Applied chemistry; an elementary text book for secondary schools

Front matter

Book. '-■

COPYRIGHT DEPOSE

AN ELEMENTARY TEXT BOOK FOR SECONDARY SCHOOLS

Preface

The author is not very sure but that the preface of any book is a useless page. It is doubtful whether a sufficient number ever read this personal letter of the author to pay him for the writing or the publisher for printing it. Yet every writer by force of custom feels compelled to address his readers by a foreword.

Like Livy, in his preface to his History of the Roman People, I do not know whether I am doing a work worth while in putting another text of elementary chemistry before the public ; and even if I knew, modesty would forbid that I speak very strongly.

Permit me to say that to me it has never seemed necessary for a high school chemistry to present a mere skeleton of the most interesting of sciences when that skeleton may just as easily be clothed with wonderful symmetry and charming beauty. On the contrary, it has always seemed that a text for secondary schools may and ought to be a readable book just as well as one merely surfeited with facts. No dinner menu is complete which offers nothing but lean meat and vegetables. It may thus contain all that is essential, but far from all that is desired. Entrees and desserts round out the repast and give a sense of satisfaction not otherwise possible.

Such is the attempt of this text, to present the chemical facts of every-day life in a readable form and by so doing make them interesting. If this cannot be done, for most students the book is a failure.

To the teacher let me say that my long experience compels me to believe that very few classes, in a school year of nine or ten months, are able to complete a text of this size.

12 PREFACE

Some portions must be omitted. No one in a table d'hote dinner is expected to order everything on the bill of fare. Let him use judgment and discretion, the teacher likewise. Almost a quarter of a century has elapsed since I began my work in Central High School in Kansas City, one of the great high schools of the Middle West. I should not be true to my own better self did I fail to acknowledge my debt of gratitude to the hundreds of students whom I have had in that time. In this particular work I wish to thank especially Mr. J. U. Young, now head of the department of Chemistry of Central High School, Kansas City, for his many valuable suggestions and also Mr. G-. W. Davis, of the Northeast High School, Kansas City. I am also under obligations to Mr. G. H. \Vilkinson of the Physics Department of Jefferson High School, Los Angeles, Cal., who has been of material assistance in reading the manuscript ; to Mr. F. N. Peters. Jr.. of the Department of Chemistry of the University of Missouri, for suggestions in methods of presentation of certain gas laws, to Mr. V. W. Peters, of Los Angeles. Cal., for drawings from which many of the illustrations were made ; to the Goldschmidt Thermit Co., of New York City, for illustrations of thermit welding, to the Permutit \Yater Softener Co., of New York, as well as to two or three publishing houses who have extended courtesies in the way of illustrations.

F. N. P.

Los Augeles, California.

Contents

CHAPTEK I A Study of Matter 21

CHAPTEE II Water and Hydrogen Peroxide .......... 34

CHAPTEK III Oxygen and Ozone 51

Introduction

Former Method of Reasoning

Present Methods of Scientific Investigation

Old Theories of Matter

(a) Composition of

(b) Transmutation Present Ideas Elements

(a) Definition of (&) Chemical Union

(c) Method of Naming

(d) Explanation of Chemical Union Chemical Changes

Kinds and Illustrations Mixtures

1. Introduction. — Nearly every normal child is born an interrogation point. Almost as soon as he can form sentences be begins asking "why;" and many a Christmas toy has served best by its sacrifice upon the altar of childish investigation in the effort to learn what makes the noise, or why the wheels go around. The history of the child is largely the history of the human race. Were the spirit of inquiry not crushed out in childhood, grown to youth and maturity, all would still find the greatest pleasure in studying the phenomena of nature. Some few survive the rebuffs and repressions of ehildhood and to them nature ever speaks in loving and fascinating words. Others must have this instinct of investigation revived in their hearts if they find pleasure in any science.

