The chemistry of common things

Front matter

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Part I. The Atmosphere, And Its Relations To Plants And Animals

II. Constituents of the Atmosphere, ... ... ... ... 16

Ammonia and Nitric Acid, ... ... ... ... 40

Concluding Remarks on the Atmosphere, ... ... ... 45

III. The Plant, and what it Feeds on, ... ... ... ... 47

IV. The Plant, and what it Yields us—

Lignin, or Woody Fibre, ... ... ... ... CO

Concluding Remarks on the Starch Group, ... ... 01

V The Plant, and what it Y'ields us —

Glutin, or Vegetable Fibrin, ... ... ... 09

Legumin, or Vegetable Casein, ... ... ... 69

Concluding Remarks on the Albumen Group, ... ... 70 vm

CONTENTS.

,rI. The Animal, and what it Feeds on, ...

The Heat-producing Constituents of Food. ...

Circulation through the Animal System,

Aeration of the Blood — Respiration,

Effects of Exercise, Temperature, anil Clothing,

Excess of Food, and Formation of Fat,

Scarcity of Food and Starvation, ...

VII. The Animal, and what it Feeds on,

The Flesh-forming Constituents of Food,

Albumen, Fibrin, and Casein,

Wear and Tear of tlie Animal System,

Classification of Food— Proportion of the Constituents,

Hrass ar.d Flesh,

Milk,

Influence of Baking and Cooking,

Digestion of Food,

Part II. The Earth Or Soil In Its Relations To Plants And Animals

VIII. Importance ok Saline Food,

Disintegration of the Soil by Air and Water,

Formation of Rock and Soil,

Influence of Earthquakes and Volcanoes,

Concluding Remarks on the Formation of Rock, . .

IX. The Saline Food of Plants and Animals,

Common Salt, ...

Soda and Potash,

Bone and Bone Earth, ...

Lime and Chalk.

Iron,

Clay, Ac..

part m.

X. Tiie Decay of Plants and Animals. ...

Part IV

XI. The Circulation op Matter,

Conclusion, ...

Index

Pars

• i

THE

CHEMISTRY OE COMMON THINGS.

INTRODUCTION.

Chapter I. The Chemistry Of The World Around Us

1 . The events of every-day life may be little observed by us, but still they are wonderful. Strange things are taking place every day in town and country, which, from their daily and hourly occurrence, have become so familiar to us, that the greater number of old as well as of young people have ceased to wonder at them. When a child first learns to observe and remember anything correctly, it may give expression to much surprise when a tree puts forth its leaves, or a rose-bush unfolds its flowers; but the momentary thought about the birth of the leaves or the pretty little roses, in most instances, soon dies out for want of culture.

2. Were an inhabitant of some other world, differently constituted from our globe, to land on the Earth some bright summer morning, and inspect our homes, he would probably feel puzzled to understand how people inclosed in bodies of flesh and blood could be profited by partaking of oatmeal and milk or bread and tea. If the stranger sojourned here for a year or more, he would, amongst other things, hardly fail to observe that a tree, with its roots fixed in a sandy soil, and its leaves dangling in the thin air, could, as each summer’s sun beat upon it, shoot higher and higher, putting out more branches and leaves; and that a young animal, let loose for a number of months in a grass plot, could, by eating grass, add to its flesh, blood, and bones.

3. The occurrence of these, and other events of a like startling nature, would give our visitor from the Stars abundance of matter to think about, if he were inclined to be thoughtful at all. Did the tree flourish simply because it drew up into its interior a quantity of sand or clay, or the young animal grow heavier merely because it stored up in some internal cavities a quantity of grass, then no mystery would for a moment overhang either example. But the tree accumulates w’oody matter, and no true wood appears within its reach ; and the body of the animal is being constantly augmented by successive quantities of flesh, and blood, and bones, and neither of these are directly partaken of.

4. Though plants and animals appear different, they are made up of the same substances. The blade of grass, as it grows in our fields, looks vei-y unlike the ox which feeds upon it. In colour, shape, texture, and, indeed, in all that which marks the external aspect of the grass and the animal, the one stands in striking contrast to the other. But however unmistakable the difference may be in their general outward appearance, yet the moment the investigation is directed to their chemical constitution, it is observed that the ultimate substances, of which each plant and each animal are made up, are identical.

