A textbook of chemistry for nurses

Front matter

^ V

OCT

*o o* k*

Preface

The science of chemistry enters into every phase of everyday life. Whether it be on the battle front where the chief aim is the wholesale destruction of human life, or at the rear in the hospital tent where it is the loving duty of the nurse to save life and woo back the wasting strength, chemistry is a potent factor. No day of our lives, whether we be the humble laborer, or the exalted magistrate who must direct the destiny of millions, can be spent without a knowledge of chemistry on the part of some one contributing to our safety and welfare. This little book has been prepared, therefore, with the idea of more fully equipping those whose angelic visitations and watchful care must inevitably wield an ever increasing influence upon unfortunate humanity.

The book is very simply written so that all may understand. It begins with the most familiar substances of life and leads up to those not so well known. The author has aimed at all times to avoid the technical: chemical theory has been introduced when such would add greatly to the understanding of the phenomena at hand: at other times it has been omitted. The author has aimed at all times to be scientific and truthful. The practical phases of chemistry are everywhere remembered and emphasized, especially those that concern the great mass of humanity. Those substances which by their applications become our daily servitors, and those which, on the contrary, would threaten and endanger life, have been introduced and studied care-

10 PREFACE

fully. A variety of tables has been added near the end of the book as an appendix. The author feels that these will be both valuable and helpful in many ways, as they give, in a concise form, information often needed quickly. No apology is made for the fact that the text is considerably larger than most of those offered up to this time. The responsibilities of the nurse are so great and the opportunities for the alleviation of suffering are so abundant that a wide knowledge of the Queen of Sciences can never come amiss. It is hoped that this book may be found a source of real help and inspiration.

Fredus N. Peters.

Kansas City, Mo.

Introduction

1. Matter, Old Theories of.

2. Transmutation of Matter.

3. False Methods of Reasoning —

Aristotle, Geber, Paracelsus.

4. Robert Boyle's theories.

5. Elements.

6. Compounds.

(a) Method of Naming.

(b) Parts of Compounds.

(c) Chemical Affinity, What?

7. Mixtures.

8. Chemical Union, What?

9. Chemical Change.

(a) Additive.

(b) Simple Decomposition.

(c) Metathesis or Double Decomposition. Exercises for Review.

1. Some Old Ideas About Matter. — From very early times, certain philosophers have regarded earth, air, fire, and water as the four fundamental or primary substances from which everything we know can be made. Not merely did they believe these four the basis of everything ; but, more than this, they felt sure it was possible to change one or more into another. For example, when a vessel of water is heated upon a stove or allowed to stand in the sun, the water disappears. "We say it evaporates: they thought that it had been changed by the heat into air, or in other words, that heat added to water produces air.

Again, when a tumbler of ice water is left sitting in a warm room, in a short time drops of moisture appear upon the outside of the glass. We say that the moisture in the air has been condensed upon the cold surface; the old philosophers thought as heat had converted the water into air, so cold had changed the air back into water.

When pure water is evaporated, it leaves no residue; but impure or hard water under like conditions leaves more or less of a sediment upon the walls of the containing vessel. This appears as "lime" or "scale" upon the inside of the tea kettle in the kitchen, or in the hot-water coil in the furnace, or in the boiler of the steam engine. We understand what this is ; but the ancient philosophers thought that while by heat the greater part of water changes into air a small portion becomes earth. So according to their reasoning there was a very close relation existing among the four primary substances, and it was no difficult matter to change one into another.

