807. Why do the bubbles arise from two or three points in columns, rapidly succeeding each other?
Because, when the formation of gas once begins, and bubbles ascend, there is less pressure in the line of the column of bubbles; the carbonic acid, therefore, draws towards those points as the easiest channel of escape.
These explanations equally apply to the "working" of beer, by which yeast is produced; to the effervescence of various waters, acidulated drinks, ginger beer, &c., and also to the "sponging" of bread, &c.
808. Why does gunpowder explode?
Gunpowder is made of a very intimate mechanical mixture of nitrate of potash, charcoal, and sulphur. When these substances are heated to a certain degree, the nitrate of potash is decomposed, and its oxygen combines with the charcoal and sulphur, instantaneously forming large volumes of carbonic acid gas and nitrogen, which, seeking an escape, produce an explosion.
"Thus saith the Lord, Let not the wise man glory in his wisdom, neither let the mighty man glory in his might, let not the rich man glory in his riches."—Jeremiah ix.
809. Why does charcoal act as a powerful disinfectant?
Because the carbon readily absorbs, and combines with various gases, neutralising their offensive odours, and destroying their unhealthy properties.