The purified air-dried product of the hydrolysis of certain • animal tissues, as skin, ligaments and bones, by treatment with boiling water.

An amorphous, more or less transparent solid, usually shredded or in thin sheets; colorless or with a slight yellowish tint, inodorous, and having a slight, characteristic, almost insipid taste. Unalterable in the air when dry, but putrefying rapidly when moist or in solution. Gelatin is practically insoluble in cold water, but swells and softens when immersed in it, gradually absorbing from five to ten times its weight of water. It is soluble in boiling water, acetic acid and glycerin, but is practically insoluble in alcohol, ether or chloroform.

Incompatibilities: Gelatin is coagulated by tannin, chlorin, bromin, and mercuric chlorid. If a solution of gelatin be mixed with formaldehyd, the gelatin is rendered hard and insoluble after evaporation and drying of the residue.

Action and Uses: Gelatin is largely used as a food product, though its full value in this respect has probably been exaggerated. It has also been used to some extent in solution for hypodermic injection to promote the formation of clot in aneurysms, and to arrest hemorrhage. There is, however, serious danger of infection from its use. Even boiling will not insure sterility as it may contain tetanus spores which are not destroyed by simple boiling. In pharmacy gelatin is used for the coating of pills, the making of gelatin capsules, gelatin disks, glycogelatin pastilles and for the making of glycerinated gelatin used as a base for suppositories.