2. Other Obse'rvations. — The old philosophers had observed other facts also which led them to believe in the transmutation of one substance into another. For example, their picks and other steel tools, left standing for a few days in the water which gradually seeped into their copper mines, always became coated with a thin layer of copper. This may be illustrated by immersing a bright nail in a dilute solution of copper sulphate for a few minutes. They had no true knowledge of what

INTRODUCTION IT

was happening, but believed the iron was being changed into copper. They knew also, that by fusing copper with a certain mineral, called cadmia, Avhich we now know contains zinc, they could obtain a substance we call brass, which may closely resemble gold. They knew it was not gold, but they believed that if they could but discover exactly the proper proportions to put together they would succeed in producing the more valuable metal, as good as any from nature's best mine. This change may be further illustrated by putting a few copper cents into a solution of mercuric nitrate and allowing them to remain a few minutes. Upon removing and rubbing them for a moment they seem to have become silver. It is not strange, therefore, that they should have believed in the transmutation of the metals and that the chief aim of the chemist of the alchemistic era was the preparation of gold from the baser metals.

3. Old Methods of Reasoning. — Aristotle, born 384 b. c, one of the greatest of ancient philosophers, once proclaimed that "a globe full of ashes or sand will hold as much water as if empty." Such was the manner of thought of that day that no one for centuries presumed to question the statement. At the present time no scientist would dare publish anything as fact which he did not feel sure was based upon a large number of careful and accurate experiments. Any scientific statement now as soon as published is subjected by scores of scientists to the most rigid tests, so that a few weeks or months at the outside demonstrate the truth or falsity of the position. Not so in Aristotle's time. The very fact that he had stated the proposition was sufficient, and no one even thought of making the experiment, simple as it was, to determine whether the assertion were true.

Twelve hundred years later, Geber, the great Arabian chemist whose doctrines were spread throughout Europe after the Saracen invasion of Spain, declared that all the metals were but different mixtures of mercury and sulphur; that silver and gold were especially rich in mercury and the baser metals were abounding in sulphur. It seems that Geber was somewhat of an experimenter and was forced to admit to himself, at least, though he never did to the public, that the mercury and sulphur as he knew them in the laboratory would not bring about such results as his theory maintained; further that the mercury and sulphur in the free state were not identical with what he described as the same in combination: yet, in spite of all this, he never admitted the inaccuracy or falsity of his theory. Furthermore, his disciples all over Europe, accepted his doctrines with equally unquestioning faith as had those of Aristotle during all the preceding centuries.

Five hundred years passed away and with them the age of alchemy. The first half of the sixteenth century introduces a new school of chemists, the physician chemists, or iatrochemists, as they are generally known. Of these, Philippus Aureolus Paracelsus Theophrastus Bombastus, or, as he is usually called, Paracelsus, was easily the leader. He maintained that "Man is a chemical compound. His ailments are due to some alteration in his composition and can only be cured by the influence of other chemical compounds. ' ' His belief that the body is composed of mercury, sulphur and salt, it will be readily seen, was but a modification of the ideas of Geber. An increase of sulphur in certain organs of the body caused fever; of mercury, paralysis; of salt, diarrhea and dropsy. Too little sulphur resulted in gout ; and so on, for all the ills of mankind. With this theory accepted

INTRODUCTION 19

as the truth, it was but a short step to the giving of calomel for a great variety of ailments, presumably with the assumption that the digestive organs with more discretion than the mind would send the mercury to those organs most in need of it. Here, too, undoubtedly, began the use of sulphur so extensively as a medicine, which in the practice of Paracelsus met with such wonderful results that even the sceptical nineteenth century did not succeed entirely in stopping.

4. Modern Ideas. — In time, however,, all this passed away. Robert Boyle, born in 1626, expressed disbelief in the four elements of the ancients as well as in the one, to which some held, and declared there were many primary substances to which he gave the name of elements. Furthermore by his own example he emphasized the truth which had been dawning for years upon the scientific world that only through experiment can absolute scientific knowledge be determined. Such was his influence that he is often called the "Father of Physics and Chemistry."

