A text-book of inorganic chemistry

Front matter

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WORKS by G. S. NEWTH, F.I.C., F.C.S.

DEMONSTRATOR IN THE ROYAL COLLEGE OF SCIENCE, LONDON,

Preface

In drawing up a systematic course of elementary chemical instruction based upon the periodic classification of the elements, whether it be as a course of lectures, or as a text-book, a number of serious difficulties are at once encountered. These possibly are sufficient to account for the fact, that although twenty-five years have elapsed since Mendelejeff published this natural system of classification, the method has not been generally adopted as the basis of English elementary text-books.

I have endeavoured to obviate many of these difficulties, while still making the periodic system the foundation upon which this little book is based, by dividing the book into three parts. Part I. contains a brief sketch of the fundamental principles and theories upon which the science of modern chemistry is built. Into this portion of the book I have introduced, necessarily in briefest outlines, some of the more recent developments of the science in a physico-chemical direction, of which it is desirable that the student should gain some knowledge, even early in his career.

Part II. consists of the study of the four typical elements, hydrogen, oxygen, nitrogen, and carbon, and of their more important compounds. By dissociating these four elements from their position in the periodic system, and treating them separately, the student is early brought into contact with many of the simpler and more familiar portions of the science. Such

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Preface

subjects as water , the atmosi^here , and combustion , to which it is desirable that he should be introduced at an early stage in his studies, are thus brought much more forward than would otherwise be the case.

In Part III. the elements are treated systematically, according to the periodic classification. In this manner, while avoiding a sharp separation of the elements into the two arbitrary classes of metals and non-metals, it has been possible to so far conform to the prevailing methods of instruction, that all those elements which are usually regarded as non-metals (with the two exceptions of boron and silicon) are treated in the earlier portion of the book.

The science of chemistry has of recent years developed and become extended to such a degree, that the difficulty of giving a fairly balanced treatment of the subject, within the limits of a small text-book, is an ever-increasing one, and it necessarily resolves itself into a question of the judicious selection of matter. In making such a selection, I have endeavoured, as far as possible, to keep in view the requirements of students at the present time, without, however, following any examination syllabus.

Acting upon this principle, I have omitted all detailed description of the rare elements and their compounds, confining myself merely to a short mention of them in a few general remarks at the commencement of the various chapters.

Although from a purely scientific standpoint many of these rare substances are of the greatest interest and importance, it must be admitted that they stand quite outside the range of all the customary courses of chemical instruction ; and so far as the wants of the ordinary student are concerned, the space which would be occupied by an account of these elements is more advantageously devoted to such matters

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Preface

as are discussed in the Introductory Outlines. Moreover, it is a matter of common observation that text-books, even upon the shelves of reference libraries, and which bear unmistakable evidence of much use, are frequently uncut in those portions which treat of these elements.

Details of metallurgical processes, also, are out of place in a text-book of chemistry, and must be sought in metallurgical text-books. Only such condensed outlines, therefore, have been given as are sufficient to explain the chemical changes that are involved in these operations.

The great importance to the student, of himself performing experiments illustrating the preparation and properties of many of the substances treated of in his text-book, cannot well be over-estimated. If he be in attendance upon a course of chemical lectures, opportunity should be given to him for repeating the simpler experiments he may see performed upon the lecture table : if he be not attending lectures, the necessity for this practical work on his part is greater still. Instead of burdening this text-book with specific directions for carrying out such elementary experiments, frequent references have been made to my “ Chemical Lecture Experiments,” where minute directions are given for carrying out a large number of experiments, many of which may be easily performed, and with the very simplest of apparatus.

Several of the woodcuts have been borrowed from existing modern works, such as Thorpe’s “ Dictionary of Applied Chemistry,” Mendelejeffs “ Principles of Chemistry,” Ostwald’s “Solutions,” and others. Care has been taken, however, to exclude all antiquated cuts, and a large number of the illustrations are from original drawings and photographs.

South Kensington.