Chemistry as one branch of learning probably enters more largely into the affairs of ordinary everyday life than any other. "Without it, not only would most of the great engineering achievements of the world, such as the construction of great bridges and transcontinental railways, and the Panama Canal; not only would the automobile and the airplane and all other modern means of rapid transportation be unknown, but the many little things of life would be mysterious and unintelligible. Cookery is a science dependent in many ways upon chemistry; pure foods and drinks can be kept so only by a knowledge of chemistry; healthful air and sanitary conditions in the home must be secured by a knowledge of chemistry on the part of some one. Careful investigation shows that a knowledge of chemistry must be had for scientific progress in almost every line of human activity. This little book, therefore, will seek to be helpful in furnishing such chemical information as shall be needed in the affairs of the home and in giving added interest to everyday life ; such, that these affairs may be administered the more wisely and that nature may speak the more intelligibly; such that those who read may not only add to their own pleasures but contribute to the welfare and happiness of all who may come under their influence.

2. Source of Scientific Knowledge. — There was a time in the world's history when scientific knowledge was thought possible of attainment by reasoning alone. Aristotle, it is said, maintained that a vessel filled with ashes or sand would hold as much water as if there were no ashes or sand in it. He never made the experiment to prove or disprove the truth of his statement and such was the strength of his influence, and such the method of reasoning* of the times and long after, that centuries passed before anyone sought to question by experiment the truth of his statement.

3. Present Methods. — In this age of the world every statement of scientific fact or supposed fact is submitted to the most rigid and searching examination; not only is reason applied, but every possible method of testing experimentally the truth of the statement is used. To illustrate: Some years ago one of England's greatest chemists announced in a paper read before a scientific gathering that he had succeeded in making a certain amount of lithium from copper by the use of radium. The next morning's sun had hardly risen before many of his hearers were preparing to repeat his experiment, not for the sake of the experiment, but to prove or disprove his claims. So, in the present age of the world, every theory of every scientist, no matter how noted he may be, or however plausible his theory may seem, must be subjected to the test of practical experiment before it can be accepted as a scientific fact.

4. Some Abandoned Theories. — As a result of the manner of thought of centuries ago, many theories were accepted as sufficiently plausible which long since have been abandoned. When a vessel of water is left exposed to the air or placed upon some source of heat, the water disappears. Centuries ago it was believed that water upon the addition of heat is changed into air; further, that the air upon the removal of the heat again becomes water. This was based upon a very superficial observation, first the disappearance of the water as stated, and second, its appearance upon the surface of any cold object brought into a warm room, as upon the outside of a tumbler of ice water. But no careful experiments were ever made to prove or disprove the theory. It was also believed that when water is boiled, a portion of it is converted into an earthy substance. True, upon the inside of the tea-kettle in the kitchen a hard, brittle crust gradually forms, but this is simply mineral matter which has been previously dissolved in the water. Pure water never leaves any such residue. But the old philosophers never made the experiment with pure water, as they might have done, to prove the truth of their position.

5. Transmutation. — At the time chemistry had its birth, philosophers believed thoroughly in the possibility of the transmutation of one substance into another. Just as they maintained that water could be changed into earth and air, and air into water, so they believed one metal could be transmuted into another. They had observed some things that to them seemed sufficient evidence. Often, in their copper mines they had noticed that the iron tools left standing for some time in the water, which seeped in, became reddish in color and looked as if the iron were changing to copper. This may be seen by putting a bright nail or knife blade into a solution of blue vitriol for a minute or two. A deposit of copper really forms upon the iron, but it may be shown experimentally that the two meta^ are simply being exchanged for one another and that the iron is not changing into copper. They knew also a process for making brass by fusing copper with an ore of zinc which they called cadmeia. They recognized there were vast differences between brass and gold, yet never did they doubt that it was entirely possible to change iron into copper and this into gold ; in fact they strongly believed in the possibility of transmuting any metal into any other if they could but learn the method.

