Contractions. - Alumen. Aln.

Present name. - Potassio-Aluminic Sulphate. Ka12so4, 12H1O.

Common Alum. For. names: German, Alaun; French, Alun; Italian, Allume; Spanish, Alumbre.

Of late years the Ammonia Alum has largely taken the place of Potash Alum in commerce; but as the prov-ings were made with the Potash salt, we must continue to use it.

It can be obtained from the manufacturing chemists.

Characters and Tests. - Colourless, transparent, crystalline masses, exhibiting the faces of the regular octohedron, and having an acid, sweetish, astringent taste. Its watery solution gives with Caustic Potash a white gelatinous precipitate, which is soluble in an excess of the re-agent, an immediate precipitate with Chloride of Barium, and after some hours a crystalline precipitate with Tartaric Acid. Boiled with Caustic Potash, no ammoniacal odour is given off.

Preparation. - Solution in distilled water for the first 3 dilutions, then dilute alcohol for 4, and afterwards rectified spirit.

Reference to Horn. Proving. - Marcy and Peters' New Mat. Med.

Proper forms for dispensing. - lx to 3, watery Solution only. 4, dilute Tincture only. 5 and upwards, Tincture, Pilules, or Globules.