5. From the same quarry, stones may be taken which at one time go to build a palace, and at another time a cottage.

THE CHEMISTRY OF THE WORLD AROUND US.

So far as the general aspect of the dwellings is concerned, the one appears different from the other, but in the stones and the lime they are the same. And so in the plant and the animal kingdoms. The little particles of matter of which each plant and each animal are made up, have been obtained from the same great reservoirs of matter — the thin air or atmosphere, and the solid earth or soil; and though in look different, yet in the materials of which the many thousand plants and animals are built up, they are at one.

6. When a tree, or, what comes to the same thing, a piece of wood or coal, is burned, the greater part passes off as gas, and a very little of a grayish substance is left, which is generally called the ash. This is well seen in the burning of wood or coal in our fire-places. And, again, if a piece of an animal, such as a slice of meat, be thrown on a bright fire, it begins to char, and in greater part burns away, leaving a small quantity of ash behind. These experiments teach us, that when a plant or an animal is burned, it almost entirely becomes gas, which curls up the chimney and escapes into the air, whilst, at the same time, there is left behind a few ashes which cannot be burned.

7. All animals are dependent on plants for the food necessary to sustain their existence. It is true the lion feeds on other animals, and therefore he does not directly make use of plants as food; but the animals which he partakes of derive their sustenance from plants, and when he devours them, they hand that over to him. Herbivorous (grass-consuming) animals, therefore, obtain their nourishment from plants at first hand; and carnivorous (flesh-devouring) ones do so at second hand, or after it has passed through the system of the plant-eating animal.

8. Plants, on the other hand, derive their food from the air and the soil. The quantity of matter which they obtain from each of these sources is inversely that which would appear at first probable. The earth, in which the roots of a plant are fixed, is so solid, stable, and abundant, and the air in which the leaves flutter is so flighty and thin a medium, that nothing is more natural than to suppose that, besides affording the plant anchorage ground, the soil may supply the larger part of the matters necessary for building up the plant structure — but such is not the case.

9. The whole of that matter which passes off as gas when a plant is burned, has been obtained at one time or another from the atmosphere; whilst the very small portion left as ash is ail which has been derived from the soil. The atmosphere, therefore, is not only the region into which the noxious gases and the smoke from our fires pass, but it is likewise the great feeding-ground from which plants procure the greater portion of their food.

10. The atmosphere and the soil are, indeed, the great store-houses out of which matter is lent to the plant and the animal. Every one knows that a book consists of so many pages, each page of a number of words, and each word of one or more letters. At the first, the types which print these letters are lying in boxes, from which the compositor lifts them, and thereafter arranges them into words. Now, the plants and the animals on this world may be said to constitute the great book of living beings. Each individual is like a page, made up of a number of little pieces, which in their turn consist of still smaller parts or atoms. The atmosphere and the soil are the places where all these atoms are kept when they are not in use.

11. While a plant is growing, it draws in from the air and the ground a multitude of little atoms, which it builds up within its structure in many different forms. When the plant is ripe, and is partaken of as food by the animal, the

TIIE CHEMISTRY OF THE WORLD AROUND US.

latter takes possession of the atoms, and these become part of the animal frame. And just as the compositor, when the printing of the book is finished, takes all the type letters down again, and throws each one into the box it came from, so, when the plant and the animal die and rot, or are burned, all the atoms which compose them are separated; the part which came from the air returns to the same region, and that which was taken from the soil is bequeathed back again to it.

12. Agriculture, or the art of producing food, is the most primitive as well as the most necessary vocation. Whatevel appertains to the direct production of food for man must be considered the most essential of all practical information. At the same time, it must be remembered that what relates to food is not the only thing which man need think of, even when his thoughts are turned solely to earthly matters. The hard rock and the unwieldy clay have locked up within their stony grasp, treasures of gold, silver, copper, lead, iron, mercury, and many other things, which cannot be used as food; but which in the hands of man have been turned to good account, and have been made the means, at least, of procuring that most necessary of all things — namely, food. In this way the useful arts and manufactures become a necessity, opening, as they do, the door by which millions of men can pass through this life with ease and comfort to themselves and others.