6. Matter. — Matter is anything which occupies space, and may be visible or otherwise. Thus, air is matter just as much as is water or wood or iron. What the real composition of matter is has long been one of the great questions of man. There have possibly always been those who believed that there is but one kind of matter in all the world, and that everything we know is simply a modified form of this one kind. On the basis of such a theory it was not hard to believe in the transmutation of the metals. Others claimed there were four primary substances, — earth, air, fire, and water, and that these in a way could be changed from the one into the other.

7. Present Theory. — Robert Boyle, sometimes called the Father of Physics and Chemistry, who was born in 1626, advanced the theory that there is a large number of kinds of matter, how many no one knows. To these primary forms he gave the name of elements, and the truth of his view has long been accepted by most of the scientific world. According to this idea, an element is a substance that cannot be divided into two or more kinds of matter. Thus gold is believed to contain only gold and copper nothing but copper. At present there are known 83 elements, the greater portion of which exist in comparatively small quantities, and most of which have been discovered since the beginning of the nineteenth century. Of these, eleven are gases. two are liquids, and the others solids. Some of the rarer may on more careful study be found not to be elements, while others as yet unknown Avill probably be discovered. It is estimated that two elements, oxygen and silicon, constitute about 75 per cent of all the matter of the earth and seven others nearly all the remaining 25 per cent. Clark gives this table:

Per cent

Silicon 25.30

Aluminum 7.26

Iron 5.0S

Calcium 3.51

Magnesium 2.50

Sodium 2.28

Potassium 2.23

The same facts are shown more graphically in Fig. 1.

Silicon 25 Jo

E

3 3

JUKI

s fcll

Fig. 1. — Abundance of certain elements.

8. Compounds. — A compound is a substance containing two or more elements chemically united and invariably in the same proportion by weight, The most familiar of all compounds is water, which consists of two elements, hydrogen and oxygen, always in the proportion of 1 to 8. Common salt is another compound containing the two elements, sodium and chlorine, always united in the proportion approximately of 46 to 71.

9. Chemical Union Denned. — In defining a compound in the preceding paragraph the expression, chemically united, was used. If two substances are mixed, the resulting product will partake of the nature of each ingredient. Two white substances will give a white product, a red and white will give a pink, a white and black a gray. But if two substances differing from each other unite chemically the product formed may not partake of the properties of either even to the slightest extent, and will be essentially different. To illustrate : Hydrogen and oxygen are both colorless gases, the former inflammable ; the latter essential for life and ordinary combustion. When the two unite chemically, at ordinary temperatures, the resulting product is a liquid, which is not only not inflammable but will even extinguish fire and cannot be inhaled. Sodium, in common salt, is a soft metal, silvery white in color, which upon the moistened hand or in the mouth would catch fire and produce most serious burns. Chlorine, the other ingredient, is a heavy yellow gas, terribly destructive of life if inhaled and used with frightful results in the late great war. When these two unite chemically each loses its properties, and the two produce an entirely new substance, not only not harmful, in ordinary quantities, but even regarded as an essential in the animal economy. Likewise, two white substances, uniting chemically, may produce a brilliant red, as do potassium iodide and mercuric chloride; two gases may form a solid, as will ammonia and hydrogen chloride ; two liquids a solid. Many of these in great variety will be taken up from time to time and need not be emphasized here.

10. General Plan of Naming Compounds. — A few general statements as to how compounds are named will be helpful at this time. In the early days of chemistry no plan was followed in naming the various substances prepared. As a result, peculiar and fantastic names of very familiar things have come doAvn to us. At the present time so vast is the number of compounds known - — hundreds of thousands — that some very definite and systematic method is necessary. In most cases as soon as a chemist hears the name of a compound, he knows its composition even though it may be one not familiar to him. Common salt is chemically known as sodium chloride, and one knows immediately that it consists of sodium and chlorine ; if the name ends in ide the compound contains only the elements mentioned, which, except in a few cases, are but two in number. Thus, mercuric chloride contains mercury and chlorine; potassium iodide, potassium and iodine. If the name of the compound ends in ate, with few exceptions which need not be mentioned here, the compound contains oxygen, in addition to the other elements named. Thus, sodium chlo-

Fig. 2. — Showing the "north" end of a magnetic needle being attracted by the "south" end of another.

rate contains sodium, chlorine and oxygen; potassium sulphate, potassium, sulphur and oxygen.