G. S. N.

PREFACE

TO THE NINTH EDITION

In preparing this edition I have availed myself of the opportunity, which the necessity to reset the book in type has afforded me, of making some more extensive changes and additions than the exigencies of stereotype plates would have allowed, with a view to bringing the matter well into line with the most recent advances of the science. The general plan of the book remains the same, the alterations consisting almost entirely of extensions and additions, amounting in all to about fifty pages. Some of the subjects dealt with in Part I will be found considerably amplified, without, however, any departure from the original intention of making these chapters uitroductory outlines only. A new section in the text of the book has been devoted to a description of the five new elements of the argon group, and these elements have been included in the periodic scheme of classification. For many of the most recent facts relating to these elements I am indebted to Travers’ “ Experimental Study of Gases.”

Descriptions have also been included of a number of recent manufacturing processes (several being illustrated by new cuts), which are now being carried on by the modern applications of electricity — such as the manufacture of phosphorus, graphite, caustic soda, sodium carbonate, potassium chlorate, aluminium, and others.

IX x Preface to the Ninth Edition

The atomic weights which in previous editions were given in a separate column of the table of weights, under the head of more exact values , have now been replaced by the so-called international atomic weights , which are published annually in the Berichte. Not that it is of any moment to the student whether the atomic weight of, say nickel, is 58.6 or 58.7 : but it is obviously desirable that as far as possible there shall be some uniformity, so that he shall not find a different value given in every different book he may refer to.

G. S. N«

HINTS TO STUDENTS

For the help of students who may use this book at the commencement of their chemical studies, and especially for those who may not be working under the immediate guidance of a teacher, the following hints are given : —

Begin by carefully reading the first four chapters (pages [-24). Then pass on to Part II. (page 171), and begin the study of the four typical elements, hydrogen, oxygen, nitrogen, and carbon, and their compounds, in the order in which they are treated. Accompany your reading by performing as many of the experiments referred to as possible, in order that you may become practically familiar with the substances you are studying.

During the time occupied in the study of these four elements and their compounds, again read Chapters I. to IV., and slowly and carefully continue reading Part I., so that by the time Part III. is reached, you may have fairly mastered at least the first thirteen chapters of the Introductory Outlines.

The order in which the elements are treated in Part III. is based upon the periodic classification, therefore read the short introductory remarks at the commencement of the various chapters, in the light of the table on page 118.

Throughout the book temperatures are given in degrees of the Centigrade thermometer. i° Centigrade equals i.8°

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Hints to Students

Fahrenheit, and as the zero of the latter scale is 320 below that of the Centigrade, temperatures given in degrees of one scale are readily translated into degrees of the other, by the simple formula —

The abbreviation mm. stands for millimetre; the l010o- part of a metre (1 metre = 39.37079 inches; or roughly, 25 mm. = 1 inch). The abbrevation c.c. signifies cubic centimetre; the ToVo Part °f a cubic decimetre, or litre (1 litre = 1.76077 pints).

1 gramme (the weight of 1 c.c. of distilled water, taken at its point of maximum density) = 15.43235 English grains.

Part I

CHAP. PAGE

I. Chemical Change — The Constitution of Matter- — Molecules —

II. Elements and Compounds — Mixtures — Chemical Affinity —

Modes of Chemical Action ...... 6

III. Chemical Nomenclature 15

IV. Chemical Symbols . . . . . . . .21

V. The Atomic Theory — Laws of Chemical Action ... 25

VI. Atomic Weights — Modes of Determining Atomic Weights . 34

VII. Quantitative Chemical Notation ...... 53

VIII. Valency of the Elements ....... 59

IX. General Properties of Gases — Relation to Heat and Pressure —

Liquefaction — Diffusion — The Kinetic Theory . . 69

X. Dissociation — Reversible or Balanced Actions ... 88

XI. Electrolysis — Electrolytic Dissociation — The Ionic Theory . 96

XII. Classification of the Elements — The Periodic System . .112

XIII. General Properties of Liquids — Evaporation, Boiling, Vapour

Pressure of Solutions — The Passage of Liquids into Solids — Freezing Point of Solutions — Raoult’s Method . . 126

XIV. Solution — Gases in Liquids— Liquids in Liquids — Solids in

Liquids — Osmotic Pressure — Crystalline Forms . .142

XV, Thermo-chemistry ........ 163

PART PI

THE STUDY OF FOUR TYPICAL ELEMENTS

Hydrogen — Oxygen — Nitrogen — Carbon,

AND THEIR MORE IMPORTANT COMPOUNDS.

