements, basing 
 his predictions on the periodic law. He pointed out that, in 
 general, the value of any property of an element is the mean 
 of the values of the same property of the elements on the 
 two sides of it, whether in the same group or in the same 
 series with it. Thus, for example, taking the atomic masses, 
 the densities, and the atomic volumes for selenium, we find: 
 
 Atomic Musses. 
 
 
 S 
 
 
 
 31-98 
 
 
 As 
 
 Se 
 
 Br 
 
 74-9 
 
 78-87 
 
 79-76 
 
 
 Te 
 
 
 
 126-3 
 
 
 Densities. Atomic Volumes. 
 
 
 S 
 
 
 S 
 
 
 
 2-01 
 
 
 15-7 
 
 
 As 
 
 Se 
 
 Br As 
 
 Se 
 
 Br 
 
 5-G7 
 
 4-6 
 
 2-97 13-2 
 
 17-2 
 
 2G-9 
 
 
 Te 
 
 
 Te 
 
 
 
 6-25 
 
 
 20-2 
 
 
 To four elements thus related, Mendeleeff has given the 
 name atomic analogues. At the time of preparing his 
 table gaps existed in it between boron and yttrium, between 
 aluminum and indium, and between silicon and tin ; to which 
 he assigned elements having the provisional names eka-borou, 
 eka-aluminum and eka-silicon, respectively, and the proper- 
 ties of which he minutely predicted. In 1875 Lecoq de 
 Boisbaudran discovered gallium, which proved to have iden- 
 tically the properties predicted for eka-alumiuum. In 1879 
 Nilson discovered scandium, whose properties turned out to 
 be exactly those required by eka-boron. And in 1886 Wiuk- 
 ler discovered germanium, an element having properties 
 identical with those which Mendeleeff had assigned to eka- 
 
ATOMIC XOTATIOX. 27 
 
 silicon. There would seem to be but little question there- 
 fore, in view of this power of prediction, that the periodic 
 law is one of the most fundamental of all the laws of chem- 
 ical science. 
 
 5. ATOMIC NOTATION. 
 
 41. Atomic Symbols. In 1815 Berzelius proposed an 
 abbreviated form of chemical language. In this system each 
 atom has for its symbol the first letter of its Latin name. 
 Where the names of two different atoms begin with the same 
 letter, a second letter, suggestive of the name, is added. 
 
 EXAMPLES. O stands for an atom of oxygen, I for one of iodine, 
 K for one of potassium (kalium), Au for one of gold (aurum), Sn for 
 one of tin (stannum). So, Cl represents an atom of chlorine, C one 
 of carbon, Ca one of calcium, Ce one of cerium, Cd one of cadmium, 
 Co one of cobalt, Cr one of chromium, Cs one of caesium, Cu one of 
 copper (cuprum). 
 
 (The symbols of the elements are given in the table on 
 page 16.) 
 
 42. Symbols represent Atomic Masses. Each atomic 
 symbol stands not only for the atom in general, but repre- 
 sents particularly its atomic mass. 
 
 EXAMPLES. Fe (ferrum) represents 55'88 mass-units of iron, Sb 
 (stibium) 1196 mass-units of antimony, Hg (hydrargyrum) 199-8 
 mass-units of mercury, Ag (argentum) 107-66 mass-units of silver; 
 these being the atomic masses of these substances respectively. 
 
 43. Valence of Atoms, liow Indicated. The valence 
 of an atom is indicated by placing Roman numerals above 
 or a little to the right of the symbol. Sometimes minute- 
 marks are used instead. 
 
 EXAMPLES. H or H' Stands for the monad hydrogen-atom ; S or S" 
 for the bivalent sulphur-atom; 1* or P"' for the trivalent phosphorus- 
 atom; 0, C IV or C"" for the quadrivalent carbon-atom; Te or Te Vi for 
 the sexivalent tellurium-atom, etc. 
 
28 TffKOliETICAL CHEMISTRY. 
 
 44. Graphic Symbols. The graphic symbol of an atom 
 is a circle, with lines radiating from it to indicate its valence. 
 These lines are called bonds. Below is a graphic represen- 
 tation of the seven classes of atoms : 
 
 Monad. 'Dyad. Triad. Tetrad. P^iiad. Hexad. Heptad. 
 
 6 -o 
 
 Generally, however, the circles are omitted, the bonds 
 radiating from the symbol. The number of bonds only is 
 significant, not their direction. 
 
 EXAMPLES. Thus, O , O=, or O stands equally for one atom 
 of dyad oxygen. N=, N , or N=-, equally represents an atom of 
 trivalent nitrogen. 
 
 45. Multiplication of Atoms. Atoms are multiplied 
 by placing an Arabic numeral below and to the right of the 
 symbol. 
 
 EXAMPLES. C. 2 represents two atoms of carbon; N 4 , four atoms of 
 nitrogen ; K 3 , five atoms of potassium ; Pt :t , three atoms of platinum. 
 
 Elemental molecules are represented in the same way : 
 
 C1 2 stands for a molecule, composed of two atoms of chlorine, O.^ for 
 
 a molecule of ozone, As 4 for a molecule of arsenic, S 6 for a hexatomic 
 
 molecule of sulphur. 
 
 Care must be taken not to confound the valence marks, 
 expressed in Roman numerals, with the number of atoms, 
 represented by Arabic numerals. 
 
 EXAMPLES. L stands for three atoms of iodine, each of which is 
 a monad. Co., stands for two atoms of bivalent cobalt, 13 3 for five 
 
 IV 
 
 atoms of trivalent boron, Si 4 for four tetrad silicon-atoms. 
 
 46. Multiplication of Molecules. Molecules are mul- 
 tiplied by enclosing their symbols in brackets, and placing 
 the numeral outside, below, and to the right. 
 
 EXAMPLES. (H._,) 6 stands for six molecules of hydrogen. (Br,J., 
 represents two molecules of bromine. (Na. 2 ) 3 indicates three mole- 
 cules of sodium. 
 
KXERCISES. 29 
 
 EXERCISES. 
 
 1. Define analysis. Synthesis. 
 
 2. What is the distinction between elementary and compound 
 matter? 
 
 2. 
 
 3. How do chemists ascertain to which class a substance belongs? 
 
 4. How many kinds of atoms are known? 
 
 5. According to what rule are the elements named? 
 
 6. Give Avogadro's law and the deductions from it. 
 
 7. Show that a hydrogen-molecule contains two atoms. 
 
 8. The relative density of arsenic-vapor is 149-8; what is its molec- 
 ular mass? 
 
 9. The atomic mass of arsenic is 74-9; how many atoms are there 
 in its molecule? 
 
 10. The relative density of mercury in vapor is 99-9; its atomic 
 mass is 199-8; what is its atomicity? 
 
 11. Mention the molecules which have two atomicities. 
 
 3. 
 
 12. Define an atom. An atomic mass. 
 
 13. What data are necessary to fix an atomic mass? 
 
 14. Marsh-gas a compound of hydrogen and carbon has a rela- 
 tive density of 8; analysis shows it to be composed of 75 per cent 
 of carbon and 25 per cent of hydrogen ; what is the atomic mass of 
 carbon ? 
 
 15. The analysis of a compound of chlorine and antimony gives 
 40-61 per cent of chlorine and 53-39 per cent of antimony; its rela- 
 tive density is 112-85; what is the atomic mass of antimony? 
 
 16. How are positive atoms distinguished from negative? 
 
 17. Which of the following atoms are positive and which negative? 
 Silver and carbon; tin and lead; sulphur and chlorine; sodium and 
 iodine. 
 
 18. Define and illustrate valence. 
 
'><) THEORETICAL CHEMISTRY. 
 
 1'J. How are atoms classified by the law of' valence? 
 
 20. What is a dyad? A pentad? A trivalent akmi? A septiva- 
 lent atom? A perissad? An artiad? 
 
 21. How does the valence of an atom vary? 
 
 22. What valence has oxygen ? Nitrogen? Iron? Copper? 
 
 4. 
 
 23. What is meant by a natural family of elements? Illustrate 
 
 24. Define a periodic property. Why are the properties of the ele- 
 ments called periodic? 
 
 25. State the periodic law. Who were its discoverers? 
 
 26. Illustrate periodicity in the properties of the elements from the 
 table. How is a group of elements distinguished from a series? 
 
 27. What were the new elements whose existence and properties 
 were predicted by Mendeleeff? By what names did be indicate 
 them ? 
 
 28. How are atoms represented in symbols? 
 
 29. Give the symbols of tin, zinc, silver, sodium, aluminum. 
 
 80. For what do the symbols Pb, Ca, K, W, Si, Se, Mn, Mg, stand? 
 
 31. How are two dyad zinc-atoms written ? Four triad gold-atoms? 
 Six tetrad tin-atoms? Five hexad sulphur-atoms? 
 
 32. What do (fi,) G , (# 4 ) 2 , ffi^ t , and ( 6 ) represent? 
 
/.V.YJ/.T MOLECULES. 
 
 CHAPTER THIRD. 
 
 COMPOUND MOLECULES. 
 
 1. BINARY MOLECULES. 
 
 47. Definition. A compound molecule is a molecule 
 whose constituent atoms are unlike. 
 
 The number of atoms which such molecules may contain 
 is apparently unlimited. While a molecule of common salt 
 contains at least two atoms, a molecule of the potassium com- 
 pound of one of Dr. Gibbs's complex inorganic acids con- 
 tains 459. 
 
 48. Molecular Mass. The molecular mass of a com- 
 pound molecule, like that of a simple one, is the sum of the 
 atomic masses of its constituents. It is always equal to twice 
 the relative density of the substance in the state of gas. 
 
 49. Formation of Molecules. Compound molecules 
 are formed by the union of atoms according to the law of 
 valence. 
 
 Since the number of bonds, or units of attraction, is never 
 less than two one being furnished by every atom to each of 
 the others to which it is directly united the entire number 
 of bonds in any molecule must always be even. And since, 
 too, every perissad atom furnishes an odd number of bonds, 
 it follows necessarily, that the number of such atoms con- 
 tained in any molecule under normal conditions is always 
 even. 
 
 5O Classification o Compound Molecules. Com- 
 pound molecules are divided into two classes : 
 
 1st. Those whose atoms are directly united, called Bi- 
 naries. 
 
32 THEORETICAL CHEMISTRY. 
 
 2d. Those whose atoms are indirectly united, called Ter- 
 naries. 
 
 51. Binary Molecules. Binary molecules are those 
 whose atoms are directly united. Whatever the absolute 
 number of atoms present in such a molecule, they can never 
 be of more than two kinds. 
 
 EXAMPLES. A molecule of salt contains but a single atom each of 
 chlorine and of sodium ; a molecule of red-lead consists of seven 
 atoms, three of which are lead-atoms, and four oxygen -atoms. 
 
 52. Naming of Binary Molecules. The names of all 
 compound molecules are derived from those of their constitu- 
 ent atoms; a plan proposed by Lavoisier, in 1787. 
 
 A binary compound is formed by the union of two simple 
 substances, one of which, by the table, must be positive to 
 the other, which is negative. Binary molecules are named : 
 
 By placing- the name of the positive constituent first, 
 and then the name of the negative, the termination of 
 which is changed to ide. 
 
 EXAMPLES. 
 
 Sodium and Chlorine yield Sodium chloride. 
 
 Magnesium and Oxygen " Magnesium oxide. 
 
 Silver and Sulphur " Silver sulphide. 
 
 Zinc and Phosphorus " Zinc phosphide. 
 
 Calcium and Iodine " Calcium iodide. 
 
 Aluminum and Bromine " Aluminum bromide. 
 
 Potassium and Nitrogen " Potassium nitride. 
 
 Barium and Fluorine " Barium fluoride. 
 
 Cad mi am, and Selenium " Cadmium selenide, 
 
 The termination IDE is always characteristic of a binary 
 compound. 
 
 53. Modification of this Rule. Whenever the pos- 
 itive atom enters into combination with more than one 
 valence, this fact is indicated in the compound by changing 
 the termination of the name of this atom into ic or ous. 
 
OF BINARY MOLECULES. 33 
 
 If the positive substance acts with but two valences, then 
 in the higher one its name takes the termination ic, and in 
 the lower one the termination ous. 
 
 EXAMPLES. 
 
 Bivalent Mercury and Oxygen form Mercuric oxide. 
 Univalent Mercury " Oxygen " Mercurous oxide. 
 Quadrivalent Tin " Chlorine " Stannic chloride. 
 Bivalent Tin " Chlorine " Stannous chloride. 
 
 Trivalent Gold " Iodine " Auric iodide. 
 
 Univalent Gold " Iodine " Aurous iodide. 
 
 If the positive constituent acts with more than two va- 
 lences the termination ic being given on the discovery of 
 the compound is generally arbitrarily assigned. The prin- 
 cipal groups whose valences thus change, with the valence in 
 the ic compound, are the following : 
 
 CHLORINE GROUP. 
 
 SULPHUR GROUP. 
 
 NITROGEN GROUP. 
 
 Valence F. 
 
 Valence VI. 
 
 Valence V. 
 
 Chlorine 
 Bromine 
 Iodine 
 
 Sulphur 
 Selenium 
 Tellurium 
 
 Nitrogen 
 Phosphorus 
 Arsenic 
 
 A compound in which the valence of the positive is less 
 than in the ous, takes the prefix hypo, which means "under." 
 When this valence is above the ic, the prefix per is given to 
 the name of the positive. The negative termination, how- 
 ever, in all these cases continues to be ide. 
 
 EXAMPLES. 
 
 Septivalent Chlorine and Oxygen form Per-chloric oxide. 
 Quinquivalent Chlorine " Oxygen " Chloric oxide. 
 Trivalent Chlorine " Oxygen " Chlorous oxide. 
 
 Univalent Chlorine " Oxygen " Hypo-chlorous oxide. 
 
 Sexivalent Sulphur " Oxygen " Sulphuric oxide. 
 
 Quadrivalent Sulphur " Oxygen " Sulphurous oxide. 
 Bivalent Sulphur " Oxygen " Hypo-sulphurous oxide. 
 
34 THE(tKET1f'AL CHEMISTRY. 
 
 Quinquivalent Nitrogen and Oxygen form Nitric oxide. 
 Trivalent Nitrogen Oxygen " Nitrous oxide. 
 
 Univalent Nitrogen " Oxygen " Hypo-nitrous oxide. 
 
 54. Use of Numeral Prefixes. In some cases the 
 number of atoms of each constituent is to be indicated. This 
 is done by prefixing Greek numerals to each of the names 
 
 given. 
 
 EXAMPLES. 
 
 1 atom of C and 2 of O form Carbon di-oxide. 
 
 1 " of P " 5 of Br " Phosphorus penta-bromide. 
 
 2 atoms of Fe " 3 of O " Di-1'errie tri-oxide. 
 
 3 " of Ti " 4 of N " Tri-titanic tetra-nitride. 
 
 55. Notation of Binary Compounds. Formulas. 
 
 Notation is the representation of a substance in symbols. If 
 the substance be a compound one, this representation is called 
 a formula. 
 
 Binary molecules are represented by placing the symbols 
 of the constituent atoms together, the positive first. 
 
 EXAMPLES. 
 
 A molecule of Hydrogen chloride is HC1. 
 " " " Cupric oxide " CuO. 
 
 " " Silver iodide " Agl. 
 
 " " " Zinc sulphide " ZnS. 
 
 56. Use of Numerals in Formulas. When the num- 
 ber of atoms of any constituent in a molecule is more than 
 one, this is indicated by a numeral placed below and at the 
 right of its symbol. Compound molecules, like simple ones, 
 are multiplied by enclosing them in brackets, and placing 
 the numeral outside and to the right. 
 
 EXAMPLES. 
 
 SO., represents 1 molecule of Sulphuric oxide. 
 S(> 2 " Sulphurous oxide. 
 
 SO " " " Hypo-sulphurous oxide. 
 
 H.jO " " " " Hydrogen oxide (water). 
 
 Pb-jO^ " " " " Tri-plumbic tetr-oxide, 
 
NOTA WOK OF BINARY MOLECULES. 35 
 
 (Nad)., represents 2 molecules of Sodium chloride. 
 (CS. 2 ). 2 2 " " Carbon di-sulphide, 
 
 (l^^o).? 3 " " Phosphoric oxide. 
 
 (As.,S 3 ) 4 " 4 " " Arsenous sulphide. 
 
 (Pb(). 2 ) " 1 molecule " Lead di-oxide. 
 
 (PbO) 2 . " 2 molecules " Lead oxide. 
 
 57. Formation of Binaries. Binary molecules are 
 generally viewed as if formed by the direct union of their 
 constituent atoms. Two cases are here to be considered : 
 
 1st, When the valence of the atoms is the same. 
 
 2d. When the valence is different. 
 
 In all cases of chemical combination, the chemism of each 
 atom must be satisfied. Atoms having the same valence, then, 
 may mutually saturate each other. Such atoms, therefore, 
 unite in the ratio of one to one. 
 
 EXAMPLES. 
 
 K' and Cl', both monads, form K'Cl', or K Cl. 
 
 Ca" O", - dyads, Ca"O", " Ca=O. 
 
 B //> N /// t u triads> u B"'N"', " B^N. 
 
 p t iv gjiv, tetrads, " Pt'vSi'v, " Pt=Si. 
 
 When the atoms which enter into combination have a dif- 
 ferent valence, then each atom must furnish the same num- 
 ber of bonds. This number is, in all cases, the least common 
 multiple of the two valences. The absolute number of atoms 
 of each constituent is obtained by dividing this least common 
 multiple by the valence of each. 
 
 EXAMPLES. When triad- and dyad-atoms combine, each must fur- 
 nish six bonds the least common multiple of 3 and 2. But to furnish 
 six bonds, three dyad-atoms and two triad-atoms are required. Hence 
 the molecule will consist of two atoms of the triad and three of the 
 dyad. 
 
 So a tetrad uniting with a dyad will require four bonds the least 
 common multiple of 4 and 2 to furnish which one tetrad-atom and 
 two dyad-atoms are necessary. The following formulas still further 
 illustrate this law; 
 
36 THEORETICAL rH 
 
 H', a monad, and O", a dyad, form H'. 2 O". 
 N'", a triad, and O", a dyad, form N'^O",, 
 Sn lv , a tetrad, and 8", a dyad, form Sn'vS" 2 
 B'", a triad, and 01', a monad, form B'^Cl^ 
 Si lv , a tetrad, and F', a monad, form Si'VF' 4 
 Biv, a pentad, and S", a dyad, form Biv. 2 S" 5 
 P v , a pentad, and Br', a monad, form P^Br'.- 
 S, a hexad, and O", a dyad, form S VI O", 
 Cl vl1 , a heptad, and O" a dyad, form C1 VII .,O" 7 
 
 Where perissad- and artiad-atoms form a molecule, the 
 number of atoms required is inversely as the valence of 
 each. 
 
 This rule requires to be modified, however, in cases when; 
 atoms of the same polyad element unite with each other 
 directly; a condition of things appearing markedly in the 
 case of carbon. While one atom of carbon unites with four 
 of hydrogen, two atoms of carbon unite not with eight, but 
 with six hydrogen-atoms ; two of the bonds of the two car- 
 bon-atoms being occupied in holding these atoms together ; 
 thus 
 
 H H 
 
 H C C H 
 
 U 
 
 Consequently the maximum number of monad atoms with 
 which n carbon-atoms can combine is not 4n, but 2n-f 2. 
 Hence the homologous series CH 4 , C 2 H 6 , C 3 H H , C 4 H 10 , C 5 H 12 , 
 C 6 H 14 , etc., the members of which differ from those^preceding 
 or following them by CH 2 . 
 
 58. Exchange of Atoms in forming* Binaries. As 
 atoms do not exist free, they can not in fact form molecules 
 by directly combining. Binary compound molecules are 
 formed from the elemental molecules of their constituents, 
 which, being brought into proximity, have their .atoms re- 
 arranged ; the intensity of the chemical attraction between 
 
A TriiA TED MOLEC UL KS. 37 
 
 two dissimilar atoms being stronger than that exerted be- 
 tween two similar atoms. 
 
 EXAMPLES. A molecule of magnesium Mg Mg, when brought 
 in contact with one of oxygen O=^O, under suitable conditions will 
 exchange one of its magnesium-atorns for an atom of oxygen to form 
 two molecules of magnesium oxide Mg = O, O =Mg. It may be rep- 
 resented thus: 
 
 Mg O Mg = 
 
 Before || j| After 
 
 Mg O Mg = O 
 
 In the same way two molecules of hydrogen and one of oxygen 
 wiil form two molecules of hydrogen oxide or water, thus: 
 
 H O H II O H 
 
 Before | || | After 
 
 H O II H O H 
 
 59. Uiisaturated Molecules. Compound Radicals. 
 
 Besides the atomic groups now considered, called saturated 
 molecules because the bonds of all the atoms they contain 
 are mutually engaged, it is often convenient to distinguish 
 certain unsaturated groups of atoms, which, possessing free 
 bonds, may enter into combination like single atoms. These 
 uusaturated groups of atoms are frequently called com- 
 pound radicals. They can not exist in a free state in 
 nature, though, like an atom, by combining with another 
 similar group, they may form a molecule which is saturated. 
 Their valence is always equal to the number of unsatisfied 
 bonds ; i. e., is the difference of the valences of their constit- 
 uents. 
 
 EXAMPLES. "Water is H O H; by removing one hydrogen- 
 atom, there is left the unsaturated group H O , which, though 
 consisting of two atoms, is capable of entering into the formation of 
 a molecule like any single atom. It has one free bond, and hence 
 acts as a monad. But by combining with another similar group, it 
 forms H O O H, a free saturated molecule. This compound 
 radical may also be written (H'O")'. 
 
 So H. { N, a saturated molecule of ammonia, yields (H 2 N)', a monad 
 
 compound radical, by the loss of H'. I* a pentad phosphorus-atom, 
 
 4 
 
38 THEORETICAL CHEMISTRY 
 
 may be partially saturated by one oxygen-atom O", forming the triva- 
 lent compound radical (P'O")'"; or by two oxygen-atoms, gi /ing the 
 univalent radical (P'O 2 ")'. The former (PO)'"' may unite with Cl 
 like any other triad, forming (PO)"'C1 3 . 
 
 60. Names of Compound Radicals. Compound rad- 
 icals have names terminating in yl. The root of the name 
 comes either from their constituents or from some compound 
 into which they enter. 
 
 EXAMPLES. The compound radical (HO/ is called hydroxyl; 
 (PO)'" is named phosphoryl ; (CO)" carbonyl, (CH 3 )' methyl, from 
 methyl alcohol, of which it is a constituent. Three compound rad- 
 icals, (H 2 N)' amidogen, (CN)' cyanogen, and (H 4 N V )' ammonium, are 
 exceptions to this rule. 
 
 61. Artiad and Perissad Radicals. Perissad radicals, 
 having an uneven number of free bonds, can exist free only 
 by combining with each other, as above stated. Artiad rad- 
 icals, having an even number of free bonds, may exist in the 
 free state by the mutual saturation of these bonds by each 
 other. 
 
 EXAMPLES. Nitryl (NO 2 )', a perissad radical, can not exist free. 
 But by combining with another group, (NO 2 ) (NO 2 ) is produced, 
 
 H H 
 
 which is saturated. Ethylene, H C H or (C.,H 4 )" is a 
 
 I I 
 
 bivalent radical; but by doubly uniting the carbon, oleliant gas 
 H H 
 
 H C = C H results. Carbonyl O=:C is a dyad radical, 
 O = C> is free carbon monoxide. 
 
 62. Explanation of Variation in Atomic Valence. 
 
 By a similar hypothesis some chemists have attempted to 
 explain the variation in atomic valence. An atom is assumed 
 to have but one valence, which is the highest it ever exhibits. 
 If now two of its bonds mutually saturate each other, the 
 atom has a less valence by two ; if two pairs thus saturate, 
 
TKll AV/ /,' I " MOL EC ULES. 39 
 
 by four ; if three, by six. A heptad may thus become a 
 pentad, triad, and monad successively ; and a hexad may be- 
 come a tetrad, and a dyad ; as the following graphic formu- 
 las show : 
 
 Pentad. Triad. Monad. 
 
 Hexad. Tetrad. Dyad. 
 
 ^ 
 
 In the case of those elements which, like mercury, copper, 
 iron, vanadium, etc., appear to act with an even valence in 
 some of their compounds and with an odd valence in others, 
 we can only accept the fact and write the formulas in the 
 simplest way ; awaiting new light upon the nature of valence 
 itself, in order to explain the anomaly. 
 
 63. Names of Molecules formed by Radicals. 
 Molecules which contain compound radicals united to ele- 
 mentary atoms are classed as binaries and are named in the 
 same way. 
 
 EXAMPLES. Nitryl (NO 2 ) y and chlorine form nitryl chloride 
 (NO 2 )'C1. Carbonyl (CO)" and sulphur form earbonyl sulphide 
 (CO)"S. Methyl (CH,)' and oxygen form (CH 3 )' 2 O, methyl oxide. 
 
 2. TERNARY MOLECULES UNITED BY DYADS. 
 
 64. Classification of Ternary Molecules. Ternary 
 molecules are those whose dissimilar atoms are united by the 
 aid of some third atom. This third atom, which performs a 
 linking function, must evidently be a polyad, since no monad 
 can join other atoms together. 
 
 Ternary molecules are divided into two classes according 
 to the valence of the uniting atom : 
 
40 THEORETICAL CHEMISTRY. 
 
 1st. Ternary molecules united by bivalent atoms. 
 2d. Ternary molecules united by trivalent atoms. 
 
 65. Ternary Molecules united by Dyads. The dyads 
 oxygen, sulphur, selenium, and tellurium, may perform a 
 linking function. Of the compounds thus formed, by far 
 the larger proportion are compounds of oxygen. Oxygen, 
 therefore, is the distinguishing component of this class of 
 bodies. 
 
 66. Ternary Molecules linked by Oxygen. Oxy- 
 gen, by its two bonds, may unite two atoms or groups of 
 atoms together. Bodies thus constituted are divided into 
 three classes, according to the character of the atoms which 
 are thus united. These classes are called acids, bases, or 
 salts. 
 
 67. Definition of an Acid. An acid molecule is one 
 which consists of one or more negatiye atoms united by 
 oxygen to hydrogen. 
 
 The general formula of an acid, therefore, is R O H. 
 The number of hydrogen-atoms which it contains is equal to 
 the valence of the negative atom or group of atoms. In 
 general, acids are recognized by the property which they 
 possess of turning certain vegetable blues to red. 
 
 68. Definition of a Base. A basic molecule consists 
 of one or more positive atoms united by oxygen to hy- 
 drogen. 
 
 A base is the analogue of an acid. It has the general 
 
 formula R O H, the number of hydrogen - atoms de- 
 pending, as before, upon the valence of the positive atom or 
 atomic group. Bases restore the color to vegetable blues 
 which have been reddened by an acid. 
 
 69. Definition of a Salt. A saline molecule is one 
 which contains a positive atom or group of atoms united 
 by oxygen to a negative atom or group of atoms. 
 
 The general formula of a salt is R R, As it con- 
 
TERNARY MOLECULES. 41 
 
 tains no hydrogen it has neither acid nor basic properties, 
 and is therefore without action upon vegetable colors. 
 
 70. Water Type. A molecule of water consists of two 
 atoms of hydrogen linked together by oxygen, thus: H O 
 
 H. By exchanging one of these hydrogen-atoms for a 
 negative monad, an acid, R O H, is produced. By a 
 similar exchange for a positive atom, a base, R O H, is 
 obtained. By replacing both of the hydrogen-atoms, one by 
 a positive the other by a negative atom, a salt, R O R, 
 results. Hence these three classes of bodies are sometimes 
 said to be formed upon the plan of structure of water ; that 
 is, upon the water type. 
 
 Acids and bases may also be viewed as compounds of the 
 monad radical hydroxyl. If hydroxyl H O unite with 
 
 R, it forms an acid R O H; if with R, it gives a base R 
 O H. This method of viewing acids and bases is conven- 
 ient for many purposes. 
 
 71. Naming- of Acids, Bases, and Salts. Acids, bases, 
 and salts, like binaries, are named from their constituent 
 atoms. The termination of the negative is changed, how- 
 ever, to indicate that the atoms are linked by oxygen. These 
 negative ternary terminations are universally ate and ite. 
 
 EXAMPLES. Potassium and sulphur when directly united, form 
 potassium sulphide; when united by oxygen, potassium sulphate, sul- 
 phite, or hypo-sulphite, according to the valence of the sulphur. The 
 binary hydrogen nitride becomes, by the introduction of linking oxy- 
 gen, hydrogen nitrate or nitrite, both ternary acids. And in the same 
 way, copper hydride becomes copper hydrate. 
 
 The name hydroxide is sometimes used to indicate a more 
 intimate union or a chemical union proper ; the word hydrate 
 being employed to signify a less intimate physical or molec- 
 ular union. Thus, if sodium oxide unites with hydrogen 
 oxide, sodium hydroxide results ; while if sodium carbonate 
 so unites, a hydrate of sodium carbonate is the product. 
 
42 THEORETICAL CHEMISTRY. 
 
 72. Change in Termination of the Positive Atom. 
 
 The positive atom, as in binaries, retains its name unaltered 
 except when it acts with more than one valence. It then 
 takes the termination ous and ic. 
 
 EXAMPLES. Mercurous and mercuric nitrates, cuprous and cuprio 
 sulphates; ferrous and ferric phosphates, stannous and stannic sili- 
 cates, etc. 
 
 73. Common Names of Acids and Bases. As both 
 acids and bases contain oxygen and hydrogen, they are com- 
 monly named from the characteristic constituent, giving it 
 the termination ic or ous, according to its valence, and add- 
 ing the word acid or base. 
 
 EXAMPLES. The common name of hydrogen sulphate is sulphu- 
 ric acid; of hydrogen nitrite, nitrous acid; of hydrogen phosphate, 
 phosphoric acid; of hydrogen hypo-chlorite, hypo-chlorous acid. So 
 too, calcium hydrate is calcic base; zinc hydrate, zincic base; ferric 
 hydrate, ferric base; ferrous hydrate, ferrous base; aluminic hydrate, 
 aluminic base. 
 
 74. Formation of Ternary Molecules. Ternary mole- 
 cules are formed in two ways: 
 
 1st. By the direct union of binary molecules. 
 2d. By substitution, from each other. 
 
 75. Formation of Ternaries hy Direct Union. Ter- 
 naries are formed by the direct union of the oxide of a more 
 positive atom with the oxide of a less positive or negative 
 one. In this case, the name oxide is dropped, and the name 
 of the negative takes ate if it terminated before an ic ; or 
 ite if it ended before in ous. Whenever water is the nega- 
 tive oxide, the body produced is a base ; when it is the posi- 
 tive, the ternary is an acid. 
 
 EXAMPLES. Sodium oxide and phosphoric oxide unite to form 
 sodium phosphate; here the "oxide" of both is dropped, and the ic of 
 the negative oxide is changed into ate. So calcium oxide and sulphu- 
 rous oxide form calcium sulphite. Silver oxide and hypo-chlorous 
 oxide form silver hypo-chlorite. Again, when hydrogen oxide wa- 
 ter unites with sulphuric oxide, hydrogen sulphate, or sulphuric 
 
TERNARY MOLECULES. 43 
 
 acid, results; when it unites with potassium oxide, potassium hydrate 
 (or hydroxide) is produced, the water being now negative. 
 
 Negative oxides are sometimes called anhydrides, because 
 they may be formed from acids by the abstraction of water. 
 
 76. Formation of Ternaries by Substitution. Ter- 
 naries are also formed from each other, by substitution. An 
 acid, by exchanging its hydrogen for a positive atom, becomes 
 a salt ; a base, exchanging its hydrogen for a more negative 
 substance, becomes also a salt ; a salt may become an acid or 
 a base, according as its positive or its negative constituent is 
 replaced by hydrogen ; and by exchanging positive for nega- 
 tive atoms, or the reverse, bases may be converted into acids 
 or acids into bases. 
 
 EXAMPLES. Hydrogen chlorate or chloric acid, by exchanging its 
 hydrogen for barium, becomes barium chlorate, a salt. Lithium hy- 
 drate, or lithic base, by exchanging its hydrogen for carbon, becomes 
 lithium carbonate, also a salt. So magnesium silicate becomes hydro- 
 gen silicate or silicic acid, by replacing its positive portion by hydro- 
 gen, and magnesium hydrate or magnesic base, by replacing its nega- 
 tive portion "by the same element. 
 
 Whenever a base and an acid are brought in contact, a 
 salt and water are produced. Or, graphically, R O H 
 and R-O-H produce R-O-R and H-O-H. 
 
 77. Classification of Acids. Acids are divided into 
 two classes, called normal or ortho-acids and meta-acids. 
 
 1st. Ortho-acids are those acids in which all the oxygen 
 has a linking function. In these acids, therefore, there are 
 as many atoms of hydrogen and of oxygen i. e., of hy- 
 droxyl as is equal to the valence of the negative atom rr 
 atomic group. 
 
 EXAMPLES. 
 
 Clvi'(OH) 7 is ortho-perchloric acid. 
 C1 V (OH) 5 is ortho-chloric acid. 
 C1'"(OH) 3 is ortho-chlorous acid. 
 Cr(OH) is ortho-hypo-chlorous acid. 
 
44 THEORETICAL CHEMISTRY. 
 
 S VI (OH) 6 is ortho-sulphuric acid. 
 S IV (OH) 4 is ortho-sulphurous acid. 
 S''(OH) 2 is ortho-hypo-sulphurous acid. 
 
 2d. Meta-acids are acids which contain saturating as well 
 as linking oxygen. The oxygen atoms therefore, in a meta- 
 acid, always exceed the hydrogen atoms. 
 
 EXAMPLES. 
 
 (CIO)'(OH) is meta-chlorous acid or hydrogen metn-chlorite. 
 (CO)"(OH). 2 is meta-carhonic acid or hydrogen mete-carbonate. 
 (PO)"'(OH) 3 is meta-phosphoric acid or hydrogen meta-phosphate. 
 (CrO)' v (OH) 4 is mete-chromic acid or hydrogen meta-chromate. 
 (IO) V (OH) 5 is meta-pcr-iodic acid or hydrogen meta-per-iodate. 
 
 78. Formation of Meta-acids. Meta-acids are derived 
 from ortho-acids by subtracting from them one or more mole- 
 cules of water ; the acid being mono-, di-, or tri-meta, accord- 
 ing to the number of molecules of water taken from the 
 ortho-acid to form it. 
 
 EXAMPLES. 
 
 Svi(OH) 6 , less H 2 O, leaves (SO)'V(OH) 4 , mono-meta-sulphuric acid. 
 S VI (OH) 6 , less (H 2 O) 2 , leaves (SO 2 )"(OH).,, di-nieta-suiphuric acid. 
 NV(OH) 3 , less H 2 O, leaves (NO)'"(OH). 5 , mono-meta-nitric acid. 
 NV(OH) 5 , less (H 2 O) 2 , leaves (NO 2 ) / (OH), di-meta-nitric acid. 
 As'"(OH),,, less H 2 O, leaves (AsO)'(OH), mono-meta-arsenous acid. 
 
 The precise manner in which the molecule is affected by 
 this abstraction of water is represented by the following 
 graphic formulas showing the production of the meta-per- 
 chloric acids : 
 
 OrtJto- Mono-meta- Di-mela- Tri-meia- 
 
 perchloric. perchloric. perchloric. perchloric. 
 
 ^cz^ ^a^ ^0-^1=0 o=a=o 
 
 $ Q, o ^ o o 
 
 Every molecule of water thus removed, it should be ob- 
 
TERNARY MOLECULES. 45 
 
 served, leaves one atom of saturating oxygen. Hence every 
 mono-meta-acid has one such atom, every di-meta-acid two, 
 and every tri-meta-acid three. 
 
 TABULAR VIEW OF ORTHO- AND META-ACIDS. 
 
 Monads Dyads Triads Tetrads Pentads Hexads Heptads 
 
 Mono-meta HKO, H.AiO, H,fiO 4 H 4 ^O. H- V iiO,. 
 
 <5 & o .1 4 4 D o f 
 
 Di-meta Hlk) 3 HjlO 4 H 3 V Jk> 5 
 
 Tri-meta HKO 4 
 
 79. Basicity of Acids. The hydrogen in an acid which 
 is linked to the atomic group by oxygen is called basic 
 hydrogen because it is readily exchanged for a more posi- 
 tive atom or group of atoms. Acids are said to be mono- 
 basic, di-basic, tri-basic, or tetra-basic, according as they con- 
 tain one, two, three, or four atoms of basic hydrogen. All 
 acids are poly-basic which contain within their molecules 
 more than one of these hydroxyl groups. 
 
 EXAMPLES. 
 
 (NO.,)'(OH), di-meta-nitric acid, is monobasic. 
 (CO)"(OH) 2 , mono-meta-carbonic acid, is dibasic. 
 B /// (OH) 3 , ortho-boric acid, is tribasic. 
 
 In all ortho-acids the basicity is, of course, equal to the 
 valence of the negative atom. 
 
 80. Ortlio- and Meta-bases. Like acids, bases may be 
 either ortho- or meta-, and for the same reasons. But, since 
 positive atoms rarely vary in valence, but a very few meta- 
 bases are known. 
 
 EXAMPLES. 
 
 K'(OH) is ortho-potassic base, or ortho-potassium hydrate. 
 Ca"(OH)., is ortho-calcic base, or ortho-calcium hydrate. 
 Pt lv (OH) 4 is ortho-platinic base, or ortho-pi atinic hydrate. 
 Fe. 2 vl (OH) H is ortho-ferric base, or ortho-ferric hydrate. 
 ZrO(OH). 2 is meta-zirconic base, or meta-zirconium hydrate. 
 Fe 2 viO a (OH) 2 is di-meta-ferric base, or di-meta-ferric hydrate. 
 
46 THEORETICAL CHEMISTRY. 
 
 81. Acidity of Bases. The hydrogen of a base is called 
 acid hydrogen, because it is replaceable by a negative atom. 
 The acidity of a base depends upon the number of hydroxyl 
 groups, like the basicity of an acid. Bases are mon-acid, di- 
 acid, tri-acid, etc., as acids are mono-basic, etc. 
 
 EXAMPLES. 
 
 Argentic base Ag'(OH) is mon-acid. 
 Ferrous base Fe"(OH)., is di-acid. 
 Aluminic base A1'"(OH) 3 is tri-acid. 
 
 82. Formation of Stilts. Salts are formed from acids 
 by replacing their basic hydrogen by positive atoms. 
 
 If the acid has its systematic name, the name of the salt 
 is obtained from it by putting the name of the positive atom 
 in place of the hydrogen. 
 
 If the acid has its common name, the name of the salt is 
 formed by placing the name of the positive atom first, fol- 
 lowed by that of the acid, the termination ic being changed 
 
 to ate, and cms to ite. 
 
 EXAMPLES. 
 
 Hydrogen nitrate, or nitric acid, and sodium, give sodium nitrate. 
 
 Hydrogen chlorite, or Chlorous acid, and barium, give barium chlo- 
 rite. 
 
 Hydrogen bypo-iodite, or bypo-iodous acid, and zinc, give zinc 
 hypo-iodite. 
 
 83. Formulas of Salts. In writing the formula of a 
 salt, regard must be had both to the basicity of the acid 
 and to the valence of the replacing atom. As many mole- 
 cules of the acid must be taken as is necessary to furnish a 
 number of hydrogen-atoms equal to the least common mul- 
 tiple of the basicity of the acid and the valence of the re- 
 placing atom. 
 
 EXAMPLES. It is required to write the formula of calcium phos- 
 phate. Calcium phosphate is derived from hydrogen phosphate 
 phosphoric acid --by replacing hydrogen by calcium. The formula 
 of mono-meta-phosphoric acid the most common form, and there- 
 fore referred to when no other is specified is PO"'(0H.) 8 or more 
 
TERNARY MOLECULES. 
 
 47 
 
 conveniently, H ;J PO 4 . Calcium is a dyad ; the acid is tri-basic ; the 
 least common multiple of two and three is six; as many molecules 
 of the acid are required as is necessary to yield six hydrogen atoms ; 
 this number is two, written (HjPO 4 ) g , or for convenience of replace- 
 ment H 6 (PO 4 ). ; . The six atoms of hydrogen can be exchanged for 
 
 three of Ca"; makins 
 phosphate. 
 
 this change, we have Oa" 3 (PO 4 ) 2 , or ealciiur. 
 
 Mono-basic Acids. 
 
 Sodium nitrate. 
 Calcium nitrite. 
 Bismuthous chlorate. 
 Zirconium phosphate. 
 
 Potassium sulphite. 
 Barium carbonate. 
 Auric chromate. 
 Platinic sulphate. 
 
 Silver arsenate. 
 Zinc iodate. 
 Bismuthous nitrate. 
 Stannic antimonite. 
 
 Caesium silicate. 
 Ferrous selenate. 
 Auric carbonate. 
 Zirconium tellurite. 
 
 84. Salts derived from Bases. Salts may be derived 
 from bases as well as from acids. They are viewed as so 
 derived only in a few cases, where they form a peculiar class 
 of basic salts. 
 
 85. Normal, Acid, Basic, and Double Salts. Nor- 
 mal salts are salts which contain neither basic nor acid 
 hydrogen.* They are formed by the complete replacement 
 of the hydrogen of an acid or a base. 
 
 Acid salts are those which contain basic hydrogen. 
 
 Na' 
 Ca" 
 Bi'" 
 Zr'v 
 
 and HNO 3 
 
 and (HNO. 2 ) 2 
 and (HC1O 3 ) 3 
 and (HPO 3 ) 4 
 
 give Na'NO 3 
 " Ca"(NO 2 ) 2 
 
 
 
 Di-basic Acids. 
 
 Ba" 
 ' Au'" 2 
 
 Pt'v 
 
 and H 2 SO 3 
 and H. 2 CO :5 
 
 and (H,CrO 4 ), 
 and (H~S0 4 ) 2 
 
 give K' 2 SO 3 
 " Ba"CO., 
 
 
 
 Tri-basic Adds. 
 
 Ag' 3 
 Zn", 
 Bi'" 
 
 and H 3 AsO 4 
 
 and (H 3 IO 4 ) 2 
 and H 3 NO 4 
 and (H,SbO 3 ) 4 
 
 give Ag'gAsOj 
 
 ; Zn" 3 (I0 4 ). 2 
 " Bi'"(NO 4 ) 
 " Sniv 8 (Sb0 3 ) 4 
 
 
 
 Tetra-basic Acids. 
 
 Cs' 4 
 Fe" 2 
 Au"' 4 
 
 Zr'v 
 
 and H 4 SiC 4 
 and H 4 SeO- 
 and (H 4 CO 4 ) :5 
 and H/TeCX 
 
 give Cs 4 SiO 4 
 " Fe" 2 SeO 5 
 Au /// 4 (C0 4 ), 
 " Zr'VTeO, 
 
48 THEORETICAL CHEMISTRY. 
 
 The replacement in the acid being only partial, the salt still 
 acts like an acid, turning vegetable blues to reds. 
 
 Basic salts are salts formed by the partial replace- 
 ment of the hydrogen of a base by a negative atom. 
 They contain therefore acid hydrogen, and often act like a 
 base upon vegetable colors. 
 
 Double salts are salts containing two or more differ- 
 ent positive atoms. 
 
 EXAMPLES. 
 
 Normal Salts. Acid Salts. 
 
 Potassium chlorate KC10 3 Hydro-sodium sulphite HNaS0 3 
 
 Calcium sulphate Ca"SO 4 Hydro-caesium carbonate HCsCO. } 
 
 Bismuthous phosphate Bi'"PO 4 Hydro-barium phosphate HBaPO 4 
 Sodium silicate Na 2 SiO 3 Hydro-cupric silicate H 2 CuSiO 4 
 
 Basic Salts. 
 
 Lead hydro-nitrate H(NO 2 ) / PbO a 
 
 Copper hydro-acetate H(Ac) / CuO 2 
 Mercuric hydro-iodite H(IO)'HgO.j 
 
 Aluminic hydro-silicate H 2 Si lv Al 2 O G 
 
 Double Salts. 
 
 Potassio sodium selenate KNaSeO 4 
 Sodio-caloiurn antimonate NaCa"SbO 4 
 Baro-zincic silicate Ba // Zn // SiO 4 
 
 Caesio-rubidic carbonate Cs'Rb'CO :i 
 
 Mono-basic acids can form only normal salts. Poly-basic 
 acids can form normal, acid, and double salts. 
 
 86. Empirical and Rational Formulas. An empir- 
 ical or experimental formula is one derived from analysis. 
 It expresses the kind and relative number of atoms in the 
 molecule. It may be also a true molecular formula, in 
 which case it expresses the absolute number of atoms the 
 molecule contains. 
 
 A rational formula not only expresses the kind and the 
 absolute number of atoms contained in any molecule, but 
 also indicates how those atoms are arranged. All graphic 
 formulas are rational. 
 
V'AV.'.V. I /' 1 ' MOL ECULES. 49 
 
 EXAMPLES. HNO 3 , CaCl 2 O 2 , HgCl, CuClO 3 , are all empirical for- 
 mulas, derived from analysis. The first two are molecular, and ex- 
 press the absolute number of atoms; but the molecular formulas of 
 the second two are Hg 2 Cl 2 and Cu 2 Cl 2 O 6 , the molecule having twice 
 the mass in each case. 
 
 The rational formulas of the four bodies above given, represented 
 graphically, are: 
 
 O 01 O O 
 
 II I Hg-Cl |! || 
 
 N OH, Ca and Cl O Cu Cu O Cl 
 
 II I Hg-Cl, || || 
 
 O O-C1, O O 
 
 The same substances are thus represented in symbols: 
 
 /MO MW r T f CuO(CK).,) 
 
 (N0 2 )OH, Ca'' and2 
 
 \ CuO(ClO 2 ) 
 
 87. Sulphur and Selenium Acids, Bases, and Salts. 
 
 The atoms of ternary molecules may be united by the neg- 
 ative dyads sulphur and selenium, as well as by oxygen. 
 These molecules are named and formulated in precisely the 
 same way as those formed by oxygen, and are distinguished 
 from these by the prefix sulph- or selen-, given to the neg- 
 ative name. 
 
 EXAMPLES. 
 
 As(OH) 3 Hydrogen arsenite As(SH) 3 Hydrogen sulph-arsenite. 
 Sb(OAg) 3 Silver antimonite Sb(SAg) 3 Silver sulph-antimonite. 
 SbO(ONa) 3 Sod. antimonate SbS(SNa) 3 Sod. sulph-antimonate. 
 SbO(OK) 3 Potas. antimonate SbSe(SeK) 3 Potas. selen-antirnonate. 
 
 The sulphur and selenium in a molecule may be saturat- 
 ing, or linking, or both. These two substances, and also 
 oxygen, may co-exist in the same molecule. 
 
 3. TERNARY MOLECULES UNITED BY TRIADS. 
 
 88. Classification of Molecules united by Nitrogen. 
 
 The negative triads which may perform a linking function 
 are nitrogen, phosphorus, and arsenic. Of these, but a few 
 compounds united by phosphorus or arsenic, and these com- 
 
50 THEORETICAL CHEMISTRY. 
 
 paratively unimportant, are known. Molecules whose atoms 
 are united by nitrogen are divided into three classes, on the 
 same principle upon which those united by negative dyads 
 are classified. These classes are called amides, amines, arid 
 alkalamides. 
 
 89. Definition of an Amide. An amide is made up 
 of molecules consisting of one or more negative atoms united 
 by nitrogen to hydrogen. 
 
 The general formula of an amide is R N=H. 2 . 
 
 90. Definition of an Amiiie. An amine-molecule 
 consists of one or more positive atoms united by nitrogen 
 to hydrogen. 
 
 The general formula of an amine is R N=H. 2 . 
 
 91. Definition of an Alkalamide. An alkalamide- 
 molecule contains both positive and negative atoms united 
 
 by nitrogen. H 
 
 i + 
 The general formula of an alkalamide is R N R. 
 
 92. Ammonia Type. An ammonia -molecule consists 
 of three hydrogen-atoms linked together by nitrogen thus, 
 
 H 
 
 i 
 H N H. By exchanging a portion of the hydrogen for 
 
 one or more negative atoms, an amide results ; for one or 
 more positive atoms an amine is obtained; and for one posi- 
 tive and one negative, an alkalamide results. These three 
 classes of bodies have a structure similar to that of ammonia. 
 They are said therefore to belong to the ammonia type. 
 Amides and amines are often regarded as compounds of 
 
 the monad radical (H 2 N)', amidogen. United to R, it gives 
 an amide ; to R, an amine. 
 
 93. Naming' of Derived Ammonias. Amides and 
 amines are called primary, secondary, or tertiary, accord- 
 ing as one, two, or three of the hydrogen-atoms are replaced. 
 The individual substances are named by prefixing the Greek 
 numerals to the name of the replacing atom. 
 
TERNARY MOLECULES, 
 
 51 
 
 EXAMPLES. Writing ammonia thus 
 
 H) 
 
 , HlN, 
 HJ 
 
 we may have 
 
 Primary. 
 
 Cyanamide. 
 
 K) 
 
 H IN 
 
 HJ 
 
 PotOMamine. 
 
 Secondary. 
 
 Tertiary. 
 
 UN 
 
 HJ 
 
 CI) 
 
 ci IN 
 01 J 
 
 Din-lodamide. 
 
 Tri-chloramide. 
 
 Na) 
 Na IN 
 HJ 
 
 Kb) 
 
 Kb IN 
 
 Rhj 
 
 JM-sodamine. 
 
 Tri-rubidam inc. 
 
 K) 
 
 K ) 
 
 ci IN 
 
 K N 
 
 HJ 
 
 cij 
 
 Amide 
 
 Amine 
 
 Alkalamide 
 
 Chloro-potassa mide. Chloro-di-potaxsamiffr. 
 
 Amides, amines, and alkalamides, regarded as derivative 
 ammonias, are called mon-amides, di-amides, tri-amides, 
 tetr-amides, etc., according to the number of nitrogen- 
 atoms in the type. 
 
 EXAMPLES. 
 
 Amide 
 
 Amine 
 
 Alkalamide 
 
 Tertiary derivatives are included here because of their 
 similar origin. Many of them really belong with binary 
 compounds. These bodies are sometimes called nitriles, and 
 secondary derivatives are sometimes called imides. 
 
 Mono. 
 
 Di 
 
 Tri. 
 
 (No 2 n 
 
 H IN 
 
 Hj 
 
 (CO)-) 
 
 ^ 
 
 (pori 
 
 %h 
 
 Nitryl-mon-amide. 
 
 Carbonyl-di-amide. 
 
 Phoxphoryl-tri-amide. 
 
 Na) 
 
 H IN 
 
 HJ 
 
 Zn" ) 
 
 ^' 
 
 Bi w 1 
 
 %h 
 
 Sodio-mon-amine. 
 
 Zinc-di-amine. 
 
 Bismuth-tri-amine. 
 
 Nftl 
 
 IN 
 HJ 
 
 (C0)"l 
 
 xh 
 
 ftri 
 
 ( Por}M 3 
 
 Sodio-iod-amide. 
 
 Mercuro-carbonyl- 
 di-amidc. 
 
 Bismuth-phosphoryl- 
 tri-amide. 
 
52 
 
 THEORETIC A L CHE AILS 77,' I . 
 
 94. Mixed Compounds of Hydroxyl and Ainido- 
 g'eii. As those bodies which are formed on the water type 
 may be viewed as binary compounds of hydroxyl, and those 
 which are formed on the ammonia type as similar compounds 
 of amidogen, it is evident that a poly-equivalent radical may 
 combine with both these residues at once, thus forming com- 
 pounds intermediate between those of the two groups men- 
 tioned. If the poly-equivalent radical be negative, the bodies 
 produced are called amic acids ; if positive, amid-hy- 
 drates. 
 
 EXAMPLES. Sulphury! (SO^)", the radical of sulphuric acid, forms 
 in this way sulphamic acid (SO 2 )" < \i\ii ? And zinc, a positive dyad, 
 forms Zii | S zin cam id-hdrate. 
 
 Molecules 
 
 TABULAR VIEW OF MOLECULAR STRUCTURE. 
 
 ijiKe At( 
 
 nns .... 
 
 United directly 
 
 
 jcaemei 
 
 Binary 
 
 
 
 [ R and H, 
 
 Acid 
 
 Unlike 
 Atoms 
 
 
 By a Dyad 
 
 j R and H, 
 
 Base 
 
 
 United 
 
 
 [ R and R, 
 
 Salt 
 
 L indirectly 
 
 
 f - 
 
 
 
 
 1 R and H, 
 
 Amide 
 
 
 . By a Triad 
 
 ] R and H, 
 
 Amine 
 
 
 - + 
 
 
 95. Recapitulation. I. Molecules are of two classes : 
 1st. Those composed of like atoms and called Element- 
 ary. 
 
 2d. Those composed of unlike atoms and called Com- 
 pound. 
 
 II. All compound molecules are of two classes : 
 1st. Those whose atoms are directly united, called Binary. 
 2d. Those whose atoms are indirectly united, called Ter- 
 nary. 
 
TERNARY MOLECULES. 53 
 
 III. Ternary molecules are of two classes : 
 
 1st. Those in which the linking atom is a dyad, called 
 Hydrates. 
 
 2d. Those in which the linking atom is a triad, called 
 Compound Ammonias. 
 
 IV. Hydrates are divided into three classes : 
 
 1st. Acid hydrates, or acids, which consist of a negative 
 atom or radical, united to hydrogen. 
 
 2d. Basic hydrates, or bases, which consist of a positive 
 atom or radical, united to hydrogen. 
 
 3d. Salts, which consist of a positive atom or radical, 
 united to a negative atom or radical. 
 
 V. Compound Ammonias are divided into three classes : 
 1st. Amides, containing a negative radical united to hy- 
 drogen. 
 
 2d. Amines, containing a positive radical united to hy- 
 drogen. 
 
 3d. Alkalamides, containing a positive radical united to 
 a negative radical. 
 
54 THEORETICAL CHEMISTRY. 
 
 EXERCISES. 
 
 1. How many atoms may a compound molecule contain? 
 
 2. How is the molecular mass of such a molecule obtained? 
 
 3. How many bonds may there be in a compound molecule? How 
 many perissad atoms? 
 
 4. Define a Binary molecule, A Ternary molecule. 
 
 5. Give the rule for naming Binaries. Illustrate it. 
 
 6. Platinum forms two compounds with bromine; name them. 
 
 7. What atoms have more than two valences? 
 
 8. What are the oxides of phosphorus? The chlorides? 
 
 9. What are formulas, and how are they written? 
 
 10. Give the formula of potassium iodide; of lead sulphide; of 
 phosphorous nitride; of calcium chloride; of gold oxide; of silver 
 arsenide; of silicic bromide; of antimorious oxide. 
 
 11. Give the names of NaCl, SrO. BiP, Cu.,As 2 , (CS 2 ) 2 , (SnO) 4 . 
 
 12. How do atoms of different valences combine? 
 
 13 How are compound molecules formed from elemental ones? 
 
 14. Define compound radicals. How are they named? 
 
 15. How is variation in atomic valence explained? 
 
 2. 
 
 16. How are ternary molecules united? By what dyads? 
 
 17. Define and explain the general formula of an acid, a base, and 
 a salt. 
 
 18. What is the water type? 
 
 19. What compounds are formed by the union of potassium to. 
 monad, triad, pentad, and heptad chlorine successively, by oxygen? 
 
 20. What are the constituents of silver phosphate; lithium carbon- 
 ate; zinc hydrate; hydrogen bromate; rnanganous phosphate; mer- 
 curous nitrate? *-- 
 
 21. What are the formulas of silicic, chromic, iodous, carbonic, hypo- 
 sulphurous, bromous, and titanic acids? 
 
 22. Illustrate the formation of ternaries by direct union. 
 
 23. What is produced when lead oxide and nitrous oxide unite? 
 bismuthous and selenic oxides? hydrogen and sulphuric oxides? 
 
EXERCISES. 55 
 
 24. How is barium sulphite produced by substitution? Mercurous 
 hypo-chlorite? 
 
 25. Define ortho- and meta- acids. How are the latter derived? 
 
 26. Which is H 3 PO 4 ? HC10? HAsO 2 ? H 2 SeO 2 ? H 4 WO 5 ? 
 
 27. Give the general formula of the mona-meta-acid of a triad ; of 
 a pentad; of a hexad. 
 
 28. Define basicity of acids. What is a tetra-basie and a poly-basic 
 acid ? 
 
 29. What is a poly-acid base? What is HNaO? H 2 BaO. 2 ? HAuO 2 ? 
 H 3 Bi0 3 ? 
 
 30. How is the name of a salt derived from that of an acid? 
 81. Give the rule for writing salt-formulas. 
 
 32. Write the formulas of sodium bromate; calcium hypo-chlorite; 
 platinic antimonate; stannic chromate; potassium borate; lead arsen- 
 ite; manganous carbonate. 
 
 33. Define and illustrate normal, acid, basic, and double salts. 
 
 34. Distinguisb an experimental from a rational formula. 
 
 35. Give the empirical, rational, and graphic formulas of calcium 
 nitrate. Of mercurous phosphate. 
 
 36. Give the formula of silver sulpho-stannate. 
 
 3. 
 
 37. What are amides? Amines? Alkalamides? How are they 
 named? To what type do they belong? 
 
 38. What is a primary amine? A tertiary di-ainide? 
 
 39. Write the formula of sodamine, chloramide, sulphamide, phos- 
 phamic acid. 
 
56 THEORETICAL CHEMISTRY. 
 
 CHAPTER FOURTH. 
 
 VOLUME-RELATIONS OF MOLECULES. 
 
 1. RELATION OF DENSITY TO ATOMIC MASS. 
 
 96. Molecular Volume. By the law of Avogadro, all 
 molecules have the same size ; that is, all molecules when in 
 the gaseous state occupy the same volume. Every molecular 
 formula, therefore, not only expresses the mass of the mole- 
 cule, but also the volume which it occupies. The molecule 
 of hydrogen is taken as the standard of molecular volume ; 
 but, as it is sometimes convenient to speak of atomic volume 
 which, since atoms in general can not exist free, must be 
 a fiction the volume occupied by the atom of hydrogen is 
 taken as unity ; the volume' occupied by the molecule will, 
 therefore, be two. Moreover, as all molecules occupy the 
 same volume, the molecular volume of all substances is as- 
 sumed to be two, also. 
 
 97. Relation of Molecular Mass to Density. Since 
 molecular mass represents the mass of two volumes, and rel- 
 ative density represents the mass of one, the relative density 
 of any homogeneous substance in the state of gas is one half 
 its molecular mass. 
 
 EXAMPLES. Ammonia gas, whose molecular formula is H 3 N, has 
 a molecular mass of 3-)-14 or 17. By the above rule, its calculated 
 relative density is 17-=-2 or 8*5; i. e., it has 8-5 times the mass of hydro- 
 gen. An experiment with the balance shows that the mass of one 
 liter of ammonia gas is 0-7627 grams. As the mass of one liter of 
 hydrogen gas is 0-0896 grams, the relative experimental density of 
 ammonia gas is 0-7627-=-0-0896 or 8-5. 
 
 98. Molecular Mass Fixed by Density. Conversely, 
 knowing the relative density, the molecular mass may be 
 obtained by doubling it. \ 
 
VOLUME -RELATIONS OF MOLECULES. 57 
 
 The analysis of any homogeneous substance gives the ratio 
 of the constituents only, not their absolute masses. On ana- 
 lytical grounds, therefore, several molecular masses, all mul- 
 tiples of the lowest, may be attributed to the body analyzed. 
 By taking the relative density of the substance in the state 
 of vapor, however, and doubling it, the true molecular mass 
 is determined. 
 
 EXAMPLES. The analysis of hydrogen oxide water shows that 
 in 100 parts of it there are 88-89 parts of oxj'gen and 11-11 parts of 
 hydrogen. The ratio of 11-11 : 88-89 is 1 : 8. If the molecule con- 
 tain one part of hydrogen and eight parts of oxygen, its molecular 
 mass will be 1+8 or 9. But it may contain two, three, four or five 
 times this quantity of each constituent, and yet yield the same ana- 
 lytical results. Its molecular mass, so far as analysis goes, may be 9, 
 18, 27, 36, 45, etc. Upon weighing now a liter of water-gas steam: 
 its mass is found to be 0-8047 grams; whence its relative density is 
 0-8047-5-0-0896, or 9, and its molecular mass is 9X2 or 18. Water 
 therefore consists of 2 parts of hydrogen and 16 parts of oxygen in 
 each molecule. 
 
 Again, olefiant gas a compound of carbon and hydrogen affords 
 on analysis 85-71 per cent of carbon and 14-29 per cent of hydrogen, 
 which is the ratio of 6 : 1. There may be then 6 parts of carbon to 
 one of hydrogen in the molecule, in which case the molecular mass 
 of olefiant gas will be 7; or 12 parts of carbon to two of hydrogen, 
 when it will be 14; or 18 to 3, giving 21; or 24 to 4, giving 28; the 
 ratio in all these cases being the same. By experiment the mass of 
 one liter of olefiant gas is 1-252 grams. Its relative density therefore, 
 is 1-252 -j-0-0896, or 14, and its molecular mass 14X2 or 28. Hence 
 one molecule of olefiant gas contains 24 parts of carbon and 4 parts 
 of hydrogen. 
 
 99. Aid in Determining- Atomic Mass. The atomic 
 mass of any simple substance is the smallest mass of it which 
 can enter into the formation of a molecule. By ascertain- 
 ing, therefore, the molecular masses of various compounds 
 of the same element, and by comparing together the masses 
 of this element which they severally contain, it is easy to fix 
 its atomic mass. 
 
58 THEORETICAL CHEMISTRY. 
 
 EXAMPLES. A molecule of water contains 16 parts of oxygen ; a 
 molecule of carbonic gas, 32 parts ; a molecule of sulphuric oxide, 48 
 parts; etc. In no known compound, however, is there less than 16 
 parts of oxygen in a molecule; 16 is therefore the atomic mass of 
 oxygen. 
 
 Again, a molecule of marsh-gas contains 12 parts of carbon, a 
 molecule of olefiant gas 24, a molecule of glycerin 36, a molecule of 
 tartaric acid 48, a molecule of citric acid 72. The smallest of these 
 numbers, 12, is therefore the atomic mass of carbon; and the bodies 
 above mentioned contain in each molecule, one, two, three, four, five, 
 and six atoms of carbon, respectively. 
 
 2. RELATION OF GASEOUS DIFFUSION TO ATOMIC MASS. 
 
 100. Gaseous Diffusion. In 1825, Dobereiuer, having 
 collected some hydrogen gas in a cracked jar, standing over 
 water, noticed that the level of the water within the jar rose 
 one and a half inches in twelve hours ; a result obviously 
 due to the escape of the hydrogen through the crack. Gra- 
 ham found, on repeating the experiment, that as the hydro- 
 gen escaped outward, a portion of air, much less in amount, 
 entered the jar. And on investigation he ascertained that 
 gases, even when separated by porous partitions, pass freely 
 into each other. This mutual passage of one gas into an- 
 other is called diffusion. 
 
 101. Graham's Law of Diffusion. Graham showed 
 experimentally that the rapidity with which different gases 
 diffuse into each other varies for each gas ; and also that 
 this rapidity stands in intimate relation to the relative den- 
 sity of the gas. This relation is expressed in the following 
 law : 
 
 The velocity of the diffusion of any gas is inversely 
 proportional to the square root of its relative density. 
 
 102. Explanation of Diffusion. Physics assumes that 
 all gaseous molecules are in rapid motion in straight lines. 
 Now, as the pressure upon all gaseous volumes is equal 
 
(iASKOm DIFFUSION. 59 
 
 being the atmospheric pressure and as this pressure is ex- 
 actly balanced by the elasticity of the gas due to the direct 
 outward impact of its molecules it follows, from Avogadro's 
 law, that the impact of all gaseous molecules is equal. 
 
 Moreover, iu dynamics, impact is proportional to the 
 product of the mass into the square of the velocity. Since, 
 therefore, molecules differ in mass, it is obvious that the 
 lighter ones must move faster than the more massive ones, 
 to produce the same effect. If one molecule has four times 
 the mass of another, the latter needs to move twice as fast 
 to strike the same effective blow ; since 4 times I 2 is the 
 same as once 2 2 , both being 4. By the supposition, the masses 
 of the molecules are as 4 : 1 ; their velocities therefore must 
 be as 1 : 2. Hence their velocities are inversely as the square 
 roots of their molecular masses ; or, what is the same thing, 
 of their relative densities; which is the law 7 of diffusion, de- 
 duced by Graham from experiment. 
 
 EXAMPLES. The relative density of oxygen being 16, a molecule 
 of oxygen has 16 times the mass of a molecule of hydrogen. The 
 elasticity of both gases under the atmospheric pressure is the same. 
 But, that the impact should be the same, the lighter or hydrogen mol- 
 ecule must move 4 times as fast as the more massive or oxygen mole- 
 cule, since 
 
 OXYGEN. HYDROGEN. 
 
 Mass. Veloc. Mass. Veloc. 
 
 16 x I 2 = 1 X 4 2 
 
 That is, hydrogen molecules should move with four times the velocity 
 of oxygen molecules. 
 
 Using a thin graphite plate as a partition, Graham found experi- 
 mentallv, that, taking air as unity, the ratio of the diffusion of oxygen 
 is to that of hydrogen as 0-95 : 3-83. But 0-95 : 3-83 .: : 1 : 4. As a 
 matter of fact, therefore, hydrogen molecules do move 4 times faster 
 than oxygen molecules. 
 
 1O3. Determination of Molecular Mass by Diffu- 
 sion. If the velocity of diffusion of any gas is equal to the 
 inverse square root of its relative density, then the relative 
 
00 THEOUETK'M. 
 
 density of any gas must be equal to the inverse square of 
 its velocity of diffusion. Or mathematically, calling V the 
 
 velocity of diffusion and D the relative density if V= ~;, _" 
 then D=y^. Of course, by doubling the relative density 
 thus given, the molecular mass is obtained. 
 
 EXAMPLES. By Graham's table of diffusibilities, carbonic gas has 
 a diffusive power of 0-812 as compared with air, or of 0-212 as com- 
 pared with hydrogen. ButD y^; hence D = ..ish' 2 =; 22-22. The 
 
 relative density of carbonic gas being 22-22, its molecular mass must 
 be 22-22X2 or 44-44. Analysis shows it to be 22, 41, 66, 88, etc. Dif- 
 fusion fixes it as the second of these numbers. It was in this way 
 that Soret determined the relative density, and thence the molecular 
 mass, of ozone. 
 
 3. COMBINATION BY VOLUME. 
 
 104. Law of Combination by Volume. The propor- 
 tions in which gaseous volumes enter into combination were 
 first investigated by Gay-Lussac. His law asserts : 
 
 1st. That the ratio in which gases combine by volume 
 is always a simple one ; and 
 
 2d. That the volume of the resulting- gaseous product 
 bears a simple ratio to the volumes of its constituents. 
 
 105. Deduction of this Law. The law of combina- 
 tion by volume, which, in Gay-Lussac's time, was purely ex- 
 perimental, has been recently shown by Clausius to be a very 
 simple deduction from the law of Avogadro. 
 
 According to Avogadro's law, equal volumes of all gases 
 contain the same number of molecules. If, therefore, the 
 number of molecules be in any way diminished, the vol- 
 ume itself will be diminished proportionally. Suppose now, 
 that in the given volume of any gas, each molecule is di- 
 atomic, i. e., contains but two atoms; then, if by any means 
 the molecule can be made tetr-atomic, i. e., four-atomed, 
 the absolute number of atoms remaining the same the nuni- 
 
nij'MK. 61 
 
 ber of molecules will be reduced one half, since each mole- 
 cule contains twice as many atoms. But by this reduction 
 in the number of molecules a corresponding diminution in 
 volume takes place, and the volume of the gas is reduced 
 one half also. 
 
 Again, if the di-atomic molecule become tri-atomic, the 
 number of molecules would be reduced by one third. Hence, 
 the volume originally occupied by these molecules would be 
 reduced in the same ratio. 
 
 1O6. Application of Clausius's Theory. To apply 
 this reasoning to the facts of volume-combinations, let us 
 consider separately the combinations which hydrogen forms 
 with the four valence groups, monads, dyads, triads, and 
 tetrads, supposing their molecules to be all di-atomic. 
 
 FIRST CASE. In the case of monads, one atom combines 
 with one atom of hydrogen ; and since the molecules of both 
 are di-atomic, a molecule will combine with one molecule, 
 and a volume with one volume of hydrogen. All bodies 
 consisting of di-atomic molecules made up of monad atoms, 
 combine, therefore, in equal volumes. 
 
 Further, when the monad atom and the hydrogen-atom 
 combine, they form a di-atomic molecule precisely like a mol- 
 ecule of either of its constituents, except that its atoms are 
 unlike. The two di-atomic simple molecules form two di- 
 atomic compound molecules. Two volumes of simple gases 
 give two volumes of a compound gas. 
 
 Substances of the first class, then, i. e., monads com- 
 bine with each other volume to volume, and yield two vol- 
 umes of the product. 
 
 EXAMPLES. A chlorine atom 01, unites with a single hydrogen 
 atom H, to form HC1, both being monads. As the molecules of both 
 are di-atomic, these sabstances unite molecule to molecule, or volume 
 to volume. On mixing the volume of chlorine with the volume of 
 hydrogen and exposing them to sunlight, they unite to form hydro- 
 gen chloride gas, each molecule of which is di-atomic, containing one 
 
62 
 
 THEORE TIC A L CHEMIS Til 1 '. 
 
 chlorine atom and one hydrogen atom. The number of molecules 
 after the union being the same as before, the volumes are unaffected. 
 To represent it molecularly: 
 
 H Cl H-C1 
 
 and | give 
 
 A 
 
 Or in volumes, 
 
 and 
 
 Cl., 
 
 H Cl 
 
 yield 
 
 SECOND CASE. If the atom taken be a dyad, then it will 
 unite with tvvo atoms of hydrogen; or one molecule will 
 unite with two molecules, or one volume with two volumes. 
 Dyads, therefore, combine with monads in the ratio of one 
 volume to two volumes. 
 
 Moreover, the molecule which results from the union of 
 one dyad atom with two monad atoms will be tri-atomic. 
 As before union they were di-atomic, three molecules then, 
 make but two now. The total number of molecules is one 
 third less than before ; and, of course, the volume is dimin- 
 ished in the same ratio. Two volumes of one gas and one 
 volume of the other give three volumes ; after combination, 
 but two volumes remain. So that three volumes of simple 
 gases give two volumes of a compound gas, a condensation 
 of three volumes to two taking place during union. 
 
 Substances of the second class, then, i. e. dyads com- 
 bine with monads in the ratio of one volume to two, and 
 yield two volumes of the product. 
 
 EXAMPLES. The atom of oxygen is bivalent; its molecule is di- 
 atomic. Assuming a fixed number of molecules in the given volume, 
 say 100, then the 200 atoms in these 100 molecules will unite with 400 
 atoms, or 200 molecules of hydrogen, producing 600 atoms. In other 
 words, one volume of oxygen will combine with two volumes of hy- 
 drogen. Now the water-molecule which results contains 3 atoms, 2 
 
COMBINATION BY rOLUMK. 63 
 
 of them hydrogen and one oxygen ; the GOO atoms of these substances 
 above mentioned will therefore give 200 water-molecules, which, by 
 the assumption above, occupy two volumes. Hence one volume of 
 oxygen and two volumes of hydrogen yield two volumes of water-gas. 
 
 THIRD CASE. One triad atom unites with three monad 
 atoms, one molecule with three molecules, one volume with 
 three volumes. The original simple molecules contain two 
 atoms, the resulting compound molecule, four; the number 
 of molecules, and hence the corresponding volume, is there- 
 fore reduced one half, four volumes being condensed into 
 two. 
 
 Substances of the third class, L e., triads, unite with mon- 
 ads in the ratio of one volume to three, and yield two vol- 
 umes of the product. 
 
 EXAMPLES. One atom of nitrogen unites with three atoms of hy- 
 drogen to form ammonia. One molecule of nitrogen and tlnee mole- 
 cules of hydrogen give two molecules of ammonia. 
 
 N HHH HHH N 
 
 HI and | | | give * , ' s 
 
 N HHH N HHH 
 
 Four di-atomic give two tetr-atomic molecules. Hence one volume 
 of nitrogen and three volumes of hydrogen form two volumes of am- 
 monia gas. 
 
 FOURTH CASE. Lastly, one tetrad atom unites with four 
 monad atoms, one tetrad molecule with four monad mole- 
 cules, one volume of any tetrad with four volumes of any 
 monad. The resulting molecule contains five atoms, and 
 hence the five original volumes are condensed to two. 
 
 Substances of the fourth class, i. e., tetrads, unite with 
 monads in the ratio of one volume to four, and yield two 
 volumes of the product. 
 
 EXAMPLES. One atom of carbon and four atoms of hydrogen 
 unite to form marsh gas. That is, C. 2 and (H 2 ) 4 give (H 4 C) 2 ; or five 
 di-atomic give two pent-atomic molecules. Hence one volume of 
 carbon gas and four volumes of hydrogen form two volumes of marsh 
 gas. 
 
64 
 
 THEORE TIC A L CTIEMISTR F. 
 
 1O7. Recapitulation of Volume-combinations. The 
 
 various ratios in which combinations by volume take place 
 according to Gay-Lussac's law, may be thus represented : 
 
X fiT VOLUME. 65 
 
 These results correspond precisely with those required by 
 the law of combination by valence, which, for the union of 
 di-atomic molecules, gives the following four cases : 
 
 1 molecule and 1 molecule give 2 molecules. 
 
 1 molecule and 2 molecules give 2 molecules. 
 
 1 molecule and 3 molecules give 2 molecules. 
 
 1 molecule and 4 molecules give 2 molecules. 
 
 Or, written out fully to express the atomic character of 
 
 the molecule : 
 
 Molecules Di-atomic. 
 
 1 monad molecule and 1 monad molecule give 2 di-atomic molecules. 
 1 dyad molecule and 2 monad molecules give 2 tri-atomic molecules. 
 1 triad molecule and 3 monad molecules give 2 tetr-atomic molecules. 
 1 tetrad molecule and 4 monad molecules give 2 pent-atomic molecules. 
 
 1O8. Cases where the Elemental Molecules are not 
 Di-atomic. The cases of this are practically but two in 
 number; one where the molecule is mon-atomic, the other 
 where it is tetr-atomic. 
 
 FIRST CASE. All known mon-atomic molecules are dyads. 
 Hence the atomic combination with monad atoms would be : 
 
 1 atom and 2 atoms give 3 atoms. 
 And by molecules : 
 
 1 molecule and 1 molecule give 1 molecule. 
 Or by volumes : 
 
 1 volume and 1 volume give 1 volume. 
 
 That is, mon-atomic dyad molecules combine with di- 
 atomic monad molecules in the ratio of equal volumes, yield- 
 ing one volume of the product. 
 
 EXAMPLES. The dyads zinc and mercury have mon-atomic mole- 
 cules. One atom of zinc unites with two atoms of chlorine to form 
 zinc chloride; that is, one mon-atomic zinc molecule unites with one 
 di-atomic molecule of chlorine, to form one tri-atomic molecule of 
 zinc chloride. As all molecules have the same size, this is equivalent 
 to saying that one volume of zinc-vapor and one volume of chlorine 
 gas combine to give one volume of zinc chloride vapor, a condensa- 
 tion of one half. 
 
66 
 
 THEORETICAL CHEMISTRY. 
 
 SECOND CASE. All known tetr-atomic molecules are tri- 
 ads. The atomic combination with monads would therefore 
 
 be: 
 
 1 atom and 3 atoms give 4 atoms. 
 
 And by molecules : 
 
 1 tetr-atomic molecule and 6 di-atomic molecules give 4 tetr-atomic 
 molecules. 
 
 Or by volumes: 
 
 1 volume and 6 volumes yield 4 volumes. 
 
 That is, tetr-atomic triad molecules combine with di-atomic 
 monad molecules in the ratio of one volume to six volumes, 
 yielding four volumes of the product, a condensation of seven 
 volumes to four. 
 
 EXAMPLES. Phosphorus is a triad, having a tetr-atomic molecule. 
 When it unites with chlorine we have atomically, P and C1 3 give 
 PCI.,; molecularly, P^ and (C1 2 ) 6 give (PC1 3 ) 4 , or by volume: 
 
 Cl, 
 
 OL 
 
 PCI, 
 
 PC1 3 
 
 1O9. Tri-atomic and Hex-atomic Molecules. The 
 
 law of combination by volume for tri-atomic and hex-atomic 
 molecules, should any substances be found to combine in 
 this way, can easily be deduced from the principles already 
 given. 
 
 The entire foregoing chapter furnishes an excellent illus- 
 tration of the intimate mutual relations between Physics and 
 Chemistry. Assuming either the physical or the chemical 
 data at pleasure, the other can be deduced from it. 
 