11. What Elements will Unite? — -Not every element will unite with every other element. If two magnets, either bar or horseshoe, be placed together, end to end, there will be no attraction if the two ends marked — are brought together or likewise if the two marked + > but if an end marked + be brought up to one with the opposite sign they adhere strongly. This is always true. Everyone is familiar with the ordinary compass, often spoken of as the mariner's compass. If the end of the needle which points north be approached by the north end of a similar magnetic needle, the one free to move will swing away; if the opposite end be approached they will attract each other. (See Fig. 2.) From these facts a simple law has been formulated: "Like poles repel and unlike poles attract each other. ' ' If the ends of two wires connected with an electric battery be dipped in a solution through which the current can pass in a U-shaped tube as shown in Fig. 3, the wire upon which the current enters is spoken of as the anode, from a Greek word meaning the road in and the wire upon which the current passes out is called the cathode, or the road out. Often the

Fig. 3. — The wire marked + is the anode and the other is the cathode.

anode is called the positive and the cathode the negative electrode. Now if the solution used be one of common salt, sodium chloride, it will be found that the sodium always collects at the cathode and the chlorine at the anode. For this reason, applying the law stated above, sodium is regarded as a positive element and chlorine as a negative. In general, in all similar compounds the metal collects at the cathode and the other element at the anode. Hence, all such consist of a positive and a negative element or group of elements. In naming such compounds the positive is always given first. Thus, sodium chloride contains a positive element, sodium, and a negative element, chlorine. Copper sulphate contains copper, a positive element and a negative group, consisting of sulphur and oxygen. It would seem then from these statements that chemical union is a kind of electrical attraction.

12. Chemical Changes, Kinds. — There are several kinds of chemical changes ; in all cases the identity and the characteristics of the substances involved are lost or destroyed. This has been illustrated in the case of hydrogen and oxygen uniting to form water and of sodium and chlorine, to form common salt. Such as these are very simple and are known as "Additive Reactions," an expression which indicates that the two substances have been added or joined together and have formed a single substance. Another similar and very familiar case is that of: flashlight powders used in photography. The essential ingredient, that which produces the intensely white light, is magnesium, a steel-gray metal which has been powdered. In burning, it simply combines with oxygen, producing a white compound known as magnesium oxide, often called magnesia, used in cleaning felt hats, kid gloves, as a dressing for white shoes and for similar well-known purposes.

13. Simple Decomposition. — Another kind of chemical change equally simple as the preceding is known as "Simple Decomposition." In such changes the process is the reverse of the additive. A single compound by heat or some other force is decomposed into its component elements. To illustrate by a familiar example, mercuric oxide, a compound whose name indicates its composition, if heated strongly is decomposed into mercury, which collects upon the sides of the vessel in which it is heated, and oxygen, which is invisible, but which may be detected by holding a pine splinter with a spark upon the end above in the outgoing current of gas. The splinter will burst into a flame. Likewise, if a current of electricity be passed through water acidulated to render it a conductor, it will decompose the liquid into the two gases of which it is composed.

14. Metathesis, or Double Decomposition. — By far the greater number of chemical changes are not as simple as the two kinds already mentioned. More frequently two, and sometimes more than two, substances unite or react with each other, in which case both substances are decomposed and two or more new ones are produced, by a rearrangement of the elements contained in the compounds. Such a change is spoken of as "Metathesis" or "Double Decomposition." It may be illustrated by adding a few cubic centimeters of a solution of potassium iodide to one of mercuric chloride in a test tube. Two new substances are formed, both entirely different from the original, one of them now a brilliant red color and not soluble in water. Numerous illustrations of this kind of change will be had from time to time. Really, metathesis is but a combination of the other two kinds of change in which both or all of the substances used are decomposed and the products combined in a new way.

