Q. Why do trees and flowers help to make country air wholesome?
A. Because trees and flowers absorb the carbonic acid generated by the lungs of animals, putrid substances, and other noxious exhalations.
Q. Why is the air of cities less wholesome than country air?
A. 1st—Because there are more inhabitants to vitiate the air:
2ndly—The sewers, drains, bins, and filth of a city, very greatly vitiate the air:
3rdly—The streets and alleys prevent a free circulation: and
4thly—Besides all this, there are fewer trees to absorb the excess of carbonic acid gas, and restore the equilibrium.
Q. Why are persons who live in close rooms and crowded cities, generally sickly?
Q. Where does the carbonic acid of close rooms and cities come from?
A. From the lungs of the inhabitants, the sewers, drains, and so on: besides, trees and gardens are not numerous enough to absorb the noxious gas as fast as it is generated.
Q. What becomes of the carbonic acid of crowded cities?
A. Some of it is absorbed by vegetables, and the rest is blown away by the wind, and diffused through the whole volume of the air.
Q. Does not this constant diffusion of carbonic acid affect the purity of the whole air?
A. No; because after it is thus diffused, it is carried to various lands, and absorbed in its passage by the vegetable world.
Q. Why do persons who ascend in balloons feel intense pain in their eyes and ears?
Q. Why is it often painful, and difficult to breathe, on a mountain top?
A. Because the pressure of air on the mountain top is not so great as on the plain; and the air inside our bodies (seeking to become of the same rarity) bursts through the pores of the body, and produces great pain.
Q. Why do we feel oppressed just previous to a storm?
A. Because the air is greatly rarefied by heat and vapour; and the air inside us (seeking to become of the same rarity) produces an oppressive and suffocating feeling.
Q. Why do divers suffer great pain in their eyes and ears under water?
A. Because the air at the bottom of the sea is more dense than the air on the surface; and while the air inside the diver’s body is settling into the same density, he feels oppressed with pain, especially in the ears.
Q. Why is this pain felt especially about the ears of a diver?
Q. Why do our corns ache just previous to rain?
A. Previous to rain, the density of air is greatly lowered (as every one knows from the fall of the barometer); in consequence of an unequal pressure, our feet swell; but the hard corn, not being elastic, is painfully stretched and pressed.
(Some of this pain is due to electricity.)
Q. Why do cellars feel warm in winter?
A. As the external air has not free access into cellars, they remain at a pretty even temperature, which (in winter time) is about 10 degrees warmer than the external air.
Q. Why do cellars feel cold in summer time?
Q. Why does lightning strike the oak-tree more frequently than any other tree?
A. 1st—Because the grain of the oak, being closer than that of any other tree, renders it a better conductor: and
2ndly—The sap of the oak contains a large quantity of iron in solution, which is a most admirable conductor of lightning.
Q. Why does air rust iron?
A. The oxygen of the air combines with the surface of the iron, and produces oxide of iron, which is generally called rust.
This rust is a species of combustion.
Q. Why does hot iron scale and peel off, when struck with a hammer?
A. The oxygen of the air very readily unites with the surface of the hot iron, and forms a metallic oxide (or rust) which scales off when struck with a hammer.
Q. Does iron rust in dry air?
A. No; iron undergoes no change in dry air.
A. Because the air is damp; and moist air oxidizes (or rusts) iron and steel.
Q. In what part of the year is it most difficult to keep stoves and fire-irons bright?
A. In autumn and winter; because the capacity of the air for holding water being on the decrease, its vapour is deposited on every-thing with which it comes in contact.
Q. Why does greasing iron prevent its becoming rusty?
A. Because grease prevents the humidity of air from coming in contact with the surface of the iron.
Q. Why do not stoves rust so frequently as pokers and tongs?
A. Because stoves are generally covered with plumbago, or black lead.
Q. What is plumbago, or black lead?
A. A mixture of charcoal and iron filings.
A most excellent varnish to prevent rust is made of 1 pint of fat oil varnish, mixed with 5 pints of highly rectified spirits of turpentine, rubbed on the iron or steel with a piece of sponge. This varnish may be applied to bright stoves and even mathematical instruments, without injuring their delicate polish.
Q. Why does ornamental steel (of a purple or lilac colour) rust more readily than polished white steel?
A. Because the lilac tinge is produced by partial oxidation; and the process which forms rust has, therefore, already commenced.
Q. How can lilac steel be kept free from rust?
A. By keeping it in a very dry place; for then no additional oxygen will come in contact with it, to increase its amount of rust.
Q. Do any other metals (besides iron) combine rapidly with oxygen?
A. Yes; copper, lead, mercury, and even silver to some extent.
Q. Why does copper tarnish?
A. The tarnish of copper is caused by its oxidation; that is, the oxygen of the air combines with the surface of the copper, and instead of rusting it, covers it with a dark tarnish.