13. The daily growth of a plant or an animal is, doubtless, a wonderful thing; but the hard rock and the thin air afford us, likewise, much cause for astonishment. The plant spins wood out of air and clay, and the animal manufactures flesh out of grass; but these events are not a whit more strange than that a candle or a coal-fire burns, a piece of iron rusts, an egg rots, or gunpowder explodes. Were we not aceus

THE CHEMISTRY OF THE WORLD AROUND US.

tomed to such changes, we would not only be surprised at their occurrence, but would, doubtless, feel alarmed at the appearance of many of them.

14. In the kindling of an ordinary fire, the paper burns, and disappears as gas ; the sticks then commence to sparkle, crackle, and vanish; and the black coals begin to send forth white flame, become red hot, and, ghost-like, glide slowly from our sight. These, and a thousand other changes in stone and gas, are going on around us every day, and yet we scarce give them a moment’s thought

15. The various simple substances or elements which constitute the atmosphere and the soil, and which at times appear in the plant and the animal, form the alphabet of chemistry. The number of elements contained in the A, B, C of chemistry, is sixty-five. About twenty of these elements are everywhere to be found, and enter into the composition of plants and animals, whilst the remaining forty-five elements occur only here and there in small quantity.

16. In the English alphabet there are twenty -four letters, by assorting which in different ways, many hundreds of words are made up. And so in regard to the chemical alphabet. The sixty-five elements in it can be united together in very many ways, and yield thousands of different substances — gases, liquids, and solids; — all of which are, doubtless, serviceable to man, directly or indirectly. Some are useful as food, and thereby give him strength and life; others can be cemented together into a house, and thereby afford him shelter; whilst others assist him much in his daily avocations.

1 7. When we wish to learn a language correctly, we must commence at its alphabet ; and learning letter by letter, afterwards proceed to form these letters into words, and words into sentences, and sentences into paragraphs. And

THE CHEMISTRY OF THE WORLD AROUND US.

so, in the study of chemistry, we must first learn something about the more simple substances or elements which compose the Earth’s erupt ; and thereafter we will be in a position to understand how these can be united together to produce complex substances, such as are found in minerals, and in plants and animals.

Chapter II. Constituents Of The Atmosphere

18. The atmosphere which surrounds the Earth is composed of millions of atoms of matter in a gaseous condition. These minute particles of air or gas are invisible to us, but nevertheless they fill up, not only the valleys, but ascend far above the highest mountains, and form a mantle or covering which entirely envelops the globe, and its plants and animals.

19. The lower stratum of the atmosphere which we reside in is pressed upon by the higher portions, and is comparatively heavy; but as we ascend into the upper regions of the air, either in a balloon or by climbing a mountain, part of the air is left below, and that which remains above, being subjected to less pressure, is more and more expanded, and becomes thin and rare.

20. The total thickness or height of the atmosphere is about 45 miles; but one-half of the whole is situated within 2f miles of the level of the sea ; three-fourths of the whole lie within 5J miles ; and the further we recede from the sea the air becomes the more attenuated, till at a distance of 30

CONSTITUENTS OF THE ATMOSPHERE.

miles it is so much expanded and rare, that less than 100th part of the entire atmosphere is left to occupy the remaining 15 miles of thickness.

21. The pressure jwhicli the air exerts on the globe and everything contained thereon is from 14 to 15 pounds on every square inch of surface ; which is equal in weight to a covering of water to the height of 32 feet, or a coating of quicksilver about 30 inches in depth. The atmospheric pressure is exerted equally on every side, and accordingly is not perceptible to touch ; but an ordinary-sized man, presenting about 2000 square inches of surface, must be subjected to a pressure of 30,000 pounds, or nearly 15 tons. This enormous weight is easily borne by us, owing to the uniformity of the pressure; whilst its withdrawal to a greater or less extent would lead to loss of blood, and to the disunion and destruction of the animal frame.