15. Mixtures. — A mixture differs from a compound in that the composing substances do not unite with each other as in additive reactions; neither is there any rearranging of the elements into new groupings. Further, as a rule, no definite amounts of the two substances are used, or at least are not necessary. The particles of one intermingle with those of the other, but each retains all its own properties. White sand may be mixed with common salt, but neither has lost its distinguishing properties. A little placed on the tongue will possess a salty taste and at the same time will have the gritty feeling of the sand. Moreover, one may readily be separated from the other by adding water, stirring and after a few minutes decanting or filtering. A common case given by nearly all books is that of fine iron filings and flowers of sulphur. Mixed together, the result is a greenish-gray powder, but neither has lost its distinguishing properties, and as in the case of the salt and sand they may be readily separated. With patience most of the iron filings may be successfully separated from the sulphur by a good magnet. An easier and more satisf actory method is to add carbon disulphide which upon shaking will dissolve the sulphur as water will salt. The dissolved sulphur may then be poured off through a filter paper ; if the filings are washed with another portion of the carbon disulphide all the sulphur may be removed. By evaporating the liquid the sulphur may be recovered with all the properties it possessed before. If, however, the intimate mixture be heated for some time strongly in a test tube, the resulting mass will be black instead of greenish, will not be attracted by the magnet as the filings were, and the sulphur cannot be removed by solution. Chemical union has taken place and we now have a compound of iron and sulphur, called iron sulphide.

1. Do you believe Aristotle's statement about the globe of sand? Give reason for your answer.

2. At the present time how is scientific truth obtained? Can reason aid at all in the discovery of Nature's laws? Explain.

3. What was the old idea regarding the relation of water to air? "What facts had they to cause such a belief?

4. What is meant by transmutation? What led the ancient philosophers to believe in such a thing? Do you believe it possible? Why?

5. What is matter? How many kinds can you find in this book? In this room? Give two old theories about the composition of matter.

6. "What was Boyle's idea of matter? What is the present idea? Is this necessarily the true idea? Explain.

7. Define an element. How many are known? How many are liquids? Solids? How many constitute nearly the whole of the earth? What two are the most abundant?

8. What is a compound? Name two and give composition. Explain what is meant by chemical union. Illustrate.

9. What is the general plan of naming compounds? Give the signification of the endings ide and ate. Give illustrations.

10. Into what two classes are elements divided? Will copper and silver unite to form a compound? Give reason for your answer.

11. How can one learn experimentally whether an element belongs to one class or the other? Give meaning of the terms anode and cathode. What synonyms are sometimes used?

12. Name three kinds of chemical changes. Give illustration of each. Show how the third may be regarded as a combination of the other two.

13. How does a mixture differ from a compound? Name two mixtures and give some easy way of separating them.

Chapter II

Forms of Appearance Characteristics of Pure Water Water in the Human Body and Foods Necessity of Water to the Body Proof of Composition

(a) By Electrolysis

(6) By Weight Law of Definite Proportions Water of Combination

Hydrates Efflorescence Deliquescence Domestic Water Supplies City Water Supplies Hydrogen Peroxide Law of Multiple Proportions

1. Its Familiarity. — Water is at once the most familiar of all natural substances and one of the most interesting. It appears in a very large variety of forms, all more or less familiar: in partially condensed vapor as fog; in the feathery cirrus cloud: the billowy cumulus, the beautiful summer cloud ; the stormy and threatening nimbus. In the solid form as snow. hail. ice. glaciers and icebergs.

2. Characteristics of Water. — Pure water is tasteless, odorless and colorless, except in great depths as lakes and seas, when it appears blue or bluish green. It is often said that distilled water tastes flat, but this is because we are accustomed to drinking water somewhat impure. Just as beans or potatoes or other vegetables served without salt would taste flat so does water without the usual impurities. Pure water when evaporated leaves no residue, hence would form no incrustation on the inside of kettles or boilers.

