Alum, I′ron (-ŭrn). Syn. Alu′men Fer′ricum, Sul′phas fer′ri et potas′sæ, Fer′ri perox′idi potassio-sul′phas, &c., L.
Comp. K2SO4 . Fe2(SO4)3.24Aq.
Prep. Take of peroxide of iron, 9 lbs.; sulphuric acid 14 lbs.; dissolve, dilute the mixture with water, q. s., and add of potassium sulphate, 10 lbs.; evaporate, and crystallise.
Prop., &c. Crystals, beautiful octahedrons of a pinkish or pale violet colour. It is strongly recommended, by Dr Tyler Smith, as a chalybeate tonic, and has been used by him, at St. Mary’s Hospital with marked success. It has also been used as a mordant, in dyeing black.—Dose, 1⁄2 gr. to 5 gr.
Alum, Ro′man. Syn. Red alum*, Roach A., Roche A., Rock A.*; Alu′men Roma′num, A. ru′brum, A. ru′peum, &c., L.; Alun Romain, A. de roche, Fr.; Alume di rocca, It. In small fragments, covered with a reddish powder (ALUMEN RUBRUM VE′′RUM); originally imported from Civita Vecchia, where it occurs native. It is much esteemed by dyers from being nearly free from iron-alum. That now sold for it in England is ordinary alum coloured with Venetian red, Armenian bole, or rose-pink (ALUMEN RUBRUM SPU′′RIUM). This is done by shaking the fragments in a sieve over a vessel of hot water, and then stirring them up with the colour, until the surface is uniformly tinged with it. In genuine roach-alum the colour not only covers the surface, but also partially pervades the substance of the crystals. The name was formerly also applied to a pure white variety of alum, prepared at Tolfa; but it is now, in English commerce, exclusively given to common alum artificially coloured.
Alum, Saccharated. Alum, 6 oz., white lead 6 drms., sulphate of zinc 3 drms., sugar 11⁄2 oz. Mix the ingredients reduced to powder into a paste, with vinegar and white of egg. Used in eye waters and cosmetic washes.
Alum, So′da. Syn. Sulphas aluminæ et sodæ, L. Comp. Na2SO4 . Al2(SO4)3 . 24Aq. An alum in which the potassium sulphate of common alum is replaced by a like salt of sodium. It does not occur in commerce. (Vide suprà et infrà.)
ALUM-EARTH. Alumina.
ALUM MOR′DANTS. In dyeing, mordants having for their basis either common alum or the acetate or sulphate of aluminum. See Alums and Mordants.
AL′UM-ROOT. Syn. Amer′ican san′icle; Heu′chera (Ph. U. S.), L. The root of heuchera America′na (Linn.), a plant of North America. It is powerfully styptic and astringent; and is used chiefly as an external application in cancer.