To the chemist, all forms of matter are mere combinations of elements. Chemical analysis is a process of separating, dividing, and subdividing matter. When the chemist separates or analyzes compounds, until he can no longer simplify or subdivide them, he calls these simple products "chemical elements."

Many of the chemical elements are well known, such as copper, iron, and gold. Other elements that are still more common are unknown in their elementary form, because they combine with other elements so readily that they exist in nature only as compounds. For example: Hydrogen, united with oxygen, forms water; the elements chlorin and sodium, combined or united, form common salt.

Common elements.

Altogether chemists have discovered about eighty-four elements, many of which are rare, and do not occur in common substances.

All substances of the earth, whether dead or living, are formed of chemical elements. These elements may be found in the pure or elementary state, or they may be mixed with other substances, or they may be combined chemically. Copper, iron, and gold are elements in the pure state. If we should take iron and copper filings and mix them together, we would still have copper and iron. Were we to take copper and gold and melt them together, we would have a metal that would be neither copper nor gold.

Number of elements.

It would be harder than one and softer than the other. But this substance would still be a mixture, and its properties half way between copper and gold.

If a piece of iron be exposed to dampness it will soon become covered with a reddish powder called "rust." The rusting of iron is a process of chemical changes in which the original substance was wholly changed by chemically uniting with the oxygen and the moisture of the atmosphere, which is really a process of combustion. The burning of wood, the rusting of iron, the souring of milk, and the digestion of food are all mere examples of chemical changes.

Care should be exercised to distinguish chemical compounds from simple mixtures. Air is not a compound, but chiefly a mixture of oxygen and nitrogen gases. Water, however, is a compound of oxygen and hydrogen. Both salt and sugar are compounds, but it we grind them together, we do not have a new compound, but a mixture of two compounds. Most of the common things around us are mixtures of different compounds or substances. Rocks are mixtures of many different compounds. Wood is, likewise, formed of many different substances. Wheat contains water, starch, cellulose, and many other compounds. Grinding the wheat into flour does not change it chemically, but if we heat the flour in an oven, some of the starch is changed into dextrin. The starch has disappeared, and dextrin, a new substance, appears in its place. Whenever elements are combined into compounds, or compounds broken up into elements, or changed into other compounds, we have true chemical action. The names of the elements are formed in many different ways. The name chlorin is derived from a Greek word meaning greenish-yellow, as this is the color of chlorin. Bromin comes from a Greek word meaning a stench, a prominent characteristic of bromin being its bad odor. Hydrogen is formed from two Greek words, one of which means water and the other to produce, signifying that it enters into the composition of water. Potassium is an element found in potash, and sodium in soda, etc.

Examples of chemical changes.

Difference between chemical compounds and simple mixtures.

For convenience, abbreviations are used for the names of elements and compounds. Thus, instead of oxygen, we may write simply "O"; for hydrogen, "H"; for nitrogen, "N," etc. Very frequently the first letter of the name of the element is used as the symbol. If the names of two or more elements begin with the same letter, some other letter of the name is added. In some cases the symbols are derived from the Latin names of the elements. Thus, the symbol of iron is Fe, from ferrum; of copper, Cu, from cuprum.

Names of elements - how derived.

Symbols of elements - how derived.

The following table gives the names of the elements which it will be necessary to understand in pursuing this work.

Aluminum . .Al

Arsenic.....As

Boron......B

Bromin.....Br

Calcium ... .Ca

Carbon.....C

Chlorin.....Cl

Chromium .. Cr

Copper.....Cu

Fluorin.....F

Gold........Au

Hydrogen .. .H

Iodin .......I

Iron ........Fe

Lead........Pb

Magnesium .. Mg

Mercury.....Hg

Nickel.......Ni

Nitrogen .... N Oxygen......O

Phosphorus . P Platinum . . . . Pt Potassium . . .K

Silicon ......Si

Silver........Ag

Sodium......Na

Sulfur.......S

Tin..........Sn

Zinc ........Zn