CHEMISTRY AND ALCHEMY—CHEMICAL COMBINATIONS—THE ATMOSPHERIC AIR.

We have in the foregoing pages given some experiments, and considered several of the metals, but there are numerous very interesting subjects still remaining; indeed, the number is so great that we can only pick and choose. All people are desirous to hear something of the atmosphere, of water, and the earth; and as we proceed to speak of crystals and minerals, and so on to geology, we shall learn a good deal respecting our globe—its conformation and constituents. But the atmospheric air must be treated of first. This will lead us to speak of oxygen and nitrogen. Water will serve to introduce hydrogen with a few experiments, and thus we shall have covered a good deal of ground on our way towards various other elements in daily use and appreciation. Now let us begin with a few words concerning Chemistry itself.

At the very outset we are obliged to grope in the dark after the origin of this fascinating science. Shem, or “Chem,” the son of Noah, has been credited with its introduction, and, at any rate, magicians were in Egypt in the time of Moses, and the lawgiver is stated by ancient writers to have gained his knowledge from the Egyptians. But we need not pursue that line of argument. In more modern times the search for the Philosopher’s Stone and the Elixir of Life, which respectively turned everything to gold, and bestowed long life upon the fortunate finder, occupied many people, who in their researches no doubt discovered the germs of the popular science of Chemistry in Alchemy, while the pursuit took a firm hold of the popular imagination for centuries; and even now chemistry is the most favoured science, because of its adaptability to all minds, for it holds plain and simple truths for our every-day experience to confirm, while it leads us step by step into the infinite, pleasing us with experiments as we proceed.

Alchemy was practised by numerous quacks in ancient times and the Middle Ages, but all its professors were not quacks. Astrology and alchemy were associated by the Arabians. Geber was a philosopher who devoted himself entirely to alchemy, and who lived in the year 730 A.D. He fancied gold would cure all disease, and he did actually discover corrosive sublimate, nitric acid, and nitrate of silver. To give even a list of the noted alchemists and magicians would fill too much space. Raymond Sully, Paracelsus, Friar Bacon, Albertus Magnus, Thomas Aquinas, Flamel, Bernard of Treves, Doctor Dee, with his assistant Kelly, and in later times Jean Delisle, and Joseph Balsamo (Cagliostro), who was one of the most notorious persons in Europe about one hundred years ago (1765-1789), are names taken at random; and with the older philosophers chemistry was an all-absorbing occupation—not for gold, but knowledge.

The revelation was slow. On the temperature of bodies the old arts of healing were based—for chemistry and medicine were allies. The elements, we read, existed on the supposition “that bodies were hot or cold, dry or moist”; and on this distinction for a long time “was based the practice of medicine.” The doctrine of the “three principles” of existence superseded this,—the principles being salt, mercury, and sulphur. Metals had been regarded as living bodies, gases as souls or spirits. The idea remained that the form of the substance gave it its character. Acid was pointed; sweet things were round.

Chemistry, then, has had a great deal to contend against. From the time of the Egyptians and Chinese, who were evidently acquainted with various processes,—dyeing, etc.,—the science filtered through the alchemists to Beecher and Stahl, and then the principle of affinity—a disposition to combine—was promulgated, supplemented in 1674 by Mayow, by the theory of divorce or analysis. He concluded that where union could be effected, separation was equally possible. In 1718 the first “Table of Affinities” was produced. Affinity had been shown to be elective, for Mayow pointed out that fixed salts chose one acid rather than another. Richter and Dalton made great advances. Before them Hales, Black, Priestley, Scheele, Lavoisier, and numerous others penetrated the mysteries of the science whose history has been pleasantly written by more than one author who we have not been able to consult, and have no space to do more than indicate. In later days Faraday, De la Rive, Roscoe, and many others have rendered chemistry much more popular, while they have added to its treasures. The story of the progress of chemistry would fill a large volume, and we have regretfully to put aside the introduction and pass on.

Before proceeding to investigate the elements, a few words concerning the general terms used in chemistry will be beneficial to the reader. If we look at the list of the elements, pp. 308-9, we shall see various terminations. Some are apparently named from places, some from their characteristics. Metals lately discovered by the spectroscope (and recently) end in ium; some end in “ine,” some in “on.” As far as possible in late years a certain system of nomenclature has been adhered to, but the old popular names have not been interfered with.