With the birth of new ideas as to the composition of matter and a disbelief in the transmutation of the metals, medicine and chemistry became separate sciences, each imbued with the spirit of making sure by experiment of any position taken. Today, medicine no less than chemistry permits of no dogmatic theory as to disease. If a new scourge appears as did yellow fever some years ago, numbers of young physicians are ready to offer their lives, if need be, to learn the true cause ; the x-ray reveals to the surgeon the exact condition of the broken bone or the location of the bullet for which he must search; it shows the ulceration at the base of the tooth or other abnormal conditions and renders sure the operation. In the laboratory culture the microscope shows the tubercle bacilli or the diphtheria germ as well as various others. So, in countless ways the modern physician makes sure of his diagnoses, after which proper treatment is comparatively simple.

5. What is an Element? — An element in the sense in which Boyle used the term and as used at the present time is a substance which consists of a single kind of matter, hence is not capable of being reduced to anything simpler. There are now known a few more than eighty of these simple substances, but it is possible that some of the rarer of them may not be really elements. It is probable also that others may be added to those already known. Some of the commoner ones are the metals, gold, silver, lead, mercury, aluminum, etc. and oxygen, nitrogen, hydrogen, carbon, sulphur and chlorine.

6. Compounds. — A compound is a substance containing two or more elements chemically united, always in exactly the same proportion by weight. For example, water is a compound, consisting of eight parts of oxygen and one part of hydrogen, from which proportions it never varies.

Compounds, How Named. — Chemists have agreed upon and rigidly adhere to a plan of naming compounds in such a way as to indicate the composition as nearly as possible. Thus mercuric oxide is a compound which contains only mercury and oxygen; any compound whose name ends in ide contains only the elements named, and with the exception of hydroxides, contains only two elements. Thus, potassium chloride contains potassium and chlorine; magnesium bromide, magnesium and bromine; while sodium hydroxide contains sodium, hydrogen and oxygen. If the name of a compound ends in ate the fact is indicated that it contains oxvgen in addition to the two other elements mentioned.

INTRODUCTION 21

Thus, potassium chlorate contains potassium, chlorine and oxygen: copper sulphate, copper, sulphur and oxygen.

Parts of a Compound. — It is well known that a magnetic needle, suspended by a thread or upon a pivot, always points approximately north and south. AYe often speak of the two ends of the magnet as the positive pole and the negative pole. In an electric circuit, the electrode where the current enters is called the anode, or positive electrode, and the one where it exits, the cathode, or negative electrode. Of course the terms, positive and negative have no real meaning and are used merely for convenience in referring to certain portions of the circuit. Anode and cathode mean, respectively, the path or road in and the road out. Furthermore, it is well known that the positive pole of a magnet always repels the positive pole of another magnet, but attracts the negative pole: from this fact is derived the law stated in physics that "Like poles repel, and unlike poles attract."

Generally speaking, the eighty elements mentioned above may be roughly divided into two groups, positive and negative. This fact grows out of the law stated just above and shown by the following experiment. If a solution of common salt, sodium chloride, is subjected to the passage of an electric current, the sodium always goes to the negative electrode and the chlorine to the positive: likewise in a solution of potassium bromide, the potassium will be found collecting at the negative electrode and the bromine at the other. Experiments upon compounds of all the elements show like results, hence the statement at the beginning of this paragraph. In the main the so-called metals are positive and the nonmetals are negative. Furthermore, in the study of compounds we find that as a general rule they all consist of a positive and a negative element, or group, united with each other. Thus, sodium chloride contains sodium, positive, and chlorine, negative ; potassium sulphate, positive potassium, and negative, the group sulphur and oxygen, which will be more fully explained later. It would seem, therefore, that the force which holds elements together in a compound is electrical in nature. In fact, the expression "chemical affinity" used so often in times past has no real meaning and is seldom used now. One more thing should be observed by the student and that is that in writing or reading the name of a compound the positive part is always given first as a general rule. Thus, chromium nitrate may be a compound entirely unknown to the student, yet from the fact just stated, he may know that chromium is the positive element in the compound and the negative portion is the group containing nitrogen and oxygen.

