Alumina: Alum Precipitated with Water of Ammonia and Calcined, Ure 1839

Alum is the earth of clay, alumina, joined to sulphuric acid and potash. Andrew Ure (1839): drop a weak alum solution into water of ammonia and a bulky white earth falls; washed, it is pure alumina hydrate. Calcined hot, it gives up its water and leaves alumina. Strong ammonia stings the eyes and lungs: work in the open with goggles. The picture: aluminium oxide on a watch glass.