Formalin

for'ma-lin, a liquid much used of late as a preservative and disinfectant. It is formed by dissolving forty per cent of formaldehyde in sixty per cent of water. The former is a compound of carbon, hydrogen, and oxygen. As indicated by the name, the active principle is much the same as that contained in the black juice or formic acid ejected by an ant. In a highly diluted form formalin is much used in museums as a preservative in which to bottle animal and vegetable specimens. A tablespoonful of concentrated formalin is sufficient for a quart jar of water. It has several advantages over alcohol. It costs less. Substances immersed in it are more apt to preserve their natural color. In a concentrated form it is less bulky and is better suited for carriage on scientific expeditions. As it kills most if not all bacteria, it is an excellent disinfectant. Physicians inject formalin into the veins of the arm as a remedy for certain forms of bacterial disease. The presence of formalin may be detected in the following manner: Place four tablespoonfuls of the sample in a teacup with an equal quantity of strong muriatic acid and a piece of iron alum about as large as a pin head. After mixing by means of a gentle rotary motion, place the cup in a pan of boiling water and let it stand for about two minutes. If formaldehyde is present the mixture will acquire a purple color.