rock alum
[rock n.1]
(See alum n. 1 and roche alum.)
| 1671 Phillips s.v. Allum, Called Roch or Rock Allum. 1678 R. Russell tr. Geber iv. iv. 246 Glassy or Rock Allom hath a two fold way of Preparation. a 1756 Mrs. Heywood New Present (1771) 263 A pound of rock-allum, burnt and beat to powder. 1806 W. Turton Linnæus' Syst. Nat. VII. 221 Alumen romanum, Rock alum. 1860 Piesse Lab. Chem. Wonders 107 The name rock or roche alum indicative of good quality. 1875 Encycl. Brit. I. 644/2 The term rock alum, commonly employed in Europe. |