I. Hydrogen — Hydrogenium . . . . . , .171

II. Oxygen — Allotropy — Ozone . . . . . • .181

III. Compounds of Hydrogen with Oxygen ..... 203

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Contents

CHAP.

V. Oxides and Oxy-acids of Nitrogen

VI. The Atmosphere and the Argon Group of Elements

Part III

THE SYSTEMATIC STUDY OF THE ELEMENTS, BASED UPON THE PERIODIC CLASSIFICATION

I. Elements of Group VII. (Family B.)

Fluorine : Hydrofluoric Acid. Chlorine : Hydrochloric Acid — Oxides and Oxyacids of Chlorine. Bromine: Hydrobromic Acid — Oxyacids of Bromine. Iodine: Hydriodic Acid — Oxyacids of Iodine — Periodates . . 345

II. Elements of Group VI. (Family B.)

Sulphur: Compounds of Sulphur with Hydrogen — Compounds with Chlorine — Oxides and Oxyacids of Sulphur — Oxychlorides — Carbon Disulphide. Selenium — Tellurium .......... 39 7

III. Elements of Group V. (Family B.)

Phosphorus : Compounds with Hydrogen — Compounds with the Halogens — Oxides and Oxyacids. Arsenic : Arsenuretted Hydrogen — Halogen Compounds — Oxides and Oxyacids — Sulphides. Antimo7iy: Antimony Hydride — Halogen Compounds — Oxides and Acids — Sulphides. Bismuth : Bismuth and Halogens — Oxides — Sulphides . 450

IV. Elements of Group I. (Family A.)

Potassium — Sodium — Lithium — Rubidititn — Ammonium Salts

V. Elements of Group I. (Family B.)

Copper — Silver — Gold

Contents xv

CHAP.

VI. Elements of Group II. (Family A.)

Beryllium — Magnesium — Calcium — Strontium — Barium

VII. Elements of Group II. (Family B.)

Zinc — Cadmium — Mercury ......

VIII. Elements of Group III.

Family A. : Scandium — Yttrium — Lanthanum — Ytterbium.

Family B. : Boron — Aluminium — Gallium — Indium — Thallium .........

IX. Elements of Group IV.

Family A. : Titanium — Zirconium — Cerium — Thorium. Family B. : Silicon — Germanium — Tin — Lead

X. Elements of Group V. (Family A.)

Vanadium — Niobium — Tantalum . ... .

XI. Elements of Group VI. (Family A.)

Chromium — Molybdenum — Tungsten— Uranium

XII. Elements of Group VII. (Family A.)

XIII. Transitional Elements of the First Long Period.

Iron — Cobalt — Nickel ........

XIV. Transitional Elements of the Second and Fourtpi

Long Period.

Ruthenium — Rhodium — Palladium — Osm ium — / ridium — Platinum — Argon — Helium ......

Appendix : Radium, and Radioactive Elements . Index

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70.5

Chapter I Constitution Of Matter

The science of chemistry may be described as the study of a certain class of changes which matter is capable of undergoing. Matter is susceptible of a variety of changes, some of which are regarded as physical and others as chemical. Thus, when a steel knitting-needle is rubbed upon a magnet, the needle undergoes a change, by virtue of which it becomes endowed with the power of attracting to itself iron filings or nails ; and when an ordinary lucifer match is rubbed upon a match-box the match undergoes a change, resulting in the production of flame. In the first case the change is said to be a physical one, while the ignition and combustion of the match is a chemical change.

When a fragment of ice is gently warmed, it is changed from a hard, brittle solid to a mobile, transparent liquid ; and when white of egg is gently heated, it changes from a transparent, colourless liquid to an opaque white solid. These changes, which appear at first sight to be of a similar order, are in reality essentially different in their nature : the transformation of solid ice into liquid water is a physical change, the coagulation of albumen is a chemical change.

