DRIED ALUM 157 



lixiviated with water, and aluminum and iron sulphates 

 together with sulphuric acid are recovered in solution. The 

 solution is concentrated and to it is added potassium 

 chloride. The double sulphate of potassium and aluminum 

 (alum) is formed, which crystallizes out on cooling, while 

 potassium sulphate and ferric chloride remain as bye- 

 products. Alum is purified by recrystallization. 



Properties. — Large, colorless, octohedral crystals, some- 

 times modified by cubes, or in crystalline fragments ; without 

 odor, but having a sweetish and strongly astringent taste. 

 On exposure to the air the crystals are liable to absorb 

 ammonia and acquire a whitish coating. Soluble in 9 parts 

 of water. It is also soluble in warm glycerin ; insoluble in 

 alcohol ; reaction acid. 



Incomputibles. — Iron, lead and mercury salts, alkalies, 

 lime, tartrates and tannic acid. 



Dose.—K. & C, 3 ii.-iv. (8.-15.); Sh. & Sw., gr.xx.-3i. 

 (1.3-4.); D.,,gr.v.-x. (.3-.6); emetic, D., 3i. (4). 



Alumen Exsiccatum. Dried Alum. ALK, (SO,),. 

 (U.S.&B.P.) 



Synonym.— Alumen ustum, burnt alum,E.; alum calcine 

 (desseche brule), Fr.; gebrannter alaun, G. 



Derivation. — Heat 100 Gm. of alum moderately until 

 aqueous vapor ceases to be disengaged, and the product is 

 reduced to 55 Gm. 



Alumini Hydras. Aluminum Hydrate. X\{0'B),. (U.S. P.) 



Synonym. — Aluminum hydroxide, hydrated alumina, E.; 

 alumine, Fr.; thonerdehydrat, reine thonerde, G. 



Derivation. — Alum, 100 Gm.; sodium carbonate, 100 Gm.; 

 water, a sufficient quantity. Mix hot, boiling solutions of 

 alum and sodium carbonate. Precipitate strained, washed, 

 -and dried. 



Properties. — A white, light, amorphous powder ; odorless 