Q. Why does lead lose its brightness, and become dull and of a darker hue, by being exposed to the air?
Q. Why is it difficult to keep silver bright?
A. Because the vapour of the air oxidizes its surface, and tarnishes it.
Q. Why do silver tea-pots and spoons tarnish more quickly than silver ore or bullion?
A. Because alloy (of some baser metal) is used to make it more hard and lasting; and this alloy oxidizes more quickly than silver itself.
Q. Why does German silver turn a dingy yellow in a few hours?
A. German silver has a great affinity for oxygen, and shows its oxidation by a sickly yellow tarnish, instead of rust.
Q. If quicksilver (or mercury) is tarnished like copper and lead,—Why does it preserve its brilliancy in barometers and thermometers?
A. Because air is excluded from it, and no moisture comes in contact with it to oxidize (or tarnish it).
Q. Is gold affected by the atmosphere?
Q. Which of the metals is capable of resisting oxidation altogether?
A. Plat’inum; in consequence of which, the graduated arcs of delicate instruments for observation are made of plat’inum instead of any other metal.
Q. Why is plat’inum used for the graduated arcs of delicate mathematical instruments, instead of any other metal?
A. Because it will never oxidize; but retain its bright surface in all weathers free from both rust and tarnish.
Q. Before plat’inum was discovered, which of the metals was employed for the same purpose?
A. Gold.
Platinum, (a white metal), so called from “plata,” the Spanish word for silver. It was first introduced into England by Mr. Wood, (A. D. 1749) from South America.
Q. For what other scientific purposes is plat’inum now used?
A. For crucibles in which acids are employed, and for galvanic batteries.
Q. Why are crucibles (in which acids are employed) made of plat’inum?
Q. Which of the metals have the greatest affinity to oxygen?
A. Those called potassium and sodium.
Potassium and sodium derive their names from potash and soda. Potassa is the oxide of potassium; and soda is the oxide of sodium.
Q. How is the affinity of potassium and sodium for oxygen shewn?
A. They decompose water the moment they are brought into contact with it.
Q. What effect has potassium on water?
A. It catches fire the moment it is thrown into water, and burns with a vivid flame, which is still further increased by the combustion of hydrogen separated from the water.
(N.B. Water is composed of oxygen and hydrogen; and potassium separates the two gases.)
Q. What effect has sodium on water?
A. It does not take fire as potassium does, but undergoes very rapid oxidation.
Q. Is the furr of kettles an oxide?
Q. Is not this furr of boiling water often dangerous?
A. Yes; especially in tubular boilers, such as those employed in railways.
Q. Why is this furr especially troublesome in railway engines?
A. Because it is a bad conductor of heat; in consequence of which, it hinders the evaporating effect of the fire, and prevents the economy of fuel.
Q. Why is this furr especially dangerous in railway engines?
A. Because when it is deposited in the boilers, they are likely to become over-heated; and then explosion will take place from the sudden generation of highly elastic steam.
Q. Why cannot railway engines be fed with brackish water?
A. Because brackish water contains mineral salt, which makes a much larger deposit of furr, than that which contains only vegetable matter.
Q. What is choke damp?
A. Carbonic acid gas accumulated at the bottom of wells and pits, which renders them noxious, and often fatal.
Q. Why is not this carbonic acid taken up by the air, and diffused, as it is in cities?
A. Because (being heavier than common air) it cannot rise from the well or pit; and no wind can get to it to blow it away.
Q. Is carbonic acid wholesome?
A. No; it is fatal to animal life, when inhaled through the mouth; acting on the stomach, as a narcotic poison (i. e.. a poison which produces death from drowsiness).
Q. How can any one know, if a place be infested with carbonic acid gas?
Q. Why does a miner lower a candle into a mine, before he descends?
A. Because the candle will be extinguished, if the mine contains carbonic acid gas: but if the candle is not extinguished, the mine is safe, and the man may fearlessly descend.
Q. Why are persons sometimes killed, by leaning over beer vats?
A. Vats (where beer has been made) contain a large quantity of carbonic acid gas, produced by the “vinous fermentation” of the beer; and when a man incautiously leans over a beer vat, and inhales the carbonic acid, he is immediately killed thereby.
Q. Why are persons often killed, who enter beer vats to clean them?
Q. Why are the jungles of Jarva and Hindostan so fatal to life?
A. Because vast quantities of carbonic acid are thrown off by decaying vegetables; and (as the wind cannot penetrate the thick brushwood to blow it away) it settles there, and destroys animal life.