Again, when certain substances (such as the materials which constitute the so-called luminous paint) are exposed to a bright light, they undergo a change whereby they become invested with the power to emit a feeble light when seen in the dark. A stick of phosphorus also emits a very similar light when seen in the dark. The glowing of these materials under these circumstances might readily be regarded as the result of the same kind of change in both cases ; but in reality the luminosity of the phosphorus is due to a chemical change taking place upon the surface of that substance, while the emission of light from the luminous paint is a purely physical phenomenon.

The two sciences, chemistry and physics, are so closely related and interdependent upon each other, that no sharp distinction or line of separation between them is possible. Every che7nical change that takes place is attended by some physical change, and it often happens that this accompanying physical change forms the only indication of the chemical change that has taken place. In certain important points, however, a chemical change is very different from one that is purely physical : in the latter case no material alteration in the essential nature of the substance takes place. This will be seen in the examples quoted. The steel needle remains unaltered in its essence, although by magnetisation it has acquired a new property — a property which it again loses, and which can be again and again imparted to it. The match, on the other hand, when ignited has undergone a material and permanent change : the combustible substance is now no longer combustible, neither will it ever return to its original state. The solid water, in being transformed to liquid water, has not undergone any vital change ; in essence it is the same substance merely endowed with a new property of liquidity, a property which it loses again when cooled, and which can be again and again imparted to it. On the other hand, the coagulated albumen has undergone a complete and lasting change, and never returns to its original condition.

In the same way, the luminous paint gradually ceases to emit light, and returns to its original state ; it may be exposed to the influence of light, when it once more acquires the property of phosphorescence, and this change may be brought about indefinitely, without altering the intrinsic nature of the substance. The glowing phosphorus, on the other hand, is gradually changed into a white substance, which escapes from it as a smoke or fume ; in the act of glowing the phosphorus is undergoing a process of slow burning, an<j if allowed to remain will continue glowing and burning until the whole of it has disappeared in the form of smoke.

Molecules

The Constitution of Matter. Molecules. — Matter is regarded by the chemist and physicist as being composed of aggregations of minute particles ; every substance, whether it be solid, liquid, or gaseous, presents the appearance to his mind of a vast number of extremely minute particles. To these particles the name molecules (“ little masses ”) has been given. The particles or molecules of any particular substance are all alike : thus in sulphur the molecules are all of one kind, while in water they are all of another kind ; the chemical properties associated with sulphur are the properties of the individual sulphur molecules, while those belonging to water are the properties of the molecules of that substance. All matter, therefore, is to be conceived as having what may be called a grained structure. The actual sizes of molecules is a matter which has not yet been determined with exactness ; they are orders of magnitude which are as difficult for the mind to grasp on account of their minuteness, as many astronomical measurements are by reason of their vastness. It is certain that their size is less than half a single wave-length of light,* and that therefore they are beyond the visual limits of the microscope. Some general idea of their order of magnitude may be gathered from Lord Kelvin’s calculation, that if a single drop of water were magnified to the size of the earth, each molecule being proportionately enlarged, the grained appearance which the mass would present would probably be finer than that of a heap of cricket-balls, but coarser than a heap of small shot.

It will be evident, therefore-, that in the strictest sense matter is not homogeneous , since it consists of aggregations of molecules, between which there exist certain interspaces.

The forces which similar molecules exert upon each other are regarded as physical , in contradistinction to cheinical. These forces are either attractive in their nature, or repellent. The attractive forces tend to draw the molecules closer together, and thus to cause the substance to assume the solid state ; while repellent forces, on the other hand, tend to separate the molecules and to make the substance pass into the gaseous condition. Changes which matter undergoes by the action of these forces are physical changes ; they do not affect the chemical nature and properties of the substance, which properties, as already stated, reside in the molecules themselves.

* The wave-length of the blue ray (G) = 0.0004311 millimetre, or 0.0000169 inch.

In each of the three states of matter, viz. solid, liquid, or gaseous, the molecules are conceived as being in a state of motion ; they are regarded as executing some vibratory movement within the spaces that divide them. In the solid state this movement is usually the most restricted, for the reason that in this case the intermolecular spaces are as a rule the smallest. In the gaseous condition, however, the attractive force between the molecules has been almost entirely overcome by the operation of the repellent forces. The molecules are therefore widely separated, and consequently permit of a much greater freedom of movement.