3. Water in the Human Body. — Not only does water appear in such variety of form and such quantities in nature, but it constitutes a very large proportion of the animal body. Only about 40 per cent of the human body is solid matter, while in the lower animals the percentage of water is much higher. Our foods are also high in water content. Even butter and flour, which we often think of as dry, contain as much as 12 to 14 per cent of water for the former, and 10 to 11 for the latter. The following table will give an idea as to many of the common food products:

Table

Per cent

Beans, dry , 12.60

Beans, string 89.00

Cabbage 91.50

Carrots 88.20

Cauliflower 92.30

Celery 94.50

Corn, dry 13.12

Flour, wheat 10.11

Meat, lean beef 67.00-70.00

Meat, lean pork 60.00

Meat, veal 73.30

Mutton 50.20

Oat Meal 12.37

Peas, dry 12.62

Peas, green 79.93

Potatoes, sweet 75.00

Potatoes, white 66.10-S0.60

Turnips 89.60

Watermelons 92.40

4. Value of Water to Animals and Plants. — Nothing need be said about the value of water in the household. Life itself is impossible without it. to say nothing of the comfort it brings. Digestion is merely a process by which solid foods are made soluble that they may be carried through the blood to all parts of the body. As water is the most nearly universal solvent it enters largely into the process of digestion. Assimilation of food is impossible in the absence of water; and not only is this true, but most of the waste matter of the body is carried away dissolved in water or mixed with it in large amounts. On account of its high specific heat, that is. a given amount of water contains more heat energy than the same weight of any other liquid at the same temperature, it is regarded as the best means of wanning houses in severe weather. It is this very fact that tempers the winters in the Great Lake regions and along the oceans, and renders the climate of countries washed by the Gulf Stream and Japan Current far warmer than other countries in the same latitude not thus favored. In the human body, the blood, largely water, in constant circulation, tends to keep the body of perfectly uniform temperature. In summer, the body is cooled by the rapid evaporation of the water in the blood through the pores of the skin: thus, summer and winter, the water in the body serves to keep a uniform temperature throughout. To maintain the supply thus needed, an ordinary person requires from two to three pints of water per day. in summer more than in cold weather. Plants, likewise, must have water to enable them to absorb the necessary substances of food value from the soil, as also, to make the cellulose, starch and sugar, which they store up in their stems, seeds and fruits.

5. Composition of Water. — By volume, water is composed of hydrogen, two parts, and oxygen, one part. This is usually shown experimentally by the Hoffman apparatus (Fig. 4). R is a reservoir into which the water is poured in filling the apparatus. It is necessary to use water slightly acidulated with some acid, as sulphuric, since pure water is not a conductor of electricity. In filling the side tubes, B, B, the stop-cocks are carefully opened, one at a time, and the water allowed to flow in until it barely reaches the stop-cock level.

Fig. 4. — Electrolysis or Hoffmann apparatus.

Not much more should be put into R than will fill the three tubes, for a small amount of water makes a large quantity of gas and this forces the excess back into the reservoir, hence room must be left to receive it. Platinum strips, A, A, serve as electrodes and are connected with the source of current by means of wires sealed in glass tubes passed through the corks, C, C. When everything is ready the current is turned on ; bubbles immediately begin to rise from both electrodes, much faster from the cathode than the anode. After a few moments the quantity of gas in each tube may be read from the graduations etched on the tubes, B, B. It Avill be found that the quantity of one gas is always 'double that of the other. To know that the smaller volume is oxygen, hold a splinter with a spark on the end over the tip of the tube and carefully open the stopcock. The pressure of the water in R will force the gas out and ignite the splinter. This characteristic test for oxygen has been mentioned in the preceding chapter. The usual method of testing hydrogen is by lighting it. A burning match or better, a small candle, brought to the tip of the tube containing the larger quantity of gas, will ignite it when the stop cock is cautiously opened. The flame at first will be invisible, or until the glass becomes red-hot; but a piece of paper held to it will be instantly ignited, thus showing the presence of a flame.