Alum

(aV-tin i) \alumen, alum]. Anyone of a cla of double sulphates formed by the union of one of the sulphates of certain non alkaline metals with a sulphate of some alkaline metal. The standard (or common ALUM EN commercial) alum, the official A lumen, U. S. P., is the aluminium-pota ium sulphate, A12(S04)3 + K2S04 + 24H20. It is a powerful astringent and styptic, and is also extensively used in the arts. A., Ammonia, is the same as the above, except that the pota ium is replaced by ammonium. It is official in Great Britain, and is extensively used on account of its cheapne . What is known as concentrated or patent alum, is the normal aluminium sulphate (alumin i i sulphas), which is not a true alum. A., 47