When elements combine together in certain proportions of each they receive certain names. The following table will explain the terms used ; for instance, we find that—

The above examples refer to the union in single proportion of each, and are called Binary Compounds. When more than one atom of each element exists in different proportions we have different terms to express such union. If one atom of oxygen be in the compound it is called a “monoxide” or “protoxide”; two atoms of oxygen in combination is termed “dioxide” or “binoxide”; three, “trioxide,” or “tritoxide”; four is the “tetroxide” or “per-oxide,” etc. When more than one atom, but not two atoms is involved, we speak of the sesqui-oxide (one-and-a-half),—“oxide” being interchangeable for “sulphide” or “chloride,” according to the element.

There are other distinctions adopted when metals form two series of combinations, such as ous and ic, which apply, as will be seen, to acids. Sulphuric and sulphurous acids, nitric and nitrous acid are familiar examples. In these cases we shall find that in the acids ending in “ous” oxygen is present in less quantity than in the acids ending in ic. The symbolic form will prove this directly, the number of atoms of oxygen being written below,

Sulphurous Acid = H₂ SO₃
Nitrous Acid = HNO₂.
Sulphuric Acid = H₂SO₄.
Nitric Acid = HNO₃.

Whenever a stronger compound of oxygen is discovered than that denominated by ic, chemists adopt the plan of dubbing it the per (?p?? over), as per-chloric acid, which possesses four atoms of oxygen (HClO₄), chloric acid being HClO₃. The opposite Greek term, ?p? (hupo, below), is used for an acid with less than two atoms of oxygen, and in books is written “hypo”-chlorous (for instance). Care has been taken to distinguish between the higher and lower; for “hyper” is used in English to denote excess, as hyper-critical; and hypo might to a reader unacquainted with the derivation convey just the opposite meaning to what is intended.

While speaking of these terminations we may show how these distinctive endings are carried out. We shall find, if we pursue the subject, that when wehave a salt of any acid ending in ic the salt terminates in “ate.” Similarly the salts of acids ending in ous, end in “ite.” To continue the same example we have—

Sulphurous Acid, which forms salts called Sulphites.
Sulphuric Acid, which forms salts called Sulphates.

Besides these are sulphides, which are results of the unions or compounds of elementary bodies. Sulphites are more complicated unions of the compounds. Sulphates are the salts formed by the union of sulphuric acid with bases. Sulphides or sulphurets are compounds in which sulphur forms the electro-negative element, and sulphites are salts formed by the union of sulphurous acids with bases, or by their action upon them.

The symbolical nomenclature of the chemist is worse than Greek to the uninitiated. We frequently see in so-called popular chemical books a number of hieroglyphics and combinations of letters with figures very difficult to decipher, much less to interpret. These symbols take the place of the names of the chemical compounds. Thus water is made up of oxygen and hydrogen in certain proportions; that is, two of hydrogen to one of oxygen. The symbolic reading is simple, H₂O, = the oxide of hydrogen. Potassium again mingles with oxygen. Potassium is K in our list; KO is oxide of potassium (potash). Let us look into this a little closer.

The union of one particle of a simple body with a particle of another simple body can be easily understood; but, as we have seen, it is possible to have substances consisting of four or five different particles, though the greater number of chemical combinations consist of two or three dissimilar ones. In the diagram (fig. 322) we have some possible combinations.

In these combinations we may have one particle of a in combination with one, two, three, four, or five of b, and many particles of a can unite with various molecules of b. Suppose we have oxygen and sulphur compounds as follows:—

Thus there are three different compounds of these two elements—SO, SO₂, SO₃ (without water).

A compound body may combine with another compound body, and this makes a complicated compound. Suppose we have a mixture of sulphuric acid and potash. We have a sulphate of potassium (K₂SO₄) and combinations of these combinations may likewise be formed. We must read these symbols by the light of the combining weights given in the table, and then we shall find the weight of oxygen or other elements in combination. Thus when we see a certain symbol (Hg.S for instance), we understand that they form a compound including so many parts of mercury and so many of sulphur, which is known as vermilion. Hg.O is oxide of mercury, and by reference to the table of Atomic Weights, we find mercury is Hg., and its combining weight is 200; while oxygen is O, and its weight is 16. Thus we see at once how much of each element is contained in oxide of mercury, and this proportion never varies; there must be 200 of one and 16 of the other, by weight, to produce the oxide. So if the oxygen has to be separated from it, the sum of 216 parts must be taken to procure the 16 parts of oxygen. When we see, as above, O₂ or O₃, we know that the weight must be calculated twice or three times, O being 16; O₂ is therefore 32 parts by weight. So when we have found what the compounds consist of, we can write them symbolically with ease.