22. The temperature of the atmosphere is greatest at the surface of the earth, and becomes colder as we ascend, in the proportion of about 1° F. for every 352 feet in the lower regions, and less at greater heights. In all countries possessing a mountainous character, the freezing-point i9 reached at a greater or less distance from the sea-level. Thus, even at 0° latitude (the Equator), the level of everlasting snow is 15,207 feet; and this gradually descends, till at G0° latitude the snow-level is less than 4000 feet above the sea. The Andes, in South America, which rise to a height of 21,000 feet, are always covered with snow for a considerable distance from the top.

23. It is impossible to see the little particles of matter of which the atmosphere is composed; but it is highly probable that each minute atom of gas does not touch its neighbour atom, and that a certain space intervenes between each.

Thus the various gases may be represented by signs as in (161) ■>

CONSTITUENTS OE THE ATMOSPHERE.

Fig. 1, where the asterisks * stands for particles of oxygen gas, the minute diamonds <£> for atoms of nitrogen, the periods * for water vapour, and the pigmy pyramids -a. for atoms of carbonic acid, and where in either case the gaseous particles are represented as separated from each other by a greater or less space.

24. If we could, by the aid of a powerful microscope, be able to observe the particles of the various gases as they are mingled together in the air, they would probably present the appearance which the artist seeks to depict when he is painting a snow-storm, and where every little flake of snow appears here and there as a white dot on the canvas ; or that observed in Fig. 2, where the atoms of the various gases are represented by different signs. We may thus obtain some conception of the manner in which all the particles of the gases are present in the atmosphere, though they are so small that they cannot be made visible to the eye, and consequently cannot be seen.

25. The atmosphere has been shown by the chemist to be a mixture of many different gases and vapours, which are not in a state of union ; but the particles are merely mechanically mingled, as small pieces of coal and sand

• •••** *

*0 * 0* 0 * 0 * 0 ? 0

Fia. 2. (Dalton.)

would be were they shaken together. The more important constituents of the atmosphere are given in the following table : —

PRINCIPAL CONSTITUENTS OF THE ATMOSPHERE.

Oxygen,

Nitrogen,

Carbonic acid,

Water vapour,

Ammonia,

Nitric acid, and Ozone.

2G. The two gases, oxygen and nitrogen, constitute by far the greater bulk and weight of the air ; whilst the carbonic acid, ammonia, nitric acid, ozone, and water vapour, are present in much smaller quantity. Other substances, such as the fragrant perfumes from sweet-scented flowers, the badly-smelling gases evolved from putrifying matter, and miasma generated in damp places, are known to pass

CONSTITUENTS OF THE ATMOSPHERE.

into tlie air; but the proportion of these is so small, ami their durability probably so short, that they have only been discovered as constituents of the great atmosphere by the most delicate tests in the immediate neighbourhood of their production.

27. In all countries the atmosphere possesses the same composition. It has been examined in Paris and in London, and has been brought from high alpine hills, and been collected at a height of 21,000 feet in a balloon ; and leaving out of consideration the less abundant gases, the oxygen and nitrogen are present in the proportion of nearly one volume of oxygen to four volumes of nitrogen, forming five volumes of atmospheric air. The proportion of these gases in the air is in 100 parts : —

By volume —

21 of oxygen,

79 of nitrogen.

And by weight —

23 of oxygen,

77 of nitrogen.

OXYGEN.

28. This gas is one of the most important elements in the whole earth. It is not only present in the atmosphere to the extent of one-fifth of its entire bulk, but it forms eight out of every nine parts by weight of all water, is a constituent of the stones of which our house walls are built and streets paved, and of the clay of our fields and the sand of the sea-shore. Indeed, oxygen is so universally distributed in large quantity in every region of the world, that it is estimated that nearly one-lialf of the whole globe is composed of it, either in a gaseous, liquid, or solid condition.

CONSTITUENTS OF THE ATMOSPHERE.