Such changes in matter, which are merely the result of alterations in the motions of the molecules, are likewise purely physical changes.

Molecules may be defined as the smallest -particles of matter which can exist in the free state', or as the smallest weight of matter in which the original properties of the matter are retained.

Atoms. — It is the belief of chemists that most molecules are possessed of a structure. That is to say, they are not simple, single, indivisible masses, but themselves consist of aggregations of still smaller particles, which are held together by the operations of some other force. These particles of which molecules are composed are termed atoms, and the force wjiich holds them together is called chemical affinity, or chemical attraction. To the mind of the' chemist, Such molecules are little systems, consisting of a number of atoms which are attracted to each other by this particular force ; in the ordinary movements of the molecule, the system moves about as a whole. In this respect it bears some analogy, on an infinitely minute scale, to a solar system. The atoms of a molecule are regarded as in a state of motion as respects one another, possibly revolving about one another, while the entire system, or molecule, at the same time performs its independent movements, just as in a solar system the various members perform various movements towards each other, while at the same time the whole system travels upon its prescribed orbit. In the case of the heavenly bodies, the force which regulates the movements of the individual members of the system amongst themselves is the same force that controls the motion of the united system, namely, gravitation. What is the precise relation, or difference, if any, between the forces which control the movements of molecules, and those which operate between the atoms of the molecule, is not known ; but as the effects produced are

Molecules and Atoms different, the latter force is distinguished by the name of chemical affinity.

Any change which matter undergoes, in which the integrity of the molecules is not destroyed, is regarded as a physical change ; while any change which arises from an alteration in the structure of the molecule is a chemical change. For example, the molecules of water consist of three separate atoms, one of oxygen and two of hydrogen ; any change which water can be made to undergo, in which these three atoms still remain associated together as the molecule, is a physical change. The water may be converted into ice, or it may be changed into steam ; but these alterations still leave the molecules intact — the three atoms still remain united as an unbroken system, and so long as this is the case chemical change has not taken place.

Suppose now the molecules of water are heated to a much higher temperature than that which is necessary to convert the water into steam, by passing electric sparks through the steam. It will then be found that a very different kind of change has come over the substance. The steam, after being so heated, no longer condenses to water again when cooled ; it has been changed into a gas which can be bubbled through water and collected in an inverted vessel filled with water standing in a pneumatic trough, and if a flame be applied to this gas a sharp explosion takes place. The change in this case is a chemical change, for the integrity of the molecules of water has been destroyed. The two atoms of hydrogen have become detached from the oxygen atom, and the original triune structure of the system is destroyed.

Atoms are therefore defined as the smallest particles of matter which can take part i?i a che7>iical chajige.

Chapter II Elements And Compounds

There are certain molecules in which all the atoms present are of the same kind, and there are other molecules which are composed of atoms which differ from one another. Thus, in the substance sulphur, all the atoms composing the molecules are alike ; while in water, as already mentioned, there are two distinct kinds of atoms in the molecule. Matter, therefore, is divided into two classes, according as to whether its molecules are composed of similar or of dissimilar atoms. Molecules consisting of atoms of the same kind are termed ele7nentary molecules , and substances whose molecules are so constituted are known as elements ; molecules, on the other hand, which contain dissimilar elements are called compound molecules , and substances whose molecules are thus composed are distinguished as compounds.

Sulphur, therefore, is an element, and water is a compound. It will be evident that in the case of elementary molecules, whatever processes they may be subjected to, only one kind of matter can be obtained from them ; while in the case of compounds, the molecules consisting of dissimilar atoms, as many different kinds of matter can be obtained as there are different atoms present. By appropriate means the atoms of hydrogen and oxygen in water molecules can be separated, and two totally different kinds of matter, namely, hydrogen and oxygen, can be obtained from this compound.