Q. Why are persons sometimes killed by having a charcoal fire in their bed-rooms?
A. When charcoal is burned, the carbon of the charcoal unites with the oxygen of the air, and forms carbonic acid gas, which is a narcotic poison.
Q. Why does the carbonic acid gas of a charcoal fire rise and disperse itself about the room; whereas the carbonic acid gas of a beer vat settles near the floor?
A. The carbonic acid gas of a charcoal fire is heated by the combustion of the fuel, and rises; but the carbonic acid gas of a beer vat is not heated, and, therefore, rests on the bottom of the vat.
Q. Why do persons throw lime into bins to prevent their offensive smell, in summer time?
Q. Why do persons throw lime into sewers in summer time?
A. Sewers (like bins) contain large quantities of carbonic acid, which readily combines with lime, and produces carbonate of lime; and thus the offensive gas of the sewer is neutralized.
Q. Can carbonic acid be removed in any way besides by lime?
A. Yes; water thrown into a pit will disperse the carbonic acid.
Q. What effect has water on carbonic acid gas?
A. Water (under pressure) absorbs carbonic acid gas; and parts with it (when the pressure is removed) in the form of effervescence.
Q. Why does aerated water effervesce, when the cork is removed?
Q. Why does soda water effervesce?
A. Soda water contains 8 times its own bulk of carbonic acid gas, which makes its escape in effervescence, the moment that the cork is removed.
Q. Why does ginger pop fly about in froth, when the string of the cork is cut?
A. All vinous fermentation produces carbonic acid gas. While the cork is fast, the water of the liquor absorbs the carbonic acid; but the moment that the pressure is removed, the gas is given off in effervescence.
Q. Why does bottled ale froth, more than draught ale?
A. Because the pressure is greater in a bottle than in a tub which is perpetually tapped: and effervescence is always produced in proportion to the pressure.
Q. Why does bottled ale and porter become “lively” and frothy by being set before the fire?
Q. What produces the froth of bottled porter?
A. The carbonic acid gas, produced by its vinous fermentation; which is absorbed by the liquor so long as the bottle is well corked, but is given off in froth as soon as the pressure of the cork is removed.
Q. What gives the pleasant acid taste to soda water, ginger beer, champagne, and cider?
A. The presence of carbonic acid, generated by fermentation, and liberated by effervescence when the pressure of the cork is removed.
Q. Why does fresh spring water sparkle, when poured from one vessel to another?
A. Because fresh spring and pump water contain carbonic acid; and it is the presence of this gas which makes the water sparkle.
Q. How is carbonic acid gas produced by fermentation?
A. Malt and fruit both contain sugar; and sugar consists of carbon, oxygen, and hydrogen. In fermentation, a part of the carbon and oxygen of the sugar escape, in the form of carbonic acid gas.
Carbonic acid gas is a compound of carbon and oxygen, in the following proportions:—3 lbs. of carbon and 8 lbs. of oxygen will form 11 lbs. of carbonic acid gas. Now, 100 lbs. of white sugar contains 43 lbs. of carbon; 50 lbs. of oxygen; and 7 lbs. of hydrogen.
Q. How is al’cohol produced by fermentation?
A. The hydrogen of the sugar combines with the residue of the oxygen and carbon to form “al’cohol.”
Q. What is al’cohol?
A. Al’cohol is the spirit of wine or beer, obtained by fermentation.
(100 gallons of alcohol consist of 38 gallons of oxygen; 43-1/2 of carbon; 15 of hydrogen; and 3-1/2 of nitrogen.)
Q. Why is barley malted?
Q. How is barley malted?
A. The barley is moistened with water, and heaped up; by which means, great heat is produced, which makes the barley sprout.
Q. Why is not the barley suffered to grow, as well as sprout?
A. Plants in the germ contain more sugar than in any other state; as soon as the germ puts forth shoots, the sugar of the plant is consumed, to support the shoot.
Q. How is barley prevented from shooting, in the process of malting?
A. The barley is put into a kiln as soon as it sprouts; and the heat of the kiln checks or destroys the young shoot.
Q. Why is yeast put into beer to make it work?
A. Yeast supplies the beer with nitrogen, which is one of the ingredients of alcohol.
Alcohol consists of oxygen, carbon, and hydrogen, (obtained from the sugar of malt), and nitrogen, (obtained from yeast).
A. Because fruit contains carbon, hydrogen, oxygen, and nitrogen, in the form of “gluten;” and, therefore, ferments spontaneously.
(Gluten is explained fully in the Appendix.—Turn to the word in the Index.)
Q. Does not malt contain carbon, hydrogen, oxygen, and nitrogen, as well as fruit?
A. No; the sugar of malt contains carbon, hydrogen, and oxygen, but no nitrogen; in consequence of which, yeast (which contains nitrogen) is added to the wort.
