Aluminium Hydroxide: Alum Solution Dropped into Ammonia Water (Ure 1839)

Drop a weak alum solution into ammonia water and a bulky white precipitate falls: aluminium hydroxide, which Ure called aluminous earth. Washed, it is the starting point for aluminium salts and for alumina. Result: a bulky white precipitate; dried, it weighs 10.82 % of the alum used. Ure dissolves it in acid while it is still moist. Source: Ure, Dictionary of Arts, Manufactures, and Mines (1839), Alum. Not given: how much ammonia water, its strength, how it is washed. Ours: work in fresh air, as ammonia fumes sting. Picture drawn by Youblob.