iron alum
a. Min. A double sulphate of iron and aluminium (see alum n. 2), occurring native as halotrichite. b. Chem. A double sulphate of iron and potassium (or ammonium), belonging to the series of alums in the extended sense: see alum n. 3).
| 1868 Dana Min. 654 Halotrichite..Iron Alum. 1868–72 Watts Dict. Chem. V. 596 Ammonio-ferric sulphate, or Ammonia-iron-alum..Potassio-ferric sulphate, or Potash⁓iron-alum. 1876 Harley Mat. Med. 192 Iron alum results when the alumina is replaced by peroxyde of iron. |