EXERCISES. 67 
 
 EXERCISES. 
 * 
 
 1. What is molecular volume, and how is it expressed? 
 
 2. The mass of one liter of carbonic gas (CO 2 ) is 1-97 grams; what 
 is" its calculated, and what its experimental, relative density? 
 
 3. Of what assistance is relative density in fixing a molecular 
 mass ? 
 
 4. Iron chloride contains 34-46 per cent of iron, and 65-54 per cent 
 of chlorine ; its relative density is 81 ; what is its molecular mass ? 
 How much iron and how much chlorine is there in each molecule? 
 
 5. How is an atomic mass determined by relative density? 
 
 6. Hydrogen bromide contains 1-24 per cent of hydrogen, and 98*76 
 of bromine ; its relative density is 40-38. Mercury bromide contains 
 56-56 per cent of mercury and 44-44 of bromine; its relative density 
 is 179-6. Boron bromide contains 4-38 per cent of boron, 95-62 of bro- 
 mine; its relative density is 125-12. Silicon bromide contains 8-04 
 per cent of silicon and 91-96 of bromine; its relative density is 173-5. 
 What is the atomic mass of bromine ? 
 
 7. What is gaseous diffusion? Give Graham's law. 
 
 8. How is the fact of diffusion explained? Illustrate. 
 
 9. How is molecular mass fixed by diffusion? 
 
 10. Marsh-gas has a diffusibility of 0.35, that of hydrogen being 1 ; 
 what is its molecular mass ? 
 
 3. 
 
 11. Give Gay-Lussac's law of combination by volume. 
 
 12. How may this be derived from the law of Avogadro? 
 
 13. How do monads combine with hydrogen by volume? Dyads? 
 Triads? Tetrads? 
 
 14. In what proportion by volume, do tetrad sulphur and oxygen 
 unite? What volume has the product? 
 
 15. Do the volume-combinations as deduced from the law of valence 
 agree with those observed by Gay-Lussac ? 
 
 16. How do merourv and arsenic unite bv volume? 
 
68 THEORETICAL CEEM1STKT. 
 
 CHAPTER FIFTH. 
 
 CHEMICAL REACTIONS. STOICHIOMETRY. 
 1. CHEMICAL EQUATIONS. 
 
 110. Molecular Stability. All material molecules are 
 more or less liable to chemical change. The atoms within 
 them may be altered in kind, in number or in relative posi- 
 tion, by various external influences. A molecule is the more 
 stable in proportion as it resists this tendency to change. 
 
 111. Chemical Reactions. Any mutual action which 
 takes place between the atoms composing a molecule is called 
 a Chemical Re-action. Both of the substances acting are 
 called Re-agents. 
 
 EXAMPLES. "When a candle burns, the wax and the oxygen of 
 the air act mutually upon each other, yielding gaseous products en- 
 tirely unlike the wax or the oxygen. When gunpowder explodes the 
 various molecules which it contains react upon each other, and a new 
 set of products is the result. When the components of a Seidlitz 
 powder are mixed together and moistened, they react upon each other, 
 producing the well-known effervesce nee. 
 
 112. Reactions Always Molecular. Chemical reac- 
 tions always take place within the molecule. When, there- 
 fore, two substances react upon each other, the changes which 
 result may be viewed as taking place between single mole- 
 cules of each. Moreover, since all molecules in homogene- 
 ous matter are alike, and what is true of one molecule is 
 true of any mass of them, it follows that a molecular change 
 represents accurately a mass-change. 
 
 113. Reactions Expressed by Formulas. Every for- 
 mula in Chemistry represents a molecule ; and as all reac- 
 tions are viewed as taking place between molecules, these 
 
CHKMK'A L !<:< f . / T/OXS. 69 
 
 reactions may be represented by the use of molecular for- 
 mulas. 
 
 114. Chemical Equations. Chemical reactions are 
 usually represented in the form of equations ; the substances 
 entering into the reaction called factors constituting the 
 h'rst member, and those issuing from it called products 
 the second. 
 
 AVhen two molecules act upon each other, the equation 
 representing the reaction may be written by the following 
 rule : 
 
 Place the formulas of the factors connected by the 
 sign plus as the first member of the equation, and the 
 formulas of the products also connected by the sign 
 plus as the second. 
 
 EXAMPLES. The reaction of the two molecules AB and CD would 
 be represented thus : 
 
 AB -f CD = AD -f CB. 
 
 Sometimes, though rarely, the minus sign is used in an equation, thus: 
 ABC B = AC. 
 
 115. Masses of the Factors and the Products Equal. 
 
 As each formula represents a definite mass of matter the 
 molecular mass it follows that the masses of matter taking 
 part in a chemical change are perfectly definite. And, more- 
 over, since the atoms are the same after the reaction as be- 
 fore it being only differently associated it also follows that 
 no loss of matter can be the result of any chemical 
 reaction. The sum of the molecular masses of the prod- 
 ucts must, therefore, always equal the sum of the molecular 
 masses of the factors. 
 
 116. Meaning' of the Signs. The equality sign indi- 
 cates the equality in mass of both members of the equation. 
 The plus sign means simply "and," and signifies that the 
 molecules thus united are mixed together. The minus sign 
 means " from," and indicates the removal of a simpler group 
 of atoms from a more complex one. 
 
 
 
70 THEORETICAL CHEMISTRY. 
 
 117. Construction of Equations. Ordinarily the rule 
 above given is quite sufficient for the construction of an equa- 
 tion, the number of molecules involved being determinable 
 by inspection. In some cases, however, where the reaction 
 is a complex one, it is convenient to be able to calculate 
 the number of molecules. This may readily be done by the 
 use of the algebraic method of simultaneous linear equa- 
 tions, which may be illustrated as follows : * Suppose it be 
 required to write the reaction where tin acts on nitric acid, 
 the products being stannic oxide, nitrogen di- oxide, and 
 water. Using letters to indicate the number of molecules, 
 we have the equation : 
 
 Sn a + (HN0 3 ) 6 = (Sn0 2 ) w + (N 2 O 2 )*+ (H 2 O), 
 Since the number of atoms of each element must be the 
 same on the two sides of the equation, we have for the tin 
 a=w; for the hydrogen, b=2y; for the nitrogen, b=2x; and 
 for the oxygen, 3b=2w+2x+y. Assuming 6=1, and solv- 
 ing these equations, we find a=f, #=J, y=\ and w=f ; or, 
 clearing of fractions, a=3, 6=4, w=3, x=2 and ?/=2. Sub- 
 stituting these numerical values now for the literal ones 
 above given, we have the correct equation : 
 
 Sn 3 + (HN0 3 ) 4 = (Sn0 2 ) 3 + (N,O f ), 
 
 118. Classification of Reactions. Chemical reactions 
 are usually divided into three classes, as follows : 
 
 1st. Analytical reactions ; which represent the separa- 
 tion of a complex molecule into simpler ones. 
 
 2d. Synthetical reactions ; which represent the union of 
 two or more simple molecules, to form a more complex one. 
 
 3d. Metathetical reactions ; which represent a transpo- 
 sition or exchange of atoms between molecules. 
 
 EXAMPLES. Analytical reactions may be represented by the gen- 
 eral equation: AB = A -j- B. 
 
 *As suggested by C. E. Munroe. 
 
\li( 'A L A'V HA T10NS. 1 1 
 
 Or, to take an actual example, 
 
 (NH 4 )N0 3 N 2 + ' (H 2 0) 2 
 
 Ammonium nitrate. Nitrogen oxide. Water. 
 
 which is read thus: One molecule of ammonium nitrate yields one 
 molecule of nitrogen oxide and two molecules of water. 
 
 Synthetical reactions are the reverse of analytical ; they are repre- 
 sented by the general equation: 
 
 A + B = AB. 
 Or, as an actual example, 
 
 CaO + SO, CaS0 4 
 
 Calcium oxide. Sulphuric oxide. Calcium sulphate. 
 
 read thus: One molecule of calcium oxide and one molecule of sul- 
 phuric oxide yield one molecule of calcium sulphate. 
 
 Metathetical reactions from perori&tyu, to displace or transpose 
 are represented by the general formula: 
 
 AB + CD = AD + . 
 
 Or, practically, by the equation: 
 
 Ag(N0 3 ) + NaCl AgCl + Na(NO 3 ) 
 
 Silver nitrate. Sodium chloride. Silver chloride. Sodium nitrate. 
 
 A molecule of silver nitrate reacts upon a molecule of sodium chlo- 
 
 ride, to produce one molecule of silver chloride and one of sodium 
 
 nitrate; an exchange taking place between positive atoms. 
 
 In all the above examples, each letter in the general equa- 
 tions, and each formula in the special, represents an entire 
 molecule. Less than an entire molecule can not enter into, 
 or issue from, any chemical reaction. 
 
 119. Conditions Favoring- Chemical Change. Fa- 
 cility of chemical change depends, to a large extent, upon 
 the ease with which the atoms of any molecule may be re- 
 arranged. It is found, for example, that chemical changes 
 take place very readily when the substances acting are in 
 the liquid or gaseous state. Hence fusion, or solution, by 
 which bodies are liquefied, or vaporization, by which they 
 are converted into gases, facilitate chemical action. 
 
 120. Berthollet's Laws. Those conditions of chemical 
 change which depend upon solubility are stated in the fol- 
 lowing general law, first established by Berthollet : 
 
72 THEORETICAL CHEMISTRY. 
 
 Whenever, on mixing two substances in solution, a 
 compound can be formed by a re-arrangement of their 
 atoms, which is insoluble in the menstruum employed, 
 such compound will be formed, and will appear as a 
 precipitate. 
 
 EXAMPLES. If AB be dissolved in water, and CD, also dissolved 
 in water, be added to it, then any re-arrangement must obviously pro- 
 duce AD and CB. AB and CD are soluble in water; but AD, or CB, 
 or both, may be insoluble. In either case, the new and insoluble com- 
 pound will separate from the solution in the solid form, the liquid 
 losing its clearness and becoming turbid. 
 
 The solid substance which thus separates from a solution 
 is called a precipitate. Any substance which will produce 
 a precipitate when added to a solution of any other substance 
 is called a precipitant. The process of producing a precipi- 
 tate is called precipitation. 
 
 121. Precipitation both Chemical and Physical. 
 The first step in precipitation is the re-arrangement of the 
 atoms ; this is a chemical result. The second step is the sep- 
 aration of the insoluble product ; this depends on the adhe- 
 sion between the liquid molecules and those of the solid, and 
 hence is a physical result. No conclusion can be drawn, 
 therefore, as to the intensity of the chemism, from the mere 
 fact of precipitation. 
 
 122. Law of Gaseous Change. The second law of 
 BerthoTlet holds when the product of the reaction, instead 
 of being a solid and insoluble, is a gas. It may thus be 
 stated : 
 
 Whenever, by the action of bodies upon each other, 
 any substance, volatile at the temperature of the ex- 
 periment, can be formed by a re-arrangement of the 
 atoms, such re -arrangement will take place, and such 
 substance will be evolved as a gas or vapor. 
 
 EXAMPLES. Theoretically, as above, AB and CD, by rearrange- 
 ment, give AD and CB. If AD or CB is volatile at the temperature 
 
CHEMICAL EQUATIONS. 73 
 
 of the experiment, it will separate from the solution in the gaseous 
 form. Or, actually, let Na 2 (CO 3 ) and H 2 (S0 4 ) be mixed together in 
 solution. By the chemical re-arrangement, Na. 2 (SO 4 ) and H 2 (CO 3 ) 
 will be produced. As, however, the body H 2 (CO 3 ) can not exist at 
 ordinary temperatures, it separates into H 2 O and C0 2 ; which latter 
 substance, being a gas, escapes from the solution. 
 
 Again, on mixing together potassium nitrate K(NO 3 ) and hydro- 
 gen sulphate H 2 (j3O 4 ), there will result by the re-arrangement, the 
 bodies HK(SO 4 ) and H(NO 3 ) hydro-potassium sulphate, and hydro- 
 gen nitrate ; this being the chemical part of the change. If now heat 
 be applied to the mixture, the nitric^ acid, being volatile, will escape 
 as a vapor. 
 
 The rapid escape of a gas from a liquid, such as is noticed 
 in mixing Seidlitz powders, for example, is called efferves- 
 cence. 
 
 123. Prediction of Results. Whether a chemical 
 change will actually take place or not may, in many cases, 
 be predicted by means of these laws, if the properties of 
 the products be known. i3y the use of a table given in 
 the appendix showing the solubility of various substances, 
 all cases under the first law may be predicted ; and by hav- 
 ing some familiarity with the volatility of various bodies, 
 cases may be predicted under the second law. 
 
 EXAMPLES. If calcium chloride and sodium carbonate be mixed 
 in solution, will there bj a precipitate? The reaction is thus written: 
 
 CaCl 2 + Na 2 (C0 3 ) = Ca(CO. { ) + (NaCl) 2 
 
 Referring to the table, it will be seen that Ca(C0 3 ) calcium carbonate, 
 is insoluble. It will therefore separate in the solid form and fall as a 
 precipitate. 
 
 If, however, an acid be at the same time formed, and the solid sub- 
 stance be soluble in acids, there will be no precipitate. If hydrogen 
 sulphide and ferrous sulphate be mixed in solution, the reaction would 
 be represented by the equation: 
 
 H 2 S + Fe(S0 4 ) = FeS -f H 2 (SO 4 ) 
 
 By the table, ferrous sulphide (FeS), though insoluble in water, is 
 soluble in acids. Were water alone present, this substance would be 
 
74 THEORETICAL CHEMISTRY. 
 
 precipitated; but as sulphuric acid (H 2 (SO 4 )) is in the solution, being 
 set free in the reaction, there will be no precipitate. 
 
 Again, if ammonium sulphate and calcium carbonate be heated 
 together, will there be a change? The only possible exchange is the 
 following: 
 
 (NH 4 ) 2 (S0 4 ) + Ca(CO s ) = (NH 4 ) 2 (CO 3 ) + Ca(SO 4 ) 
 Ammonium Calcium Ammonium Calcium, 
 
 sulphate. carbonate. carbonate. sulphate. 
 
 But ammonium carbonate is volatile; it will therefore escape in vapor, 
 leaving the calcium sulphate behind. 
 
 124. Modes of Chemical .Action. Chemical changes 
 in matter may take place in five different ways, namely : 
 
 1. By the direct union of simpler molecules to form a more 
 complex one. 
 
 2. By the separation of a complex molecule into simpler 
 ones. 
 
 3. By the substitution in a molecule of one atom or group 
 of atoms for another or for several others. 
 
 4. By the mutual exchange of atoms between molecules. 
 
 5. By the re-arrangement of the atoms within a single 
 molecule. 
 
 EXAMPLES. 1st. All synthetical reactions belong to the first class 
 of chemk.il changes; as: 
 
 Zn + C1 2 = ZnCl 2 
 Zinc. Chlorine. Zinc chloride. 
 
 2d. All analytical reactions belong to the second class; as: 
 
 H 2 S0 4 = H 2 4- S0 3 
 Hydrogen sulphate. Water. Sulphuric oxide. 
 
 3d. Substitution reactions; as: 
 
 C 2 H 6 -f C1 2 = C 2 H 5 C1 + HC1 
 Ethyl hydride. Chlorine. Ethyl chloride. Hydrogen chloride. 
 4th. All metathetical reactions represent the fourth class; as: 
 
 CaCl 2 + K 2 (C 2 4 ) = Ca(C 2 4 ) + (KC1) 2 
 Calcium chloride. Potassium oxalate. Calcium oxalate. Potassium chloride. 
 5th. The conversion of ammonium cyanate into urea: 
 
 (NH 4 )(CNO) = (CO)(H 2 N) 2 
 Ammonium cyanate. Urea. 
 
CHEMICAL EQUATIONS. 75 
 
 125. Chemical Relations of Work and Energy. 
 
 In studying the energy-relations of matter, it is often con- 
 venient to consider the bodies concerned as forming mutu- 
 ally acting systems, whose parts at any instant are definitely 
 arranged with reference to one another. Such a system pos- 
 sesses energy, in part potential, due to the relative position 
 of its parts, in part kinetic, due to their motion. The action 
 of one such system upon another consists simply in the trans- 
 ference of this energy from one to the other ; in doing which 
 the one system is said to exert force upon the other. It is 
 evident, however, that the amount of energy gained by the 
 one system is exactly equal to that which is lost by the other. 
 So that if we include both systems in a single larger system, 
 we see that the total energy of this larger system remains 
 unchanged. Hence the total energy of a material .system 
 can not be changed in amount by any action going on within 
 the system ; although it may be converted into other forms. 
 This is the principle of the Conservation of Energy. 
 
 If an agent external to the system act upon it, however, 
 its action may be either to increase or to diminish the total 
 energy of the system. Whenever work is done upon a sys- 
 tem, its energy is increased ; arid w/ienever the system itself 
 does work upon other systems, its energy is decreased. The 
 amount of energy which is stored up in a system is always 
 exactly equal to the amount of work w r hich is done upon it. 
 While we can not measure the total energy of a system, we 
 can measure very accurately the changes in energy which it 
 undergoes. If we suppose a definite system to pass from 
 one definite state to another, the energy lost or gained iu 
 the process is evidently the difference between the energy 
 of the system in its initial and final states. Heat is a form 
 of energy ; so that, if we may assume that the energy lost 
 or gained is heat-energy, a measurement of the heat gained 
 or lost by the system will give us the increase or decrease of 
 energy which the system undergoes. If a system A whose 
 
76 THEORETICAL CHEMTSTHT. 
 
 potential energy is E A passes to a system B, whose potential 
 energy is E 15 , less than E A , then the loss of energy in the 
 process due to a change in the position of the parts where- 
 by the stress between them is diminished will evidently be 
 E A E I5 . This energy by supposition appears as heat; so that 
 we may write E A E B =H. To return the system B to its 
 original state A, on the other hand, requires energy to be 
 supplied; whence the equation E A =E B -fH. 
 
 126. Tliermo-chemical Laws. The fundamental laws 
 of therm o-chemistry are three in number (Berthelot) : 
 
 I. The amount of heat set free in any chemical reaction 
 whatever is a measure of the total work, both physical and 
 chemical, accomplished in the reaction. 
 
 II. Whenever a system of bodies undergoes physical or 
 chemical changes capable of bringing it to a new state with- 
 out producing any mechanical effect exterior to the system, 
 the amount of heat set free or absorbed in these changes de- 
 pends only on the initial and final states of the system, and 
 is independent of the nature or order of the intermediate 
 states. 
 
 III. Every chemical change which is effected in a system 
 without the aid of outside energy, tends to the production 
 of that body or system of bodies the formation of which 
 evolves the maximum heat. 
 
 EXAMPLES. In thermo-chemical equations the grarn is taken as 
 the unit of atomic mass, II representing one gram of hydrogen and 
 O sixteen grams of oxygen; so that, calling a heat-unit the amount 
 of heat necessary to raise the temperature of one gram of water one 
 degree (i. e., a water-gram degree), we may write the synthetical reac- 
 tion for the production of water-vapor at 136-5, as follows: 
 (H 2 ) 2 -f-O 2 (H 2 O) 2 -f 114,320 water-gram degrees; 
 
 and this by the first law measures the total work accomplished in the 
 reaction. Again, when stannous oxide SnO is formed by the union 
 of tin and oxygen, 73,800 heat-units are evolved; but if the resulting 
 product is stannic oxide SnO 2 , 145,400 units are set free. Hence by 
 the third law the latter substance is always formed, in case the oxygen 
 
CHEMICAL EQUATIOXS. 77 
 
 is present in excess. When one gram of hydrogen unites with eight 
 grains of oxygen to form water (liquid), 34,180 heat-units are evolved; 
 while if the higher oxide H. 2 O 2 be formed, one gram of hydrogen 
 evolves only 23,500 units of heat. In this ease therefore, even in 
 presence of an excess of oxygen, it is the lower oxide and not the 
 higher which will be formed, according to the third law. 
 
 Moreover it will be observed that hydrogen peroxide H 2 O 2 can not 
 be formed from hydrogen oxide H 2 O without the absorption of energy 
 from some source outside the system itself. The equation is: 
 (H 2 0) 2 +O 2 =(H 2 O 2 ) 2 44,000 water-gram degrees. 
 Reactions are classified thermically by Berthelot as exothermic and 
 endothermic, according as heat is evolved or absorbed during their 
 progress. Thus the reaction between hydrogen and chlorine evolves 
 heat, and is therefore an exothermic reaction : 
 
 H 2 +C1 2 =(HC1) 2 -|-44,000 water-gram degrees. 
 
 While when hydrogen combines with iodine vapor heat is absorbed 
 and the reaction is endothermic : 
 
 H 2 -f-I 2 :={HI) 2 3,060 water-gram degrees. 
 
 In accordance with the law that the tendency of the energy of a sys- 
 tem is always toward a minimum, it is found that substances like 
 hydrogen iodide, hydrogen peroxide, cyanogen, acetylene, nitrogen 
 chloride, and the oxides of nitrogen and chlorine, all of which are 
 formed from their constituents with absorption of heat by endother- 
 mic reactions are more or less unstable; being either spontaneously 
 decomposable and even explosive, like nitrogen chloride and the chlo- 
 rine oxides, or readily undergoing changes by slight external causes; 
 but in all cases evolving heat by their decomposition. Carbon di-sul- 
 phide, for example, is an endothermic compound; and Thorpe has re- 
 cently shown that the shock of mercuric fulminate exploded in its 
 vapor decomposes it, depositing both carbon and sulphur. While, 
 therefore, the formation of an endothermic substance can not take 
 place without the aid of outside energy, so, on the other hand, the 
 decomposition of an exothermic substance can not occur without this 
 aid. An exothermic compound is therefore stable. 
 
 The third law teaches us further that if a substance A, 
 in uniting with a given metal, produces more heat than is 
 evolved when B unites with the same metal, A will displace 
 B from the combination. Thus chlorine evolves more heat 
 
78 THEORETICAL CHEMISTRY. 
 
 in combining with the metals than either bromine or iodine 
 does. Hence it can displace bromine and iodine from their 
 metallic compounds. In general, whenever one metal dis- 
 places another from its state of combination, it does so be- 
 cause energy tends to a minimum, and the production of the 
 new compound is attended with an increased evolution of 
 heat. 
 
 127. Intensity of Chemical Action. Helmholtz re- 
 gards each atom of matter as charged with a definite quan- 
 tity of electricity, these charges being proportional to the 
 valence of the atoms. Thus all univalent atoms have unit 
 charge, all bivalent atoms a charge of two units, all trivalent 
 atoms a charge of three units, and so on. Moreover, he con- 
 ceives, 1st, that the same atom in different compounds can 
 be charged with units of either positive or of negative elec- 
 tricity; sulphur, for example, being in hydrogen sulphide a 
 negative substance, and in sulphurous oxide a positive one. 
 And 2d, that their electrical charges are held more strongly 
 by some atoms than by others ; an atom of zinc, for exam- 
 ple, holding its positive charge more strongly than an atom 
 of copper does its negative one. Further, an electrically 
 neutral molecule, whether simple or compound, will have 
 each unit of positive electricity on one of its atoms neutral- 
 ized by an equal unit of negative electricity on another 
 atom. Since a gas set free by electrolysis is neutral, it fol- 
 lows that one atom positively charged combines with another 
 negatively charged, even when, as in tl\e case of hydrogen, for 
 example, these atoms are alike ; thus agreeing with the infer- 
 ence from the law of Avogadro that a molecule of hydrogen 
 is really composed of two atoms. Again, any atom or group 
 of atoms which can be substituted for another must have an 
 equal electrical charge. And, since every equivalent mass 
 has unit charge, the number of unit charges will be equal 
 to the number of equivalent masses in the atomic mass ; i.e., 
 will be the valence of the atom. 
 
STOICHTOMETRICAL CALCULATIONS. 79 
 
 % 
 
 As to the magnitude of these atomic charges, Helmholtz 
 calculates that they must be enormous. ' ' The electricity of 
 one milligram of water," he says, " separated and communi- 
 cated to two balls a kilometer distant, would produce an 
 attraction between them equal to the weight of 26,800 kilo- 
 grams." Or, comparing the electrical attraction between two 
 quantities of oxygen and hydrogen with their gravitational 
 attraction, he finds the electrical force to be 71,000 billion 
 times greater than the gravitational force. 
 
 Faraday long ago expressed his conviction that the forces 
 termed chemical affinity and electricity are one and the same. 
 And now Helmholtz, having proved by experiment that in 
 the phenomena of electrolysis no other force acts but the 
 mutual attractions of the atomic electric charges, comes to 
 the equivalent conclusion "that the very mightiest among 
 the chemical forces are of electric origin." 
 
 2. STOICHIOMETRICAL CALCULATIONS. 
 
 ?28. Definition. Stoichiometry is that department of 
 Chemistry which considers the numerical relations of atoms. 
 All calculations, therefore, which can be made from the 
 atomic masses and volumes are stoichiometrical calculations. 
 
 129. Calculations Founded on Mass. Every atom 
 has its own mass, called the atomic mass. The atomic mass 
 is the smallest mass of any simple or elementary substance 
 referred to the atom of hydrogen as unity which takes 
 part in any chemical change. 
 
 A molecule being built up of atoms, a molecular mass is 
 the sum of the atomic masses of which it is composed. It 
 is also equal to twice the mass of a given volume of a sub- 
 stance in the state of vapor, compared with the same volume 
 of hydrogen. 
 
 If the substance be not volatile and can not be weighed in 
 the state of gas, its molecular mass is that mass of it, in its 
 
80 THEORETICAL CHEMISTRY. 
 
 'to- 
 solid condition, which has the same specific heat as fourteen 
 units of mass of lithium at the same temperature. 
 
 13O. Mass Concerned in Chemical Changes. Since 
 every chemical change is simply an alteration in the position 
 and association of atoms, every chemical equation which rep- 
 resents such a change, represents it as taking place between 
 definite quantities of matter. An equation expresses not 
 only the fact of chemical reaction between two bodies, but 
 also indicates the quantities of matter concerned in it. 
 
 EXAMPLES. S stands for one atom of sulphur, with an atomic 
 mass of 32. O 3 represents three atoms, or (16x3) 48 parts of oxygen. 
 SO 3 expresses the fact that one atom of sulphur (32) and three atoms 
 of oxygen (48) have united to form a molecule of sulphuric oxide, 
 with a molecular mass of (48+32) 80. So Ca(CO 8 ) represents a mol- 
 
 Ca C O, 
 ecule of calcium carbonate, with a molecular mass of 40-{-12 + (]6x3) 
 
 K N O 3 
 =100. The molecular mass of K(NO 3 ) is 39+14+48 101. 
 
 So the equation 
 
 Pb"(NO 3 ) 2 +Na 2 (SO 4 )=Pb"(S0 4 )4-(NaNO. { ) 2 
 
 one molecule of lead nitrate and one of sodium sulphate, yield one 
 molecule of lead sulphate and two of sodium nitrate may be read 
 by mass thus: 
 
 207 f (14+48)2 + (23X2)f32f&4 = 207+ (32 1 64) + (23+14+48)2 
 Pb"(N0 3 ) 2 + Na. 2 (S0 4 ) = Pb"(S0 4 ) + (NaN0 3 ), 
 
 331 -{- 142 303 + 170 
 
 Three hundred and thirty-one parts of lead nitrate and one hun- 
 dred and forty-two parts of sodium sulphate yield three hundred and 
 three parts of lead sulphate and one hundred and seventy parts of 
 sodium nitrate. 
 
 (For convenience of calculation in the examples and exercises whole 
 numbers will generally be taken to represent the atomic and molecu- 
 lar masses.) 
 
 131. Calculation of Percentage Composition. Know- 
 ing the molecular mass of any substance, the number of atoms 
 which it contains, and the atomic mass of each, it is easy to 
 calculate its percentage composition ; i. e. , its composition in 
 
ST01CHIOMKTIUCAI. CALC I LATWXS. 81 
 
 100 parts the form in which the results of analysis are usu- 
 ally given. 
 
 Representing the molecular mass by 222, the atomic mass 
 of any constituent by a, the number of atoms of that con- 
 stituent by 22, and its percentage amount by jf, then we have 
 evidently the proportion : 
 
 222 : an : : 100 : ;x; 
 whence the formula : 
 
 22 x 100 
 
 x= ~vr w 
 
 To find, therefore, the percentage amount of any constit- 
 uent in a molecule, we have the following rule : 
 
 Multiply the atomic mass by the number of atoms 
 and this product by 1OO. Divide the final product by 
 the molecular mass, and the quotient will be the per- 
 centage amount of that constituent. 
 
 By repeating this process for each atomic constituent, the 
 percentage composition of the molecule may be obtained. 
 
 EXAMPLES. What is the percentage composition of calcium sul- 
 phate, Ca(SO 4 ) ? 
 
 By the formula, the molecule contains of 
 
 Calcium, one atom (at. ms. 40) ...... 40 
 
 Sulphur, one atom (at. ms. 32) ...... 32 
 
 Oxygen, four atoms (at. ms. 16) ..... 64 
 
 Molecular mass of calcium sulphate, 136 
 Substituting in the percentage formula, the quantity of 
 
 Calcium in 100 parts is _ 2 9-41 
 
 136 
 
 32X100 
 
 Sulphur -= 23-53 
 
 136 
 
 Oxygen " << " _ 4 7<M 
 
 136 
 
 100-00 
 
82 THEOliKTK 'A L ( 'HKM1HTH Y. 
 
 132. Other Problems by this Formula. In the for- 
 mula given above (1), the four quantities a,, 22, 222, and x 
 are employed. Any three of them being known, of course 
 the fourth can be found. There are therefore three more 
 cases to be here considered. 
 
 SECOND CASE. Having the percentage amount of any 
 constituent, its atomic mass, and the molecular mass of the 
 compound given, to find the number of atoms of that con- 
 stituent in the molecule. 
 
 By transposition, formula (1) gives : 
 
 whence we derive the following rule : 
 
 Multiply the molecular mass by the percentage 
 amount of the given constituent, and divide the prod- 
 uct by its atomic mass, multiplied by 1OO. The quo- 
 tient is the number of atoms of that constituent in the 
 molecule. 
 
 Having obtained in this way the number of each kind 
 of atoms composing a molecule, it is easy to construct the 
 molecular formula. 
 
 EXAMPLES. What is the formula of quartz, its molecular mass 
 being 60, and its percentage composition: 
 
 Silicon ................ 46-67 
 
 Oxygen ............... 53-33 
 
 100-00 
 
 The atomic mass of silicon is 28; hence by formula (2) the number 
 of atoms of - ' 
 
 Q-T n >. 60X46-67 
 
 Silicon would be - = 1 
 100X28 
 
 60X53-33 
 
 Oxygen " " - =2 
 
 100X16 
 
 The molecular formula of quartz is therefore SiO.,. 
 
STOH'HIOMKTRH'AL CALCULA T1ONS. 83 
 
 THIRD CASE. Having the percentage composition, the 
 number of atoms of any constituent in the molecule, and 
 the molecular mass, to find the atomic mass of that atomic 
 constituent. From formula (1) by transposition, we obtain : 
 
 The rule therefore is : 
 
 Multiply the molecular mass by the percentage 
 amount of the constituent whose atomic mass is de- 
 sired, and divide the product by the number of atoms 
 multiplied by 1OO. The quotient is the atomic mass 
 required. 
 
 EXAMPLES. The molecular mass of silver nitrate is 170; it con- 
 tains 63-53 per cent of silver, and has but one atom of silver in a 
 molecule. What is the atomic mass of silver? 
 
 Making the necessary substitutions in formula (3) we have 
 
 170X63-53 
 
 - =108 
 100X1 
 
 Hence the atomic mass of silver is 108. 
 
 FOURTH CASE. Having the atomic mass of any constitu- 
 ent, the number of atoms of it in the molecule, and its per- 
 centage amount, to find the molecular mass. 
 
 By a final transposition of formula (1), we obtain : 
 
 Whence the rule : 
 
 Multiply the atomic mass of the constituent given 
 by the number of its atoms, and this product by 1OO. 
 Divide the final product by the percentage amount 
 of that constituent, and the quotient is the molecular 
 mass. 
 
 EXAMPLES. Salt contains 39-32 per cent of sodium, whose atomic 
 mass is 23. In a molecule of salt there is but one atom of sodium. 
 What is the molecular mass of salt? 
 
84 THEORETICAL CHEMISTRY. 
 
 23V1 VlOO 
 By substitution, = 58-5. The molecular muss of salt 
 
 is therefore 58-5. 
 
 Again, ferric oxide contains three atoms of oxygen, or 30 per cent. 
 What is its molecular mass ? 
 
 By the formula, - = 160, the molecular mass. 
 
 133. Calculation of an Atomic Group. Iii some 
 cases it is desirable to calculate the percentage amount of a 
 group of atoms in any molecule. Formula (1) above given 
 enables us to do this, using a to indicate the mass of the 
 group, and n the number of such groups in the molecule. 
 
 EXAMPLES. Ammonium nitrate, (NH 4 )NO 3 , breaks up under the 
 influence of heat into one molecule of nitrogen oxide, N 2 O, and two 
 molecules of water, (H 2 O) 2 . How much nitrogen oxide in 100 parts 
 of ammonium nitrate? 
 
 ,, 44x1X100 
 
 By formula (1) - , we have --- = 55. Hence am- 
 
 monium nitrate yields 55 per cent of nitrogen oxide. 
 
 134. Other than Percentage Numbers. Problems 
 often arise which require the quantity of a constituent in 
 less or more than 100 parts. The answers to such problems 
 can of course be obtained by stating the proportion for each 
 problem; but they may be derived also from formula (1) 
 already given, by putting y the quantity of the constitu- 
 ent in place of x, and z the quantity of the compound 
 in place of 100. The formula then becomes : 
 
 anxz (5) 
 
 222 
 
 Whence the rule : - 
 
 Multiply the mass of the constituent contained in 
 one molecule by the mass of the compound given in 
 the problem, and divide this product by the molecular 
 mass. The quotient is the quantity of the constituent 
 required, 
 
STOICHIOMETRICAL CALCULATIONS. 85 
 
 EXAMPLES. How much iodine may be obtained from 236 grams 
 of potassium iodide, the atomic mass of iodine being 127, and the 
 molecular mass of potassium iodide being 166? 
 
 By proportion. As 166 parts of potassium iodide give 127 of iodine, 
 it is obvious that the quantity given by 236 parts would be given by 
 the proportion 166 : 236 : : 127 : y. Whence jr=180-5. Answer, 180-5 
 grams iodine. 
 
 By formula (5). Substituting for an in formula (5), 127, for z, 236, 
 
 127X236 
 and for 122, 166, we have jr - 180-5. Hence 236 grams 
 
 potassium iodide yield 180-5 grams iodine. 
 
 Conversely, if the quantity of the compound necessary to 
 yield a given mass of the constituent be required, we obtain 
 by transposition : 
 
 an 
 
 EXAMPLES. How much potassium iodide would be required to 
 yield 78 grams iodine? 
 
 1 AA\/ 7Q 
 
 Substituting in formula (6) we have z = -- = 102. Answer, 
 102 grams potassium iodide. 
 
 By analysis. If 166 parts potassium iodide yield 127 of iodine, to 
 
 166 
 yield 1 part of iodine - of one part will be required; and to yield 
 
 166 166x78 
 78 parts, 78 times or - , will be required. But this is the 
 
 precise result given above. 
 
 135. Calculation from Equations. The same princi- 
 ples are applied in calculating the mass of substances enter- 
 ing into, or issuing from, chemical reactions. The reaction 
 is first to be expressed in the form of an equation. The 
 molecular mass of all the substances given are then to be 
 written below their respective formulas. Having now the 
 data, the problems are to be solved by making the following 
 proportion : 
 
 As the molecular mass of the substance given is to 
 
 7 
 
86 THEORETICAL CHEMISTRY. 
 
 the quantity of it given in the problem, so is the molec- 
 ular mass of the substance required to the quantity 
 of it required. 
 
 Representing by M the molecular mass of the substance 
 given, by W the absolute mass of this substance given in 
 the problem, by 122 the molecular mass of the substance re- 
 quired, and by w the absolute mass of this substance, then 
 by the above rule we have the proportion M : W: : 222 : W, 
 from which the four following formulas may be derived : 
 
 W -Z22 
 
 W M. 
 
 Hence, any three of these quantities being given, it is easy 
 to find the fourth. Four cases thus arise, viz : 
 
 1. Having the absolute quantity of a factor and the quan- 
 tity of the product yielded by it, as well as the molecular 
 mass of the product ; to find the molecular mass of the factor. 
 
 2. Having the molecular mass of both factor and product, 
 to find the quantity of the factor necessary to yield a given 
 mass of the product. 
 
 3. Having the quantity of the factor, the quantity of the 
 product, and the molecular mass of the factor; to find the 
 molecular mass of the product. 
 
 4. Having the molecular mass of both factor and product, 
 to find the mass of the product from a given weight of the 
 factor. 
 
 EXAMPLES. Nitric acid is prepared by the action of sulphuric 
 acid upon potassium nitrate, according to the following equation : 
 
 K(N0 3 ) + H 2 (SO 4 ) = H(N0 3 ) + HK(SO 4 ) 
 
 101 -f 98 = 63 + 136 
 
 Problem 1st. 125 grams of niter yield 77 - 97 grains of nitric acid, 
 whose molecular mass is 63 ; what is the molecular mass of potassium 
 nitrate ? 
 
STOICHIOMETRICAL CALCULATIONS. 87 
 
 In this problem, 122 equals 63, W equals 125, and w equals 77-97; 
 
 63X125 
 
 hence M = ~ = 101. Answer. 
 77-97 
 
 Problem 2d. The molecular mass of niter is 101, and that of nitric 
 acid is 63; how much niter would be required to yield 77-97 grams 
 nitric acid? 
 
 Here, the quantities being represented as before, we have W = 
 
 101X77-97 
 
 = 125 grams, Answer. 
 
 Problem 3d. 125 grams of niter yield 77-97 grams of nitric acid. 
 The molecular mass of niter is 101 ; what is the molecular mass of 
 nitric acid? 
 
 101X77-97 
 
 In this problem, m = = 63, Answer. 
 
 125 
 
 Problem 4th. The molecular mass of niter is 101 and that of nitric 
 acid is 63; how much nitric acid would 125 grams of niter yield? 
 
 63X125 
 We have w= = 77-97 grams, Answer. 
 
 Formulas (2) and (4) are the ones usually employed, since 
 molecular masses may generally be obtained more readily in 
 other ways. These two formulas may be applied to a great 
 variety of problems, as the following examples show. 
 
 EXAMPLES. Taking the equation for the production of nitric acid 
 by the action of su-lphuric acid on potassium nitrate, above given, the 
 following problems may be worked by formula (2) : 
 
 Problem 1st. How much niter is necessary to yield 36 grams of 
 nitric acid? 
 
 101X36 
 
 W= 57-7 grams, Answer. 
 63 
 
 Problem 2d. How much sulphuric acid will be required? 
 
 98X36 
 
 Here M 98; hence W= = 66 grams, Answ r er. 
 
 63 
 
 Problem 3rf. How much hydro-potassium sulphate will be pro- 
 duced ? 
 
 136X36 
 
 M in this problem = 136; hence W= 77-7 grams, An- 
 
 63 
 
 swer. 
 
 And these problems by formula (4): 
 
88 THEORETICAL CHEMISTRY. 
 
 Problem 1st. How much nitric acid may be produced i'rom 500 
 grams of potassium nitrate? 
 
 222 W 63X500 
 
 W= - = 31T88 trains, Answer. 
 
 M 101 
 
 Problem 2d. How much sulphuric acid would be required to de- 
 compose 500 grams niter ? 
 
 98X^00 
 Here m = 98; hence w = 485-15 grams, Answer. 
 
 Problem M. How much hydro -potassium sulphate would be 
 yielded by the decomposition of 500 grams of potassium nitrate by 
 sulphuric acid? 
 
 136X500. 
 
 In this problem m = 136; hence w = 673-27 grains. 
 
 In all the above problems it has been assumed that cadi 
 molecule of the factor yielded one of the product. If in any 
 reaction this is not true, then M and 222 must represent the 
 sum of the molecular masses expressed in the equation. 
 
 136. Volume Calculations from Equations. Every 
 molecular formula represents two volumes. Hence any equa- 
 tion composed of such formulas may be read by volume. 
 From these volumes calculations may be made as well as 
 from the masses. 
 
 EXAMPLES. In the equation : 
 
 (C0) 2 + 2 = (C0 2 ) 2 
 
 two molecules carbon mon-oxide and one molecule of oxygen yield 
 two molecules carbon di-oxide the volume relations may be read 
 thus: four volumes carbon mon-oxide and two volumes of oxygen 
 give four volumes of carbon di-oxide. From these relations the fol- 
 lowing problems may arise: 
 
 Problem 1st. How much carbon di-oxide is formed by the com- 
 bustion of 1 liter of carbon mon-oxide ? 
 
 As 4 volumes carbon mon-oxide yield 4 of carbon di-oxide, 1 vol- 
 ume will yield 1 volume, and 1 liter of course 1 liter, Answer. 
 
 Problem Id. How much oxygen is needed to convert 2 liters car- 
 bon mon-oxide to carbon di-oxide? 
 
 Four volumes by the equation require 2 of oxygen ; hence 2 liters 
 will require 1 liter of oxygen, Answer, 
 
STOICHIOMETRICAL CALCULATIONS. 89 
 
 Problem M. To form 100 cubic centimeters of carbon di-oxide 
 how much carbon mon-oxide must be burned? 
 
 Four volumes carbon di-oxide require the combustion of four of 
 carbon mon-oxide; 100 cubic centimeters will require its own volume 
 therefore, or 100 cubic centimeters, Answer. 
 
 137. Relations of Mass to Volume. It is often neces- 
 sary to calculate the volume occupied by a given mass of any 
 gas, or the mass of any given volume. The following are 
 the rules : 
 
 1. To determine the volume of any gas, its mass being 
 given : Divide the mass of the gas given, by the mass 
 of one liter ; the quotient is the number of liters. 
 
 2. To determine the mass of any given volume of gas : 
 Multiply the number of liters of gas by the mass of 
 one liter ; the product is the mass of the given volume. 
 
 EXAMPLES. 
 
 1. What volume is occupied by 6-08 grams of oxygen gas? 
 
 The mass of one liter of oxygen is 1-43 grams; hence in 6-08 
 grams there will be as many liters as 1-43 is contained times in 6-08; 
 or 4-25 liters, Answer. 
 
 2. What is the mass of 25 liters of nitrogen gas ? 
 
 The mass of one liter of nitrogen gas is 1-26 grams. 1-26X25 = 
 31-5; hence the mass of 25 liters of nitrogen is 31-5 grams, Answer. 
 
 138. Relation of Volume to Density. Relative den- 
 sity being the mass of one volume of any gas compared 
 with the same volume of hydrogen and molecular mass 
 being the mass of two volumes, it is evident that the relative 
 density of any body in the state of gas may be obtained by 
 dividing its molecular mass by two. 
 
 Having the relative density of any gas which expresses 
 how many times the gas is denser than hydrogen the mass 
 of one liter may be readily obtained by multiplying it into 
 the mass of one liter of hydrogen. The mass of one liter 
 of hydrogen is 0*0896 grams, or 1 crith. 
 
92 THEORETICAL CHEMISTRY. 
 
 lowered, the formula for calculating an increase of volume 
 will be approximately : 
 
 V = Vx(l+ -003665 1) (1) 
 
 And by transposing, the formula by which the volume at a 
 lower temperature can be calculated is obtained : 
 
 V 
 
 V= (2) 
 
 (1 + -003665 1) 
 
 EXAMPLES. 
 
 1. A gas measures 15 cubic centimeters at 0; what will it measure 
 at 60? 
 
 Substituting in (1), V'= 15X(1 + 60X'U03665) = 18-298 c. c., Ans. 
 
 2. What will a gas measure at 0, which, at 100, measures 40-1 c. c.? 
 
 40-1 
 
 Substituting in (2), V = 29-345 c. c., Answer. 
 
 (I + IOOX'003665) 
 
 3. A gas measures 560 c. c. at 15; what will it measure at 95? 
 
 / ( 1 -I- 95 X '003665) 
 
 Here t = 15 and f ' = 95. Hence V = 560 - 
 
 (1-J-16X '008666) 
 
 715-6 cubic centimeters, Answer. 
 
EXERCISES. 93 
 
 EXERCISES. 
 1. 
 
 1. What is molecular stability? 
 
 2. What is a chemical reaction? A chemical re-agent? 
 
 3. Explain why mass-reactions may be accurately represented by 
 molecular formulas. 
 
 4. What is a chemical equation? How is it constructed? 
 
 5. Give the rule for writing equations. Illustrate it. 
 
 6. Does matter disappear in chemical changes? 
 
 7. How are chemical reactions classified ? Illustrate. 
 
 8. Why does solution favor chemical changes? 
 
 9. Give Berthollet's first law. Define precipitate, precipitation. 
 
 10. Distinguish the chemical part of this process of precipitation 
 from the physical. 
 
 11. Give Berthollet's second law. Illustrate it. 
 
 12. How may results be predicted by these laws? 
 
 13. If barium chloride and magnesium sulphate bo mixed, together 
 in solution, will there be a reaction? Lead nitrate and ammonium 
 phosphate? Sodium hydrate and zinc iodide? Write the reaction 
 in each case. 
 
 14. In what ways may chemical changes in matter take place? 
 Write a reaction of each kind. 
 
 15. State the principle of the Conservation of Energy. How may 
 the energy of a system be varied? 
 
 16. Give the laws of Thermo-chemistry. What is an exothermic 
 reaction? Why are substances formed by endothermic reactions less 
 stable than those formed by exothermic reactions ? 
 
 2. 
 
 17. What are stoichiometrical calculations? 
 
 18. What does a chemical equation represent by mass? 
 
 19. Bead the following equation by mass: 
 
 Sr(NO s ) a +HNa 2 P0 4 =HSrP0 4 +(NaNO s ) a 
 
 20. Deduce the formula for calculating the percentage composition. 
 Give the rule. 
 
94 THEORETICAL C 
 
 21. What is the percentage composition of potassium chlorate? 
 Of sodium carbonate? Of K 3 PO 4 ? Of Zn. 2 SiO 4 ? 
 
 22. Derive the formula, and give the rule for finding the number 
 of atoms of any constituent in any molecule. 
 
 23. Alumina is composed as follows: Aluminum 53-50, Oxygen 
 46-50 = 100. Its molecular mass is 103; what is its formula? 
 
 24. The mineral wollastonite has the following composition: Sili- 
 con 24-14, Calcium 34-48, Oxygen 41-38 = 100. Its molecular mass is 
 116; what is its formula? 
 
 25. How is the formula forgetting the atomic mass derived? Give 
 the rule. 
 
 26. Tin oxide has a molecular mass of 150; it contains one atom 
 of tin, or 78-67 per cent. What is the atomic mass of tin? 
 
 27. Magnetic iron oxide contains three atoms of iron; its percent- 
 age amount of oxygen is 27-60, and its molecular mass is 232. What 
 is the atomic mass of iron? 
 
 28. What is the formula and what the rule for finding the molecu- 
 lar mass? 
 
 29. Zinc sulphide contains 67 per cent of zinc, or one .atom ; the 
 atomic mass of zinc is 65; what is the molecular mass of zinc sulphide? 
 
 30. How may the atomic groupings into which a molecule can be 
 broken up be calculated ? 
 
 31. The mineral magnesite, MgCO 3 , is decomposed by heat into 
 MgO and CO 2 ; what are the percentage amounts of these substances 
 which it contains? 
 
 32. Give the formula and rule in cases where other than percentage 
 numbers are required. 
 
 33. How much lead may be obtained from 564 kilograms lead sul- 
 phide? (At. ms. lead, 207; mol. ms. lead sulphide, 239.) 
 
 34. How much calcium phosphate is required to give 356 kilograms 
 phosphorus? (At. ms. of phosphorus is 31; the molecular mass of 
 calcium phosphate is 310.) 
 
 35. How may the products of a reaction be calculated from the 
 factors ? Give the rule. 
 
 36. Derive the four formulas given, and show the class of problems 
 to which each applies. 
 
 37. From the following equation: 
 
 Zn(NO 3 ) 2 +K 2 CO 3 =ZnCO 3 +(KNO 3 ) 2 
 
 calculate the quantity of zinc nitrate required to give 103-17 grams 
 zinc carbonate. 
 
KXKHCISES. 95 
 
 38. How much ZnCO 3 may be obtained from 156 grams Zn(NO 3 ) 2 ? 
 
 39. How much K 2 CO 3 is needed to decompose 75 grams Zn(NO 3 ) 2 ? 
 
 40. What quantity of potassium nitrate will result? 
 
 41. How much potassium carbonate must bo used in order to obtain 
 54 grams zinc carbonate? 
 
 42. How much potassium nitrate will be produced? 
 
 43. 156 grams zinc nitrate yield 103-17 grams zinc carbonate (mol. 
 ms. 125); what is the molecular mass of zinc nitrate? 
 
 44. 103-17 grams zinc carbonate are obtained from 156 grams of 
 zinc nitrate (mol. ms. 189); what is the molecular mass of zinc car- 
 bonate ? 
 
 45. Read the following equation by volume: 
 
 CH 4 +(0 2 ) 2 =C0 2 +(H 2 0) 2 
 
 46. How much oxygen is needed to burn 1 liter of CH 4 ? 
 
 47. What volume of carbonic di-oxide is produced? 
 
 48. How much CH 4 is needed to give 1 cubic meter of steam? 
 
 49. What volume does a kilogram of oxygen occupy? 
 
 50. One liter of CH 4 in burning gives what mass of CO 2 ? 
 
 51. Calculate the mass of one liter of chlorine; of phosphorus; of 
 H 2 S; of 00; of PC1 3 ; of HNO 3 . 
 
 52. Calculate the specific gravity of nitrogen. 
 
 53. The specific gravity of hydrogen iodide is 4-43; what is its 
 molecular mass ? 
 
 54. How is the formula for reducing gaseous volumes to the normal 
 pressure deduced ? Give the rule. 
 
 55. What is the normal volume of a liter of oxygen measured at 
 756mm.? At 795? At 1140? At 380? 
 
 56. What volume would 350 c. c. of ammonia-gas, measured at 74, 
 have at 0? At 100? At 20? 
 
PART SECOND. 
 
 INORGANIC CHEMISTRY. 
 
 (97) 
 
Part Second. 
 INORGANIC CHEMISTRY. 
 
 CHAPTER FIRST. 
 
 HYDROGEN. 
 
 Symbol H. Atomic Mass 1. Valence I. Relative Density 1. 
 Molecular Mass 2. Molecular Volume 2. T/ie Jlfoss of one 
 liter at is 0-089578 gram (1 mtfi). 
 
 142. History. Hydrogen was apparently known to Par- 
 acelsus in the 16th century. It was first accurately de- 
 scribed by Cavendish in 1766, who called it inflammable 
 air. Lavoisier gave it the name hydrogen. 
 
 14*?. Occurrence. Hydrogen occurs free in certain 
 volcanic gases ; Bunsen found that it formed 45 per cent 
 of the gaseous exhalations of Nimarfjall, Iceland. It also 
 occurs in the gases accompanying petroleum. It is shown 
 by the spectroscope to exist in the sun, the fixed stars, and 
 in some of the nebulas. Graham obtained from the Lenarto 
 meteorite a remarkably pure iron three times its own vol- 
 ume of this gas. 
 
 Combined, hydrogen exists in water, every cubic centi- 
 meter of which contains 1J liters ; also in petroleum and 
 bitumen, and in all animal and vegetable tissues. 
 144. Preparation. Simple molecules are obtained from 
 
 (99) 
 
100 INORGANIC CHEMISTRY. 
 
 compound molecules by re-arranging their atoms. For the 
 production of hydrogen this re-arraugemeut may be effected : 
 
 I. By the action of some physical agent ; as 
 
 (a) Heat. When melted platinum is dropped into water, 
 both hydrogen and oxygen gases are evolved : 
 
 H O H H O H 
 
 forming | 1 1 
 H O H H O H 
 
 or: 
 
 (H 2 0) 2 = <H 2 ) 2 + 2 
 
 This process is called dissociation. 
 
 (b) Electricity. In the electrolysis of hydrogen com- 
 pounds (p. 139). 
 
 II. By superior chemical attraction; as in the action of 
 sodium upon water at ordinary temperatures : 
 
 (HP), + Na, = (HNaO), + H 2 
 
 Hydrogen oxide. Sodium. Sodium hydrate. Hydrogen. 
 
 or of iron and other metals, at a red heat : 
 
 (H.O), + Fe 6 = (Fe,0,), + (H,), 
 
 Water. Iron. Iron oxide. Hydrogen. 
 
 Or of zinc upon an acid, as sulphuric acid : 
 
 H 2 (S0 4 ) + Zn = Zn(S0 4 ) + H, 
 
 Hydrogen sulphate. Zinc. Zinc sulphate. Hydrogen. 
 
 or of magnesium upon a base, as potassic base : 
 
 (HKO), + Mg = Mg"(OK) 2 + H 2 
 
 Potassium hydrate. Magnesium. Potassio-magnesium Hydrogen. 
 
 oxide. 
 
 EXPERIMENTS. The apparatus by which hydrogen is obtained by 
 the action of sodium upon water is shown in Fig. 1. It consists of a 
 glass cylinder filled with water, and inverted in water contained in 
 a cistern. Upon throwing a fragment of sodium upon the water, it 
 rolls about upon the surface, with a hissing noise, as a silver-white 
 globule. By means of the wire-gauze cage shown in the figure, this 
 globule may be depressed below the surface, and held beneath the 
 
PROPERTIES OF HYDROGEN. 
 
 101 
 
 mouth of the glass cylinder. The hydrogen gas set free by the action 
 of the sodium, rises in bubbles into the cylinder, displacing the water. 
 
 By repeating the process a 
 sufficient number of times, 
 the cylinder may be filled. 
 
 The usual method of pre- 
 paring hydrogen is by the 
 action of zinc upon sulphu- 
 ric acid, for which an appa- 
 ratus similar to that shown 
 in Fig. 2 may be used. The 
 zinc is placed in the two- 
 Fig, i. Preparation of Hydrogen by Sodium, necked bottle in place of 
 
 which a wide-mouthed bot- 
 tle having two holes through the cork, may be substituted; through 
 one of these openings a funnel-tube passes to the bottom of the bottle, 
 and through the other a delivery-tube passes to the water-cistern, 
 terminating beneath an inverted cylinder filled with water, which 
 stands within it. On pouring diluted sulphuric acid one part of. 
 the commercial acid mixed with four parts of water and cooled 
 through the funnel -tube upon 
 the zinc, effervescence takes 
 place and bubbles escape from 
 the delivery-tube. After allow- 
 ing time for the air in the bot- 
 tle to escape, the gas may be 
 collected for use. 
 
 145. Properties. I. 
 
 PHYSICAL. Hydrogen is a 
 colorless, odorless, and taste- 
 less gas. It is the lightest 
 form oljrmatter known, be- 
 ing 14*43 times lighter than 
 air, 11,000 times lighter than water, and 240,000 times lighter 
 than platinum. Its molecular mass is therefore smaller than 
 that of any other substance. For this reason, as shown in 
 the section on diffusion, its diffusibility is higher than that 
 of any other gas. Its refractive power on light is remark- 
 
 8 
 
 Fig. 2. Preparation of Hydrogen from 
 Zinc and Sulphuric Acid. 
 
102 INORGANIC CHEMISTRY. 
 
 able, being 6*614 times that of air. It is soluble to a very 
 slight extent in water, 100 volumes of which dissolve but 
 1*9 of hydrogen. 
 
 When subjected to a pressure of 160 atmospheres, and 
 cooled in boiling nitrogen to 213, Olzewski obtained it 
 as a colorless and transparent liquid running down the walls 
 of the tube, by allowing the gas suddenly to expand to 40 at- 
 mospheres ; this sudden expansion producing increased cold. 
 Its critical temperature and pressure have not therefore been 
 determined experimentally. The former, however, has been 
 calculated as 240 and the latter as 13 '3 atmospheres. 
 
 Owing to its lightness, the velocity of sound in hydrogen 
 is trebled, but its intensity is much enfeebled. Hydrogen 
 is the standard of relative density, and of molecular mass 
 and volume. The mass of 1 liter at and 760 millimeters 
 is -089578 gram, or 1 crith. 
 
 EXPERIMENTS. The rapid diffusion of hydrogen gas may be shown 
 very well by'the apparatus represented in Fig. 3. A light, unglazed, 
 cylindrical cup of earthen-ware such as 
 is used in voltaic batteries is cemented, at 
 its open end, to a glass funnel whose stem 
 is prolonged by a slender tube, which dips 
 into colored water. The whole may be sup- 
 ported on any convenient stand. If now, 
 a bell-glass filled with hydrogen be brought 
 over this earthen cup, the gas diffuses so 
 much more rapidly into the cylinder than 
 the air diffuses out, that an increase of vol- 
 ume takes place within it and the gas bub- 
 bles out violently through the water. When 
 the bell-glass is removed, the hydrogen 
 within the cylinder being now in excess, 
 diffuses so rapidly outward as to produce 
 
 a partial vacuum, so that the colored water 
 Fig. 3. Diffusion Apparatus. . r , , ^ <. > 
 
 rises half a meter or more in the tube. 
 
 The levity of hydrogen may be shown by using the gas to inflate 
 soap-bubbles. When detached from the pipe, they rise rapidly. Any 
 
PROPERTIES OF HYDROGEN. 
 
 103 
 
 bag made of thin tissue, such as collodion or varnished paper, may 
 be filled with hydrogen, and will then rise like a balloon. 
 
 The curious effect of hydrogen upon sound may be illustrated by 
 placing in a large bell-glass, suspended mouth downward and filled 
 with this gas, one of the squeaking images used as toys for children. 
 As the image passes up into the gas, the sound is observed to be 
 greatly enfeebled and altered considerably in character. The same 
 fact may be shown with the human voice by filling the lungs with 
 the gas, and then speaking. Especial care should be taken, however, 
 to have the gas for this purpose made from pure materials ; for, 
 although the lungs may be filled once with hydrogen gas without 
 injury if it is pure, yet it is liable to contain impurities which may 
 produce serious results. 
 
 II. CHEMICAL. Hydrogen gas is combustible ; that is, 
 when heated to a certain degree about 500 it is capable 
 of combining with the oxygen of the air with the evolution 
 of light and heat. The flame of burning hydrogen is pale, 
 and, under the atmospheric pressure, is scarcely luminous; 
 though it becomes bright if the pressure be increased. The 
 heat evolved by it is very great ; one gram of hydrogen in 
 burning produces heat sufficient to raise 34,180 (Thomsen) 
 grams of water from to 1; that is, 34,180 heat-units. It 
 does not support combustion or respiration ; a lighted candle 
 placed in it is extinguished and an animal 
 loses his life when confined in it. It is 
 the standard of atomic mass and of val- 
 ence. 
 
 EXPERIMENTS. A cylinder full of the gas 
 collected as shown in Fig. 2, for example may 
 be inverted, and a lighted taper applied to its 
 mouth. The hydrogen takes fire with a slight 
 explosion and burns with its characteristic flame. 
 If the jar be held mouth downward, and the 
 candle be passed up into it, as shown in Fig. 4, Fig. 4. Combustibility 
 the gas takes fire and burns quietly at the open 
 
 end, while the flame of the candle, as it passes into the gas, is extin- 
 guished, but may be relighted again from the burning hydrogen as it 
 is withdrawn. 
 
104 
 
 L\0/{<; A XI (' CHEMISTRY. 
 
 The combustibility, and at the same time the levity, of hydro- 
 gen may be shown by covering a bell-glass of this gas with a glass 
 plate, and holding it, mouth upward, beneath a lighted candle six or 
 eight inches distant. On removing the plate the gas rises from the 
 bell, comes in contact with the flame and takes fire 
 with a slight explosion. The same fact is shown 
 by pouring a bell-glass full of this gas upward into 
 an empty bell, testing each, after the experiment, 
 with a lighted candle. If the soap-bubbles above 
 mentioned be touched with a lighted taper as they 
 ascend (Fig. 5), they take fire and burn with a slightly 
 yellow flame. 
 
 Water is the sole product of the combus- 
 tion of hydrogen. Hence its name, from 
 and evvctw water-former. 
 
 Fig. 5. Lighting a 
 
 "When burned from a jet, as shown in Fig. 6 
 
 being previously dried by passing it through a tube 
 
 containing calcium chloride the flame of hydro- 
 
 gen, though pale, is very hot, and will raise a small 
 
 coil of fine platinum wire placed within it to a white 
 
 heat. On holding a cold and dry bell-glass over 
 
 this flame, it is at once dimmed 
 with the moisture, and if the ex- 
 periment be sufficiently long-con- 
 tinued the water produced will 
 run down the sides of the bell- 
 glass in drops. 
 
 Several years ago Graham 
 pointed out the fact that hy- 
 drogen is capable of being 
 absorbed or occluded by many 
 metals, at temperatures more 
 or less elevated. Of these 
 Fig. 6. Water from the combustion of metals, palladium is the most 
 
 remarkable, being able to 
 
 take up over nine hundred times its volume of hydrogen at 
 ordinary temperatures, forming a white metallic solid, con- 
 
USES OF HYDROGEN. 105 
 
 taining its constituents in ratios nearly atomic. Graham 
 maintained that the hydrogen in this substance is a solid 
 metal, with a density about 2, and analogous in many respects 
 to magnesium ; that it has a metallic luster, a certain amount 
 of tenacity, conducts heat and electricity readily, and is mag- 
 netic. He therefore proposed for it the name hydrogenium. 
 
 14O. Uses. On account of its lightness, it has been used 
 to fill balloons for military and other purposes. The amount 
 which a balloon will carry up, i. e., its ascensional power, is 
 the difference between the weight of the balloon itself with 
 its contained hydrogen, and that of an equal volume of air. 
 A liter of hydrogen gas has an ascensional force of 1*2 
 grams. 
 
 Hydrogen is used also in the arts as a heating material, 
 on account of the high temperature developed by its com- 
 bustion. 
 
106 INORGANIC CHEMISTRY. 
 
 EXERCISES. 
 
 1. Mention some substances which contain hydrogen. 
 
 2. Write the equation which expresses the preparation of hydro- 
 gen by the action of potassium upon water. 
 
 3. Give the reaction which takes place when iron acts on sulphuric 
 acid. 
 
 4. Ten grams of water will give how many grams of hydrogen 
 when decomposed by heat? By the action of sodium? 
 
 5. How many cubic centimeters in each case ? 
 
 6. How many grams of sodium will be required ? 
 
 7. Ten liters of hydrogen are desired; how many grams of zinc 
 are necessary to furnish this quantity? How many grams of iron? 
 
 8. Twenty grams magnesium will yield how many liters of hydro- 
 gen? How many grams of potassium hydrate must be employed? 
 
 9. "What will hydrogen cost per cubic meter, when- made with 
 iron costing 7 cents and sulphuric acid costing 15 cents per kilogram? 
 When made with zinc costing 22 cents per kilogram ? 
 
 10. What volume of hydrogen does one liter of vrater contain? 
 One liter of water-vapor or steam? 
 
 11. What volume does 0-423 gram of hydrogen occupy at 0? At 
 15? At 100? 
 
 12. Calculate the specific gravity of hydrogen from its relative 
 density. 
 
 13. To what temperature must air be raised to have the relative 
 density of hydrogen at 0? 
 
 14. Under what barometric pressure has air the relative density of 
 hydrogen? 
 
 15. From what does the name hydrogen come ? 
 
 16. What is a unit of heat? How many heat-units does hydrogen 
 produce in its combustion ? 
 
 17. How many grams of hydrogen must be burned to raise 50 kilo- 
 grams of water from to 10? 
 
 18. What must be the diameter of a spherical balloon which, when 
 filled with hydrogen, will have an ascensional force of 80 kilograms; 
 the balloon itself weighing 30 kilograms? 
 
 19. What will it cost to inflate the above balloon, if the hydrogen 
 be prepared by the use of sodium at two dollars the kilogram? 
 
PREPARATION OF CHLORINE. 107 
 
 CHAPTER SECOND. 
 
 NEGATIVE MONADS. 
 
 1. CHLORINE. 
 
 Symbol Cl. Atomic mass 35-37. Valence, I, III, V, and VII. 
 Relative density 35'37. Molecular mass 70'74. Molecular 
 volume 2. 27ie wows o/ 1 Zifer a is 3-167 grams (35 -37 
 criths). 
 
 147. History. Chlorine was first obtained by Scheele 
 in 1774, and called dephlogisticated muriatic acid ; a name 
 afterward changed to oxymuriatic acid by Berthollet. In 
 1809 G-ay-Lussac and Thenard suggested its elementary 
 character, which was established by Davy in 1810, who gave 
 it the name it bears. 
 
 148. Occurrence. Chlorine never occurs free in nature. 
 In combination with sodium, magnesium, potassium and cal- 
 cium, it exists abundantly in saline springs, and also in sea- 
 water, every liter of which contains 5 liters of chlorine. 
 Sodium chloride or salt exists also in the solid form in the 
 earth, forming vast deposits, many of which, like that at 
 Stassfurt, are mined. 
 
 149. Preparation. Chlorine may be prepared : 
 
 I. By the action of heat or of electricity upon chlorides. 
 
 PtCl 4 = PtCl 2 + C1 2 
 
 Platinic chloride. Platinous chloride. Chlorine. 
 
 II. By the superior chemism of oxygen ; as when hydro- 
 gen chloride acts upon manganese di-oxide : 
 
 (HC1) 4 + Mn0 2 = MnCl 2 + (H 2 O) 2 + C1 2 
 
 Hydrogen Manganese Manganom Water. Chlorinf. 
 
 chloride. di-6xide. chloride. 
 
108 
 
 TXOIifi A XIC CHKMrSTR T. 
 
 Or, when sodium chloride, sulphuric acid and manganese 
 di-oxide are heated together : 
 
 (Nad), + (H.CSO,)), 
 
 Sodium chloride. Sulphuric acid. 
 
 Mn(S0 4 ) 4- Na. 2 (SO 4 ) + 
 
 Manganous sulphate. Sodium sulphate. 
 
 + MuO 2 = 
 
 Manganese di-oxide. 
 
 (H 2 O) 2 4 C 
 
 Water. Chlo 
 
 EXPERIMENTS. The apparatus employed for preparing chlorine 
 is shown in Fig. 7. The materials are placed in a flask, which stands 
 in sand contained in a thin iron cup, upon the gas furnace. Through 
 the cork of this flask two tubes pass, one for the delivery of the gas, 
 the other a safety-tube. This safety-tube is a funnel-tube bent twice 
 upon itself, upon the recurved portion of which are two bulbs. When 
 any liquid is poured into the funnel, a portion remains in the bend 
 
 and acts as a valve to 
 prevent the escape of 
 the gas. Should the 
 pressure within be in- 
 creased, the gas will 
 force the liquid up into 
 the funnel and escape 
 through it in bubbles; 
 should it be diminished, 
 the outside pressure 
 will force the liquid 
 into the bulbs and air 
 will enter, thus avoid- 
 ing accident. To the 
 delivery-tube is attach- 
 ed, by means of a rub- 
 ber tube, a bottle con- 
 taining sulphuric acid, 
 to the bottom of which 
 this delivery-tube passes, and through which the gas is made to bubble, 
 in order to dry it. From this drying-bottle it passes through a long 
 glass tube to the bottom of the cylindrical gas-jar, where, being heavier 
 than air, the gas gradually collects. When full, a fact easily ascer- 
 tained from the green color of the gas, the mouth of the cylinder is 
 closed with a glass plate smeared with a little tallow. If a series of 
 these jars be closed with glass covers perforated for two tubes, they 
 
 Fig. 7. Preparation of Chlorine. 
 
PROPERTIES OF CHLORINE. 109 
 
 may be successively filled by displacement with the gas. For every 
 liter of chlorine gas, 8 grams of manganese di-oxide and 20 grams 
 hydrochloric acid (of commercial strength, sp. gr. about 1-16) are re- 
 quired. The acid is placed in the flask first, the di-oxide is then added, 
 and the whole agitated. The evolution goes on for a time without 
 heat, but to complete the operation the gas beneath must be lighted. 
 
 Commercially, as in Deacon's process, the oxygen of the air may 
 be used to decompose hydrogen chloride. This process consists in 
 passing a mixture of hydrogen chloride and air through heated tubes 
 containing balls of clay soaked in a solution of copper sulphate and 
 dried. The copper sulphate remains unchanged, a series of interme- 
 diate compositions and decompositions taking place. The process is 
 continuous, water and chlorine being the only products. Weldon's 
 process regenerates the MnCl 2 by converting it into CaMnO 3 , calcium 
 manganite. And this, by the action of hydrogen chloride, produces 
 as before MnCl 2 and chlorine. 
 
 15O. Properties. I. PHYSICAL. Chlorine is a yellow- 
 ish-green gas its name coming from %Aatp6q t yellowish-green 
 of a peculiar suffocating odor and astringent taste. It is 
 totally irrespirable, producing coughing, even when very di- 
 lute, and in larger quantity, inflammation of the air -pas- 
 sages. Its specific gravity is 2*46; it is therefore nearly two 
 and one half times heavier than air. Under a pressure of 
 four atmospheres at the ordinary temperature, or when sub- 
 jected without pressure to a cold of 40, it is condensed 
 to a dark yellow liquid of specific gravity 1-38, which boils 
 at 35*5 and solidifies when cooled to 102. It is quite 
 soluble in water, one volume of which at 11 dissolves nearly 
 three volumes of chlorine gas, forming a solution which pos- 
 sesses essentially the properties of the gas itself. Cooled to 
 0, a definite molecular compound crystallizes out, which con- 
 tains, to every molecule of chlorine, 10 molecules of water. 
 
 II. CHEMICAL. Chlorine has an exceedingly strong at- 
 traction for other substances. It combines directly with all 
 the elements except oxygen, nitrogen, and carbon. When 
 finely divided copper, antimony, or arsenic is placed in the 
 gas it combines with it, with the evolution of light and 
 
110 /.Vo/,v;j.V/Y CHEMISTRY. 
 
 heat, to form a chloride. Phosphorus at ordinary tempera- 
 tures, and sodium at more elevated ones, burn in chlorine 
 spontaneously, forming phosphoric and sodium chlorides. Its 
 attraction for hydrogen is specially strong, the two gases ex- 
 ploding violently when mixed together and exposed to sun- 
 light, or on the approach of a flame. In an atmosphere 
 of hydrogen, chlorine gas burns freely, as hydrogen burns 
 freely in one of chlorine. The heat of the combustion of 
 hydrogen in chlorine is less than in oxygen, being but 22,000 
 (Thomsen) units. Chlorine does not burn in the air at any 
 temperature, owing to its slight attraction for oxygen. 
 
 ALLOTROPISM. Chlorine is capable of existing in two 
 states or conditions, the one active, the other passive. The 
 passive condition is the one obtained when the chlorine is 
 prepared in the dark ; when prepared in full daylight it 
 becomes exceedingly active, capable of effecting unions not 
 before directly possible. Chlorine prepared in the dark may 
 be mixed with hydrogen, without combination taking place. 
 But place the mixture in the full sunlight and it at once 
 explodes. So a solution of chlorine in water, placed in the 
 sunlight in an inverted jar, loses its color, hydrogen chloride 
 being formed and oxygen set free. 
 
 The existence of an element in two conditions, in one of 
 which it has different properties from those exhibited by the 
 other, is called allotropism. The substance is said to exist 
 in two allotropic states. It is probable that allotropism is 
 due only to differences in molecular atomicity. 
 
 One of the most noticeable properties of chlorine is its 
 bleaching power, due to its attraction for hydrogen. But 
 chlorine will not bleach except in the presence of water. 
 Water is decomposed by active chlorine, and the oxygen 
 which is thereby set free, being evolved in the nascent or 
 atomic state, destroys the vegetable coloring matter. Min- 
 eral colors in general are unaffected by chlorine. In some 
 cases, however, the chlorine may combine with one or more 
 
PROPERTIES OF CHLORINE. 
 
 Ill 
 
 of the constituents of the coloring matter, forming thereby 
 colorless compounds. Its tendency to unite with hydrogen 
 and thus to destroy foul-smelling gases, of which this hydro- 
 gen is a constituent, is the cause of its value as a disinfecting 
 agent. 
 
 EXPERIMENTS. The action of chlorine upon the metals may be 
 shown by dropping into a jar of the gas thin leaves of copper or 
 bronze-leaf, or shaking into it some powdered arsenic or antimony. 
 The metals burn spontaneously and vividly as they enter the gas. 
 Phosphorus, introduced in a combustion- 
 spoon a cup attached to the end of a bent 
 wire is instantly 'inflamed. Sodium, if 
 previously heated to redness, burns brill- 
 iantly in a jar of chlorine. 
 
 A lighted candle lowered into the gas 
 burns with a smoky flame at first, as shown 
 in Fig. 8, but is soon extinguished. The Combustion 
 chlorine takes the hydrogen of which the P on - 
 wax is composed, and the carbon is set free in the 
 form of smoke. A more striking way of showing the 
 relative attractions of chlorine for hydrogen arid for 
 carbon is shown in Fig. 9. A jar of pure chlorine has 
 thrust into it a piece of thin tissue paper, previously 
 moistened with warm oil of turpentine. The chlorine 
 seizes the hydrogen of the turpentine, evolving so 
 much heat in the combination that the whole takes 
 fire, evolving dense clouds of smoke. 
 
 Either the gas, or its solution in water, may be 
 used to show its bleaching power. Pieces of print 
 having various designs upon them in color, when 
 moistened and placed in contact with the chlorine, 
 will have their colors discharged. A piece of paper 
 covered with characters, partly written and partly 
 printed, loses entirely all the writing upon it when 
 placed in chlorine; the writing-ink being attacked, 
 while the printing-ink, made of carbon, is unaffected. Fig. 9. Turpentine 
 
 The action of oxygen upon hydrogen chloride to in chlorine - 
 set free chlorine and the apparently contradictory action of chlorine 
 upon hydrogen oxide to set free oxygen afford an interesting example 
 
 Fig. 8. Candle 
 
 burning in 
 
 Chlorine. 
 
112 jxona.ixrc CHEMISTRY. 
 
 of the law of maximum work. Since to form a molecule of water- 
 vapor 57,160 heat-units are evolved, while to decompose two mole- 
 cules of gaseous hydrogen chloride only 44,000 heat-units are absorbed, 
 the reaction C1 2 
 
 is evidently an exothermic reaction and therefore takes place without 
 outside aid. So, on the other hand, since the formation of two mole- 
 cules of hydrogen chloride in solution in water evolved 78,630 heat- 
 units, while the decomposition of one molecule liquid water absorbs 
 only 68,360 heat- units, the converse reaction 
 
 H 2 + C1 2 = (HOI), -f O 
 
 is also exothermic, and under the given circumstances will take place 
 without the assistance of external energy. 
 
 151. Tests. Free chlorine may be detected readily by 
 its odor, and, if pure, by its color, its bleaching action upon 
 indigo, and by the dense white fumes which it gives with 
 ammonia. In solution, it is detected by its power of dis- 
 solving gold leaf. In combinations, it yields with solutions 
 of silver salts a white precipitate of silver chloride, insoluble 
 in nitric acid. 
 
 152. Uses. Chlorine is used very largely in the arts for 
 the preparation of the so-called chloride of lime, the form in 
 which this gas is made available as a bleaching agent. The 
 process employed on the large scale is the second given in a 
 former section. Salt and sulphuric acid, together with man- 
 ganese di-oxide, or sometimes nitric acid, are heated together 
 in large leaden vessels, and the gas as produced is conducted 
 into long, low, stone chambers, upon the floor of which dry 
 slacked lime is placed for the purpose of absorbing it. 
 
 COMPOUNDS OF CHLORINE WITH HYDROGEN. 
 
 HYDROGEN CHLORIDE. Formula HC1. Molecular mass 36-37. 
 Molecular volume 2. Relative density 18*18. The mass of 1 
 liter at is 1*63 grams (18-18 crtihs). 
 
 153. History. Only one compound of chlorine and hy- 
 drogen is known ; this is hydrogen chloride, or as it is more 
 
PREPARATION OF HYDROGEN CHLORIDE. 
 
 113 
 
 frequently called, hydrochloric acid. It was known to the 
 alchemists under the name " spirit of salt." Glauber in the 
 17th century gave it the name muriatic acid, from the Latin 
 muria, brine. The pure gas was first obtained by Priestley 
 in 1772, though it was not till 1810 that its true composition 
 was ascertained by Davy. 
 
 154. Preparation. I. Since chlorine and hydrogen are 
 both monads, and their molecules are both di-atomic, it fol- 
 lows that they unite in equal volumes. Hydrochloric acid 
 may be formed therefore by the direct union of equal volumes 
 of its constituents, according to the equation : 
 
 H 2 + C1 2 = (HC1) 2 
 
 This equation also declares that the volume of the hydrogen 
 chloride is the same as that occupied by the hydrogen and 
 chlorine which formed it. \ 
 
 EXPERIMENTS. If a suitable 
 jar be filled, one half with hydro- 
 gen, the other half with chlorine, 
 and a flame be applied to the 
 open mouth as shown in Fig. 10, 
 a smart explosion takes place, 
 and white fumes of hydrochloric 
 acid are formed. In this experi- 
 ment it is well to wrap a towel 
 about the cylinder, to prevent 
 the pieces from flying in case of 
 breakage. If the glass be strong 
 enough, the mixture of gases may 
 be exploded by exposing the jar 
 to sunlight. On opening it after- 
 ward, with the mouth under mer- 
 cury, none will enter, thus show- 
 ing that the volume of the hydrochloric acid produced is the same as 
 that of the chlorine and hydrogen before union. 
 
