Characters. - A white, light, amorphous powder, permanent in dry air, odourless, and tasteless.

Solubility. - It is insoluble in water or alcohol.

Reactions. - Soluble without residue in hydrochloric or in sulphuric acid, also in solution of potassa or of soda.

Uses. - It is feebly astringent and desiccant. Is used externally as a powder in inflammatory diseases of the skin.