7. Mixtures. — Mixtures are different from compounds in that the two or more substances of which they are composed are not chemically united and are not necessarily in any fixed or definite proportion. Thus, brass is a mixture of zinc and copper in greatly varying proportions. It may contain 65 per cent of zinc and 35 per cent of copper or it may run as low as 5 per cent of zinc and the remainder of copper, with variations all the way between these limits, according to the purpose in view. The air, likewise, is a mixture, mainly of five substances; two of them, nitrogen and oxygen, are always nearly in the same proportion, so nearly in fact, that for many years they were regarded as being combined, but later more accurate measurements showed that even these two vary at different times and places Further, in another chapter it will be shown that there

INTRODUCTION . 23

are excellent reasons for assuming that they are not chemically united.

8. What is Chemical Union? — The expression "chemically united" has been used several times in the preceding paragraph. By it is meant that two or more elements in uniting chemically form a new substance, having properties essentially different from those of the original elements, while they lose their individual identities. Thus, water was said to consist of hydrogen and oxygen: at ordinary temperatures these are both gases, one very highly inflammable, the other necessary for all ordinary combustion. When chemically united, the resulting product is a liquid at ordinary temperatures, not combustible like the hydrogen, not an aid to combustion like oxygen. In uniting chemically the two elements have lost their individual characteristics and have formed a substance altogether different from either. To illustrate again, sodium is a silvery white metal, lighter than water which it decomposes rapidly and which in the mouth or upon the wet hand would readily catch fire and produce most serious chemical burns. Chlorine is a heavy, yellow, corrosive gas, used in the World War as a terribly destructive agent: combine these two poisonous elements and we have common salt, used daily in our food and in moderate amounts perfectly harmless. In combining, each element has lost its destructive properties and formed a substance of the greatest commercial value.

9. Chemical Change'. — A chemical change is one in which the substances used, one or more, are destroyed as such; new substances are formed with entirely different properties. Chemical union, explained in the preceding paragraph, is but one kind of chemical change. Such as those mentioned, the union of hydrogen and oxygen to form water or of sodium and chlorine to form salt, are called additive reactions; that is, the two or more substances have simply been combined to form one new substance. An experiment easily made to illustrate this kind of chemical change is that of burning a feAV inches of magnesium ribbon. The steel gray metal rapidly combines with the oxygen of the air and produces magnesium oxide, commonly known as magnesia.

A second kind of chemical change is called simple decomposition which is just the reverse of an additive reaction. A single substance by heat or some other force is decomposed forming usually two simpler substances When a current of electricity is passed through water, it is decomposed into its constituents, hydrogen and oxygen. Again, if a small quantity of mercuric oxide is heated in a test tube, in a short time mercury will be seen gathering upon the sides of the test tube while the presence of oxygen at the mouth of the tube may be shown by its causing a glowing pine splinter held just above to burst into a flame.

A third kind of chemical change is known as metathesis, or double decomposition. It is the mutual decomposition of two reacting substances, resulting in the formation of two entirely new substances. For example, if a small quantity, say about a gram each, of mercuric chloride and of potassium iodide be rubbed together in a mortar, almost immediately the white mixture begins to turn pink and increases in color as the rubbing proceeds. The very fact that two white compounds put together produce a red one indicates something more than mere mixing has occurred. No two white paints could be mixed together to produce a red pigment. What really has happened is this: the two metals, potassium and mercury, being of positive character, as suggested in a preceding paragraph, have

INTRODUCTION 25

exchanged places with each other forming two new compounds, mercuric iodide and potassium chloride, one of which is a brilliant red.

In the study of chemistry we are dealing much of the time with chemical changes most of which will fall under one of the three kinds just mentioned. Some will be of a mixed character, partaking of the nature of two of the kinds mentioned.

1. Name the four substances regarded by ancient philosophers as primary.

2. Give some evidence they offered for such belief. Why did they assume one of these could be transformed into another?

3. What led them to believe the metals could be transmuted? What is meant by transmutation of metals?

4. What was the method of scientific reasoning in Aristotle's day? Illustrate. Who was Geber? What was one of his theories?