 II. The second method of preparing hydrochloric acid, 
 and the one usually employed, is by the action of sulphuric 
 
 Fig. 10. Direct union of Hydrogen and 
 Chlorine. 
 
114 
 
 INORGANIC CHEMISTS Y. 
 
 acid upon a chloride, generally sodium chloride, or salt. The 
 reaction is : 
 
 (Nad), + H 2 (S0 4 ) = Na 2 (S0 4 ) + (HC1) 2 
 
 Sodium chloride. Hydrogen sulphate. Sodium sulphate. Hydrogen chloride. 
 
 By passing the gas thus set free through water so long as it 
 is absorbed, the liquid acid is obtained. 
 
 EXPERIMENTS. For the preparation of the gas from salt and sul- 
 phuric acid, the apparatus shown in Fig. 11 may be employed. The 
 salt is placed in the flask, and upon it is poured, through the safety- 
 tube, twice its weight of sulphuric acid, previously diluted with one- 
 
 Fig. 11. Preparation of Hydrochloric Acid. 
 
 fourth its volume of water. Upon applying a gentle heat, the gas 
 is copiously evolved, and may be collected either over mercury or by 
 displacement. 
 
 If it is desired to obtain the liquid acid, the gas is passed through 
 water contained in the series of bottles shown in the figure, called 
 Woulfe's bottles. The first bottle, which is smaller than the others, 
 contains water to wash the gas, which then passes into the larger 
 bottles, charging the water in each in succession. 
 
 155. Properties. Hydrogen chloride is a colorless, pun- 
 gent, acid gas, which fumes strongly in the air, is irrespira- 
 ble, and extinguishes flame. Its critical temperature is 52*3, 
 and its critical pressure is 86 atmospheres ; so that when sub- 
 
PROPERTIES OF HYDROGEN CHLORIDE. 
 
 11") 
 
 jected to a pressure of 40 atmospheres at 10, or of 2 atmos- 
 pheres at 70, it is condensed to a colorless limpid liquid 
 having a specific gravity of 1'27, boiling at 8O3 under 
 atmospheric pressure, and solidifying at 116. It is re- 
 markably soluble in water, one volume of which dissolves 
 450 volumes of this gas at 15, forming the liquid acid. 
 This acid contains about 43 per cent of hydrogen chloride, 
 and has a specific gravity of 1*21; when heated it evolves 
 hydrochloric acid gas, until, under the ordinary atmospheric 
 pressure, the solution has a specific gravity of 1*104, and 
 contains 20 '22 per cent of the gas ; then the boiling point 
 remains stationary at 110, and the liquid distills over un- 
 changed. 
 
 Fig. 12. Commercial Preparation of HC1. 
 
 The composition of hydrogen chloride may be determined 
 by analysis. If two volumes of the gas be acted on by potas- 
 sium, only one volume remains and that is hydrogen. In a 
 similar way the electrolysis of a solution of hydrogen chloride 
 
116 ixoita.iMc r ///;. 
 
 *> 
 
 yields equal volumes of chlorine and of hydrogen. Hence, 
 since this substance contains equal volumes of hydrogen and 
 chlorine, there must be 35*37 units of mass of chlorine for 
 every unit of mass of hydrogen. 
 
 EXPERIMENTS. The solubility of hydrogen chloride in water, and 
 at the same time its acidity, may be shown by removing .the stopper 
 of a tall cylinder filled with the dry gas, beneath the surface of water 
 colored with blue litmus solution. On agitating the vessel a little, the 
 water enters as if into a vacuum, the cylinder being not (infrequently 
 broken. 
 
 On cooling the concentrated solution to 22, a compound with 
 water separates in the form of crystals having the formula HC1(H 2 O) 2 . 
 
 156. Uses. Hydrochloric acid is manufactured on an 
 immense scale in the arts, chiefly as a waste product in the 
 soda industry. The salt is treated with sulphuric acid in 
 cast iron cylinders placed in a furnace, as shown in Fig. 12, 
 and the gas as evolved is condensed in water contained in 
 large Woulfe bottles made of earthenware. It is used for 
 various minor purposes in the chemical arts. 
 
 2. BROMINE, IOL>INE, AND FLUORINE. 
 
 BROMINE. Symbol Br. Atomic mass 79*76. Valence I, V, 
 and VII. Specific gravity 3*187 at 0. Relative demity of 
 vapor 79*76. Molecular weight 159*5. Molecular volume 2. 
 The mass of 1 liter of bromine-vapor at is 7*15 grams 
 (79*76 criihs). 
 
 157. History. Bromine was discovered in the water 
 of the Mediterranean sea by Balard, in 1826. On account 
 of its disagreeable odor, he gave it the name bromine, from 
 Ppwtjun;, stench. 
 
 158. Preparation. On evaporating the water of many 
 saline springs, the salt crystallizes out, and there is left a 
 solution of the more soluble salts called the mother-liquor 
 or bittern which is rich in bromides. By heating this bit- 
 
PROPERTIES OF BROMINE AND IODINE. 117 
 
 tern with manganese di-oxide and sulphuric acid, the chlo- 
 rides in it are decomposed, yielding chlorine, which, in its 
 turn, sets the bromine free from the bromides. The vapors 
 of the bromine are led into a cooled receiver, where they 
 condense into a liquid. 
 
 159. Properties. Bromine is a heavy, dark brownish- 
 red liquid, of a disagreeable odor, somewhat recalling that 
 of chlorine. At a temperature of 63 it boils, and is con- 
 verted into a deep red vapor which is five and one half times 
 denser than air. Cooled to 22, it becomes a dark, lead- 
 gray crystalline solid, with a metallic luster. It is but slightly 
 soluble in water, thirty-three parts of which dissolve, at 15, 
 but one part of bromine. 
 
 Chemically it is similar to chlorine, but less active. Hence 
 chlorine sets it free from its combination. Several of the 
 metals burn in its vapor, and it exerts a decided bleaching 
 action. It is an active corrosive poison. 
 
 Bromine colors starch yellow ; and a bromide in aqueous 
 solution precipitates silver from its solutions, as yellow silver 
 bromide. It is used principally in photography and in med- 
 icine. 
 
 IODINE. Symbol I. Atomic mass 126 '54. Valence I, III, V, 
 and VII. Specific gravity 4'95. Relative vapor-demity 126 '54. 
 Molecular mass 253*08. Molecular volume 2. The mass of 
 1 liter of iodine-vapor at is 11*37 grams (126'54 criths). 
 
 160. History. On the coasts of Scotland and Normandy 
 large masses of sea-weeds were formerly burned in order to 
 extract the soda which they contain. The semi-fused ash 
 called kelp or varec was dissolved in water and the soda 
 salts crystallized out. It was in the mother-liquor thus ob- 
 tained that iodine was first discovered by Courtois in 1811. 
 Its elementary character was determined by Davy and G-ay- 
 Lussac in 1813. Its name is from Mys, violet-colored, in 
 allusion to the beautiful color of its vapor. 
 
 
118 I \OUGAXIC CHEMISTRY. 
 
 1O1. Preparation. It is prepared commercially in the 
 same way as bromine, by distilling the mother-liquors just 
 mentioned with manganese di-oxide and sulphuric acid, and 
 condensing the vapors ; or by passing chlorine or nitrous 
 acid through the mother-liquors, when the iodine will fall as 
 a precipitate. 
 
 1G2. Properties. Iodine is a bluish-black solid, having 
 a metallic luster, and crystallizing in rhombic scales, or, not 
 infrequently, in well-defined ortho-rhombic octahedrons, Fig. 
 13. Heated to 107 it melts, and at 180 boils, evolving a 
 dense, magnificent violet vapor, which 
 is 8 '72 times heavier than air, and is 
 therefore the heaviest vapor known. 
 At 1500, however, the relative density 
 of the vapor is reduced one half; and 
 hence the molecule is monatomic. It 
 Fig. is. crystals of iodine. ** onl >; Rightly soluble in water, one 
 part of iodine requiring 7,000 parts of 
 
 water at ordinary temperatures to dissolve it. It dissolves 
 readily in alcohol, ether, carbon disulphide and chloroform ; 
 and also in aqueous solutions of potassium iodide. 
 
 In chemical activity it is third in the series, being next to 
 bromine. It bleaches but faintly, if at all, in full sunlight, 
 but combines directly with the metals, forming iodides. It 
 stains the skin yellow, but is not an active poison. 
 
 Starch is a characteristic reagent for free iodine. It strikes 
 with it a deep blue color, which is so intense that one part 
 of iodine may be detected by it in 300,000 parts of water. 
 The most delicate test for iodine is the purple-red color it 
 produces when dissolved in carbon disnlphide. One part of 
 iodine in 1,000,000 parts of water may be detected in this 
 way. Soluble iodides produce characteristic precipitates with 
 mercurous, mercuric, and lead salts. 
 
 EXPERIMENTS. The process of obtaining iodine maybe illustrated 
 by adding to a solution of potassium iodide contained in a test-tube n 
 
I'UEPAKATION AND PJiOrKRTIES OF FLUORINE. 119 
 
 few drops of chlorine-water. The liquid becomes brown in color from 
 the iodine set free, and upon agitating it with ether, the iodine is dis- 
 solved by the ether and forms a dark brown layer above, while the 
 solution below is colorless. Upon pouring off the ether and agitating 
 it with a little solution of potassium hydrate, potassium iodide is 
 formed and the ether is decolorized. 
 
 The fumes of iodine are conveniently exhibited by throwing some 
 iodine upon a heated brick, and then covering the whole with a large 
 bell-glass. To show its reaction with starch, add a drop of the alco- 
 holic solution to a very dilute solution of starch contained in a tall 
 jar. The blue color, upon agitation, will penetrate the entire mass.*" 
 This experiment may be modified by adding a few drops of potassium 
 iodide to a dilute solution of starch, and then a few drops of chlorine- 
 water. The iodine does not color the starch until set free by the 
 chlorine, when the blue appears. 
 
 Add a few drops of potassium iodide to some water contained in 
 each of three tall test-glasses. Upon dropping into the first a little 
 of a solution of lead acetate, a brilliant yellow precipitate of lead 
 iodide is obtained. The second, treated with a few drops of mercu- 
 rous nitrate, gives a bright yellowish-green precipitate of mercurous 
 iodide. While the third, upon the addition of a little mercuric chlo- 
 ride, gives scarlet mercuric iodide. 
 
 163. Uses. Iodine is largely used in medicine, both free 
 and in combination. It is particularly serviceable in gland- 
 ular affections. It is also used extensively in photography 
 and in the preparation of aniline colors. 
 
 FLUORINE. Symbol F. Atomic mass 19 '06. Valence III (?). 
 Molecular mass 38*12 (?). Molecular volume 2 (?). Relative 
 density 19'06 (?). The mass of 1 liter at is 1-7 grams 
 (19-06 criths) (?). 
 
 164. Preparation and Properties. The mineral known 
 as fluorite, fluor or Derbyshire spar, is a compound of fluor- 
 ine with calcium, CaF 2 ; and the mineral cryolite is sodio- 
 alumiimm fluoride, Na. { AlF (i . From either of these minerals 
 hydrogen - potassium fluoride may be prepared, and by the 
 action of heat on this, anhydrous hydrogen fluoride is ob- 
 
120 INORGANIC CHEMISTRY. 
 
 tained. By the electrolysis of this substance placed in a 
 V-tube of platinum and cooled to 23 by boiling meihyl 
 chloride, Moissan obtained at the positive electrode a color- 
 less gas, having an odor like that of hypochlorous acid, and 
 possessed of an extraordinary activity. It unites directly 
 with hydrogen even in the dark, and decomposes water read- 
 ily, setting free ozonized oxygen. Sulphur, selenium, phos- 
 phorus, iodine, arsenic, antimony, silicon, boron, potassium, 
 and sodium take fire in it spontaneously. Potassium chlo- 
 ride and iodide are attacked by it when melted, the chlorine 
 and iodine being set free. Carbon disulphide is inflamed by 
 it ; and carbon tetrachloride evolves chlorine when this gas 
 is led into it. Organic substances are violently attacked and 
 inflamed in it. Quantitative experiments with iron showed 
 the absence of every other substance, and proved the gas 
 thus obtained to be fluorine. It therefore appears that the 
 activity of fluorine surpasses that of all the other elements. 
 
 By igniting platinum fluoride, Moissan has obtained fluor- 
 ine in a purer form. Its name comes from that of the min- 
 eral fluor spar just mentioned. Fluorite comes from the 
 Latin fluo, I flow, because it is used as a flux in the reduc- 
 tion of metals. 
 
 HYDROBROMIC, HYDRIODIC AND HYDROFLUORIC ACIDS. 
 
 165. Hydrogen Bromide or Hydrobromic Acid. 
 
 Formula HBr. Molecular mass 80'76. Molecular volume 2. 
 Relative density 40-38. 
 
 Hydrogen bromide may be obtained directly by passing a 
 mixture of hydrogen and bromine vapor over heated plati- 
 num finely divided, or indirectly by acting upon phosphorus 
 with bromine in presence of water. The phosphorus and 
 the bromine first unite to form phosphoric bromide accord- 
 ing to the following reaction : 
 
 P. + (Br,),,, - (PBr 5 ), 
 
A\l) HYI)/!OI<'Lr()t;lC ACIIW. 121 
 
 which, as fast as formed, is decomposed into phosphoric acid 
 and hydrobromic acid by the water present : 
 
 PBr 5 + (H. 2 0) 4 = H :) P0 4 + (HBr) 5 
 
 Hydrobromic acid is a colorless acid gas, fuming strongly 
 in moist air, and very soluble in water. Cooled to 73 it 
 becomes a liquid, and this at the temperature of 120 
 freezes. 
 
 1GO. Hydrogen Iodide or Hydriodic Acid. Formula 
 HI. Molecular mass 127 '54. Molecular volume 2. Relative 
 density 63 '77. 
 
 Hydrogen iodide may be readily prepared by heating to- 
 gether potassium iodide, iodine, and phosphorus, in presence 
 of water. The reaction is analogous to that above given for 
 hydrogen bromide : 
 
 (KI) 4 + P, + (I,) 5 + (H,0) 8 = 
 
 Potassium iodide. Phosphorus. Iodine. Water. 
 
 + (HK,(P0 4 )) 2 
 
 Ilydrlodic acid. Hydro-di-potassium phosphate. 
 
 Hydriodic acid is also a colorless gas, of specific gravity 
 4-41, which has an acid reaction and fumes in the air. It 
 is easily condensed to a liquid by a pressure of four atmos- 
 pheres at 0, and this liquid, cooled to 51, freezes to a 
 clear ice-like solid. It is as soluble in water as hydrogen 
 chloride, yielding at a solution of specific gravity 1'99. 
 A weaker solution, of specific gravity 1/7, distills over at 
 127, and contains 57 per cent of hydrogen iodide. This 
 solution is much used as a reducing reagent in organic chem- 
 istry. At 180 the gas decomposes into hydrogen and iodine. 
 
 167. Hydrofluoric Acid. Formula HF. Molecular mass 
 2O06. Molecular volume 2. Relative density 10. 
 
 Hydrogen fluoride is generally prepared by the action of 
 sulphuric acid upon calcium fluoride ; calcium sulphate and 
 hydrogen fluoride resulting : 
 
 CaF 2 + H. 2 (S0 4 ) = Ca(S0 4 ) + (HF), 
 
122 r\OI{(!.L\I(' CH 
 
 The process must be conducted iu a vessel of lead or of plat- 
 inum, as the gas readily attacks glass. It may be obtained 
 anhydrous by heating hydrogen-potassium fluoride. 
 
 Hydrofluoric acid is a colorless gas, which fumes in the 
 air and reacts strongly acid. The anhydrous gas condenses to 
 a liquid at 0, which boils at 19'5, and solidities at 102'5 
 as a transparent crystalline mass, fusing again at 92-30. 
 As obtained by the above reaction, it is a liquid having a 
 specific gravity of 1'06, owing to the presence of moisture. 
 The strong acid corrodes the skin powerfully, giving rise 
 to painful ulcers ; and the fumes, if inhaled, produce serious 
 irritation of the lungs. 
 
 At temperatures of 100 and above, hydrogen fluoride 
 has a molecular mass of 20*06, corresponding to the formula 
 HF ; but at about 30 its molecular mass is double this 
 value, or H 2 F. r It forms two classes of salts. I IMF, and 
 M. 2 F. 2 , in which M represents any metal ; and hence H.,F 2 
 represents probably the size of the molecule under ordinary 
 conditions. If fluorine be trivalent, the graphic formula of 
 hydrogen fluoride will be H F=F H, and that of cryolite 
 
 F=F-Na 
 
 AlfF=F-Na. 
 
 x F=F-Na 
 
 This substance when moist is distinguished from all others 
 by its remarkable property of attacking glass. With the 
 silicon of the glass the fluorine combines 
 to form a gaseous silicon fluoride. The 
 acid is used extensively in the arts for 
 etching glass, the highly ornamented door- 
 lights now so common being prepared by 
 this agent. Used as a liquid, the etched 
 surface is left smooth ; but when the gas 
 Etching by HF. is applied, the surface remains rough. 
 
 EXPERIMENT. Place some finely pulverized fluor-spar or cryolite 
 in a dish of lead, or preferably of platinum (Fig. 14), and pour upon it 
 
RELATIONS OF THE HALOUKX UlfOt'P. 123 
 
 some strong sulphuric acid. Cover the dish with a glass plate, upon 
 the lower side of which is a thin layer of wax, through which some 
 characters have been drawn with a iiii-e point. Place the whole on a 
 suitable stand and heat very gently for a few minutes. If now the 
 wax bo removed from the plate, the device drawn will be found etched 
 upon the glass. 
 
 3. RELATIONS OF THE HALOGEN GROUP. 
 
 168. Chlorine, bromine, and iodine constitute a closely 
 allied group of elements. Even in their physical properties, 
 there is a remarkable progression observable. As to physical 
 state, chlorine is a gas, bromine a liquid, iodine a solid; as 
 to color, chlorine is yellowish-green, bromine-vapor is brown, 
 iodine-vapor purple ; as to density, chlorine comes first, then 
 bromine, then iodine. All of them exist in the solid, liquid, 
 and gaseous forms, and change from one to the other at tem- 
 peratures not far apart. 
 
 The same is true of their chemical properties. The atomic 
 mass of bromine, 79*76, is nearly a mean between that of 
 
 126-54+35-37 
 chlorine and iodine, - =8U'yD. Chlorine is more 
 
 2 
 
 active than bromine, and bromine more than iodine. Indeed, 
 as is frequently the case with allied negative elements, the 
 chemism seems to vary inversely as the atomic weight. As 
 a whole, therefore, the group furnishes an excellent illustra- 
 tion of the periodic law (page 23). 
 
 Moreover, the hydrogen compounds of these elements are 
 similarly constituted and exhibit a similar gradation in prop- 
 erties. Their binary compounds with potassium and sodium 
 all resemble sea-salt ; hence these compounds are frequently 
 called haloid salts, and the elements halogens. 
 
124 IXOUGAMC CHEMISTRY. 
 
 EXERCISP]S. 
 
 1. In what compounds does chlorine occur in nature? 
 
 2. What volume does 32 grains of chlorine occupy? 
 
 3. What is the mass of 2356 cubic centimeters ? 
 
 4. How many grams of platinic chloride are required to give 25 
 grams of chlorine? To give 500 cubic centimeters? 
 
 5. How many liters of chlorine from 20 grams of hydrochloric 
 acid gas? How much manganese di-oxide is needed? 
 
 6. Liquid hydrochloric acid of specific gravity 1-20 contains 41 per 
 cent of HC1 ; one liter will yield how many liters of chlorine? 
 
 7. Commercial manganese di-oxide is seldom pure; what per cent 
 of MnO 2 does a sample contain, 30 grams of which heated with HC1, 
 gives 12-04 grams chlorine? 
 
 8. One kilogram of salt contains how many grams of chlorine? 
 
 9. One cubic centimeter salt contains how many cubic centimeters 
 of chlorine? (Specific gravity of salt 2-15.) 
 
 10. 150 liters of chlorine, at 15, and under 742 mm. pressure, are 
 required; how many grams of salt, of sulphuric acid, and of manga- 
 nese di-oxide, are necessary? 
 
 11. Give the formulas and names of the compounds of chlorine 
 with Ag' t Cu", Co", Sb'", B'", Sn'v, Ti'v, PV. 
 
 12. Calculate the percentage composition of silver chloride. 
 
 13. If ten c. c. of hydrogen diffuse into an atmosphere of chlorine 
 in one minute, how much chlorine will diffuse into the hydrogen in 
 the same time? 
 
 14. One cubic meter of HC1 contains what mass of Cl? 
 
 15. What volume of Cl will convert one liter of H into HC1? 
 
 16. Calculate the specific gravity of HC1 from its relative density. 
 
 17. What volume has one kilogram of HC1 gas? 
 
 18. One liter of HC1 passed over heated iron, yields what volume 
 of hydrogen? 
 
 19. Write the reaction which takes place in replacing the sodium 
 in salt by hydrogen. 
 
Kti. J25 
 
 20. How many kilograms of HC1 gas may be obtained from 28 
 kilograms of salt? How many liters? 
 
 21. How much sulphuric acid would be required to decompose it? 
 How much Na. 2 (SO 4 ) would be obtained? 
 
 22. One liter of liquid acid, specific gravity 1-21, contains how many 
 grams of HCl? How many liters? 
 
 23. How many kilograms of salt and of sulphuric acid are required 
 to produce 150 kilograms of liquid HCl, containing 24-24 per cent 
 of the gas ? 
 
 24. What mass of potassium hydrate is required to neutralize one 
 liter of hydrochloric acid gas? 
 
 25. Ten grams of the liquid acid precipitated 2-26 grains silver 
 chloride from 11 solution of silver; what percentage of HCl did the 
 solution contain? 
 
 2. 
 
 26. What is the mass of one c. c. bromine-vapor at 150 and 760 
 mm.? 
 
 27. Fifty c. c. of HBr decomposed by Na, gives what volume of H? 
 
 28. What volume of HBr will 10 grams of Br give? 
 
 29. If a liter of HI and one of chlorine be mixed together, what 
 will be the reaction? What will be the resulting gaseous volume and 
 what its composition? - 
 
 30. Show that the liquid hydriodic acid which contains 57 per cent 
 of HI, is not a definite hydrate. 
 
 31. What volume does 100 grams of H 2 F 2 occupy? 
 
 32. What volume of H is contained in 250 c. c of H 2 F 2 ? 
 
126 IXOliGAMC CHEMISTRY. 
 
 CHAPTER THIRD. 
 
 NEGATIVE DYADS. 
 S 1. OXYGEN. 
 
 Symbol O. Atomic mass 15 '96. Valence II. Relative demity 
 15-98. Molecular mass 31 '92. Molecular volume 2. The 
 mass of 1 liter at is 1*4298 grams (15 '96 critli*). 
 
 169. History. Oxygen was discovered by Priestley in 
 1774, who called it dephlogisticated air. The following year 
 Scheele discovered it independently, and gave it the name 
 empyreal air. Condorcet called it vital air. After the 
 overthrow of the theory of phlogiston by Lavoisier in 1781, 
 he gave it the name oxygen, from the Greek n-^ and ^>vw, 
 acid-former. 
 
 170. Occurrence. Oxygen is the most abundant ele- 
 ment in nature. It exists free in the atmosphere, of which 
 it forms a fifth part. Combined with other elements, it con- 
 stitutes two thirds of the entire globe. Water is eight ninths 
 oxygen, silica is one half oxygen, and alumina one third 
 oxygen, by weight. Fully one half of the weight of all 
 minerals, three quarters of the weight of all animals, and 
 four fifths of the weight of all vegetables, is oxygen. 
 
 171. Preparation. The atoms of compound molecules 
 containing oxygen may be re-arranged so as to yield simple 
 oxygen molecules : 
 
 I. By the action of some physical agent ; as 
 (a) Heat. Mercuric oxide, when exposed to a high tem- 
 perature, is resolved into mercury and oxygen : 
 
 Hg = O Hg O 
 
 becomes and l| 
 
 Hg = O Hg O 
 
I'll 
 
 (b) Light. Carbon di-oxide in the leaves of plants yields, 
 under the influence of sunlight, carbon and oxygen : 
 
 (CO,), = C 2 + (0 2 ) 2 
 
 (c) Electricity. In the electrolysis of oxygen compounds. 
 II. By the chemism of some other element assisted -by 
 
 some physical agent, generally heat : as when chlorine acts 
 upon the vapor of water at a red heat, producing hydrogen 
 chloride and oxygen : 
 
 (H. 2 0), + (Cl,) 2 = (HC1) 4 + 2 
 or upon calcium oxide or lime, producing calcium chloride 
 and oxygen : 
 
 (CaO) 2 + (C1 2 ) 2 = (CaCl 2 ) 2 
 
 O 
 
 EXPERIMENTS. The original experiment by which Priestley dis- 
 covered oxygen is an interesting one, and may be performed with the 
 apparatus shown in 
 Figure 15. An or- 
 dinary test -tube 
 coated with cop- 
 per by electro - de- 
 position for about 
 two inches from the 
 sealed end is used 
 to contain the mer- 
 curic oxide, and is 
 supported above 
 the gas-burner by a 
 
 clamp. By means 
 
 ITT Fig. 15. Preparation of Oxvgen from Mercuric Oxide. 
 
 of a cork and tube, 
 
 the oxygen as evolved is conducted beneath the mouth of a glass" 
 receiver filled with water, standing in the porcelain cistern^ _ 
 
 The usual method of obtaining oxygen is by heating potassium 
 chlorate, when the following reaction takes place: 
 
 (KC10 3 ) 2 : (KC1) 2 + (0 2 ), 
 
 But, since this Decomposition takes place at a very elevated tempera- 
 ture, and then witb almost explosive rapidity, it is found convenient 
 in practice to mix the salt with one fourth of its weight of some 
 metallic oxide, such as ferric or cupric oxide, or manganese di-oxide. 
 
128 
 
 Fig. 16. Preparation of Oxygen from Potas 
 Chlorate. 
 
 The mode in which these oxides act is not certainly known ; hut by 
 their use the oxygen is evolved with great uniformity and at a far 
 lower temperature, though it is not quite as pure. The oxide is ap- 
 parently unchanged by the operation. The apparatus employed is 
 
 shown in Fig. 16. The 1 
 mixture of potassium 
 chlorate and mangan- 
 ese di-oxide is placed 
 in a tlask standing in 
 a sand-bath, through 
 the cork of which a 
 bent glass tube passes 
 to convey the oxygen 
 as set free -to the cyl- 
 inder previously lilled 
 with water and stand- 
 hig in tlie water-cis- 
 tern. Upon applying 
 heat the gas is regularly evolved and may be collected for examina- 
 tion over water as shown in the figure, or, as it is heavier than air, by 
 displacement. When larger quantities of the gas are required, the 
 glass flask may be advantageously replaced by a conical flask with a 
 flat bottom made of sheet iron. 
 
 172. Properties. I. PHYSICAL. Oxygen is a colorless, 
 odorless, and tasteless gas. It is somewhat denser than air, 
 its specific gravity being 1-10563. Water dissolves it slightly, 
 100 volumes at taking up 4'1 volumes of oxygen. When 
 subjected to a pressure of 20 atmospheres, at a temperature 
 of 136 obtained by immersing it in boiling ethylene, it is 
 condensed to a transparent liquid having a density somewhat 
 less than that of water. Its critical temperature is 118 
 and its critical pressure is 50 atmospheres. Under these con- 
 ditions its density is 0'65, which increases to 0'87 at 139 
 and to 1-124 at 200. The liquid oxygen boils at 181 
 under a pressure of one atmosphere and at 198 under 
 a pressure of six millimeters. Its expansion-coefficient at 
 139 is 0-01706. Its refractive power is to that of air as 
 0-8616 to 1. li is strongly magnetic ; calling the magnetism 
 
PROPERTIES OF OXYGEN. 129 
 
 of iron 1,000,000, that of oxygen is 377. Hence the mag- 
 netic power of the atmospheric oxygen is quite appreciable, 
 being equal to that of a layer of iron covering the earth to 
 the thickness of O'l millimeter. The diurnal variations of 
 the magnetic needle are supposed to be due, at least par- 
 tially, to variations in the intensity of this magnetism, owing 
 to changes of temperature. 
 
 II. CHEMICAL. Oxygen is capable of entering into com- 
 bination with all the elements but fluorine. But, in the state 
 in which it is usually obtained, an elevation of temperature 
 is necessary to bring about this union. Combustion, in the 
 ordinary use of that term, is union with oxygen, attended 
 with light and heat. When hydrogen, sulphur, charcoal, 
 phosphorus, sodium, and iron, for example, are brought in 
 contact with oxygen at a suitable temperature, they burn, 
 evolving heat and light, and producing oxides of these sub- 
 stances. Oxygen is therefore an intensely active substance, 
 in which the rapidity of ordinary combustion is vastly in- 
 creased. It is respirable when pure, and produces a quick- 
 ening of the circulation. 
 
 EXPERIMENTS. A lighted candle burns far more brilliantly in 
 oxygen than in air. If it be blown out. leaving a spark upon th.e 
 wick, it is immediately rekindled in oxygen gas, with a slight puft'. 
 It is by this means indeed that this gas is recognized, a sliver of 
 wood with a spark upon the end bursting into flame in oxygen. In 
 this way ajar filling with the gas by displacement may be from time 
 to time tested. 
 
 A piece of charcoal that from oak or spruce is best having a 
 spark upon it, bursts into vivid combustion when placed in a jar 
 of oxygen. Sulphur, lighted and introduced in a combustion-spoon; 
 burns with a bright blue flame. Sodium, heated to redness, burns 
 with a dazzling light. Iron used in the form of watch spring or 
 of small wire, to which the end of a match is tied burns in oxygen 
 with great activity. 
 
 The most brilliant experiment with oxygen is the combustion in 
 it of phosphorus. A very neat apparatus for this purpose is shown 
 in Fig. 17, A light wire tripod has a ring at its upper part for sup- 
 
130 lyoituAxir CHKMISTKY. 
 
 porting a globe to contain the gas, and just below it a shallow cup, 
 containing water, into which the neck of the globe enters. From the 
 center of this cup rises a wire crowned by a small 
 hemispherical cup to receive the phosphorus. The 
 globe is filled about four fifths with oxygen by dis- 
 placement, and is then inverted on the stand. When 
 all is ready, a piece of phosphorus is cut from a 
 solid stick, and very thoroughly dried between sheets 
 of blotting or filtering paper. The globe is raised, 
 the piece of phosphorus dropped into the cup, in- 
 flamed by a hot wire, and the globe replaced. The 
 combustion is at once exceedingly vivid ; but in a few 
 seconds the phosphorus becomes volatilized by the 
 heat, and then burns throughout the entire mass of 
 Oxygen. ^he oxygen with a brilliance almost inconceivable. 
 
 If now, after cooling, water be added to the jars in which these 
 combustions have occurred, a direct union will take place between 
 the water and the oxide produced. Carbon produces carbon di-oxide; 
 sulphur, sulphurous oxide; sodium, sodium oxide; iron, tri-ferric tetr- 
 oxide; and phosphorus, phosphoric oxide. With water, the negative 
 oxides of carbon, sulphur, and phosphorus yield carbonic, sulphurous, 
 and phosphoric acids; and upon testing the water with a solution of 
 blue litmus, it will be found to be reddened. With water the positive 
 oxide of sodium yields sodium base, and this turns a solution of red 
 litmus blue. The oxide of iron produced does not form hydrates, and 
 
 hence in this jar the litmus is unaffected. 
 
 * 
 
 173. Uses. Oxygen is used in the arts for increasing 
 the intensity of combustion, for purposes either of heat or 
 light. Various methods have been proposed for its manu- 
 facture from the air on the large scale, the best of which 
 are: (1) Tessie du Motay's, which consists, first, in passing 
 pure air over a heated mixture of manganese di-oxide and 
 sodium hydroxide, producing by its oxygen sodium manga- 
 nate ; and second, in heating this manganate still higher, by 
 which, with the aid of a current of steam, it is decomposed 
 into the original materials again, setting the oxygen free. 
 (2) Mallet's, in which cuprous chloride is oxidized by pass- 
 ing air over it at a high temperature, to cupryl chloride, 
 
HISTOIfY OF <)/,<)\K. 131 
 
 which at a higher temperature becomes cuprous chloride and 
 oxygen again. (3) Boussingault's, which consists in passing- 
 moist air over heated barium oxide, whereby it is oxidized to 
 barium peroxide ; and then raising the temperature of this 
 peroxide to 400, by which it is decomposed into barium 
 oxide and oxygen. And (4) Deville's, which consists in the 
 decomposition of sulphuric acid by heat. 
 
 In the natural world, the uses of oxygen are well-nigh 
 infinite. Diluted with nitrogen in the air, it is continually 
 entering and leaving chemical combinations, setting free in 
 the former and absorbing in the latter enormous stores of 
 energy. It is by the oxygen of respiration that the energy 
 of living beings is set free from their food ; it is by the sep- 
 aration again of oxygen by the sunlight that that energy is 
 stored up anew in this food. Faraday has calculated that 
 6,000,000,000 pounds of oxygen are daily consumed in the 
 respiration of animals; and that the daily consumption of 
 oxygen for all purposes whatever reaches the enormous sum 
 of 7,142,857 tons! We have not, however, to fear an ex- 
 haustion of the supply, since the air of the globe, were no 
 oxygen added to it, contains enough of this gas to supply 
 this enormous demand for 480,000 years. 
 
 OZONE. Molecular formula O. r Molecular mass 47 '88. Molec- 
 ular volume 2. Relative density 23*94. The mass of 1 liter 
 at is 2-145 grams (23 '94 criths). 
 
 174. History. Oxygen, like chlorine, is capable of ex- 
 isting in both passive and active states. The passive condi- 
 tion is the one we have just considered. The active condi- 
 tion is termed ozone. As early as 1785, von Marum no- 
 ticed that oxygen, upon being electrified, acquired an odor 
 strongly resembling that perceived after a stroke of light- 
 ning, and usually termed "sulphurous." It was not until 
 1840, however, that any accurate experiments were made on 
 the subject. Then Schonbein noticed the similarity between 
 
132 IXORGAXIC CHEMTSTRY. 
 
 the electrical odor and that produced in the electrolysis of 
 water and in the slow oxidation of phosphorus and of sul- 
 phur ; and showed that in each of these cases the substance 
 produced turned paper moistened with a solution of potas- 
 sium iodide and starch, to a deep blue. The same year Ma- 
 rig-nac and De la Rive proved this substance to be modified 
 'oxygen. In 1852, Becquerel and Fremy showed that pure 
 oxygen could be entirely converted into ozone. In I860, 
 Andrews and Tait showed that a contraction of volume 
 took place when oxygen became ozone ; and in the same 
 year Soret showed that oil of turpentine absorbed the entire 
 ozone molecule, and in this way determined its relative den- 
 sity ; confirming his results in 1867 by the method of diffu- 
 sion of gases. The same year Andrews suggested that the 
 substance in the air which affected test-papers was ozone. 
 175. Preparation. Oxygen may be condensed to ozone : 
 
 I. By physical methods ; as 
 
 (a) Heat; as when a spiral of platinum wire is heated 
 in air. 
 
 (b) Light ; as when essential oils become strongly ozon- 
 ized in the sunlight. Or, as when the oxygen set free from 
 growing plants by sunlight, contains ozone. 
 
 ( c) Electricity ; 1st, by the electric silent discharge through 
 oxygen; 2d, in the electrolysis of water acidulated with sul- 
 phuric and chromic acids. 
 
 II. By the chemical process of slow combustion, and in 
 some cases, of active combustion also. And by the decom- 
 position of barium peroxide and potassium permanganate by 
 sulphuric acid. 
 
 EXPERIMENTS. For obtaining ozone by the action of the silent 
 electric discharge, the apparatus of Siemens (Fig. 18) is the most sat- 
 isfactory. As shown in the diagram above the cut, it consists of an 
 inner and an outer tuhe of glass, the inner surface of the inner tube 
 and the outer surface of the outer tube being covered with tin-foil. 
 Between the two tubes a slow current of pure dry ami well cooled 
 oxygen passes, while the two metal surfaces are connected with an 
 
PREPARATION OF OZOXK. 
 
 133 
 
 active induction coil. In this way 15 per cent of the oxygen may be 
 converted into ozone, a far larger amount than by any other method. 
 To show the contraction in volume when oxygen is converted into 
 ozone, the oxygen may be 
 contained in a cylindrical 
 bulb having a long, nar- 
 row neck bent into a U- 
 form. Through the walls 
 of the cylinder two plati- 
 num wires pass, and in 
 the bend of the U-tube a 
 little sulphuric acid is 
 
 Fig. 18. Siemeus's Tube for Ozonizing Oxygen. 
 
 placed. On passing the 
 spark through the gas by 
 means of the platinum wires, the oxygen is ozonized and the diminu- 
 tion in volume is shown by the rise of the sulphuric-acid column on 
 the bulb side of the U-tube. On heating the bulb to 290, the ozone 
 is reconverted into oxygen and the original volume is restored. By 
 absorbing the ozone by oil of turpentine, the volume of ozone pro- 
 duced may be determined; and hence its relative density. 
 
 A small flask half full of oil of turpentine, exposed freely to the 
 air and full sunlight for many weeks, acquires powerful ozonizing 
 properties. Sometimes the ozone is directly given up to other bodies; 
 but often it is not so surrendered, except by the intervention of a 
 third body, called therefore an ozone-carrier. Platinum sponge and 
 
 fl 
 
 
 ferrous salts act as such carriers; and blood 
 corpuscles are specially active. 
 
 To produce ozone by the slow oxidation of 
 phosphorus, place in a perfectly clean and spa- 
 cious gas-jar, a piece of phosphorus a centime- 
 ter in diameter and three or four long, previ- 
 ously scraped clean, and pour in water enough 
 to half cover it. The jar is then loosely stop- 
 pered and left to itself, at the ordinary tempera- 
 ture, for several hours. The air in the jar will 
 then be found strongly ozonized. 
 
 To produce ozone by the slow combustion 
 of ether, a few drops of ether are poured into a 
 beaker, as shown in Fig. 19, across the top of which is placed a rod 
 on which hang two slips of test-paper, one of blue litmus for acids, 
 the other for ozone. If now a glass rod, previously heated to a high 
 
 ' 1Q 
 
 Fig. 19. Ozone by Slow 
 Combustion of Ether. 
 
Io4 IXftlKtANIC CHEMISTRY. 
 
 temperature, be thrust into the jar, the ether will undergo slow com- 
 bustion, generating acid-vapors which redden the litmus paper, while 
 the ozone, which is formed at the same time, will turn the other paper 
 blue. 
 
 If a vigorous blast of air be directed from a glass tube through 
 the extreme top of the flame of a Bunsen gas-burner into a capacious 
 beaker, the air in the beaker will give the reaction for ozone ; an evi- 
 dence that it is produced in rapid combustion. 
 
 176. Properties. Physically, ozoiie is like oxygen, ex- 
 cept in density ; it is half as dense again as that gas. When 
 ozonized oxygen is cooled to 181 '4 by placing it in liquid 
 oxygen at atmospheric pressure, ozone is easily obtained as 
 a dark blue liquid, transparent in thin layers, but almost 
 opaque in a layer two millimeters thick. Its boiling point is 
 106. It yields a bluish gas on evaporation, which re- 
 condenses on immersion in liquid ethylene. 
 
 Chemically, too, it is like oxygen, in the fact that all its 
 compounds are oxides. In a word, it is oxygen with prop- 
 erties intensified ; it is active oxygen. It has a bluish color 
 and a strong odor, which is said to resemble that of weak 
 chlorine ; hence its name, from o!>, to smell. At a temper- 
 ature of 290 it is reconverted into ordinary oxygen. Its 
 most remarkable property is its powerful oxidizing action 
 even at ordinary temperatures. It bleaches strongly, carries 
 silver up to the peroxide, and is very poisonous to animal 
 life, on account of its irritating action upon the mucous sur- 
 faces. It is soluble only in oil of turpentine or oil of cinna- 
 mon. It decomposes potassium iodide, oxidizing the potas- 
 sium and setting the iodine free. 
 
 When ozone oxidizes a substance, there is no change in 
 volume, although the ozone itself disappears, the third atom 
 of oxygen alone entering into combination. The production 
 of ozone from oxygen is an endothermic reaction : 
 
 (O 2 ) 2 + O 2 = (O 3 ) 2 72,400 water-gram degrees. 
 Hence energy must be added to the oxygen to convert it 
 
OCCURRENCE OF OZONE. 135 
 
 into ozone ; the increased activity of ozone is thus accounted 
 for, as well as its instability. 
 
 177. Tests. Schonbein's test consists of paper moistened 
 with a dilute solution of potassium iodide and starch. The 
 iodine is set free by the ozone, and colors the starch deep 
 blue. Fremy's test is paper moistened with an alcoholic 
 tincture of guaiacum ; it is turned light blue by ozone. Pa- 
 per moistened with manganous sulphate, or lead hydrate, be- 
 comes dark brown' or black in ozone. The most distinctive 
 test is metallic silver, which is converted by ozone into the 
 brown peroxide. 
 
 EXPERIMENTS. To prepare Schonbein's test-paper, one part of 
 pure potassium iodide is dissolved in two hundred parts of water, the 
 solution gently heated, ten parts of line starch gradually added, and 
 the heating continued until the whole becomes homogeneous. Slips 
 of filtering paper are then drawn through the solution and dried in 
 the air. They must be kept in a closely stoppered bottle. When one 
 of these slips is moistened and exposed to an atmosphere containing 
 ozone, it becomes deep blue. The bleaching action of ozone may be 
 shown by agitating in a jar of air ozonized by phosphorus a little 
 very dilute solution of indigo. It is at once decolorized. 
 
 178. Occurrence and Uses. Ozone is found free in 
 the air, in small quantities, especially after a thunder-storm. 
 It is also produced by decay, and probably by plant growth. 
 It has been supposed to oxidize and destroy impurities in the 
 air. One volume of air containing g-oVo ^ ozoue will purify 
 540 volumes of putrid air. On the other hand, on account 
 of its irritating action when breathed, it has been assumed 
 to be the cause of influenzas, etc. But in the absence of 
 exact data, it is not possible to decide whether atmospheric 
 ozone performs any well-defined function. In the arts it has 
 been used as a disinfectant, and also as a bleaching agent. 
 
 It is probable that, while the molecule of oxygen is diat- 
 omic, that of ozone is triatomic, thus : 
 
 O = O 
 
 0-0 
 
 Oxygen. Ozone. 
 
136 JXORUAXIC CHEMISTRY. 
 
 So that while in the case of ozone we have another instance 
 of allotropism ozone being allotropic oxygen we have here 
 an instance in which the allotropism is evidently due to a con- 
 densation within the molecule. Hence the conclusion seems 
 reasonable that all allotropism may be due to a similar cause. 
 
 COMPOUNDS OF OXYGEN WITH HYDROGEN. 
 
 HYDROGEN OXIDE. Formula H.,O. Molecular mass 17.96. 
 Molecular volume 2. Relative density 8*98. The maw of 1 
 liter of water-vapor is 0'8064 grams (8*98 criths). Specific 
 gravity 1. Solidifies at 0. Boils at 100. Molecular majs 
 in the liquid state probably 35 '92. 
 
 179. History. Hydrogen oxide, or water, was consid- 
 ered to be an elementary substance until 1776, when Lavoi- 
 sier showed its" compound nature. Cavendish and Watt 
 in 1781, first proved its composition by synthesis. In 1805, 
 Humboldt and Gay-Lussac ascertained that the ratio of 
 its constituents by volume is as 2 : 1 ; and Berzelius and 
 Dulong- proved that the mass-ratio is as 1 : 8. 
 
 180. Occurrence. Water occurs abundantly diffused in 
 nature, both free and in combination. Natural waters are 
 seldom pure ; even the water which falls as rain contains 
 atmospheric impurities to an extent of 3 per cent or more. 
 It is essential to the life of plants and animals, and enters 
 into the composition of many mineral substances. Seven 
 eighths of the entire human body is water. 
 
 181. Preparation. Hydrogen oxide may be prepared 
 synthetically ; that is, by the direct union of its constituent 
 elements. The product of the combustion of hydrogen is 
 always water, as we have seen. (Fig. 6.) And when the 
 two gases are mixed together in the ratio of two volumes 
 of hydrogen to one of oxygen, they may be caused to unite 
 by a flame, by an electric spark, or by finely divided plati- 
 num. The heat evolved by their union is very great ; when 
 
HYDROGEN OXIDE. 
 
 137 
 
 the two gases are burned together in the above proportions 
 from a jet, they give the most intense heat which can be ob- 
 tained by combustion. This experiment was first made by 
 Hare, of Philadelphia, in 1801 ; and the apparatus is called 
 the compound or oxy-hydrogen blowpipe. 
 
 EXPERIMENTS. To show the production of water by the combus- 
 tion of hydrogen, the experiment described under hydrogen may be 
 repeated. In Fourcroy's exper- 
 iment the gas continued to burn 
 for a week, consuming 37,500 
 cubic inches of oxygen and hy- 
 drogen and producing 15 ounces 
 of pure water. 
 
 To show the union of the 
 mixed gases by flame, a mass 
 of soap-bubbles may be blown 
 in a metallic dish containing 
 soap and water, by a bubble- 
 pipe attached to a gas-bag con- 
 taining one volume of oxygen 
 to two of hydrogen. On apply- 
 ing a flame (Fig. 21) the gnses 
 explode with a loud report. 
 
 For the purpose of measuring exactly the proportions in which the 
 gases unite, an instrument called a eudiometer is employed. 
 
 Fig. 22 represents the form proposed by Ure; it is simply a U- 
 
 shaped tube of glass which 
 is closed at one end, the 
 closed limb being gradu- 
 ated, and pierced near its 
 extremity by two platinum 
 wires. This limb is to be 
 filled with water, and then 
 a given quantity of pure 
 oxygen, say 20 cubic centi- 
 Fig. 21. Explosion of mixed Oxygen and Hy- meters is to be introduced 
 drogen gases. from a delivery-tube; 50 
 
 cubic centimeters of hydrogen are then similarly introduced all 
 measurements being made when the level of the liquid is the same in 
 
 Fig. 20. Water from the combustion of 
 Hydrogen. 
 
 
138 
 
 
 both limbs the open end is closed firmly by the thumb, as shown 
 in the figure a cushion of air being left between it and the liquid - 
 and a spark passed through the mixed gases by 
 means of the platinum wires. Upon restoring 
 the level of the liquid by adding water, 10 cu- 
 bic centimeters of gas will be left, which, on 
 examination, will be found to be pure hydrogen. 
 Hence 20 volumes of oxygen have united with 
 40 of hydrogen to form water. But this is the 
 ratio of 1 : "2, which theory requires. 
 
 The remarkable action of spongy platinum 
 in causing the union of oxygen and hydrogen 
 Pig. 22. lire's Eudiom- gases, may be shown by holding a piece of this 
 metal or what answers equally well, a piece of 
 
 asbestus previously moistened with strong platinic chloride solution 
 and heated to redness over a jet from which hydrogen is issuing. 
 The mass becomes at once red-hot and fires the gas. This effect is 
 attributed to the enormous surface-attraction which platinum, in this 
 form, has for gaseous substances. Exposed to the air, platinum-sponge 
 condenses oxygen in this way within it, perhaps to the state of a liquid. 
 When now it is exposed to hydrogen, it condenses this gas also; thus 
 bringing them together and causing their union. 
 
 The great heat evolved by burning oxygen and hydrogen gases 
 together requires for its production a concentric jet, consisting of an 
 inner tube carrying the oxygen, and outside of this a second tube be- 
 tween which and the first the hydrogen passes. The two gases must 
 be brought from separate gas-holders. The hydrogen is first lighted; 
 it burns with a large yet pale flame. On admitting the oxygen, this 
 flame becomes smaller, and is drawn out very long and fine, being 
 altered also in color. If this flame be directed upon various metals 
 contained in small cups of charcoal, they may be melted and burned, 
 each with its characteristic color. The brilliance of the experiment 
 is much heightened, in many cases, by shutting off the hydrogen and 
 allowing the combustion to take place in the oxygen alone. A watch- 
 spring or a smalt file, introduced into the flame, burns with vivid 
 scintillations. A piece of cast-iron on charcoal gives, after melting 
 it and shutting off the hydrogen, a superb pyrotechnical effect. On 
 introducing some infusible substance, as a pipe-stem, a cylinder of 
 magnesia or zirconia, or still better, one of lime, the light emitted is 
 dazzling. This light was first utilized practically in the trigonomet- 
 rical survey of Great Britain, by Lieut. Drummond, when it was seen 
 
ANALYSIS OF WATER. 
 
 139 
 
 108 miles in full daylight. It is sometimes called the Drummond 
 light; but is more properly called the calcium or oxy-hydrogen light. 
 By means of an oxy-hydrogen flame 3,200 ounces of platinum have 
 been melted in one operation. 
 
 But not only may the composition of water be established 
 by synthesis, it may be equally well determined by analysis. 
 For this purpose both direct and indirect means may be em- 
 ployed. 
 
 EXPERIMENTS. In the sodium experiment (Fig. 1) the hydrogen 
 set free must have been derived from the water on which the sodium 
 acted. If a little solution of red litmus be added to the water after 
 the experiment, it will be blued. A base must therefore have been 
 produced by the sodium; but a base contains oxygen, which oxygen 
 must also have come from the water. In this way 
 the composition of water may be established by 
 an indirect analysis. 
 
 To analyze water directly, it may be submitted 
 to the action of electricity. But as water itself is 
 not decomposed by this agent, a secondary action 
 must be made use of. A little sulphuric acid is 
 added to the water ; this is decomposed by the elec- 
 tric current, and reacts upon the water, separating 
 it into its constituents. A convenient apparatus 
 for this purpose is shown in Fig. 28. Two tubes 
 closed at one end and filled with water are 
 suspended with their mouths beneath the 
 surface of some acidulated water contained 
 in the glass dish below. Through the 
 sides of this dish two wires pass, each 
 terminating in a plate of platinum seen 
 beneath the open ends of the tubes. On 
 connecting these wires with a Bunsen's or Grove's battery of 6 or 8 
 cells, a torrent of gas-bubbles rises from each platinum plate into the 
 tube placed above it. It will soon be noticed that the tube over the 
 negative electrode fills twice as rapidly as the other; and on testing 
 the gas in each, when the tubes are both full, the gas in this tube will 
 be found to be hydrogen, while that in the other is oxygen. Water 
 contains therefore 2 volumes of hydrogen and 1 volume of oxygen. 
 And as the mass of oxygen is 16 times that of hydrogen, the mass- 
 
 Fig. 23. Decomposition of 
 Water by Electricity. 
 
140 
 
 ratio must be as 2 : 16 or as 1 : 8; or more exactly, water consists of 
 of 88-89 per cent of oxygen and 11-11 per cent of hydrogen. 
 
 182. Properties. Hydrogen oxide is a limpid liquid, 
 without odor or taste. lu thiu layers it is colorless, but in 
 thick layers it is distinctly blue. It is neither acid nor alka- 
 line in its action upon vegetable colors, is a poor conductor 
 of heat and a non-conductor of electricity. It is 773 times 
 heavier than air at 0. It is the standard of specific gravity 
 for liquids, and is taken as the unit of mass in the decimal 
 system, the mass of one cubic centimeter of water at 4 
 being 1 gram ; hence the mass of one liter of water at the 
 same temperature is 1 kilogram. When cooled to 0, it solid- 
 ifies in crystals which are derived from the hexagonal prism, 
 and which are often very beautifully seen in snow-flakes, 
 Fig. 24. The melting-point of ice is lowered by '0075 for 
 
 Fig. 24. Snow Crystals. 
 
 every atmosphere increase of pressure. When heated to 
 100 under atmospheric pressure it is converted into vapor 
 called steam. The rate of its expansion by heat increases 
 slightly with the temperature ; though at 4 water reaches 
 its point of maximum density, and then, if cooled below this, 
 it expands until its solidifying point is reached. At the 
 moment of becoming solid it increases considerably in vol- 
 ume, 916 cubic centimeters of water becoming 1,000 of ice. 
 Its index of refraction at is 1'333. It is also the stand- 
 ard of specific heat, since it requires more heat to raise its 
 temperature a given number of degrees than any other solid 
 or liquid. In the form of steam it is a colorless gas, having 
 a relative density of 8 '98, or a specific gravity of 0-622, air 
 
CHEMICAL rUOPEKTIES OF WATER. 141 
 
 being 1. One volume of water yields 1,696 volumes of steam 
 at 100. The heat of liquefaction of water is 80-025 heat- 
 units. The heat of vaporization is 536 '5 heat-units. The 
 critical temperature is 370, and the critical pressure 195 '5 
 atmospheres. 
 
 Chemically, water is a very active substance. It enters 
 into combination directly with most positive and negative 
 oxides, forming bases with the former and acids with the 
 latter, evolving more or less heat. A familiar example of 
 this is the slaking of lime, a process which may be repre- 
 sented by the following equation : 
 
 CaO + H 2 = Ca"(OH) 2 
 
 Calcium oxide. Water. Calcium hydroxide. 
 
 Water also enters molecularly into the composition of 
 many crystalline substances, the amount appearing to in- 
 crease in proportion as the crystallization takes place in a 
 colder and more dilute solution. Calcium sulphate crystal- 
 lized takes two molecules, CaSO,, 2 aq. ; copper sulphate, 
 five, CuSO 4 , 5 aq. ; magnesium sulphate, seven, MgSO 4 , 7 
 aq. ; sodium sulphate, ten, Na.,SO 4 , 10 aq. ; and potassio- 
 aluminic sulphate (alum), twelve, KA1(SO 4 ) 2 , 12 aq. Such 
 crystals, when exposed to dry air, effloresce; i. e., lose this 
 water of crystallization and fall into a white powder. On 
 the other hand, some substances, in a moist atmosphere, 
 attract water and liquefy : this is called deliquescence. The 
 solvent power of water is very much greater than that of 
 any other liquid. Each substance which it dissolves, how- 
 ever, has a fixed limit of solubility, which depends upon 
 temperature, etc. Gaseous solubility is to a very large ex- 
 tent dependent upon atmospheric pressure also. Water is 
 obtained pure and free from dissolved foreign substances 
 only by distillation. 
 
 When water-vapor is produced from its constituent gases 
 without change of volume the synthetical reaction is 
 (H,) 2 + O 2 = (H,O). 2 -f 114,320 water-gram degrees; 
 
142 'INORU.IMC < 'II KM I WHY. 
 
 and hence water is highly exothermic and proportionately 
 stable. When the water is obtained as a liquid each gram 
 of hydrogen burned evolves 34,180 heat-units. Conversely 
 the decomposition of water is endothermic and requires this 
 quantity of heat to be furnished from without. The disso- 
 ciation of water is effected at 1000 and is half completed 
 at 2500. Moreover, heat-changes also accompany the act 
 of solution. Thus the solution of KC1, KBr and KI in 
 water absorbs 4,440, 5,080, and 5,110 units of heat respect- 
 ively; while the solution of Nal evolves 1,220, that of 
 BaBr 2 evolves 4,980, that of LiCl 8,440, that of Na 2 P 2 O 7 
 11,850, and that of KOH 13,290 heat-units, according to 
 Thomsen. 
 
 183. Natural Waters. The purest natural water which 
 can be obtained is that which falls as rain ; but even this is 
 contaminated with matters washed from the air. Other nat- 
 ural waters may be divided into potable (or drinkable), min- 
 eral, and saline waters. Of potable waters, river and lake 
 waters, especially such as are found in granite regions, are 
 the purest. That of Loch Katrine in Scotland, containing 
 but 2 grains of solid matter to the gallon, is one of the 
 purest waters known; while the purest water supplied to 
 any city in this country is that from Lake Cochituate which 
 supplies Boston, which contains but 3*11 grains in one gal- 
 lon. The Schuylkill water (Philadelphia) contains 3 50 
 grains ; Ridge wood (Brooklyn) 3 '92 ; the Croton (New York) 
 4-78; Lake Michigan (Chicago) 6'68; the water which sup- 
 plies Albany, 10-78 ; and that of the Thames, which supplies 
 London in part, 16'38 grains, in each gallon. Spring and 
 well waters are seldom as pure as surface waters, since they 
 have penetrated the ground and taken up solid impurities. 
 Thus the water of a well near Central Park, New York, 
 gave 43*54 grains; one in Schenectady, 49*21 grains; one 
 in Amsterdam, 69.93 grains ; and one in London, 99'97 grains 
 of solid matter to the gallon. Mineral waters are classified, 
 
// YDifoa /<:.y rKHoxiDK. 1 43 
 
 according to their prevailing constituents, into sulphurous, 
 chalybeate, alkaline, etc. The amount of solid matters which 
 they hold in solution varies very widely; the chalybeate 
 spring of Tunbridge Wells contains but 7 grains to the gal- 
 lon, while the Saratoga Seltzer spring contains over 400, one 
 of the springs at Vichy, 460, the High Rock spring at Sara- 
 toga, 628, and the artesian Lithia spring at Ballston, 1,233. 
 Saline waters, especially those of inland lakes with no outlet, 
 are most impure. Sea-water contains on an average, 2,500 
 grains of solid matter, the water of the Dead Sea 12,600 
 grains, and that of the Great Salt Lake 22,000 grains to the 
 gallon. 
 
 Water for drinking should be as pure as it is possible to 
 obtain it. Indeed, in some of our cities distilled water prop- 
 erly aerated is sold for table use. The effervescent table wa- 
 ters now largely used are of value in proportion as the water 
 of which they are made is pure. The most serious contami- 
 nation of water is that arising from sewage, coining either 
 from surface drainage or from soakage through the soil. 
 The greatest care should therefore be exercised in selecting 
 a source of water supply, to see that no such cause of impu- 
 rity exists. 
 
 HYDROGEN PEROXIDE. Free hydroxyl. Formula H.,O r 
 Graphic H O O H. Molecular mass 33'92. Specific 
 gravity of liquid, 1*452. 
 
 184. History. Hydrogen peroxide was discovered by 
 Thenard in 1818, and called by him oxygenated water. 
 
 185. Preparation and Properties. It is always pre- 
 pared from barium peroxide by the action of hydrochloric, 
 or, better, of carbonic acid. The reaction is : 
 
 BaO, + H 2 CO S = BaCO, + H,O 2 
 
 By adding the materials alternately, the water present soon 
 becomes saturated ; then, by evaporation over sulphuric acid, 
 
144 IXORGAXIC C 
 
 this water may be removed, thus leaving pure hydrogen per- 
 oxide. 
 
 It is always formed by slow oxidation in presence of moist- 
 ure ; the hydrogen peroxide thus produced being detected in 
 the liquid by proper means. It would appear that its pro- 
 duction under these conditions is to be viewed not as an oxi- 
 dation of water, but rather as due to the action of nascent 
 hydrogen upon oxygen. (Traube.) If air or oxygen be passed 
 through acidulated water undergoing electrolysis, hydrogen 
 peroxide appears at the negative or hydrogen electrode. 
 
 Hydrogen peroxide is a colorless syrupy liquid, of spe- 
 cific gravity 1'452. It does not solidify at 30, and may 
 be evaporated in vacuo unchanged. It begins to decompose 
 at 15, and at 100 it separates into water and oxygen with 
 almost explosive violence. It is more permanent if diluted 
 with water. It has a harsh taste, and whitens the skin when 
 placed upon it. It bleaches vegetable colors. 
 
 Hydrogen peroxide, as already mentioned (page 77), is an 
 endothermic compound, being formed with the absorption 
 of energy: 
 
 (H 2 O) 2 + O 2 = (H,O 2 ) 2 44,000 water-gram degrees. 
 
 Its activity is seen to be due to the increased amount of en- 
 ergy it contains over that existing in water. Moreover to 
 this cause is due its instability also. 
 
 Its most remarkable property is the facility with which it 
 evolves oxygen under certain conditions. It oxidizes sele- 
 nium, chromium and arsenic, converts lead sulphide into sul- 
 phate, and sets free iodine from hydrogen iodide. Metallic 
 platinum, gold, and silver, when finely divided, decompose 
 it almost with explosion ; their oxides, as well as the perox- 
 ides of lead and manganese, also decompose it, giving up a 
 part of their oxygen at the same time. Ozone is decomposed 
 by it, water and oxygen being the sole products. It is there- 
 fore at once an oxidizing and reducing agent. The similarity 
 
OX1DKH AM) ACIDS OF CHLORINE. 145 
 
 in its chemical properties to those of ozone arises doubtless 
 from the slight attraction between one of the atoms of oxy- 
 gen and the rest of the molecule. 
 
 EXPERIMENTS. The water surrounding the phosphorus in the 
 preparation of ozone (p. 133) contains hydrogen peroxide, and will 
 reduce a dilute solution of potassium permanganate, itself a strong 
 oxidizing agent. If to a solution containing hydrogen peroxide, a 
 few drops of a dilute solution of potassium chromate be added, and 
 the whole be agitated with ether, the ethereal layer which forms above 
 the liquid on standing will be blue from the presence of perchromic 
 acid. It turns Schonbein's test-paper blue, and also blues guaiacum 
 paper. Indigo is also decolorized by it. These reactions are not as 
 promptly produced by hydrogen peroxide as they are by ozone, un- 
 less a minute quantity of some carrier, such as ferrous sulphate, be 
 present. 
 
 Hydrogen peroxide exists in small quantity in the air and 
 may very readily be detected in freshly fallen rain-water or 
 snow. Its quantity varies from one twentieth of a milligram 
 to one milligram in a liter. The close similarity between its 
 reactions and those of ozone causes the one to be frequently 
 mistaken for the other. 
 
 OXIDES AND ACIDS OF CHLORINE. 
 
 186. The element chlorine, as already mentioned, may act 
 as a monad, a triad, a pentad, or a heptad. Its oxygen com- 
 pounds, together with their corresponding hydrates or acids, 
 are therefore as follows : 
 
 Hypochlorous oxide C1' 2 O Hypochlorous acid HCl'O 
 
 Chlorous oxide C1'" 2 O 3 Chlorous acid HCl^O, 
 
 Chloric oxide C1V 2 6 5 Chloric acid HC1VQ 3 
 
 Perchloric oxide Civn.,0. Perchloric acid HC1 VII O 4 
 
 Of these oxides, only the first two have been prepared. 
 Of the acids, all have been obtained. 
 
 187. Hypochlorous Oxide and Acid. Hypochlorous 
 oxide was discovered by Balard in 1834. It may be pre- 
 pared by passing dry chlorine gas over mercuric oxide : 
 
 HgO + C1 4 = HgCl 2 + C1,O 
 
146 IXOI:<;AM< CH 
 
 A yellow gas, of relative density 43*5, is obtained, which 
 condenses to a blood-red liquid at 0. This gas has a pene- 
 trating, chlorine-like odor, and is decomposed with explosion 
 by very slight causes, yielding two volumes of chlorine and 
 one of oxygen. It is very soluble in water, uniting with it 
 to form hypochlorous acid, Cl(OH), which retains the odor 
 of the oxide and is a powerful bleaching agent, twice as 
 active as chlorine. 
 
 Hypochlorites are prepared in the arts by exposing alkali 
 hydroxides to the action of chlorine gas. With sodium hy- 
 droxide, the reaction which takes place is as follows : 
 
 (HNaO), + Cl, = NaCIO + NaCl + H 2 O 
 
 By treating a hypochlorite with dilute nitric acid and 
 distilling, hypochlorous acid may be obtained. 
 
 HypocKlorites are used very largely in the arts as bleach- 
 ing agents; the so-called chloride of lime, a compound of 
 calcium chloride and calcium hypochlorite, being manufact- 
 ured for this purpose on an immense scale. 
 
 188. Chlorous Oxide and Acid. Chlorous oxide was 
 first described by Millon. It Is prepared by acting upon a 
 chlorate with nitric acid in presence of a reducing agent, 
 like arsenous oxide. It is a yellowish -green gas, having a 
 specific gravity of 2*65, bleaching indigo and litmus, and 
 soluble in one sixth its volume of water, forming chlorous 
 acid. It is condensed to a liquid by a cold of 20. It ex- 
 plodes when heated to 57, and also when brought in contact 
 with sulphur, phosphorus, or arsenic. 
 
 Chlorous acid, CIO(OH), combines slowly with bases, form- 
 ing chlorites, which are unstable, breaking up easily into 
 chlorates and chlorides. 
 
 189. Chlorine Tetr-oxide. C1,O, or O,Cl v -O-Cr"'O. 
 This oxide is intermediate between chlorous and chloric 
 oxides, and is decomposed by water and the alkalies into 
 chlorous and chloric acids. It was discovered by Davy, in 
 
CHLOUIC ACID. 147 
 
 1814, and is obtained by the action of sulphuric acid upon 
 potassium chlorate, at a low temperature. A dark-greenish 
 gas is evolved, which, strongly diluted, has a sweetish aro- 
 matic odor, and is strongly oxidizing in its action. At 20 
 it condenses to an orange-red liquid. It explodes with great 
 violence above 60, often spontaneously. 
 
 EXPERIMENTS. The vigor of its action on combustibles may be 
 shown by mixing together on a sheet of paper about a gram of finely 
 pulverized potassium chlorate and and an equal 
 quantity of fine sugar. Place the mixture on a 
 fragment of brick, and touch it with a glass rod 
 previously dipped in sulphuric acid. The chlo- 
 rine tetr-oxide thus set free causes a vivid com- 
 bustion of the entire mass. 
 
 Or, a gram of chlorate in crystals may be 
 placed at the bottom of a conical glass filled 
 with water (Fig. 25), a few small pieces of phos- 
 phorus added, and sulphuric acid allowed to Phosphorus^y (Jhlo- 
 come in contact with the salt, by means of a rine tetr-oxide. 
 
 pipette. The phosphorus at once takes fire in the chlorine tetr-oxide 
 gas evolved, and burns vividly. 
 
 19O. Chloric Acid. Chloric acid, C1O 2 (OH), was first 
 prepared by G-ay-Lussac. On passing chlorine through a 
 solution of potassium hydroxide, potassium chlorate and po- 
 tassium chloride are obtained, according to the equation : 
 
 (0,), + (HKO). = KC10 3 + (KC1). + (H,,0) 3 
 
 By adding to a solution of potassium chlorate, fluo- silicic 
 acid, or to one of barium chlorate, sulphuric acid, the potas- 
 sium or barium is separated, and there is left an aqueous 
 solution of chloric acid, which by concentration in vacuo 
 may be obtained as a colorless, syrupy, acid liquid, of spe- 
 cific gravity 1 '28, and containing about 40 per cent of HC1O. , 
 which decomposes above 40, and is a strongly oxidizing 
 agent. Sulphur, phosphorus, alcohol, paper, are at once in- 
 flamed by it. Its salts, the chlorates, are also active oxidiz- 
 
148 IXOHGAXIC Ct/EM/sr/fV. 
 
 ing agents. They are used for the preparation of oxygen, 
 and in detonating and pyrotechuical mixtures. 
 
 EXPERIMENTS. Mix carefully on paper half a gram of fine potas- 
 sium chlorate with quarter of a grain of sulphur. Wrap up the mass 
 in paper, place it on an anvil and strike it with a hammer. It will 
 explode violently. Many new explosives have been recently pro- 
 posed, consisting of potassium chlorate mixed with tannin, with cate- 
 chu, and with potassium ferrocyanide and sugar. They are all more 
 or less unstable and therefore dangerous. A mixture of amorphous 
 phosphorus and potassium chlorate sometimes detonates spontane- 
 ously. 
 
 191. Perchloric Acid. Perchloric acid, C1O 3 (OH), was 
 
 discovered by Stadion in 1815 ; it has been recently more 
 fully examined by Roscoe. On subjecting potassium chlo- 
 rate to heat, it becomes pasty at a certain stage of the proc- 
 ess, and ceases to evolve oxygen.. It is then a mixture of 
 potassium perchlorate and chloride, thus : 
 
 (KC1O 3 ) 2 = KC1O 4 + KC1 -f 3 
 
 By crystallization the difficultly - soluble perchlorate is ob- 
 tained pure ; and by distilling this with sulphuric acid, a 
 colorless fuming liquid condenses in the receiver, having a 
 specific gravity of 1*782 at 15. It does not solidify at 
 35. This acid is a powerful oxidizer ; it instantly ignites 
 wood or paper when thrown upon it, and is decomposed by 
 charcoal, with explosion. It is the most stable of the chlo- 
 rine acids. 
 
 OXIDES AND ACIDS OF BROMINE AND IODINE. 
 
 192. The analogy of bromine and iodine to chlorine is 
 shown also in the similarity of their oxides and acids to 
 those of that element. Theoretically, the series is the same, 
 though only a few members of it have as yet been obtained. 
 Of the bromine compounds, only the following are known : 
 
 Hypobromous acid HBr'O 
 
 Bromic acid 
 Perbromic acid 
 
XfK or s LLPH UR. 1 49 
 
 and of those of iodine, only those given below have been 
 
 prepared : 
 
 Hypoiodous acid HI'O 
 
 lodie oxide K 2 O 5 lodic acid HI V O 3 
 
 Periodic oxide I VII O Periodic acid 
 
 193. lodic Acid. lodic acid is the most important of 
 the bodies given above. It is prepared by the direct action 
 of oxidizing agents upon iodine, or by the simultaneous ac- 
 tion of chlorine and iodine upon water : 
 
 I, + (C1,) B 4 (H 2 0) 6 = (HIO s ) a + (HC1) 10 
 lodic acid is a colorless solid, of specific gravity 4*63, crys- 
 tallizing in ortho-rhombic prisms; at 170 it loses a mole- 
 cule of water, and becomes iodic oxide. 
 
 2. SULPHUR. 
 
 Symbol S. Atomic mass 31-98. Valence II, IV, VI. Rela- 
 tive density of vapor 31*98. Molecular mass 63 '96. Molec- 
 ular volume 2. Specific gravity of solid 2-04. The mass of 
 1 liter of sulphur vapor at a temperature of 1000 is 2 '86 
 grams (31*98 criths). 
 
 194. History. Sulphur has been known from the re- 
 motest times. 
 
 195. Occurrence. It is found free in many volcanic 
 regions, especially in Italy and Sicily. It occurs also in 
 combination, as a constituent of both binary and ternary 
 compounds. The sulphides of iron, copper, lead, zinc, anti- 
 mony, arsenic, and mercury, are well-known minerals ; as 
 tire also the sulphates of calcium, barium, strontium, mag- 
 nesium, and sodium. It forms an essential part of animal 
 tissues and exists to a considerable extent in those of vege- 
 tables. Its compounds cause the peculiar odor of crucifer- 
 ous and alliaceous plants, such as mustard and garlic. 
 
 Sicily and Italy yield annually 80,000 tons of sulphur, 
 ' 11 
 
150 
 
 ISOEdA XK' CHEMISTRY. 
 
 198. Preparation. The sulphur of commerce is the 
 native material purified. As found, it is mixed with vari- 
 ous earthy impurities ; and to separate it from these it is 
 subjected to heat in earthen pots, as shown in Fig. 2b'. 
 
 These pots are arranged in the furnace in two rows, and 
 are charged from the top. The. sulphur is converted into 
 vapor by the heat, passes through the narrow tubes into a 
 second row of earthen vessels which act as receivers, is there 
 condensed to a liquid, and runs out at the bottom into wood- 
 en vessels filled with water, placed below. Richer masses are 
 
 Distillation of Sulphur. 
 
 often heated in heaps with just fuel enough to melt the sul- 
 phur, which collects in a depression made at the bottom of 
 the heap. The sulphur thus prepared contains still three 
 or four per cent of impurities ; it is still further refined by 
 another distillation in cylinders of iron, as shown in Fig. 27. 
 The crude sulphur is melted in a tank by the waste heat of 
 the fire, and then runs down through a pipe into the retort, 
 where it is converted into vapor. This vapor enters a large 
 brick chamber, and is there condensed. At first, when the 
 walls are cold, a fine powder is produced, known in com- 
 merce as flowers of sulphur ; but afterwards, when the walls 
 of the chamber become hot, the sulphur condenses to a liquid, 
 
PROPERTIES OF SULPHUR. 
 
 151 
 
 which collects on the floor and may be drawn off and ladled 
 into moulds, forming what is ordinarily called roll brim- 
 stone. 
 
 Sulphur is also obtained from iron disulphide or pyrite, 
 a mineral which, in some localities, is very abundant. For 
 this purpose the pyrite is piled up in a pyramid with wood, 
 
 Fig. 27. Refining of Sulphur. 
 
 and fire applied. The sulphur which is set free collects in 
 the liquid form in cavities made in different parts -of the 
 heap. The pyrite gives up one third of its sulphur when 
 thus treated, yielding about 20 per cent of its weight. 
 
 197. Properties. I. PHYSICAL. Sulphur is capable of 
 existing in three distinct allotropic forms or modifications, 
 due without doubt to varying molecular atomicity : 
 
 (V) The first variety is that found in nature. It is a 
 lemon-yellow, brittle solid, crystallizing in ortho-rhombic octa- 
 hedrons, often modified (Fig. 28, 1, and 2), and possessing a 
 
152 IXORGAXTC CHEMISTRY. 
 
 specific gravity of 2'05. It is easily soluble in carbon disul- 
 phide and may be readily crystallized therefrom., 
 
 (/?) The second variety is produced by crystallizing sul- 
 phur from fusion, at high temperatures. Yellowish-brown 
 needle-shaped crystals belonging to the monoclinic system 
 (Fig. 28, 3), are thus obtained, which are transparent and 
 have a specific gravity of 1'98. This variety also is soluble 
 in carbon disulphide, and passes, slowly at ordinary temper- 
 atures, more rapidly at higher ones, back into variety a. 
 
 Sulphur, since it crys- 
 tallizes in forms belonging 
 to two distinct systems, is 
 called a dimorphous ele- 
 ment. 
 
 (Y) The third variety 
 of sulphur is produced by 
 heating melted sulphur to 
 Fig. 28. sulphur Crystals. a temperature of 250 and 
 
 then suddenly cooling it by pouring it into water. It is a 
 dark brown, tenacious mass, which may be drawn out in 
 threads like caoutchouc. It has a specific gravity of 1 !)"), 
 and is only partially soluble in carbon disulphide, an amor- 
 phous powder remaining uudissolved. It slowly passes into 
 if left to itself; but if heated to 100, it undergoes this 
 change suddenly, the temperature rising to 110 from the 
 heat evolved. 
 
 Eitlfer variety of sulphur melts when heated to 111, be- 
 coming a pale -yellow limpid liquid. As the temperature 
 rises it becomes* viscid, until between 200 and 250 the 
 vessel may be inverted without loss ; it then becomes fluid 
 again, and at 440 boils. Its vapor-density was for a long 
 time considered anomalous, being at 500, 96 ; but Bineau 
 showed that at 1000 it became normal, 32. The molecule 
 of sulphur at 500 is therefore hex-atomic, while at 1000 it 
 is di-atomic. 
 
SVL/'HL'II. 
 
 153 
 
 EXPERIMENTS. To produce the t 1 variety of sulphur, melt 250 
 grams ,of this substance in a crucible over a gas-flame or in a char- 
 coal fire. Allow it to cool 
 until a crust forms upon the 
 surface. Pierce a hole in this 
 crust near one side, and pour 
 out the sulphur which still 
 remains liquid. The interior 
 of the crucible when cold will 
 be found lined with needle- 
 shaped crystals. (Fig. 29.) 
 
 The third or amorphous 
 
 variety of sulphur may be prepared by melt- 
 ing a sufficient quantity in a flask, heating it 
 until the second stage of fluidity is readied, 
 and then pouring it, in a thin stream, into 
 water, as shown in Fig. 30. On removing it 
 from the water, it is found to be remarkably 
 plastic; thus affording an excellent example of allotropism. 
 
 Fig. 29. Mono- 
 clinic Sulphur 
 Crystals. 
 
 Fig. oO. Preparation of 
 Amorphous Sulphur. 
 
 II. CHEMICAL. When heated to 260 in the air, sulphur 
 takes fire, burning with a pale blue flame. It is also a sup- 
 porter of combustion, many metals taking fire readily in its 
 vapor and burning actively. When united with other ele- 
 ments it forms sulphides. 
 
 Berthelot proposes to call the insoluble variety of sulphur 
 electro -positive, and the soluble, electro - negative, because 
 these forms of sulphur are due, in his opinion, to the element 
 with which the sulphur has previously been united. When 
 separated from union with the more negative oxygen, for 
 example, the sulphur is found insoluble and electro-positive ; 
 while, obtained from its hydrogen compound, it is soluble 
 and electro-negative. 
 
