ELEMENTS AND COMPOUNDS.
By an element is meant a substance which has never been resolved into parts, and conversely, one that can not be produced by the union of two or more substances. There is some difference of opinion as to their number. It is usually given as sixty-four. There are a great many compounds. Nature seems to delight in surprising us by the simplicity of the means employed in producing marvelous results. As the mind of Milton combined the twenty-six letters of our alphabet to form “Paradise Lost,” so the Infinite arranged and re-arranged the elements to form the sublime poem of creation. Fifty-one of the elements are metals, and thirteen metalloids; gold is a familiar example of the former, and sulphur of the latter. A few, like hydrogen and oxygen, are gases; two are liquids; quicksilver and bromine: the greater number exist as solids. But few of them are found native, i. e., chemically uncombined with other substances. In the fierce heat of former ages they were mixed as in a mighty crucible, and few escaped the power of affinities thus engendered. Gold and copper are sometimes found pure, but even they, more frequently than otherwise, exist fused with other substances.
Compounds are of three classes—acids, bases and salts. Sand is a specimen of the first, lime of the second, and clay of the third. Fixedness is a characteristic of mineral compounds, yet they are by no means incapable of change; certain influences come in to promote it, of which the following are the most important—heat, solution, friction and percussion.
Two gases, oxygen and hydrogen, may remain side by side for years uncombined, but a single spark will cause them to rush together with terrific energy.
If the contents of the blue and white papers in a Seidlitz powder are mixed, no chemical action follows, but if dissolved separately in glasses of water, and then poured together, a violent effervescence takes place. If a small amount of potassium chlorate and a little piece of sulphur be put together in a mortar, and then pressed by the pestle, sharp detonations follow. Dynamite, which is nitro-glycerine mixed with infusorial earth, sugar or sawdust, is quite harmless when free from acid, unless struck. The above instances illustrate the various influences that stimulate chemical combination. Almost all the crust of the earth is formed of three substances—quartz, lime, and alumina. Wherever we stand on the round globe, it is safe to say that one or all of these are beneath our feet.