Gallic Acid. H3C7H3O5H1O.

A crystalline acid prepared from Galls, which are excrescences on Quercus infectoria, caused by the punctures and deposited ova of Diplolepis Galloe tinctorioe.

It may be obtained pure from the operative chemists.

Characters and Tests. - Crystalline, in acicular prisms or silky needles, sometimes nearly white, but generally of a pale fawncolour. It requires about 100 parts of cold water for its solution, but dissolves in 3 parts of boiling water. Soluble also in rectified spirit. The aqueous solution gives no precipitate with solution of Isinglass. It gives a bluish-black precipitate with a Persalt of Iron. The crystalline acid when dried at 212° loses 9.5 per cent. of its weight. It leaves no residue when burned with free access of air.

Homoeopathic uses. - These are given in Marcy and Peters' New Mat. Med.

Preparation. - Solution in rectified spirit.