 When combined with positive elements alone, sulphur 
 acts as a dyad and is then the analogue of oxygen. As a 
 dyad too, it may perform a linking function. 
 
 198. Tests. In the free state sulphur is recognized by 
 its color, by its volatility when heated, and by its odor when 
 
154 
 
 burned. In combination, as a soluble sulphide, it blackens 
 paper moistened with a solution of lead acetate. 
 
 199. Uses. Sulphur is employed very largely in the arts 
 in the manufacture of gunpowder, in the preparation of sul- 
 phuric acid, in the vulcanization of india-rubber, and for 
 bleaching straws and woolens. 
 
 SULPHUR AND HYDROGEN. 
 
 HYDROGEN SULPHIDE. Formula H,S. Molecular /////.s.s 33*98. 
 Molecular volume 2. Relative density 16*99. The HKIM <>f 1 
 liter is 1*52 gram* (17 critlt*). 
 
 200. History and Occurrence. Hydrogen sulphide 
 called also hydrosulphuric acid and sometimes sulphuretted 
 hydrogen was discovered by Scheele in 1777. It occurs in 
 certain volcanic gases, and is the essential constituent of the 
 water of the so-called sulphur springs, such as Sharon and 
 Avon in this country, Harrowgate in England, Bagnieres in 
 France, and Aachen in Germany. 
 
 201. Preparation and Properties. Hydrogen sul- 
 phide may be prepared by the direct union of its compo- 
 nents, as by passing sulphur vapor and hydrogen through 
 a red-hot tube, filled with fragments of pumice to increase 
 the heated surface. It is generally obtained by the action 
 of an acid upon some sulphide. When ferrous sulphide, for 
 example, is treated with sulphuric acid at the ordinary tem- 
 perature, the reaction is : 
 
 FeS + ' H,(SO 4 ) = Fe(SO 4 ) -f H 2 S 
 
 Ferrous sulphide. Hydrogen sulphate. Ferrous sulphate. Hydrogen sulplii<l<'. 
 
 Or, when antimonous sulphide is heated with hydrochloric 
 acid, antimonous chloride and hydrogen sulphide result: 
 
 Sb& + (HC1) 6 = (SbCl 3 ), 
 
 EXPERIMKNTS. For the continuous preparation of hydrogen sul- 
 phide from ferrous sulphide arid dilute sulphuric acid, Kipp's appa- 
 ratus, shown in Fig. 31, is convenient. It consists of three bulbs of 
 
PROPERTIES or HYDROGEN SULPHIDE. lOO 
 
 glass, the two lower ones being in a single piece, and the upper one, 
 prolonged by a tube re^hing to the bottom of the lower, being 
 ground air-tight into the neck of the second. 
 Through the tubulure of the middle bulb, the 
 ferrous sulphide, in lumps the size of a chest- 
 nut, is introduced, the space between the tube 
 and the side of the constriction being too 
 narrow to let them fall through. This tubu- * 
 lure is then closed by a cork through which 
 a glass stop cock passes. The acid one part 
 sulphuric acid diluted with fourteen of water 
 is poured in through the safety tube, runs 
 into the bottom globe, and rises to overflow 
 the iron sulphide in the middle one. If the 
 cock is open, the gas which is evolved escapes; 
 but when it is shut, the pressure of the accu- 
 mulating gas forces the liquid away from 
 the sulphide down into the lower, and thence 
 into the upper bulb, thus stopping the action 
 and preserving a volume of the gas ready 
 for use. By the tubulure of the lower bulb Fig. 31. Hydrogen Sulphide 
 the acid, when saturated, may be removed. Apparatus. 
 
 Hydrogen sulphide is a colorless gas, with a disgusting 
 odor, well known as that of rotten eggs. It is somewhat 
 heavier than air, its specific gravity being 1*177. Cooled to 
 74, or submitted to a pressure of 17 atmospheres at 10, 
 it condenses to a colorless mobile liquid of specific gravity 
 0'9, which freezes to a mass like ice at 85. It is quite 
 soluble in water, 1 volume of which dissolves 3 volumes at 
 ordinary temperatures, and 4%37 volumes at 0. Chemically, 
 hydrosulphuric acid gas is combustible, burning with a pale 
 blue flame. Its reaction with blue litmus paper is weakly 
 acid. It is easily decomposed by a temperature of 400 and 
 by oxidizing agents, the sulphur frequently being deposited. 
 It reacts with metals and their oxides to produce sulphides, 
 setting hydrogen free in the first case, and water in the sec- 
 ond. This gas is exceedingly poisonous ; according to Fara- 
 
156 i xona AXIC ( 'HEM fs rn } '. 
 
 day, birds die in air which contains but ysVo ^ ^> and dogs 
 in that which contains but -g^j--^. 
 
 Hydrogen sulphide is feebly exothermic, the reaction being, 
 when the sulphur is solid and the hydrogen and hydrogen 
 sulphide gaseous : 
 
 (H 2 ), + S 2 = (H 2 S) 2 + 9,000 water-gram degrees. 
 
 Inasmuch as the solution of hydrogen sulphide in water 
 evolves 9,400 units of heat, it follows that the formation of 
 a solution of this gas from its elements evolves 18,400 heat- 
 units. It is evidently this low heat of formation which ren- 
 ders its direct synthesis so difficult, and which renders the 
 gas so easily decomposed by heat. 
 
 2O2. Tests and Uses. Hydrogen sulphide is easily de- 
 tected by placing in it a strip of paper moistened with a 
 solution of lead acetate ; in this way it may be shown to 
 exist in most specimens of coal-gas, and in the gaseous exha- 
 lations from drains, cess-pools, and the like. AVith sodium 
 nitroferrocyanide in alkaline solution, it strikes a deep purple 
 color. 
 
 It is used extensively in the laboratory as a re-agent, the 
 sulphides which it produces being characteristic for certain 
 metals, either in color, solubility, or in some other easily rec- 
 ognized property. 
 
 EXPERIMENT. The action of hydrogen sulphide upon metallic 
 solutions may be very well shown by the apparatus represented in 
 Fig. 32. The gas is evolved from ferrous sulphide in the two-necked 
 bottle, and passes successively through the four solutions in the ad- 
 joining bottles, the escaping gas being retained in a solution of am- 
 monia. In the first bottle may be placed a dilute acid solution of 
 lead, in the second one of arsenic, in the third one of antimony, and 
 in the fourth one of zinc, the last being made slightly alkaline with 
 ammonia. The sulphide of lead in the first bottle will be black, the 
 sulphide of arsenic in tbe second, yellow, tbe sulphide of antimony in 
 the third, orange, and the sulphide of zinc in the fourth, white. The 
 first three metals are precipitated in acid solutions, the last only when 
 the solution is alkaline. 
 
157 
 
 The gas may readily be inflamed by applying to it a lighted tape:. 
 By holding a bell-glass over an ignited jet of this gas, it is bedewed 
 with moisture, thus proving that the gas contains hydrogen. More- 
 over, on filling a tube, the closed end of which is bent so that it can 
 
 n 
 
 . ; 5-. Precipitation of Metals by Hydrogen Sulphide. 
 
 be placed horizontally, with hydrogen sulphide over mercury, placing 
 a fragment of metallic tin in the horizontal portion and heating it, 
 the gas will be decomposed, the tin forming a sulphide with the sul- 
 phur and setting the hydrogen free. As the volume of the gas re- 
 mains unchanged, it is evident that hydrogen sulphide contains its 
 own volume of hydrogen. 
 
 OXIDES AND ACIDS OF SULPHUR. 
 
 203. Sulphur may unite with oxygen as a dyad, tetrad, 
 or hexad, and may therefore form the following series of 
 oxides and dibasic acids : 
 
 Hyposulphurous oxide S"O Hyposulphurous acid H 2 S"O., 
 
 Sulphurous oxide Siv(). 2 Sulphurous acid H 2 S"VO 3 
 
 Sulphuric oxide S VI 0, Sulphuric acid H,SV'O 4 
 
 Hyposulphurous oxide is unknown. 
 
 204. Hypos ulplmrous Acid. Formula H 2 SO 2 . Mo- 
 lecular mass 65*90. Molecular volume 2 (?). This acid was 
 obtained by Sehutzenberger by the reduction of sulphurous 
 acid by means of zinc : 
 
 Zn + (H 2 S0 3 ) 2 = ZnS0 3 + H,SO, -f H. 2 O 
 A yellow solution resulted which decolorized litmus and in- 
 digo solutions readily. The acid combines readily with oxv- 
 
158 
 
 gen, and is a more active reducing agent than sulphurous 
 acid. It is decomposed on standing in the air, producing at 
 first thio-sulphuric acid and then sulphurous acid, water and 
 sulphur. 
 
 SULPHUROUS OXIDE. Formula SO.,. Molecular maxs 63*9. 
 Molecular volume 2. Eelatur d(<n*!ti/ 31-95. The max* of 1 
 liter is 2 '86 grams (32 crithz). 
 
 205. History and Occurrence. Sulphurous oxide was 
 first pointed out as a peculiar substance by the alchemist 
 Stahl ; but not until 1774 did Priestley carefully examine 
 its properties. It is found among the gaseous products of 
 volcanic action. 
 
 206. Preparation. Sulphurous oxide is uniformly the 
 product of the combustion of sulphur in air or in pure oxy- 
 gen ; being formed thus : 
 
 S, + (O,) 2 = (SO,), 
 
 It is also the product of the action of certain metals, such 
 as copper and mercury, upon sulphuric acid. The metal 
 simply displaces the radical of the acid : 
 
 Cu + ^)} , = C >, + HO., 
 
 **| ) X1 2 ) 
 
 Copper. Sulphuric acid. Copper hi/ilro.cide,. Sufylturow oxide. 
 
 The copper hydroxide then reacts with another molecule of 
 sulphuric acid, thus : 
 
 Copper hydroxide. Sulphuric acid. Copper sulphate. Wafer. 
 
 2O7. Properties. Sulphurous oxide is a colorless gas, 
 with a pungent suffocating odor, known as that of a burn- 
 ing sulphur match. It is more than twice as dense as air, 
 having a specific gravity of 2 -247. Cooled to 10 by a 
 freezing mixture, it condenses to a thin colorless liquid of 
 specific gravity 1'49, which becomes solid at 76. Its 
 critical temperature is 155 '4, and its critical pressure is 78 '9 
 
S OF XULPHl'lfOt'S OX I It K. 159 
 
 atmospheres. A temperature of 60 is produced by !<> 
 evaporation. Heated to 1200 under pressure, it is decom- 
 posed and yields sulphuric oxide and sulphur. 
 
 Sulphurous oxide gas is freely soluble in water, one vol- 
 ume of which dissolves at 0, 68'86, and at 20, 36*22 vol- 
 umes of this gas, forming sulphurous acid. This solution, 
 when cooled to 0, deposits cubical crystals consisting of 
 H 2 H0 3 , 14 aq. 
 
 Chemically, sulphurous oxide is neither a combustible nor 
 a supporter of combustion; burning bodies introduced into 
 it are at once extinguished. It unites directly with chlorine 
 to form sulphuryl chloride, and with positive oxides to form 
 sulphites. Hydrogen sulphite or sulphurous acid has 
 strong acid properties and destroys vegetable colors, appar- 
 ently by forming direct compounds with them. It exhibits 
 a decided tendency to take up oxygen and to pass into sul- 
 phuric acid; and therefore acts as an energetic reducing 
 agent. It is a dibasic acid, and forms acid, normal and dou- 
 ble sulphites. Its formation is strongly exothermic, 78,700 
 heat-units being evolved in the production of a dilute aque- 
 ous solution from solid sulphur and oxygen. 
 
 EXPERIMENTS. Sulphurous oxide is easily liquefied by passing; it, 
 previously thoroughly dried, through a U-tube immersed in ice and 
 salt, as shown in Fig. 33. It may he pre- 
 served in sealed tubes, or if the quantity 
 be large, in well -stoppered mineral -water 
 bottles. To show the cold produced by its 
 evaporation, pour some of the liquid upon 
 the surface of mercury contained in a cap- 
 sule, and blow a current of air over it by 
 means of a bellows. The mercury will be 
 frozen. Or, pour some of the liquid oxide 
 
 into a thick crucible of platinum which is Fig. 33. Condensation of 
 
 Sulphurous Oxide. 
 red hot; the liquid will assume the sphe- 
 
 roidal state at a temperature below its boiling point. Tf now, a little 
 water be poured in, the sulphurous oxide will be instantly vaporized 
 by the heat taken from the water, which therefore at once becomes 
 
160 
 
 1 \OHCA \1< ' ( 77 AM/ 7.S77,' 1 '. 
 
 ice. Bv some dexterity, the lump of ice mav l>e thrown out of tlie 
 
 red-hot crucible. 
 
 The bleaching power of sulphurous oxide upon flowers may be 
 
 illustrated by burning some sulphur under a glass shade (Fig. 34), 
 
 within which, on a tripod, are some 
 brilliantly colored flowers. The flow- 
 ers will be readily bleached, but at the 
 same time will be very much wilted. 
 That the color is not destroyed in 
 these cases, may be proved very well 
 bv adding some sulphurous acid t. > 
 two glasses, each of which contains 
 some fresh infusion of the purple cab- 
 bage an excellent vegetable color 
 for testing acidity and alkalinity. The 
 bleaching action is but slight till potas- 
 sium hydroxide solution is cautiously 
 
 added, when the color entirely disap- 
 Fig. 34. Bleaching by SOa. . J 
 
 pears, the two liquids becoming color- 
 less. But if a little strong sulphuric acid be added to one, and a little 
 potassium hydroxide solution to the other, the color reappears in both ; 
 in the -first case brilliant red, in the other brilliant green. Ether, ben- 
 zene, arid some other substances, will also restore the color of bodies 
 thus bleached. 
 
 The deoxidizing power of sulphurous acid may be shown by add- 
 ing its solution to one of potassium permanganate. The deep purple 
 color of the latter solution at once disappears. 
 
 2O8. Tests and Uses. Sulphurous oxide when free is 
 at once detected by its pungent odor, and by its blackening 
 action upon paper moistened with a solution of raercurous 
 nitrate. In combination as a sulphite, it evolves hydrogen 
 sulphide when added to a solution evolving hydrogen. 
 
 In the arts it is used chiefly for bleaching straws and 
 woolens; but for the reasons just given, the bleaching in 
 not permanent as it is with chlorine, but requires to be fre- 
 quently repeated. On account of its reducing power sul- 
 phurous acid, in the form of sodium sulphite, is sometimes 
 uaed as a preserving fluid in canning fruits and vegetables. 
 
SULPHURIC OX IDE. 161 
 
 SULPHURIC OXIDE. Formula SO 3 . Molecular mass 79*86. 
 Molecular volume 2. Relative density 39 : 93. The mass of 
 one liter of the vapor is 3 '58 grams (40 criths). 
 
 209. Preparation. Sulphuric oxide may be prepared 
 by oxidizing sulphurous oxide. When this gas is mixed 
 with oxygen, both being perfectly dry, and the mixed gases 
 are passed over heated platinized asbestus, they unite, and 
 form sulphuric oxide. Commercially, the gases are obtained 
 in the proper proportion by dropping sulphuric acid into 
 red-hot platinum retorts. The water formed is removed by 
 }>assing the products through sulphuric acid. The oxide is 
 also obtained by heating di-sulphuric acid or sodium disul- 
 phate : 
 
 H 2 S 2 7 = H 2 (S0 4 ) + SO S 
 
 Di-sulpliuric acid. Sulphuric add. Sulphuric oxide. 
 
 The vapor evolved is collected in a cold and dry receiver. 
 
 210. Properties. Sulphuric oxide as thus obtained is 
 a white, wax-like solid, crystallizing in silky fibers resem- 
 bling asbestus. Its specific gravity is 1'9. It melts at 16, 
 and boils at 46. On maintaining the temperature of the 
 fused oxide below 25, it gradually changes into a solid, 
 polymeric apparently with the one just mentioned, and called 
 t sulphuric oxide; this, at 50, becomes fluid again, being 
 transformed into the a form. Recent researches make it prob- 
 able that both these modifications contain water. When ob- 
 tained perfectly anhydrous by repeated distillations, it is a 
 readily mobile liquid having a specific gravity of 1*94 at 
 K), and solidifying in long transparent needles resembling 
 niter, fusing at 14'8. The liquid boils at 46'2. It fumes 
 strongly in the air and unites with water with the evolution 
 of great heat, producing sulphuric acid. Since the union 
 of SO, and oxygen to form liquid SO 3 evolves 32,100 heat- 
 units, the heat of formation of liquid SO 3 from solid sulphur 
 and oxygen is 103,200 heat-units. 
 
1 62 
 
 HYDROGEN SULPHATE OR SULPHURIC ACID. Formula H,SO r 
 Molecular mass 97 '82. Specific gravity of liquid 1*854 at 0. 
 Boils at 325. 
 
 211. History and Occurrence. Sulphuric acid was 
 prepared by Basil Valentine in the 15th century under the 
 name " oleum sulphuris per campanum." Dr. Roebuck pro- 
 posed the present method of manufacture in 1770. The acid 
 thus made is therefore often called "English" add. 
 
 Sulphuric acid occurs free in the waters of certain rivers 
 and mineral springs. Boussingault estimates that the Rio 
 Vinagre in South America carries daily to the sea more than 
 38,000 kilograms ; and the water of the Oak Orchard min- 
 eral spring, New York, contains in each liter over 2-J grains. 
 It has also been observed as a secretion of certain mollusks ; 
 the saliva of Dolium galea Lk. containing nearly 3^ per cent 
 of it. In the sulphates of iron, calcium, barium, and stron- 
 tium, forming the minerals melanterite, gypsum, barite, and 
 celestite, sulphuric acid is also represented. 
 
 212. Preparation. Sulphuric acid is prepared by add- 
 ing water to sulphuric oxide, either at the instant of its for- 
 mation or subsequently : 
 
 H. 2 + S0 ;j = H,SO, 
 
 When sulphur is boiled in nitric acid, it is oxidized to sul- 
 phuric oxide, which unites at once with the water present, 
 forming sulphuric acid. In the preparation on the large 
 scale there are two general stages : 1st, the oxidation of the 
 sulphurous to sulphuric acid by the oxygen of the air ; and 
 2d, the solution of the sulphuric oxide in water. The agent 
 employed for carrying oxygen from the air to the sulphu- 
 rous oxide is nitrogen tri-oxide, N.,O,. The entire process 
 may be represented theoretically by the four following steps, 
 although in fact the reactions are much more complicated: 
 1st. The burning of the sulphur to get sulphurous oxide ; 
 
 S + O, = SO, 
 
PR EPA EA TJOX OF ,s / 'LI' II I IUC ACID. 163 
 
 2d. The reaction of the sulphurous and nitrogen oxides : 
 
 80. + NA = SO, + NA 
 3d. The union of the sulphuric oxide with water: 
 
 S0 3 + H,0 = H 2 S0 4 
 4th. The re-oxidation of the NA ^ rom tne air : 
 
 (NA), -f O, = (NA), 
 
 In practice the operation is conducted in large leaden 
 chambers, shown in Fig. 35 on the following page. The 
 sulphur is burned in the furnace seen on the left, and the 
 sulphurous oxide produced passes up through the large pipes, 
 through a smaller and then a larger chamber, into a third, 
 upon the floor of which porous, earthen, terrace-shaped ves- 
 sels are placed, over which a stream of nitric acid flows from 
 the reservoirs just above. The reaction w T hich takes place 
 here is as follows : 
 
 (SO A, + (HN0 8 ) 2 + H,0 = (H 2 S0 4 ) 2 -f NA 
 In presence of a limited supply of steam, the next reac- 
 tion is : 
 
 (SO,), + NA -f 2 + H,0 = 
 
 the product being a crystalline compound called nitrosyl- 
 sulphuric acid. By the action of water this is decomposed 
 as follows : 
 
 The third stage is effected by blowing steam into the cham- 
 bers from a boiler heated by the burning sulphur, as shown 
 in the figure. The sulphuric acid resulting from the decom- 
 position of the crystalline compound and the union of its 
 sulphuric oxide with water collects on the floor of the cham- 
 bers, while the N.,O 2 unites with the oxygen of the air pres- 
 ent to form NA> an( l tnus renews the oxidation. A cur- 
 rent of air passes slowly through these chambers, and to 
 prevent loss, especially of the nitrogen oxides, the escaping 
 
164 
 
 INORGANIC 
 
PREP AH A TION OF 8 ULPH UK 1C A CID. 1 65 
 
 products pass up through a column of moistened pumice, 
 seen on the right, by which these are absorbed. The solu- 
 tion thus obtained is carried toward the sulphur furnace and 
 allowed to trickle slowly over a series of inclined shelves in 
 the first chamber, where it meets the entering sulphurous 
 oxide and is utilized. A series of smaller chambers is gen- 
 erally preferred to a single large one. When the acid which 
 accumulates in the water on the floor of the chambers has a 
 specific gravity of 1*5, it is drawn off, concentrated in leaden 
 vats by heat until the specific gravity rises to 1*7, and then 
 in a platinum still or in retorts of glass, until most of the 
 .water is driven off and the specific gravity rises to 1 *83. It is 
 then placed in carboys for use. In practice the leaden cham- 
 bers often have a capacity of 100,000 cubic feet, and pro- 
 duce continuously thousands of tons per week. Sulphur itself 
 is generally employed in this manufacture, though in some 
 cases the sulphurous oxide is obtained by roasting pyrite. 
 
 EXPERIMENTS. To show the reducing action of sulphurous oxide 
 upon nitrogen oxides, place in a jar filled with sulphurous oxide 
 (Fig. 36) a stick dipped in strong nitric acid. Red 
 fumes of the reduced nitrogen compounds will at 
 once fill the jar, and soon unite with the sulphu- 
 ric oxide to form a crystalline compound which 
 lines the walls of the vessel. On adding water, 
 the crystals dissolve with effervescence, the red 
 fumes again appear, and sulphuric acid may be 
 found in the liquid at the bottom of the jar. 
 
 Upon the lecture-table, the sulphuric acid proc- 
 ess may be illustrated by the apparatus shown in Fig. 36. Oxidation of 
 Fig. 37. The lead-chamber is represented by the 
 large glass globe, at first full of air. The two-necked bottle on the 
 right contains the materials for generating N. 2 O 2 ; this gas enters the 
 globe, meets with the air, and becomes N 2 O 3 . By means of a mixture 
 of sulphur and manganese di-oxide contained in the flask shown on 
 the left, sulphurous oxide is evolved and is led into the globe by the 
 connecting tube. There meeting with the N 2 O 3 , the second reaction 
 
 given above takes place, N.,O 3 and SO 2 producing 8Oj/< QJJ** which 
 
166 
 
 INORGANIC CHEMISTR Y. 
 
 lines the walls of the globe, now colorless, with white radiating crys- 
 tal!;. If finally, a jet of steam be blown in frotn the third flask, the 
 crystals disappear, the globe becomes tilled with red vapors, and sul- 
 
 Fig. 37. Production of Sulphuric Acid. 
 
 phuric acid collects at the bottom. By renewing the air from time to 
 time, through the rubber tube shown on the right, the process may be 
 made continuous. 
 
 213. Properties. Sulphuric acid is a dense, colorless, 
 oily, and very corrosive acid liquid, having a specific grav- 
 ity of 1-854 at 0. It boils about 338 and solidifies when 
 cooled to a low temperature ; the crystals, which have the 
 composition H 2 SO 4 , melting at 10-8. It may be distilled, 
 but suffers a partial decomposition, so that the product con- 
 tains but 98'7 per cent of acid ; this separation into sulphu- 
 ric oxide and water or dissociation, as it is called takes 
 place completely at higher temperatures, so that at 416 its 
 vapor-density is only one half of that required by theory. 
 Sulphuric acid has a very strong attraction for water, com- 
 bining with it with the evolution of great heat. It attracts 
 moisture from the air, and is often used to dry a gas by caus- 
 ing it to bubble through the acid. It also removes water 
 from organic matters placed in it, completely charring them. 
 
PROPER TIES OF S ULPH URK ' AC 1 1). 
 
 167 
 
 EXPERIMENTS. To show the heat evolved by the union of sul- 
 phuric acid and water, pour one part of water upon four parts strong 
 sulphuric acid in a beaker, and stir the mixture with a test-tube con- 
 taining- some ether or alcohol, colored with alkanet, or other color- 
 ing matter. The alcohol or ether will boil violently; by holding the 
 tube in a stand, the vapor may be ignited, producing a voluminous 
 flame. 
 
 To .show its action on organic matters, add to 50 cubic centimeters 
 of sulphuric acid an equal volume of strong sugar-syrup. On stirring 
 the two together the mass will 
 become hot and rise into a 
 black porous coal. 
 
 The attraction of sulphuric 
 acid for water is now made 
 use of largely in Paris for the 
 production of ice. Fig. 38 
 shows the apparatus contrived 
 by Carre for this purpose. The 
 water to be frozen is placed in 
 the flask on the left, which is 
 connected by a tube with a 
 horizontal reservoir contain- 
 ing sulphuric acid; this reser- 
 voir may be exhausted by the 
 
 air pump, the sulphuric acid 
 
 Fig. 38. E. Carre's Ice Apparatus, 
 being constantly agitated by 
 
 means of a stirrer. The water is cooled by its own evaporation under 
 the diminished pressure; and as the vapor produced is at once removed 
 by the sulphuric acid, it soon congeals. A pint of water may be frozen 
 in 15 seconds with this apparatus. 
 
 The sulphuric acid which has DOW been considered is the 
 di-meta form, according to the previous classification of acids, 
 page 44. By limiting the temperature during evaporation 
 to 205, by cooling a mixture of acid and water of specific 
 gravity 1'78, or by mixing together 100 parts "of the acid 
 and 18 '4 parts of water, an acid is obtained having the 
 composition H 4 S VI O 5 , which is mono-meta-sulphuric acid. It 
 has a specific gravity of 1'78, and at 7'5 crystallizes in the 
 rhombic system. Again, if a dilute acid be carefully evapo- 
 
168 INORGANIC CHEMISTRY. 
 
 rated at 100, a third definite compound of water and sul- 
 phuric oxide results. It has the formula H 6 S VI O 6 , and is 
 ortho-sulphuric acid. 
 
 The common form of sulphuric acid is di-basic ; sulphates 
 may therefore be acid, normal, or double. Letting M stand 
 for a monad metal, they may be represented thus : 
 
 Acid. Acid salt. Normal salt. DoubU ?nlt. 
 
 The other forms of sulphuric acid given above have also 
 their corresponding salts. A zinc niono-meta-sulphate Zn"., 
 SO 5 , and a mercuric ortho-sulphate Hg" 3 SO c , are well known 
 compounds. 
 
 The solution of sulphuric oxide in -water evolves 36,100 
 heat-units. So that the heat of formation of normal or ortho- 
 sulphuric acid is 210,700 heat-units, and that of ordinary or 
 di-meta sulphuric acid H 2 SO 4 is 192,900 heat-units. 
 
 214. Di-sulphuric Acid, H,S 2 O 7 . Another kind of sul- 
 phuric acid is found in commerce, prepared by the distilla- 
 tion of partially dried ferrous sulphate in earthen retorts. 
 It is a heavy oily liquid of specific gravity 1*9 ; it is usually 
 more or less dark colored, hisses like a hot iron when dropped 
 into water, and fumes strongly in the air. It is therefore 
 called fuming sulphuric acid, or, as it is manufactured largely 
 in Nordhausen in Saxony, sometimes Nordhausen sulphuric 
 acid. The name di-sulphuric acid is given to it, because it 
 may be regarded as derived from two molecules of sulphuric 
 acid, by the removal of one molecule of water, thus : 
 
 (H 2 SO 4 ) 2 -- H 2 O = H,SA 
 
 When heated, it decomposes into sulphuric acid and sul- 
 phuric oxide, according to the equation : 
 H 2 SA = H 2 S0 4 + SO, 
 
 It is used for dissolving the indigo with which the celebrated 
 Saxony blues are made. 
 
TESTS FOP SULPHURIC ACID. 169 
 
 Di-sulphuric acid is DOW made commercially by conducting 
 sulphuric oxide, made by passing sulphurous oxide and oxy- 
 gen over platinized asbestus at a high temperature, through 
 ordinary sulphuric acid. It is called solid sulphuric acid, 
 because it solidifies when cooled, forming crystals which melt 
 at 35. 
 
 Three sulphates have long been known under the name 
 of vitriols, because like glass ; zinc sulphate, or white vitriol ; 
 ferrous sulphate, or green vitriol; and copper sulphate, or 
 blue vitriol. Because sulphuric acid was first prepared by 
 distilling the second of these, it has received the name of oil 
 of vitriol. 
 
 215. Tests. The test for free sulphuric acid is the char- 
 ring it causes. A natural water containing this acid, if used 
 to moisten paper, will char it completely on drying at 100. 
 In combination in a soluble form, sulphuric acid and sul- 
 phates give a dense white precipitate with solution of barium 
 chloride, insoluble in acids. If the sulphate be insoluble in 
 water, it may be recognized by fusing it with sodium carbon- 
 ate, thus converting it into sodium sulphate. This is soluble 
 in water and may be tested as above. Or, what is sometimes 
 preferable, the suspected sulphate may be heated for some 
 time with pulverized charcoal ; it will thus be reduced to a 
 sulphide, which, on treatment with a drop of acid, will evolve 
 the well-known odor of hydrogen sulphide. 
 
 216. Uses. Sulphuric acid is the most important sub- 
 stance consumed in chemical manufactures. It is used in 
 the production of nitric, hydrochloric, phosphoric, citric, and 
 tartaric acids ; and in the manufacture of soda, of phospho- 
 rus, of alum, and of the alkaloids. It is largely used in dye- 
 ing, in calico printing, and in bleaching ; in the preparation 
 of fertilizers, and in the refining of petroleum. Indeed, the 
 extent of the consumption of sulphuric acid by any nation, 
 it has been well said, is a true index of its commercial pros- 
 perity. 
 
170 INORGANIC CHEMISTRY. 
 
 THIONIC ACIDS. 
 
 Besides the acids now given, in which there is but one 
 atom of sulphur in each molecule, there are others contain- 
 ing more than one such atom, the two or more sulphur 
 atoms having different valences. This group of acids, called 
 the thionic series, from the Greek ftelov, sulphur, contains 
 the following substances.: 
 
 O 
 II 
 Thio-sulphuric acid H 2 S 2 O 3 HS S OH 
 
 O 
 
 O O 
 
 II II 
 
 Dithionic acid H^S./ > f> HO S S OH 
 
 O O 
 O O 
 
 II II 
 
 Trith ionic acid H 2 S 3 O 6 HO S S S OH 
 
 II II 
 
 O 
 
 O O 
 
 II II 
 
 Tetra tli ionic acid H^Og HO S S S S OH 
 
 II II 
 
 O O 
 
 O O 
 
 II II 
 
 Pentathionic acid H 2 S 5 O 6 HO S S S S S OH 
 
 II il 
 
 O O 
 
 217. Thio-sulpliuric Acid. Hypo-sulphurous acid 
 of some authors. Thio-sulphates are prepared either by add- 
 ing sulphur to a sulphite or by partial oxidation of a sul- 
 phide. By the first method : 
 
 Na 2 SO 3 + S = Na 2 S 2 O, 
 
 Large quantities of the sodium salt were formerly manufact- 
 ured for use in photography, under the name sodium hypo- 
 
RELEXITM A XI) TELLURIUM. 171 
 
 sulphite. It is also used as an antichlor in chlorine bleach- 
 ing. The acid corresponding to it has not been prepared in 
 the free state, as it rapidly decomposes. 
 
 SULPHUR AND CHLORINE. 
 
 218. The Sulphides of Chlorine are three in number, 
 having the formulas C1 2 S 2 , C1 2 S, and C1 4 S. They are formed 
 by the direct union of their constituents, the first being 
 formed when the sulphur is present in excess, the last when 
 the chlorine is most abundant. The chloride, C1 4 S, exists 
 not only in the free state, but also in combination with cer- 
 tain metallic chlorides as SnCl 4 (Cl 4 S). 2 with stannic chloride, 
 (SbCl 5 ) 2 (C1 4 S) 3 with antimouic chloride, etc. 
 
 The sulphurous acid radical SO", called thionyl, and the 
 sulphuric acid radical SO/', called sulphuryl, combine with 
 chlorine to form thionyl chloride SOC1 2 and sulphuryl chlo- 
 
 ( OH 
 
 ride SO 2 C1 2 . The intermediate compound SO 2 j p, , sulphu- 
 ryl hydroxy-chloride is also known. 
 
 3. SELENIUM AND TELLURIUM. 
 
 SELENIUM. Symbol Se. Atomic mass 78 -87. Molecular mass 
 157*74. Valence II, IV, VI. Relative density of vapor 78*87. 
 Molecular volume 2. Specific gravity of solid 4*5. The mass 
 of one liter of selenium -vapor at 1420 is 7*08 grams (79 
 criths). 
 
 219. History and Preparation. Selenium was discov- 
 ered by Berzelius in 1817 in the lead-chamber deposits of 
 the sulphuric acid manufactory at Gripsholm. He named 
 it from ffetyvy, the moon. It is a rare substance, occurring 
 occasionally free, but generally combined with copper, lead, 
 silver and mercury, as* selenides. It exists also as an impu- 
 rity in certain sulphurs. It is obtained from the sulphuric 
 acid residues, or from the minerals containing it, by fusing 
 
172 IXORGJXIC CHEMISTKY. 
 
 with sodium nitrate and carbonate, extracting the sodium 
 sclenate with water, and reducing this with a solution of 
 sulphurous acid. 
 
 220. Properties. Selenium, like sulphur, is capable of 
 existing in at least two allotropic states : Selenium, which 
 corresponds to sulphur, is a dark, grayish-black crystalline 
 solid, of specific gravity 4*8, and is insoluble in carbon di- 
 sulphide. It is a conductor of electricity and has a metallic 
 luster. /? Selenium, is dark reddish-brown in color, has a 
 specific gravity of 4*5, and is soluble in carbon di-sulphide, 
 from which it crystallizes in monoclinic prisms. This is the 
 more stable form of selenium, the form it has when native. 
 A third or amorphous variety is known, having a specific 
 gravity 4'26, and existing in two forms, the one electro-posi- 
 tive and insoluble in carbon di-sulphide, the other electro- 
 negative and soluble in this liquid. It fuses a little above 
 100, and if suddenly cooled becomes vitreous selenium. On 
 heating it to 217 and then suddenly cooling to 180-19(), 
 keeping this temperature constant for some time, the amor- 
 phous is converted into the crystalline variety, selenium. 
 On raising the temperature to 150, /9 passes into a selenium, 
 with a distinct evolution of heat, ft Selenium melts at 217. 
 The liquid boils at about 700. In its chemical properties, 
 selenium very closely resembles sulphur, forming similar 
 compounds with other elements. It burns with a blue flame 
 and gives off an intolerable odor like that of decaying horse- 
 radish. It unites directly with the metals, forming selenides. 
 
 TELLURIUM. Symbol Te. Atomic mass 125*0. Valence II, 
 IV, and VI. Relative density of vapor 125*0. Molecular 
 volume 2. Specific gravity of solid 6*25. The mass of 1 liter 
 of tellurium-vapor at 1390 is 11*47 grams (125*0 criths). 
 
 221. History and Preparation. Tellurium was dis- 
 covered by Klaproth in 1798, in a Transylvanian gold ore, 
 and named from tellus, the earth. It occurs even more 
 
S OF TELLURU M. 173 
 
 rarely than selenium, and is found native in Colorado and 
 in Hungary. It exists also in combination with bismuth, 
 lead, gold, and silver. The mode of its preparation is analo- 
 gous to that of selenium. It is obtained in solution either 
 as potassium telluride, or as tellurous acid, and then precip- 
 itated ; in the former case by a current of air, in the latter 
 by sulphurous acid. 
 
 222. Properties. Tellurium is a tin-white, brittle solid, 
 having a strong metallic luster and a specific gravity of 6*25. 
 It crystallizes in rhombohedrons, and conducts heat and elec- 
 tricity readily. It melts at 500, volatilizes at a white heat, 
 and may be distilled. Its vapor is greenish-yellow like chlo- 
 rine. When heated in the air it takes fire and burns with a 
 blue flame tinged with green, evolving white fumes of tel- 
 lurous oxide. Indeed in all its physical properties it is a 
 metal ; but it is so closely allied chemically to sulphur and 
 selenium, that it is considered with these elements. Its bi- 
 nary compounds are called telluricles. 
 
 RELATIONS OF THE GROUP. 
 
 223. The same gradation of properties is seen here which 
 was noticed in the chlorine group. As the atomic weight 
 increases, the chemical activity diminishes. The sum of the 
 atomic weights of sulphur and tellurium (31 '98+ 125), is 
 almost exactly double that of 'selenium, 78 '87. They all 
 form similar compounds with hydrogen, H 2 O, H 2 S, H 2 8e, 
 and H 2 Te, in which they are bivalent; and the last three 
 form oxides, in which their valence is four and six ; as SO., 
 and SO 3 ; SeO 2 and SeO :j ; TeO a and TeO 3 , to each of which 
 there is a corresponding acid. 
 
174 INOltGAXIC CHEMISTRY. 
 
 EXERCISES. 
 
 1. By what physical and chemical methods may oxygen be ob- 
 tained? 
 
 2. What volume does a gram of oxygen occupy? 
 
 3. One gram of mercuric oxide yields what mass of oxygen ? 
 
 4. How much mercuric oxide is required to yield 356 c. c. o* oxy- 
 gen measured at 15 and under 736 mm. pressure? 
 
 6. What mass of oxygen measured at 100 is necessary to fill a 
 gas-jar which holds 4-6 liters of water? 
 
 6. At what temperature do 75) c. c. of oxygen occupy a liter? 
 
 7. Calculate the percentage of oxygen in CuO, MnO.^, KC10.,, 
 KN0 3 . 
 
 8. How much potassium chlorate is necessary to yield a cubic 
 meter of oxygen? A kilogram? 
 
 9. If the chlorate be one dollar a kilogram, what will the oxygen 
 cost per cubic meter ? 
 
 10. A liter of oxygen is required of the relative density of 100 at 0; 
 how much KC1O. { is needed, and what is the pressure on the gas? 
 
 11. How much O will one liter of chlorine evolve from water? 
 
 12. From what is the name oxygen derived? Illustrate. 
 
 13. By what processes is oxygen obtained commercially? 
 
 14. When was ozone first recognized? By whom? 
 
 15. How may ozone be produced? What is Schonbein's test? 
 
 16. In what do oxygen and ozone differ? 
 
 17. How is the composition of water proved by synthesis? By 
 analysis? 
 
 18. What is the mass of a cubic meter of steam? What volume 
 of hydrogen does it contain? Of oxygen? 
 
 19. One gram of water contains what volume of mixed gases? 
 
 20. If 226 c. c. of oxygen and 500 c. c/of hydrogen, both at 110, 
 be mixed and exploded, what will be the composition of the remain- 
 ing gas, and what its volume at 0? 
 
 21. What mass of potassium chlorate is needed to evolve the amount 
 of oxygen contained in one c. c. of water? 
 
KXERCTSKR. 17;" 
 
 22. What mass of water can be heated from- to 1 bv the combus- 
 tion of one cubic meter of mixed oxygen and hydrogen? 
 
 23. What volume has a block of ice the mass of which is a kilo- 
 gram? 
 
 24. An iceberg floating in sea-water of specific gravity 1-027, ex- 
 poses 30,000 cubic meters above the surface; what is its entire vol- 
 ume ? 
 
 25. Define water of crystallization. Efflorescence. Deliquescence. 
 
 26. How is hydrogen peroxide prepared? What are the tests for it? 
 
 2. 
 
 27. How does sulphur occur in nature? How is it purified? 
 
 28. Why is sulphur dimorphous? Pr-i.ve its allotropism. 
 
 29. What is the mass of 632 c. c. of sulphur-vapor at 500? At 
 1000? 
 
 30. One liter of hydrogen sulphide contains what mass of sulphur? 
 
 31. 500 c. c. H 2 S requires what volume of oxygen for its combus- 
 tion ? 
 
 32. How many grams of FeS and of H 2 S0 4 are needed to yield one 
 cubic meter of H 2 S? To saturate one liter of water at 0? 
 
 33. Name the oxides and the acids of sulphur. 
 
 34. Sulphur burned in a liter of oxygen, gives what volume of 
 SO,? 
 
 35. Ten grams of S gives what volume of SO 2 ? What mass? 
 
 36. 53 grams of copper yield how many c. c. of sulphurous oxide, 
 measured at 100 and under 750 mm. pressure? 
 
 37. To produce 100 grams of calcium sulphite requires how much 
 SO,? 
 
 38. One kilogram of SO 3 requires the oxidation of what volume of 
 SO, ? 
 
 39. What mass of H. 2 S 2 7 will yield 100 c. c. of solid SO H ? 
 
 40. One gram of sulphur yields what mass of sulphuric acid? 
 
 41. Oil of vitriol of sp. gr. 1-773 contains 70 per cent of sulphuric 
 acid; how many kilograms of such acid may be made from 150 kilo- 
 grams of pyrite, containing 42 per cent of sulphur? 
 
 ^42. What are the chemical changes in the leaden chamber? 
 
 43. To neutralize a kilogram of lime requires what mass of H,SO 4 ? 
 
 44. How is sulphuric acid detected? What salts does it form? 
 
 45. What is di-sulphuric acid and how is it made? 
 
176 
 
 CHAPTER FOURTH. 
 
 NEGATIVE TRIADS. 
 
 1. NITROGEN. 
 
 Symbol N. Atomic ma** 14-01. Valence 1, III, and V. Rela- 
 tive (leHxiti/ 14. Muh'cnlur imi** 28'02. Molecular volume 2. 
 T/i mo&s o/* o?ie Mter is 1'257 grams (14 critks). 
 
 224. History. Nitrogen was discovered by Rutherford 
 in 1772. He showed that air, after it had been breathed 
 by an animal and washed with lime-water, contained a gas 
 which would support neither respiration nor combustion. 
 Scheele and Lavoisier soon after showed, independently, 
 that this substance constituted four fifths of the air. La- 
 voisier gave it the name azote, from a and !>/;. Chaptal 
 proposed the name nitrogen, from vtrpov and ysww, because 
 a necessary constituent of niter. 
 
 225. Occurrence. Nitrogen exists free in the air, mixed 
 with oxygen. It occurs also combined, in the nitrates of 
 sodium, potassium and calcium, and in ammonia. It forms 
 an essential component of many vegetable and animal sub- 
 stances. 
 
 22O. Preparation. The easiest method of preparing 
 nitrogen is to burn out of a given volume of air the oxygen 
 it contains, thus leaving the nitrogen. It may also be pro- 
 cured by purely chemical processes; as by heating ammo- 
 niam nitrite: (NHj)NOj = (^ + ^ 
 
 or by passing chlorine gas through ammonia solution in 
 
 excess : 
 
 (H 3 N) 8 + (0,), = (NH.C1). + N, 
 
PROPERTIES 01' A7 Y7.W, A'.Y. 
 
 177 
 
 Fig. 39. Preparation of Nitrogen. 
 The oxvgen is retained bv the 
 
 EXPERIMENTS. Nitrogen may be obtained from air by burning- 
 out the oxygen by phosphorus or copper. A fragment of phosphorus, 
 carefully dried, is placed in a small 
 capsule floated upon the surface of 
 water by a piece of cork. The phos- 
 phorus is lighted and then covered 
 with a large bell- glass, as shown 
 in Fig. 39. Dense white fumes are 
 formed by the combustion, which fill 
 the jar; the oxygen is gradually con- 
 sumed, and the water rises to take 
 its place. In a short time these 
 fumes disappear, and the nitrogen 
 is left comparatively pure. 
 
 When copper is used, it is heated 
 to redness in a glass tube, and a 
 slow stream of air is passed over it. 
 copper, and the nitrogen escapes from the tube. 
 
 For the chemical preparation of nitrogen, the ammonium nitrite 
 or what is equivalent to it, a mixture of equal parts ammonium chlo- 
 ride, potassium dichromate, and potassium nitrite in three parts of 
 water is beated in an ordinary flask, and the gas is collected over 
 water. 
 
 227. Properties. I. PHYSICAL. Nitrogen is a color- 
 less, odorless, and tasteless gas, somewhat lighter than air, 
 its specific gravity being 0*971. When cooled to 150 in 
 liquid ethylene, boiling under a pressure of 10 millimeters, 
 nitrogen is readily liquefied by a pressure of about 30 atmos- 
 pheres. The critical temperature ;s 146 and the critical 
 pressure 35 atmospheres (Olszewski). Under these condi- 
 tions liquid nitrogen has a density of 0*4552 ; which becomes 
 0*83 at 193 and one atmosphere, and 0*866 at 202 and 
 0*105 atmosphere. At 153*7 its coefficient of expansion 
 is 0*0311. Its boiling point is 193; though by evaporat- 
 ing it in vacuo a temperature of 213 has been reached. 
 When the gas is compressed, cooled in boiling oxygen and 
 suddenly expanded, solid nitrogen falls in crystals like snow. 
 
178 
 
 Water dissolves about 2*5 per cent of it. Its refractive 
 power is to that of air as 1*034 to 1. 
 
 II. CHEMICAL. Chemically, nitrogen is a' remarkably inert 
 substance, entering into direct combination with only a few 
 elements, such as carbon, silicon, boron, and titanium, and, 
 at an exceedingly elevated temperature, with oxygen. It 
 extinguishes burning bodies introduced into it, and at ordi- 
 nary temperatures is not itself combustible. It is irrespira- 
 ble, though it exerts no positively injurious action upon the 
 tissues; animals die in it as they would in water, simply 
 from suffocation. Though so indifferent when free, the com- 
 pounds formed by nitrogen are among the most energetic 
 known. The corrosive nitric acid, the pungent ammonia, 
 the explosive nitre-glycerin , the active poisons known as 
 prussic acid and the alkaloids, all contain nitrogen. Some 
 chemists have long believed it to be compound. 
 
 THE ATMOSPHERE. 
 
 228. Physical Properties. The atmosphere is the aerial 
 envelope which surrounds the earth. Careful experiments 
 by Regnault have shown that one liter of air weighs 1*29318 
 grams at 0, and under 760 millimeters pressure ; it is there- 
 fore 14'43 times heavier than hydrogen, and is the standard 
 of specific gravity for gases. Torricelli showed, in 1643, that 
 the pressure of the air upon the earth's surface would sus- 
 tain a column of mercury about 76 centimeters in height ; 
 and as a column of meYcury of this height, whose area is 
 one square centimeter, weighs 1033 '3 grams, it follows that 
 this number represents the atmospheric pressure upon every 
 square centimeter of the earth's surface. This is equivalent 
 to 1,033x980, 6r 1,012,340 dynes; a little more than one 
 mega-dyne. From this it appears that the entire mass of 
 the air on our globe is about equal to that of a sphere of lead 
 100 kilometers in diameter. The height of the atmosphere is 
 unknown ; it is generally given as 50 or 60 kilometers, but 
 
CHEMICAL MiOPEltTlES OF AIR. 179 
 
 observations upon the zodiacal light and upon meteoric show- 
 ers prove that it may be from 320 to 340 kilometers in height. 
 As we rise from the earth, the density of the air diminishes 
 rapidly, according to Marriotte's law ; so that one half of it 
 is within four and one half kilometers of the surface. The 
 barometer shows that the weight of the air fluctuates within 
 narrow limits, the column of mercury in this instrument 
 varying sometimes as much as 60 millimeters in height. 
 
 229. Chemical Properties. Air is a mixture of oxy- 
 gen and nitrogen gases. This may be ascertained both by 
 
 Fig. 40. Lavoisier's Experiment. 
 
 analysis and by synthesis. The former method is the one 
 by which Lavoisier first established the composition of the 
 air. His experiment, now a classic one in chemistry, was 
 thus performed : a glass balloon with a long neck, bent as 
 shown in Fig. 40, was partially filled with mercury and placed 
 on a furnace. The neck passed down under the surface of 
 the mercury in an adjoining vessel, and then up into a bell- 
 glass also full of air whose mouth was sealed by the mer- 
 cury. On raising the temperature of the mercury to near 
 the boiling point, a red powder began to accumulate upon 
 its surface, the volume of the air proportionally diminish- 
 ing ; until, at the end of twelve days, the contraction of vol- 
 
180 
 
 ume ceased, and the experiment was concluded. The gas 
 contained in the apparatus was proved to be nitrogen ; and 
 by collecting the red powder and heating it, as in Fig. 17, 
 the mercury was reproduced and a gas evolved which had 
 all the properties of oxygen. 
 
 This experiment was qualitative ; an approximately quan- 
 titative experiment may be made by taking a graduated tube 
 full of air, placing in it a ball of phospho- 
 rus cast on the end of a wire (Fig. 41), and 
 immersing its mouth in mercury. By the 
 slow combustion of the phosphorus, the ox- 
 ygen will be removed, and the mercury 
 will rise to fill the space it previously occu- 
 pied. The nitrogen will be left in the tube. 
 Knowing the original volume of air, its 
 composition may be easily calculated. A 
 still more accurate analysis may be made 
 by means of the eudiometer. Fig. 42 rep- 
 resents a convenient form for the lecture-room, known as 
 Yolta's eudiometer. It consists of a strong cylinder of glass, 
 closed above and below by stop-cocks, the lower one carrying 
 a funnel for convenience of. filling, the upper one a cup for 
 holding water, into which may be screwed the long gradu- 
 ated tube, shown in the figure. To make an analysis of air, 
 a given portion, say 200 cubic centimeters, is introduced into 
 the eudiometer previously filled with water and standing 
 on the water-cistern by means of the measuring glass shown 
 on the right. Sufficient hydrogen to combine with all the 
 oxygen, say 100 cubic centimeters, is then added, the lower 
 cock is closed, and an electric spark passed through the 
 mixture from the small ball attached to the upper cap. The 
 hydrogen and oxygen unite, and, on opening the lower cock, 
 the water will enter to take the place of the gas which has 
 disappeared. The long graduated tube is now filled with 
 water, inverted in the top cup of water, and screwed to its 
 
ANALYSIS OF AIR. 
 
 181 
 
 place. The top cock is DOW opened, and, by depressing the 
 apparatus in the cistern, the remaining volume of gas will 
 pass into this tube and may be measured. 
 Assuming that it measures 174 cubic cen- 
 timeters, then the volume of gas which 
 has disappeared must be 300174 or 126 
 cubic centimeters. But this 126 cubic 
 centimeters must be two thirds hydrogen 
 and one third oxygen, this being the ratio 
 in which these two gases combine by vol- 
 ume. One third of 126 is 42 ; hence 200 
 cubic centimeters of air contain 42 cubic 
 centimeters of oxygen, and 100 volumes 
 contain 21 volumes of oxygen. 
 
 The most accurate of the earlier analy- 
 ses of air were made by Dumas and Bous- 
 singault, by drawing pure dry air over 
 red-hot copper. The increase in the mass 
 of the copper gave the mass of the oxy- 
 gen, and the increased mass of the ex- 
 hausted globe that of the nitrogen drawn 
 into it. In this way the composition of the 
 air by mass was directly, and by volume 
 indirectly, determined to be as follows : 
 By tnass. By volume. 
 
 Oxygen 23-0 20-8 
 
 Nitrogen 77-0 79-2 
 
 100-0 100-0 
 
 The air of different localities, though nearly constant in com- 
 position, is not absolutely so ; the oxygen may diminish from 
 21 volumes to 20-9, and in rare cases even to 20'3. 
 
 That the air is merely a mechanical mixture of its con- 
 stituents, and not a chemical compound, is proved by the 
 following considerations : 1st, its components are not united 
 in the ratio of their atomic masses ; 2d, the properties of air 
 
 13 
 
 Fig. 42. Volta's Eudi- 
 ometer. 
 
182 fXORGJXIC CHEMISTRY. 
 
 are such as might properly be expected of a mixture ; 3d, 
 each gas dissolves in water independently of the other ; aud 
 4th, no change of volume or evolution of energy appears 
 when air is made artificially by placing together oxygen and 
 nitrogen. 
 
 Moreover, the same conclusions follow from the results of 
 liquefying air. Its critical temperature is not constant, but 
 varies between 140-8 and 143 just as a mixture would 
 do. The boiling point rises gradually, the nitrogen evaporat- 
 ing the more rapidly. By proper treatment two layers may 
 be obtained, each having its own meniscus. 
 
 EXPERIMENTS. A mixture of oxygen and nitrogen, in the pro- 
 portion of one volume of the former gas to four of the latter, made in 
 a jar over the water-cistern, acts, in reference to combustible bodies, 
 precisely like common air. The contrast between air and its constit- 
 uents may be shown by taking three jars, one of nitrogen, one of oxy- 
 gen, and a third of the artificial air, made as above, and introducing 
 into them successively a lighted taper with a long wick. In the first 
 jar it will be extinguished, in the second provided a spark is left on 
 the wick it will be relighted, and in the third it will burn normally, 
 as in the outside air. 
 
 Water, on being boiled, loses the air which it has dissolved. On 
 collecting and analyzing this air, it is found to be richer in oxygen 
 than common air, having 32 per cent of this gas and 68 of nitrogen. 
 As the coefficient of solubility of both these gases is known, it is easy 
 to calculate what the composition of the dissolved gases should be, on 
 the supposition that the air is a mixture. Calling the air one fifth 
 oxygen and four fifths nitrogen, and the coefficient of solubility of 
 oxygen -046 and of nitrogen -025, we have : 
 
 Solubility calcitlaled. Solubility obserrcd. 
 Oxygen -046 X = '0092 or 31-5 32 
 
 Nitrogen -025 X $ = '0200 or 68-5 68 
 
 0292 100-0 100 
 
 This correspondence establishes the fact of mixture, since every 
 chemical compound has a specific solubility of its own. This larger 
 percentage of oxygen in the air dissolved by water, it may here be 
 observed, is essential to the life of fishes. 
 
COMPOSITION OF AIR. 
 
 183 
 
 The relative density of oxygen being to that of nitrogen 
 as 16 : 14, it might be expected that they would separate, 
 the denser oxygen accumulating near the earth. But we 
 have seen that all molecules are in constant motion ; and 
 hence that all gases readily permeate or diffuse into each 
 other independently of their density. The perfection of this 
 diffusion is shown in the fact that the variation in the com- 
 position of the air is as slight as analysis has showed it to be. 
 
 EXPERIMENT. The relative densities of oxygen and nitrogen, as 
 well as their opposite action upon flame, may be well shown by the 
 
 apparatus given in Fig. 43. Two bell- 
 glasses are filled, the one with oxygen, 
 the other with nitrogen, closed by plates 
 of glass and placed together, the oxy- 
 gen lowest, as shown in the cut. On 
 removing the stopper of the upper jar 
 and the plates between the two, and 
 introducing a lighted taper having a 
 long wick, the flame is extinguished in 
 the nitrogen but relighted again if a 
 spark be left on the wick as it de- 
 scends into the oxygen. This may be 
 repeated several times before the gases 
 become mixed by diffusion. 
 
 Fig. 43. Properties of N and O 
 contrasted. 
 
 But besides these two chief com- 
 ponents of the air, it contains oth- 
 er substances in small quantity, 
 which are quite as essential. These are aqueous vapor, car- 
 bon di-oxide, and ammonia. The aqueous vapor varies very 
 widely in amount, depending upon various conditions, espe- 
 cially on temperature. The quantity of moisture in the air 
 is measured by the hygrometer ; air is said to be saturated 
 when it contains all the moisture it can hold at any given 
 temperature ; thus at 0, one cubic meter is saturated by 5 -4 
 grams of water, at 10 by 9 '74 grams, and at 25 by 22'5 
 grams. But the air in seldom entirely saturated ; 60 per 
 
184 IXORGJXIC CHEMISTRY. 
 
 cent is regarded as the healthy mean; but it may contain 
 only one fifteenth of the saturating quantity, as is the case 
 on the Red Sea during a simoon. When the air is cooled, 
 the excess of moisture falls as rain ; thus one cubic meter at 
 25 cooled to 10 would deposit 22*5 9 '74 or 12 '70 grams 
 of water. The carbon di-oxide of the air, the next largest 
 constituent, exists in minute quantity relatively about one 
 twentieth of one per cent though the absolute quantity is 
 large, being about 3,000 billion kilograms. It is estimated 
 by drawing a known volume of air through a tube contain- 
 ing potassium hydroxide, which absorbs it and thus increases 
 in mass. This minute amount of carbon di-oxide is the sole 
 source of the carbon of vegetation. It is produced by com- 
 bustion, by the respiration of animals, by fermentation, and 
 by decay. The ammonia present in air exists in even more 
 minute quantity, being only from one to fifty parts in a mill- 
 ion of air, according to the locality. This ammonia \vashed 
 down by the rain plays an important part in yielding nitro- 
 gen to vegetation. Other and variable constituents there 
 are in the air, such as gaseous products of various kinds, 
 dust, and organic matters. The latter include those micro- 
 scopic germs which produce malaria and thus may give rise 
 to specific diseases. Miller gives the average composition 
 of the air of England as follows : 
 
 Oxygen ........................ 20-61 
 
 Nitrogen ........................ 77-95 
 
 Carbon di-oxido .................. -04 
 
 Aqueous vapor .................. 1-40 
 
 Nitric acid .......... ^ 
 
 Ammonia .......... I .......... traces. 
 
 Gaseous hydrocarbons J 
 
 And in towns : 
 
 Hydrogen sulphide | _ 
 Sulphurous oxide. , * 
 
 100-00 
 
/A' /;/'./ //.may OF AM MOM A. 185 
 
 NITROGEN AND HYDROGEN. 
 
 HYDROGEN NITRIDE OR AMMONIA. Formula H 3 N. Molecu- 
 lar mass 17*01. Molecular volume 2. Relative density 8*5. 
 The mass of 1 liter is 0*7635 gram (8*5 criths). 
 
 230. History. Ammonia was known to the alchemists; 
 it was mentioned by Raymond Lully in the 13th century, 
 and by Basil Valentine in the 15th. It was first obtained 
 as a gas by Priestley in 1774, and called alkaline air. 
 Scheele in 1777 showed that it contained nitrogen, and 
 Berthollet analyzed it in 1785. The name ammonia was 
 given by Bergman in 1782, from that of its chloride, then 
 called sal-ammoniac ; which substance was largely produced 
 by burning camel's dung in the Libyan desert, near a temple 
 of Jupiter Ammon. It occurs sparingly in nature, traces 
 of it being found in the air, in soils, and in most mineral 
 waters. It exists also in certain minerals found in volcanic 
 regions, and in the fluids of animals and plants. 
 
 231. Preparation. Ammonia can not ordinarily be 
 produced by the direct union of its constituents ; though by 
 suitable means they may be made to combine indirectly. 
 When for example, nitric acid acts upon zinc, the hydro- 
 gen which is set free in the atomic form and hence with 
 a stronger than molecular attraction hence called nascent 
 hydrogen unites at once with the nitrogen, according to 
 the following equation : 
 
 (HN0 3 ) 9 + Zn 4 = (Zn(NO s ) 2 ) 4 + (H 2 O), + ~H 3 N 
 
 Nitric acid. Zinc. Zinc nitrate. Water. Ammonia. 
 
 Under the influence of the silent electric discharge, nitrogen 
 and hydrogen may combine to form ammonia. The electric 
 spark in moist air produces ammonium nitrate ; and small 
 quantities of ammonium nitrite are formed by the evapora- 
 tion of water, by ordinary combustion, by the rusting of iron 
 and by the electrolysis of water. Hence ammonium nitrite 
 is a normal constituent of the atmosphere. 
 
The compounds of ammonia found in commerce are ob- 
 tained either by the destructive distillation of animal matters 
 or from the so-called ammoniacal liquors of the gas-works, 
 obtained in the distillation of coal. Ammonia itself is pre- 
 pared by acting upon two parts of ammonium chloride the 
 sal-ammoniac of commerce with one part of quick-lime. 
 The reaction is as follows : 
 
 (NH,HC1) 2 + CaO = CaCl a + K,O 4- (H,N) 2 
 
 The gas being lighter than air, may be collected by upward 
 displacement. 
 
 232. Properties. Ammonia is a colorless gas with a 
 pungent odor and a strongly alkaline reaction upon test- 
 papers. It is considerably lighter than air, its specific grav- 
 ity being 0'59. Subjected to a pressure of six and a half 
 atmospheres at 10, or to a cold of 40, it condenses to a 
 colorless liquid of specific gravity 0*6362, which freezes at 
 75 and boils at 35.7. The critical temperature is 130 
 and the critical pressure 115 atmospheres. It is soluble in 
 water to an extraordinary degree ; one volume of water at 
 .0 absorbing 1,149 volumes of ammonia gas, forming the so- 
 called aqua amrnonise. At 15 one volume of water absorbs 
 783 volumes of the gas. This solution has the well-know r n 
 properties of the gas, has a specific gravity of 0-85, and 
 evolves the ammonia again upon heating. For the prepara- 
 tion of the ammonia solution, the same apparatus may be 
 employed as was used for hydrochloric acid, Fig. 11. 
 
 Chemically, ammonia gas has a strong, but transient alka- 
 line reaction upon vegetable colors, whence the name volatile 
 alkali, sometimes applied to it. Though containing so much 
 hydrogen it is not combustible in air at ordinary tempera- 
 tures, though it burns in oxygen. A burning candle im<- 
 mersed in the gas is extinguished and animals die in it at 
 once, owing to the extreme irritation it causes. Under the 
 influence of heat or of the electric spark it is decomposed. 
 
PROPERTIES (>r AM MOM A. 
 
 187 
 
 As it contains trivulent nitrogen it t-an unite directly with 
 other bodies, the nitrogen then becoming a pentad. 
 
 Ammonia gas is an exothermic compound, the reaction 
 
 iemg (H 2 ) S +N 2 = (H 3 N) 2 + 11,800 water-gram degrees, 
 all the substances being gaseous. The solution of the gas 
 in water evolves 8,800 heat-units ; so that the heat of forma- 
 tion of the aqueous solution is the sum of these values, or 
 20,600 heat-units. 
 
 EXPERIMENTS. The indirect formation of ammonia may be very 
 beautifully shown by mixing in a gas-holder five volumes of hydro- 
 gen and two volumes of ni- 
 trogen di-oxide, and passing 
 a stream of the mixed gases 
 through a bulb Lube contain- 
 ing platinized asbestus, as 
 shown in Fig. 44. So long 
 as the bulb is cold, the escap- 
 ing gases redden blue litmus 
 paper; but on warming the 
 bulb, the surface action of 
 the platinum begins, the as- 
 
 Fig. 44. Synthesis of Ammonia. 
 
 bestus often becoming red-hot, and the pungent alka- 
 line fumes of ammonia appear and turn the red paper 
 back again to blue. 
 
 The absorption of ammonia gas by water may be | 
 illustrated by filling a large bottle with the gas by 
 upward displacement, and closing the mouth with a 
 rubber cork through which a glass tube passes, drawn 
 to a fine point at the lower end. On breaking this 
 point beneath the surface of the water, as shown in 
 Fig. 45, the water will enter the bottle with great vio- 
 lence, sometimes crushing it. If the water be colored 
 with red litmus solution, it will become blue as 
 it enters the bottle, thus showing at the same 
 time the alkalinity of the gas. 
 
 The fiu:ilit y with which ammonia gas may be 
 expelled from its solution by heat, and the ease 
 
 with which it may be condensed to a liquid by pressure, have been 
 made use of by F. Carre, of Paris, for the production of artificial ice. 
 
 FIg ' 
 
188 
 
 tlis apparatus is represented in Fig. 46. It consists of a generator 
 and receiver made of iron boiler-plate, the receiver being conical in 
 
 shape, both connected by means 
 of a strong iron tube. In the 
 generator is placed a strong solu- 
 tion of ammonia saturated at 0, 
 and this is heated over a large 
 gas flame to 130, the receiver 
 meanwhile being immersed in 
 cold water. The ammonia gas is 
 driven off and is condensed to 
 the liquid state in the receiver, 
 as soon as the pressure passes ten 
 atmospheres. Into the cylindri- 
 cal space in the receiver a closely- 
 fitting vessel filled with water is 
 
 Fig. 46. F. Carre's Ammonia Ice- now placed, and the apparatus is 
 machine. 
 
 reversed, the generator being im- 
 mersed in the water. The liquefied ammonia passes again into the 
 gaseous state and is re-absorbed by the water in the generator. But 
 in this evaporation great cold is pro- 
 duced and the vessel of water is soon 
 frozen. A larger and continuous ap- 
 paratus on the same principle has also 
 been patented by M. Carre. 
 
 The combustion of ammonia in oxy- 
 gen may be conveniently shown by 
 the apparatus represented in Fig. 47. 
 The gas is obtained by heating a strong 
 solution of ammonia in the retort, and 
 is conducted through a narrow glass 
 tube to a point just at the upper edge rig. 47. Combustion of Ammonia 
 of a narrow glass cylinder, through in Oxygen, 
 
 which passes a current of oxygen supplied by the flexible tube. The 
 jet of ammonia gas as it issues, being surrounded by an atmosphere 
 of oxygen, takes fire on the approach of a lighted taper, and burns 
 with a peculiar yellowish flame. 
 
 233. Composition. The composition of ammonia may 
 be determined by introducing a given volume of the gas into 
 a graduated tube over mercury, and passing electric sparks 
 
x or AMMOMA. 189 
 
 through it. It is decomposed and doubles in volume ; the 
 pungency and alkalinity of the gas disappear, and it is no 
 longer soluble in water. By eudiometry, the volumes of its 
 constituents are obtained thus : assuming that 100 cubic 
 centimeters of ammonia are taken, they will expand to 200 
 cubic centimeters on passing the spark ; 100 cubic centime- 
 ters of oxygen are now added and the spark again passed ; 
 the 300 cubic centimeters become reduced to 75 cubic centi- 
 meters, 225 cubic centimeters having disappeared. Of this 
 225 cubic centimeters two thirds, or 150 cubic centimeters, 
 must be hydrogen and 75 cubic centimeters oxygen. Sub- 
 tracting the excess of oxygen taken, 10075, or 25 cubic 
 centimeters, from the residual 75 cubic centimeters left in 
 the eudiometer, the remainder, 50 cubic centimeters, is nitro- 
 gen. Hence the 200 expanded volumes consist of 150 vol- 
 umes of hydrogen and 50 of nitrogen ; and ammonia gas 
 consists of three volumes of hydrogen and one volume of 
 nitrogen condensed into two volumes. 
 
 234. Tests. Free ammonia is easily detected by its odor, 
 by its alkalinity, and by the fumes which it gives when a rod 
 moistened with hydrochloric acid is brought near it. When 
 combined, it may be set free by quicklime and then tested. 
 
 DlAMINE H 4 N. 2 AND HYDROXYLAMINE (OH)H 2 N. - These 
 
 two compounds are nearly related to ammonia. The former 
 is a stable gas having a peculiar pungent odor, and is very 
 soluble in water. It reduces silver and copper salts to the 
 metallic state and forms a hydrate H 4 N 2 . H.,O. The latter, 
 produced by reducing nitric acid with tin, forms salts analo- 
 gous to those formed by ammonia, which salts have a reduc- 
 ing action like those of diamine. Hydrazoic acid, HN :j , dis- 
 covered by Curtius in 1890, is a highly explosive gas. 
 
 OXIDES AND ACIDS OF NITROGEN. 
 
 235. The oxides formed by nitrogen are five in num- 
 ber ; those normally formed, in w r hich it has a valence of 
 
190 
 
 one, three, aiid five ; and those in which the nitrogen atom* 
 are directly united, and which may be viewed as free radi- 
 cals. Their names, together with their corresponding acids, 
 
 are as follows : 
 
 Oxides. Acids. 
 
 Hyponitrous oxide N' 2 O Hyponitrous acid HN'O 
 
 Nitrogen di-oxide (nitrosyl) N'^O., 
 
 Nitrous oxide N'" 2 O 3 Nitrous acid HN'"<>, 
 
 Nitrogen tetr-oxide (nilryl) N V . 2 O 4 
 
 Nitric oxide NV 2 O 5 Nitric acid HN^O, 
 
 NITRIC OXIDE. Formula N 2 O 5 . Molecular mass 107 -82. 
 
 236. History and Preparation. Nitric oxide, called 
 also nitrogen pentoxide and nitric anhydride, was first ob- 
 tained by Deville in 1849. It is prepared by the action of 
 phosphoric oxide on nitric acid, or better of nitryl chloride 
 upon silver nitrate at 60. 
 
 237. Properties. Nitric oxide is a colorless, transpar- 
 ent solid, crystallizing in right rhombic prisms. It melts at 
 30 and boils at 47. It is quite unstable, sometimes ex- 
 ploding spontaneously. It reacts energetically with water, 
 producing nitric acid, thus : 
 
 NA + H 2 = (HNO :t ), 
 
 HYDROGEN NITRATE, OR NITRIC ACID. Formula HNO.,. 
 Molecular mass 62*89. Molecular volume 2. Relative den- 
 sity 31 '5. TJie mass of om liter of nitrw-acid vapor is 2*82 
 grams (31*5 criths). 
 
 238. History. Nitric acid was known to Geber, an 
 alchemist of the 8th century ; Raymond Lully in 1225 de- 
 scribed a method for preparing it. Cavendish, in 1785, 
 first determined its true composition synthetically. 
 
 239. Formation. When strong electric sparks are 
 passed through a confined portion of air, standing over a 
 solution of potassium hydroxide, the volume gradually less- 
 ens and potassium nitrate may be detected in the liquid. So 
 
PREPARATION or MTRIC ACID. 
 
 191 
 
 when o/one acts upon the nitrogen of the air, upon ammo- 
 nia, or upon the lower oxides of nitrogen, water being pres- 
 ent, nitric acid is produced. Again, when animal matters 
 containing nitrogen are allowed to decompose in presence 
 of weak alkaline bases, nitrates of these bases are produced. 
 In this way artificial niter-beds are made. 
 
 24O. Preparation. Nitric acid is always produced by 
 the distillation of a nitrate generally sodium or potassium 
 nitrate with sulphuric acid. The reaction may thus be rep- 
 resented : 
 
 Na(NO 8 ) + H 2 (SO 4 ) = HNO 3 + HNa.(SO 4 ) 
 
 Sodium 
 nitrate. 
 
 Sulphuric 
 
 acid. 
 
 Xitric 
 acid. 
 
 Hydro-sodium 
 sulphate. 
 
 EXPERIMENTS. The distillation of nitric acid may be conducted 
 in the apparatus given in Fig. 48. The sodium nitrate is placed in 
 the retort on the right, and upon it is poured through the tuhulure, 
 by means of a funnel, an equal weight of sulphuric acid. The neck 
 
 Fig. 48. Preparation of Nitric Acid. 
 
 of the retort passes into that of the receiver for a considerable dis- 
 tance, and the receiver, supported over a beaker, is covered with pa- 
 per to distribute equally the water which runs from the vessel above, 
 and which is intended to keep it cool. On lighting the burner, the 
 mass liquefies, red fumes appear, and a more or less colored liquid 
 accumulates in the receiver. By changing this, collecting the acid 
 which comes over during the middle of the operation separately, a 
 colorless acid is obtained. 
 
192 
 
 In the arts the operation is conducted in a cast-iron retort, as shown 
 in Fig. 49. A less concentrated acid is used for the decomposition, 
 
 Fig. 49. Commercial Preparation of Nitric Acid. 
 
 and two molecules of sodium nitrate are treated with one of sulphuric 
 acid, normal sodium sulphate remaining in the retort, thus: 
 (NaNO,) 2 + H,(S0 4 ) - Na 2 (8O 4 ) + (HNO S ) 2 
 The nitric acid distills over and is condensed in the earthen-ware 
 receivers. 
 
 241. Properties. Nitric acid is a colorless, fuming, cor- 
 rosive, strongly acid liquid, having a specific gravity of 1'52. 
 Cooled to 55 it freezes, and heated to 86, it boils, suffer- 
 ing a partial decomposition. It is also readily decomposed 
 by light. Chemically, it is a powerfully oxidizing agent, 
 acting on most of the metals with great vigor. Nitrogenous 
 animal substances, such as parchment, silk, and wool, are 
 colored strongly yellow by nitric acid. And many non-nitro- 
 genous vegetable substances, such as glycerin, cotton, and 
 sugar, are converted by it into violently explosive bodies. 
 
 The commercial acid known as aqua-fortis is of two 
 sorts, called single and double. Double aqua-fortis has a 
 specific gravity of 1*36, and single of 1*22, being one half 
 as strong. A mixture of nitric acid and water of density 
 1-42 has a definite boiling point, 120-5. But it is not a 
 definite hydrate, the boiling point being uniform only under 
 a constant barometric pressure. 
 
TESTS FOR CITRIC ACID. 193 
 
 Nitric acid is a monobasic acid, and can form only normal 
 salts, represented by M(NO 3 ), M being any monad metal. 
 But besides this, which is the di-meta-nitric acid, two others 
 are possible, represented by H ;1 NO 4 , mono-meta-nitric acid, 
 and H 5 NO 5 , ortho-nitric acid. Lead mouo-meta-nitrate Pb".< 
 (NO 4 ). 2 , and bismuth mono -meta- nitrate, Bi'"NO 4 usually 
 called basic nitrates are well known salts; and a hydro- 
 bismuthous ortho-nitrate, H 2 Bi'"NO 5 , has also been produced. 
 
 242. Tests. When free, nitric acid reddens litmus pow- 
 erfully, bleaches indigo - solution readily, and evolves red 
 fumes on introducing a fragment of copper. These reactions 
 are obtained from nitrates after treatment with sulphuric 
 acid. Moreover, nitrates deflagrate when thrown on burn- 
 ing charcoal. 
 
 Nitric acid is used in the arts for etching upon metals, 
 for oxidizing various substances, for forming various substi- 
 tution products, such as nitro-benzol and picric acid, and for 
 the preparation of nitro-glycerin, gun-cotton, etc. 
 
 243. Aqua Regia. Neither nitric nor hydrochloric acid 
 alone has the power of dissolving gold, the rex metallorum 
 of the ancients. But a mixture of one volume of nitric 
 and three of hydrochloric acid contains free chlorine and 
 possesses this property, whence its name aqua regia. On 
 submitting this mixture to a gentle heat, two exceedingly 
 volatile liquids are obtained ; one of these is nitryl chloride 
 (NO 2 )C1, the other nitrosyl chloride (NO)C1. Neither of 
 these attack gold. 
 
 NITROGEN TETR-OXIDE. Formula N 2 O 4 or -^-Q 2 I O. Molec- 
 ular mass 91 '86. Molecular volume 4 (Dissociation*). 
 
 244. Preparation. Nitrogen tetr-oxide may be formed 
 directly by mixing together two volumes of nitrogen dioxide 
 with one volume of oxygen ; although it is generally pre- 
 pared by heating perfectly dry lead nitrate: 
 
 ,), - (PbO) 2 + (N,0j, + O, 
 
194 lyOBdAXJC- CHEMISTRY. 
 
 On passing the vapors through a freezing mixture, they 
 are condensed to a liquid, or if perfectly dry, to a white crys- 
 talline solid which melts at 9. As the temperature rises, 
 the color of the liquid changes from yellow to deep orange, 
 until it reaches 22, when it boils, evolving an orange vapor 
 which at 40 is almost black. This substance furnishes an 
 interesting example of dissociation at ordinary temperatures. 
 The theoretical vapor-density for N. 2 O 4 is 45*9, while that for 
 NO 2 is 22-9. At the temperature of 22, the boiling point 
 of the liquid, this relative vapor density is 38 ; showing that 
 about 34 per cent of the N.,0^ is dissociated. At 150 the 
 vapor-density becomes constant at 22*9 and all the molecules 
 consist of NO 2 . This progressive dissociation may be traced 
 by the change in color ; N 2 O 4 being colorless, while NO 2 is a 
 deep brown, darkening as above as the temperature rises. 
 By the action of cold water it yields nitric and nitrous acids : 
 
 _ 2Q 
 NO p ' H p H p H J 
 
 And hence its constitution must be ON O NO.,. It is an 
 energetic oxidizing agent, many substances burning in its 
 vapor. It combines directly with chlorine to form nitryl 
 chloride (NO.JC1. 
 
 NITROUS OXIDE AND ACID. Formulas N,O 3 and HNO.,. 
 Molecular mass of tJie oxide 75 '90; of the acid 46 '93. 
 
 245. Preparation. Nitrous oxide may be prepared 
 either directly by the union of four volumes of nitrogen di- 
 oxide with one volume of oxygen, or indirectly by the reduc- 
 tion of nitric acid by starch or by arsenous oxide : 
 
 (HN0 8 ), + As,0 ;{ = (MAs0 3 ) 2 + N. 2 O :( 
 By passing the evolved vapors through a freezing mix- 
 ture, the nitrous oxide condenses to a very unstable blue 
 liquid, which reacts with water, producing nitrous acid ; this 
 is also a blue liquid, which may be preserved at low temper- 
 
NITROUS ACID AND NITRITES. 
 