Q. Why do not grapes ferment while they hang on the vine?
A. 1st—Because the skin lets out the water of the pulp, which causes the grapes to shrivel and dry up: and
2ndly—The skin prevents the admission of oxygen into the pulp, from the air without.
Q. What is the froth or scum of fermented liquors?
Q. Why does a small piece of raw meat, or a few raisins improve flat beer?
A. 1st—Because they supply it with nitrogen to form it into al’cohol.
2ndly—As the raw meat, &c. putrifies, it gives off carbonic acid gas into the beer, which gives it “life.”
Q. Why is beer flat, if the cask be open too long?
A. Because too much of the carbonic acid gas (produced by fermentation) is suffered to escape.
Q. How is the carbonic acid gas of beer generated?
A. The saccharine (or sugar) of the malt is converted by fermentation into carbonic acid gas and alcohol.
Q. Why does beer turn flat, if the vent peg be left out of the tub?
A. Because the carbonic acid gas escapes through the vent hole.
Q. Why will not beer run out of the tub, till the vent peg is taken out?
A. When the tap is turned, air rushes through the tap into the bottom of the tub, and holds the liquor in.
The upward pressure of air is illustrated by the
following simple experiment:—Fill a wine-glass with water; cover the top of the glass with a piece of writing paper; turn the glass topsy turvy, and the water will not run out. The paper is used merely to give the air a medium sufficiently dense to act against.
Q. Why does the beer run freely, immediately the vent peg is taken out?
A. As soon as the vent peg is taken out, air rushes through the vent hole at the top of the tub,—presses the liquor down, and forces it through the tap.
Q. Why does liquor flow reluctantly out of a bottle held upside down?
A. Because the upward pressure of the air prevents the liquor from flowing out.
Q. Why should a bottle be held obliquely, in order to be emptied of its liquor?
A. Because air will then flow into the bottle, and help the liquor out by balancing the upward pressure.
Q. Why does wine (poured from a bottle quickly) spirt about without going into the decanter?
Q. Why is beer made stale, by being exposed to the air?
A. Because air absorbs its carbonic acid, which gave it “life.”
Q. Why is porter made stale, by being exposed to the air?
A. Because air absorbs its carbonic acid, which gave it “life.”
Q. Why does the effervescence of soda water and ginger beer so soon go off?
A. Because air absorbs the carbonic acid, which produced the effervescence.
Q. Why is boiled water flat and insipid?
A. Because the whole of the carbonic acid is expelled by boiling, and absorbed by the air.
Q. Why does water become flat and insipid, after it has been drawn some time?
A. Because air absorbs its carbonic acid; and when its carbonic acid is absorbed, the water is flat and insipid.
Q. Why should spring water (used for washing) be exposed to the air?
Q. Why does yeast make bread light?
A. Flour contains a small portion of saccharine matter (or sugar); and the yeast (mixing with this) produces fermentation, as it does in brewing.
Q. How does fermentation make the dough rise?
A. During fermentation, carbonic acid gas is evolved; but the sticky texture of the dough will not allow it to escape, so it forces up little bladders all over the dough.
Q. Why is dough placed before the fire?
A. 1st—Because the heat of the fire increases the fermentation: and
2ndly—It expands the gas which is confined in the little bladders; in consequence of which, the bladders are blown up larger, and the dough becomes lighter and more porous.
Q. Why is bread heavy, if the dough be removed from the fire?
Q. Whence does the heat of fire arise?
A. The carbon of fuel (when heated) combines with the oxygen of the air, and produces carbonic acid gas: again, the hydrogen of the fuel combining with other portions of oxygen, condenses into water; by which chemical actions heat is evolved.
Q. Whence does the heat of our own body arise?
A. The carbon of the blood combines with the oxygen of the air inhaled, and produces carbonic acid gas; which produces heat in a way similar to burning fuel.
Q. Whence does the heat of a dunghill arise?
A. The straw, &c. of the dunghill undergoes fermentation as it decays: the fermentation produces carbonic acid gas, and heat is evolved by a species of combustion (as in the two former cases).
Q. What changes do vegetables undergo from putrefaction?
Q. What changes do animal bodies undergo from putrefaction?
A. The same as vegetables, with this addition—they give out ammonia, sulphur, and phosphorus also; which causes the offensive smell of putrefying animal bodies.
Q. Why is lime heated by a kiln?
A. All marl and chalk abound in carbonic acid; and (when heated by a fire) the carbonic acid flies off in gas, producing great heat.
Q. What is mortar?
A. Lime mixed with sand and water.
Q. What is lime?
A. Lime-stone burnt produces lime.