5. Who was Paracelsus? What was his idea about the human body? Of disease?

6. "Who was the father of physics and chemistry? What was his idea about matter?

7. What is an element? How many are there?

8. W T hat is a compound? Name two.

9. How may you know from the name the composition of a compound? Illustrate.

10. What is a magnet? Pole of a magnet?

11. What is meant by anode? Cathode?

12. Into what two groups may the elements be divided? Why so divided?

13. What force apparently holds elements together in a compound? What is chemical affinity?

14. How is a mixture different from a compound?' Illustrate.

15. What is meant by chemical union? Illustrate.

16. What is a chemical change?

17. Name three kinds of chemical change. Give some experiment to illustrate each.

18. Define each kind of chemical change.

Chapter II

1. Water, Abundance, Various Forms.

2. Water in Food Products.

3. Composition of Water — Proof.

(a) By Electrolysis — Volumetric.

(b) By Synthesis — Gravimetric.

4. Deliquescence.

(a) Definition and Illustration.

(b) Hygroscopic substances.

5. Water of Combination — Hydrates.

6. Efflorescence.

7. Solvent Powers' of Water.

(a) Hard Waters.

(b) Water Supplies.

8. Nature's Method of Purification.

9. City Water Systems.

(a) Sewage in.

(b) Methods of Treatment.

(c) Treatment for Algae.

10. Tests for Water.

Exercises for Eeview.

1. Abundance. — Water in its various forms is so familiar to every one that little need be said of its abundance. As a liquid and in a partially condensed form of steam, fog, and cloud it is known to all; while as ice and snow, glaciers and icebergs, it is known only in middle and northern latitudes.

2. Water in Food Products. — Practically all our foods contain a greater or less amount of water. Even flour, which might be thought of as entirely free from water contains a very considerable amount, averaging in different samples about ten or eleven per cent.

Table

Per cent

Beans, dry 12.60

Beans, string, 89.00

Bread, yeast 36.12 to 37.70

Cabbage 91.50

Carrots 88.20

Cauliflower 92.30

Celery 94.50

Flour, wheat 10.11

Meat, lean beef 67.00 to 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 to 80.60

Turnips 89.60

Watermelons 92.40

Likewise, all fresh fruits run high in water, their chief food value being in the sugar they contain, in addition to the organic acids probably of special value in their effects upon the digestive system. Naturally, therefore, the human body itself is largely water, it being estimated that in the case of a man weighing 150 pounds the amount of solid matter would be about sixty pounds.

3. Composition of Water. — As already stated, water was regarded by the ancient philosophers as one of the primary substances; but we know now that it is a compound, consisting, by volume, of hydrogen, two thirds, and oxygen, one third. Proof of this is usually made by means of what is known as the Hoffmann apparatus, shown in Fig. 1. A and K are two platinum strips serving as the electrodes and connecting with the electric circuit by means of wires enclosed in glass tubes passed through the corks C,C, which close the

Fig 1. — Electrolysis apparatus.

apparatus at the bottom. S,S are stopcocks by means of which the gases may be drawn off at the close of the experiment and tested. B is a reservoir to receive the excess of water from the electrolytic tubes, B,B. In making the experiment, water slightly acidulated with sulphuric acid is poured into the central tube, or reservoir, and the stopcocks opened to allow the water to just barely fill the tubes, B,B, up to the stopcocks. A suitable, direct current is then switched on and allowed to flow until a sufficient amount of gas has collected for testing. Readings taken on the graduated tubes at any time show twice as much gas in one as the other. To prove that the gases are hydrogen and oxygen the following tests may be made which it will be found later are the usual ones. Over the tip of the tube containing the lesser amount of gas, hold a pine splinter with a spark upon the end of it; open the stopcock cautiously and allow the gas to flow out upon the spark: it immediately bursts into a flame. This may be repeated several times, until the gas is exhausted. To test the other tube, with a match or small candle, which is better, light the gas which flows out upon opening the stopcock ; it will burn with an almost invisible flame, which is characteristic of hydrogen.