29. The presence of oxygen in the atmosphere can be easily demonstrated in the ordinary phenomenon of the rusting of a piece of iron. When the iron is left exposed to the air, it soon gets coated over with a red powder; and if allowed to rust long enough, the hard tough iron disappears, and in its place there remains a quantity of red ochre or rust. During the process of rusting, the little atoms of iron seize the oxygen of the air as it floats over them, and combine therewith to form the red powder, which is thus composed of iron and oxygen.

30. The most convenient method for the preparation of oxygen is to heat a mixture of chlorate of potash and black oxide of manseveral glass jars. (Fig. 3.) Fiq. 3.

31. Four parts of chlorate of potash and one part of black oxide of manganese are mixed together and introduced into the flask ; and then heat is applied. The oxygen gas quickly comes away, and, escaping from the end of the bent tube, can be received in the jars filled with water, and standing on the shelf of the trough. The gas rises into the jars and displaces the water.

32. Oxygen is a transparent, colourless, odourless, and tasteless gas, and in these respects is not distinguishable from ordinary air. It is heavier than atmospheric air in

CONSTITUENTS OF THE ATMOSPn ERE.

the proportion of 1105 to 1000. It is not combustible, but is a great supporter of combustion. Thus a splinter of wood which has been ignited and blown out, so as to leave only a red tip, is immediately rekindled on being thrust into a jar of oxygen.

(Fig. 4.) A candle with merely a red wick, when plunged into a jar containing oxygen (Fig. 5), is relighted in the same manner, and thereafter

Fio. 4.

Fio. 5.

burns most vividly.

33. Again, a piece of sulphur placed in a small spoon, heated till it takes fire, and then introduced into a globe of oxygen (Fig. G), burns with a beautiful blue flame ; .and phosphorus, when set fire to under a bell jar containing the gas (Fig. 7), gives rise to the evolution of Fio. 6. light of the most Fro- 7.

dazzling nature.

34. Indeed, so great is the power of oxygen to support combustion, that a coil of fine iron wire, which has been tipped with burning sulphur and introduced into a jar con-

CONSTITUENTS OP THE ATMOSPHERE.

taining the gas (Fig. 8), immediately passes into vivid combustion, and the burning iron falls in white hot globules into a metal tray placed beneath. It is the presence of oxygen in the atmosphere, to the extent of one-fifth of its volume, which enables our candles, gas jets, and coals to burn ; and the other constituents of the air dilute the oxygen to that point at whicli the combustion can proceed at the ordinary rate.

35. As a supporter of respiration, or the breathing of animals, oxygen is likewise of vast importance; and were its presence withdrawn from the air for several moments, every animal would die. Indeed, oxygen is air-food to the animal, and is being constantly inhaled or breathed into the living system. Land animals obtain the supply of oxygen which they require through the operations of the lungs, which thus serve the office of carriers of air into the animal frame. Oxygen is soluble in water to the extent of 3£ volumes in 100 volumes of water; and it thus becomes of great importance to fish and other animals inhabiting fresh and salt water, which receive their air-food dissolved in the water which surrounds them, and which in many cases they pass through their gills.

Fig. 8.

NITROGEN.

36. Every five gallons of atmospheric air contain four gallons of nitrogen, which is thus the most abundant constituent of the gaseous envelope. It is generally prepared by removing the oxygen from a confined portion of air. This is most easily accomplished by burning a piece of phosphorus on a small stand under a glass bell jar containing ordinary air. The open end of the jar rests on a plate containing water. (Fig. 9.) The phosphorus in burning combines with the oxygen of the air, forming a white substance resembling snow, and called phosphoric acid, which quickly dissolves in the water, whilst the latter rises in the jar to supply the vacant place. When the phosphorus exhausts the oxj’gen, and thus extinguishes itself, the nitrogen gas remaining in the jar will become transparent in a short time, and will then occupy four-fifths of the original volume of the vessel.

37. Nitrogen is a colourless and transparent gas, with no taste and no odour. It is not combustible, neither is it h supporter of combustion, as may be observed by inverting the jar in which it was prepared, and plunging a lighted candle therein, when it will be immediately extinguished, owing to the want of oxygen. It is a general rule that a gas which will not allow a candle to burn in it will not admit of an animal to live in it, and nitrogen is no exception to this rule. It is a non-supporter of respiration, and animals introduced into pure nitrogen almost immediately die.

