This substance was originally discovered in the red ant (Formica rufa), but it is prepared on a large scale by distilling Starch with Binoxide of Manganese and Sulphuric Acid.
Properties.—The strength of commercial Formic Acid is uncertain, but it is always more or less dilute. The strongest acid, as obtained by distilling Formiate of Soda with Sulphuric Acid, is a fuming liquid with a pungent odour, and containing only one atom of water. It inflames the skin in the same manner as the sting of the ant.
Formic Acid reduces the Oxides of Gold, Silver, and Mercury to the metallic state, and is itself oxidized into Carbonic Acid. The alkaline formiates also possess the same properties.
GALLIC ACID.
Symbol, C7H3O5 + H3O. Atomic weight, 94.
The chemistry of Gallic Acid is sufficiently described at [page 27], to which the reader is referred.
GELATINE.
Symbol, C13H10O5N2. Atomic weight, 156.
This is an organic substance somewhat analogous to Albumen, but differing from it in properties. It is obtained by subjecting bones, hoofs, horns, calves' feet, etc., to the action of boiling water. The jelly formed on cooling is termed size, or, when dried and cut into slices, glue. Gelatine, as it is sold in the shops, is a pure form of Glue. Isinglass is gelatine prepared, chiefly in Russia, from the air-bladders of certain species of sturgeon.