It will be found that in the electrolysis of water as outlined above the hydrogen always goes to the cathode and the oxygen to the anode. The reason for this is plain when we remember what was said about every compound in the preceding chapter, that is, that it consists of a positive and a negative element or group. Hydrogen belongs to the positive elements and oxygen to the negative, hence obeying the law previously stated they would be attracted, the former to the negative electrode and the latter to the positive.

Composition by Weight. — By the electrolysis of water as just given we learn its composition by volume. It is even more important to know what it is by weight. This may be readily determined by a simple experiment as follows:

In Fig. 2, K is a generator for the preparation of hydrogen; W is a wash bottle containing sulphuric acid for the purpose of thoroughly drying the hydrogen ; T is a combustion tube made of hard glass containing copper oxide, preferably in what is known as "wire form ; ' ' TJ is a U-tube containing calcium chloride, a substance which rapidly absorbs water ; B is a Bunsen burner or some other source of heat. Before beginning the experiment several grams of copper oxide are placed in the combustion tube and both together weighed ; next the calcium chloride tube is nearly filled and weighed. Heat is then applied and the current of hydrogen turned on, slow at first. Soon the black oxide will be noticed turning red like bright copper and this will continue till the whole mass has thus changed. At the' same time

Fig. 2. — Synthesis of water.

water will be noticed collecting in the U-tube. At this stage the heat is removed but the gas is allowed to continue till the copper oxide tube has become nearly cool. The apparatus is then disconnected and second weighings made. The following weights may be taken as representing a typical case.

Copper oxide tube, before heating 35.29 grams

after heating 28.81 < '

Loss, which is oxygen 6.48 ' '

Calcium chloride tube, before heating 27.34 grams

after heating 34.63 ' <

Gain, which is water 7.29 tl

Subtracting the weight of the oxygen from that of the water leaves 0.81 grams, which is the weight of the hydrogen used in forming the water. It will be observed that this weight is one eighth that of the oxygen or one ninth that of the water formed. Owing to experimental errors the results are not usually exact, but the average of a very large number of experiments more carefully carried out than can be done in the ordinary class room shows conclusively that the above conclusions are correct.

4. Deliquescence. — Deliquescence is the property some substances possess of absorbing water from the air when exposed and of becoming liquid. Nearly everything absorbs some moisture when exposed to the air, but a few substances do this to a remarkable degree as indicated in the definition of deliquescence just given. Literally translated the word means "becoming liquid." An excellent example of such compounds is seen in calcium chloride used in the experiment outlined in the preceding paragraph. Other well-known deliquescent compounds are caustic soda and potash and phosphorous pentoxide. A hygroscopic substance is one that will become damp upon exposure to the air, but will not absorb sufficient water to become a liquid. Most samples of table salt become damp in wet weather due, however, to the presence of an impurity in the salt rather than to the salt itself being hygroscopic.

5. Water of Combination — Hydrates. — Many chemical compounds occur in regular geometric shapes which are called crystals, such as cubes, octahedrons, rhombohedrons, etc. These crystals are more often obtained by making a solution of the substance in water and evaporating. In such cases it is often true that a very considerable portion of the water, instead of passing off into the air, goes into combination with the solid. Water thus taken up is called water of combination or often, though less properly, water of crystallization. This water is not simply mixed with the solid: if it were, it might be removed by pressure or absorption by a piece of blotting paper. On the other hand, it is far from a stable chemical union, for usually comparatively little heat will more or less completely remove it. That there is real chemical union, however, is known from the fact that when the water is removed the properties of the substance are often materially changed. Such substances as these are now called hydrates. Some good examples of crystalline hydrates are blue vitriol, alum, green vitriol, sal soda, borax and many other familiar compounds.