A Guide to the Scientific Knowledge of Things Familiar. Ebenezer Cobham Brewer
come from?
A. It was in the water and lime before; but was in a latent state.
Q. Was there heat in the cold water and lime, before they were mixed together?
A. Yes. All bodies contain heat; the coldest ice, as well as the hottest fire.
Q. Is there heat even in ice?
A. Yes. But it is latent, (i.e. not perceptible to our senses).[4]
[4] Latent, from the Latin word, Lateo, (to lie hid.)
Q. How do you know there is heat, if you cannot perceive it?
A. Thus:—Ice is 32° by the thermometer; but if ice be melted over a fire, (though 140° of heat are thus absorbed,) it will feel no hotter than it was before. (i.e. it will be only 32°, and not 172°)[5].
[5] 32°, i.e. 32 degrees; 140°, i.e. 140 degrees, &c.
Q. What becomes of the 140°, which went into the ice to melt it?
A. It is hidden in the water; or (to speak more scientifically) it is stored up in a latent state.
Q. How much heat may be thus secreted or made latent?
A. All things contain a vast quantity of latent heat; but, as much as 1140° of heat may remain latent in water.
Q. How can 1140° of heat be added to water, without being perceptible to our feelings?
A. 1st—140° of heat are hidden in the water, when ice is melted by the sun or fire.
2ndly—1000° more of heat are secreted, when water is converted into steam. Thus, before ice is converted into steam, 1140° of heat become latent.[6]
[6] Thus, one pint of boiling water, (212° according to the thermometer,) will make 1800 pints of steam; but the steam is no hotter to the touch than boiling water, both are 212°: therefore, when water is converted into steam, 1000° of heat become latent. Hence, before ice is converted to steam, it must contain 1140° of latent heat.
Q. Can we be made to feel the heat of ice or snow?
A. Yes. Into a pint of snow put half as much salt; then plunge your hand into the liquid; and it will feel so intensely cold, that the snow itself will seem quite warm in comparison to it.
Q. Is salt and snow really colder than snow?
A. Yes, many degrees; and by dipping your hand into the mixture first, and into snow afterwards, the mere snow will seem to be comparatively warm.
Q. What is fire?
A. Combustion is another instance of heat, arising from chemical action.
Q. What two things are essential to produce combustion?
A. Fuel and air.
Q. What are the elements of fuel?
A. As bread is a compound of flour, yeast, and salt; so fuel is a compound of hydrogen and carbon.
Q. What are the elements of atmospheric air?
A. The air is a compound of oxygen and nitrogen mixed together; in the proportion of five gallons of nitrogen, to one of oxygen.
Q. What is carbon?
A. The solid part of fuel. It abounds also in all animal bodies, earths, and minerals.
Q. Mention some different species of carbon.
A. Common charcoal, lamp-black, coke, black lead, and the diamond, are all varieties of carbon.
Q. What is hydrogen?
A. An inflammable gas. The gas used in our streets, is only the hydrogen gas driven out of coals by heat.
Q. What are the peculiar characteristics of hydrogen gas?
A. Though this gas itself will burn, yet a candle will not burn when immersed in it; nor can an animal live in it. Hydrogen gas is the lightest of all known substances.[7]
[7] Hydrogen gas may be made thus:—Put some pieces of zinc or iron filings into a glass: pour over them a little sulphuric acid (vitriol), diluted with twice the quantity of water; then cover the glass over for a few minutes, and hydrogen gas will be given off.
Exp. If a flame be put into the glass, an explosion will be made.
If the experiment be tried in a phial, which has a piece of tobacco-pipe run through the cork; and a light held a few moments to the top of the pipe, a flame will be made.
If a balloon be held over the phial, (so that the gas can inflate it,) the balloon will ascend in a very few minutes.
Q. What is oxygen?
A. A gas, much heavier than hydrogen; which gives brilliancy to flame, and is essential to animal life.[8]
[8] Oxygen gas is much more troublesome to make than hydrogen. The cheapest plan is to put a few ounces of manganese (called the black oxide of manganese) into an iron bottle, furnished with a bent tube; set the bottle on a fire till it becomes red hot, and put the end of the tube into a pan of water. In a few minutes, bubbles will rise through the water; these bubbles are oxygen gas.
These bubbles may be collected thus:—Fill a common bottle with water; hold it topsy-turvy over the bubbles which rise through the pan, but be sure the mouth of the bottle be held in the water. As the bubbles rise into the bottle, the water will run out; and when all the water has run out, the bottle is full of gas. Cork the bottle while the mouth remains under water; set the bottle on its base; cover the cork with lard or wax, and the gas will keep till it be wanted.
N. B. The quickest way of making oxygen gas, is to rub together in a mortar half an ounce of oxide of copper, and half an ounce of chlorate of potassa. Put the mixture into a common oil flask, furnished with a cork which has a bent tube thrust through it. Heat the bottom of the flask over a candle or lamp; and when the mixture is red hot, oxygen gas will be given off. Note—the tube must be immersed in a pan of water, and the gas collected as before.
(Chlorate of potassa may be bought at any chemist’s; and oxide of copper may be procured by heating a sheet of copper red hot, and when cool, striking it with a hammer: the scales that peel off, are oxide of copper.)
Exp. Put a piece of red hot charcoal, (fixed to a bit of wire,) into your bottle of oxygen gas; and it will throw out most dazzling sparks of light.
Blow a candle out; and while the wick is still red, hold the candle (by a piece of wire,) in the bottle of oxygen gas; the wick will instantly ignite, and burn brilliantly.
(Burning sulphur emits a blue flame, when immersed in oxygen gas.)
Q. What is nitrogen?
A. Nitrogen is another invisible gas. It will not burn, like hydrogen; and an animal cannot live in it: it abounds in animal and vegetable substances, and