The Chemist as an Inventor The expert in chemistry often invents new sub stances which prove of measureless value. Fiber silk, celluloid, Bakelite, " papier mAch4," waterproof garments, artificial rubies, gas mantles, all sorts of building compositions, and metal alloys, numberless dyes and stains, photographic films and plates, sub stitutes for rubber, leather, and cloth, special kinds of glass for fine lenses—these are just a few of the products of his work.
Public health departments have their laboratories for identifying and combating disease, for testing food, milk, drugs, etc. In the pursuit of criminals, the law calls upon the chemist to detect poisons and blood stains, or find evidence of forgeries in the ink of signatures. And the high explosives, poison gases, liquid fire, and other weapons of destruction used in the World War of 1914-18 show what powerful per sons are the chemists when nation attacks nation and the bitter rivalry of battle is born.
Chemistry is usually divided into two branches, in organic and organic. The organic branch deals chiefly with those countless compounds of carbon which are usually produced only by the life processes of " organic" or living things—plants and animals.
Albumen, for instance, of which the white of an egg is principally made up, is one of the commonest of organic chemical compounds the fats and oils, the sugars, the cellulose of which wood and cloth are composed, are other such compounds. It is in this branch that the industrial chemist does most of his work, investigating these intricate substances, devis ing substitutes for them, or finding artificial ways of doing nature's work. Many organic compounds, formerly believed to be obtainable only from natural sources, are now " created" by synthetic chemistry.
Inorganic chemistry deals with the elements them selves and those simpler compounds which exist or are produced in nature without the intervention of living organisms, or which can readily be made from the elements in the laboratory. Such compounds are salt, water, glass, etc.
The Smallest Things in the World Suppose we consider the smallest particle of com mon salt which can exist and still have the properties of salt. It is called a molecule of salt. The still smaller bits of sodium and chlorine which compose this molecule are called atoms. Thus, one atom of
sodium united to one atom of chlorine by that mysterious chemical attraction we discussed earlier produces one molecule of salt.
Until the invention of the ultra-microscope (see Microscope), no one had ever seen anything so small as a molecule, much less an atom. But works and the marvelous changes it brings about, two familiar instances present themselves. There is a very dangerous metal known as sodium which ignites spontaneously in the atmosphere, and for safety has to be kept in naphtha. If we want a piece of it we dare not bring it into the air, but must cut it while it is still in the naphtha. It must on no account be touched with the bare fingers or a painful burn will result. • Then there is a highly dangerous gas called chlorine.
It is very suffocating and was used in the World War to kill whole regiments of soldiers. If only a small proportion is in the air of a room, caged birds and mice will die.
We heat a small piece of sodium, this dangerous metal, and introduce it into a jar of chlorine, this still more dangerous gas, and the sodium bursts into flame and burns with a fine golden-yellow flame.
The chemical attraction of the sodium for the chlorine is in operation. The dangerous metal and the dangerous gas both completely disappear, and in their place comes an entirely different substance with none of the properties of sodium or chlorine, a substance that is not only harmless, but is positively essential to the healthy life of man—common salt.
The force of chemical attraction makes life-preserving salt from the dangerous metal sodium and the suffocating gas chlorine.
Here is the other familiar example. There is a gas which we call hydrogen, the lightest of all known substances. It burns with a pale blue flame that is very hot. Then there is another gas, oxygen, present in the atmosphere, which will not itself burn, but which makes it possible for other substances to burn.
We burn a jar of hydrogen in a jar of air which con tains much oxygen. Soon the hydrogen gas ceases to exist, the oxygen in the air of the jar also disap pears, and in their places we find little drops of moisture, which prove to be ordinary pure water.