At the present time there are about seventy substances known to chemists which are believed to be elements. In the history of the science it has frequently happened that substances which were considered to be elements have proved, when subjected to new methods of investigation, to be in reality compound bodies : thus, prior to the year 1783, water was thought to be an elementary substance ; it was indeed regarded as the very type of an element, until Cavendish and Lavoisier proved that it was composed of two entirely different kinds of matter. In the year 1807 Sir

Elements and Compounds

Humphry Davy showed that the substances known as potash and soda, which were believed to be elements, were in reality compound bodies, and he succeeded in separating the constituent atoms in the molecules of these substances, and in obtaining from them two essentially different kinds of matter. It is therefore quite possible, perhaps even probable, that some at least of the forms of matter which are now held to be elements may yet prove to be compound bodies. On the other hand, the list is from time to time extended by the discovery of new elements. Thus during the last few years at least five new members have been added to the number.

The number of compounds is practically infinite.

The elements are very unequally distributed in nature, and are of very different degrees of importance to mankind. Some are absolutely essential to life as it is constituted, while others might be blotted out of creation without, so far as is known, their absence being appreciated. The following thirty elements include all the most important (for the complete list see page 22) : —

Aluminium.

Gold.

Oxygen.

Antimony.

Hydrogen.

Phosphorus.

Arsenic.

Iodine.

Platinum.

Bismuth.

Iron.

Potassium.

Bromine.

Lead.

Silicon.

Calcium.

Magnesium.

Silver.

Carbon.

Manganese.

Sodium.

Chlorine.

Mercury.

Sulphur.

Copper.

Nickel.

Tin.

Fluorine.

Nitrogen.

Zinc.

On account of certain properties common to a large number of the elements, and more or less absent in others, properties which are for the most part physical in character, the elements are divided into two classes, known as metals and non-metals. The metals generally are opaque, and their smoothed surfaces reflect light to a high degree, thus giving them the appearance known as metallic lustre. They also conduct heat and electricity. Gold, silver, copper, iron, are metals ; sulphur, bromine, oxygen, phosphorus, are non-metals. These two classes, however, gradually merge into one another, and certain elements are sometimes placed in one division and sometimes in the other, depending upon whether the distinction is based more upon their physical or their chemical properties : thus, the element arsenic possesses many of the physical properties of a metal, but in its chemical relations it is more allied to the non-metals ; such elements as these are often distinguished by the name metalloids. The following list embraces all those elements which by common consent are regarded as non-metals and metalloids, including the recently discovered elements of the argon group, which are here printed in italics : —

Arsenic.

Boron.

Bromine.

Carbon.

Chlorine.

Fluorine. Phosphorus. Helium.

Hydrogen. Selenium. Neon.

Iodine. Silicon. Argon.

Nitrogen. Sulphur. Krypton.

Oxygen. Tellurium. Xenon.

The number of atoms which compose the various elementary molecules is not the same in all cases : thus in the elements sodium, potassium, cadmium, mercury, and zinc, the molecules, when the elements are in a state of vapour, consist of only one atom. The same is true also of the newly discovered elements in the last column. The molecules of all these substances are single particles of matter. The terms molecule and atom , therefore, as applied to these elements, are synonymous. Such molecules as these are called mono-atomic molecules. In many cases elementary molecules consist of two atoms ; such is the case with the elements hydrogen, bromine, chlorine, oxygen, nitrogen, and others. Elementary molecules of this twin or dual nature are known as di-atomic molecules. Only one instance is known in which an elementary molecule consists of a trio of atoms, namely, the molecule of ozone, which is an aggregation of three oxygen atoms. This molecule is said to be t7'i-atomic. In two cases, namely, arsenic and phosphorus, the molecules are composed of a quartette of atoms, and these elements, therefore, are said to form tetr-atomic molecules. In a large number of instances the atomic constitution of the molecule of the elements is not known. These terms, mono-atomic , di-atomic , &c., are applied exclusively to molecules of elements, and are not used in reference to compounds, where the molecules are composed of dissimilar atoms.

Mechanical Mixtures. — When molecules of different kinds of matter are brought together, one of two results may follow : either they will merely mingle together without losing their identity, that

Mechanical Mixtures 9

is to say, the atoms composing the individual molecules will still remain associated together as before, or the atoms in the molecules of one kind will attach themselves to certain atoms present in molecules of another kind to form still different molecules ; in other words, there will be a redistribution of the atoms, whereby different systems or molecules are produced.