This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
A sulphate of aluminium and potassium (potassium alum or potash alum), or of aluminium and ammonium (ammonium alum or ammonia alum), crystallised from solution in water, B.P.; a sulphate of aluminium and potassium, U.S.P. K2A12(SO4)4.24H2O; 948.
Reactions. - Its aqueous solution gives with caustic potash or soda a white precipitate soluble in an excess of the reagent (aluminium); and an immediate precipitate with chloride of barium (sulphate).
U.S.P. Large colourless octahedral crystals, acquiring a whitish coating on exposure to air; no smell, sweet astringent taste, and acid reaction.
Impurity. - Iron.
Test. - The solution in water does not acquire a blue colour from the addition of yellow or red prussiate of potash.
Dose. - 10 to 20 grains.