 195 
 
 atures unaltered, but is decomposed readily into nitric acid, 
 water, and nitrogen di-oxide, thus : 
 
 (HN0 2 ), = HN0 3 + H 2 + N 2 O 2 
 
 Nitrous acid forms salts called nitrites ; the mono-meta 
 form is monobasic, the ortho form, tri basic. Potassic mono- 
 meta-uitrite is KNO 2 ; this is the more common form of ni- 
 trite. Hydro-plumbic ortho - nitrite HPb"NO 3 and normal 
 plumbic ortho - nitrite Pb" 3 (NO 3 ) 2 are examples of actually 
 known ortho-salts. 
 
 EXPERIMENT. The formation of nitrous compounds by the oxida- 
 tion of ammonia may be illustrated by the apparatus shown in Fig. 
 oO. A flask is one third filled with strong ammonia solution, and 
 placed in a cup of sand on the gas fur- 
 nace. A spiral of platinum wire one 
 third of a millimeter thick formed by 
 winding it about a pencil is attached 
 to a cork, heated to redness and plunged 
 at once into the flask. At the same time 
 oxygen gas is admitted through a glass 
 tube which just dips into the liquid. The 
 spiral glows brilliantly in the gaseous 
 atmosphere, producing at first white 
 fumes of ammonium nitrite and then 
 red vapors of nitrous oxide. When the 
 ammonia gas is freely evolved, it forms 
 often an explosive mixture with the 
 oxvgen; this, ignited by the coil, gives 
 a slight puff. The coil cooled by this 
 explosion soon again becomes heated, and the operation is repeated. 
 Sometimes the explosions are minute and take place rapidly within 
 the flask, producing a tone like that of the hydrogen tube. 
 
 NITROGEN DI-OXIDE. Formula N.,O 2 . Molecular mass 59*94. 
 Molecular volume 4 (Dissociation). Relative density 14*98. 
 The mass of one liter is 1*34 grams (15 crith*). 
 
 24C>. History. Nitrogen di-oxide, though noticed by 
 Hales, was first investigated by Priestley in 1772. 
 
 Fig. 50. Combustion of N 
 ^203. 
 
196 IXORdAyiC CHEMISTRY. 
 
 247. Preparation. It may be prepared by the action 
 of dilute nitric acid upon metals, such as copper, silver, or 
 mercury, or upon ferrous sulphate. With copper, the reac- 
 tion is as follows : 
 
 Cu, + (HN0 3 ) 8 = (Cu(NOO,), + (H,,0) 4 + N,O, 
 
 248. Properties. Nitrogen di-oxide is a colorless gas, 
 having a specific gravity of 1*039. Its critical temperature 
 is 93-5 and its critical pressure 71 '2 atmospheres. Under 
 atmospheric pressure it boils at 153*6 and solidifies like 
 snow. There is an anomaly in its vapor-density, since its 
 molecule, if saturated, occupies four volumes instead of two. 
 This is explained by the supposition that even at ordinary 
 temperatures the molecule is separated into two others, each 
 of which occupies the normal volume. This is known to 
 be the case with some other bodies, alike irregular in their 
 vapor-density. One volume of this gas dissolves in about 
 twenty of water at 15. 
 
 Nitrogen di-oxide is strongly endothermic, the reaction 
 being 
 
 N 2 + O 2 = N. 2 O 2 - 43,000 water-gram degrees. 
 
 Hence it may be exploded by detonating a little mercuric 
 fulminate in it (Berthelot). So too, combustion in this gas 
 evolves more heat than combustion in oxygen ; a result ex- 
 plicable only on the supposition that to separate N and O 
 from each other in the N 2 O 2 molecule requires less energy 
 than to separate O and O from each other in a molecule of 
 oxygen O 2 . 
 
 Nitrogen di-oxide extinguishes the flame of a caudle intro- 
 duced into it ; but phosphorus well ignited burns in it with 
 great brilliancy, being able to take away its oxygen. It 
 has a strong attraction for oxygen, combining with half its 
 volume of this gas to form red fumes of nitrogen tetr-oxide, 
 N 2 O,. It also unites directly with chlorine, producing nitro- 
 syl chloride (NOjCl. 
 
NITROGEN DIOXIDE. 
 
 197 
 
 EXPERIMENTS. To prepare nitrogen di-oxide, nitric acid of spe- 
 cific gravity 1-2 prepared by diluting the ordinary acid with twice 
 
 Fig. 51. Combustion of CS2 
 and N2O2. 
 
 Fig. 52. Action of N2O2 and N2Os 
 on Litmus Paper. 
 
 its volume of water is poured upon copper clippings contained in a 
 two-necked bottle like that used for obtaining hydrogen (Fig. 2). The 
 gas must be collected over water. 
 
 A lighted candle or burning sulphur is 
 extinguished when plunged into the gas. 
 Phosphorus just ignited is also extin- 
 guished ; but if allowed to get fully on fire 
 it burns brilliantly. If a few drops of car- 
 bon disulphide be poured into a jar of 
 the gas and agitated, the mixture will take 
 fire on the approach of a flame, as shown 
 in Fig. 51, burning with a vivid, intensely 
 actinic light. 
 
 On removing the cover of a jar of nitro- 
 gen di-oxide (Fig. 52), and immersing in the 
 gas a long slip of blue litmus paper, the 
 lower end of the paper in the pure gas will 
 be unaffected, while the upper end in con- 
 tact with the red fumes produced by union 
 with the oxygen of the air, will be turned red. A somewhat large 
 bell-glass filled with this gas gives voluminous clouds of the brown- 
 red vapors when its cover is removed, as shown in Fig. 53. This 
 experiment demonstrates the existence of free oxygen in the air, the 
 N 2 O 2 combining with it to yield N 2 O 3 . 
 
 14 
 
 Fig. 53. N 2 2 aud air. 
 
198 
 
 INORGANIC CHEMISTli Y. 
 
 HYPONITROUS OXIDE. Formula N 2 O. Molecular mass 43*98. 
 Molecular volume 2. Relative density 21*99. The mass of 
 one liter is 1*97 grams (22 criths). 
 
 249. History. Hyponitrous oxide was discovered by 
 Priestley in 1776. It was more minutely examined by 
 Davy in 1809, who discovered its exhilarating property. 
 It was first used as an anaesthetic by Wells in 1845. 
 
 250. Preparation. Hyponitrous oxide maybe prepared 
 by reducing nitric acid with zinc or stanuous chloride ; but 
 it is generally obtained by decomposing ammonium nitrate 
 by heat, according to the equation : 
 
 The gas, being heavier than air, may be collected by dis- 
 placement. It may also be collected over warm Water. The- 
 apparatus used is shown in Fig. 54. 
 
 Fig. 54 Preparation of Hyponitrous OxicU-. 
 
 251. Properties. Hyponitrous oxide, sometimes called 
 nitrous oxide, is a colorless gas, inodorous, but with a dis- 
 tinctly sweet taste. It is one half heavier than air, its spe- 
 cific gravity being 1*527. Cooled to 88 or subjected to 
 a pressure of thirty-two atmospheres at 0, it is condensed 
 to a colorless mobile liquid of specific gravity 0*937, which 
 freezes at 101. Its critical temperature is 35*4 and its 
 
FROrERTIKS OF HYrOMTliOUH OXIDE. 199 
 
 critical pressure is 75 atmospheres. The liquid also freezes 
 by its own evaporation when allowed to escape into the open 
 air, producing a snow-like mass, which, mixed with carbon 
 disulphide and placed in a vacuum, produces the very low 
 temperature of 140. The gas is quite soluble in water, 
 one hundred volumes dissolving seventy-eight volumes at 
 15. It is more soluble in alcohol and in alkaline solutions. 
 
 Burning bodies have their combustion accelerated in hypo- 
 nitrous oxide. A candle having a spark upon the wick is 
 relighted in it, much as in oxygen. Phosphorus and sulphur 
 burn in it with great splendor. The gas is decomposed, and 
 its oxygen unites with the combustible. When breathed in 
 moderate quantity it exerts a marked exhilarative action on 
 the system, and hence has been called laughing- gas. Of 
 late years it has come extensively into use as an anaesthetic 
 agent, the inhalation being continued for a longer time. 
 It was with this gas that the property of anaesthesia was dis- 
 covered; a discovery everywhere acknowledged as one of 
 the crowning surgical discoveries of the present century. 
 
 Its composition may be ascertained by passing electric 
 sparks through it, when it separates into two volumes of 
 nitrogen and one of oxygen ; or by exploding it with an 
 equal volume of hydrogen, when its own volume of nitrogen 
 only is left. This oxide, like all the oxides of nitrogen, is 
 an endothermic compound, and hence can not be prepared 
 from its constituents without the addition of energy from 
 some external source. 
 
 252. Hyponitrous Acid. Formula HNO. By reduc- 
 ing a solution of "potassium nitrate with sodium amalgam, 
 potassium hyponitrite is obtained ; and by decomposing silver 
 hyponitrite by hydrogen chloride, the free hyponitrous acid 
 is obtained. It is strongly acid, quite stable, reduces per- 
 manganates, sets free iodine, and yields hyponitrous oxide 
 on dehydration. The silver salt decomposes with explosion 
 above 110. 
 
200 INORGANIC CHEMIST in. 
 
 2. PHOSPHORUS. 
 
 Symbol P. Atomic mass 30*96. Molecular mass 123*84. Mo- 
 lecular volume 2. Valence I, III, and V. Relative detixitt/ 
 61*92. The mass of one liter of phosphorus-vapor is 5*55 
 grams (62 criths). 
 
 253. History. Phosphorus was discovered in 1669, by 
 Brandt, by igniting evaporated urine in closed vessels. One 
 hundred years later, in 1769, G-ahn and Scheele discovered 
 it in bones, and in 1775 proposed a method of preparing it 
 from them. 
 
 254. Occurrence. Phosphorus does not occur free in 
 nature. It exists in combination in the minerals apatite, 
 pyromorphite, wagnerite, etc., which are calcium, lead, and 
 magnesium phosphates, respectively. Vast deposits of cal- 
 cium phosphate occur on many of the Caribbean islands, 
 and near Charleston, S. C. The bones of animals contain 
 calcium phosphate, and this as well as other phosphates are 
 present in their tissues, being derived mostly from the seeds 
 of plants. 
 
 255. Preparation. Phosphorus is prepared by acting 
 upon burned bones with sulphuric acid, leaching off the re- 
 sulting liquid, evaporating it to dryness, and distilling the 
 residue with charcoal. The earthy matter of bones consists 
 of calcium phosphate Ca" 3 (PO 4 ) 2 . By treating this with sul- 
 phuric acid, acid calcium phosphate results, as follows : 
 
 Ca" s (P0 4 ) 2 + (H0 4 ), = (CaSO;x, + H 4 Ca"(PO 4 ), 
 
 Calcium Sulphuric Calcium * Hydro-calcium 
 
 phosphate. acid. xulphate. phosphate. 
 
 This is leached off from the insoluble calcium sulphate, and 
 by evaporation of the solution to dryness is converted into 
 calcium meta-phosphate, thus : 
 
 H 4 Ca"(P0 4 ) 2 = Ca"(PO ;j ), + (H,O) 2 
 and the calcium meta-phosphate distilled with charcoal gives 
 
PREPARATION OF PHOSPHORUS. 201 
 
 phosphorus and calcium phosphate again, according to the 
 equation : 
 
 (Ca"(P0 3 ) 2 ) : , + C IO = Ca" 3 (POJ 2 + (CO) U +P. 
 
 Practically, the bones previously burned and ground very 
 fine are mixed with two thirds of their mass of strong sul- 
 phuric acid diluted with eighteen or twenty parts of water, 
 
 Fig. 55. Preparation of Phosphorus. 
 
 well stirred, and allowed to stand for twelve hours. The 
 clear liquid is then strained from the deposited calcium sul- 
 phate or gypsum, evaporated in a pan to a syrupy consist- 
 ence, mixed with one fifth its mass of charcoal powder, and 
 heated to low redness. The dry mass is then placed in earthen 
 retorts with long necks, and these are raised gradually to 
 bright redness in the furnace shown in Fig. 55, when the 
 phosphorus distills over and condenses in the receivers. The- 
 oretically, the bone ash should yield eleven per cent of phos- 
 phorus, but practically only eight per cent is obtained, unless 
 enough sand is added to form calcium silicate ; then all the 
 phosphorus is set free. 
 
 The crude phosphorus is purified generally by melting it 
 under water and agitating it with a mixture of potassium 
 di-chromate and sulphuric acid. The impurities are oxidized, 
 and the pure liquid phosphorus remains colorless and trans- 
 
202 
 
 INORGANIC CHEMISTRY. 
 
 parent at the bottom of the vessel. It is then ladled into 
 a conical vessel surrounded with warm water, shown in Fig. 
 56, from the bottom of which a tube passes, through a stop- 
 cock, into another tube laid 
 horizontally in a vessel con- 
 taining cold water, which 
 tube can be closed by a 
 
 plug. On opening the cock 
 the tube fills with melted 
 phosphorus, which in the 
 Fig. 56. Casting Phosphorus in Sticks. cold water goon so ]idifies, 
 
 and may be withdrawn as a solid stick by removing the 
 plug. In this form it is brought into commerce. 
 
 256. Properties. Phosphorus is capable of existing in 
 two markedly different allotropic states. Prepared as-above, 
 phosphorus is a colorless, transparent, wax-like solid, hav- 
 ing a specific gravity of 1-83. It melts at 44 to a colorless 
 liquid and boils at 290, yielding a colorless vapor of specific 
 gravity 4'355. It crystallizes from its solution in carbon di- 
 sulphide in the form of the regular dodecahedron (Fig. 57, 1). 
 It is not soluble in water, but 
 dissolves easily in carbon disul- 
 phide, in phosphorous chloride, 
 in alcohol, in ether, and in cer- 
 tain volatile and fixed oils. In 
 the air it oxidizes readily, and 
 hence must be kept under wa- 
 ter. Owing to this slow combus- 
 tion it is luminous in the dark, i rig. 57. 2 
 
 ,11 n i .-, Phosphonis Crystals. 
 
 though a trace of naphtha or 
 
 oil of turpentine in the air prevents this phenomenon, 
 is violently poisonous, and kills by depriving the blooc 
 oxygen. Oil of turpentine is the best antidote. Heated to 
 50 in the air it takes fire and burns vividly, forming phos- 
 phoric oxide. 
 
 It 
 of 
 
HYDROGEN PHOSPHIDE, 203 
 
 In 1848 Schrotter discovered that by heating ordinary 
 phosphorus to 300 in a gas which had no action upon it, it 
 was converted into a chocolate-red powder /5 phosphorus 
 possessing properties entirely different from those previously 
 exhibited. Its specific gravity is 2*14. At 358 it is recon- 
 verted into the variety. It is insoluble in the ordinary 
 solvents of phosphorus, but it may be dissolved in metallic 
 lead by heating in a sealed tube with this metal. On cool- 
 ing it crystallizes out in acute rhombohedral crystals (Fig. 
 57, 2), having a metallic luster, an almost black color, and 
 a specific gravity of 2 -34. It has no. odor, does not oxidize 
 readily in the air, and is not poisonous. It does not take 
 fire until heated to 260. The formation of the red phospho- 
 rus from the white variety is accompanied by the evolution 
 of 19,200 heat-units. Hence the less activity of the former. 
 
 257. Uses. Phosphorus is extensively used in the manu- 
 facture of friction matches. For this purpose the variety 
 is generally employed ; though on account of the frightful 
 disease of the jaw which it causes in the workmen, the ft or 
 red variety is much to be preferred. It is used also in medi- 
 cine and as a rat-poison. Its spectrum is characterized by 
 two green lines, readily seen in the flame of hydrogen which 
 has been passed over phosphorus. 
 
 PHOSPHORUS AND HYDROGEN. 
 
 Three compounds of phosphorus and hydrogen are known : 
 a gaseous compound H,P, a liquid one H 4 P 2 , and a solid one, 
 H 2 P 4 . 
 
 HYDROGEN PHOSPHIDE OR PHOSPHINE. Formula H,P. Mo- 
 lecular mass 33'96. Molecular volume 2. Relative density 
 16-98. The mass of one liter is 1'52 grams (17 frith*). 
 
 258. History. Hydrogen phosphide was discovered in 
 1783 by Gengembre; but its analogy with ammonia was 
 first established by Heinrich Rose in 1832. 
 
204 
 
 INORGANIC CHEMISTRY. 
 
 259. Preparation. It may be prepared by the action 
 of water or of acids upon phosphides : 
 
 Ca 3 P, + (HC1) 6 = (CaCL 2 ) 3 + (H 3 P) 2 
 by the decomposition of so-called hypophosphorous acid : 
 (H(P0 2 H,)) 2 = H 3 P0 4 + H S P 
 
 and by boiling phosphorus with a solution of potassium hy- 
 droxide : 
 
 (HKO) 3 + P 4 + (H.O), - (K(P0 2 H 2 )) 3 + H.P 
 
 260. Properties. Phosphine is a colorless gas, with a 
 nauseous garlic-like odor. It is sparingly soluble in water, 
 is condensable to a liquid, and is neutral in its reaction. Its 
 specific gravity is 1'175. It takes fire readily at 100, burn- 
 ing with a brilliant flame. It unites directly with hydriodic 
 acid, forming phosphonium iodide, analogous to ammonium 
 iodide formed from ammonia in the same way. 
 
 EXPERIMENT. Hydrogen phosphide may be conveniently pro- 
 pared by the apparatus shown in Fig. 58. The retort is one third 
 filled with moderately concentrated solution of potassium hydroxide, 
 a few pieces of phosphorus are dropped in, and by means' of the tube 
 
 Fig. r>8. Preparation of Hydrogen Phosphide. 
 
 passing through the tubulure, the air is displaced by a current of pure 
 hydrogen. The beak of the retort is prolonged by a glass tube which 
 dips beneath the surface of the water in the porcelain dish, thus cut- 
 ting off contact with the air. On heating the contents of the retort 
 
OXIDES AND ACIDS OF PHOSPHORUS. 205 
 
 to boiling, hydrogen gas first escapes, but soon bubbles of phosphine 
 make their appearance, each one of which as it bursts takes fire spon- 
 taneously owing to a small quantity of the liquid phosphide dis- 
 solved in it and forms a beautiful ring of white smoke which rotates 
 on its circular axis as it ascends. If the air of the room be still, sev- 
 eral of these rings will follow each other to the ceiling. When the 
 experiment is concluded, the hydrogen may be again passed until the 
 gas is no longer spontaneously inflammable. 
 
 OXIDES AND ACIDS OF PHOSPHORUS. 
 
 The normal oxides and acids of phosphorus form a parallel 
 series with those of nitrogen. The known members of the 
 series are the following : 
 
 Oxides. Acids. 
 
 Hypophosphorous oxide P'.,0(?) 
 Phosphorous oxide ~P"'.). A 
 
 C Hypophosphorous acid H(PVQ. 2 H.,) 
 
 Phosphoric oxide PV/), Phosphorous acid H 2 (PVQ S H) 
 
 | Phosphoric acid H 3 (PvQ 4 ) 
 
 t Meta-phosphoric acid H(P V O 3 ) 
 
 PHOSPHORIC OXIDE. Formula P 2 O 5 . Molecular mass 141-72. 
 
 261. Preparation. Phosphoric oxide is always the prod- 
 uct of the rapid combustion of phosphorus in the air or in 
 oxygen. The reaction is synthetic, thus : Q 
 
 P. 4- (Q Y = 
 
 EXPERIMENT. Place a fragment of care- 
 fully dried phosphorus in a small cup on a 
 stand, in the middle of a din ing-plate; ignite 
 it by a hot wire and cover it with a large bell- 
 glass, as shown in Fig. 59. White fumes will 
 fill the jar, gradually aggregate together and 
 
 fall into the plate, resembling in appearance 
 
 Fig. 59. Formation of 
 a miniature snow-storm. Phosphoric Oxide. 
 
 262. Properties. Phosphoric oxide is a snow-white 
 amorphous powder, which is fusible at a red heat and is 
 
20C) IXORGAXIC CHEMISTRY, 
 
 easily volatilized. It rapidly attracts moisture from the air, 
 and adheres together in flocks. When plunged into water 
 it hisses like a hot iron, and then dissolves, forming phos- 
 phoric acid. It is used for drying gases. 
 
 TRI-HYDROGEN PHOSPHATE OR PHOSPHORIC ACID. Formula 
 H 3 PO 4 . Molecular mats 97 '80. 
 
 263. Preparation. Phosphoric acid is obtained by the 
 action of boiling water upon phosphoric oxide : 
 
 P 2 5 + (H,,0) 3 = (H S P0 4 ), 
 
 by the oxidation of phosphorus by nitric acid; or by the 
 decomposition of phosphates by sulphuric acid : 
 
 Pb" 8 (P0 4 ), + (H,(S0 4 )) 3 = (Pb"(S0 4 )) 8 + (H,P0 4 ), 
 
 Lead phosphate. Sulphuric acid. Lead sulphate. Phosphoric arid. 
 
 Commercially, an impure acid is prepared by treating bone- 
 ash calcium phosphate with sulphuric acid. 
 
 264. Properties. As thus prepared, phosphoric acid 
 is a syrupy liquid, which by spontaneous evaporation over 
 sulphuric acid gives hard, transparent, prismatic crystals, 
 which deliquesce in the air. Their solution is intensely acid ; 
 it does not coagulate albumin, nor precipitate barium chlo- 
 ride. It throws down from ammoniacal solutions of magne- 
 sium sulphate a white crystalline precipitate of ammonio- 
 magnesium phosphate, sometimes called triple phosphate. 
 It gives with silver nitrate, when neutralized by ammonia, 
 yellow silver phosphate. On heating its aqueous solution to 
 213, it gives di-phosphoric a.cid ; and on raising the temper- 
 ature to redness, meta-phosphoric acid is produced. 
 
 This form of phosphoric acid, being tribasic, is capable of 
 forming acid, normal, and double salts. The following are 
 examples of each: 
 
 Acid Salts. 
 
 Di-hydro-sodium phosphate H. 2 NaPO 4 
 
 Hydro-di-sodium phosphate HNa. 2 PO 4 
 
 Hydro-calcium phosphate HCa"PO 4 
 
META-PHOSPHORIC ACID. 207 
 
 Normal Sails. 
 
 Potassium phosphate K. 3 PO 4 
 
 Barium phosphate Ba // 3 (PO 4 ) 2 
 
 Bismuth phosphate Bi"'PO 4 
 
 Double Salts. 
 
 Ammonio-magnesium phosphate (NH 4 )Mg"(PO 4 ) 
 Potassio-barium phosphate KBu"(PO 4 ) 
 
 The acid and normal salts are sometimes called primary, 
 secondary, or tertiary salts, according as one, two or three 
 hydrogen atoms are replaced to form them. 
 
 MONO-HYDROGEN PHOSPHATE OR META-PHOSPHORIC ACID. 
 Formula HPO. { . Molecular mass 79 '84. 
 
 2(>5. History and Preparation. In 1833 Graham 
 showed that ordinary phosphoric acid loses water on being 
 heated to redness, and on cooling becomes a transparent ice- 
 like solid, the so-called glacial phosphoric acid : 
 
 H,P0 4 - H,0 = HP0 5 
 
 The same acid is produced by dissolving phosphoric oxide 
 in cold water: pA + H/) = (JJpQ ^ 
 
 Meta-phosphates are produced*by igniting acid phosphates 
 which have two hydrogen atoms : 
 
 H 2 NaPO 4 H 2 O = NaPO s 
 or which have two atoms of volatile base : 
 
 H(NH 4 )NaP0 4 = H(NH 4 )O + NaPO 3 
 
 Hydro-ammonio-Bodium Ammonium hydrate. Sodium meta- 
 phosphate. phosphate. 
 
 By decomposing meta-phosphates, the acid is obtained. 
 
 26G. Properties. Meta-phosphoric acid is a hard, trans- 
 parent, colorless, glassy mass, not crystallizable, and very 
 soluble in water, forming a strongly acid solution, which 
 gradually takes up water and forms tri-hydrogen phosphate. 
 It coagulates albumin and gives a white precipitate with 
 
208 INORGANIC CHEMISTRY. 
 
 silver nitrate. It is mono-basic, and forms but one class of 
 salts. It is distinguished by a remarkable tendency to pro- 
 duce polymeric forms, called di-, tri-, tetra-, and hexa-meta- 
 phosphates, respectively. 
 
 The two phosphoric acids now described are the mono- and 
 di-meta forms of ortho-phosphoric acid, H 5 PO 5 , being only 
 more distinctly marked examples under a general law. Cer- 
 tain ortho-phosphates, as the mineral libethenite, hydro-di- 
 cupric ortho-phosphate HCu",PO 5 , and di-hydro-ammouio- 
 magnesium ortho - phosphate H , (NHj Mg " PC- , are well- 
 known bodies. 
 
 DI-PHOSPHORIC OR PYRO-PHOSPHORIC ACID. Formula 
 H 4 P 2 O.. Molecular mass 177'64. 
 
 2O 7. In 1826 Clark discovered a variety of phosphoric 
 acid intermediate between the two forms already described, 
 produced by heating a solution of the tri-basic acid to 213, 
 and which for this reason he called pyro-phosphoric acid. 
 Two molecules of the tri-hydrogen phosphate together lose 
 one of water: (H p O<)s _. H/) = H^ 
 
 Di-phosphates are produced by igniting a phosphate which 
 has one atom of volatile base : 
 
 (HNa. 2 PO 4 ) 2 - H 2 O = Na 4 P 2 0. 
 
 ' Hydro-di-sodium phosphate. Water. &>diu>n di-phosphate. 
 
 It occurs generally in solution, but may be obtained by 
 evaporation at 213 as a soft glass or in semi-crystalline 
 masses. Its solution is strongly acid, does not coagulate 
 albumin, and precipitates silver nitrate white. Being tetra- 
 basic, di-phosphoric acid forms a large series of acid, normal 
 and double salts. It bears the same relation to tribasic phos- 
 phoric acid that di-sulphuric acid bears to dibasic sulphuric 
 acid. On boiling its solution, it takes up a molecule of 
 water and becomes tri-hydrogen phosphate; on igniting it, 
 it loses one, becoming mono-hydrogen phosphate. 
 
PHOSPHOROUS OXIDE. 209 
 
 268. Aldehydic Phosphoric Acids. Two other acids 
 of pentad phosphorus are known, which, as they resemble 
 the aldehydes of organic chemistry, may be called aldehy- 
 dic acids. These are commonly known as phosphorous and 
 hypo-phosphorous acids. Phosphorous acid has the formula 
 H. 2 (PO 3 H), is dibasic, and forms so-called phosphites. Hypo- 
 phosphorous acid, H(PO 2 H,), is mono-basic, and is obtained 
 by decomposing barium hypo-phosphite with sulphuric acid. 
 Hypo-phosphites are formed by boiling phosphorus in alka- 
 line solutions. 
 
 PHOSPHOROUS OXIDE. Formula P 2 O 3 . Molecular mass 109 '8. 
 
 269. Preparation and Properties. Phosphorous ox- 
 ide is produced by the imperfect combustion of phosphorus 
 in dry air. For this purpose the phosphorus is placed in 
 a somewhat narrow tube (Fig. 60), drawn to a point at one 
 
 ^BB end and at the other 
 
 ^T; ^aF = ^^ :7 >-:-?^Kjtf^^gSBi^-y connected with an 
 
 Fig. GO. Production of Phosphorous Oxide. aspirator, by means 
 
 of which air may be 
 
 drawn through the tube. On heating the tube the phospho- 
 rus takes fire, and a bulky amorphous deposit of phosphorous 
 oxide collects beyond it in the tube. The white flakes are 
 readily volatile and have an alliaceous odor. They are deli- 
 quescent and dissolve in water with a hissing noise, 
 forming an acid solution. The rational constitu- 
 tion of this compound is unknown ; but it can 
 hardly be normal, since it does not give the nor- 
 mal acid by the action of water. 
 
 No acid of triad phosphorus is certainly known. 
 
 270. Hypo-phosphorous Oxide. By cover- 
 ing fragments of phosphorus with a layer of phos- 
 phorous chloride, and exposing the whole to the 
 
 air, Leverrier obtained a canary-yellow substance, soluble 
 m water, and decomposing when boiled, into phosphoric acid 
 
210 INORGANIC CHEMISTRY. 
 
 and a flocculent substance having the composition P 4 O, 
 which could be heated to 300 without change. 
 
 EXPERIMENT. By melting 1 a piece of phosphorus under warm 
 water (Fig. 61), and then passing into it a current of oxygen from a 
 gas-holder, the phosphorus will take fire and burn brilliantly beneatu 
 the water. The phosphoric acid produced dissolves in the liquid; 
 but besides this a red-brown powder is formed, which was formerly 
 regarded as hypophosphorous. oxide, but which is now believed to be 
 only impure red phosphorus. 
 
 3. ARSENIC AND ANTIMONY. 
 
 ARSENIC. Symbol As. Atomic mas* 74'9. Valence III and V. 
 Relative density 149 '8. Molecular mass 299'(>. Molecular, 
 volume 2. The mass of 1 liter of arsenic vapor is 13*44 y ran us 
 (150 critJis). 
 
 271. History. Two sulphides of arsenic occur native, 
 one red, the other yellow. The former is mentioned by Aris- 
 totle under the name ffa^ddpd/.r^ and the latter by Dioscor- 
 ides under the name apffsvtzov, from which the name arsenic 
 is derived. The metal was first obtained by Schroeder in 
 1694, and was more minutely examined by Brandt in 1733. 
 
 272. Occurrence. Arsenic occurs somewhat abundant- 
 ly in nature, both free and combined with other metals, as 
 iron, copper, cobalt, nickel, etc. The most abundant sources 
 of it are the iron arsenides leuco- and arseno-pyrite. The 
 yellow sulphide called orpiment, and the red sulphide, or 
 realgar, also occur native. 
 
 273. Preparation. From mispickel or arsenical pyrites 
 arsenic is obtained by heating it in earthen tubes or retorts. 
 The arsenic, being volatile, sublimes and condenses in the 
 cooler portions of the retort, toward its mouth. In certain 
 districts arsenic is obtained by reducing its oxide with char- 
 coal ; this method gives it in a purer form. 
 
 274. Properties. Arsenic is a dark, steel-gray brittle 
 solid, with a metallic luster and a specific gravity of 5 '6 to 
 
HYDROGEN ARSENIDE. 211 
 
 5*9. It occurs in two, perhaps three, allotropic modifica- 
 tions. Besides the steel-gray variety , which crystallizes in 
 rhombohedrons and has the above specific gravity, there is 
 an amorphous black vitreous variety ft, of specific gravity 
 4*71, which at 360 passes into with considerable evolu- 
 tion of heat. Arsenic is volatile in close vessels at 500; its 
 vapor is orange yellow, and has a peculiar odor resembling 
 garlic. In the air it gradually oxidizes at common tempera- 
 tures, and at a red heat it burns with a bluish-white flame, 
 producing arsenous oxide. Arsenic and all its compounds 
 are active poisons. In the arts it is used in pyrotechny, in 
 the manufacture of shot, and as a fly-powder under the name 
 . of cobalt. 
 
 ARSENIC AND HYDROGEN. 
 
 HYDROGEN ARSENIDE OR ARSINE. Formula H.,As. Molec- 
 ular mass 77 '9. Molecular volume 2. The mass of 1 liter is 
 3-48 grams (39 criths). 
 
 275. History. Hydrogen arsenide was discovered by 
 Scheele in 1755. 
 
 276. Preparation. It is always prepared by the action 
 of pure zinc upon sulphuric or hydrochloric acid containing 
 arsenic, or of these acids in the pure state upon zinc contain- 
 ing arsenic : 
 
 As. 2 Zn :{ + (HC1) (! = (ZnCl. 2 ) 3 -f (H 3 As) 2 
 
 Zinc arsenide. Hydrogen chloride. Zinc chloride. Hydrogen arsonde. 
 
 277. Properties. Arsine is a colorless gas, with an alli- 
 aceous odor and a specific gravity of 2 - 7. Cooled to 40 
 it becomes a liquid, which solidifies at 119, and melts 
 again at 113'5. It is soluble in five times its volume of 
 water. It takes fire easily in the air, burning with a bluish- 
 white flame, evolving white fumes of arsenous oxide. If 
 a cold surface of porcelain be held in this flame, metallic 
 arsenic is deposited upon it as a dark stain or tache. Hy- 
 drogen arsenide is easily decomposed when the tube through 
 
212 
 
 INOlidA M( ' ( 'HEMISTRY. 
 
 which it is passing is heated to redness, a dark mirror-like 
 ring of metallic arsenic being formed just beyond the heated 
 spot. The gas is also decomposed when passed into a solu- 
 tion of silver nitrate, forming arseuous acid and precipitat- 
 ing metallic silver. 
 
 EXPERIMENT. Marsh's test for arsenic depends upon the produc- 
 tion of arsine whenever arsenic is present in any soluble form in a 
 solution in which hydrogen is being evolved. The form of Marsh's 
 apparatus employed by the author is represented in Fig. 62. It con- 
 sists of a three-necked bottle, through the middle tubulure of which 
 a funnel-tube passes for the supply of liquid, while one of the side 
 openings has a siphon tube for withdrawing the exhausted acid, and 
 
 Fig. 62. Marsh's Arsenic Apparatus. 
 
 the other a delivery tube carrying a bulb filled with cotton, to retain 
 impurities mechanically carried over with the gas. Next to this bottle 
 is ajar containing potassium hydroxide arid calcium chloride to purify 
 the gas, which then passes through a long tube of hard glass drawn 
 out at intervals. Pure zinc in fragments is first put into the three- 
 neeked bottle, and then pure sulphuric acid, previously diluted with 
 three parts of water and cooled, is added until this bottle is about one 
 third full. After allowing sufficient time for the air to be expelled 
 from the apparatus, the narrow tube is heated to dull redness by the 
 gas flame. If no dark deposit appears beyond the flame in fifteen 
 minutes, the materials may be considered pure. The liquid suspected 
 
OXIDES AND ACIDS OF ARSENIC. 213 
 
 to contain arsenic which must be perfectly free from all organic 
 matter is now added through the funnel-tube. If arsenic be present, 
 the flame of hydrogen burning at the end of the tube will, often in a 
 few seconds, change color, becoming whitish, and will deposit a dark 
 brown metallic spot on the porcelain crucible cover pressed down 
 upon it. If the tube be again heated, the arsine will be decomposed 
 and the arsenic be deposited as a dark metallic ring. According to 
 Wormley ^^ of a grain of arsenous oxide in one hundred grain 
 measures of the solution may be detected by this test. 
 
 Hydrogen arsenide is one of the most active poisons 
 known. It should therefore be experimented upon with 
 the greatest care. 
 
 OXIDES AND ACIDS OF ARSENIC. 
 
 278. The oxides of arsenic, with their corresponding 
 acids, are the following: 
 
 Oxides. Acids. 
 
 Arsenous oxide As 2 O 3 Arsenous acid HAsO 2 
 
 Arsenic oxide As 2 O 5 Arsenic acid H 3 AsO 4 
 
 ARSENIC OXIDE. Formula As 2 O 5 . Molecular mass 229 '6. 
 
 279. Preparation and Properties. Arsenic oxide, ob- 
 tained by heating arsenic acid to dull redness, is an opaque, 
 white, amorphous, deliquescent mass, which fuses at a bright 
 red heat, and decomposes into arsenous oxide and oxygen. 
 By solution in water it forms arsenic acid. 
 
 ARSENIC ACID. Formula H 3 AsO 4 . Molecular mass 141*74. 
 
 280. Preparation and Properties. Arsenic acid is 
 produced by oxidizing arsenous oxide or acid by nitric acid, 
 and evaporating to a syrup. On standing, long rhomboidal 
 laminae separate, which contain water of crystallization and 
 are deliquescent. At 100 this water is expelled, and needle- 
 shaped crystals of the acid H 3 AsO 4 are produced. Its aque- 
 ous solution is strongly acid. On heating arsenic acid to 
 150, di- or pyro-arsenic acid, H 4 As.,O 7 , results; and at 200, 
 
214 INORGANIC CHEMISTRY. 
 
 another molecule of water is lost and meta - arsenic acid, 
 HAsO 3 , is obtained. Salts corresponding to each of these 
 acids have been produced. Arsenic acid and its salts are 
 poisonous, though less so than arsenous compounds. 
 
 ARSENOUS OXIDE. Formula As.,O a . Molecular mu** 197*68. 
 Molecular volume 1 (anomalous). Relative density 197 '68. 
 
 281. Occurrence and Preparation. Arsenous oxide 
 occurs native as the mineral arsenolite. It is prepared by 
 roasting arsenical ores with free access of air, and collecting 
 the vapors in partitioned chambers. The tine dust thus ob- 
 tained is purified by re-sublimation. 
 
 282. Properties. Arsenous oxide exists in two, prob- 
 ably polymeric, modifications. When condensed at a tem- 
 perature of 400, it forms a transparent vitreous mass , of 
 specific gravity 3'738. When deposited slowly at tempera- 
 tures slightly less elevated, this variety crystallizes in right 
 rhombic prisms. The second modification, ft, is obtained by 
 condensing the vapor at 200, in brilliant transparent octa- 
 hedral crystals, of specific gravity 3 -689. The same octahe- 
 dral form is obtained on cooling a saturated aqueous solu- 
 tion. The vitreous or variety passes gradually at ordinary 
 temperatures, rapidly at 100, into y9, forming a white opaque 
 mass resembling porcelain. When the vitreous variety is dis- 
 solved to saturation in hot hydrochloric acid and left to cool 
 slowly, it crystallizes in octahedrons, the formation of eacli 
 crystal being accompanied with a flash of light. Arsenous 
 oxide volatilizes at 218, yielding a vapor whose density is 
 198 instead of 99. This would indicate that the vitreous 
 modification, which is formed at high temperatures, has the 
 molecular formula As 4 O 6 , double that of the octahedral mod- 
 ification. Both varieties are soluble in water, in hydrochlo- 
 ric acid, and in alkaline solutions. Arsenous oxide is a most 
 energetic poison, one or two decigrams being sufficient to 
 Destroy life. 
 
ANTIMONY. 
 
 215 
 
 EXPERIMENTS. Arsenous oxide may be readily recognized by its 
 weight, by its volatility, and by its crystalline form. If a few milli- 
 grams be placed in a small open tube 
 (Fig. 63) and heated over a gas-flame 
 the upper part of the tube being slightly 
 warmed the oxide will be volatilized 
 and the vapor will condense on the tube 
 in a ring of brilliant octahedral crys- 
 tals like those in Fig. (34. If in another 
 similar tube a mixture of arsenous oxide 
 
 and a little charcoal 
 
 be placed and heat- 
 ed, a dark ring of 
 
 metallic arsiMiic will 
 
 be deposited, as 
 
 shown in the figure. 
 
 No other substance 
 
 but arsenic gives 
 
 these appearances. 
 
 Fig. 64. Crystals of 
 Arseuous oxide. 
 
 Fig. 63. Testing for Arsenic. 
 
 The best antidote for arsenic is freshly prepared ferric or 
 magnesic hydrate. 
 
 ARSENOUS ACID. Formula H 3 AsO. r Molecular mass 125 '78. 
 
 283. Preparation and Properties. When arsenous 
 oxide is dissolved in water, an acid, styptic liquid is ob- 
 tained, which can not be evaporated without decomposition. 
 The arsenites in general are more stable, and include both 
 ortho-arsenites and meta-arsenites. Potassium arsenite is the 
 chief ingredient in Fowler's solution, used in medicine, and 
 copper arsenite in Paris green, used as a pigment. 
 
 ANTIMONY. Symbol Sb. Atomic mass 119 -6. Valence III 
 andV. Relative density 239'2 (?). Molecular mass 478 '4 (?). 
 Molecular volume 2. The mass of 1 liter of antimony-vapor is 
 21-86 grams (240 criths) (?). 
 
 284. History and Occurrence. Antimony was first 
 prepared by Basil Valentine toward the end of the fifteenth 
 
216 INORGANIC CHEMISTRY. 
 
 century. It occurs in nature both free and in combination. 
 The most abundant source of it is the sulphide, known as 
 stibnite ; but it exists in combination with oxygen in the 
 minerals valentinite, senarmontite, and cervantite ; with sil- 
 ver, in dyscrasite ; and with silver and sulphur in pyrargy- 
 rite and miargyrite. 
 
 285. Preparation and Properties. Commercial anti- 
 mony is generally produced by acting upon the melted native 
 sulphide with iron, producing ferrous sulphide and free anti- 
 mony, according to the equation : 
 
 Sb& + Fe 3 = (FeS) 3 + 8b, 
 
 It is also obtained by roasting the sulphide, and then reduc- 
 ing the oxide thus obtained, with charcoal. By fusion with 
 sodium carbonate and a small quantity of antimonous sul- 
 phide, the metal may be obtained pure. 
 
 Antimony is a brilliant bluish-white brittle metal, of spe- 
 cific gravity 6*715. It crystallizes in rhombohedrous, isomor- 
 phous with arsenic and red phosphorus. A curious allotropic 
 variety is obtained by electrolysis, having a specific gravity 
 of 5 '8, and passing into the ordinary condition when heated 
 or struck, with the evolution of great heat. Antimony melts 
 at 450, and at a white heat may be distilled. It tarnishes 
 scarcely at all in the air, but takes fire at a red heat, pro- 
 ducing autimonous oxide. It is strongly attacked by chlo- 
 rine, forming antimonous and antimonic chlorides, SbCl, 
 and SbCL. Antimony is used largely in the arts as a con- 
 stituent of type-metal. 
 
 COMPOUNDS OF ANTIMONY. 
 
 286. Hydrogen An ti moiiide or Stibine, H 3 Sb. 
 
 Whenever an antimony compound is present in a solution 
 from which hydrogen is being evolved, an inodorous gas 
 escapes mixed with the hydrogen, causing it to burn with 
 a bluish-white name. This gas is stibine. It is analogous 
 
OXIDES AM) STLPHWEfi OF ANTIMONY. 'Ill 
 
 to arsine, and is similarly decomposed by heat ; but the me- 
 tallic deposit of antimony is easily distinguished from that 
 of arsenic by its darker color, its smoky appearance, its less 
 volatility, its insolubility in hypochlorites, and its solubility 
 in ammonium sulphide. 
 
 287. Aiitimoiious and Antimoiiic Oxides and Acids. 
 Antimonic oxide, Sb 2 O 5 , is a tasteless, yellowish, insoluble 
 powder, of specific gravity 6 '6, obtained by heating antimo- 
 iric acid. Antimonic acid is obtained by oxidizing anti- 
 mony by nitric acid or by treating antimonic chloride with 
 water. Both the ortho-acid, H 5 SbO 5 , and the di-meta acid, 
 HSbO 3 , have been obtained ; and salts of di-antimonic acid, 
 H 4 Sb 2 O 7 , are also known. 
 
 Antimonous oxide, Sb 2 O ;J) , occurs native, in two different 
 crystalline forms, as senarmontite and valentinite. It is the 
 product of the combustion of antimony in the air, and is 
 then crystalline ; by pouring antimonous chloride into a boil- 
 ing solution of sodium carbonate it is obtained as a dirty- 
 white powder, which becomes yellow when heated. Anti- 
 monous acid, HSbO 2 , is a feeble acid, forming easily de- 
 composable salts. It acts also as a base, SbO or antimonyl 
 
 acting as a radical. Thus tartar-emetic is C 4 H 4 O 2 j Q/g^Q\ 
 potassio-antimonyl tartrate. 
 
 288. Antimonous and Antimonic Sulphides and 
 Sulph-acids. Antimonic sulphide, Sb 2 S 5 , is obtained as 
 a yellowish-red powder by the action of hydrogen sulphide 
 upon a solution of the chloride in tartaric acid, or by acidi- 
 fying a solution of an alkaline sulph-antimonate. It unites 
 readily with sulphides of positive elements, forming sulph- 
 antimonates, having the general formula M 3 SbS 4 ; of which 
 sodium sulph-antimonate, Na,SbS 4 , 9 aq. sometimes called 
 Schlippe's salt is an example. 
 
 Antimonous sulphide, Sb 2 S 3 , exists native as s.tibnite, as 
 above stated. It has a steel-gray color, a specific gravity 
 
218 ryoRGAyir CHEMISTRY. 
 
 of 4*5, and a strong metallic luster. It crystallizes in ortho- 
 rhombic prisms. It is thrown down by hydrogen sulphide 
 from antimonous solutions as a bright orange-red precipitate, 
 which contains water. On fusion it becomes steel-gray. The 
 sulph-antimonites, which it forms by union with positive sul- 
 phides, are largely represented among minerals : pyrargyrite 
 Ag' 3 SbS 3 , and boulangerite Pb" 3 (SbS 3 ) 2 , being ortho-sulph- 
 antimonites ; miargyrite Ag'SbS 2 , and berthierite Fe"(SbS 2 ) 2 
 being meta-sulph-antimonites ; and jamesonite Pb" 2 Sb 2 S 5 , and 
 brongniardite (PbAg)" 2 Sb. 2 S 5 being di- or para-sulph-antimo- 
 nites. 
 
 4. BISMUTH. 
 
 Symbol Bi. Atomic maw 207 '3. Valence III ami V . Specific 
 gravity of solid 9'83. Fuse* at 264. 
 
 289. History. Bismuth was first distinctly recognized 
 by Basil Valentine in the fifteenth century. Agricola, in 
 1529, calls it Bisemutum, and Paracelsus mentions it as 
 Wisemat. It was for a long time confounded with other 
 metals, especially with lead, tin, and antimony. Pott, in 
 1739, first described its characteristic reactions. 
 
 290. Occurrence and Preparation. Bismuth occurs 
 in the metallic state in veins traversing gneiss, clay-slate, 
 and other crystalline rocks, principally in Saxony and Bohe- 
 mia. It occurs also as oxide, forming the mineral bismite ; 
 as sulphide, or bismuthinite ; as sulpho-telluride, or tetrady- 
 mite ; and as carbonate, or bismutite. It is prepared on the 
 large scale in the arts from the native bismuth by placing 
 this, mixed with the rocky gangue, in iron tubes, slightly 
 inclined, which are heated in a furnace. The bismuth melts 
 and flows out at the lower ends of the tubes into suitable 
 vessels, from which it is ladled into moulds. The bismuth 
 of commerce contains arsenic, iron, and other metals, from 
 which it may be freed by fusion with potassium nitrate, by 
 
PROPKRT/ES OF lifSUt'TH. 210 
 
 which these metals are oxidized. Chemically pure bismuth 
 may be obtained by reducing the basic nitrate by charcoal. 
 
 291. Properties. Bismuth is a hard, brittle, brilliant 
 reddish-white metal. It is powerfully dia-niagnetic, and has 
 a strong tendency to crystallize when cooled from fusion ; 
 by melting a considerable quantity of it, allowing it to cool 
 until a crust forms on the surface, piercing this and pour- 
 ing out the metal which still remains fluid, crystals of great 
 size and beauty may be obtained. They are rhombohedrons, 
 though on account of the large interfacial angle, 87 40', 
 they have often been mistaken for cubes, in which this angle 
 is 90. Owing to a slight superficial oxidation, these crys- 
 tals, as usually obtained, are beautifully iridescent. Bismuth 
 has a specific gravity of 9*83 ; it melts at 264, and expands 
 one thirty-second of its bulk on solidifying. It may be dis- 
 tilled at a white heat. It is unaltered in dry air, but is tar- 
 nished in presence of moisture. Strongly heated, it takes 
 fire, burning with a bluish-white flame, and forming bismu- 
 thous oxide. Chlorine and nitric acid attack it readily, but 
 hydrochloric and sulphuric acids, when cold, have no action 
 upon it. 
 
 Bismuth is used in the arts for forming alloys. Hose's 
 fusible metal is composed of one part of lead, one of tin, and 
 two of bismuth; it melts at 94. Lippwitz's fusible metal 
 contains three parts of cadmium, four of tin, eight of lead, 
 and fifteen of bismuth; it melts at 60. An alloy of lead 
 and bismuth is used in the so-called permanent metallic 
 pencils. 
 
 COMPOUNDS OF BISMUTH. 
 
 292. Bismuthous Chloride, BiCl 3 . This chloride may 
 be formed by the direct action of chlorine upon bismuth. 
 It is a white, granular, deliquescent substance, fusible at 
 230 and volatile at 435. By contact with water it is de- 
 composed, forming bismuthyl chloride, (BiO)Cl, sometimes 
 called bismuth oxychloride. 
 
220 lyORG.lXIC CHEMISTRY. 
 
 293. Bismuthic Oxide, Bi.,O 5 . Bismuthic oxide is ob- 
 tained by heating its hydrate to 130. It is a brown powder, 
 which gives up a part of its oxygen readily. Its hydrate, 
 called bismuthic acid, HBiO 3 , may be prepared by oxidiz- 
 ing bismuthous hydrate, suspended in water, by a current 
 of chlorine. It is a bright red powder, which loses oxygen 
 a little above 100. Its salts are called bismuthates ; po- 
 tassium bismuthate, KBiO,, and bismuthous bismuthate, 
 Bi'"Bi v O 4 , are examples. 
 
 294. Bismuthous Oxide, Bi 2 O,. This oxide occurs 
 native as bismite. It may be formed by burning the metal 
 in air, or by igniting the hydrate, carbonate, or nitrate. It 
 is a pale-yellow powder, of specific gravity 8 '2, which melts 
 at a red heat, and is insoluble in water. It has been ob- 
 tained in ortho - rhombic prisms. Bismuthous hydrate, 
 H 3 BiO,, is obtained by treating a bismuthous salt, as the 
 chloride, for example, with potassium hydrate. A white, 
 flocculent precipitate is thrown down, which on drying loses 
 water and becomes an amorphous white powder, HBiO. r 
 With strong bases this body acts like an acid, sodium bis- 
 muthite, NaBiO. 2 , being one of its salts. But with strong 
 acids, on the other hand, this hydrate is strongly basic, the 
 nitrate, Bi(NO 3 ) 3 , the sulphate, Bi,(SO 4 ) 3 , the carbonate, 
 Bi. 2 (CO 3 ) 3 , and the phosphate, BiPO 4 , being well-known 
 compounds. By pouring the nitrate into a large quantity 
 of water, the mono -meta-nitrate, BiNO 4 , is produced. 
 
 Bismuthous sulphide, Bi 2 S 3 , occurs native as bismuthiu- 
 ite. It is obtained as a black precipitate, on adding hydro- 
 gen sulphide to solutions of bismuth ; but, unlike the sul- 
 phides of arsenic and antimony, it is not soluble in solutions 
 of the alkali sulphides. It forms with metallic sulphides 
 salts called sulpho-bisrnuthites, some of which, as that of 
 lead or kobellite, Pb" 3 (BiS 3 ) 2 , and those of copper, called 
 emplectite, Cu"(BiS 2 ) 2 , and wittichenite, Cu" 3 (BiS 3 ) 2 , occur 
 native. 
 
RELATIONS OF THE \LTff (tfi A'.V C.ROrr. 221 
 
 5. RELATIONS OF THE NITROGEN GROUP. 
 
 295. The members of the nitrogen group have close 
 relations, both physically and chemically, with each other. 
 From nitrogen to bismuth they increase in density and in 
 atomic mass, while their chemical activity decreases in the 
 same order. The last four are iso-dimorphous ; that is, they 
 all have two crystal-forms, which are the same for each sub- 
 stance. A comparison of their compounds will show how 
 closely they are allied chemically : 
 
 TRIAD COMPOUNDS. 
 
 Hydrides. Chlorides. Oxides. Sulphides. 
 
 N H,N NC1 3 NA 
 
 P H 3 P PC1 3 PA P 2 S 3 
 
 As H 3 As AsCl 3 As 2 O 3 As 2 S 3 
 
 Sb K 5 Sb SbCl 3 SbA Sb 2 S ;! 
 
 Bi BiCl 3 BiA Bi 2 S 3 
 
 PENTAD COMPOUNDS. 
 
 Chlorides. Oxides. Sulphides. 
 
 N N.A 
 
 p PCI, PA PA 
 
 As AsCl 5 As 2 O 5 As 2 S 5 
 
 Sb SbCl 5 Sb 2 O 5 Sb 2 S 5 
 
 Bi Bi 2 5 
 
222 
 
 EXERCISES. 
 
 ! 
 
 1. In what ways may nitrogen be prepared? 
 
 2. The mass of a given volume of oxygen is thirty grams ; what 
 is the mass of the same volume of nitrogen ? 
 
 3. What mass of oxygen does a cubic meter of air contain ? 
 
 4. What are the proofs that air is merely a mixture? 
 
 5. What volume of air is required to yield six kilograms of oxygon ? 
 
 6. At what temperature has air the density of H at 0? 
 
 7. What mass of nitrogen does ten grams of ammonia contain? 
 
 8. A liter of water is to be saturated with ammonia- gas at 0; how 
 many grams of (NHJC1 and of CaO must be used in the process? 
 
 9. What volume of H 3 N at 15 will a kilogram of NH 4 C1 yield? 
 
 10. 250 cubic centimeters ammonia decomposed by el '(trie sparks 
 gives what volume of mixed gases? If 200 cubic centimeters of oxy- 
 gen be added and exploded, what will be the composition of the 
 remaining gas? 
 
 11. What volume of NH :i will neutralize a liter of HC1? 
 
 12. How much nitric acid may be obtained from a kilogram KNO., 
 by the laboratory process? How much by the commercial ? 
 
 13. To neutralize ten grams MgO requires how many cubic centi- 
 meters of nitric acid of specific gravity 142? (Acid contains 70 per 
 cent of HNO 3 ,) 
 
 14. Write the graphic formula of nitrogen tetr-oxide? 
 
 15. A kilogram of copper gives what volume of N 2 O 2 ? 
 
 16. One liter of N 2 O 2 requires what volume of oxygen to make 
 
 NA? 
 
 17. How many cubic centimeters of O and of N in one liter of 
 nitrogen di-oxide? 
 
 18. Fifteen grams ammonium nitrate yield what volume of N 2 O? 
 
 19. What volume of H will one gram of K 2 O burn? One liter? 
 
 20. One cubic centimeter of liquefied N 2 O requires what mass of 
 (NH 4 )NO a ? 
 
 2. 
 
 21. Give the chemical stages in making phosphorus. 
 
 22. One hundred kilograms of bone-ash, 80 per cent calcium phos- 
 phate, yield how many kilograms of phosphorus? 
 
EXERCISES. 223 
 
 23. How do common and allotropic phosphorus differ? 
 
 24. One liter of phosphine contains what volume of P vapor? 
 
 25. What volume of air is required to burn ten grams of P? 
 
 26. If dissolved in boiling water, how much phosphoric acid would 
 the above product yield ? 
 
 3. 
 
 27. Give the preparation and properties of metallic arsenic. 
 
 28. Describe Marsh's test. What is the limit of its delicacy? 
 
 29. At a certain temperature the mass of 100 liters of hydrogen is 
 four grams ; what will be the mass of this volume of As vapor at the 
 same temperature ? 
 
 30. H 3 As contains \vhat volume of H ? How much air is required 
 to burn it ? 
 
 31. Calculate the percentage of antimony in antimonous sulphide. 
 
 32. How is stibine distinguished from arsine? 
 
 33. Give the formulas of the common antimony compounds. 
 
224 ixona t i \K ' ( -it KM is 77,' r. 
 
 CHAPTER FIFTH. 
 
 NEGATIVE TETRADS. 
 
 1. CARBON. 
 
 Symbol C. Atomic, ma.s,s 11 '97. Valence II and IV. Relative 
 density 12 (?). Molecular maw 23'94 (?). Molecular rol- 
 tnne 2. The mass of 1 liter of carbon-vapor i 1*075 gram* 
 (12 mtfi,s) (?). 
 
 296. Occurrence. Carbon occurs native in two allo- 
 tropic forms, known as the diamond and as graphite. Also 
 more or less impure, in the various forms of mineral coal. 
 Combined with hydrogen, it occurs in bitumen and petro- 
 leum ; with oxygen, it exists in the air ; and with oxygen 
 and calcium it forms limestone, a very abundant rock, of 
 which twelve per cent is carbon. It is an essential constit- 
 uent too of all animal and vegetable tissues. 
 
 297. Properties. I. As DIAMOND. The form of carbon 
 known as the diamond is a brilliant, transparent, and gen- 
 erally colorless solid, having a specific gravity of 3 *5, and 
 crystallizing in forms belonging to the isometric system (Fig. 
 65), the faces being often rounded. It does not conduct heat 
 or electricity, and has a very high refractive and dispersive 
 power. It is the hardest form of matter known. Heated to 
 a high temperature, it is converted into a black mass resem- 
 bling graphite. Lavoisier established its composition in 
 1776 by burning it in oxygen. 
 
 The diamond occurs generally in the form of small rounded 
 pebbles in alluvial detritus produced by the disintegration 
 of ancient rocks, from which it is obtained by washing. The 
 
DIAMOND AND GRAPHITE. 
 
 chief localities are India, Borneo, South Africa, and Brazil ; 
 though a few diamonds have been found in Georgia and 
 North Carolina in this country. It is cut for a gem into 
 
 Fig. 65. Crystalline forms of Diamond. 
 
 forms having a relation to its directions of cleavage known 
 as the brilliant, the rose, and the table by means of dia- 
 mond dust. 
 
 II. As GRAPHITE. The second form of carbon, known 
 as graphite, is a friable, leaden-gray solid, unctuous to the 
 touch, of specific gravity 2 to 2*2, and crys- 
 tallizes in hexagonal plates (Fig. 66). It 
 has a semi -metallic luster, conducts heat 
 and electricity readily, and is combustible 
 with difficulty, leaving generally a few per 
 cents of ash. It is soluble in melted iron, 
 from which it crystallizes on cooling. Ni- 
 tric acid mixed with potassium chlorate, 
 when heated, oxidizes graphite to graph- 
 itic acid. 
 
 Graphite occurs both foliated and massive, in metamor- 
 phic rocks, in England, Siberia, and Ceylon, and in various 
 localities in the United States; as Sturbridge, Mass., Ticon- 
 deroga, N. Y., Brandon, Yt., Wake, N. C., etc. It is puri- 
 fied by Brodie's process, by treating it .with potassium chlo- 
 rate and nitric acid ; and is, after drying, condensed to a 
 solid block by hydrostatic pressure. It is largely used for 
 making pencils the name graphite coming from 7y>f>, I 
 write and also for crucibles. 
 
 Fig. 66. Form of 
 Graphite Crystal. 
 
226 INORGANIC CHEMISTET. 
 
 III. As MINERAL COAL. The purest variety of carbcm in 
 the form of mineral coal is that known as anthracite. It is 
 an amorphous, hard, lustrous, black solid, difficultly combus- 
 tible, and consisting of from 80 to 94 per cent carbon. Its 
 specific gravity varies from 1*3 to 1*7. From this there is 
 a regular gradation through cannel and bituminous coals 
 of all varieties^to lignite or brown coal, which in some cases 
 is scarcely altered wood. All coal is derived from primitive 
 vegetation, changed and consolidated by heat and pressure. 
 Anthracite coals are found where the strata have been most 
 heated or disturbed, bituminous where they remain nearly or 
 quite horizontal ; while brown coal or lignite is more recent 
 in age, being generally tertiary. 
 
 Other varieties of more or less pure carbon are : gas- 
 carbon or plumbagine, deposited in the cast-iron retorts in 
 which coal-gas is made ; a hard, compact, mammillated va- 
 riety, being almost metallic in appearance, and conducting 
 both heat and electricity. Specific gravity 1'76. Vegeta- 
 ble coal or charcoal, prepared on the large scale by burning 
 wood in heaps, as shown in Fig. G7, and for special purposes, 
 
 Fig. 67. Interior of Charcoal Heap. 
 
 in iron cylinders ; a bluish-black, porous substance, retaining 
 minutely the form of the original wood, and having a spe- 
 cific gravity of 1*7. Animal coal or bone-black, obtained 
 by igniting bones in close vessels; also a black porous mass, 
 
ABSOEPTIOX BY CHARCOAL. 
 
 227 
 
 containing 90 per cent of calcium phosphate. And lamp- 
 black, or soot, prepared by collecting the matters condensed 
 from the smoke of highly carbonized bodies, such as pitch 
 and tar, in stone chambers ; a soft, finely divided, and very 
 impure form of carbon, used in printing-ink and as a pig- 
 ment. It always contains more or less hydrogen. 
 
 In all its forms, carbon is infusible and non-volatile. As 
 vegetable and animal coal, owing to its very great porosity 
 a single cubic centimeter of box- wood charcoal exposing a 
 surface of more than four square meters carbon exhibits a 
 remarkable power of absorbing gases. Thus, box-wood char- 
 coal will absorb 90 volumes of ammonia gas, and that made 
 from the shell of the cocoanut, 171 volumes. From this fact 
 i. e. , that charcoal carries within it a condensed mass of 
 the oxygen of the air in which it cooled it acts as an ener- 
 getic disinfectant by oxidizing foul vapors. For the same 
 reason animal charcoal is largely used as a decolorizing agent, 
 particularly in refining sugar. It has been proposed for fill- 
 ing respirators, which are placed over 
 the mouth to absorb noxious gases. 
 
 Charcoal filters are 
 
 also in use. 
 
 EXPERIMENTS. The 
 powerful absorption of 
 ammonia gas by char- 
 coal may be shown by 
 filling a cylinder over 
 mercury with the dry 
 gas (Fig. 68), and then 
 introducing into it a 
 piece of cocoanut char- 
 coal, previously heated 
 to redness in sand, and 
 
 allowed to cool away from the air. The ammonia will be rapidly 
 absorbed by the charcoal, and the mercury will rise in the tube. 
 
 To show the decolorizing property of charcoal, place in four na.sk.s 
 dilute solutions of indigo, cochineal, iodide of starch, and potassium 
 
 Fig. 68. Absorp- 
 tion of Gases by 
 Charcoal. 
 
 Fig. 69. Decolorizing power 
 of Charcoal. 
 
228 INORGANIC CHEMISTRY. 
 
 permanganate. Agitate each solution with recently ignited bone- 
 black, and throw each upon a separate filter (Fig. 69). The liquors 
 as they run from the funnels will be colorless. If beer or ale be thus 
 treated, it will lose not only its color, but also its bitter taste. 
 
 Carbon is apparently unalterable in the air at ordinary 
 temperatures. Charred piles driven by the Britons to pre- 
 vent Julius Csesar from crossing the Thames, and wheat 
 charred nearly 2,000 years ago at Herculaneuni, are yet 
 unchanged. When heated in the air, it burns, forming the 
 di-oxide. Heated with sulphur, or used to give the electric 
 arc in hydrogen, it unites directly with these substances, 
 forming carbon disulphide and acetylene. 
 
 CARBON AND HYDROGEN. 
 
 298. Hydrocarbons. The compounds of carbon and 
 hydrogen called hydrocarbons are very numerous, and 
 are usually classified in series. Most of them are more sat- 
 isfactorily considered in Organic Chemistry. Only three of 
 them will therefore be described here. These are hydrogen 
 carbide, H 4 C, hydrogen di-carbide, H t C 2 , and di- hydrogen 
 di-carbide H. 2 C 2 . 
 
 HYDROGEN CARBIDE, OR METHANE. Formula H 4 C. Molec- 
 ular mass 15 '97. Molecular volume 2. Relative density 8. 
 The mass of one liter is 0*716 
 grams (8 criths). 
 
 299. Occurrence. Meth- 
 ane occurs free in nature, being 
 produced somewhat abundantly 
 by the decomposition of vegeta- 
 ble matter confined under wa- 
 ter. It constitutes 75 per cent 
 of the gas which rises when the 
 
 bottom of a pond covered with Fi e- 70 collection of Marsh -gas. 
 vegetable matter is stirred with a stick, whence it is often 
 called marsh-gas. It often escapes from seams in coal mines, 
 
PREPARATION OF METHANE. 
 
 229 
 
 and constitutes the fire-damp of miners. It often occurs 
 largely in the vicinity of salt-wells, as in Kanawha, West 
 Virginia. It constitutes nearly the whole of the so-called 
 natural gas which has come so extensively into use in some 
 of the western cities for purposes of heating and lighting. 
 
 3OO. Preparation. Marsh-gas may be obtained by fill- 
 ing a bottle with \vater, attaching a funnel to its mouth by 
 a string, as shown in Fig. 70, and inverting it in a pond so 
 as to catch the bubbles which rise on stirring the mud at the 
 bottom. By agitating it with a little lime-water, it may be 
 purified for experiment. 
 
 Methane may be also procured by heating potassium ace- 
 tate in presence of a strong base, usually potassium or sodium 
 hydroxide. The reaction which takes place is as follows : 
 
 CH 3 Na 
 
 Sodium acetate. Sodium hydroxide. Sodium carbonate. Methane. 
 
 EXPERIMENT. For the preparation of methane, two parts crys- 
 tallized sodium acetate, two parts sodium hydroxide, and three parts 
 
 Fig. 71. Preparation of Hydrogen carbide. 
 
 powdered quick-lime are intimately mixed together and heated in 
 a thin copper or iron flask to bright redness (Fig. 71). The lime is 
 
 16 
 
230 
 
 INORGANIC CHEMISTRY. 
 
 used to prevent the fusion of the mass. The gas is rapidly evolved, 
 and may be collected over water. 
 
 3O1. Properties. Hydrogen carbide is a colorless, odor- 
 less, and tasteless gas, and is but slightly soluble in water. 
 Its critical temperature is 81 '8 and critical pressure 54'9 
 atmospheres. Reducing the pressure to one atmosphere, the 
 temperature of the liquid sinks to 164, which is therefore 
 its boiling point. At this temperature the liquid methane 
 has a density of 0*415. It is the lightest gas next to hy- 
 drogen, its specific gravity being 0'5576. It is combustible, 
 burning in the air with a pale, faintly luminous flame. By 
 passing electric sparks through the gas, it is decomposed, 
 and yields twice its volume of hydrogen. It forms an ex- 
 plosive mixture with two volumes of oxygen or ten volumes 
 of air, and is the cause of the serious coal-mine explosions 
 which sometimes happen in coal districts. By the action of 
 chlorine, its hydrogen is gradually replaced by this element, 
 forming successively the compounds CH :i Cl, CH,CLj, CHCl.^, 
 and CC1 4 . 
 
 Methane constitutes the first member of a homologous 
 series of hydrocarbons known as the marsh-gas series, the 
 successive members increasing uniformly 
 by CH.,. They are all saturated substances, 
 having the general formula C n H 2n+2 ; i. e., 
 they contain twice as many atoms of hy- 
 drogen as of carbon, plus two. They con- 
 stitute the essential portion of the various 
 native petroleums. The second member of 
 the series is ethane, C 2 H , or H ;J C CH,. 
 
 EXPERIMENT. The levity and inflammabil- 
 
 Fig. 72. Combustibility ity of this gas may be shown, as in the case of 
 of Marsh-gas. J . J . ' 
 
 hydrogen, by introducing a lighted taper into a 
 
 jar of it, held mouth downward. The gas will burn at the mouth 
 of the jar, and the candle-flame, as it passes up into it, will be extin- 
 guished. 
 
PREPARATION AM) PROPERTIES OF ETRYLEXE. 231 
 
 HYDROGEN DI-CARBIDE OR ETHYLENE. Formula H 4 C 2 , or 
 H 2 C = CH 2 . Molecular mass 27*94. Molecular volume 2. 
 Relative density 13 '97. The mass of one liter is 1'25 grams 
 (14 criths). 
 
 302. History. Ethylene was discovered ID 1796 by four 
 Dutch chemists, Deiman, Paets van Troostwyk, Bondt, 
 and Lauwerenburgh. It has been found in small quantity 
 among the gases of coal-mines. 
 
 303. Preparation. It is usually prepared by the action 
 of sulphuric acid upon alcohol, according to the reaction : 
 
 C 2 H 6 = HA + H 2 
 
 This equation exhibits only the final result ; the chemical 
 change itself is evidently more complicated. 
 
 EXPERIMENTS. To prepare etbylene, one volume of alcohol and 
 four volumes of sulphuric acid are mixed in a flask with sand to a 
 thick paste, and gently heated. The sand is added to prevent froth- 
 ing toward the end. The gas may be purified by passing it through 
 milk of lime to remove sulphurous oxide, and through strong sul- 
 phuric acid to retain the vapors of ether and alcohol. 
 
 Mitscherlich's continuous process consists in passing the vapor of 
 80 per cent alcohol through boiling dilute sulphuric acid three parts 
 of water to ten of acid. 
 
 304. Properties. Hydrogen di-carbide is a colorless, 
 irrespirable gas, having usually an ethereal odor. Its spe- 
 cific gravity is 0'978. The critical temperature of ethylene 
 is 10*1, and its critical pressure 51 atmospheres. Under 
 760 millimeters pressure its temperature is 103, which 
 is therefore its boiling point. At 9 '8 millimeters pressure 
 its evaporation produces a temperature of 150'4. Hence 
 liquid ethylene is much used to produce cold in the liquefac- 
 tion of gases. It is soluble in about eight times its volume 
 of water. It is readily combustible, burning in the air with 
 a brilliant white flame, evolving much smoke. Mixed with 
 three volumes of oxygen, it explodes violently on the approach 
 of a flame. It is decomposed by the electric spark, the carbon 
 
232 INORGANIC CHEMISTRY. 
 
 being deposited, and twice its volume of hydrogen remaining. 
 It is an unsaturated substance, and unites directly with an 
 equal volume of chlorine, forming an oily liquid, ethylene 
 chloride, C. 2 H 4 C1 2 . From this fact the gas 
 received from its discoverers the name 
 " olefiant gas," and the liquid was called 
 the " oil of the Dutch chemists." 
 
 EXPERIMENT. To show the direct union of 
 ethylene and chlorine, fill a glass cylinder half 
 full of chlorine over the water-cistern, and then 
 add rapidly an equal volume of olefiant gas. The 
 gaseous mixture will at once begin to diminish 
 in volume (Fig. 73), oily drops will collect upon 
 Fig. 73. Formation of the walls of the vessel, and, sinking through the 
 [de< liquid, form a layer upon the bottom of the con- 
 taining cistern. By pouring off the water and agitating with sodium 
 carbonate solution, the ethylene chloride may be purified and its agree- 
 able, chloroform-like odor obtained. 
 
 Dl-HYDROGEN Dl-CARBIDE OR ACETYLENE. Formula H 2 C 2 
 
 or HC-ECH. Molecular mass 25 '94. Molecular volume 2. 
 Relative density 12*97. The mass of one liter is 1*16 grams 
 (13 criths). 
 
 305. History and Preparation. Acetylene was dis- 
 covered by E. Davy in 1836, and studied by Berthelot in 
 1860. It may be prepared by the direct union of its constit- 
 uents. When the carbon points terminating the electrodes 
 of a powerful voltaic battery or dynamo-machine are brought 
 together in an atmosphere of hydrogen, the carbon and hy- 
 drogen combine at the elevated temperature produced and 
 form acetylene. It is also a product of the action of heat 
 upon substances rich in carbon and hydrogen, and is always 
 formed in the imperfect combustion of hydrocarbon com- 
 pounds, such as coal-gas. 
 
 306. Properties. Acetylene is a colorless gas, having 
 a peculiar and disagreeable odor, and is condensable to a 
 
JL L I 'MIXA TL\(i (',.( X. 233 
 
 liquid under a pressure of 68 atmospheres at 37, its critical 
 temperature. It has a specific gravity of 0'92, is quite solu- 
 ble in water, and burns with a bright but very smoky flame. 
 It is readily absorbed by ammoniacal cuprous chloride, form- 
 ing a red precipitate of cuprous acetylide, which is explosive. 
 This explosive body is sometimes formed in brass gas-pipes 
 by the action upon them of the acetylene in coal-gas, and 
 has been the cause of fatal accidents. It unites directly with 
 the halogens, the compounds of chlorine with it, for example, 
 being C 2 H,C1 2 and C 2 H 2 Cl r 
 
 ILLUMINATING GAS. 
 
 307. History. The production of a combustible gas 
 from coal was first observed by Clayton in 1664 ; but it was 
 not until 1792 that Murdock made gas-illumination a prac- 
 tical success. In 1798 he lighted in this way Boulton and 
 Watt's works at Soho, near Birmingham. The streets of Lon- 
 don were first lighted with gas in 1812. Gas was introduced 
 into Paris in 1815. 
 
 308. Preparation. Illuminating gas is ordinarily pre- 
 pared by distilling bituminous coal at a high temperature ; 
 although various other substances, such as oil, rosin, wood, 
 and petroleum have also been employed for its preparation. 
 The complete apparatus for the manufacture, purification, 
 and collection of coal-gas is represented in Fig. 74. The coal 
 is placed in semi-cylindrical iron retorts, C, set in a furnace 
 shown upon the right, their mouths being closed by heavy 
 plates. Usually five retorts are heated by the same fire, 
 forming what is technically called a "bench." The products 
 of the distillation pass from the retorts through a tube near 
 its mouth, up into a larger horizontal tube, B, called the 
 hydraulic main, where the tar and a portion of the water 
 are condensed to liquids ; the gas then passes on, first through 
 a series of vertical pipes, D, and then through the coke-box 
 or "scrubber" O, by which it is still further cooled and the 
 
234 
 
 IXOL'GA XK' CHEMISTST. 
 
COMPOSITION OF COAL-GAS. 235 
 
 condensable vapors separated. It then enters the purifier, 
 M, a large metallic box containing, on shelves for the pur- 
 pose, either dry slaked lime or, what is preferable, ferric hy- 
 drate, either alone or mixed with lime and sawdust. From 
 this it issues, freed from most of its impurities, particularly 
 sulphur compounds and carbon di-oxide, and is collected in 
 the adjoining gasometer, G, for distribution. 
 
 EXPERIMENT. The manufacture of coal-gas may be illustrated on 
 the lecture-table by the apparatus shown in Fig. 75. The coal is placed 
 in the retort upon the right, which is then, heated by the gas-burner. 
 The water and volatile liquid products condense in the receiver, while 
 the gas passes on to the first U-tube, in one limb of which a piece of 
 red litmus-paper is placed to detect ammonia and in the other a 
 
 Fig. 75. Distillation of Coal. 
 
 a strip of paper moistened with a solution of lead acetate to detect 
 hydrogen sulphide and then to the second, the bend of which con- 
 tains lime-water which indicates, by becoming milky, the presence 
 of carbon di-oxide and is finally collected over water in the capped 
 receiver. By depressing this receiver in the water, and opening the 
 cock, the gas may be lighted as it issues from the jet. 
 
 3O9. Composition and Properties. Coal-gas is a mix- 
 ture of several gaseous products which vary according to the 
 quality of coal used, the temperature at which it is distilled, 
 etc., but which consist essentially of hydrogen and methane 
 (marsh -gas) mixed with variable proportions of ethylene, 
 acetylene, carbon monoxide and di-oxide, butylene, nitro- 
 gen, oxygen, and hydrogen sulphide. The amount of gas 
 obtained varies, with different coals, from 8,000 to 15,000 
 cubic feet to the ton. Coal-gas has a specific gravity vary- 
 
236 INORGANIC CHEMISTRY. 
 
 ing from 0*65 to 0*34. The illuminating power of a gas is 
 determined by an instrument called a photometer, in which 
 the amount of light given by the gas, burning from a jet at 
 the rate of five cubic feet per hour, is compared with that 
 emitted by a standard candle burning 120 grains of sperma- 
 ceti in the same time. A gas may rise in illuminating power 
 to 25 or 30 candles ; but the average supplied in our cities 
 is 16 candles. By heating the gas before it is burned, Sie- 
 mens showed that five feet of gas may be made to give a light 
 of 40 to 50 candles. 
 
 The collateral products of the coal-gas manufacture are in 
 general, two ; the ammoniacal liquors and the gas-tar. The 
 former consists of the condensed water, holding in solution 
 the ammonia produced from the nitrogenous matters in the 
 coal ; the latter is a complex substance, containing in its 
 lighter portions certain volatile liquids as benzene and tolu- 
 ene, and certain volatile alkaline bases as aniline and chiuo- 
 line ; and in its heavier, certain phenols as phenol proper 
 (carbolic acid) and cresol, and certain solid hydrocarbons as 
 naphthalene and anthracene. 
 
 CARBON AND OXYGEN. 
 
 CARBON DI-OXIDE. Formula CO 2 . Molecular mass 43 -89. 
 Molecular volume 2. Relative density 21 '94. The mass of 
 one liter is 1*977 grams (22 criths). 
 
 31O. History. Carbon di-oxide was the first gas distin- 
 guished from air. It w r as noticed as a distinct substance by 
 Paracelsus in 1520 ; and soon after Van Helmont obtained 
 it from limestone whence he called it chalky air and no- 
 ticed its production in the fermentation of sugar and in the 
 burning of charcoal, and its occurrence naturally. Black 
 showed in 1757 that alkalies absorbed it and that its com- 
 pounds effervesced with acids. Lavoisier in 1775 deter- 
 mined its composition synthetically by burning carbon in 
 oxygen. 
 