Composition of the Atmospheric Air.

We have already communicated a variety of facts concerning the air. We have seen that it possesses pressure and weight. We call the gaseous envelope of the earth the atmosphere, and we are justified in concluding that other planets possess an atmosphere also, though of a different nature to ours. We have seen how easy it is to weigh the air, but we may repeat the experiment. (See illustration, fig. 45, page 50.) We shall find that a perfectly empty glass globe will balance the weights in the scale-pan; admit the air, and the glass globe will sink. So air possesses weight. We have mentioned the Magdeburg hemispheres, the barometer, the air-pump, and the height and the pressure of the atmosphere have been indicated. The density of the atmosphere decreases as we ascend; for the first seven miles the density diminishes one-fourth that of the air at the sea-level, and so on for every succeeding seven.

In consequence of the equal, if enormous, pressure exercised in every direction, we do not perceive the inconvenience, but if the air were removed from inside of a drum, the parchment would quickly collapse. We feel the air when we move rapidly. We breathe the air, and that statement brings us to consider the composition of the atmosphere, which, chemically speaking, may vary a little (as compared with the whole mass) in consequence of changes which are continually taking place, but to all intents and purposes the air is composed as follows, in 100 parts:

with minute quantities of other ingredients, such as ammonia, iodine, carbonetted hydrogen, hydrochloric acid, sulphuretted hydrogen, nitric acid, carbonic oxide, and dust particles, as visible in the sunbeams, added.

The true composition of the atmosphere was not known till Lavoisier demonstrated that it consisted of two gases, one of which was the vital fluid, or oxygen, discovered by Priestley. To the other gas Lavoisier gave the name of Azote,—an enemy of life,—because it caused death if inhaled alone. The carbonic acid in the air varies very much, and in close, heated, and crowded rooms increases to a large quantity, which causes lassitude and headache.

We can easily prove the existence of carbonic acid gas as exhaled from the lungs. Suppose we take a glass and fill it partly with clear lime-water; breathe through a glass tube into the water in the glass, and very quickly you will perceive that the lime-water is becoming cloudy and turbid. This cloudiness is due to the presence of chalk, which has been produced by the action of the carbonic acid gas in the lime-water. This is a well known and always interesting experiment, because it leads up to the vital question of our existence, and the functions of breathing and living.

A popular writer once wrote a book entitled, “Is Life Worth Living?” and a witty commentator replied to the implied question by saying, “It depends upon the liver.” This was felt to be true by many people who suffer, but the scientific man will go farther, and tell you it depends upon the air you breathe, and on the carbonic acid you can raise to create heat,—animal heat,—which is so essential to our well-being. We are always burning; a furnace is within us, never ceasing to burn without visible combustion. We are generating heat by means of the blood. We know that we inhale air into the lungs, and probably are aware that the air so received parts with the oxygen to renew the blood. The nitrogen dilutes the oxygen, for if we inhaled a less-mixed air we should either be burnt up or become lunatics, as light-headed as when inhaling “laughing-gas.” This beautifully graduated mixture is taken into our bodies, the oxygen renews the blood and gives it its bright red colour; the carbon which exists in all our bodies is cold and dead when not so vivified by oxygen. The carbonic acid given off produces heat, and our bodies are warm. But when the action ceases we become cold, we die away, and cease to live. Man’s life exemplifies a taper burning; the carbon waste is consumed as the wax is, and when the candle burns away—it dies! It is a beautiful study, full of suggestiveness to all who care to study the great facts of Nature, which works by the same means in all matter. We will refer to plants presently, after having proved by experiment the existence of nitrogen in the air.

Rutherford experimented very cruelly upon a bird, which he placed beneath a glass shade, and there let it remain in the carbonic acid exhaled from its lungs, till the oxygen being at length all consumed by the bird, it died. When the atmosphere had been chemically purified by a solution of caustic potash, another bird was introduced, but though it lived for some time, it did not exist so long as the first. Again the air was deprived of the carbonic acid, and a third bird was introduced. The experiment was thus repeated, till at length a bird was placed beneath the receiver, and it perished at once. This is at once a cruel and clumsy method of making an experiment, which can be more pleasantly and satisfactorily practised by burning some substance in the air beneath the glass. Phosphorus, having a great affinity for oxygen, is usually chosen. The experiment can be performed as follows with a taper, but the phosphorus is a better exponent.

