Formula: Al (NH4) (SO4) 2 × 12H2O
Alum alyumoammoniynye single crystals are also called "aluminum ammonium disulfate." Alum is a double metal salts, and alyumoammoniynye appear as white crystalline powder. Water soluble but is not soluble in alcohol.
Ammonium disulfate aluminum is used in many areas: in the manufacture of paper, as an external medical device in the preservation of wood furniture and wood building materials, chemical industry in the production of corundum (synthetic crystals). In the leather and textile industry is used as a tanning agent.
Alum does not pose a health risk, but when dealing with them should pay special attention to personal hygiene and work only with rubber gloves from constant contact with alum skin begins to coarsen.