PREPARATION OF CARBON I) I- OXIDE. 237 
 
 311. Occurrence. Carbon di-oxide exists in the air to 
 the extent of about O04 per cent, being produced by com- 
 bustion, fermentation, respiration, etc. In volcanic districts 
 it is more abundant, the large quantity of it often collected in 
 low places frequently proving fatal to life. Combined with 
 calcium oxide or lime, it exists in enormous quantity in lime- 
 stone. 
 
 312. Preparation. Carbon di-oxide may be prepared 
 by direct synthesis. It is always the product of the com- 
 bustion of carbon in air or in oxygen : 
 
 C + O 2 = CO, 
 
 It is generally obtained, however, by the action of an acid 
 upon some carbonate, as that of sodium or of calcium : 
 
 CaC0 8 + (HN0 3 ) 2 = Ca"(N0 8 ), + H 2 O + CO 2 
 
 It is produced in large quantities in burning limestone for 
 the production of quicklime : 
 
 CaCO 3 = CaO + CO 2 
 
 EXPERIMENTS. All carbonates effervesce with acids from the set- 
 ting free of carbon di-oxide gas. If some fragments of marble be 
 placed in the test-glass (Fig. 76), and some hydrochlo- 
 ric acid be added, a brisk effervescence will take place 
 from the escape of this gas. In order to collect it the 
 experiment may be repeated in the two-necked bottle 
 (Fig. 77), the acid being poured in through the funnel 
 tube upon the marble, previously covered with, water. 
 The gas may be collected over water or by displace- 
 ment, as it is denser than air. Fig ?6 Efferveg . 
 
 313. Properties. Carbon di-oxide is a col- Senates w&h 
 orless gas with a slightly pungent odor and acid 
 
 taste. It is denser than air, its specific gravity being 1 '524. 
 At the ordinary temperature and pressure, water dissolves its 
 own volume of this gas. As the pressure increases, the tem- 
 perature remaining the same, another volume is absorbed 
 for each atmosphere added ; but as the gas is condensed in 
 
238 
 
 INORGANIC CHEMISTRY. 
 
 the same ratio, according to Marriotte's law, it follows that 
 the volume of the gas dissolved by water is the same at all 
 pressures, while the mass is directly proportional to the press- 
 ure. Subjected to a pressure of 38*5 atmospheres at 0, 
 it condenses to a colorless limpid liquid, of specific gravity 
 0-923 at 0, 0-868 at 10, and 0-782 at 20. Its critical 
 temperature is 30'9 and its critical pressure is 73 '6 atmos- 
 pheres. Cooled to 65, the liquid solidifies to a transpar- 
 ent mass like ice. Since the pressure at this temperature 
 is 3*5 atmospheres, liquid carbon di-oxide can not exist at a 
 less pressure. Under atmospheric pressure it becomes a gas 
 
 or a solid. When therefore 
 a fine stream of the lique- 
 fied gas is allowed to es- 
 cape into the air, the rapid 
 evaporation of one portion 
 freezes another, producing 
 a snow-white, flocculent 
 mass, which may be formed 
 into balls like snow, and 
 which disappears with 
 great slowness, producing 
 a temperature of 78. 
 Moistened with ether and placed in the vacuum of an air- 
 pump, a temperature of 140 may be obtained. Carbon 
 di-oxide extinguishes the combustion of burning bodies 
 placed in it and is fatal to animal life, though less actively 
 than was formerly supposed. Diluted largely with air it 
 exerts a narcotic action, and has been proposed as an anaes- 
 thetic. Fatal effects have resulted from entering wells, fer- 
 menting vats, and other places in which this gas has accu- 
 mulated. Before going into such a place, a lighted candle 
 should be lowered into it ; if it is extinguished, the place is 
 unsafe. This gas constitutes the so-called " choke-damp" and 
 "after-damp" frequently found in coal-mines. 
 
 Fig. 77. Preparation of Carbon di-oxidc 
 
LIQUEFACTION OF CARBON Dl-OXIDE. 
 
 239 
 
 EXPERIMENTS. Carbon di-oxide may be condensed to a li(juid by 
 the apparatus either of Thilorier, in which the gas, cooled below 
 
 30-9, is liquefied by its own pressure; 
 
 or of Natterer, in which the pressure 
 
 is produced mechanically. Fig. 78 
 
 represents Bianchi's modification of 
 
 Natterer's condensing pump. The 
 
 piston is solid and is worked by a 
 
 crank and fl}--wheel, as shown in 
 
 the figure. The receiver at the top 
 
 of the pump-barrel is made of heavy 
 
 cannon-metal, and has a tight valve 
 
 below, and a screw-plug above, by 
 
 which the liquefied gas may be drawn 
 
 off. The tube leading to the pump 
 
 serves to convey the dry carbon di- 
 oxide; as the pump is worked, the 
 
 pressure in the receiver increases till 
 
 it reaches 38-5 atmospheres the re- 
 ceiver being surrounded with ice 
 
 when each additional stroke of the 
 
 pump liquefies the gas which it forces 
 
 into it. - In this way half a kilogram 
 
 of liquid carbon di-oxide may be ob- 
 tained in a short time. The receiver 
 
 is then removed from the pump and 
 
 inverted, and the gas allowed to escape into a peculiarly constructed 
 
 cylindrical box of metal, 
 which in the course of a few 
 seconds is filled with the sol- 
 id carbon di-oxide snow. On 
 moistening some of it with 
 ether in a wooden tray, and 
 immersing in the mixture 
 thermometer - bulbs f u 1 1 of 
 mercury, bullets of frozen 
 mercury are easily obtained. 
 From the ease with which 
 carbon di-oxide gas can be 
 
 prepared, it is used to illustrate many of the properties of gases. Its 
 
 density may be shown by balancing carefully a large beaker or a thin 
 
 Fig. 78. Bianchi's Pump for Con- 
 densing Gases. 
 
 Fig. 79. 
 
 3 extinguished by Carbon 
 di-oxide. 
 
240 
 
 INORGANIC CHEMISTRY, 
 
 Fig 80. Drawing 
 the gas from a 
 well. 
 
 Fig 81. Candle 
 extinguished 
 by C0 2 . 
 
 pasteboard box on one of the scale-pans of a large balance, and pour- 
 ing into it a second large beakerful of the gas. The scale-pan will at 
 once descend. A candle lighted and placed in the bottom of a beaker 
 is extinguished on pouring some of the gas upon it. If a stand car- 
 rying a series of lighted candles be 
 placed in a large jar (Fig. 79), and 
 carbon di-oxide gas be introduced 
 at the bottom, the candles will be 
 successively extinguished as the gas 
 rises around them. The accumula- 
 tion of this gas in wells, and its re- 
 moval therefrom by buckets, may 
 be shown by using a tall jar (Fig. 
 80) to represent the well, and a glass 
 bucket attached to a wire to draw 
 up the gas. If a lighted candle be 
 near, the gas may be poured from 
 the bucket upon the flame so as to 
 put it out (Fig. 81). This is the only gas which extinguishes flame 
 and renders lime-water milky. If a little clear lime-water be poured 
 into a jar of the gas, it becomes at once turbid from the production 
 of calcium carbonate. 
 
 314. Carbonic Acid. Formula H 2 CO 3 . Molecular tnafis 
 61 85. Carbonic acid is produced by the solution of carbon 
 di-oxide in water. It has not been obtained free from water, 
 a it readily decomposes into water and carbon di-oxide again 
 on slightly raising the temperature. The solution in water is a 
 distinctly acid liquid having the pungent odor and agreeable 
 acid taste so well known in the so-called soda-water, which is 
 made simply by condensing carbon di-oxide gas into water. 
 
 The salts of carbonic acid are called carbonates. Both 
 ortho- carbonates and meta- carbonates, having respectively 
 the general formulas M' 4 CO 4 and M' 2 CO.,, are known. 
 
 The simplest test for a carbonate is the effervescence which 
 results when it is treated with an acid. The escaping gas 
 may be passed through lime-water, which is rendered milky 
 by carbon di-oxide, and becomes clear again on the addition 
 of a dilute acid. 
 
PREPARATION OF CARBON MONOXIDE. 241 
 
 CARBON MONOXIDE OR CARBON YL. Formula CO. Molecular 
 mass 27*93. Molecular volume 2. Relative density 13 '96. 
 The mass of one liter is 1'25 grains (14 criths). 
 
 315. History. Carbon monoxide was discovered by Las- 
 sone in 1776, and also by Priestley in 1783. Its true nature 
 was determined by Woodhouse in 1800. 
 
 316. Preparation. Carbon monoxide may be prepared 
 (1) by the incomplete combustion of carbon, as when char- 
 coal and blacksmith's scales ferroso-ferric oxide are heated 
 
 Fe 3 0, + C. = Fe s + (CO), 
 
 (2) by the abstraction of oxygen from carbon dioxide, as 
 when this gas is passed over heated charcoal : 
 
 CO, + C = (CO), 
 
 (3) by heating oxalic acid with strong sulphuric acid : 
 
 H,C 2 O 4 = H 2 O + CO, + CO 
 
 Oxalic acid. Water. Carbon Carbon 
 
 di-oxide. monoxide. 
 
 EXPERIMENT. For preparing carbon monoxide from oxalic acid, 
 such an apparatus as is shown in Fig. 82 is required. The oxalic 
 
 Fig. 82. Preparation of Carbon monoxide. 
 
 acid is placed in the flask, enough sulphuric acid is added to cover 
 it. and the whole is heated in a cup of sand over the gas-flame. The 
 gases as evolved pass into a washing-bottle containing a solution of 
 
242 ixomtAyic CHEMISTRY. 
 
 potassium hydroxide, in bubbling through which the carbon di-oxide 
 is absorbed; the carbon monoxide thus purified maybe collected over 
 water. 
 
 317. Properties. Carbon monoxide is a colorless gas 
 having a peculiar suffocating odor. It is condensable to a 
 liquid, the critical temperature required being 139'5 and 
 the critical pressure 35'5 atmospheres. Its temperature un- 
 der atmospheric pressure is 190 and in vacuo 211. At 
 this point it solidifies, yielding a clear mass like ice if the 
 freezing be slow, but a snowy mass if it be rapid. (Olszew- 
 ski.) It requires 40 times its volume of water for solution. 
 Its specific gravity is 0'969. It is readily combustible, burn- 
 ing in the air or in oxygen with the characteristic lambent 
 blue flame often seen playing over a freshly fed anthracite 
 fire. It unites directly with chlorine in sunlight, forming 
 carbonyl chloride, or phosgene gas. It is totally irrespirable, 
 being an active narcotic poison, one per cent in the air prov- 
 ing fatal. Its presence in " water-gas," produced by passing 
 steam over red-hot charcoal, has been the occasion of legis- 
 lative interference ; the amount of carbon monoxide permis- 
 sible in a gas used for illumination being now fixed by law 
 in several of the States. The ready passage of this gas 
 through heated cast iron, and its consequent presence in 
 apartments heated by stoves or furnaces of this metal, has 
 been assumed as the cause of serious disease in many in- 
 stances. With sufficient ventilation, however, no danger from 
 this cause need be apprehended. 
 
 COMBUSTION. ; 
 
 318. Definition. In the wide sense of the term, com- 
 bustion is an energetic chemical action, attended with light 
 and heat.* It is commonly restricted, however, to the direct 
 union of a substance with oxygen. Two substances at least 
 are concerned in every combustion : the combustible, or the 
 body which burns ; and the supporter of combustion, or 
 
COMBUSTION AND COMBUSTIBLES. 243 
 
 the gas in which the combustion takes place. Commonly 
 we call hydrogen a combustible body, and air a supporter 
 of combustion ; but if the atmosphere were 
 hydrogen, then the oxygen would burn in it 
 and would be the combustible body. 
 
 EXPERIMENT. It is commonly said that coal-gas 
 burns in the air; but if ajar be filled with coal-gas, 
 and a combustion-spoon containing melted potas- 
 sium chlorate be introduced into it (Fig. 83), the 
 oxygen given off will burn in the coal-gas, the latter 
 being now the supporter. 
 
 319. Combustibles. The substances 
 which are burned as combustibles are very burning 
 numerous. Illuminating-gas has already been 
 mentioned. Of liquids, the vegetable oils known as rape, 
 olive, and turpentine, the animal oils called sperm and lard, 
 and the mineral oils derived from petroleum, may be men- 
 tioned. Of solids from the vegetable kingdom, wood and 
 bayberry wax ; from the animal, tallow and its product, 
 stearin ; and from the mineral, paraffin and the various sorts 
 of coal, are examples. These substances, though so different 
 in character and origin, all agree in the fact that they con- 
 tain carbon and hydrogen. Some contain oxygen in addi- 
 tion. 
 
 320. Combustion itself. Bodies are burned either for 
 purposes of warmth or of illumination. The temperature at 
 which bodies take fire in the air differs widely ; phosphorus, 
 for example, inflames at 50; sulphur at 260; hydrogen at 
 500; while coal-gas requires a temperature of 1000, and 
 nitrogen one of 5400. The amount of heat and light 
 evolved are proportional to the rapidity of the combustion. 
 In the decay of wood there is a true burning, called by 
 Liebig eremacausis ; but though the heat produced -is the 
 same in slow as in rapid combustion, the rise of temperature 
 in the former case is small, Phosphorus exposed to the air 
 
244 
 
 INOEGA NIC CHE MIS TE Y. 
 
 becomes luminous and slowly oxidizes ; but the temperature 
 never rises very high. When heated very hot, however, bod- 
 ies undergo a rapid combustion and evolve their maximum 
 temperature. When the matter burning is gaseous, then 
 the phenomenon of flame appears. The char- 
 acter of flame may be very well studied in that 
 of an ordinary candle (Fig. 84). The solid mat- 
 ter melted by the heat is drawn up in the wick 
 as a liquid, and is converted in the flame into 
 gas. In the center of the flame then there is 
 a dark cone of inflammable gas. Surrounding 
 this there is the luminous envelop, where con- 
 densed hydrocarbons are undergoing combus- 
 tion. And outside still is the portion of the 
 flame called the mantle, faintly blue in color, 
 composed, it is said, of burning hydrogen, and 
 cup-shaped at its lower portion. 
 
 EXPERIMENTS. By means of a glass tube the com- 
 bustible gas in the center of a candle-flame may be 
 easily led off and burned. Moreover, burning phos- 
 Fig. 84 Caudle- ph orus i s extinguished when placed in the center of a 
 large alcohol-flame, thus showing the absence of air 
 there. A porcelain plate held in the luminous cone will have the 
 condensed hydrocarbons deposited upon it; i. e., will be smoked. 
 
 In order to burn this gaseous matter in 
 the center of the flame, Argand proposed 
 the burner now known 
 by his name. In this 
 burner air is admitted 
 into this gaseous space 
 by making the flame 
 ring-shaped. Moreover, 
 by using a chimney to 
 
 Fig. 85. Argand burner produce a draft> great 
 
 brilliancy and steadiness are given to the flame. For heating 
 
 Fig. 86. Bunsen's 
 burner. 
 
COMBUSTIOX. 245 
 
 purposes, the best burner is Bunsen's burner (Fig. 86). The 
 
 <rus, issuing from a small central jet, is thoroughly mixed 
 
 with air entering by the lateral openings, 
 
 before it burns at the top of the tube. By 
 
 this dilution, which may be made equally 
 
 well with nitrogen or carbon di-oxide, the 
 
 density of the gas is so reduced that the 
 
 flame is non-luminous, and no smoke is 
 
 deposited on bodies held in it. 
 
 Flame, if cooled below a certain point, 
 is extinguished ; hence no flame can be 
 propagated through a cold, fine metal tube. 
 This was Davy's discovery, which gave 
 rise to the safety-lamp. 
 
 EXPERIMENTS. Wire-gauze is simply a col- 
 lection of small, short tubes. If a piece of such 
 gauze be pressed upon a gas-flame,- the flame 
 will not pass through it, but will be depressed 
 by it as if it were a solid plate. If held two 
 inches above the jet, the gas may be lighted 
 above the gauze, but the flame will not pass 
 through to the jet. With two pieces of gauze 
 the gas may be made to burn between them, but 
 
 neither above the upper nor below the lower; or above and below, 
 but not between them. 
 
 The miner's safety-lamp is represented in section in Fig. 
 87. It consists of a metallic lamp, the wick of which is sur- 
 rounded with wire-gauze, inclosed in a frame, by which the 
 whole may be suspended. The explosive mixture of air with 
 the gases of the mine can enter the gauze and burn within 
 it; but the flame can not pass outward through the gauze, 
 as it is thereby cooled and extinguished. Hence, with such 
 -a lamp an explosion of these gases can not take place. 
 
 321. Products of Combustion. The products of com- 
 bustion are of two sorts: 1st, the physical products, the 
 heat and light for which the combustion is generally pro- 
 
 17 
 
246 INORGANIC CHEMISTRY. 
 
 duced. 2d, the chemical products, which are to be con- 
 veyed away. The heat of combustion is measured in heat- 
 units; a heat-unit being the quantity of heat required to 
 raise one gram of water from to 1. Thus the heat of 
 combustion of hydrogen in oxygen is 34,180 units, and that 
 of carbon 8,080 units ; i. e., one gram of hydrogen or of car- 
 bon in burning in oxygen would heat 34,180 or 8,080 grams 
 of water from to 1. Knowing the quantity of carbon 
 and hydrogen in a given fuel, therefore, it is easy to calcu- 
 late its value for heating purposes. 
 
 The light given by an illuminating agent is measured by 
 comparison with that of a standard candle, as mentioned 
 under coal-gas. The instrument used for this comparison is 
 called a photometer. 
 
 The chemical products of combustion, since the combus- 
 tibles are composed of carbon and hydrogen, are obviously 
 carbon di-oxide and hydrogen oxide or water. 
 
 EXPERIMENTS. That water is produced in combustion may be 
 shown by holding a cold dry bell-glass over a candle-flame; it will 
 be at once bedewed with moisture. If now a little clear lime-water 
 be shaken in the jar, it will become milky, thus proving the presence 
 of carbon di-oxide. The same is true of respiration; a full breath 
 blown through a glass tube into lime-water will make it entirely 
 white. Air that has been twice respired will also extinguish a candle. 
 
 322. Ventilation. To carry off these effete products, 
 an efficient ventilation is necessary. This is generally se- 
 cured by a draft produced by heat, carrying all the foul air 
 into a ventilating shaft and thence into the outer air. Air 
 is too impure to breathe if it contains 0-10 per cent of car- 
 bon di-oxide ; but numerous other organic and inorganic im- 
 purities are produced by respiration and by combustion in 
 our houses which are quite as injurious to health, and which 
 must also be removed. 
 
 EXPERIMENTS. The principles of ventilation may be illustrated 
 by the following experiments: If a tall bell-glass, closed at top, be 
 
PSINCIPL A'.v or \ 'KSTILA T-ION. 
 
 247 
 
 placed over a stand on which are three lighted caudles at different 
 heights (Fig. 88), the heated carbon di-oxide will accumulate in the 
 upper part of the bell, and gradually extinguish the tapers from above 
 downward. By removing the stopper and rais- 
 ing the jar just before' the last 
 flame expires, the air is re- 
 newed and the taper will be 
 revived. 
 
 If a wide glass tube be fixed 
 in the neck of the bell, as 
 shown in Fig. 89, and this be 
 placed over a stand carrying 
 two tapers, both will be ex- 
 tinguished as before. But if 
 
 a small space be left between Fig. 88. Accumulation 
 tf?n wUha Draft the bell and the plate, the up- f f &$ part 
 
 per taper only will go out, 
 
 while the lower one will be supplied with air from below, its carbon 
 di-oxide and water escaping through the tube. 
 
 Again, if two large tubes, one within the other, be fixed in the 
 neck of a bell-glass (Fig. 90), and the whole be placed over a candle- 
 flame, the heated and effete products of combustion escape up the 
 center tube, while fresh air enters by the an- 
 nular space between the two, and the candle 
 burns actively. 
 
 Mines are usually ventilated by means of 
 two shafts, called the upcast and the down- 
 
 I 
 
 Fig 90. Double-draft Ap- 
 paratus. 
 
 Fig. 91. Upcast and Downcast 
 Shafts. 
 
 cast shafts, respectively. Their action may be represented by Fig. 91. 
 A square box has at each end a chimney, in one of which a candle is 
 kept burning. The air heated by the combustion rises, while fresh 
 
248 INORGANIC CHEMISTRY. 
 
 air descends in the opposite chimney to supply its place. Practically, 
 a coal fire is kept burning at the base of the upcast shaft, and by 
 suitably, arranging doors in the different parts of 
 the mine, the whole may be thoroughly ventilated. 
 If but one shaft is possible, then an arrangement 
 illustrated by Fig. 92 is generally employed. A 
 candle placed in a small bell-glass surmounted by 
 a wide tube will be extinguished. But if a piece 
 of tin-plate be inserted in the tube, the foul air will- 
 pass out on one side and fresh air will enter on 
 the other, and the candle will continue to burn. It 
 was the taking fire of such a partition, and the 
 consequent stoppage of ventilation, which caused 
 the terrible disaster at the Avondale colliery a few 
 years ago; the choke-damp as well as the fire-damp Fig. 92. Single shaft 
 accumulating in the mine in co/isequence, and pro- 
 ducing fatal results. 
 
 CARBON AND SULPHUR. 
 
 CARBON DI-SULPHIDE. Formula CS. r Molecular mass 75 -93. 
 Molecular volume 2. Relative density of vapor 37 '96. The 
 mass of one liter of carbon di-sulphide vapor 'is 3*40 grams 
 (38 criilis). 
 
 323. History and Preparation. Carbon disulphide 
 was discovered by Lampadius in 1796. It is always pre- 
 pared synthetically, by passing the vapor of sulphur over 
 charcoal heated to redness : 
 
 . C, + (S,), = (CS 2 ), 
 
 By agitating with lead hydrate or mercuric chloride, and 
 re-distilling from milk of lime, it is obtained pure. 
 
 324. Properties. Carbon di - sulphide is a colorless, 
 strongly refracting liquid, having, when perfectly pure, an 
 agreeable ethereal odor, like chloroform. Its specific grav- 
 ity is 1-27. It solidifies at 116, melts again at 110, 
 and boils at 46, yielding a dense vapor. It is very volatile, 
 evaporating rapidly in the air, with the production of great 
 cold. It is not soluble in water, Its vapor is readily inflam- 
 
249 
 
 mable, taking fire in the air even at 150, and burning with 
 a blue flame, producing carbon and sulphur di-oxides. The 
 brilliancy of its combustion with nitrogen di-oxide has been 
 already mentioned. 
 
 Carbon di- sulphide unites directly with alkali -sulphides 
 and sulphydrates, producing sulpho-carbonates M 2 CS S , anal- 
 ogous to carbonates M,CO 3 . By decomposing ammonium 
 sulpho - carbonate with hydrochloric acid, sulpho - carbonic 
 acid H 2 CS 3 is obtained as a reddish-brown oily liquid : 
 
 (NHJ 2 CS 3 + (HC1), = (NH 4 C1) 2 + H,Cfe 3 
 
 325. Uses. Carbon di-sulphide is used in the arts to 
 dissolve phosphorus, iodine, and sulphur ; the latter particu- 
 larly in vulcanizing india-rubber. It is largely used also as 
 a solvent for resins and bitumens ; and of late years has 
 been prepared on an immense scale for the extraction of the 
 various fatty and essential oils. 
 
 CARBON AND NITROGEN. 
 
 CYANOGEN. Formula C.,N 2 . Symbol Cy. Molecular max* 
 51-96. Molecular volume 2. Relative density -25*98. The 
 mass of one liter is 2%32 grams (26 criths). 
 
 326. History. Cyanogen was discovered by Gay-Lus- 
 sac in 1815. It was the first compound radical isolated, and 
 its discovery marks an era in the science of chemistry. Its 
 name is from xudvsoz, dark blue, it being a constituent of the 
 well-known pigment, prussian-blue. 
 
 327. Preparation. Cyanogen is usually prepared by 
 heating the cyanide of gold, silver, or mercury: 
 
 H K "Cy, = Hg + Cy, 
 
 EXPERIMENT. Instead of using the somewhat rare mercuric cya- 
 nide, a mixture of two parts of thorough^ dried potassium ferro- 
 cyanide and three parts mercuric chloride may be advantageously 
 substituted. The mixture is placed in a flask of hard glass (Fig. 93), 
 upon a sand-bath, and heated intensely by means of the double-draft 
 
250 INORUAMC CIIKMfxrHY. 
 
 gas-burner. The gas as it is evolved may be collected by displace- 
 ment, the pungent odor indicating when the jar is full. 
 
 328. Properties. Cyanogen is a colorless gas, with a 
 penetrating, pungent odor, resembling that of peach-blos- 
 soms. Its specific gravity is 1'806. Cooled to 2O7, or 
 subjected to a pressure of four and a half atmospheres at 
 15, it condenses to a colorless, highly refractive liquid, of 
 
 specific gravity 0'866, 
 which freezes at 34 
 to a transparent, ice- 
 like solid. Its critical 
 pressure is 61 '7 atmos- 
 pheres and critical tem- 
 perature 124. Cyan- 
 ogen gas is soluble in 
 one fourth of its vol- 
 ume of water and in 
 one twentieth of its vol- 
 ume of alcohol. It 
 takes fire readily in 
 
 the air, burning with 
 Fig. 93. Preparation of Cyanogen. 
 
 a characteristic purple- 
 red flame, producing carbon di-oxide and nitrogen. 
 
 Free or molecular cyanogen is composed of two atoms of 
 the cyanogen radical, Cy, being analogous to C1. 2 . Moreover, 
 atomic cyanogen acts precisely like an elemental monad, 
 forming compounds corresponding to the chlorides, thus : 
 
 Potassium chloride KC1. Potassium cyanide KCy. 
 
 Hydrochloric acid HC1. Hydrocyanic acid HCy. 
 
 Hypochlorous acid HC1O. Cyanic acid HCyO. 
 
 The thermo-chemical relations of carbon are noteworthy. 
 Berthelot has shown that in the form of diamond one gram 
 of carbon in uniting with oxygen evolves 7,859 heat-units, 
 one gram of graphite 7,901, and one gram of charcoal 8,137 
 
SJLfCON. 251 
 
 heat-units. The heat of formation of methane CH 4 from 
 amorphous carbon and hydrogen is 21,750 heat-units; of 
 ethylene 2,700, and of acetylene 48,300 heat-units. This 
 absorption of energy results from the fact that to separate 
 the carbon atoms in the molecule and to convert the solid 
 carbon into gas, work must be done upon it ; calculation show- 
 ing that 12 grams of amorphous carbon thus separated ab- 
 sorb 38,300 heat-units. The readiness with which acetylene 
 and ethylene unite directly with hydrogen is thus* apparent. 
 To form CC1 4 from chlorine and amorphous carbon, 21,030 
 heat-units must be set free ; so that, to judge by this standard, 
 the attraction of carbon for hydrogen is practically the same 
 as that for chlorine. The heat of formation of carbon mon- 
 oxide CO is 28,500 units ; that of carbon di-oxide CO,, also 
 from amorphous carbon and oxygen, is 96,900 units. Hence 
 when CO burns to CO 2 , 68,400 heat-units are evolved. The 
 heat of formation of CS 2 is negative and is 12,600 units. 
 The formation of free cyanogen C 2 N 2 is also endothermic, 
 the absorption of heat being 65,700 units. 
 
 2. SILICON. 
 
 Symbol Si. Atomic mass 28. Valence IV. Relative density 
 28 (?). Molecular mass 56 (?). Molecular volume 2. The 
 mass of one liter of silicon-vapor is 2 '5 grams (28 critJis) (?). 
 
 329. History and Occurrence. Silicon was first ob- 
 tained pure by Berzelius in 1823. It does not occur free 
 in nature, but exists abundantly in combination with oxy- 
 gen, forming the well-known substance, quartz. Combined 
 with oxygen, and also with potassium, aluminum, and other 
 metals, it constitutes a large portion of the rocks which make 
 up the solid crust of the earth. 
 
 330. Preparation. Silicon may be prepared by the 
 action of sodium upon potassium fluo-silicate : 
 
 K 2 SiF 6 + Na 4 = (KF) 2 + (NaF) 4 + Si 
 
252 IXOIH'.AXIC CIIEM1STHY. 
 
 331. Properties. Silicon as thus obtained is an amor- 
 phous, nut-brown, lusterless powder, which may be crystal- 
 lized by solution in melted zinc, in long needles made up 
 of adhering regular octahedrons; or in melted aluminum, 
 in flat octahedral plates. In this form it is a dark iron-gray 
 solid, with a metallic luster and a specific gravity of 2 '49. 
 It is hard enough to scratch glass, and melts at a tempera- 
 ture above the melting point of iron. Heated in the air, 
 the amorphous silicon takes fire and burns, producing silicic 
 oxide. 
 
 SILICON AND HYDROGEN. 
 
 HYDROGEN SILICIDE. Formula H 4 8i. Molecular mans 32. 
 
 332. History and Preparation. Hydrogen filicide 
 was first observed by Wohler and Buff in 1857; but it was 
 first obtained pure in 1867 by Friedel and Ladenburg. 
 
 It may be obtained, mixed with hydrogen, by the electro- 
 lysis of a solution of sodium chloride, a plate of aluminum 
 containing silicon being made the positive electrode. A 
 better process is to decompose magnesium silicide by hydro- 
 chloric acid : 
 
 Mg. 2 Si -f (HC1) 4 = (MgCl. 2 ) 2 + H 4 Si 
 
 It is obtained perfectly pure by the action of sodium upon 
 tri-ethyl silico-formate. 
 
 EXPERIMENT. For preparing 
 magnesium silicide, 40 parts fused 
 magnesium chloride, 35 parts dried 
 sodium fluo-silicate, 10 parts fused 
 sodium chloride, and 20 parts of 
 sodium cut into small pieces, are 
 well mixed together and thrown 
 into a red-hot hessian crucible, 
 which is then covered and heated Fig . 94> Preparation of Hydrogen 
 until the sodium ceases to burn. Silicide. 
 
 When cold, a dark layer of the impure silicide will be found at the 
 bottom. It is detached and preserved in a tight bottle. 
 
iKX SI LIC-I !)/<;. 253 
 
 To obtain hydrogen silieitle, the coarsely pulverized slag thus made 
 is placed in a wide-mouthed bottle (Fig. 04), through the cork of 
 which passes a funnel tube for adding the acid, and a wide delivery 
 tube for the escape of the gas. The bottle is then filled with cold 
 water recently boiled to expel the air and placed by the water- 
 cistern as shown in the figure. Upon pouring concentrated hydro- 
 chloric acid down the funnel tube taking especial care that it carries 
 in no air-bubbles hydrogen silicide gas is evolved and may be col- 
 lected for use. 
 
 333. Properties. Hydrogen silicide is a colorless gas, 
 which, when mixed with hydrogen, is spontaneously inflam- 
 mable in the air, yielding white clouds of silicic oxide. At 
 the temperature of 5, a pressure of 70 atmospheres con- 
 denses it to a liquid. Burned from a jet, it gives a brilliant 
 white flame, w r hich deposits a brown layer of silicon upon a 
 piece of porcelain held in it. When the tube conveying the 
 <zas LS heated, a mirror-like deposit of silicon takes place 
 within it. Hydrogen silicide is not soluble in water. Passed 
 into cupric sulphate or silver nitrate, it throws down cupric 
 and silver silicides. It is decomposed by potassium hydrox- 
 ide, one volume of the gas yielding four volumes of hydro- 
 
 SiH 4 + (HKO) 4 = K 4 Si0 4 + H 8 
 
 One half of this hydrogen comes from the silicide ; each 
 molecule must therefore contain two molecules of hydrogen, 
 or four atoms. 
 
 SILICON AND OXYGEN. 
 
 SILICIC OXIDE. Formula SiO 2 . Molecular mass 59*92. 
 
 334. Occurrence. Silicic oxide, or silica, occurs abun- 
 dantly in nature in the pure and crystallized form known 
 as quartz or rock-crystal ; and more or less deeply colored 
 in the minerals called amethyst, jasper, agate, chalcedony, 
 and carnelian. A beautiful and probably polymeric form is 
 known as opal. As sandstone it forms a rock-nmterial in 
 geology. Its combinations with metallic oxides, called sili- 
 
254 lyoiidAXIC CHEMISTRY. 
 
 cates, form by far the most numerous class of mineral sub- 
 stances. Silicic oxide also occurs dissolved in many natural 
 waters, particularly those of thermal springs ; it stiffens the 
 stems of the cereal grains, and has been also found in animal 
 tissues. 
 
 335. Preparation. Silicic oxide may be prepared either 
 by the oxidation of silicon, as when it burns in the air, or 
 by the dehydration of silicic acid : 
 
 H,SiO 3 -- H,0 = SiO 2 
 
 336. Properties. Silicic oxide, as usually obtained, is 
 a white amorphous powder, though in nature it occurs often 
 in the form of hexagonal prisms, crowned by six- 
 
 sided pyramids (Fig. 95). It has a specific grav- 
 ity of 2 '60, is so hard as readily to scratch glass, 
 and is fusible only by the oxyhydrogeu flame. It 
 is but slightly soluble in water, and is unattacked 
 by acids, except the hydrofluoric. Fused with 
 salts of the alkali-metals, it combines with the 
 basic oxide, forming a silicate, and sets the nega- 
 tive or acid oxide free. 
 
 337. Silicic Acid. Ortiw H 4 Si lv O 4 . Meta 
 H 2 Si lv O 3 . Ortho-silicic acid may be prepared by 
 
 the action of water on silicon fluoride, or by decomposing a 
 solution of an alkaline silicate by an acid. It is obtained as 
 a gelatinous precipitate, losing water when dried, and pro- 
 ducing meta-silicic acid. By dialysing a solution of an alka- 
 line silicate in hydrochloric acid, the acid passes through the 
 membrane, and there is left in the dialyser an aqueous solu- 
 tion of silicic acid, which may be concentrated by boiling in 
 a flask until it contains 37 per cent. It is a tasteless, lim- 
 pid liquid, is slightly acid, and becomes a jelly on standing. 
 On evaporation it leaves meta-silicic acid. A third silicic 
 hydrate, called para -silicic or di- silicic acid, H 6 Si 2 O 7 , is 
 known. 
 
ttELATio\s or TIIK r.////;av aitour. 255 
 
 The silicates are classified by Dana as uni-silicates, M' 4 SiO 4 , 
 corresponding to ortho-silicates, and bi-silicates, M' 2 SiO,, cor- 
 responding to meta-silicates. Some of the intermediate vari- 
 eties, such as wernerite [Na, Ca, Al]", Si 2 O 7 , are di- or para- 
 silicates ; others, as lepidolite [K, Li, Mn, Al]" 4 Si 3 O 10 , and 
 labradorite [Ca, Na, Al]" 4 Si 3 O 10 , are derived from tri-silicic 
 acid, H 8 Si 3 O 10 . Besides these there is a third class of sili- 
 cates Dana's sub-silicates which are meta - aluminic sili- 
 cates, derived from meta-aluminic base H 4 A1 2 O 5 by replac- 
 ing the H 4 by Si lv . In this way the mineral cyanite, SiAl. 2 O 5 , 
 is produced. Potassium and sodium meta-silicates are solu- 
 ble in water, and their solutions are used in the arts under 
 the name of soluble glass. Potassio-lead silicate is known in 
 commerce as flint glass, and sodio-calcium silicate as window 
 glass. Crown glass, used for optical purposes, and Bohemian 
 glass, of which chemical vessels are made, are potassio-cal- 
 cium silicates. Plate glass contains potassium, sodium, and 
 calcium as its basic constituents. 
 
 RELATIONS OF THE CARBON GROUP. 
 
 338. Carbon, silicon, and titanium, as well as zirco- 
 nium, cerium, and thorium, are closely related to each other 
 in the gradation of their physical properties as well as in the 
 similarity of their chemical compounds. Their tetrad char- 
 acter is well marked, since they form tetra-chlorides, di-ox- 
 ides, and di-sulphides, and since carbon and silicon form also 
 tetra-hydrides. The elements of this group are also capable 
 of entering into combination as double atoms, with an equi- 
 valence of six, forming the chloride of carbon C 2 C1 6 and the 
 oxide of titanium Ti. 2 O 3 , for example. Finally they all form 
 normal ortho-hydrates, which are tetra-basic or acidic, and 
 derived meta-hydrates, which are di-basic or acidic. 
 
IS ORGANIC CHEMISTRY. 
 
 EXERCISES. 
 $1* 
 
 1. Mention the forms in which carbon occurs in nature. 
 
 2. How are they proved to be chemically identical? 
 
 3. One kilogram of carbon in burning will evaporate how much 
 water? 
 
 4. How is methane produced naturally? How hiade artificially? 
 
 5. What volume of methane from a kilogram of sodium acetate? 
 
 6. One gram of alcohol yields what volume of ethyk'iie? 
 
 7. A cubic meter of ethylene contains what volume of H? 
 
 8. For what reason is ethylene written C 2 H 4 and not CH.,? 
 
 9. What volume of O is required to burn 250 grams of ethylene? 
 
 10. How is acetylene prepared? What are its properties? 
 
 11. Describe the process for making coal-gas. 
 
 12. One kilogram of C in burning gives what mass of CO.,? 
 
 13. What mass of KC1O 3 will completely burn 5 grams of C? 
 
 14. What volume of air is required to burn one liter of marsh-gas. 
 of ethylene, and of acetylene? What volume of CO., is produced in 
 each case? 
 
 15. What volume of carbon di-oxide will be produced by burning 
 a kilogram of cannel coal, 85-81 per cent of which is carbon? 
 
 16. One cubic centimeter of marble (specific gravity 2-7) contains 
 what volume of CO 2 ? 
 
 17. How many kilograms of carbon in 1,000 kilograms of chalk? 
 
 18. What volume of CO 2 must be passed over charcoal to yield a 
 liter of CO? What is the increase in mass? 
 
 19. 25 grams oxalic acid yield what volume of CO at 10 and 740 
 millimeters pressure? 
 
 20. To burn one gram of CS 2 requires what volume of O? 
 
 21. What volume of air is required to burn one liter of CN? 
 
 22. What are the analogies of cyanogen ? 
 
 2. 
 
 23. Give the method of preparation and the properties of silicon. 
 
 24. Into what classes are the silicates divided ? Illustrate. 
 
PROPERTIES OF BORON. 257 
 
 CHAPTEE SIXTH. 
 
 1. BORON. 
 
 Symbol B. Atomic mass 10 '95. Valence ill. Molecular mass 
 21-90 .(?). Molecular volume 2. Specific gravity 2 '68. 
 
 339. History and Occurrence. Under the Arabic 
 name buraq, corrupted into borax, a salt obtained from cer- 
 tain lakes in Thibet, and containing boron as an essential 
 component, has long been imported into Europe. From 
 this, in 1702, Homberg- obtained boric oxide ; and from 
 boric oxide, Davy, in 1807, by the aid of electricity, and 
 Gay-Lussac and Thenard, in 1808, by chemical means, 
 obtained pure boron. It \vas first obtained crystallized by 
 Wohler and Deville in 1856. The mineral sassolite is boric 
 acid, H ;j BO. H ; and borax, boracite, and larderellite are native 
 borates of sodium, magnesium, and ammonium respectively. 
 
 340. Preparation and Properties. Amorphous boron 
 may be prepared by the action of sodium upon potassium 
 fluoborate, thus : 
 
 (KBF 4 ), + Na H = (KF), + (NaF) 6 + B 2 
 In this form boron is a soft, greenish-brown powder, read- 
 ily oxidized by nitric acid, and fusible at the heat of the 
 oxy-hydrogen flame. It may be obtained crystallized by dis- 
 solving it in melted aluminum, allowing the mass to cool, 
 and removing the aluminum by hydrochloric acid. Short 
 quadratic octahedrons are left undissolved, which vary from 
 honey-yellow to garnet-red in color, have a specific gravity 
 of 2-63, and are nearly as hard, as lustrous, and as highly 
 refractive as the diamond itself. These crystals contain a 
 little aluminum, are infusible, and are combustible with dif- 
 
258 INOKGAXIC CHEMISTRY. 
 
 ficulty even in oxygen. They are not attacked by melted 
 niter. The so-called graphitoidal boron is a compound of 
 boron and aluminum. 
 
 341. Hydrogen Boride, H 3 B. A compound of hydro- 
 gen and boron has been obtained by acting on magnesium 
 boride with hydrogen chloride. A colorless gas is set free, 
 which burns with a bright green flame, with separation of 
 boric oxide. Upon holding a cold porcelain surface in the 
 flame, a brown coating of boron is deposited on it. Con- 
 ducted into silver-nitrate solution, it produces a black pre- 
 cipitate in it consisting of silver and boron. 
 
 342. Boric Oxide, B 2 O 3 . Boric oxide is formed when- 
 ever boron burns in the air or in oxygen. It is usually ob- 
 tained by igniting its hydrate, boric acid. A viscid mass is 
 left, which solidifies to a colorless, brittle, transparent glass, 
 of specific gravity 1 '83. It unites directly with positive ox- 
 ides to form borates, expelling the more volatile negative 
 oxides with which they are combined. 
 
 343. Boric Acid, H 3 BO 3 . Boric acid occurs free in na- 
 ture, especially in volcanic districts, as in Tuscany, where it 
 issues, with steam and gaseous matters, from fissures in the 
 earth, into natural or artificial ponds or lagoons, the water 
 of which soon becomes charged with the acid. This water is 
 then evaporated and the acid crystallized out. Boric acid 
 may be prepared from sodium borate or borax, by dissolving 
 three parts of it in twelve of boiling water, adding one part 
 of sulphuric acid, and allowing the whole to cool. The boric 
 acid separates in white crystalline scales, of specific gravity 
 1-48, soluble in two and a half parts of water at 18, and 
 freely soluble in alcohol. Its aqueous solution reddens lit- 
 mus paper and turns turmeric paper brown. Its solution 
 in alcohol burns with a green flame. This is the normal or 
 ortho-boric acid. By heating it to 120 it loses one mole- 
 cule of water and yields meta-boric acid, HBO 2 . Boric acid 
 shows a strong tendency to condensation, thus forming mul- 
 
PEE P. I If A TION OF AL UMINUM. 259 
 
 tiple salts. Borax, or sodium tetraborate, Na, 2 B 4 O T , is an 
 example. It is found native in the waters of certain lakes 
 in Thibet and California. It is used largely as a flux in 
 working metals. Boron acts in some cases as a basic ele- 
 ment. Salts of this element are known, such as the disul- 
 phate (BO)HS 2 O 7 and the phosphate BPO 4 . 
 
 2. ALUMINUM. 
 Symbol Al. Atomic mass 27*04. Valence III. 
 
 344. History and Occurrence. Aluminum oxide, or 
 alumina, was long confounded with lime, from which it was 
 first distinguished by Marggraff in 1754. Oersted, in 1826, 
 first prepared the chloride ; and from this, in 1828, Wohler 
 obtained the metal. His process was made a commercial 
 one by St. Claire Deville in 1854. The metal was first pre- 
 pared from cryolite by H. Rose in 1855. 
 
 Aluminum, next to oxygen and silicon, is the most abun- 
 dant element in nature. The minerals corundum, ruby, and 
 sapphire are aluminum oxide ; diaspore, chrysoberyl, and 
 spinel are aluminates ; micas, feldspars, and clays are alu- 
 minum silicates ; cryolite is sodium-aluminum fluoride ; and 
 many other minerals contain it as an essential constituent. 
 Its name comes from the Latin alumen, alum, which sub- 
 stance was largely imported into Europe from the East until 
 the fifteenth century. 
 
 345. Preparation and Properties. Aluminum is gen- 
 erally prepared commercially by- the process of Deville, which 
 consists in reducing the chloride with sodium. At the works 
 of Morin, in Paris, ten parts sodio-aluminum chloride, five 
 parts of fluor-spar or cryolite, and two parts of sodium are 
 mixed together and thrown upon the hearth of a reverber- 
 atory furnace, previously heated to full redness. A violent 
 action takes place, great heat is evolved, and the liquefied 
 mass of slag and metal collects at the back of the furnace. 
 
260 INORGAXIC CHEMISTRY. 
 
 The latter is drawn off and cast into ingots. This process 
 has recently been greatly improved by Castner. Tissier, at 
 Amfreville, makes aluminum from the mineral cryolite, after 
 the method proposed by H. Rose ; and in this country it Ls 
 now made in considerable quantity from the same mineral 
 by electrolysis, by a process devised by Hall. 
 
 Aluminum is a brilliant bluish-white metal, capable of 
 taking a fine polish. It crystallizes in octahedrons, and con- 
 ducts heat and electricity readily. It is highly sonorous, is 
 very light, specific gravity 2 '56 to 2-67, and is very mallea- 
 ble and ductile. Its tenacity is about equal to that of silver, 
 and it is slightly magnetic. After fusion it is soft, but be- 
 comes hard by hammering. It melts at a temperature of 
 700, but little above the fusing-poiut of zinc, but is not 
 volatile. It tarnishes very slowly in the air, though it burns 
 readily in thin leaves when heated in oxygen. Sulphuric 
 and nitric acids are without action upon it, though hydro- 
 chloric acid and alkali-hydrates attack it readily. 
 
 Aluminum is used in the arts chiefly for ornamental pur- 
 poses, for which its luster, its whiteness, and its unalterabil- 
 ity in the air well adapt it. Its lightness makes it useful 
 for weights, and for astronomical and physical instruments. 
 Culinary utensils have also been made of it. Alloyed with 
 copper, it forms aluminum-bronze, which, when it contains 
 ten per cent of aluminum to ninety of copper, is hard, mal- 
 leable, as tenacious as steel, and takes a fine polish. 
 
 COMPOUNDS OF ALUMINUM. 
 
 346. Aluminum Chloride. Formula AlCl. r The com- 
 pounds of aluminum until recently were supposed to contain 
 this element with a double atom. But the latest vapor-den- 
 sity determinations, particularly of its organic compounds, 
 seem to establish its triad character, and thus to confirm the 
 indications of the periodic series. Aluminum chloride is 
 prepared by passing chlorine over an ignited mixture of the 
 
ALUMINUM OXIDE AND SALTS. 261 
 
 oxide and charcoal. It is a colorless, semi-crystalline, waxy 
 substance, fusible and volatile, and having a vapor-density 
 of 134. It combines violently with water, forming the hy- 
 drate A1C1 3 , 6 aq. Chlorine, passed over an ignited mixture 
 of salt, aluminum oxide, and charcoal, yields sodio-alumi- 
 num chloride, NaAlCl 4 , as a white crystalline solid, which 
 melts at 200. Aluminum fluoride, A1F 3 , combined with 
 sodium fluoride, occurs native in the mineral cryolite. 
 
 tt47. Aluminum Oxide. Formula A1 2 O 3 . Aluminum 
 oxide occurs native in the mineral corundum, which includes 
 the precious stones known as the ruby and the sapphire, as 
 well as the valuable polishing material called emery. It may 
 be prepared by the combustion of the metal in oxygen or 
 by igniting the hydrate. It is found in nature crystallized 
 in rhombohedral forms, with a specific gravity of 3 '90, and 
 scarcely inferior in hardness to the diamond. Aluminum 
 hydrate, A1(OH) 3 , or ortho-aluminic base, occurs native as 
 gibbsite. It is obtained by precipitating any salt of alumi- 
 num by ammonium hydrate. Meta-aluminic base AIO(OH) 
 is also known, occurring in nature as the mineral diaspore. 
 Aluminic hydrate acts as an acid with basic radicals, forming 
 aluminates ; sodium ortho-aluminate, Na 3 AlO 3 , and rneta- 
 aluminate, NaAlO 2 , and potassium meta-aluminate, KA1O 2 , 
 have been prepared artificially ; and beryllium aluminate, Be" 
 (A1O 2 ) 2 , or chrysoberyl ; magnesium aluminate, Mg"(AlO 2 ) 2 , 
 or spinel ; and zinc aluminate, Zn"(AlO 2 ) 2 , or gahnite, are 
 well-known minerals. With strong acids, aluminum hydrate 
 acts as a base. With sulphuric acid, it yields aluminum 
 sulphate, A1 2 (SO 4 ) 3 , 18 aq., the mineral alunogen; it is used 
 in dyeing. It forms a characteristic class of double sulphates 
 called alums, whose general formula is MA1(SO 4 ) 2 , 12 aq., M 
 being generally K or (NH 4 ). They all crystallize in regular 
 octahedrons, are acid in their reaction, and have a styptic 
 taste. Aluminum phosphate, A1(PO 4 ), is known in the 
 hydrated form. The silicates of aluminum constitute an 
 
 18 
 
262 INORGANIC CHEMISTRY. 
 
 important class of minerals. Orthoclase is a potassio-alumi- 
 num silicate, albite a sodio-aluminum silicate, and labrador- 
 ite a calcio-aluminum silicate. Clay is a more or less pure 
 aluminum silicate, Al 2 Si. 2 O 7 , 2 aq. It is used in pottery, the 
 finer kinds being known as kaolin, or porcelain clay. 
 
 RELATIONS OF THE GROUP. 
 
 348. To this group belong also scandium, yttrium, lan- 
 thanum, and ytterbium, all rare elements. They are all 
 trivalent and form similar compounds. Boron is the most 
 strongly negative, and the acidic character seems to diminish 
 as the atomic mass increases ; so that ytterbium would be 
 the most strongly positive. The intermediate electro-chem- 
 ical character of the group appears in the fact that, while 
 boron gives an acid hydrate, B(OH) :i , aluminum gives a 
 basic one, A1(OH) 3 ; taken in connection with the further 
 fact that BPO 4 is as stable a salt as magnesium aluminate, 
 Mg(AlO 2 ). 2 ; and yet in the latter compounds the electro- 
 chemical character is reversed. 
 
EXERCISES. 263 
 
 EXERCISES. 
 
 1. In what forms does boron occur? 
 
 '2. How is hydrogen boride prepared? 
 
 8. What mass of B. 2 ;5 can be obtained from 10 grams of borax? 
 
 4. Write the constitutional formula of borax. 
 
 5. In what compounds does aluminum occur in nature? 
 
 6. Give the process adopted by Morin for preparing it. 
 
 7. Cryolite has the formula Na a AlF 6 ; what per cent of aluminum 
 does it contain? 
 
 8. What is the mass of an aluminum ball 5 centimeters in diam- 
 eter ? 
 
 9. Write the graphic formula of aluminum chloride. Oxide. 
 
 10. Under what names does aluminum oxide occur? 
 
 11. Calculate the percentage composition of the mineral cbryso- 
 beryl. 
 
 12. Fibrolite contains 36-8 per ce:it of silicic oxide and 63-2 per 
 cent of aluminum oxide; what is its formula? (Molecular mass 163.) 
 
264 INORGANIC CHEMISTRY. 
 
 CHAPTER SEVENTH. 
 
 POSITIVE TETKADS. 
 
 1. TIN. 
 
 Symbol Sn. Atomic mass 117*8. Valence II and IV. Molec- 
 ular mass 235-6 (?). 
 
 349. History and Occurrence. Tin has been known 
 from the remotest antiquity. It is spoken of by Moses (Num- 
 bers, xxxi, 22) ; and Homer mentions it in the Iliad under 
 the name xaffffirepo-. Much of the brass of the ancients was 
 a copper and tin bronze, the tin being obtained from Corn- 
 wall ; whence Herodotus speaks of the British Isles as the 
 xaffffiTzptdzq or tin-islands. The principal ore of tin is stannic 
 oxide, known as the mineral cassiterite. It occurs in veins 
 running through ancient rocks vein or mine-tin and also 
 in the beds of water-courses, from the disintegration of these 
 rocks stream tin. The principal localities of tin ore are 
 Cornwall, England, and Banca and Malacca, India. It has 
 been found in New Hampshire and in California in this 
 country. 
 
 350. Preparation and Properties. The ore is pul- 
 verized, roasted, and washed, and is then smelted with char- 
 coal, which removes the oxygen. It is refined by melting 
 and thrusting into it a stick of wet wood ; the impurities 
 rise to the surface and are skimmed off. The tin is then 
 ladled into molds, the upper layers being the purest. It 
 comes into commerce as grain-tin, in irregular fragments 
 produced by allowing the hot ingots to fall from a height ; 
 and as block-tin, a less pure form, in ingots. The purest 
 
PREPARATION OF STANNIC CHLORIDE. 265 
 
 tin is imported from the island of Banca, and is known as 
 straits-tin. 
 
 Tin is a soft, brilliant-white metal, of specific gravity 7*29. 
 It is dimorphous, crystallizing in forms belonging to the iso- 
 metric and the quadratic systems. It is very malleable, and 
 may be beaten into leaves one fortieth of a millimeter thick ; 
 at 100 it is ductile and may be drawn into wire. Its tenac- 
 ity, however, is small. It crackles when a bar of it is bent, 
 producing what is known as the cry of tin. It has a pecul- 
 iar odor, and is a good conductor of heat and electricity. It 
 melts at 230, and distills at a white heat. Heated in the 
 air, it burns readily to oxide, though it retains its luster in 
 air at ordinary temperatures. Acids attack it readily. 
 
 351. Uses. Tin is used in the arts for making tin foil, 
 for covering iron in the preparation of tin plate, and for 
 alloys. Pewter, britannia, queen's metal, and solder are alloys 
 of tin and lead, containing sometimes a little antimony and 
 bismuth. Bell-metal, gun-metal, bronze, and speculum-metal 
 are essentially alloys of tin and copper. In gun-metal and 
 bronze, the tin constitutes one part in ten or twelve, in bell- 
 metal one part in five, and in speculum -metal one part in 
 three. 
 
 TIN AND CHLORINE. 
 
 STANNIC CHLORIDE. Formula SnCl 4 . Molecular mass 259 -28. 
 
 352. Preparation and Properties. Stannic chloride 
 known to the alchemists as Liquor fumans Libavii may 
 be obtained by the direct action of chlorine gas upon tin, or 
 by distilling mercuric chloride with tin filings : 
 
 (HgCl 2 ) 2 + Sn = Hg, 2 + SnCl, 
 
 It is a colorless, fuming liquid, of specific gravity 2 '28, which 
 boils at 115. Its vapor-density is 130. It unites with water 
 readily, evolving heat, and forming two crystalline hydrates. 
 With alkali-chlorides it forms definite compounds, the potas- 
 sium salt being K. 2 SnCl (i . It is used in dyeing. 
 
266 INORGANIC CHEMISTRY. 
 
 STANNOUS CHLORIDE. Formula SnCL,. Molecular mas* 
 188-54. 
 
 353. Preparation and Properties. Stannous chloride 
 may be prepared by distilling tin filings with mercurous chlo- 
 ride, or by the action of heat upon its hydrate. It is a gray- 
 ish-white translucent solid, which melts at 250, and may be 
 distilled at 620; at 900 its vapor-density is normal. By 
 solution in water and evaporation, large colorless monoclinic 
 prisms are produced, having the composition SnCl 2 , 2 aq. 
 These crystals are known as the " tin-salt" of the dyer, for 
 whose use they are commonly made by dissolving metallic 
 tin in hydrochloric acid. Stannous chloride is used in the 
 laboratory as a reducing agent. 
 
 TIN AND OXYGEN. 
 
 STANNIC OXIDE. Formula Sn lv O 2 . Molecular mass 149-72. 
 
 354. Preparation and Properties. Stannic oxide oc- 
 curs native as the mineral cassiterite, or tin-stone, crystal- 
 lized in square prisms, terminated by the faces of the square 
 octahedron. It may be prepared by burning the metal in 
 air, or by igniting either of the hydrates. It is then obtained 
 as a white powder, of specific gravity 6 -6, insoluble in all 
 acids except hydrofluoric. Owing to its hardness it is used 
 for polishing glass, under the name of putty-powder. When 
 fused with alkali-hydrates it forms stannates. 
 
 355. Stannic Acids. Oriho H 4 SnO 4 and Meta H 2 SnO : ,. 
 Ortho-stannic acid is precipitated from alkaline stannates by 
 acids, or from stannic chloride by ammonia, as a gelatinous 
 mass, which loses water on drying in vacuo, and becomes 
 meta-stannic acid. When tin is oxidized by nitric acid, a 
 polymeric form of meta-stannic acid is produced, which when 
 dried at 100 has the formula H 10 Sn.O 15 . Sodium meta-stan- 
 nate Na 2 SnO 3 , 3 aq., made by fusing native tin-stone with 
 sodium hydrate, is used as a mordant in dyeing. 
 
HlSTOliY JA7> (MT-rilRENCE OF LEAD. 267 
 
 STANNOUS OXIDE. Formula Sn"0. Molecular mass 133-76. 
 
 356. Preparation and Properties. Stannous oxide 
 is obtained when stannous oxalate is heated in close vessels. 
 It is a black powder of specific gravity 6 '6, crystallizing in 
 the isometric system, and combustible when heated in the 
 air. With water it forms a ^hydrate which absorbs oxygen 
 gradually from the air, and passes into stannic acid. With 
 sulphuric acid it forms stannous sulphate Sn"SO 4 . 
 
 TIN AND SULPHUR. 
 
 STANNIC SULPHIDE. Formula Sn lv S 2 . Molecular mass 181 -76. 
 
 357. Preparation and Properties. Stannic sulphide 
 is prepared by heating together tin-amalgam, sulphur, and 
 ammonium chloride (sal-ammoniac). A golden-yellow crys- 
 talline powder having a metallic luster and a specific gravity 
 of 4'6 is left in the vessel. This substance was known, to 
 the alchemists under the name of aurum musivum, or mosaic 
 gold. It is used as a bronze-powder. 
 
 2. LEAD. 
 
 Symbol Pb. Atomic maw 206 '4. Valence II and IV. Specific 
 gravity 11*37. 
 
 358. History and Occurrence. Lead has been known 
 from the earliest ages of history. It is mentioned in the 
 book of Job and elsewhere in the sacred writings. The Ro- 
 mans worked the lead ores of Spain and of England, and 
 the Carthaginians those of Spain, the extent of their mining 
 and smelting operations exciting surprise, even at the pres- 
 ent day. The principal workable ore of lead is its sulphide, 
 or galenite ; though it occurs also somewhat abundantly as 
 carbonate, or cerussite ; as sulphate, or anglesite ; as chloro- 
 arsenate, or mimetite ; as chloro-phosphate, or pyromorphite ; 
 and in other forms. 
 
 ** 
 
268 INORGANIC CHEMISTRY. 
 
 359. Preparation and Properties. Lead is prepared 
 from the sulphide by a comparatively simple metallurgical 
 process. The ore is first roasted on the floor of a reverbera- 
 tory furnace, by which both oxide and sulphate of lead are 
 produced. The furnace is then closed tight, and these prod- 
 ucts react upon the undecomposed lead sulphide as follows : 
 
 (PbO) 2 + PbS = S0 2 + Pb 3 
 
 Lead oxide. I^ead sulphide. Sulphurous oxide. Lead. 
 
 PbSO 4 + PbS = (S0 2 ) 2 + Pb 2 
 
 Lead sulphate. Lead sulphide. Sulphurous oxide. Lead. 
 
 When the ore contains impurities, it is smelted by fusing it 
 with iron, ferrous sulphide and lead being produced. Other 
 methods are employed for smelting lead, varying according 
 to the ore and the locality. 
 
 Lead is a brilliant metal, bluish-white in color, and so 
 soft as to be easily cut with a knife. It leaves upon paper 
 a bluish-gray streak, and is very malleable. It has a spe- 
 cific gravity of 11*37, crystallizes in regular octahedrons, 
 and fuses at 325. At a white heat it may be distilled. It 
 has but a feeble tenacity, a wire two millimeters in diameter 
 sustaining only nine kilograms. A freshly cut surface tar- 
 nishes in ordinary air, but remains bright in perfectly dry 
 air and also in water free from air. Potable waters in gen- 
 eral act upon lead, dissolving it, and partly precipitating it 
 as carbonate. This action is particularly noticeable in well- 
 waters which contain nitrates from decomposed animal mat- 
 ter, or chlorides from saline infiltration. Lead water-pipes 
 should therefore be avoided or used with great caution. When 
 melted in the air, lead is rapidly converted into the oxide. 
 It is scarcely attacked by sulphuric or hydrochloric acid at 
 ordinary temperatures, but dissolves readily in nitric acid. 
 In presence of air and moisture it is acted upon by quite 
 feeble acids, as acetic and carbonic. Hence the use of such 
 vessels as are made of or are united with lead, or lead solder, 
 
PROPERTIES OF LEAD. 269 
 
 should be avoided for such articles. Lead, when taken into 
 the system, unites definitely with certain tissues and is re- 
 tained there, until finally sufficient accumulates to produce 
 poisoning. Acute colic is characteristic of poisoning by a 
 large dose of lead ; but in chronic poisoning, which is far 
 more common, there is paralysis, particularly of the muscles 
 of the forearm, causing the wrists to drop; or there may 
 be simply an indefinable feeling of malaise, accompanied by 
 dyspeptic symptoms. 
 
 Lead is used extensively in the arts for various purposes, 
 both alone and alloyed with other metals. With a small 
 proportion of arsenic it forms the alloy of which shot are 
 made ; with antimony and tin, it forms type-metal ; with bis- 
 muth, the soft alloy used for permanent pencil-points ; with 
 tin, pewter and soft solder ; and with cadmium, tin, and bis- 
 muth, fusible metal melting at 60. 
 
 EXPERIMENT. Metallic lead in a state of fine division takes fire 
 readily in the air, forming what is known as pyrophorus. To obtain 
 it in this form, tartrate of lead is produced by adding lead acetate to 
 a solution of potassio-sodium tartrate rochelle salt so long as it 
 forms a precipitate. The lead tartrate, filtered off, washed, and dried, 
 is placed in a tube of hard glass, the tube is then drawn out at the 
 end, and the whole is heated to a bright redness, until no more fumes 
 escape. The end of the tube is then sealed, and the whole allowed 
 to cool. On breaking the tube and pouring out the contents into the 
 air, the metallic lead at once inflames, producing a shower of fire. In 
 oxygen the combustion is brilliant; in carbon di-oxide no combustion 
 takes place. 
 
 LEAD AND CHLORINE. 
 
 360. Plumbic Chloride. Form ula Pb"Cl,. This chlo- 
 ride has been found in the crater of Vesuvius after an erup- 
 tion, and is known as cotunnite. It is precipitated from any 
 plumbic solution, if sufficiently concentrated, upon the addi- 
 tion of hydrochloric acid or a chloride. It is a heavy white 
 powder, soluble in 135 parts of cold and 30 parts of boiling 
 water, from which it crystallizes, on cooling, in lustrous nee- 
 
270 INORGANIC CHEMISTRY. 
 
 dies. It melts when heated in close vessels, and at a higher 
 temperature sublimes. The fused chloride is translucent and 
 sectile, and is known as horn-lead. A white and a yellow 
 oxy-chloride are used as pigments. 
 
 361. Plumbic Per-chloride. Formula Pb lv Cl 4 . Plum- 
 bic per-chloride is obtained in solution by dissolving plumbic 
 peroxide in cold hydrochloric acid, and in crystals by evap- 
 orating this solution in vacuo. It has been but little studied. 
 
 LEAD AND OXYGEN. 
 
 362. Plumbic Peroxide. Formula Pb lv O 2 . Plumbic 
 peroxide is best prepared by precipitating a solution of four 
 parts of lead acetate with a solution of three and a half 
 parts of crystallized sodium carbonate, and passing chlorine 
 gas through the mixture until the whole of the white car- 
 bonate of lead is converted into the brown peroxide. It 
 forms on drying a chocolate-brown or puce-colored powder, 
 which gives off oxygen on heating. It is a strongly oxidiz- 
 ing agent, uniting directly with sulphurous oxide to form 
 plumbic sulphate. .Digested with ammonic hydrate, it forms 
 water and lead nitrate ; mixed with one fifth its weight of 
 sulphur, it inflames spontaneously ; rubbed in a mortar with 
 one sixth of grape-sugar ignition takes place ; it sets iodine 
 free from potassium iodide, and bleaches a solution of sulph- 
 indigotic acid. 
 
 Plumbic peroxide combines directly with the oxides of po- 
 tassium, sodium, calcium, and even lead, forming salts called 
 plumbates, having the general formula M,PbO.,. Potassium 
 plumbate occurs in white "octahedrons, decomposable by wa- 
 ter. Plumbic plumbates form the various compounds know T n 
 as red-leads. The compound Pb". 2 Pb lv O 4 , or plumbic ortho- 
 plumbate, written more often Pb. ? O 4 , occurs native as min- 
 ium. This, as well as the meta-plumbate Pb"Pb lv O,, or Pb. 2 O,, 
 is produced largely in the arts as a pigment, by oxidizing 
 litharge in a current of air, and then cooling very slowly. 
 
PLUMBIC OXWK JA7) HYDUATE. 271 
 
 Nitric acid decomposes these plumbates, producing lead ni- 
 trate and plumbic peroxide. The same result is produced 
 by much weaker acids, such, for example, as acetic acid. 
 
 363. Plumbic Oxide. Formula Pb"O. This oxide of 
 lead occurs native as the mineral massicot. It is prepared 
 on the large scale in the arts under the name of litharge, by 
 heating melted lead in a current of air. Its color is pale- 
 yellow, or orange-yellow, according to the temperature at 
 which it is produced. It is dimorphous, crystallizing in 
 rhombic octahedrons and in regular dodecahedrons. Its spe- 
 cific gravity is 9*42, and infuses at a full red heat. It is 
 soluble only in 7,000 parts of water, but acids dissolve it 
 easily, forming definite salts. It is also soluble in alkali- 
 hydrate solutions, and in lime-water. It is used in the arts 
 in the manufacture of glass. 
 
 Plumbic hydrate, H.,PbO., or Pb"(OH) 2 , is known only as 
 a colorless, sweetish, alkaline liquid, obtained by the action 
 upon lead of water and air, free from carbon di-oxide. The 
 precipitate produced by hydrates of the alkalies in plumbic 
 solutions is an oxy-hydrate having the composition Pb 2 O 
 (OH),. 
 
 Plumbic nitrate, Pb"(NO 3 ) 2 , is produced by dissolving 
 lead or its oxide in nitric acid and crystallizing. The hy- 
 
 ( 
 dro-nitrate H(NO 2 )'PbO 2 or Pb j \ is precipitated 
 
 from the nitrate by adding ammonium hydrate in small 
 quantity. Plumbic carbonate, PbCO 3 , occurs native as 
 cerussite; a hydro - carbonate, Fb 8 (COg),(OH) t , is much 
 used as a pigment under the name of white-lead. Plumbic 
 sulphate, PbSO 4 , which occurs native as anglesite, is pre- 
 cipitated from solutions of lead on adding sulphuric acid or 
 soluble sulphates. 
 
 364. Plumbous Oxide. Formula Pb 2 O. When lead 
 oxalate is heated to 300 in a closed vessel, a black velvety 
 powder is obtained, which is plumbous oxide. It contains 
 
272 INORGANIC CHEMISTRY. 
 
 no metallic lead and no plumbic oxide ; but takes fire when 
 heated in the air, producing this oxide. 
 
 RELATIONS OF THE GROUP. 
 
 365. This group includes germanium, tin, and lead. Ger- 
 manium was discovered in 1886 by Winkler, in a Freiberg 
 silver-ore, and is remarkable as being one of the three ele- 
 ments whose properties were predicted by Mendeleeff by the 
 aid of the periodic law. It is extremely rare. The members 
 of the group are closely allied, and show a distinct grada- 
 tion of properties as the atomic mass increases, germanium 
 being the most strongly electro-negative and lead the most 
 strongly electro-positive. They all form halogen compounds 
 of the types MX 2 and MX 4 , and oxygen and sulphur com- 
 pounds of the types MO and MS, MO, and MS, ; the latter 
 acting negatively and forming salts with the alkalies. The 
 hydrates of germanium ancf tin act as weak acids. 
 
EXERCISES. 273 
 
 EXERCISES. 
 
 1. How does tin occur in nature ? How is it obtained ? 
 
 2. What mass of " tin salts " will 250 kilograms of tin yield ? 
 
 3. What volume of chlorine is contained in a gram of stannous 
 chloride? Of stannic chloride? 
 
 4. To give a kilogram of stannic sulphide requires what mass of 
 tin? 
 
 2. 
 
 5. Mention the minerals in which lead occurs. 
 
 6. Write the chemical reactions which take place in obtaining 
 lead from galenite. 
 
 7. 1,000 kilograms of galenite yield what volume of SO 2 ? 
 
 8. What mass of metallic lead would be obtained? 
 
 9. Calculate the volume occupied by a kilogram of lead. 
 
 10. What are the objections to the use of lead water-pipes? 
 
 11. How is a lead pyrophorus prepared ? 
 
 12. What volume of chlorine is contained in the plumbic chloride 
 required to saturate a liter of water? 
 
 13. What mass of sulphur may be burned by one gram of lead di- 
 oxide? Write the reaction. 
 
 14. Give the rational constitution of the red-leads. 
 
 15. One cubic decimeter of lead will give what mass of litharge? 
 
 16. How many kilograms of white-lead can be obtained from 1,000 
 kilograms of lead ? 
 
 
274 INORGANIC CHEMISTRY. 
 
 CHAPTER EIGHTH. 
 
 THE PLATINUM GKOUP. 
 $5 1. PLATINUM. 
 
 Symbol Pt. Atomic mass 194*3. Valence II and IV. 
 
 366. History and Occurrence. Platinum was brought 
 to Europe from South America in 1735 by Ulloa, and in 
 1741 by Wood. It was first described by Watson in 1750, 
 and independently by Scheffer in 1752. It derives its name 
 from the word platina, the Spanish diminutive of plata, silver. 
 It occurs native usually in rounded grains, though sometimes 
 it is found crystallized in octahedrons. It is rarely pure, the 
 native platinum containing gold, iron, and copper, besides 
 iridium, ruthenium, osmium, rhodium, and palladium, its 
 natural congeners. It occurs not only in South America, 
 but also in Russia, in Borneo, and in California. 
 
 367. Preparation and Properties. Native platinum 
 was formerly purified by the method of Wollaston, which 
 consists in treating the crude metal first with nitric acid 
 and then with hydrochloric acid, and afterward with boiling- 
 aqua regia. By the latter treatment, the platinum, palla- 
 dium, and a portion of the rhodium are dissolved, while a 
 mixture of iridium, rhodium, osmium, and ruthenium, known 
 as iridosmine, is left. The platinum is thrown down from 
 its solution by ammonium chloride, as ammonium chloro- 
 platinate. This, on ignition, leaves the metal in a finely- 
 divided state known as spongy platinum, which is con- 
 densed into a cake by powerful pressure, and is then welded 
 at a white heat into a homogeneous mass. 
 
PROPERTIES OF PLATINUM. 
 
 275 
 
 Latterly, however, Deville's method has almost entirely 
 superseded that of Wollaston. In this the crude platinum 
 is melted with an equal weight of lead sulphide and half 
 its weight of metallic lead ; in this way the platinum is dis- 
 solved, leaving the iridosmine. The platinum-lead alloy is 
 then melted and exposed to a current of air, by which the 
 lead is oxidized, the oxide flowing off as slag, and the plati- 
 num being left as a porous mass. This is then placed in 
 a furnace made of lime (Fig. 
 98), and by means of two 
 powerful oxy-hydrogen jets, it 
 is melted and cast into ingots. 
 Masses weighing 100 kilo- 
 grams have been produced 
 by this process at one fusion. 
 The melted mass absorbs oxy- 
 gen, and evolves it again on 
 cooling, like silver. 
 
 Platinum is a brilliant white 
 metal, with a tinge of blue. It has a specific gravity of 
 21-5, is extremely malleable and ductile, and has a tenacity 
 and hardness resembling that of copper. It is an imperfect 
 conductor of heat and of electricity, and is infusible by ordi- 
 nary means, but yields to the oxy-hydrogen flame (1775 ), 
 in which it is partially volatilized. ' Before complete fusion 
 it softens, and may then be welded. At high temperatures 
 it absorbs hydrogen, and is readily permeable by this gas at 
 a red heat. Platinum is unaltered in the air at any tem- 
 perature ; it is not attacked by any single acid, being dis- 
 solved only by aqua regia. Fused potassium and sodium 
 hydroxides act upon it ; and it combines directly with sul- 
 phur, phosphorus, arsenic, and silicon. 
 
 Platinum possesses in a remarkable degree the property 
 of condensing gases upon its surface. In the form of plati- 
 num-foil, it will cause the explosion of mixed oxygen and 
 
 Fig. 98. Platinum Furnace. 
 
276 INORGANIC CHEMISTRY. 
 
 hydrogen gases; but in the form of platinum-sponge it is 
 much more active ; and in the still more finely divided form 
 known as platinum black, it is capable of absorbing 800 
 times its volume of oxygen. Platinum black, therefore, 
 owing to this condensed oxygen, is an energetic oxidizing 
 agent ; alcohol thrown upon it is at once inflamed. From 
 recent researches, Berthelot regards platinum black as a sub- 
 oxide. When hydrogen acts on it, it first reduces this oxide 
 and then forms a hydride with the metal. 
 
 Owing to its infusibility and its unalterability by chemical 
 agents, platinum is used extensively both in the arts and in 
 the laboratory for chemical vessels. Large platinum stills for 
 sulphuric acid weigh often 30,000 grams. Platinum has been 
 used in Russia also for coinage. 
 
 COMPOUNDS OF PLATINUM. 
 
 368. Platinum Chlorides. Two chlorides of platinum 
 are known, the platinic chloride, PtCl 4 , and the platinous 
 chloride, PtCL 2 . The former is obtained whenever platinum 
 is dissolved in aqua regia. By evaporation at 100, a brown- 
 red deliquescent mass is left, soluble freely in water, alcohol, 
 and ether. It loses half its chlorine at 230, and the whole 
 at a red heat. It unites directly with alkali chlorides, form- 
 ing chloro - platinates, M 2 PtClg. Platinous chloride is pro- 
 duced by heating platinic chloride to 230, until . chlorine 
 ceases to be evolved. A dark-green powder is left, insoluble 
 in water, sulphuric and nitric acids, but soluble in sodium 
 and potassium hydroxides. A series of remarkable com- 
 pounds is formed by the action of ammonia upon this chlo- 
 ride, called the ammonio-platinum bases. 
 
 369* Platinic Oxide, PtO 2 , forms a hydrate Pt lv (OH) 4 , 
 which dissolves in alkali-hydrates, yielding platinites. Pla- 
 tinous oxide, PtO, yields a basic hydrate Pt"(OH) 2 , which 
 forms salts with acids. Platinous and platinic sulphides 
 are also known. 
 
RELATIONS OF THE PLATINUM GROUP. 277 
 
 RELATIONS OF THE GROUP. 
 
 37O. The platinum metals, so called, are commonly di- 
 vided into two sub-groups, according to the periodic law. 
 Sub-group A contains osmium, iridium, and platinum, and 
 sub-group B, ruthenium, rhodium, and palladium. The mem- 
 bers of these sub-groups are closely related : 
 
 SUB-GROUP A. SUB-GROUP B. 
 
 0.5 Ir Pt Ru Ro Pd 
 
 At. ms. 191-0 192-5 194-3 103-5 104-1 106-2 
 
 Sp. gr. 22-48 22-42 21-50 12-20 12-1 11-5 
 
 the atomic masses and specific gravities being nearly the 
 same for each sub-group. Ruthenium and osmium are more 
 strongly negative, palladium and platinum more strongly 
 positive. 
 
 EXERCISES. 
 
 1. With what other elements is platinum associated? 
 
 2. By what two methods is it refined? 
 
 3. An alloy of platinum and gold has a specific gravity of 20; 
 what per cent of platinum does it contain? 
 
 4. What remarkable property has finely-divided platinum? 
 
 5. What pressure would condense oxygen as it is condensed by 
 platinum black? 
 
 6. One gram of PtCl 4 contains what volume of chlorine? 
 
 I'.i 
 
 
278 INORGANIC CHEMISTRY. 
 
 CHAPTER NINTH. 
 
 THE IKON GROUP. 
 ( SUB-GROUP A.) 
 
 CHROMIUM. 
 Symbol Cr. Atomic imi#* 52 -4"). Valence II, III, and VI. 
 
 371. History and Occurrence. Chromium was first 
 recognized as a distinct substance by Vauquelin in 1797, in 
 a native lead chromate from Siberia. Its name comes from 
 Zl)a)tj.a, color, because most of its compounds are brilliantly 
 colored. It occurs in nature in the mineral chromite, or 
 chrome-iron, a ferroso-chromic oxide ; also as lead chromate 
 in the mineral crocoite. It forms the coloring matter of the 
 emerald, and has been found in meteoric irons. 
 
 372. Preparation and Properties. Chromium is pre- 
 pared by reducing its oxide by charcoal ; or better, by re- 
 ducing the chloride by zinc or magnesium. By the former 
 method, it is obtained as a steel-gray mass, highly infusible 
 aud extremely hard ; by the latter, as a gray-green, glisten- 
 ing powder, composed of minute tetragonal octahedrons, of 
 specific gravity 6 '8. It is unaltered when heated in dry air, 
 but burns in oxygen. It is not magnetic. 
 
 CHROMIUM AND CHLORINE. 
 