Let us take a shallow basin with some water in it, a cork or small plate floating upon the water, and in the plate a piece of phosphorus. We must be careful how we handle phosphorus, for it has a habit, well known, but sometimes forgotten by amateur chemists, of suddenly taking fire. Light this piece of phosphorus,—a small piece will do if the jar be of average “shade” size,—and place the glass over it, as in the illustration (fig. 325). The smoke will quickly spread in the jar, and the entry of air being prevented, because the jar is resting under water, phosphoric acid will be formed, and the oxygen thereby consumed. The water, meanwhile, will rise in the jar, the pressure of the air being removed. The burning phosphorus will soon go out, and when the glass is cool, you will be able to ascertain what is inside the jar. Put a lighted taper underneath, and it will go out. The taper would not go out before the phosphorus was burnt in the glass, and so now we perceive we have azote in the receptacle—that is, nitrogen. The other, the constituent of our atmosphere, carbonic acid, as we have seen, is very injurious to the life of animals, and as every animal breathes it out into the air, what becomes of it? Where does all this enormous volume of carbonic acid, the quantities of this poison which are daily and nightly exhaled, where do they all go to? We may be sure nature has provided for the safe disposal of it all. Not only because we live and move about still,—and of course that is a proof,—but because nature always has a compensating law. Remember nothing is wasted; not even the refuse, poisonous air we get rid of from our lungs. Where does it go?

It goes to nourish the plants and trees and vegetables that we delight to look upon and to eat the fruit of. Thus the vegetable world forms a link between the animals and the minerals. Vegetables obtain food, so to speak, and nourishment from water, ammonia, and carbonic acid, all compound bodies, but inorganic.

Water consists of oxygen and hydrogen, carbonic acid of carbon and oxygen, and ammonia of hydrogen and nitrogen. Water and ammonia are present in the air; so are oxygen and nitrogen. Water falls in the form of rain, dew, etc. So in the atmosphere around us we find nearly every necessary for plant-life; and in the ground, which supplies some metallic oxides for their use, we find the remainder. From the air, then, the plant derives its life.

The vegetable kingdom in turn gives all animals their food. This you will see at a glance is true. Certainly animals live on animals. Man and wilder animals live on the beasts of the field in a measure, but those beasts derive their nourishment from vegetables—the vegetable kingdom. So we live on the vegetable kingdom, and it separates the carbonic acid from the air, and absorbs it. What we do not want it takes. What we want it gives. Vegetables give out oxygen, and we consume it gladly. We throw away carbonic acid, and the plants take it greedily; and thus the atmosphere is retained pure for our use. We can, if desirable, prove that plants absorb carbonic acid and give out oxygen by placing leaves of a plant in water, holding the acid in solution, and let the sun shine upon them. Before long we shall find that the carbonic acid has disappeared, and that oxygen has come into the water.

Carbonic acid is sufficiently heavy to be poured from one vessel to another; and if we have obtained some in a glass, we can extinguish a taper by pouring the invisible gas on to the lighted taper, when it will be immediately extinguished.

From the foregoing observations it will be perceived how very desirable it is that ventilation should be attended to. People close up windows and doors and fireplaces, and go to bed and sleep. In the morning they complain of headache and lassitude; they wonder what is the matter, and why the children are not well. Simply because they have been rebreathing the carbonic acid. Go into a closed railway carriage which is nearly filled (and it is astonishing to us how people can be so foolish as to close every outlet), and you will recoil in disgust. These travellers shut the ventilators and windows “because of the cold.” A very small aperture will ventilate a railway carriage; but a close carriage is sickening and enervating, as these kind of travellers find out by the time they reach their journey’s end. Air was given us to breathe at night as well as by day; and though from man’s acts or omissions there may be circumstances in which “night” air may affect the health, we maintain that air is no more injurious naturally than “day” air. Colder it may be, but any air at night is “night” air, in or out of doors at night; and we are certain that night air in itself never hurt any healthy person. It is not nature’s plan to destroy, but to save. If a person delicate in constitution gets hot, and comes out into a colder atmosphere, and defy nature in that way, he (or she) must take the consequences. But air and ventilation (not draught) are necessaries of health, and to say they injure is to accuse nature falsely. There are many impurities in the air in cities, and in country places sometimes, but such impurities are owing to man’s acts and omissions. With average sanitary arrangements and appliances in a neighbourhood no one need be afraid to breathe fresh air night or day; and while many invalids have, we believe, been retarded in recovery from being kept in a close room, hundreds will be benefited by plenty of fresh air. We should not so insist upon these plain and simple truths were there not so many individuals who think it beneficial to close up every avenue by which air can enter, and who then feel ill and out of spirits, blaming everything but their own short-sightedness for the effect of their own acts. An inch or two of a window may be open at night in a room, as the chimney register should be always fully up in bedrooms. When there are fires the draught supplies fresh air to the room with sufficient rapidity. But many seaside journeys might be avoided if fresh air were insisted on at home.