3S. The very large proportion of nitrogen in the atmosphere at once tells us that it cannot be directly a poisonous agent ; and the death of animals introduced into the pure gas is due rather to the absence of the oxygen or air-food. The principal offices fulfilled by nitrogen in the atmosphere appear to be the proper dilution of the oxygen to that point when it can support combustion and respiration, without active destruction of material, whilst at the same time it imparts that bulk to the entire atmosphere which is necessary for

CONSTITUENT^ OF THE ATMOSPHERE.

the production of strong currents of wind, which are alike useful in navigation and in carrying away smoky and poisonous gases.

CARBONIC ACID.

39. This gas is present in the free atmosphere in the small proportion of one part in every 2,500, or four volumes in 10,000 of air. It may be recognised as a constituent of the atmosphere by exposing some clear lime water in an open vessel, such as a tumbler or saucer. The lime water may be prepared by adding water to slaked lime (same as is used in making mortar); and after settling, a clear solution of lime is obtained. On exposing this liquid to the action of the air, the lime combines with the carbonic acid, forming carbonate of lime or chalk, which appears as a white film or skin on the surface of the water. This test is regarded as one of the best methods of showing the presence of carbonic acid in the atmosphere.

40. In the preparation of the gas in a state of purity for experimental purposes, recourse may be had to chalk, or, what is chemically the same thing, marble, which is found in masses like ordinary stone at and near the surface of the earth. When the marble is acted upon by an acid such as sulphuric acid or hydrochloric acid, much gas is evolved with effervescence, which consists of carbonic acid.

41. The apparatus required for the preparation of the gas is a double necked gas bottle (Fig. 10), fitted with a funnel tube for pouring in liquid, and a delivery tube for the escape of the carbonic acid gas. Chips of marble are placed in the bottle, the tubes are inserted, and thereafter some water and sufficient

2R CONSTITUENTS OP THE .ATMOSPHERE.

hydrochloric acid are added to cause the disengagement of the gas with effervescence. The delivery tube conducts the escaping gas to the lower part of the jar which is placed to receive it. As the gas continues to flow from the bottle, it chases out the air originally present in the jar, and in a short time the vessel becomes completely filled with carbonic acid.

42. The great weight of this gas, as compared with ordinary air, admits of a jar being filled with it by the above process of displacement, but it may also be prepared and received over water. The apparatus required for this mode of collecting the gas consists of a gas bottle, with a delivery tube leading the gas to a pneumatic trough, where it is passed into jars which have been previously filled with water. (Fig. 11.) On the large scale, carbonic acid is liberated in leaden vessels, from chalk or whiting and sulphuric acid, and is used for charging soda water, lemonade, and other aerated or effervescing waters.

43. Carbonic acid is a transparent, colourless gas, with an

CONSTITUENTS OF THE ATMOSPHERE.

agreeable, acidulous taste, as observed in the effervescing liquid known as soda water. When a bottle containing soda water is opened (Fig.

12), the gas which escapes in bubbles or bells is carbonic acid. It is soluble to the extent of its own volume in cold water, and hence there is some loss in preparing the gas at the pneumatic trough. A stream of the gas on being passed through water coloured with blue litmus or purple cabbage, exhibits faint acid properties.

44. When the gas from the generating bottle (Fig. 10) is allowed to flow through lime water contained in a wine glass or tumbler, it first causes the formation of a milky liquid due to the formation of carbonate of lime or chalk, and thereafter it dissolves the precipitate and yields a clear sparkling liquid, which agrees with many natural hard waters in containing chalk dissolved in excess of carbonic acid.

45. A lighted candle introduced into a vessel containing carbonic acid, is immediately extinguished, and the gas itself refuses to burn. In the same manner, a lighted taper, flaming sulphur, and burning phosphorus, are put out when introduced into the gas. Carbonic acid, therefore, is neither combustible nor is it a supporter of ordinary combustion. A piece of magnesium wire or ribbon, however, when lighted and plunged into a jar of carbonic acid, will burn as readily there as in ordinary air.