 373. Chromic Chloride. Formula CrCL. Chromic 
 chloride is obtained by passing chlorine gas over ignited 
 pellets of chromic oxide and lamp-black. A sublimate of 
 micaceous scales, beautiful peach-blossom in color, and of an 
 unctuous feel, is thus produced, which is insoluble in water 
 
COMPOUXDS OF CHEOMIUM. 279 
 
 unless a trace of chromous chloride is present ; then it dis- 
 solves readily. It is unaltered by ordinary re-agents. On 
 prolonged boiling with water it dissolves, forming a green 
 solution, containing a hydrate. A soluble violet modifica- 
 tion is produced by heating the green hydrate in a current 
 of hydrochloric acid gas. Its solution becomes green on 
 boiling. The chlorine of the violet solution is completely 
 precipitated by silver nitrate ; that of the green solution but 
 partially. 
 
 374. Chromous Chloride. Formula CrCl. 2 . Chromous 
 chloride is prepared by reducing chromic chloride by hydro- 
 gen at a gentle heat. It is a white, crystalline substance, 
 soluble in water, forming a blue solution, which by absorp- 
 tion of oxygen rapidly becomes green. 
 
 375. Chromic Per-fiuoride. Formula CrF 6 . Chromic 
 per-fluoride is obtained by distilling lead chromate with cal- 
 cium fluoride (fluor spar) and sulphuric acid : 
 
 PbS0 4 + (CaS0 4 ) 8 + (H,0),+ CrF. 
 
 An orange vapor is evolved, which condenses to a blood-red 
 liquid, boiling at a temperature but little above that of the 
 air, fuming in contact with moist air, and decomposed by 
 water, forming hydrofluoric and chromic acids. 
 
 CHROMIUM AND OXYGEN. 
 
 376. Chromic Tri-oxide. Formula Cr vl O 3 . Chromic 
 tri-oxide is obtained by mixing a saturated solution of potas- 
 sium di-chromate with its own volume of strong sulphuric 
 acid. On cooling, splendid crimson needles of the tri-oxide 
 crystallize out, which may be dried on a porous tile. It is 
 deliquescent in damp air, and is decomposed by a heat of 
 250. It is a powerful oxidizing agent ; alcohol poured on 
 it is at once inflamed, and ammonia gas reduces it with 
 incandescence. 
 
280 IXORGAXIC CHEMISTRY. 
 
 377. Chromic Acid. /'//// <//</ H,CrO 4 . By solution 
 of chromium tri-oxide in water, an acid liquid is obtained 
 which contains chromic acid, but which is decomposed on 
 evaporation, yielding only chromic tri-oxide again. The salts 
 of chromic acid, called chromates, are numerous and impor- 
 tant. The ortho-chromates of bismuth, B'",CrO 6 , and of mer- 
 cury, Hg" 3 CrO 6 , the mono-meta-chromate of lead, Pb" a CrO 5 , 
 the di-meta-chromates of sodium, Na,CrO 4 , and of barium, 
 Ba"CrO 4 , and the di-chromate of potassium, K,Cr,O T , are all 
 well-known compounds. Potassium di-chromate is used in 
 dyeing and in calico-printing. 
 
 378. Perchromic A.cifi..Fonnula H,l'r,O,. ^). By the 
 action of hydrogen peroxide upon an acid solution of pota>- 
 sium chromate, a bright blue liquid is obtained which evolves 
 oxygen with effervescence, and becomes green. By agitation 
 with ether, the blue substance is dissolved ; and on standing, 
 it forms a bright blue layer upon the surface of the liquid. 
 This reaction is a delicate test for hydrogen peroxide or for 
 a chromate. 
 
 379. Chromic Oxide. Formula Cr 2 O 3 . Chromic oxide 
 may be produced by igniting its hydrate, or by decomposing 
 the tri-oxide or a di-chromate by combustibles. By passing 
 chromyl chloride vapor through a red-hot tube, rhombohe- 
 dral crystals of chromic oxide are obtained, greenish-black 
 in color, having a specific gravity of 5 -21, and hard enough 
 to scratch glass. It is generally produced in the form of an 
 amorphous bright green powder, which after ignition is in- 
 soluble in acids. It is used to color bank-notes green. 
 
 Chromic oxide may act as a positive or a negative oxide, 
 according to the oxide with which it unites. With the 
 strongly negative sulphuric oxide, for example, it forms 
 chromium sulphate, Cr,(SO 4 ), ; while with calcium or mag- 
 nesium oxide, compounds called calcium or magnesium chro- 
 mites, CaCr.,O 4 , or MgCf k O|, are obtained. The best known 
 of these is FeCr.O,, ferrous chromite, or native chromic 
 
OCCURHK\CK OF MA\(i AXKSE. 281 
 
 iron. Chromium sulphate exists in solution in two different 
 modifications, one green, the other violet; with potassium 
 sulphate the latter yields a double sulphate, which, crystal- 
 lizing in violet-red regular octahedrons with twelve molecules 
 of water, is known as potassio-chromium alum, KCr(SO 4 ). 2 , 
 12 aq. Ortho-chromic hydrate, H 3 CrO 3 , 2 aq., is precipitated 
 by ammonium hydrate from boiling solutions of chromic- 
 salts ; and an intermediate di-chromic hydrate, H 4 Cr 2 O., is 
 used as a pigment under the name of Pannetier's green. 
 
 380. Chromous Oxide. Formula Cr"O. Chromous 
 oxide is known only in the form of hydrate, produced by 
 precipitating chromous chloride by potassium hydrate. It 
 acts as a basic oxide, yielding chromous salts. 
 
 381. Cliroinyl Chloride. Formula (CrO 2 )"Cl r Chro- 
 myl chloride is prepared by distilling a mixture of sodium 
 chloride and potassium di-chromate with sulphuric acid. It 
 is a blood-red liquid, having a specific gravity of I'll, and 
 boiling at 118. Its relation to the chromates is as follows: 
 
 r n 1 OH r o f OH rvn 1 OK rvn I C1 r n J C1 
 CrO,| OH Cr0 2 | OK CrO, j OR CrO 2 j QK CrO 2 
 
 Hydro-potcuffatvt Potassium Potassium Chromyl 
 
 Chromate. ' eliminate. chromate. chloro-chromate. chloride. 
 
 Potassium chloro-chromate crystallizes from a hot solution 
 of potassium di-chromate in hydrochloric acid, on cooling. 
 
 ( SUB-GROUP B.) 
 MANGANESE. 
 
 Symbol Mn. Atomic mass 54*8. Valence U, III, IV, VI, and 
 
 VII. 
 
 382. History and Occurrence. Manganese was dis- 
 covered by Scheele and Berg-mann in 1774, in a mineral 
 known as braunstein. Owing to its being confounded with 
 magnetic iron, this mineral had received the Latin name 
 of this substance, magnesia nigra ; whence the name mag- 
 
282 l\()h'<;.L\/< CHEMISTRY. 
 
 nesium first given to the new metal obtained from it. This 
 name was afterward changed to manganesium, to distinguish 
 it from the true magnesium, obtained from the magnesia 
 alba. Manganese occurs somewhat abundantly in nature, 
 combined principally with oxygen. The mineral pyrolusite 
 is manganese di-oxide ; hausmannite is manganoso-manganic 
 oxide ; and manganite is manganic hydrate. Manganese sul- 
 phide, arsenide, carbonate, and silicate are also known as 
 minerals. 
 
 383. Preparation and Properties. Manganese is ob- 
 tained by reducing its oxide by charcoal at a high tempera- 
 ture. It is a grayish-white, hard metal, resembling cast iron, 
 and very brittle. It is feebly magnetic and has a specific 
 gravity of 8. It oxidizes readily in the air, and dissolves 
 easily in acids. It forms a remarkably beautiful alloy with 
 copper, and it is largely used in the Bessemer steel process, 
 in the form of a rich alloy with iron, called spiegel-eisen. 
 
 MANGANESE AND CHLORINE. 
 
 384. Manganic Chloride. Formula MnCl. { . Man- 
 ganic chloride is a very unstable compound, obtained by 
 dissolving manganic oxide in hydrochloric acid at a low 
 temperature. It is a brown liquid, readily evolving chlo- 
 rine and becoming manganous chloride. 
 
 385. Maiig-anous Chloride. Formula MnCl r Man- 
 ganous chloride, obtained by heating the hydrated com- 
 pound, or by the direct action of chlorine on manganese, is 
 a pale rose-colored deliquescent mass, which dissolves readily 
 in water, forming a definite hydrate. The same hydrate is 
 formed whenever manganese oxide or carbonate is dissolved 
 in hot hydrochloric acid. 
 
 MANGANESE AND OXYGEN. 
 
 386. Manganic Tri-oxide. Formula Mn vl O :r Neither 
 manganic tri-oxide nor its corresponding hydrate, manganic 
 
283 
 
 acid, is knowD in the free state. Their salts, however, called 
 manganates, are well-known compounds. Potassium manga- 
 uate, K 2 MnO,, is produced whenever manganese compounds 
 are heated with potassium hydrate or carbonate. A deep 
 green mass results, which, dissolved in water and evaporated 
 in vacuo, affords dark green crystals, isomorphous with po- 
 tassium sulphate. The manganates are all unstable, passing 
 readily into permanganates and depositing manganese di- 
 oxide. 
 
 387. Permanganic Oxide. Formula Mu 2 O 7 . When 
 sulphuric acid and potassium permanganate are mixed to- 
 gether, previously cooled to a low temperature, a dark-col- 
 ored oily liquid separates which is supposed to have this com- 
 position. It oxidizes and inflames organic substances, and 
 may be converted into violet-colored vapors, which explode 
 when heated rapidly. 
 
 388. Permanganic Acid. Formula HMnO 4 . By treat- 
 ing barium permanganate with sulphuric acid and evaporat- 
 ing the solution in vacuo, permanganic acid is obtained in 
 the form of brown crystals. It is deliquescent, dissolves in 
 water with a red color, and decomposes at 32, evolving 
 oxygen. Its salts, the permanganates, are more stable than 
 the manganates. Potassium permanganate is prepared by 
 removing a portion of the base from the mauganate, by 
 passing through its solution a current of chlorine gas : 
 
 (K 2 Mn0 4 ) 2 + C1 2 = (KC1), + (KMnO 4 ) 2 
 
 The color of the liquid changes from green to purple-red, 
 and on evaporation yields dark purple-red ortho-rhombic 
 crystals, soluble in sixteen times their weight of water, and 
 isomorphous with potassium perchlorate. Permanganates 
 act as strongly oxidizing agents, and are used extensively 
 as disinfectants. 
 
 389. Manganic Oxide. Formula Mn 2 O. r Manganic 
 oxide is produced when manganic hydrate or manganese 
 
284 IXOItd.-lXIC CHKMISTKY. 
 
 di-oxide is heated to low redness. It is a black powder, 
 uniting with strong acids to form salts. Manganic sulphate 
 forms an alum with potassium sulphate, having the formula 
 KMn(SOj 2 , 12 aq. Manganic hydrate, HMnO.,, exists na- 
 tive as the mineral mauganite. 
 
 390. Manganese I>i- oxide. Formula Mu lv O.,. The 
 di-oxide of manganese occurs native as the mineral pyrolu- 
 site, in steel-gray ortho-rhombic prisms, of specific gravity 
 4-9. It is produced whenever a lower oxide is heated with 
 free access of air. When heated it gives off oxygen, and is 
 extensively used in the arts as an oxidizing agent at high 
 temperatures. Heated with sulphuric acid, it evolves oxy- 
 gen and forms manganous sulphate ; with hydrochloric acid 
 it evolves chlorine. With basic oxides, nia.iiirane.se di-oxide 
 forms manganites such as OaMnO, and K. 2 Mu. 2 O 5 . 
 
 391. Manganous Oxide. Formula Mn"O. Manga- 
 nous oxide is obtained by igniting manganous carbonate or 
 oxalate in an atmosphere of hydrogen. It is a grayish-green 
 powder, which has been obtained crystallized in emerald- 
 green regular octahedrons. Its hydrate is thrown down as a 
 white precipitate on adding a solution of potassium hydrate 
 to one of a manganous salt. It quickly becomes brown on 
 exposure to the air. Manganous oxide unites directly with 
 negative oxides to form the manganous salts. Manganous 
 sulphate, MnSO^, manganous carbonate, MnCO.,, and man- 
 ganous silicate, MnSiO,, are examples. They all have a deli- 
 cate pink color. 
 
 ( SUB-GROUP C.) 
 
 1. IRON. 
 Symbol Fe. Atomic mm* 55 '88. Valence II, III, IV, and- VI. 
 
 392. History and Occurrence. Iron is one of the 
 most important, as it is one of the most abundant, of metals. 
 It has been known from the earliest historic times, Tubal 
 
PREP AHA TJOX or i no \ . 285 
 
 Cain being an artificer in this metal. Even in pre-historic 
 times, implements made of it seem to have been used. It is 
 doubtful whether it occurs native ; the native iron found on 
 the earth's surface containing generally nickel, and being 
 of meteoric origin. Its ores, however, are very numerous. 
 Among these may be mentioned : ferroso-ferric oxide or mag- 
 netite, Fe 3 O 4 ; ferric oxide or hematite, Fe.,O 3 ; ferric hy- 
 drate or limonite, H^Fe^; and ferrous carbonate or siderite, 
 FeCO. r It occurs also in numerous other minerals, and in 
 vegetables and animals. 
 
 393. Preparation and Properties. On the large scale 
 in the arts, iron is produced either from the native oxide or 
 from the artificial oxide obtained by roasting the native car- 
 bonate or hydrate. Alternate layers of the ore, of the fuel, 
 and of limestone are placed in an enormous furnace, shaped 
 like a double cone interiorly, and forty to sixty feet in 
 height; whence it is commonly called the "high furnace." 
 A powerful blast of hot air enters at the bottom, and the 
 combustible matter, at the high temperature produced, re- 
 moves the oxygen from the ore, thus reducing it to the me- 
 tallic state, according to the equation : 
 
 FeA -f C, = Fe, + (CO), 
 
 The limestone unites with the silica and other impurities 
 present, forming an easily fusible silicate, which collects 
 above the melted iron and is- drawn off as slag. After the 
 iron is reduced to the metallic state, it takes up more carbon, 
 becomes fusible, melts, and runs down to the bottom of the 
 furnace, accumulating in a narrow cylinder called the cru- 
 cible. When this is full, it is tapped by driving in the clay 
 plug which closes the opening, and the melted iron runs 
 down a suitable channel into molds made in the sand for 
 its reception. The manufacture of cast iron in the high- or 
 blast-furnace is a continuous operation ; the materials are 
 constantly added above, the slag and melted iron are drawn 
 
off from below, usually twice a day ; and this is kept up until 
 the furnace wears out. The iron thus made is known as cast 
 or pig-iron. Three varieties are distinguished ; white pig-iron, 
 which is hard, brittle, and crystalline, uniformly brilliant and 
 white, of specific gravity 7 '5, and readily fusible; gray pig- 
 iron, which is granular in structure, gray in color, very soft, 
 of specific gravity 7*1, and difficult of fusion; and mottled 
 pig-iron, which has intermediate properties, but is stronger 
 than either. The gray iron has generally least carbon, its 
 color being due to a separation of a part of this carbon as 
 graphite during the cooling. Hence the same metal sud- 
 denly cooled, as when "chilled" or cast in iron molds, may 
 be hard and white; and when cooled slowly in sand, be soft 
 and gray. White iron, especially the variety known as spiegel- 
 eisen, which contains manganese, contains nearly () per cent 
 of carbon; gray iron contains from 2 to 5 per cent. 
 
 Iron is refined, or converted into wrought iron, by burn- 
 ing out the carbon and silicon, as well as the impurities sul- 
 phur and phosphorus. This is effected usually by the process 
 called " puddling" or "boiling." The pig-iron is piled up 
 on the floor of a reverberatory furnace, in contact with some 
 of the pure ores. On lighting the fire it melts, and is con- 
 tinually stirred to mix it thoroughly with the oxide. Gradu- 
 ally the carbon and silicon are oxidized, the former escaping 
 as gaseous carbon monoxide, the latter being retained as sili- 
 cate of iron in the slag ; until finally the iron becomes pasty 
 and adheres together in spongy masses. These are collected 
 into balls of 25 to 30 kilograms weight, and compacted, first 
 by working between powerful jaws called squeezers, and then 
 between rollers, by which the slag is pressed out, and the 
 iron is made into "muck bar." The puddled bar is cut into 
 short pieces, made into bundles, heated, and again passed 
 through the rolls ; the operation being repeated until the 
 wrought iron is sufficiently pure. By this process the carbon 
 is reduced to one half of one per cent, sometimes to even 
 
287 
 
 less, and the other foreign matters to mere traces. If the 
 iron retain phosphorus, it is brittle when cold, and is called 
 ' ' cold-short ; " if it contain sulphur, it is brittle when hot, or 
 "red-short." The iron thus obtained is bluish-gray in color, 
 is fibrous in structure, and has a specific gravity of 7 '3 
 to 7-9. 
 
 Pure iron may be prepared from the best commercial vari- 
 eties, piano-forte wire for example, by fusing them with pure 
 iron oxide, beneath a layer of glass, to keep out the air, in a 
 clay crucible. It is brilliant silver-white in color, softer than 
 wrought iron, capable of receiving a high polish, strongly 
 magnetic, of specific gravity 7*8, and crystallizes in the reg- 
 ular system. When obtained by electrolysis its specific grav- 
 ity is 8'1. Iron is also prepared for pharmaceutical uses by 
 reducing its oxide by hydrogen at a red heat. It is then 
 obtained as a black powder, burning when heated in- the air. 
 In its purest commercial form, iron has a tenacity superior 
 to that of any other metal, except nickel and cobalt. Its 
 ductility is also very great, and when heated it may be rolled 
 into sheets scarcely thicker than paper. At a full red heat 
 it becomes pasty like wax, and may then be welded. It melts 
 at a high temperature, probably above 2000. 
 
 Steel is iron which contains from 0'6 to nearly 2'0 per 
 cent of carbon. It is therefore intermediate in this respect 
 between cast and wrought iron. Two methods are in use for 
 making steel. In the one, the wrought-iron bar is heated 
 with charcoal, and thus made to take up again a portion 
 of carbon; in the other, the carbon is burned out from the 
 melted cast iron by a powerful current of air. The former 
 is known as the process of cementation. Fig. 96 represents 
 a cross-section of the furnace in which it is effected. The 
 iron bars are packed in charcoal in the fire-clay chests or 
 boxes shown in the figure, the whole covered with sand to 
 exclude the air, and heated to redness for from seven to ten 
 davs, after which it is allowed to cool down slowlv. The 
 
288 
 
 bars are now brittle, covered with blisters, and are easily 
 fusible. They may be at once piled together, heated, and 
 rolled into bars of " shear-steel ; " or they may be broken in 
 small pieces, melted in crucibles of fire-clay, with the addi- 
 tion of a little manganese di-oxide, and cast into ingots; 
 
 Fig. 9fi. fomentation Furnace. 
 
 these ingots are afterward heated and drawn out under the 
 hammer into bars. In this form it is known as "cast steel." 
 The second steel-process is named the Bessemer process, 
 from its inventor. In it a melted cast iron rich in silicon 
 is run directly into large wrought-iron vessels lined with fire- 
 clay, called converters (Fig. 
 97), where this iron meets 
 with a blast of air blown in 
 under a pressure of two en- 
 tire atmospheres. The silicon 
 in the iron burns vividly, the 
 air at the high temperature 
 produced acting on the car- 
 bon, sulphur, and other impu- 
 rities, to oxidize and remove 
 them. At the end of about twenty minutes the luminous 
 flame suddenly disappears, and a malleable iron containing 
 0'3 to 0*5 per cent of carbon is left melted in the converter. 
 
 Section. Exterior. 
 
 Fig. 97. Bessemer Converter. 
 
BESSEMER STEEL PROCESS. 289 
 
 To this is now added a suitable proportion of white cast iron 
 called technically spiegel-eisen which contains manganese 
 and sufficient carbon to convert the whole into steel. It is 
 then poured into molds, and the ingots thus obtained are 
 hammered or rolled, as before. Formerly, attempts were 
 made to stop the air-blast at the right point ; but the steel 
 thus made varied so widely in quality, that the process above 
 described was substituted. Since the Bessemer process re- 
 moves the sulphur only partially, and the phosphorus not at 
 all, it is evident that a cast iron as free from these impu- 
 rities as possible- must be employed. By simply lining the 
 converter with a mixture of clay, silica, lime, and magnesia, 
 constituting a basic material, Thomas and Gilchrist, in 1880, 
 adapted the Bessemer process to the working of iron con- 
 taining a notable amount of phosphorus. 
 
 Steel resembles iron very closely, being distinguished from 
 it only by the remarkable property it possesses of being ex- 
 tremely hard and brittle when heated and suddenly cooled. 
 By cautious re-heating, the brittleness thus acquired may be 
 diminished, the steel becoming highly elastic ; this process is 
 called tempering. For the manufacture of tools and cutting- 
 instruments, as well as for springs, cementation steel is pre- 
 ferred ; but for many other purposes, as for rails, etc., Bes- 
 semer steel is said to be superior to it. 
 
 Malleable cast iron is produced by heating articles made 
 of ordinary white cast iron to redness for several hours in 
 contact with an iron oxide. A reverse cementation process 
 takes place, by which the carbon is partially removed and 
 the iron becomes semi-malleable. 
 
 IRON AND CHLORINE. 
 
 394. Ferric Chloride. Formula FeCL,. Ferric chlo- 
 ride has been found native, in crevices in active volcanoes. 
 It is prepared by the direct action of chlorine on iron, or by 
 heating its hydrate. A sublimate of iron-black iridescent 
 
290 IXORGAXIC CHEMISTET. 
 
 scales is obtained, which have a metallic luster, and are vola- 
 tile a little above 100, yielding a vapor of density 162'5. 
 Ferric chloride is deliquescent, and dissolves in water with 
 a hissing noise, forming a hydrate. This hydrate is also pro- 
 duced by dissolving iron in hydrochloric acid, heating the 
 solution, and adding nitric acid so long as nitrous gas is 
 evolved. On evaporation, orange-red rhombic crystals are 
 deposited having the composition FeCl 2 , 3 aq. 
 
 395. Ferrous Chloritle. Formula Fed.,. When chlo- 
 rine or hydrogen chloride gas is passed over iron filings in 
 excess, heated to redness, ferrous chloride is obtained in 
 white shining hexagonal scales, which have a specific gravity 
 of 2*5, and are deliquescent in moist air. Ferrous chloride 
 is soluble in two parts of water, and the solution, evaporated 
 and cooled away from the air, deposits bluish-green, mono- 
 clinic crystals, having the composition FeCl 2 , 4 aq. Ferrous, 
 like ferric chloride, forms double salts with alkali-chlorides. 
 
 IRON AND OXYGEX. 
 
 396. Ferric Tri-oxide. Fvnnula Fe vl O.,. Ferric tri- 
 oxide, together with the corresponding ferric acid, are both 
 unknown. Certain salts have, however, been prepared of 
 analogous constitution. Such is potassium ferrate, produced 
 by projecting iron filings, mixed with twice their weight of 
 niter, into a red-hot crucible. On extracting the mass with 
 ice-cold water, a deep cherry-red solution is obtained, which 
 contains potassium ferrate, crystallizing in dark red prisms. 
 It is very unstable, being easily decomposed into oxygen, 
 potassium hydroxide, and ferric oxide. By adding barium 
 chloride to this solution, a purple-red precipitate of barium 
 ferrate is obtained, which is far more stable. It has the 
 composition BaFeO 4 , aq. 
 
 397. Ferric Oxidv. Formula Fe,'"O r This oxide of 
 iron occurs abundantly in nature in two forms : one crys- 
 tallized in rhombohedrons and mirror-like, called specular 
 
OXIDES A XI) HYDRATES or IROX. 291 
 
 iron.; the other columnar or fibrous, sometimes amorphous 
 or oolitic in structure and blood-red in color, whence it is 
 called hematite. Artificially, it may be obtained in rhombo- 
 hedral crystals by igniting the amorphous oxide in a slow 
 current of hydrogen chloride gas ; and as an amorphous pow- 
 der by igniting ferric hydrate or ferrous carbonate or oxalate. 
 This latter variety is used for polishing metals and glass, 
 under the name of rouge, crocus, or colcothar. Its specific 
 gravity is about 5. It is reduced to the metallic state when 
 heated in hydrogen. After ignition it is almost insoluble in 
 acids. 
 
 398. Ferric Hydrates exist also in nature, ortho-ferric 
 hydrate, H.^FeOy, in the mineral limnite, di-ferric hydrate, 
 HjFcjjOg, in xanthosiderite, and meta-ferric hydrate, HFeO.,, 
 in gothite, beside other and intermediate forms. Ortho-ferric 
 hydrate is precipitated, on adding ammonium hydrate to a 
 solution of ferric chloride, as a bulky brownish-red precipi- 
 tate, which loses water upon drying and forms a yellowish- 
 brown powder. Moist ferric hydrate forms the best antidote 
 in cases of arsenical poisoning. It is used also in calico- 
 printing as a mordant and in purifying gas. 
 
 399. Ferroso-ferric Oxide. ^Formula Fe"Fe,'"O 4 . 
 This oxide of iron occurs native as the mineral magnetite, 
 crystallized in regular octahedrons. The same crystalline 
 form is obtained artificially by fusing ferric phosphate with 
 three or four times its weight of sodium sulphate. This oxide 
 in the amorphous form is produced when iron is heated to 
 redness in oxygen or steam. It forms the protecting coating 
 in the processes of Barff and Bower. It is a hard, black, me- 
 tallic-like solid, of specific gravity 5*0, and highly magnetic. 
 It is one of the most valuable of iron ores, containing 72 per 
 cent of this metal. Ferroso-ferric oxide may be regarded as 
 ferrous ferrite, derived from ferric hydrate, HFeO., ; analo- 
 gous to ferrous chromite, Fe"GY./) r Other similar compounds 
 are magnesium ferrite, Mg"Fe 2 O 4 , known as the mineral 
 
292 INOEGAXir CHEMISTRY. 
 
 magnesio-ferrite ; and zinc ferrite, Zn"Fe.,O 4 , or franklinite, 
 in which, however, a part of the zinc is replaced by iron and 
 manganese. Ferroso-ferric hydrate is precipitated by am- 
 monic hydrate from a solution containing ferrous and ferric 
 salts in suitable proportions, as a brownish-black, dense mass, 
 which dries to a brittle, strongly magnetic powder. 
 
 4OO. Ferrous Oxide. Formula Fe"O. Ferrous oxide 
 may be obtained by igniting ferrous oxalate in a close vessel, 
 as a black powder, which takes fire in the air and produces 
 ferric oxide. Ferrous hydrate is precipitated whenever solu- 
 tions of alkali-hydrates are added to solutions of pure ferrous 
 salts, both being free of air. White flocks are thus produced 
 which, dried away from the air, have but a slight greenish 
 tinge, but which on exposure take fire and burn to ferric 
 oxide. It has a strong reducing action. 
 
 Ferrous oxide forms a numerous and important class of 
 salts. United to sulphuric oxide, it forms ferrous sulphate, 
 FeSO 4 , known in commerce as green vitriol or copperas. It 
 is produced on the large scale by exposing ferrous sulphide 
 obtained by roasting ferric di-sulphide, or pyrite to the 
 weather, by which it is oxidized : 
 
 FeS + ((X), = Fe"SO 4 
 It is also the product of the action of sulphuric acid on 
 
 H 2 S0 4 -f Fe = FeS0 4 -f H 2 
 
 By evaporating its solution, pale green monocliuic prisms 
 crystallize out, having the formula FeSO,, 7 aq. The same 
 salt occurs native as the mineral melanterite. The crystals 
 effloresce in dry air, and lose all their water at 300. They 
 are soluble in one and a half parts of water at 15, but are 
 insoluble in alcohol. Both the crystals and their solutions 
 readily oxidize in the air. When heated to redness, previ- 
 ously perfectly dried, it gives off sulphurous and sulphuric 
 oxides, leaving a pure ferric oxide. It is therefore used 
 for preparing the Nordhausen or di- sulphuric acid. It is 
 
XICKEL AND COBALT. 293 
 
 employed in the arts also for dyeing, for tanning, and for 
 making writing-ink. 
 
 Ferrous carbonate, FeC0 3 , occurs native as siderite, or 
 spathic-iron, in obtuse rhombohedrons, light grayish-white in 
 color, and of specific gravity 3 '8. It is throw r n down, on the 
 addition of a soluble carbonate to a solution of a ferrous 
 salt, as a white precipitate, rapidly passing into brown fer- 
 ric hydrate on drying. It is soluble in water containing 
 carbonic acid ; occurring native in this form in chalybeate 
 springs. 
 
 IRON AND SULPHUR. 
 
 401. Ferric Di-sulphide. Formula Fe lv S 2 . This sul- 
 phide of iron occurs native in two forms ; one brass-yellow 
 and isometric, called pyrite ; the other white and orthorhom- 
 bic, called marcasite. Buff suggests for pyrite the formula 
 S=Fe=S, and for marcasite, Fe=S=8. Both varieties, on 
 heating in close vessels, give off sulphur and yield the mag- 
 netic sulphide, Fe 3 S 4 . 
 
 402. Ferrous Sulphide. Formula FeS. Ferrous sul- 
 phide is produced by the direct union of sulphur and iron, 
 as when iron wire burns in sulphur vapor, or when the two 
 substances are melted together in suitable proportions. It 
 is a grayish-yellow solid, with a metallic luster and crystal- 
 line structure, and easily fusible. When finely divided it is 
 oxidized to ferrous sulphate on exposure to the air. With 
 acids it evolves hydrogen sulphide gas. It is precipitated 
 from ferrous solutions by alkaline sulphides, as a hydrate. 
 
 2. NICKEL AND COBALT. 
 
 NICKEL. Symbol Ni. Atomic mass 58*56. Valence II, III, 
 and IV. 
 
 403. History and Occurrence. Nickel is one of the 
 less common metals. It was discovered by Cronstedt in 
 1751, in a copper-colored mineral, to which, having failed 
 
 20 
 
294 1XORGAN1C CHEM1STKY. 
 
 in attempting to extract copper from it, the miners had ap- 
 plied in derision the name kupfernickel. From this mineral 
 the name nickel is derived. Nickel occurs free in nature 
 only in meteoric irons ; in combination it exists in many min- 
 erals, as niccolite (kupfernickel), NiAs; gersdorffite, (NiS)". 2 
 A&jj ullmannite, Ni 2 S 2 (AsSb) 2 ; annabergite, Ni 3 (AsO 4 ) 2 ; zara- 
 tite, NiCO 3 , with nickel hydrate; and rnorenosite, NiSO 4 , 
 7 aq. 
 
 404. Preparation and Properties. Nickel is gener- 
 ally obtained commercially either from kupfernickel or from 
 an artificial arsenide produced in the manufacture of smalt, 
 and known as speiss. These arsenides are roasted to drive 
 off the arsenic, are then dissolved in hydrochloric acid, the 
 antimony, bismuth, copper, etc. precipitated as sulphides and 
 removed, the iron after oxidation precipitated as ferric oxide 
 by ammonia, the ammoniacal solution exposed to the air, 
 and the nickel thrown down by potassium hydroxide. The 
 dried precipitate is formed into cubes one or two centimeters 
 on a side, mixed with pulverized charcoal, and placed in 
 intensely heated fire-clay cylinders. The nickel oxide is re- 
 duced, though not fused ; the small tubes of metallic nickel 
 which are drawn from the bottom of the cylinders being sent 
 in this form into commerce. Nickel is a pure silver-white, 
 ductile and malleable metal, of specific gravity 8 '6. It is 
 exceedingly infusible, and has very great tenacity. It is 
 magnetic, but loses this property at 350. It tarnishes in 
 moist air, oxidizes readily at a red heat, and is dissolved 
 somewhat slowly by acids. It is largely used for making 
 German silver, which is an alloy of nickel with copper and 
 zinc. 
 
 COBALT. Symbol Co. Atomic mats 58*74. Valence II, III, 
 and IV. 
 
 405. History and Occurrence. The property of cer- 
 tain cobalt compounds to color glass blue was known to the 
 
COMPOUNDS OF COBALT. 295 
 
 ancient Greeks and Romans. Its ores were long known to 
 the German miners under the name of cobalt, a term derived 
 from kobold, the evil spirit of the mines, who, as they sup- 
 posed, tantalizingly offered them an ore rich in appearance, 
 but worthless. The metal was first prepared by Brandt in 
 173Sf, and more fully studied by Bergmann in 1780. Co- 
 balt occurs in nature in small quantity in meteorites, but 
 principally in the minerals smaltite or speisscobalt, cobaltite 
 or cobalt-glance, erythrite or cobalt-bloom, and asbolite or 
 earthy cobalt. 
 
 406. Preparation and Properties. Cobalt may be 
 obtained by reducing its oxide obtained from the arnmo- 
 niacal solution mentioned under nickel with charcoal or in 
 a current of hydrogen. It may also be obtained by igniting 
 the oxalate. Cobalt has a steel-gray color, with a tinge of 
 red ; it is hard, has a granular fracture, a specific gravity 
 of 8'7 to 8*9, and is malleable at a red heat. It takes up 
 carbon and becomes fusible in an ordinary furnace. It is 
 more magnetic than nickel, and retains its magnetism per- 
 manently. When massive, its surface becomes tarnished on 
 exposure to moist air. It oxidizes readily at a red heat, and 
 burns in oxygen. Sulphuric and hydrochloric acids dissolve 
 it slowly with the evolution of hydrogen. Nitric acid acts 
 upon it readily. 
 
 407. Compounds of Cobalt. Cobalt forms both cobalt- 
 ous and cobaltic compounds. Of these, cobaltous chloride, 
 CoCl.,, a blue solid which forms a pink hydrate hence used 
 for a sympathetic ink ; cobaltous nitrate, Co"(NO 3 ) 2 , a 
 rose-red salt used as a blow-pipe re-agent ; cobaltous sul- 
 phate, CoSO 4 , a light-red salt crystallizing with seven mole- 
 cules of water, and isomorphous with ferrous sulphate ; and 
 cobaltic oxide, Co./"O 3 , and the remarkable cobaltamines, 
 roseo-, purpureo-, xantho-, and luteo-cobalt, may here be men- 
 tioned. Smalt is an impure cobaltous silicate, made by 
 fusing the roasted ore with potassium carbonate and pulver- 
 
296 lyOUG Ay 1C CH EM IS 77,' ) '. 
 
 ized quartz. A deep blue glass is thus obtained, which is 
 poured into water and thus finely divided, in which state it 
 is sent into commerce as a pigment. Zaffre is a very im- 
 pure oxide of cobalt, prepared by roasting the arsenical ores 
 and mixing the product with twice its weight of sand. It is 
 used for coloring glass blue. Thenard's blue is made* by 
 igniting alumina and cobalt phosphate in a covered cruci- 
 ble. Rinrnan's green is produced by treating mixed zinc 
 and cobaltous oxides in the same way. Both are used as 
 pigments. 
 
 RELATIONS OF THE GROUP. 
 
 4O8. The periodic law requires the metals of this group 
 to be arranged in three distinct sub-groups. In the first is 
 placed chromium, molybdenum, tungsten, and uranium. In 
 the second is placed manganese, and in the third is placed 
 iron, nickel, and cobalt. The elements of the first sub-group 
 have a striking resemblance in properties to those of the sul- 
 phur group, the acid oxides CrO s , MoO 3 , WO.,, and UO, cor- 
 responding to SO 3 , SeO 3 , and TeO 3 ; their salts in many cases 
 being isomorphous. In the second group manganese resem- 
 bles the chlorine group, Mn.,O. and HMnO^ corresponding to 
 C1. 2 O 7 and H(J1O 4 , the permanganates being isomorphous with 
 the perchlorates. On the other hand, both chromium and 
 manganese show strong affinities with the iron sub-group, 
 especially on their basic side ; the acidic character being most 
 strongly developed in chromium, the basic character in iron. 
 Moreover, in the entire group there is an odd valence, the 
 valence in general being even. The vapor-density on the 
 whole does, not sustain the doubled formula M..C1,.. 
 
EXERCISES. 297 
 
 EXERCISES. . 
 1. 
 
 1. How does chromium occur in nature? Why is it so called? 
 
 2. What valences has it in its oxides? Its chlorides? 
 
 3. Write the graphic formula of mercuric ortho-chromate. Of 
 lead mono-meta-chromate. Of barium di-meta-chromate. Of potas- 
 sium di-chromate. , 
 
 4. By the following reaction 
 
 K. 2 Cr,0. + C 2 = Cr 2 3 + K 2 CO 3 + CO 
 how much Cr 2 3 will a kilogram of K. 2 Cr.,O 7 yield ? 
 
 2. 
 
 5. Write the reaction in preparing manganese. 
 
 6. What mass of potassium permanganate may be obtained from 
 a kilogram of Mn0. 2 , the reaction being: 
 
 (MnO 2 ) 2 + O 3 -f K,O = (KMn0 4 ) 2 ? 
 
 7. Calculate the percentage composition of manganous silicate. 
 
 8. What per cent of iron do the four ores mentioned contain? 
 
 9. How is cast iron obtained ? What are its varieties ? 
 
 10. What is the mass of a cubic dekameter of gray iron? 
 
 11. What are the chemical changes in the refining of iron? 
 
 12. Give the chemistry of the two processes for steel. 
 
 13. In what do cast iron, wrought iron, and steel differ? 
 
 14. 250 grams pure iron are burned in an excess of chlorine. What 
 compound is formed? What mass of it? 
 
 15. Answer the above questions, using oxygen in place of chlorine. 
 
 16. What percentage of water is there .in the mineral gothite? 
 
 17. 1,000 kilograms pyrite are roasted and exposed to the weather; 
 what mass of crystallized ferrous sulphate may be obtained by its 
 oxidation? 
 
 18. One cubic centimeter of spathic iron contains what volume of 
 
298 INORGANIC CHEMISTRY. 
 
 4. 
 
 19. What percentage of nickel does iiiccolite contain? 
 
 20. An iron vessel weighs 156 grams; what will be its mass if made 
 of nickel ? 
 
 21. By what chemical process is nickel obtained? 
 
 22. The mass of a cube of cobalt is 50 grams; what does it measure 
 on a side? 
 
 23. What mass of cobaltous oxide is required to yield 36 grains of 
 cobaltous nitrate? Of crystallized sulphate? 
 
COPPER, SILVER, GOLD. 299 
 
 CHAPTER TENTH. 
 COPPER, SILVEK, GOLD. 
 
 1. COPPER. 
 Symbol Cu. Atomic mass 63*4. Valence I and II. 
 
 409. History and Occurrence. Copper has been 
 known from the earliest times. The Romans obtained it 
 from the island of Cyprus, and called it aes cyprium, a 
 term which afterward became cuprum, from which the Eng- 
 lish word copper is derived. Copper is found abundantly in 
 nature both free and in combination. Native copper occurs 
 in masses of great size near Kewenaw Point, Lake Superior, 
 one of which weighed over 400 tons. The workable ores 
 of copper are the oxides cuprite and melaconite ; the sul- 
 phides chalcocite, covellite, bornite, and chalcopyrite ; the 
 sulph-antimonite tetrahedrite, and the carbonates malachite 
 and azurite. 
 
 410. Preparation and Properties. The method ap- 
 plied for the extraction of copper varies w r ith the ore under 
 treatment. The oxides and carbonates are simply heated 
 with charcoal or other fuel, with the. addition of some silice- 
 ous flux. The sulphides which contain iron are first roasted, 
 by which the iron sulphide becomes oxide, and some copper 
 oxide is produced. The mass is then fused with silica, thus 
 forming a slag containing the iron as silicate, while a purer 
 copper sulphide is left. By repeating this roasting and the 
 subsequent fusion several times, a nearly pure copper sul- 
 phide is obtained. This is again roasted, the copper oxide 
 
300 L\OH(^ t XI< ' ( 'JIKMISTR V. 
 
 now produced acting upon the copper sulphide to give me- 
 tallic copper, thus : 
 
 Cu 2 S + (CuO) 2 = SO, + Cu 4 
 
 The metal is refined by being kept melted for many hours 
 with free access of air. The more oxidable metals, together 
 with some copper, pass into the slag as oxides, while some 
 of the copper oxide dissolves in the melted metal. To re- 
 move this, it is stirred with the trunk of a young tree, by 
 which this oxide is reduced, the copper becoming at the 
 same time tough and fibrous. If this "poling" be continued 
 too long, the metal is made brittle again. Perfectly pure 
 copper may be obtained by electro-deposition, or by reducing 
 the oxide by a current of hydrogen gas. 
 
 Copper is a lustrous metal, flesh-red in color, and some- 
 what softer than iron. It crystallizes in isometric forms, 
 has a specific gravity of 8*95, and conducts heat and elec- 
 tricity readily. It may be drawn into fine wire or beaten 
 into thin leaves. Its tenacity is considerable, a wire two mil- 
 limeters in diameter sustaining a weight of 140 kilograms. 
 It melts at about 1054, and is volatile at a very high tem- 
 perature. It is unaltered in ordinary air when massive, 
 though when finely divided it often takes fire spontaneously. 
 When heated to redness, scales of oxide form on its surface. 
 It is attacked readily by chlorine and sulphur and by nitric 
 acid. Weak acids and alkalies and saline solutions act on 
 it slowly in presence of the air; hence, as all its salts are 
 poisonous, any thing to be taken as food should not be pre- 
 pared in vessels made of this metal or any of its alloys. 
 
 Copper finds extensive use in the arts, both as such and 
 in the form of alloys. The alloys of copper with tin and 
 aluminum have been mentioned. With zinc it forms the 
 well-know T n alloy brass, of which yellow- or sheathing-metal 
 and aich-metal are varieties. Sterro-metal is a brass con- 
 taining nearly one per cent of tin and two per cent of iron. 
 
or cor PER. 301 
 
 German silver is an alloy of copper, zinc, and nickel. Phos- 
 phorus bronze is an alloy of copper and tin containing nearly 
 one per cent of phosphorus, which increases its hardness and 
 strength. Silicon bronze contains silicon in place of phos- 
 phorus. 
 
 COMPOUNDS OF COPPER. 
 
 411. Cvipric Chloride, Cud,,, is obtained by the action 
 of chlorine upon copper, or by drying its hydrate at 200. 
 It is a yellowish-brown deliquescent powder, soluble in water, 
 forming a green solution which on evaporation deposits crys- 
 tals of the hydrate, CuCl 2 , 2 aq. It forms double salts w y ith 
 
 the alkali-chlorides. Cuprous chloride, Cu 2 01 2 , or p p,, 
 
 is formed by the action of metallic copper upon cupric chlo- 
 ride. On pouring the solution thus obtained into water, a 
 dense white crystalline precipitate is thrown down, which 
 becomes blue on exposure to air, and is fusible at a red heat. 
 Its vapor-density corresponds to the formula Cu 2 Cl 2 . It also 
 forms double salts with the chlorides of the alkali-metals. 
 A cuprous hydride, CuH, is known. 
 
 412. Cupric Oxide, CuO, occurs native as melaconite. 
 It may be prepared by heating the metal in the air, or by 
 calcining the hydrate, carbonate, or nitrate. It occurs in 
 isometric forms perhaps also in orthorhombic but is gen- 
 erally massive. Its specific gravity is 6 "3, and it fuses with- 
 out change at a bright-red heat. It is easily reduced when 
 heated with combustible substances, and hence is used in 
 organic analysis. Cupric hydrate, Cu(OH) 2 , is thrown 
 down as a pale blue precipitate on adding sodium hydrate 
 to a cold solution of cupric salt. It acts strongly basic, and 
 forms numerous salts. Cupric nitrate, Cu(NO 3 ) 2 , is pro- 
 duced w r hen copper is dissolved in nitric acid. On evapora- 
 tion, bright blue crystals separate, which have the formula 
 Cu(NO 3 ) 2 , 3 aq. Cupric sulphate, CuSO 4 , commonly known 
 as blue vitriol, is obtained by dissolving the oxide, carbonate, 
 
302 INOEGANIC CHEMISTRY. 
 
 or hydrate in sulphuric acid, or by roasting the sulphide. It 
 crystallizes with five molecules of water in triclinic prisms, 
 which are soluble in three and one half times their weight 
 of cold water. Cupric ortho-phosphate, liCu 2 PO 5 , occurs 
 native as the mineral libethenite. Two cupric ortho-car- 
 bonates occur native : malachite, which is green, Cu. 2 CO 4 , 
 aq., and azurite, which is blue, JI 2 Cu 3 (CO 4 ) 2 . Cuprous ox- 
 ide, Cu, 2 O, forms the mineral cuprite. It is obtained by 
 reducing a solution of copper with grape-sugar in presence 
 of an alkali-hydrate. It is a bright red powder, isometric in 
 its natural forms, and of specific gravity 6'0. Acids decom- 
 pose it into cupric oxide and copper. 
 
 413. Cupric Sulphide, CuS, is found native as the min- 
 eral covellite. It is hexagonal in its crystallization, is of a 
 bluish-black color, and has a specific gravity of 4 '6. It is 
 precipitated from cupric solutions by hydrogen sulphide. 
 Cuprous sulphide, Cu 2 S, also occurs native, forming the 
 mineral chalcocite. It is produced abundantly in smelting 
 copper. It crystallizes in orthorhombic prisms, is blackish 
 lead-gray in color, and is easily fusible. It acts as a sulphur 
 base, forming cuprous sulph-arseuites and autimonites. 
 
 2. SILVER. 
 Symbol Ag. Atomic mass 107 '66. Valence I and III. 
 
 414. History and Occurrence. Silver has been known 
 in the metallic form from the earliest historic times. It oc- 
 curs native, both crystallized and massive, and is found also 
 in combination, as sulphide, in argentite ; as sulph-antimo- 
 nite, in pyrargyrite, miargyrite, and stephanite ; as chloride 
 in cerargyrite ; as bromide in bromyrite ; as chloro-bromide 
 in embolite, etc. 
 
 415. Preparation. The process employed for the ex- 
 traction of silver varies with the quality of the ore. At 
 Freiberg, the ore an impure sulphide is roasted with ten 
 
PROPKH 77 />' 07^ S/L VER. 303 
 
 per cent of salt, the resulting mass is ground to a fine pow- 
 der, and agitated in revolving barrels containing water and 
 scrap iron, by which the silver chloride is reduced to the 
 metallic state. "Mercury is then added to dissolve the silver, 
 and by distilling the amalgam thus obtained the silver is left 
 pure. A crude modification of this process is employed in 
 Mexico and Chili. Much of the lead of commerce is argen- 
 tiferous. To extract the silver from it, the lead is melted in 
 large iron pots, and allowed to cool gradually. Crystals of 
 pure lead separate, while the alloy of silver and lead remains 
 fluid. These crystals are removed and re-melted, and again 
 allowed to cool ; so that ultimately, by a continuation of the 
 process, a very rich alloy is obtained, which may contain 300 
 ounces of silver to the ton. This alloy is then cupelled ; i. e. t 
 it is melted in a reverberatory furnace, whose hearth is com- 
 posed of bone-ash, and the lead oxidized by allowing a cur- 
 rent of air to pass over it. The lead oxide thus formed fuses 
 and is absorbed by the bone-ash, while the silver, being un- 
 altered, is finally left pure. Native copper containing silver 
 is separated from the silver by electrolysis. 
 
 416. Properties. Silver is a remarkably white, brilliant 
 metal, of specific gravity 10 '5. It is harder than gold, but 
 may be hammered into leaves only one four-thousandth of a 
 millimeter thick, and drawn into wire so fine that two thou- 
 sand meters w r ould weigh but one gram. It has a high tenac- 
 ity, the weight of 85 kilograms being required to break a 
 wire of silver two millimeters in diameter. It is the best 
 conductor of heat and electricity know r n. It is fusible at 
 about 954, and may be distilled at a full white heat. It 
 may be obtained in isometric crystals by slow cooling. When 
 melted it is capable of absorbing twenty-two times its vol- 
 ume of oxygen gas, which is again evolved when it solidifies. 
 It is unaltered in the air at any temperature, though it is 
 readily acted on by chlorine, by sulphur, and by phosphorus. 
 Nitric acid dissolves it easily, sulphuric and h/drochloric 
 
304 INORGANIC CHEMISTRY. 
 
 acids with difficulty. It is not attacked by melted niter nor 
 by fused alkali-hydrates. 
 
 417. Uses. Owing to its softness, silver is rarely used 
 alone. It is generally alloyed with copper, which, while it 
 increases its hardness, scarcely injures its color. The coin- 
 alloy of the United States and France contains 10 per cent 
 of copper; that of England, 7'5, and that of Germany 12-5 
 per cent. The silver used in silver-plate contains usually 
 from 70 to 95 per cent of pure silver. 
 
 COMPOUNDS OF SILVER. 
 
 418. Silver Chloride, AgCl, occurs native as cerargyr- 
 ite. It may be obtained by the direct union of silver and 
 chlorine, or by precipitating a solution of silver nitrate by 
 a chloride. A white, curdy mass, soluble in ammonium hy- 
 drate, but insoluble in nitric acid, is thrown down, which 
 on drying becomes a white powder. When heated it fuses, 
 and on cooling solidifies to a crystalline, translucent, sectile 
 mass resembling horn, whence the name horn-silver, some- 
 times applied to it. It has a specific gravity of 5*4, crystal- 
 lizes in isometric forms, and turns black on exposure to light. 
 For this latter reason it is used in photography. 
 
 419. Silver Oxide, Ag.,O, is usually prepared by adding 
 a strong, hot solution of silver nitrate to one of potassium 
 hydroxide. It is also the product of the combustion of silver 
 at high temperatures. It is a dark brown or black powder, 
 of specific gravity 7 '2, easily decomposed by heat and par- 
 tially by light. It is scarcely soluble in water, though am- 
 monia dissolves it readily, the solution depositing a violently 
 explosive crystalline compound, probably the nitride, Ag 3 N, 
 upon exposure to the air. Silver hydrate, Ag(OH), is a 
 strong base, reacts alkaline, and becomes silver oxide on 
 heating to 60. Silver nitrate, AgNO s , is prepared by dis- 
 solving silver in nitric acid and evaporating to crystalliza- 
 tion. Transparent orthorhombic prisms are obtained, which 
 
OCCURRENCE AND PROPERTIES OF COLD. 305 
 
 are soluble in their own weight of cold water. They fuse at 
 a moderate heat, and at a higher temperature are decom- 
 posed. Silver nitrate blackens in presence of organic mat- 
 ter ; it is used therefore as a hair-dye and for indelible ink. 
 Cast in sticks, it is employed as a caustic in surgery. Other 
 salts of silver are the sulphate, Ag 2 SO 4 , and the phosphate, 
 Ag 3 PO 4 . Silver peroxide, AgO, is obtained by electrolysis 
 of silver solutions and by the action of ozone upon the metal. 
 
 3. GOLD. 
 Symbol An. Atomic mat* 196 '7. Valence I and III. 
 
 420. Occurrence. Gold occurs quite widely distributed 
 in nature, though in small quantity. It is found generally 
 in quartz veins intersecting metamorphic rocks of various 
 ages, and in the alluvial detritus which has resulted from 
 the disintegration of these rocks. To extract the gold from 
 the auriferous quartz, the whole is finely pulverized and then 
 treated with mercury, which dissolves the gold. By pressing- 
 out the excess of mercury and distilling off that which is left 
 in the solid amalgam, the gold is obtained pure. The yield 
 of the United States gold-fields in 1866 was $86,000,000, and 
 that of Australia $30,000,000. The largest single mass was 
 found in Ballarat, Australia ; it weighed 184f pounds. 
 
 421. Properties. Gold is a soft, orange-yellow metal, 
 of specific gravity 19'33, and very brilliant. It is very duc- 
 tile, and so malleable that it may be beaten into leaves only 
 one ten-thousandth of a millimeter thick. These gold leaves 
 transmit green light, though when rendered non-lustrous by 
 heat this light is ruby-red. Gold crystallizes in isometric 
 forms, conducts heat and electricity well, and fuses at 1035. 
 It is unaltered in the air, and is not attacked by any single 
 acid or alkali-hydrate, though solutions which contain free 
 chlorine, like aqua regia, dissolve it readily. 
 
 Gold is used both for jewelry and for coinage. Being too 
 
306 l\()l{<i.l\ir r ///;.!/ /.s/V.T. 
 
 soft for either purpose alone, it is alloyed with either copper 
 or silver, the mint-alloy of the United States consisting of 
 nine parts of gold and one of copper. The purity of gold 
 for jewelry is estimated by the carat, pure gold being twenty- 
 four carats fine ; hence an alloy of eighteen parts gold to six 
 of silver and copper is said to be eighteen carats fine. Gold 
 is freed from copper by cupellation, and from silver by quar- 
 tation. The latter process consists in adding silver to the 
 alloy until the gold forms one quarter part, and then dis- 
 solving out the silver by nitric acid. The gold is left pure. 
 
 EXPERIMENT. Prepare a dilute solution of gold by adding to a 
 liter of water a few drops of a rather strong solution of auric chlo- 
 ride; then drop into it one or two fragments of phosphorus of the 
 size of a mustard-seed, and place the whole in the sunlight. Soon, 
 often in the course of a few hours, the water will have a distinct 
 purplish tint. This will deepen in color until finally, if the solution 
 has the proper strength, a beautiful ruby-red liquid will be obtained. 
 Faraday proved that the color of this liquid is due to finely-divided 
 metallic gold; so finely divided indeed that, though gold is one of the 
 heaviest of metals, it does not settle out of the liquid on standing. 
 
 COMPOUNDS OF GOLD. 
 
 422. Auric Chloride. Formula AuCl :r This chloride 
 is produced by dissolving gold in aqua regia and -removing 
 the excess of hydrochloric acid by evaporation to dryness. 
 A dark red, crystalline, deliquescent mass is obtained, which 
 is freely soluble in water, in alcohol, and in ether. It forms 
 yellow double chlorides with hydrogen, sodium, potassium, 
 and ammonium chlorides. Aurous chloride, AuCl, is ob- 
 tained by gently heating auric chloride. It is a nearly white 
 mass, permanent in the air, and insoluble in water. By boil- 
 ing water it is decomposed into auric chloride and metallic 
 gold. 
 
 423. Auric Oxide, Au 2 O s , is obtained as a dark brown 
 powder by digesting magnesia in a solution of auric chlo- 
 ride, decomposing the magnesium aurate by nitric acid, and 
 
EXERCISES. 307 
 
 drying the residue at 100. It is decomposed by light and 
 heat, and unites readily with positive oxides to yield aurates, 
 having the general formula M'AuO,. Ammonium aurate, 
 known as fulminating gold, is violently explosive. In potas- 
 sio-auric sulphite, K 3 Au"'(SO 3 ) 3 , auric oxide is basic or posi- 
 tive. Aurous oxide, A\i 2 O, is a greenish powder ; one of 
 its salts, sodio-aurous thio-sulphate, Na. 5 Au'(S 2 O 3 ) 2 , 2 aq., 
 is used in photography. 
 
 EXEKCISES. 
 
 1. What mass of copper may be obtained from 1,000 kilograms of 
 meluconite? Of chalcocite? Of malachite? 
 
 2. Calculate the composition of crystallized cupric sulphate. 
 
 3. 100 parts of silver form by union with chlorine 132-84 parts of 
 silver chloride; what is the atomic mass of silver? 
 
 4. How is silver extracted from argentiferous lead ? 
 
 5. How much silver is needed to make 250 grams silver nitrate? 
 
 (5. What is the mass of gold in a sphere five centimeters in diam- 
 eter made of a gold-copper alloy, the alloy being twenty-one carats 
 fine? 
 
 7. Cak-ulate the percentage of gold in potassium chlor-aurate. 
 
308 2SOEGAXIC CHEMISTRY. 
 
 CHAPTER ELEVENTH. 
 
 GALLIUM, INDIUM, AND THALLIUM. 
 
 1. GALLIUM. 
 Symbol Ga. Atomic mass 69*9. Valence II and III. 
 
 424. History and Properties. The element gallium 
 was discovered in 1875 by Lecoq de Boisbaudran, in a zinc- 
 blende from Pierrefitte. Its name comes from Gallia, the 
 Latin name of France. When separated by electrolysis from 
 a solution of its sulphate it is a bluish-white metal, having 
 a specific gravity of 5*9, and fusing at the very low temper- 
 ature of 30. It remains untarnished in the air at ordinary 
 temperatures, and does not decompose water. It is not vol- 
 atile up to a red heat. Heated in oxygen, it oxidizes only 
 upon the surface. It dissolves readily in hydrochloric acid 
 and in potassium hydroxide, with evolution of hydrogen. It 
 has two characteristic violet lines in its spectrum. Two chlo- 
 rides are known, GaCL, and GaCl ;! , obtained by the action of 
 chlorine upon the metal. Gallium oxide, Ga.,O,, is obtained 
 by igniting the nitrate. The nitrate, Ga(NO 3 ) 3 , and the 
 sulphate, Ga. 2 (8O 4 ) 3 , are well-known salts. The existence 
 of gallium was predicted by Mendeleeff by means of the 
 periodic series. 
 
 2. INDIUM. 
 
 Symbol In. Atomic mass 113*4. Valence II and III. 
 
 425. History, Preparation, and Properties. Indium 
 was discovered in the Freiberg zinc-blendes, by Reich and 
 Hichter, in 1863. They observed that the impure zinc chlo- 
 
OCCUPEEXCK OF THALLITM. 309 
 
 ride, obtained by dissolving the roasted ore in hydrochloric 
 acid, contained a substance whose spectrum consisted of two 
 indigo-blue lines, one of which was very brilliant and more 
 refrangible than the other. Indium is a soft, malleable metal, 
 resembling lead, of specific gravity 7/2. It is unaltered in 
 the air, and leaves a gray streak on paper. At a temper- 
 ature of 176 it melts, and burns with a violet light, produc- 
 ing the oxide. Hydrochloric and sulphuric acids dissolve 
 it readily. Indium oxide, InO, is a straw-yellow powder, 
 becoming brown on heating, and easily reducible on char- 
 coal. Indium hydrate, In"(OH). 2 , is thrown down, as a white 
 precipitate, from solutions of indium by alkali-hydrates. In- 
 dium sulphide, InS, is a dark yellow powder. Indium 
 chloride, InCl.,, is procurable as a white crystalline subli- 
 mate, which is deliquescent. Indium sulphate, In 2 (SO 4 ) 3 , 
 is easily obtained by dissolving the metal in sulphuric acid. 
 
 3. THALLIUM. 
 Symbol Tl. Atomic mam 203*7. Valence I and III. 
 
 426. History and Occurrence. Thallium was discov- 
 ered in 1861 by Crookes, in a residue left after the distilla- 
 tion of selenium from a lead-chamber deposit obtained from 
 a sulphuric-acid factory in the Hartz mountains. This resi- 
 due colored a gas-flame intensely green, and gave a spectrum 
 consisting of one brilliant green line. From the peculiar 
 tint of this line, Crookes named the metal thallium, from 
 VUMOS, a green shoot. Thallium was independently discov- 
 ered by Lamy nearly a year later. 
 
 By the aid of the spectroscope, which will detect one four- 
 thousandth of a milligram of thallium, this element has been 
 proved to be widely distributed in nature, though in very 
 minute quantities. The rare mineral crookesite is a selenide 
 of copper, thallium, and silver, and contains seventeen per 
 cent of thallium. Various specimens of iron and copper 
 
 21 
 
310 
 
 pyrites contain from a four-thousandth to a hundred-thou- 
 sandth of their volume of thallium. It occurs also in zinc- 
 blende, in certain varieties of lepidolite, and in the saline 
 residues at Nauheim. 
 
 427. Preparation and Properties. Thallium is gen- 
 erally obtained from the dust deposited in the tubes which 
 in sulphuric-acid works convey the sulphurous oxide from 
 the pyrites burners to the leaden chambers. This is extracted 
 with water, and the thallium is thrown down from this solu- 
 tion as chloride. This, by solution in sulphuric acid, gives 
 the sulphate ; and from this metallic thallium may be pre- 
 cipitated by zinc. 
 
 Thallium is a brilliant, nearly white metal, softer than 
 lead, and having a specific gravity of 11'8. It is malleable, 
 but not ductile, owing to its want of tenacity. It melts at 
 294, and crystallizes in octahedrons. It tarnishes rapidly 
 in air and burns brilliantly in oxygen. Nitric acid dissolves 
 it readily. It is strongly dia-maguetic. 
 
 428. Thallic Chloride, T1CL, is obtained by acting on 
 thallium with an excess of chlorine. It forms double salts 
 with the chlorides of the alkali-metals. Thallous chloride, 
 T1C1, is precipitated from thallous solutions by chlorides. It 
 is white and crystalline, resembling lead chloride. Thallic 
 oxide, T1 2 O 3 , is a dark red powder. Thallous oxide, T1 2 O, 
 is reddish-black in color, and dissolves in water, forming a 
 hydrate. With acids it yields salts, thallous sulphate being 
 T1 2 (SO 4 ). Thallic sulphate, T1. 2 (SO 4 ),, forms 'double sul- 
 phates with the sulphates of the alkali-metals ; but, unlike 
 those formed similarly by gallium and indium sulphates, they 
 are not true alums, and have a different crystalline form. 
 
CADMIUM, MERGUEY. 311 
 
 CHAPTER TWELFTH. 
 ZINC, CADMIUM, MEKCUKY. 
 
 1. ZINC. 
 
 Symbol Zii. Atomic mass 64*9. Valence II. Relative density 
 32*45. Molecular mass 64*9. Molecular volume 2. The mass 
 of one liter of zinc-vapor is 2*91 grams (32*5 criths). 
 
 429. History and Occurrence. An ore of zinc was 
 used by the ancient Greeks in the manufacture of brass, un- 
 der the name xa3/j.ta, a word said to be derived from Cadmus, 
 who first taught them its use. The first zinc was made in 
 Europe in the eighteenth century, it having been until that 
 time imported from China. The name zinc was given by 
 Paracelsus in the sixteenth century. Under the name cal- 
 amine a corruption of cadmia two ores of zinc are now 
 known : one a silicate, the calamine proper ; the other a car- 
 bonate, now called smithsonite. Zinc-blende or sphalerite, 
 and red zinc-ore, or zincite, are also well-known minerals. 
 
 430. Preparation and Properties. Zinc is extracted 
 from its ores by first roasting them in a reverberatory fur- 
 nace, and then distilling them, mixed with charcoal, in close 
 iron or earthen vessels. By the action of the charcoal the 
 oxygen is removed from the zinc oxide which constitutes 
 the roasted ore, and the zinc thus set free, being volatile, dis- 
 tills over into suitable receivers. In Silesia this distillation 
 is effected in peculiarly-shaped muffles of fire-clay; in Bel- 
 gium, in earthen-ware tubes ; and in England, in fire-clay 
 crucibles. The English zinc-furnace is represented in Fig. 
 99. It is conical in shape, and contains an interior dome, 
 
312 
 
 IXOR G.I X If ( 'HEM IS TR Y. 
 
 within which six crucibles are placed, each of which has a 
 hole in the bottom, through which an iron pipe passes to 
 convey away the zinc-vapor. The crucibles are charged with 
 the mixture of roasted ore and coke, the covers are cemented 
 on, and they are gradually raised 
 to bright redness. At first the 
 carbon monoxide burns at the 
 mouth of the tube, but soon the 
 greenish-white flame of zinc ap- 
 pears ; the tube is then length- 
 ened, and the condensed zinc is 
 collected in suitable vessels 
 placed beneath. It is afterward 
 re-melted, cast into ingots, and 
 sent into commerce under the 
 name of spelter. 
 
 Zinc is a bluish-white, highly 
 crystalline metal, of specific grav- 
 ity about 7-0. It is hard and Fi ^ " English zinc-furnace. 
 brittle at ordinary temperatures, and also at 200; but be- 
 tween 100 and 150 it is malleable and ductile, and may be 
 rolled into thin sheets. At 412 it melts, and at 1040 it 
 boils, evolving a vapor having half the normal density; its 
 molecule is therefore mou-atomic. Zinc is oxidized readily 
 by exposure to moist air. When strongly heated it burns 
 brilliantly, producing the oxide. It is acted upon by dilute 
 acids, by the halogens, and by alkali-hydrates. 
 
 Zinc is used largely in the arts as sheet-zinc, for various 
 purposes ; it forms the positive element of most voltaic bat- 
 teries. Its alloys are highly valuable ; with copper it forms 
 brass; with copper and tin, bronze and bell-metal, and with 
 copper and nickel, German silver. Iron alloys readily with 
 zinc on being plunged into a bath of the melted metal ; the 
 zinc coating protects the iron by a galvanic action, whence 
 iron thus treated is called galvanized iron. 
 
ZL\C CHLOIUDK AM) OM /)!<;. :>lo 
 
 COMPOUNDS OF ZINC. 
 
 431. Zinc Chloride, ZnCl 2 , may be obtained either by 
 the direct action of chlorine upon zinc, or by dissolving zinc 
 in hydrochloric acid and evaporating the solution. It is a 
 white or grayish -white, translucent, crystalline substance, 
 easily fusible, and volatile at a red heat. It is very deli- 
 quescent, and dissolves in water, forming a definite hydrate, 
 ZnCl 2 , 2 aq., which crystallizes in octahedrons. It forms defi- 
 nite compounds with ammonia and with alkali-chlorides. It 
 is used as a caustic in surgery, and in solution as an anti- 
 septic, and, with ammonium chloride, as a soldering-fluid. 
 It is also a powerful de-hydrating agent. 
 
 482. Zinc Oxide, ZnO, occurs native as red zinc-ore or 
 zincite. It is the sole product of the combustion of zinc in 
 the air, and is made commercially by conducting zinc-vapor 
 into chambers through which a current of air passes. It is 
 a white powder, unalterable in the air, becoming transiently 
 yellow on heating, and insoluble in water. It is used exten- 
 sively as a pigment. Zinc hydrate, Zn(OH) 2 , is obtained 
 on adding an 'alkali-hydrate to a solution of a zinc-salt, as a 
 white gelatinous mass, similar to alumina, but soluble in am- 
 monia. It is strongly basic, forming well-defined salts with 
 acids. Zinc sulphate, ZnSO 4 , known as white vitriol, is ob- 
 tained by oxidizing the sulphide, or by dissolving the metal 
 in sulphuric acid. It crystallizes, with seven molecules of 
 water, in orthorhombic prisms. Zinc carbonate, ZnCO 3 , 
 occurs native as smith sonite ; it is the principal ore of zinc. 
 Zinc ortho-silicate, Zn" 2 SiO 4 , occurs native as willemite ; 
 and with a molecule of water, Zn 2 SiO ( , aq., is known as 
 calamine. 
 
 483. Zinc Sulphide, ZnS, is found in nature in iso- 
 metric crystals, forming the mineral sphalerite or blende. It 
 is generally yellowish-brown in color, has a resinous luster, 
 and is translucent. It is precipitated from zinc-solutions by 
 
814 IXOIHi.LMC CIl 
 
 alkali-sulphides as a white precipitate, easily soluble in acids. 
 The native sulphide is easily converted into the sulphate by 
 roasting it with free access of air. 
 
 2. CADMIUM. 
 
 Symbol Cd. Atomic mass 111*7. Valence II. Relative density 
 55 '8. Molecular mass 111 *7 '. Molecular volume 2. 
 
 434. History and Preparation. Cadmium was dis- 
 covered in 1817 by Herrmann and also by Stromeyer ; the 
 latter gave it the name cadmium from cadmia, the ancient 
 name of zinc-ore. Its sulphide is found native as greenock- 
 ite. It occurs as an impurity in commercial zinc ; but as it 
 is more volatile than zinc, it comes over in the first products 
 of its distillation ; these are dissolved in acid, and the cad- 
 mium precipitated by zinc, in the metallic state. 
 
 435. Properties. Cadmium resembles zinc, but is whiter, 
 heavier, more easily fusible, and more volatile than that metal. 
 Its specific gravity is 8*7. It is malleable and ductile at ordi- 
 nary temperatures, but becomes brittle at 82, and crackles 
 when bent, like tin. It melts at 315, and* crystallizes in 
 regular octahedrons on cooling. It is unalterable in the air, 
 but at a red heat it burns, producing bro\vn fumes of oxide. 
 Acids act. upon it slowly. Its compounds are analogous to 
 those of zinc. 
 
 3. MERCURY. 
 
 Symbol Hg. Atomic mass 199 '8. Valence I and II. Relative 
 density 99*9. Molecular mass 199*8. Molecular volume 2. 
 The mass of one liter of mercury-vapor is 8*96 grams (100 
 criths). 
 
 436. History and Occurrence. Mercury has been 
 known from the earliest times ; it is mentioned by Theo- 
 phrastus as /(JTOS Spyvptr;, whence the Latin argentum vivum 
 and the English quicksilver. The name mercury, from the 
 
.1X1) niorKHTLKX OF MKltCi'I!}'. 315 
 
 planet of that name, was given by the alchemists to all vola- 
 tile substances, but only this one has retained it. Mercury 
 occurs native in small quantity ; but the chief ore of mer- 
 cury is the sulphide, called cinnabar, which is found princi- 
 pally in Idria in Austria, Almaden in Spain, and New Alma- 
 den in California. 
 
 437. Preparation. In Austria and Spain the mercury 
 is obtained by roasting the ore, and carrying the volatile 
 products through a series of chambers, or of long, narrow 
 pipes, in which the metal is condensed. A better process is 
 to distil the sulphide with lime or iron scales in close vessels. 
 
 438. Properties. Mercury is a brilliant, silver-white 
 metal, of specific gravity 13 '59 at 0. At ordinary temper- 
 atures it is a coherent liquid, but cooled to 40 it solidifies 
 to a malleable tin-white mass, easily sectile, and crystallizing 
 in regular octahedrons. It is slightly volatile even at 15. 
 It boils at 350, yielding a colorless vapor of specific gravity 
 6 '976. Mercury is unalterable in the air, but at its boiling 
 point it slowly absorbs oxygen, a crystalline, dark red oxide 
 forming on the surface. Hydrochloric and dilute sulphuric 
 acids do not attack it, but boiling strong sulphuric acid, and 
 even dilute nitric acid, dissolve it readily. Chlorine and 
 sulphur unite directly with it. 
 
 Mercury is used in the arts for filling thermometers and 
 barometers, and very extensively for extracting gold and sil- 
 ver from their ores. Its alloys with other metals are called 
 amalgams. Tin-amalgam is used to cover mirrors. 
 
 COMPOUNDS OF MERCURY. 
 
 439. Mercuric Chloride. Formula HgCl 2 . This chlo- 
 ride, often called corrosive sublimate, is formed when mer- 
 cury is acted upon by an excess of chlorine. It is usually 
 prepared by subliming a mixture of mercuric sulphate and 
 
 Salt: Hg(S0 4 ) + (NaCl) 8 = Na. 2 (S0 4 ) + HgCl 2 
 
 Mercuric sulphate. Sodium chloride. Sodium sulphate. Mercuric chloride. 
 
316 /.\Y>/,'r,j v/ r CHEMISTRY. 
 
 A white, semi-transparent, crystalline. mass is thus obtained, 
 which has a specific gravity of 5'43, melts at 265, and boils 
 at 295, yielding a vapor of normal density. The critical 
 pressure for the solid is about 420 millimeters. It is soluble 
 in sixteen parts of cold and three parts of hot water ; from 
 the latter solution it crystallizes on cooling in long white 
 orthorhombic prisms. Its solution tastes acrid, nauseous, and 
 metallic, and reacts acid. It is an energetic corrosive poison. 
 It coagulates albumin, forming an insoluble compound with 
 it ; whence white of egg is the best antidote for it in cases of 
 poisoning. For this reason also mercuric chloride has been 
 used to preserve wood. Its solution is decomposed by many 
 metals, with the deposition of mercury. Mercurous chlo- 
 ride, HgCl, ordinarily called calomel, is precipitated when- 
 ever a chloride is added to a solution of a mercurous salt. 
 It occurs native in tetragonal crystals. Commercially, it is 
 prepared by subliming a mixture of mercuric sulphate, mer- 
 cury, and salt : 
 
 Hg(S0 4 ) + Hg + (NaCl), = Na./SO 4 ) + (HgCl) a 
 
 The heavy white powder which condenses is washed with 
 water to remove any mercuric chloride. It is not soluble 
 in water, though chlorine-water and nitric acid dissolve it by 
 converting it into mercuric chloride. It volatilizes below a 
 red heat, yielding four volumes of vapor ; being decomposed 
 into mercuric chloride and free mercury, each of which occu- 
 pies two volumes ; hence the vapor of calomel turns gold- 
 leaf white, and sublimed calomel always contains some cor- 
 rosive sublimate. Calomel is gradually decomposed by light, 
 and is blackened by ammonium hydroxide, whence its name. 
 44O. Mercuric Iodide, HgI 2 , is precipitated as a brill- 
 iant scarlet crystalline powder, on adding a solution of po- 
 tassium iodide to one of a mercuric salt. The crystals are 
 tetragonal octahedrons ; but on heating to 200 the iodide 
 is volatilized and condenses in bright yellow orthorhombic 
 
MERCURIC AM) MKRCUKOUH SALTS. 317 
 
 plates, which on cooling pass again into the red variety. 
 This substance is therefore dimorphous, the two forms being 
 probably polymeric. Cuprous-mercuric iodide, prepared 
 by adding copper sulphate and then sulphurous acid to a 
 warm solution of mercuric iodide in potassium iodide, is a 
 brilliant carmine-red powder, which changes to a deep choco- 
 late-brown on heating to 70. Upon cooling it regains its 
 original color. Mercurous iodide, Hgl, is obtained as a 
 yellowish -green powder by precipitating a mercurous salt 
 with potassium iodide. 
 
 EXPERIMENT. Heat a little mercuric iodide in a porcelain cru- 
 cible covered with a watch-glass. Yellow crystals will be deposited 
 on the lower surface of the glass; and these, when cold, will change 
 back to red on touching them with a needle, the red color spreading 
 gradually over the entire mass. 
 
 441. Mercuric Oxide. Formula HgO. When mer- 
 cury is heated in the air to near its boiling point, red scales 
 of mercuric oxide, commonly known as red precipitate, col- 
 lect upon its surface. The same oxide is obtained by heat- 
 ing mercuric nitrate until no more nitrous fumes are evolved. 
 Mercuric oxide is soluble in acids, yielding mercuric salts. 
 The di-meta-nitrate, Hg(NO 3 ) 2 , aq., and the acid and the 
 normal mono-meta-nitrates, H 2 Hg 2 (NO 4 ),, aq., and Hg. { 
 (NO 4 ) 2 , aq., are well-known compounds. The di-meta-sul- 
 phate, Hg(SO 4 ), is decomposed by water, forming the yellow 
 ortho-sulphate, Hg,(SO (i ), turpeth mineral. Mercurous 
 oxide, Hg.,O, is an unstable black powder, obtained by the 
 action of alkali-hydrates upon calomel. With acids it forms 
 mercurous salts. 
 
 442. Mercuric Sulphide, HgS, occurs native as the 
 mineral cinnabar, both massive and in rhombohedral crys- 
 tals. It is made artificially by direct synthesis. It is brill- 
 iant red in color, and is used as a pigment under the name 
 of vermilion. Mercurous sulphide, Hg 2 S, is a black pcw- 
 der known as ethiops mineral. 
 
818 
 
 The mercury amides are very numerous. Mercuric 
 chlor-amide, Hg j Xj 2 , is known in pharmacy as white 
 precipitate. 
 
 RELATIONS OF THE GROUP. 
 
 443. The metals of this group are closely related in many 
 ways. Their molecules in the gaseous state are all moi> 
 atomic. Their specific gravity increases with the atomic muss, 
 while the fusing and boiling points decrease. The heat of 
 formation of their compounds also decreases as the atomic 
 mass increases. 
 
 Atomic Fusing Boiling Specific Heat of 
 
 mass. point. poittt. grarli;/ formation. 
 
 Zinc 64-9 412 1040 -7-0 ZnO 86,400 
 
 Cadmium 111-7 315 765 8-7 CdO 66,400 
 
 Mercury 199-8 40 350 13-6 HgO 30,600 
 
 Both zinc and cadmium are bivalent only, while mercury is 
 apparently univalent also. But the significance of molecular 
 formulas for bodies in the solid state being uncertain, the 
 simpler formula is provisionally adopted. 
 
 EXERCISER. 
 
 1. Smithsonito, containing 75 per cent of zinc carbonate, yields 
 what mass of zinc to the kilogram? 
 
 2. 500 kilograms of blende when roasted yield what mass of crys- 
 tallized zinc sulphate? 
 
 3. One cubic centimeter of mercury will give what volume of 
 vapor? 
 
 4. How much mercuric sulphate and how much salt are required 
 to give one kilogram of HgCl 2 ? Of HgCl? 
 
 5. Calculate the percentage composition of HgO. Of Hg.,O. 
 
319 
 
 CHAPTER THIRTEENTH. 
 
 POSITIVE DYADS. 
 