There is another and an important constituent of the atmosphere called Ozone, which is very superior oxygen, or oxygen in what is termed the “Allotropic” state, and is distantly related to electricity, inasmuch as it can be produced by an electrical discharge. This partly accounts for the freshness in the air after a thunderstorm, for we are all conscious that the storm has “cleared the air.” The fresh, crisp ozone in the atmosphere is evident. Ozone differs from oxygen in possessing taste and smell, and it is heavier by one-half than the oxygen gas. There is a good deal of ozone in the sea breeze, and we can, though not infallibly, detect its presence by test-paper prepared with iodide of potassium, which, when ozone is present, will turn blue. We have still something to learn about ozone, which may be considered as “condensed oxygen.”

We have frequently mentioned “combustion,” and as under ordinary circumstances such effects cannot take place without atmospheric air, we will consider it. Combustion is chemical action accompanied by light and heat. Chemical union is always attended by the development of heat, not always by light, because the union varies in intensity and quickness. But when a candle is burning we can study all the interesting phenomena of combustion. We have already spoken of Heat and Light, so we need only refer the readers to those subjects in the former parts of this volume. Heat is referable to chemical action, and varies according to the energy of union. Heat is always present, remember, in a greater or less degree; and when visible combustion takes place we see light. Invisible combustion goes on in our bodies, and we feel heat; when we get cold we feed the fire by eating, or blow it by exercise and air in our lungs.

We shall speak, however, of combustion now as it affects us in daily life; our fires, our candles, gas, etc., and under these ordinary circumstances hydrogen and carbon are present. (We shall hear more about carbon presently.) These unite with the oxygen to form water and carbonic acid; the water being visible as we first put the cold shade upon the lighted lamp, and the carbonic acid renders the air impure.

In the case of a common candle, or lamp, combustion takes place in the same way. The wick is the intermediary. The oil mounts in the lamp wick, where it is converted into a gas by heat; it then “takes fire,” and gives us light and heat. The candle-flame is just the same with one exception: the burning material is solid, not liquid, though the difference is only apparent, for the wax is melted and goes up as gas. The burning part of the wick has a centre where there is no combustion, and contains carbon. We can prove this by placing a bent tube, as in the illustration (fig. 326), one end in the unburning part of the flame. We shall soon see a dark vapour come over into the receiver. This is combustible, for if we raise the tube without the glass we can light the gas (fig. 327). If we insert the end of the tube into the brilliant portion of the flame we shall perceive a black vapour, which will extinguish the combustion, for it is a mixture of carbonic acid gas and aqueous vapour, in which (fig. 328) particles of carbon are floating.

When we proceed to light our lamps to read or to write by, we find some difficulty in making the wick burn at first. We present to it a lighted taper, and it has no immediate effect. Here we have oil and cotton, two things which would speedily set a warehouse in flames from top to bottom, but we cannot even ignite them, try all we can. Why?—Because we must first obtain a gas, oil will not burn liquid; it must be heated to a gaseous point before it will burn, as all combustion depends upon that,—so flames mount high in air. Now in a candle-flame, as will be seen in the diagram (fig. 331.), there are three portions,—the inner dark core, which consists of unburnt gas; the outer flame, which gives light; and the outside rim of perfect combustion non-luminous. In the centre, A, there is no heat. If we place a piece of gauze wire over the flame at a little distance the flame will not penetrate it. It will remain underneath, because the wire, being of metal, quickly absorbs the heat, and consequently there is no flame. This idea led to the invention of the “safety” lamp by Sir Humphrey Davy, which, although it is not infallible, is the only lamp in general use in mines (figs. 329, 330).

Mines must have light, but there is a gas in mines, a “marsh” gas, which becomes very explosive when it mixes with oxygen. Of course the gas will be harmless till it meets oxygen, but, in its efforts to meet, it explodes the moment the union takes place; instead of burning slowly like a candle it goes off all at once. This gas, called “fire damp,” is carburetted hydrogen, and when it explodes it develops into carbonic acid gas, which suffocates the miners.