 1. MAGNESIUM. 
 Symbol Mg. Atomic mass 23*94. Valence II. 
 
 444. History and Occurrence. Under the name of 
 magnesia alba, magnesium carbonate was brought into Eu- 
 rope early in the eighteenth century; Black, in 1755, showed 
 that this substance contained a peculiar earth. The metal 
 was prepared first by Davy in 1808, and in a purer form 
 by Bussy in 1830. Bunsen and Matthiessen, in 1852, pre- 
 pared it by electrolysis of the fused chloride ; and in 1857 
 Deville and Caron obtained it in large quantity by acting 
 upon the chloride with sodium, a process subsequently im- 
 proved by Sonstadt. Magnesium occurs abundantly in na- 
 ture, but always in combination. Its hydrate forms the 
 mineral brucite ; its carbonate, magnesite ; its sulphate, ep- 
 somite ; its borate, boracite; its fluo- phosphate, wagnerite, 
 etc. Numerous magnesian silicates are also known; and 
 the double carbonate of magnesium and calcium, or dolo- 
 mite, exists abundantly as magnesian limestone. Magnesium 
 chloride exists in many natural waters, especially in sea- 
 water. 
 
 445. Preparation and Properties. Magnesium is 
 prepared on the large scale by heating to bright redness a 
 mixture of six parts of magnesium chloride, one of sodium 
 chloride, one of calcium fluoride, and one of sodium, in a 
 covered crucible. The globules of magnesium thus obtained 
 are purified by distillation in an atmosphere of hydrogen. 
 
320 I \OIMA\IC r//AM//.S'77M'. 
 
 Magnesium is a silver-white, brilliant metal, having a spe- 
 cific gravity of 1'75. It is somewhat malleable and ductile, 
 but is not very tenacious. It melts at a red heat, and may 
 be obtained crystallized in regular octahedrons. At higher 
 temperatures it is volatile. It is permanent in dry air, though 
 it oxidizes readily in moist air. Heated to redness it takes 
 fire and burns with a dazzling light, very rich in ultra-violet 
 rays. A wire 0-297 millimeter in thickness gives a light 
 equal to that of 74 stearin candles, five of which weigli a 
 pound. Acids attack it with ease, and it unites directly 
 with most negative elements, including nitrogen. It has 
 been used of late years as a source of light in photography, 
 
 COMPOUNDS OF MAUNKSIUM. 
 
 446. Magnesium Chloride, MgCl.,, is best prepared by 
 igniting the double chloride of magnesium and ammonium ; 
 the ammonium chloride is thereby driven off, and the mag- 
 nesium chloride is left as a white, translucent, crystalline 
 mass, readily fusible, and somewhat volatile. It is deliques- 
 cent and dissolves in water, forming the hydrate MgCl,, 
 6 aq. The mineral carnallite is a potassio-magnesium chlo- 
 ride, KMgCl 3 , 6 aq. 
 
 447. Magnesium Oxide, MgO, commonly called mag- 
 nesia, occurs native as periclasite, crystallized in isometric 
 forms. It is the sole product of the combustion of magne- 
 sium in air, and is left whenever its carbonate, hydrate, or 
 nitrate is ignited. It is an infusible, insoluble, bulky, white 
 powder, which gradually unites with water to form the hy- 
 drate. Magnesium hydrate, Mg(OH),, is precipitated from 
 solutions of magnesium salts by alkali-hydrates. It is slightly 
 soluble in water, and reacts alkaline to test-papers. It occurs 
 in nature as brucite, crystallized in rhombohedrons. Mag- 
 nesium sulphate, MgSO 4 , may be prepared by dissolving 
 the oxide, hydrate, or carbonate in sulphuric acid. It is ob- 
 vtained commercially either from sea-water, from dolomite 
 
OCCVRRKXCE OF CALCFTM. 321 
 
 a ealciomagnesian carbonate or from serpentine, which is 
 a magnesium silicate. It occurs native as epsomite, MgSO 4 , 
 7 aq., and is found also in the waters of bitter saline springs, 
 as those of Epsom in England ; whence the name Epsom salt 
 applied to this substance. It crystallizes in orthorhombic 
 prisms, containing seven molecules of crystal-water. They 
 dissolve in twice their weight of cold water at 0. Magne- 
 sium carbonate, MgCO 3 , is found in nature as the mineral 
 magnesite. Magnesia alba, the common commercial form of 
 this substance, is obtained by precipitating the sulphate with 
 sodium carbonate. It Is a light, white powder, soluble in 
 acids, even the carbonic, and having the composition H 4 Mg 4 
 (CO j,, 2 aq. It occurs native as hydromagnesite. 
 
 2. CALCIUM. 
 Symbol Ca. Atomic mass 39 -91. Valence II and IV. 
 
 448. History and Occurrence. Calcium carbonate 
 and sulphate were known to the ancients, the former being- 
 burned into lime for making mortar. It is from the Latin 
 name for lime, calx, that the word calcium is derived. The 
 metal itself was obtained in an impure form by Davy in 
 1808 ; and in 1855 Matthiessen prepared it pure and in 
 considerable quantity. Calcium is one of the most abundant 
 of the elements. As carbonate, it forms the mineral calcite, 
 and the rock-masses known as limestone, chalk, and marble. 
 As sulphate, it forms vast beds of gypsum ; as phosphate, it 
 occurs as apatite ; as fluoride, in fluor spar ; and as silicate, 
 it is found in numerous minerals. It forms an important 
 constituent of the animal skeleton, whether external or inter- 
 nal, and is essential to vegetable growth. 
 
 449. Preparation and Properties. Calcium may be 
 prepared either by the electrolysis of its chloride, previously 
 mixed with two thirds its weight of strontium chloride, and 
 fused in a porcelain crucible ; or by igniting the iodide with 
 
322 IXORGAXIC CHEMISTRY. 
 
 sodium, or the chloride with sodium and zinc, in a closed 
 vessel. It is a light yellow, brilliant metal, of specific grav- 
 ity 1*57, very malleable and ductile, and about as hard as 
 gold. It is permanent in dry air, but is oxidized if the air 
 be moist. At a red heat it burns vividly. 
 
 COMPOUNDS OF CALCIUM. 
 
 45O. Calcium Chloride, CaCl. 2 , is produced by dissolv- 
 ing the oxide or carbonate in hydrochloric acid, and in many 
 other ways. It is therefore frequently a waste product in 
 the chemical arts. On evaporating its solution in water, 
 hexagonal crystals of the hydrate, CaCl 2 , 6 aq., are obtained, 
 which lose two molecules of water when dried in vacuo, and 
 the whole at 200. The crystals are used with snow as a 
 freezing mixture ; in it a thermometer falls to 48*5. Cal- 
 cium chloride melts at a full red heat ; it has a strong attrac- 
 tion for water, and is deliquescent ; it is hence used for drying 
 
 451. Calcium Oxide, CaO, commonly known as lime, is 
 always prepared on the large scale by igniting its carbonate. 
 This operation is conducted in a rather rude furnace of ma- 
 sonry called a kiln (Fig. 100), built usually upon the side of 
 a hill. An arch of the limestone is first thrown across just 
 above the fire, and upon this the charge rests. The fuel 
 employed is generally wood, and the fire is maintained for 
 three or four days, until the whole mass is converted into 
 lime. The purer the limestone, the better the product. Per- 
 fectly pure lime is obtained by igniting crystallized calcite. 
 
 Calcium oxide is a white, hard, infusible substance, of spe- 
 cific gravity 2 '3 to 3. When moistened with water, it unites 
 directly with it, with the evolution of great heat, to form the 
 hydrate. This process is called slaking. Calcium hydrate, 
 Ca(OH) 2 , is a soft, white, bulky powder, soluble in 530 times 
 its weight of cold water, forming an alkaline, feebly caustic 
 liquid, known as lime-water, which yields, on evaporation in 
 
Pit VTA If. / TIOX OF C. I LCI I 'M OXIDK. 323 
 
 vacuo, hexagonal prisms of the hydrate. It absorbs carbon 
 ili-oxide readily. Calcium sulphate, CaSO 4 , occurs native 
 us anhydrite ; and, crystallized with two molecules of water, 
 as selenite. It is also found massive as gypsum. It is pre- 
 cipitated on adding a sulphate to a concentrated solution 
 
 Fig. 100. Lime-kiln. 
 
 of a calcium salt. By heating gypsum to 110, it parts with 
 water, producing what is called plaster of Paris. The burned 
 gypsum, on being mixed with water, again unites with it and 
 "sets" or becomes hard. Hence its use as a cement. Cal- 
 cium carbonate, CaCO.,, is an abundant mineral. It is di- 
 morphous, being orthorhombic in aragonite, and rhombohe- 
 dral in calcite. It occurs also more or less pure as marble, 
 chalk, and limestone. In water containing carbonic acid 
 it is quite soluble ; such waters are called hard. Calcium 
 phosphate, Ca 3 (PO 4 ) 2 , is precipitated from a solution of a 
 calcium salt by sodium phosphate in excess. It occurs as a 
 fhio-phosphate in the mineral apatite, and forms the chief 
 
324 INORGAXIC CUKMTSTRY. 
 
 constituent of the bones of animals. Two acid calcium phos- 
 phates, HCaPO, and H 4 Ca(PO 4 ).,, are known, the former, 
 with 2 aq., constituting the mineral brushite. 
 
 $ 3. STRONTIUM AND BARIUM. 
 STRONTIUM. Kymhol Sr. Atomic mass 87*3. Valence II and IV. 
 
 452. History and Occurrence. Strontium was distin- 
 guished as a peculiar substance by Hope in 1792. The metal 
 was first prepared pure by Bunsen and Matthiessen in 1855. 
 It occurs in nature both as sulphate or celestite, and as car- 
 bonate or strontianite. From the latter name, which is taken 
 from that of Strontian, in Scotland, where the mineral was 
 first observed, the name strontium comes. 
 
 453. Preparation and Properties. Metallic stron- 
 tium is prepared by the electrolysis of its chloride. It is a 
 pale-yellow metal, of specific gravity 2%54, harder than lead, 
 melting at a 1'ed heat, and burning vividly if exposed to the 
 air. It is quite permanent in dry air, but decomposes water 
 readily, evolving hydrogen. 
 
 COMPOUNDS OF STRONTIUM. 
 
 454. Strontium Chloride, SrCl.,, is obtained as a hy- 
 drate, SrCL,, 3 aq., by dissolving the oxide or carbonate in 
 hydrochloric acid. On evaporation, deliquescent crystals are 
 obtained, which lose their water on fusion, leaving a color- 
 less, glassy mass, soluble in water and in alcohol. 
 
 455. Strontium Oxide, SrO, is generally prepared by 
 igniting the nitrate. It is a grayish-white, porous mass, is 
 infusible, and unites energetically with water to form the 
 hydrate. Strontium hydrate, Sr(OH).,, prepared as above, 
 is soluble in water, forming an alkaline liquid which, on 
 evaporation, deposits crystals of Sr(OH) 2 , 8 aq. Strontium 
 nitrate, Sr(NO.,) 2 , is employed in pyrotechny for producing 
 a crimson fire. Strontium di-oxide, Sr lv (X, is precipitated 
 
HA III I'M AM) ITS ('(>MI>or.\I)S. 325 
 
 as a hydrate by adding hydrogen peroxide to a solution of 
 strontium hydrate. 
 
 BARIUM. Symbol Ba. Atomic mass 136*9. Valence Hand IV. 
 
 456. History and Occurrence. Barium was first rec- 
 ognized as a new element by Scheele in 1774. Davy, in 
 1808, first isolated the metal. The compounds of barium 
 which occur native are the sulphate, or barite, and the car- 
 bonate, or witherite. The former from its weight was for- 
 merly called heavy-spar ; hence the name barium, from /3/>wr, 
 heavy. 
 
 457. Preparation and Properties. Barium, obtained 
 by the electrolysis of its chloride, is a yellow, lustrous, mal- 
 leable metal, of specific gravity 4*0, which decomposes water 
 rapidly. 
 
 458. Compounds of Barium. Barium chloride, Ba 
 C1 2 , is usually obtained by dissolving the carbonate or the 
 sulphide prepared from the native sulphate in hydrochlo- 
 ric acid, and crystallizing. Orthorhombic crystals separate, 
 having the formula BaCl 2 , 2 aq. , which lose all their water 
 at 100. Barium oxide, BaO, is a grayish-white, infusible 
 mass, obtained by heating the nitrate to redness. With wa- 
 ter it slakes, forming a hydrate, Ba(OH),, which crystallizes 
 from a hot saturated solution with 8 aq. Barium nitrate, 
 Ba(NCX) 2 , is used in the green fire of pyrotechny, for which, 
 however, the chlorate, Ba(ClO 3 ) 2 , is to be preferred. Ba- 
 rium sulphate, BaSO^, occurs native as barite; when heated 
 with charcoal, it is reduced to barium sulphide, BaS. Ba- 
 rium di-oxide, Ba lv O. 2 , is produced by heating the oxide in 
 a stream of oxygen. It is used in the preparation of hydro- 
 gen peroxide. 
 
 EELATIONS OF THE GROUP. 
 
 459. To this group belong also the elements beryllium 
 and erbium. Two sub-groups are indicated here, the one 
 containing beryllium and magnesium (probably erbium also), 
 
326 I SOlid A M< ' < 'HKMISTli Y. 
 
 and the other calcium, strontium, and barium ; the affinities 
 of the former sub-group being rather with zinc and cadmium, 
 while those of the latter are with the alkalies. The specific 
 gravity of the latter sub-group increases with the atomic 
 mass. 
 
 EXERCISES. 
 
 1. To yield 5 cubic centimeters of magnesium requires how much 
 magnesite? 
 
 2. What is the relative length of two bars 5 centimeters in diam- 
 eter, one of platinum, the other of magnesium, each of which has the 
 mass of a kilogram ? 
 
 3. What mass does limestone lose in burning? 
 
 4. Compare the percentage composition of anhydrite and selonite. 
 
 5. Which contains most oxygen, strontianite or witherite? 
 
POSITIVE M OX ADS. 327 
 
 CHAPTER FOURTEENTH. 
 
 POSITIVE MONADS. 
 
 1. LITHIUM. 
 Symbol Li. Atomic mass 7 '01. Valence I. 
 
 460. History and Occurrence. Lithium oxide was 
 recognized first as a peculiar substance by Arfvedson in 
 1817. The metal was first prepared pure by Bunsen and 
 Matthiessen in 1855. Lithium is a rare substance, being 
 found principally in the minerals amblygonite, spodumene, 
 petalite, lepidolite, and triphylite. The water of a mineral 
 spring in Cornwall contains the chloride in considerable 
 quantity. Traces of lithium have been detected by the spec- 
 troscope in sea -water, in many minerals, in tobacco-ashes, 
 and even in meteorites. 
 
 461. Preparation and Properties. Lithium is best 
 obtained by the electrolysis of the fused chloride. It is a 
 brilliant, silver-white metal, somewhat softer than lead, and 
 remarkably light, having a specific gravity of only 0'578. 
 It melts at 180, and burns in the air with an intense white 
 flame when more strongly heated. It tarnishes in the air, 
 and decomposes water, evolving hydrogen. Its compounds 
 are the chloride, LiCl, a deliquescent, fusible, and volatile 
 salt; the oxide, Li,O, and hydroxide, Li(OH), the latter a 
 caustic, strongly alkaline substance ; the carbonate, Li^CCX, 
 the sulphate, Li,SO 4 , and the phosphate, Li 3 PO 4 , all of 
 which are well-defined salts. Its spectrum is characterized 
 by an intense crimson line of wave-length '0006705 milli- 
 meter. 
 
1XOIHIA MC ( 'HKMISTH Y. 
 
 2. AMMONIUM. 
 Symbol Am. Formula (NH 4 ). Molecular mass 18 '01. Valence I. 
 
 462. History. The salts which ammonia forms by di- 
 rect union with acids have a remarkable similarity to those 
 formed by the metals of this group. To account for this 
 resemblance, Berzelius, in 1816, acting upon a theory of 
 Ampere, proposed to consider these salts as compounds of 
 ammonium, a monad compound radical, (N V H 4 )', capable 
 of acting like the monad elements sodium and potassium. 
 Being unsaturated, ammonium, if it exist free, in list exist as 
 a double molecule, N 2 H 8 . Weyl, by condensing ammonia 
 gas in presence of sodium, obtained a bright blue metallic- 
 like liquid, which he assumed to be sod-ammonium, N. 2 H Na r 
 By acting upon ammonium chloride with this, a similar blue 
 liquid was obtained, which he considered to be free ammo- 
 nium. Moreover, when mercury containing one per cent of 
 sodium is placed in a saturated solution of ammonium chlo- 
 ride, it swells prodigiously in bulk, becoming a pasty mass, 
 like butter. This is the so-called ammonium amalgam. It 
 rapidly decomposes, yielding ammonia and hydrogen gases. 
 
 463. Compounds of Ammonium. Ammonium chlo- 
 ride, (NH 4 )C1, found native as sal-ammoniac, is prepared on 
 the large scale from the ammoniacal liquors of the gas-works, 
 by adding hydrochloric acid, crystallizing out the crude chlo,- 
 ride, and purifying by sublimation. It is thus obtained in 
 white fibrous masses, soluble in 2*72 parts of water at 18, 
 and crystallizing in cubes and regular octahedrons. It is 
 completely dissociated into NH 3 and HC1 at 350. Ammo- 
 nium sulphate, (NH 4 ) 2 SO 4 , is also obtained from gas-liquor. 
 It occurs in transparent, orthorhombic crystals, isomorphous 
 with potassium sulphate. Ammonium nitrate, (NH 4 )NO 3 , 
 is prepared by neutralizing nitric acid with ammonium hy- 
 droxide, and crystallizing. It is used for making hyponitrous 
 
PRKP. \ RA TION A M) P HOP Kit TIES OF SODIUM. 329 
 
 oxide gas. Commercial ammonium carbonate is a mix- 
 ture of acid carbonate and carbarnate, (H(NHjCO,) 2 and 
 (NH 4 )(NH 2 CO 2 ). On exposure to air the carbamate is vola- 
 tilized. 
 
 3. SODIUM. 
 
 Symbol Na. Atomic mass 23 '0. Valence I and III. 
 
 464. History and Occurrence. Sodium oxide was first 
 clearly distinguished from potassium oxide by Duhamel in 
 1736. The metal was first obtained by Davy in 1807. So- 
 dium is one of the most abundant of the elements. Its chlo- 
 ride, or salt, known as the mineral halite, is found not only 
 in immense deposits of rock-salt, but also in enormous quan- 
 tities in sea-water and the water of saline springs. Sodium 
 also occurs in the form of nitrate, or soda-niter; of borate, 
 or borax ; of carbonate, or trona ; and of silicate, in albite, 
 oligoclase, sodalite, etc. It is found in marine plants, and 
 is essential to animal life. 
 
 465. Preparation and Properties. Sodium is pre- 
 pared by reducing its oxide by carbon at a white heat, thus : 
 
 Nap -f C = Na 2 + CO 
 
 Practically, thirty kilograms of dry sodium carbonate, thir- 
 teen kilograms of charcoal, and three kilograms of chalk are 
 intimately mixed together, 
 calcined, and introduced in- 
 to iron cylinders heated in a 
 reverberatory furnace (Fig. 
 101). At a bright red heat 
 the sodium distills over, and 
 is collected in the flat receiv- 
 er shown in the figure. To 
 purify it, it is re-distilled, Fig.l01 Sodium-furnace. 
 
 melted under petroleum, 
 
 and cast into ingots, which are preserved under naphtha. 
 Ca'stner's process consists in reducing sodium hydrate by 
 
330 IXORd A XI< ' ( 'HEM IS TR Y. 
 
 heatiog it to 825 with an intimate mixture of finely divided 
 iron and carbon, prepared by mixing the iron with molten 
 pitch. 
 
 Sodium is a lustrous, silver-white, soft metal, of specific 
 gravity 0*98, becoming brittle at 20, and fusing at 97. 
 It crystallizes in tetragonal octahedrons. On exposure to 
 air it rapidly tarnishes, and if thrown on water, decomposes 
 it with effervescence ; if it be prevented from moving, or if 
 the water be warm, it takes fire, burning with a character- 
 istic yellow flame, and yielding a spectrum consisting of a 
 double yellow line of wave-length 0-0005892 millimeter. It 
 is used in metallurgy as a reducing agent. 
 
 COMPOUNDS OF SODIUM. 
 
 466. Sodium Chloride, NaCl, may be formed by the 
 direct union of its constituents, as by burning sodium in 
 chlorine gas. It is obtained commercially, either by mining 
 it directly, in which form it is known as rock-salt, or by evap- 
 orating the water of saline springs ; producing boiled salt, if 
 artificial heat be used, or solar salt, if the heat be natural. 
 Large quantities of salt are obtained from sea -water, of 
 which it constitutes 2'75 per cent. Sodium chloride is a col- 
 orless, transparent solid, crystallizing in cubes, and having 
 a specific gravity of 2'15. It has an agreeable saline taste, 
 is deliquescent in moist air, and is soluble in three times its 
 weight of water. It melts at 776 , 
 
 467. Sodium Oxide, Na. 2 O, and Hydroxide, Na(OH). 
 Sodium oxide may be obtained by the combustion of the 
 metal in air, or by heating the hydroxide with sodium. It is 
 a white, fusible substance, which unites directly with water to 
 form the hydroxide. Sodium hydroxide, known commonly 
 as caustic soda, is made in the pure form by the action of 
 sodium upon water. Commercially, it is prepared by the 
 action of calcium hydrate milk of lime upon sodium car- 
 bonate. The clear liquid thus obtained is evaporated in 
 
SO 1>I I M N 67, ril. I TE AND CARBOSA TE. 331 
 
 vessels of iron or of silver, and the fused mass which is left 
 is poured on to flat plates or cast into sticks. It is a white, 
 opaque, brittle solid, of specific gravity 2 '00. It is deliques- 
 cent and absorbs carbon di-oxide from the air, forming the 
 carbonate. It may be obtained crystallized in monoclinic 
 prisms, having the composition (NaOH) 2 , 7 aq. Sodium 
 peroxide, Na 2 O 2 , is produced by heating sodium in oxygen, 
 as a white, friable, deliquescent mass. 
 
 468. Sodium Sulphate, Na.,SO 4 , is obtained abundantly 
 commercially, as a residue in many chemical processes, as in 
 the preparation of nitric and hydrochloric acids. It is also 
 largely produced as an intermediate product in the soda 
 manufacture. It occurs native, anhydrous as thenardite, 
 and hydrated as mirabilite. It crystallizes from solution in 
 large colorless monoclinic prisms, which have the composi- 
 tion Na.,SO 4 , 10 aq., and which are efflorescent in dry air, 
 losing all their water. The anhydrous salt is soluble in two 
 and a half parts of water at 100. The acid salt, hydro- 
 sodium sulphate, HNaSO 4 , is formed by adding sulphuric 
 acid to the normal sulphate. 
 
 469. Sodium Carbonate, Na.,CO. { , was formerly extract- 
 ed from the ashes of marine plants. It has been produced 
 in immense quantities from salt by a process proposed by 
 Leblanc. This process consists, 1st, in treating the salt with 
 sulphuric acid, by which sodium sulphate is produced; and, 
 2d, in heating the sodium sulphate with coal and limestone 
 in a reverberatory furnace, by which sodium carbonate and 
 calcium sulphide are obtained in the form of a black mass 
 called black-ash. This is extracted with water, evaporated 
 to dryness, calcined with sawdust, and brought into com- 
 merce as soda-ash. By solution in water and evaporation, 
 sodium carbonate is obtained crystallized, Na.,C(X, 10 aq. 
 The Solvay or ammonia process, by which at present nearly 
 all of the sodium carbonate of commerce is made, depends 
 on the slight solubility of hydro-sodium carbonate in water. 
 
332 IX ORGANIC C 
 
 Hence, if a solution of hydro-ammonium carbonate be added 
 to one of sodium chloride, 
 
 NaCl + H(NHJCO 3 = HNaCO 3 -f NH 4 C1 
 hydro-sodium carbonate separates and is converted into Na 2 
 CO 3 by heat. The NH 4 C1 is treated with lime or magnesia, 
 and the ammonia thus set free is used to produce more 
 H(NH 4 )CO 3 ; and so the process becomes continuous. The 
 crystals are efflorescent, are readily soluble in water, have 
 an alkaline reaction and a nauseous taste. The acid salt, 
 hydro-sodium carbonate, BCNaCO,, is prepared by expos- 
 ing crystals of the normal salt to carbon di-oxide gas. 
 
 470. Sodium Nitrate, NaNO,, is brought from Peru, 
 where it occurs native, under the name soda saltpeter. It 
 crystallizes in rhombohedrons and is deliquescent. Normal 
 sodium phosphate, Na 3 PO 4 , is unstable. Hydro-di-sodium 
 phosphate, HNa.,PO 4 , is alkaline in its reaction, while di- 
 hydro-sodium phosphate, H,NaPQ 4 , reacts acid. 
 
 S 4. POTASSIUM. 
 Symbol K. Atomic mass 39'03. Valence I, III, and V. 
 
 471. History and Occurrence. The lye obtained by 
 leaching the ashes of land-plants has long been used in soap- 
 making ; and the solid product of the evaporation of this 
 lye has long been known in commerce as potashes, from its 
 origin. The metal potassium was first obtained by Davy in 
 1807, by the aid of electricity ; but it was soon after pre- 
 pared chemically by Gay-Lussac and Thenard. Potassium 
 occurs somewhat abundantly in nature, but always in com- 
 bination. In the mineral kingdom it is found as nitrate or 
 niter, as chloride or sylvite, as potassio-magnesium chloride, 
 or carnallite, and as sulphate, or aphthitalite. It exists also 
 in orthoclase and in muscovite, and in the waters of the 
 ocean and mineral springs. Land-plants contain it largely, 
 and it is essential to animal life. 
 
POTASSIUM AND ITS COMPOUNDS. 333 
 
 472. Preparation and Properties. Potassium is now 
 prepared by calcining an intimate mixture of the carbonate 
 with charcoal, obtained by igniting the tartrate. The process 
 is quite similar to that described for sodium ; but owing to 
 the tendency of the metal to unite directly with the carbon 
 monoxide to produce a dangerously explosive body, it is far 
 more difficult. Potassium is a soft, brilliant, bluish-white 
 metal, of specific gravity 0*865, becoming brittle at 0, and 
 at 62*5 melting to a liquid resembling mercury. From this 
 it may be crystallized in tetragonal octa- 
 hedrons. It may be distilled in hydrogen, 
 
 and gives a green vapor. It tarnishes in- 
 stantly in the air. and must therefore be 
 preserved under naphtha. Thrown upon 
 water, it at once decomposes it, evolving 
 so much heat that the hydrogen set free 
 takes fire and burns with a characteristic 
 violet flame (Fig. 102). It unites actively Fte- 102. P< 
 with chlorine and with sulphur. Its spec- 
 trum is characterized by two sharply defined lines ; one in 
 the red, of wave-length 0*0007680 millimeter, and the other 
 in the violet, of wave-length 0*0004045 millimeter. By means 
 of this spectrum as minute a quantity of potassium as one 
 three-thousandth of a milligram may be detected with cer- 
 tainty. 
 
 COMPOUNDS OF POTASSIUM. 
 
 473. Potassium Chloride, KC1, constitutes the mineral 
 sylvite. It is obtained commercially from sea-water, or from 
 an abundant mineral of the Stassfurt mines, carnallite, which 
 is a potassio-magnesium chloride. It is a transparent, color- 
 less solid, which crystallizes in cubes, has a specific gravity 
 of 1*9, and tastes like common salt. It decrepitates when 
 heated, melts at a red heat, and is volatile at higher temper- 
 atures. It dissolves in about three times its weight of water 
 at 15, producing great cold. 
 
334 INOK(;.\M< CHEMISTRY. 
 
 Potassium iodide, KI, is prepared on the large scale l>y 
 the direct action of iodine upon potassium hydroxide : 
 
 (U + (KOH) 6 = (KI; 3 + KI0 3 + (H 2 O) 3 
 
 Iodine. Potassium Potassium Potassium Water, 
 hydrate. iodide. iodate. 
 
 By evaporation of the solution, and gentle ignition of the 
 residue, the iodate is converted into iodide. Potassium iodide 
 occurs in cubical crystals, which are deliquescent in moist 
 air. It is readily soluble in water and alcohol, and has a 
 specific gravity of 3. Potassium bromide, KBr, is quite 
 similar in properties to the iodide, and is obtained by an 
 analogous process. 
 
 474. Potassium Oxide, K,O, and Hydroxide, K(OH). 
 Potassium oxide is obtained by the direct oxidation of potas- 
 sium or by the action of potassium upon the hydroxide. It 
 is a white, deliquescent, and caustic substance, which unites 
 energetically with water to form the hydroxide. This hydrox- 
 ide, commonly called caustic potash, is generally prepared by 
 the action of milk of lime calcium hydrate on potassium 
 carbonate. The solution may be evaporated, and the fused 
 hydroxide thus left be cast into sticks, the form in which it is 
 usually found in commerce. It is a white, opaque, deliques- 
 cent, brittle mass, of specific gravity 2-1, and freely soluble 
 in water and alcohol. Its solution is powerfully alkaline, 
 turning reddened litmus back again to blue, neutralizing 
 completely the strongest acids, and acting readily upon the 
 skin. In the solid form it is sometimes used as a cautery. 
 Potassium also forms a di-oxide, K.,O. ( , and a tetr-oxide, 
 
 KA. 
 
 475. Potassium Salts. Potassium chlorate, KC1O.,, 
 is prepared by passing chlorine through a solution of potas- 
 sium chloride containing milk of lime : 
 
 KC1 -f (Ca(OH),) s + (CU = (CaCl 2 ) 8 + (H 2 O) 3 -f KC1O, 
 By evaporation of the solution the chlorate crystallizes out. 
 
RUBIDIUM AND CJK8IUM. 335 
 
 Potassium sulphate, K. 2 !SO 4 , is obtained as a residue in the 
 preparation of nitric acid from niter, and is a product also 
 of the evaporation of sea-water. It forms hard orthorhom- 
 bic crystals, which have a bitter taste, and dissolve in ten 
 parts of cold water. Potassium nitrate, KNO 2 , occurs as 
 an efflorescence upon the surface of the soil in Bengal. It 
 is extracted by solution in water, and evaporation, and is 
 brought into commerce as crude saltpeter. It is also ob- 
 tained by decomposing native sodium nitrate, or native or 
 artificial calcium nitrate by potassium carbonate. It crys- 
 tallizes generally in transparent orthorhombic prisms, which 
 are not deliquescent, have a cooling taste, and dissolve read- 
 ily in water. It fuses below redness to a colorless liquid, 
 and at a high temperature is decomposed, evolving oxygen. 
 It deflagrates with combustibles, and is used in making gun- 
 powder. Potassium carbonate, K 2 CO 3 , is the essential con- 
 stituent of the crude potash of commerce, which is obtained 
 by evaporating the teachings of wood-ashes. When refined 
 it is known as pearlash. It forms a white, granular, very 
 deliquescent mass, having an alkaline reaction, and fusible 
 at full redness. It is soluble in less than its own weight of 
 water, but is insoluble in alcohol. The acid salt, hydro- 
 potassium carbonate, HKCO :i , is permanent in the air, 
 and has a faintly alkaline reaction. 
 
 5. RUBIDIUM AND CAESIUM. 
 RUBIDIUM. Symbol Rb. Atomic mass 85*2. Valence I. 
 
 476. Preparation and Properties. Rubidium was 
 first detected in the water of the Durckheim mineral spring, 
 by Bunsen, in 1860, by means of the spectroscope. Its spec- 
 trum contains two characteristic dark red lines; hence its 
 name, from the Latin rubidus, dark red. By distilling the 
 carbonate with charcoal, rubidium is obtained as a soft white 
 metal, of specific gravity 1-5. It melts at38'5, and vola- 
 
336 INORGANIC CHEMIST U Y. 
 
 tilizes below a red heat. It is more easily oxidized than 
 potassium, and takes fire in the air, burning- with a violet 
 flame. 
 
 477. Rubidium Salts. The salts of rubidium resemble 
 very closely those of potassium. The chloride crystallizes 
 in cubes, dissolves in its own weight of water at 150, and 
 forms a double salt with platinum chloride. The nitrate, 
 RbNCX, resembles saltpeter, but crystallizes in hexagonal 
 prisms. The carbonate, Rb 2 CO 3 , is an alkaline deliquescent 
 salt. The sulphate, Rb. 2 SO 4 , is isomorphous with potassium 
 sulphate. 
 
 CAESIUM. Symbol Cs. Atomic mass 132'7. Valence I. 
 
 478. History. Caesium was discovered at the same time 
 with rubidium, and in the same mineral water. The name 
 caesium comes from caesius, sky-blue, and has reference to 
 two bright blue lines in its spectrum. The Diirckheim water 
 contains in five kilograms scarcely one milligram of caesium 
 chloride ; but the lepidolite of Hebron, in Maine, contains 
 0*3 per cent of caesium, and the rare mineral pollucite con- 
 tains 32 per cent. Metallic caesium was obtained by Setter- 
 berg, in 1882, by electrolysing a mixture of four parts of 
 caesium cyanide and one part of barium cyanide. It is a 
 soft metal, as white in color as silver, has a specific gravity 
 of 1*88, and fuses between 26 and 27, passing through the 
 pasty state. The salts of caesium resemble those of rubidium. 
 
337 
 
 EXERCISES. 
 
 1. Give the theory of ammonium. Illustrate it. 
 
 2. What volume of ammonia gas in one kilogram of (NH 4 ). 2 SO 4 ? 
 
 3. Twenty kilograms Na 2 CO 3 yield how many cubic centimeters 
 of sodium? 
 
 4. One cubic centimeter rock-salt contains what mass of sodium? 
 What volume of chlorine? 
 
 5. Write the reactions in the soda-process of Leblanc. 
 
 6. One hundred kilograms of salt yield what mass of sodium car- 
 bonate? 
 
 7. By decomposing a kilogram of NaNO 3 by K 2 CO 3 what mass 
 of KNO 3 is obtained ? 
 
 8. How much water will one gram of potassium decompose? One 
 gram of sodium? 
 
 9. Bv whom were rubidium and caesium discovered? When? 
 
APPENDIX. 
 
 TABLE L THE METRIC SYSTEM. 
 
 MEASURES OF LENGTH. 
 
 Millimeter 
 
 Centimeter 
 
 Decimeter 
 
 METER 
 
 Dekameter 
 
 Hectometer 
 
 Kilometer 
 
 0-001 of a meter, 
 0-01 U 
 
 0-1 
 1 
 
 10 
 100 
 
 1000 
 
 meter, 
 
 meters, 
 
 Mvriameter 10000 
 
 0-0394 incli. 
 0-3937 M 
 3-9370 inches. 
 39-3704 " 
 393-7043 " 
 328 feet, 1 inch. 
 
 3280 10 inches 
 
 6-21 37 miles. 
 
 MEASURES OF SURFACE. 
 
 Cen tare 1 square meter, 1550 square inches 
 
 ARE 100 square meters, 119-6 square yards. 
 
 Hectare 10000 square meters, 2-471 acres. 
 
 Milliliter 
 
 Centiliter 
 
 Deciliter 
 
 LITER 
 
 Dekaliter 
 
 Hectoliter 
 
 MEASURES OF VOLUME. 
 0-001 of a liter (1 cu. cm.) 0-0610 cubic inch. 
 
 0-01 " 
 
 0-1 " 
 
 1 cubic decimeter, 
 
 10 cubic decimeters, 
 100 
 
 Kiloliter (stere) 1000 
 
 0-338 fluid ounce. 
 
 0-1056 quart. 
 61-0271 cubic inches. 
 
 2-6417 gallons (U. S.) 
 26-417 
 264-17 
 
 MASSES. 
 
 Milligram 
 
 0-001 
 
 ms. 1 
 
 cu. mm. water, 0-0154 
 
 grain 
 
 Av. 
 
 Centigram 
 
 0-01 
 
 " 10 
 
 " " 
 
 0-1543 
 
 " 
 
 M 
 
 Decigram 
 
 0-1 
 
 " 
 
 1 cu. cm. 
 
 1-5432 
 
 grains 
 
 " 
 
 GRAM 
 
 1 
 
 " 1 
 
 cu. cm. 
 
 15-4323 
 
 " 
 
 
 
 Dekagram 
 
 10 
 
 " 10 
 
 u 
 
 0-3527 
 
 ounce 
 
 
 
 Hectogram 
 
 100 
 
 " 1 
 
 deciliter 
 
 3-5274 
 
 ounces 
 
 " 
 
 Kilogram 
 
 1000 
 
 " 1 
 
 liter 
 
 2-2046 
 
 pounds 
 
 
 
 Myriagram 
 
 1 0000 
 
 " 10 
 
 liters 
 
 22-0462 
 
 
 
 
 
 Quintal 
 
 100000 
 
 " 1 
 
 hectoliter 
 
 220-4621 
 
 " 
 
 " 
 
 Tonneau 
 
 1000000 
 
 " 1 
 
 cu. meter ' 2204-6212 
 
 " 
 
 " 
 
 (339) 
 
340 
 
 A PPEXDIX TA JiLE II. 
 
 COMPARISON OF CENTIGRADE AND FAHRENHEIT DEGREES. 
 
 (Tut. Fain: 
 
 Cent. Fain: 
 
 Cait. Fain: 
 
 ('cut. Fahr. 
 
 _40 40-0 
 
 5 +23-0 
 
 + 30 +86-0 
 
 + 65 +149-0 
 
 39 38-2 
 
 4 24-8 
 
 31 87-8 
 
 66 150-8 
 
 38 36-4 
 
 3 26-6 
 
 32 89-6 
 
 67 152-6 
 
 37 34-6 
 
 2 28-4 
 
 33 91-4 
 
 68 154-4 
 
 36 32-8 
 
 1 30-2 
 
 34 93-2 
 
 69 156-2 
 
 35 31-0 
 
 32-0 
 
 35 95-0 
 
 70 158-0 
 
 34 29-2 
 
 + 1 33-8 
 
 36 96-8 
 
 71 159-8 
 
 33 27-4 
 
 2 35-6 
 
 37 98-6 
 
 72 161-6 
 
 32 25-6 
 
 3 37-4 
 
 38 100-4 
 
 73 163-4 
 
 31 23-8 
 
 4 39-2 
 
 39 102-2 
 
 74 165-2 
 
 30 22-0 
 
 5 31-0 
 
 40 104-0 
 
 75 167-0 
 
 29 20-2 
 
 6 42-8 
 
 41 105-8 
 
 76 168-8 
 
 28 18-4 
 
 7 44-6 
 
 42 107-6 
 
 77 170-6 
 
 27 16-6 
 
 8 46-4 
 
 43 109-4 
 
 78 172-4 
 
 26 14-8 
 
 9 48-2 
 
 44 111-2 
 
 79 174-2 
 
 25 13-0 
 
 10 50-0 
 
 45 113-0 
 
 80 176-0 
 
 24 11-2 
 
 11 51-8 
 
 46 114-8 
 
 81 177-8 
 
 23 9-4 
 
 12 53-6 
 
 47 116-6 
 
 82 179-6 
 
 22 7-6 
 
 13 55-4 
 
 48 118-4 
 
 83 181-4 
 
 21 5-8 
 
 14 57-2 
 
 49 120-2 
 
 84 183-2 
 
 20 4-0 
 
 15 59-0 
 
 50 122-0 
 
 85 185-0 
 
 19 2-2 
 
 Hi CO-8 
 
 51 123-8 
 
 86 186-8 
 
 18 0-4 
 
 17 62-6 
 
 52 125-6 
 
 87 188-6 
 
 17 +1-4 
 
 18 64-4 
 
 63 127-4 
 
 88 190-4 
 
 16 3-2 
 
 19 66-2 
 
 54 129-2 
 
 89 192-2 
 
 15 5-0 
 
 20 68-0 
 
 55 131-0 
 
 90 194-0 
 
 14 6-8 
 
 21 69-8 
 
 56 132-8 
 
 91 195-8 
 
 13 8-6 
 
 22 71-6 
 
 57 134-6 
 
 92 197-6 
 
 12 10-4 
 
 23 73-4 
 
 58 136-4 
 
 93 199-4 
 
 11 ll>-2 
 
 24 75-2 
 
 59 138-2 
 
 94 201-2 
 
 10 14-0 
 
 25 77-0 
 
 60 140-0 
 
 95 203-0 
 
 9 15-8 
 
 26 78-8 
 
 61 141-8 
 
 96 204-8 
 
 8 1.7-6 
 
 27 80-6 
 
 62 143-6 
 
 97 206-6 
 
 7 19-4 
 
 28 82-4 
 
 63 145-4 
 
 98 208-4 
 
 6 +21-2 
 
 +29 +84-2 
 
 +64 +147-2 
 
 99 210-2 
 
 
 
 
 +100 +212-0 
 
 -fllO +230 
 
 +210 +410 
 
 +310 +590 
 
 +410 +770 
 
 120 248 
 
 220 428 
 
 320 608 
 
 420 788 
 
 130 266 
 
 230 446 
 
 330 626 
 
 430 806 
 
 140 284 
 
 240 464 
 
 340 644 
 
 440 824 
 
 150 302 
 
 250 482 
 
 350 662 
 
 450 842 
 
 160 320 
 
 260 500 
 
 360 680 
 
 4(iO 860 
 
 170 338 
 
 270 518 
 
 370 698 
 
 470 878 
 
 180 356 
 
 280 536 
 
 380 716 
 
 480 890 
 
 190 374 
 
 290 554 
 
 390 734 
 
 490 914 
 
 +290 +392 
 
 +300 +572 
 
 +400 752 
 
 + 500 +932 
 
 +500 4932 
 
 +800 +1472 +1100 +2012 
 
 +1400 +2552 
 
 600 1112 
 
 900 1652 1200 2192 
 
 1500 2732 
 
 + 700 -1-1292 
 
 + 1000 +1832 1+1300 +2372 
 
 +1600 +2912 
 
APPENDIXTABLE III. 
 
 341 
 
 3 
 
 I 
 
 l! 
 
 /o 
 
 *"*^ O* 
 
 I?. 
 
 S' 3' 
 
 T: 
 
 Platiuic. 
 
 Auric. 
 
 Mercuric. 
 
 Mercurous. 
 
 Lead. 
 
 Arsenic. 
 
 Antimonic. 
 
 Stannic. 
 
 Stannous. 
 
 Silver. 
 
 Bismuth. 
 
 Cupric. 
 
 Cadmium. 
 
 Ferric. 
 
 Aluminum. 
 
 Chromic. 
 
 Cobalt. 
 
 Nickel. 
 
 Manganous. 
 
 Zinc. 
 
 Barium. 
 
 Strontium. 
 
 Calcium. 
 
 Magnesium. 
 
 Sodium. 
 
 Ammonium 
 
 Potassium. 
 
 Hydrogen. 
 
 23 
 
342 
 
 APPENDIX TABLE IV. 
 
 CQ 
 
 w 
 
 
 < 
 
 fc 
 
 hH- 
 ! 
 
 EH 
 
 !11g11'i < 5gSl > 3.S ! i^ I 5.9 Sla-S ( g4Fir SSsSf-g 
 
 pS c *> e 
 
 e c^s w j- KJ ^ c o 
 
 att^lz-Z-Zs-a 
 3!ssfi28S?3l 
 
 ^^oooqo^oe;^^^ 
 
 9 j <D s 
 
 I s 
 
 I 3 
 
 j g sSSSSSSS Si ?Si5lS 8 
 
INDEX. 
 
 Acetylene 232 
 
 critical temp, of . 7 
 
 Acid, antimonic . . .217 
 antimonous . . . 217 
 
 arsenic 213 
 
 arsenous 215 
 
 bismuthic . . . . 220 
 
 boric 258 
 
 bromic 148 
 
 carbonic 240 
 
 chloric 147 
 
 chlorous .... 146 
 
 chromic 280 
 
 di-phosphoric . 208 
 di-sulphuric ... 168 
 di-thionic .... 170 
 
 ferric 290 
 
 hydrazoic .... 189 
 hydrobromic . . . 120 
 hydrochloric ... 112 
 hydrofluoric . . . 121 
 hydriodic . . . , 121 
 hydrosulphuric . 154 
 hypobromous . . 148 
 hypochlorous . . 145 
 hypoiodous ... 149 
 hyponitrous ... 199 
 hyposulphurous . 157 
 
 iodic 149 
 
 manganic .... 283 
 meta-phosphoric 209 
 meta-stannic . . .266 
 
 nitric 190 
 
 nitrous 194 
 
 ortho-stannic . . 266 
 penta-thionic . . 170 
 perbromic .... 148 
 perchloric .... 148 
 perchromic . . .280 
 
 periodic 149 
 
 permanganic ... 232 
 phosphoric . . . 206 
 pyrophosphoric . 208 
 
 silicic 254 
 
 stannic 266 
 
 sulph-antimonic . 217 
 sulpho-carbonic . 249 
 sulpho-sulphuric 170 
 sulphuric . . . 162 
 sulphurous . . 159 
 tetra-thionic . . 170 
 thio-sulphuric . 170 
 tri-thionic . . .170 
 
 Acid hydrogen . . .46 
 
 Acid salts 47 
 
 Acidity of bases ... 46 
 
 Acids, basicity of . . 45 
 
 classification of . 43 
 
 defined 40 
 
 formation of . .44 
 
 meta 44 
 
 naming of .... 41 
 
 ortho 43 
 
 sulphur, etc. ... 49 
 Action, chemical, in- 
 tensity of 78 
 
 Adhesion 2 
 
 ^Ether-energy .... 6 
 Air, composition of . 179 
 Air-unit, relation of, 
 
 to H unit 90 
 
 Albite 262 
 
 Aldehydic acids of 
 phosphorus .... 209 
 
 Alkalamide 50 
 
 Allotropism 110 
 
 Alum 261 
 
 Aluminates 261 
 
 Aluminum 259 
 
 Aluminum-bronze . . 260 
 Aluminum chloride . 260 
 
 fluoride 261 
 
 hydrates 261 
 
 oxide 261 
 
 phosphate .... 261 
 
 silicates 262 
 
 sulphate 261 
 
 Alunogen 261 
 
 Amalgams 315 
 
 Amblygonite 327 
 
 Amic acids 52 
 
 Amid-hydrates . ... 52 
 Amide defined .... 50 
 Amine defined .... 50 
 
 Ammonia 185 
 
 critical temp, and 
 
 pressure of ... 7 
 Ammonia type ... 50 
 A mmonias, derived . 50 
 Ammoiiio -p 1 a t i n i c 
 
 bases 276 
 
 Ammonium 328 
 
 amalgam 328 
 
 aurate 307 
 
 carbamate .... 329 
 carbonate .... 329 
 
 chloride 328 
 
 nitrate 326 
 
 Ammonium sulphate, 328 
 Ampere's law .... 12 
 Analogues, atomic . . 26 
 
 Analysis 9 
 
 Analytical reactions . 70 
 
 Anglesite 267 
 
 Anhydrides . ... 43 
 
 Anhydrite 323 
 
 Animal coal . ... 226 
 Annabergite . ... 294 
 
 Antimony 215 
 
 Antimonic oxide and 
 
 acid 217 
 
 Antimonous oxide 
 
 and acid 217 
 
 Antimony sulphides . 217 
 
 Apatite 323 
 
 Aphthitalite 332 
 
 Aqua fortis . . . . . 192 
 
 Aqua regia 193 
 
 Aragonite 323 
 
 Argand burner .... 244 
 
 Argentite 302 
 
 Arsenates 214 
 
 Arsenic 210 
 
 Arsenic oxide and 
 
 acid 213 
 
 Arsenites . . .' . . 215 
 Arsenous oxide and 
 
 acid 214, 215 
 
 Arseno-pyrite .... 210 
 
 Arsine 211 
 
 Artiads 20, 21, 38 
 
 Asbolite 295 
 
 Atmosphere 178 
 
 Atom defined . . . . 2, 14 
 
 Atomic analogues . . 26 
 
 attraction .... 3 
 
 group, calcul'n of 84 
 
 heat 17 
 
 masses . . 5,14, 16, 17, 
 27,83 
 
 notation 27 
 
 symbols . . . . 27, 28 
 valence, how indi- 
 cated 27 
 
 Atomicity of mole- 
 cules 13 
 
 Atoms classified ... 14 
 combin'g power of, 18 
 exchange of ... 36 
 in H molecule . . 12 
 in elemental mol- 
 ecules 13 
 
 (343) 
 
344 
 
 INDEX. 
 
 Atoms, multiplication 
 
 of 28 
 
 naming of .... 11 
 
 valence of . 20, 21, 22 
 
 variation in . 38 
 
 Attraction, atomic . . 3 
 
 mass 2 
 
 molecular .... 2 
 
 Aurates 307 
 
 Auric chloride .... 306 
 
 oxide 306 
 
 Aurous chloride . . . 306 
 
 oxide 307 
 
 Aurum musivum . . 267 
 Avogadro's law- ... 12 
 Azurite 302 
 
 Barite 325 
 
 Barium 325 
 
 chlorate 325 
 
 chloride 325 
 
 di-oxide 325 
 
 hydrate 325 
 
 nitrate 325 
 
 oxide ... ... 325 
 
 sulphate 325 
 
 sulphide 325 
 
 Bases, acidity of ... 46 
 
 denned 40 
 
 naming of .... 41 
 
 ortho and meta . 45 
 
 sulphur, etc. ... 49 
 
 Basic hydrogen ... 45 
 
 salts 48 
 
 Basicity of acids ... 45 
 
 Beryllium 325 
 
 aluminate ... 261 
 
 Berthierite 218 
 
 Berthollet's laws . . 72, 73 
 Bessemer process . . 288 
 Binaries, formation 
 
 of 35,36 
 
 notation of . . . . 34 
 
 Binary molecules . . 32 
 
 naming of .... 32 
 
 terminations . 32, 33 
 
 Bismite 218 
 
 Bismuth 218 
 
 Bismuth ates 220 
 
 Bismuth carbonate . 220 
 
 nitrates 220 
 
 oxides of 220 
 
 phosphate .... 220 
 
 sulphate 220 
 
 sulphide 220 
 
 Bismuthic acid ... 220 
 
 Bismuthinite . .. . . 220 
 
 Bismuthous chloride 219 
 
 oxide and hydrate 220 
 
 sulphide 220 
 
 Bismuthyl chloride . 219 
 
 Bismutite 218 
 
 Blende 313 
 
 Blue vitriol 301 
 
 Boiling point .... 6 
 
 Bonds 28, 31, 35 
 
 Boracite 257, 319 
 
 Borax 259 
 
 Boric acid 258 
 
 oxide 258 
 
 Bornite 299 
 
 Boron 257 
 
 Boulangerite 218 
 
 Brass 300 
 
 Brimstone, roll . . .151 
 Britannia metal . . . 265 
 
 Bromine 116 
 
 acids of 148 
 
 oxides of 148 
 
 Bromyrite 302 
 
 Brongniardite .... 218 
 
 Bronze 265 
 
 Brucite 319 
 
 Brushite 324 
 
 Bunsen burner . . . 244 
 
 Cadmium 314 
 
 Caesium 336 
 
 salts of 336 
 
 Calamine 313 
 
 Calcite 323 
 
 Calcium 321 
 
 carbonate .... 323 
 
 chloride 322 
 
 hydrate 322 
 
 oxide 322 
 
 phosphate .... :->2l 
 
 sulphate 32;; 
 
 Calculations founded 
 
 on mass 79 
 
 of percentage . . 80 
 from equations, 85, 88 
 
 Calomel 316 
 
 Candle-flame 246 
 
 Carbon 224 
 
 Carbonates 240 
 
 Carbon di-oxide . . . 2:;r> 
 di-sulphide ... 248 
 mon-oxide .... 211 
 thermo-chemistry 
 
 of 2M 
 
 Carbonic acid . . . . 240 
 
 Carbonyl 241 
 
 chloride 242 
 
 Carnallite 332 
 
 Cassiterite 266 
 
 Cast iron 286 
 
 Celcstite 324 
 
 Cementation 288 
 
 Cerargyrite 304 
 
 Cerussite 267 
 
 Cervantite 216 
 
 Chalcocite 302 
 
 Chalcopyrite . ' . . . .299 
 
 Charcoal -226 
 
 Chemical action, in- 
 tensity of 78 
 
 modes of 74 
 
 Chemical changes . 4, 80 
 change, condi- 
 tions of ... 71 
 mass in ... 80 
 equations .... 69 
 
 reactions 68 
 
 relations of work 
 and energy ... 75 
 
 Chemical properties . 4 
 Chemism ...... 3 
 
 Chemistry defined . . 5 
 province of .... 3 
 
 thermo- ..... 5 
 
 Chloric acid . ..... 147 
 
 Chlorine ....... 107 
 
 acids of ..... 145 
 
 allotropism of . .110 
 oxides of ..... 145 
 
 sulphides .... 171 
 
 tetr-oxide .... 146 
 
 Chlorous oxide and 
 
 acid ...... 146 
 
 Chloro-platinates . . 276 
 Chrome-alum .... 281 
 
 Chromic acid .... 280 
 
 chloride ..... 278 
 
 hydrate ..... 281 
 
 oxide ...... 280 
 
 per-fluoride ... 279 
 tri-oxide ..... 279 
 
 Chromite ...... 278 
 
 Chromites ...... 2SO 
 
 Chromium ...... 278 
 
 sulphate ..... 281 
 
 Chromous chloride . 279 
 oxide ...... 281 
 
 Chromyl chloride . . 281 
 Chrysoberyl ..... 259 
 
 Cinnabar ....... 317 
 
 Classification of acids -i:> 
 of atoms ..... 20 
 
 of molecules . .31, -19 
 of ternaries ... 39 
 of ternary mole- 
 cules united by 
 nitrogen .... 49 
 
 Clausius's hypothesis til 
 
 Cla 
 
 -J62 
 226 
 226 
 
 . 226 
 233 
 29 1 
 
 . 295 
 295 
 
 .295 
 29:. 
 
 . 295 
 2 
 
 lay 
 Coal, animal 
 
 mineral 
 
 vegetable . 
 Coal-gas 
 Cobalt 
 
 Cobaltamines . 
 Cobaltite 
 Cobalt chlorides 
 
 oxides 
 
 Cobaltous salts 
 Cohesion 
 Colcothar ...... 291 
 
 Combination by vol- 
 ume ....... 60-66 
 
 Combining power of 
 atoms ....... 17 
 
 modification in 
 
 rule of ..... 36 
 Combustibles .... 243 
 Combustion ..... 242 
 Comp. ammonias . 50, 51 
 
 radicals . . . .37,38 
 
 Construction of equa- 
 tions ........ 70 
 
 Converter, Bessemer . 288 
 Corundum ...... 259 
 
 Cotunnite ...... 269 
 
 Covellite ....... 302 
 
INDEX. 
 
 345 
 
 Critical temperature 
 and pressure .... 7 
 
 Crocoite 278 
 
 Crocus 291 
 
 Crookesite 309 
 
 Cryolite 259 
 
 Cupric carbonate . .302 
 
 chloride 301 
 
 hydrate ..... 301 
 
 nitrate 301 
 
 oxide 301 
 
 phosphate .... 302 
 
 sulphate 301 
 
 sulphide 302 
 
 Cuprite 299, 30*2 
 
 Cuprous chloride . . 301 
 
 hydride 301 
 
 oxide 302 
 
 sulphide 302 
 
 Cyanite 255 
 
 Cyanogen 249 
 
 Deliquescence .... 141 
 
 Density 2, 56 
 
 absolute 2 
 
 relative 2 
 
 rel. of volume to . 89 
 rel. of, to sp. gr. . 90 
 periodicity of . . 24 
 rel. mol. mass to . 56 
 
 Diamine 189 
 
 Diamond 224 
 
 Diaspore 259 
 
 Diffusion, gaseous . . 58 
 
 law of 58 
 
 explanation of . . r>9 
 det. mol. mass by, 59 
 Di- hydrogen di- car- 
 bide 232 
 
 Dimorphism 152 
 
 Direct union 42 
 
 Di-sulphuric acid . . 108 
 Di-thioiiic acid ... 170 
 
 Dolomite 319 
 
 Double salts 48 
 
 Dyads, ternaries unit- 
 ed by 39 
 
 Dyscrasite 216 
 
 Effervescence .... 73 
 
 Efflorescence 141 
 
 Electricity 6 
 
 Electro - chemical se- 
 ries 19 
 
 Elemental groupings 23 
 Elements, periodic 
 
 law of 25 
 
 periodicity in 
 properties of . . 23 
 
 * Embolite 302 
 
 Emery 261 
 
 Empirical formulas . 48 
 
 Emplectite 220 
 
 Energy and work, 
 chemical relations 
 
 of 75 
 
 Equations, chemical . 69 
 construction of . 70 
 
 Equations, calcula- 
 tion from .... 85, 88 
 
 rule for writing . 69 
 
 simult. linear . . 70 
 
 Erbium 325 
 
 Erythrite 295 
 
 Etching glass .... 122 
 Ethiops mineral . . . 317 
 Ethylene 231 
 
 crit. temp, of ... 7 
 Eudiometer, Ure's . . 138 
 
 Volta's 181 
 
 Exchange of atoms in 
 forming binaries . . 36 
 
 Factors equal to prod- 
 ucts 69 
 
 Ferric acid 290 
 
 chloride 289 
 
 di-sulphide . . .293 
 
 hydrates 291 
 
 oxide 290 
 
 tri-oxide 290 
 
 Ferrites 291 
 
 Ferrous carbonate . . 292 
 
 chloride 290 
 
 oxide 292 
 
 sulphate 292 
 
 sulphide 293 
 
 Ferroso-ferric oxide . 291 
 Flowers of sulphur . 150 
 
 Fluorine 119 
 
 Fluor spar .... 119, 321 
 
 Formation of binaries 35 
 
 meta-acids .... 44 
 
 molecules .... 31 
 
 salts 46 
 
 ternaries . . . . 42, 43 
 Formulas, binary . . 34 
 calculation of . . 82 
 empirical and ra- 
 tional 48 
 
 of salts 46 
 
 use of numerals 
 
 in 34 
 
 Fowler's solution . . 215 
 
 Franklinite . . . . . 292 
 
 Fusible metal .... 219 
 
 Lipowitz's .... 219 
 
 Rose's 219 
 
 Gahnite 261 
 
 Galenite 267 
 
 Gallium 308 
 
 chlorides 308 
 
 oxide 308 
 
 nitrate 308 
 
 sulphate 308 
 
 Galvanized iron . . . :U2 
 
 Gas-carbon 226 
 
 Gaseous change, law 
 
 of 72 
 
 diffusion 58 
 
 volumes, r e d u c- 
 tion of, for tem- 
 perature .... 91 
 for pressure . . 90 
 Gay-Lussac's law . . 60 
 
 Germanium 272 
 
 German silver . . 301, 312 
 
 Gersdorffite 294 
 
 Gibbsite 261 
 
 Glass, crown .... 255 
 
 flint 255 
 
 soluble 255 
 
 Gold 305 
 
 chlorides 306 
 
 fineness of .... 306 
 oxides .... 306, 307 
 
 GSthite 291 
 
 Graham's law of dif- 
 fusion 58 
 
 Graphic symbols ... 28 
 
 Graphite 225 
 
 Gravitation 2 
 
 Greenockite 314 
 
 j Group, atomic .... 84 
 
 halogen 123 
 
 Groupings, elemental 23 
 Gypsum 323 
 
 Halite 329 
 
 Halogens 123 
 
 Haloid salts 123 
 
 Hausmaunite .... 282 
 
 Heat 3 
 
 atomic 17 
 
 of liquefaction . . 6 
 of vaporization . . 6 
 
 specific 6 
 
 Heat-unit ... 6, 103, 246 
 
 Heavy spar 325 
 
 Hematite 291 
 
 Hydrazoic acid .... 189 
 Hydrocarbons .... 228 
 Hydrobromic acid . . 120 
 Hydrochloric acid . . 112 
 Hydrofluoric acid . . 121 
 Hydriodic acid ... 121 
 Hydrogenium .... 105 
 
 Hydrogen 99 
 
 acid 46 
 
 basic 45 
 
 molecule 12 
 
 Hydrogen arsenide . 211 
 antimonide ... 216 
 
 bromide 120 
 
 carbide 228 
 
 carbonate .... 240 
 
 chloride 112 
 
 di-carbide .... 231 
 
 fluoride 121 
 
 iodide 121 
 
 nitrate 190 
 
 nitride 185 
 
 oxide 136 
 
 peroxide 143 
 
 phosphate .... 206 
 phosphide .... 203 
 
 silicate 254 
 
 silicide . . . . . .252 
 
 stannate ..... 266 
 
 sulphate 162 
 
 sulphide 154 
 
 sulphite 159 
 
 Hydromagnesite . . . 321 
 
346 
 
 INDEX. 
 
 Hydroxide 41 
 Hydroxyl 38 143 
 
 Liquor fumans Liba- 
 vii . 265 
 
 Matter and energy . . 5 
 
 Hydroxylamine . . '. 189 
 Hypochlorous oxide 
 and acid 145 
 Hyponitrous oxide 
 and acid 198 
 Hypophosphorous ox- 
 ide ... 209 
 
 Litharge 271 
 Lithium 327 
 carbonate .... 327 
 chloride 327 
 hydroxide ... ,327 
 oxide 327 
 phosphate .... 327 
 
 divisions of ... 2 
 compoimd ... 9 
 elementary. ... 9 
 physical states of, 6 
 heterogeneous . . 3 
 homogeneous . . 3 
 how studied 1 
 
 Hyposulphurous acid 157 
 
 Ice, artificial . . 167, 188 
 Illuminating gas . . . 23:3 
 Imides 51 
 
 sulphate 327 
 
 Magnesia alba .... 321 
 Magnesio-ferrite . . .292 
 Manesite ... . 3*21 
 
 motions of .... 3 
 Melaconite .... 299, 301 
 Melanterite 292 
 Melting point .... 6 
 
 Indium 308 
 
 Magnesium 319 
 
 iodide 316 
 
 chloride .... 309 
 hydrate .... 309 
 
 aluminate .... 261 
 carbonate .... 321 
 
 nitrates .... 317 
 oxide 317 
 
 oxide 309 
 sulphate .... 309 
 
 chloride 320 
 hydrate 320 
 
 sulphates . . . .317 
 sulphide 317 
 
 sulphide .... 309 
 Intensity of chemical 
 
 oxide 320 
 sulphate 320 
 Magnetism 6 
 
 Mercurous chloride . 316 
 iodide 317 
 oxide 317 
 
 lodic acid 149 
 
 Magnetite 291 
 
 sulphide 317 
 
 Iodine 117 
 
 Malachite 302 
 
 
 oxides and acids 
 of 148 
 
 Malleable iron .... 289 
 Manganese 281 
 
 specific heat of . . 7 
 Mercury amides 318 
 
 Iridium 277 
 Iron 284 
 
 chlorides 282 
 di-oxide 284 
 
 Meta-acids 44 
 formation of 44 
 
 metallurgy of, 285, 280 
 chlorides . . .289, 290 
 oxides 290 292 
 
 Manganic acid .... 283 
 oxide 2s:: 
 tri-oxide 282 
 
 Meta-elements . . 11 
 Meta-phosphoric acid, 207 
 
 Jamesonite 218 
 
 Kaolin 262 
 
 Kelp 117 
 
 Mangauite 28-1 
 Manganous carbon a te,2.s 1 
 oxide 284 
 silicate 284 
 sulphate 284 
 
 Mehithetical reaot'ns, 70 
 Meteorites, hydrogen 
 in 99 
 Methane 228 
 critical temp and 
 
 Kobellite 220 
 
 Labradorite ... 255, 262 
 Lampblack 227 
 Larderellite 257 
 
 Marcasite 293 
 Marsh-gas 228 
 critical temp, and 
 pressure of ... 7 
 Marsh's test 212 
 
 pressure of ... 7 
 Metric system .... :',;;'. 
 Miargyrite . . - 21S, :>,02 
 Mimetite 267 
 Mineral coal 226 
 
 Laughing gas .... 199 
 Law of Ampere ... 12 
 Law of Avogadro . . 12 
 combination by 
 volume . . 60 
 
 Mass, atomic . . . . 14, 57 
 how fixed . . 14, 15, 17 
 relation of densi- 
 ty to 56 
 relation of diffu- 
 
 waters 142 
 Mirabilite 331 
 Mispickel 210 
 Modes of chemical 
 action 74 
 
 diffusion 58 
 
 sion to 58 
 
 Molecular attraction 2 
 
 gaseous change . 72 
 
 calcula'n founded 
 on 79 
 
 mass . 12, 31, 56, 59, 83 
 det by diffusion 59 
 
 Law, p'eriodic .... 23 
 thermo-chemical . 76 
 Laws of Berthollet 71 72 
 
 concerned in 
 chem. changes . 80 
 definitions of . . 2 
 
 Molecular mass, rela 
 tion of, to density 56 
 motion 3 
 
 Lead 207 
 
 Mass, molecular ... 31 
 
 stability .... 68 
 
 action of water 
 on 268 
 
 fixed by density 56 
 rel. of, to den- 
 
 symbols .... 28 
 volume 56 
 
 alloys of 269 
 
 sity 56 
 
 Molecule, definition 
 
 chlorides 269 
 
 
 of . . 29 
 
 oxides 270 
 
 ecules . ... 12 
 
 formation of ... 31 
 
 Leaden-chamber proc- 
 ess 162, 165 
 Leblanc soda process, 331 
 Lepidolite 255 327 
 
 relation of, to vol- 
 ume 89 
 Mass-attraction ... 2 
 Mass-motion . 3 
 
 Molecules, atomicity 
 of 13 
 binary 31,32 
 classification of, 9, 31 
 
 Leuco-pvrite . . -210 
 
 Masses atomic, table 
 
 compound . . . 9, 31 
 
 Libethenite 302 
 Light 6 
 
 of 16 
 repr by symbols . 27 
 
 differences in . . 4 
 elemental ... 9-13 
 
 Lime 322 
 
 of factors and 
 
 multiplication of . 28 
 
 Limnite . . . 291 
 
 products equal . 69 
 
 ternary . . . . 39, 49 
 
 Limouite . . , . 285 
 
 Massicot . , . 271 
 
 unsatu rated ... 37 
 
INDEX. 
 
 347 
 
 Morenosite 294 
 Motion, atomic ... 3 
 
 Phosphoric acids, al- 
 dehydic 209 
 oxide . . 205 
 
 Properties, periodic . 23 
 prediction of ... 26 
 Pyrargyrite 218 302 
 
 molecular .... 3 
 Multiplic'n of atoms . 28 
 of molecules ... 28 
 
 Names of elements 
 
 Phosphorous oxide . 209 
 Phosphorus 200 
 red 203 
 oxides and acids 
 of 205 
 
 Pyrite 293 
 Pyrolusite 284 
 Pyromorphite .... 267 
 Pyrophorus 269 
 Pyrophosphoric acid . 208 
 
 derivation of . . . .342 
 Naming of acids bases, 
 
 Phosphorus bronze . 301 
 Photometer . . . 236, 246 
 Physical changes . . 3 
 
 Quality of combining 
 power 17 
 
 binary molecules, 32 
 
 properties . - . . 4 
 science 1 
 
 Quantity of combin- 
 ing power ... .18 
 
 elem. molecules . 11 
 Natural waters . . . .142 
 
 Physics, province of . 3 
 Pig iron 286 
 Plaster of Paris 3''3 
 
 Quartation 306 
 Quartz 253 
 Quicksilver 314 
 
 Niccolite 294 
 
 Platinum 274 
 
 
 Nickel 293 
 
 black 276 
 
 Radicals, comp. . . 38, 39 
 
 Niter 335 
 Nitric oxide 190 
 acid 190 
 Nitriles 51 
 Nitrogen 176 
 oxides and acids 
 of 189 
 di-oxide 195 
 
 chlorides 276 
 oxides 276 
 spongy 274 
 sulphides . . . .276 
 Plumbates 270 
 Plumbic carbonates . 271 
 chloride 269 
 
 artiad and peris- 
 sad 38 
 Rational formulas . . 48 
 Reactions, chemical, 68,69 
 always molecular, 68 
 classification of . 70 
 expressed by for- 
 mulas 68 
 
 tetr-oxide 193 
 
 nitrates 271 
 
 Re-agents 68 
 
 Nitrosyl 196 
 
 
 Realgar . 210 
 
 Nitrous oxide and 
 acid 194 
 
 perchloride . . .270 
 peroxide 270 
 
 Red-leads 270 
 Red precipitate . . . 317 
 
 Normal salts 47 
 Notation, atomic ... 27 
 of binaries . 34 
 
 sulphate 271 
 Plumbous oxide . . . 271 
 Pollucite 336 
 
 Reduction of gas vol- 
 umes for pressure 
 and temperature 90 91 
 
 Number of bonds 31 
 of perissad atoms, 31 
 Numeral prefixes . . 34 
 Numerals in formu- 
 las 34 
 
 Positive atoms .... 17 
 change in termi- 
 nation of . ... 42 
 Potassa-niter or salt- 
 peter 335 
 
 Refraction equivalent, 
 periodicity of ... 24 
 Relations of work and 
 energy 75 
 Rhodium 277 
 
 Olefiant gas ..... 231 
 Orpimcnt . 210 
 
 Potassio-aluminum 
 sulphate 261 
 Potassium 332 
 
 Rinman's green ... 296 
 Rock crystal . . . . 253 
 Rouge 291 
 
 Ortho-acids 43 
 
 aluminate . . 261 
 
 Rubidium 335 
 
 Orthoclase 262 
 
 bromide 334 
 
 carbonate . . . 336 
 
 Ortho-stannic acid . . 266 
 Osmium 277 
 Oxygen 126 
 
 carbonates .... 335 
 chlorate 334 
 chloride 333 
 
 chloride 336 
 nitrate 336 
 sulphate 336 
 
 critical temp, and 
 pressure of . .7, 128 
 
 chloro-chromate . 281 
 di-oxide 334 
 
 Rule for naming bina- 
 ries 32 
 
 Ozone 131 
 
 hydroxide .... 334 
 iodide . . . 334 
 
 Ruthenium 277 
 
 Palladium 277 
 Paris green -. 215 
 
 nitrate 335 
 oxide . 334 
 
 Safety-lamp 245 
 Sal-ammoniac 328 
 
 Penta-thiouic acid . . 170 
 Percentage composi- 
 tion 80 
 Perchloric acid ... 148 
 Periodic law .... 23-27 
 
 plumbate .... 270 
 sulphate 335 
 tetr-oxide .... 334 
 Power, combining, of 
 atoms 17 18 
 
 Saline waters 142 
 Salt defined 40 
 Salts, acid and nor- 
 mal 47 
 
 Periodicity in proper- 
 ties of elements . 23 
 
 Precipitant 72 
 Precipitate 72 
 
 derived from bases, 47 
 
 Perissads . ... 20, 21, 38 
 Permanganic acid . . 282 
 oxide 28 9 
 
 Precipitation 72 
 Prediction of proper- 
 ties 26 
 
 formulas of . . 46 
 haloid 123 
 
 Petalite 327 
 
 of results 73 
 
 sulphur etc 49 
 
 Petroleum series . . . 230 
 
 Prefixes, numeral . - 34 
 
 Sassolite 257 
 
 Pewter 265 
 
 Pressure critical . 7 
 
 Science 1 
 
 Phosgene gas . 242 
 
 Products and factors 
 
 
 Phosphine 203 
 
 equal 69 
 
 physical . 1 
 
 Phosphoric acid ... 206 
 
 of combustion . . 245 
 
 Selenite 323 
 
348 
 
 INDEX. 
 
 Selenium 171 
 
 Seiiarmontite .... 217 
 Series, electro - chem- 
 ical 19 
 
 homologous ... 36 
 
 Siderite 285 
 
 Signs in equations . . 69 
 
 Silicates 255 
 
 Silicic acid 254 
 
 oxide 253 
 
 Silicon 251 
 
 bronze 301 
 
 Silver 302 
 
 chloride 304 
 
 di-oxide 305 
 
 hydrate 304 
 
 nitrate 304 
 
 nitride 304 
 
 oxide 304 
 
 phosphate .... 305 
 
 sulphate 305 
 
 Simultaneous linear 
 
 equations 70 
 
 Size of elemental mol- 
 ecules 12 
 
 Smaltite 295 
 
 Smithsonite 313 
 
 Snow crystals . . . 140 
 Soda-niter or saltpe- 
 ter 332 
 
 Sodio-alumiuum chlo- 
 ride 261 
 
 Sodium C29 
 
 aluminates .... 261 
 bismuthite .... 220 
 carbonates .... 331 
 
 chloride 3:50 
 
 hydroxide .... 330 
 
 nitrate 332 
 
 oxide 330 
 
 peroxide 331 
 
 phosphates .... 332 
 
 sulphates 331 
 
 Solubility table . . . H 11 
 Solvay soda process . 331 
 Specific gravity, rela- 
 tion of, to density . . 90 
 
 heat 6 
 
 Specular iron .... 290 
 Speculum metal . . . 265 
 
 Sphalerite 313 
 
 Spinel 259, 261 
 
 Spodumeue 327 I 
 
 Stability, molecular . 68 I 
 Stannic acids .... 266 I 
 
 chloride 265 | 
 
 oxide 266 
 
 sulphide .... 267 
 Stannous chloride . . 266 
 
 oxide 267 
 
 Steam 140 
 
 Steel 287 
 
 Stephanite 302 
 
 Sterro-metal 300 
 
 Stibine 216 
 
 Stibnite 217 
 
 Stoichiotnetry .... 68 
 
 Strontianite 324 
 
 Strontium 324 
 
 chloride 324 
 
 di-oxide 324 
 
 hydrate 324. 
 
 nitrate 324 
 
 oxide 324 
 
 Substitution 43 
 
 Sulphates 168 
 
 Sulpho-carbonates . . 249 
 Sulpho-carbonic acid, 249 
 Sulpho -sulphuric 
 
 acid 170 
 
 Sulphur 149 
 
 flowers of .... 150 
 oxides and acids 
 
 of 157 
 
 Sulphuric oxide and 
 
 acid 162 
 
 Sulphurous acid . . . 159 
 
 oxide ' 158 
 
 Sylvite 332 
 
 Symbols, atomic . . 16, 27 
 
 graphic 28 
 
 Synthesis 9 
 
 Synthetical reactions, 70 
 
 Table of atomic 
 masses 16 
 
 electro- chemical 
 series 19 
 
 molecular struct- 
 ure 52 
 
 ortho and m e 1 ;i 
 acids . .^. . . . 45 
 
 periodic law . . . 25 
 
 valences 21 
 
 Tellurium 172 
 
 Temperature, reduc- 
 tion of gaseous vol- 
 umes for 91 
 
 critical 7 
 
 Terminations, binary, ::2:: 
 
 Ternary molecules, 39, 42, 
 
 49 
 
 classification of . 39 
 
 formation of ... 42 
 
 Tetrad y mite 218 
 
 Tetrahedrite 299 
 
 Tetra-thionic acid . . 170 
 Thallic sulphate . . .310 
 Thallium 309 
 
 chlorides ... .310 
 
 oxides 310 
 
 Thallous sulphate . . .310 
 
 Thenardite 331 
 
 Thenard's blue ... 296 
 Thermo-chemistry . . 5 
 Thermo-chem. laws . 76 
 Thermometer tables . 340 
 Thionic acids . . .170 
 Thio-sulphuric acid . 170 
 
 Tin 264 
 
 Tin oxides 266 
 
 salts 266 
 
 Triphylite 327 
 
 Tri-thionic acid . . . 170 
 
 Trona " . .329 
 
 Turpeth mineral . . .317 
 
 Type, ammonia . . 50 
 
 water 41 
 
 Ullmannite 294 
 
 Unit, relation of the H 
 
 to the air unit ... 90 
 Units of attraction . . 31 
 Unsaturated mole- 
 
 cules 37 
 
 Valence 20, 22 
 
 hovy indicated . . 27 
 periodicity of . . 24 
 
 table of 21 
 
 variation in . . 20, 38 
 
 Valentinite 217 
 
 Variation in valence, 
 
 20,38 
 Vegetable coal .... 226 
 
 Ventilation 246 
 
 Vermilion 317 
 
 Vitriols 169 
 
 Volume, atomic ... 24 
 periodicity of, 24 
 combination by, 60-66 
 molecular . . .56 
 relation of, to den- 
 sity 89 
 
 relation of mass to, 89 
 Volume calculations . 88 
 
 Wagnerite 319 
 
 Water . 136 
 
 critical temp, and 
 
 pressure of ... 7 
 of crystallization . 141 
 
 type 41 
 
 Waters, mineral . . .142 
 
 Wernerite 255 
 
 White precipitate . . 318 
 
 White vitriol 313 
 
 Willemite 313 
 
 Witherite 325 
 
 Wittichenite 220 
 
 Work and e n e rgy, 
 
 chemical relations of, 75 
 Wrought iron .... 286 
 
 Xanthosiderite . . . 291 
 
 Zaffre 296 
 
 Zaratite 294 
 
 Zinc 311 
 
 aluminate .... 261 
 carbonate .... 313 
 
 chloride 313 
 
 hydrate . . . . 313 
 
 oxide 313 
 
 silicates 313 
 
 sulphate 313 
 
 sulphide 313 
 
 Zincite 311, 313 
 

 
 
 

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