Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/243

in the lixivium rather than actually dissolved; for the solution being left at rest for some time, these particles subsided.

2. To the clear alkaline solution, muriat of ammonia was added, till no further precipitate took place; the precipitate was edulcorated and collected in a filter. It was white and gelatinous. Caustic potash being added to the clear fluid, ammonia was disengaged, showing that it contained an excess of muriat of ammonia; and acetic acid being added to another portion of the same liquor, no turbidness appeared, both circumstances showing that all the alumine was precipitated. This precipitate being dissolved in muriatic acid, in order to separate a minute portion of silica, which it contained^[1], and being again precipitated by succinat of ammonia with excess of ammonia, formed a gelatinous mass, which being edulcorated, dried, and ultimately heated to redness, weighed 2,4 grains.

3. Another portion of residue, weighing thirty grains, being treated in a manner exactly similar to that just described, with this exception, that the redissolution of the alumine in muriatic acid and its subsequent precipitation by succinat of ammonia, were omitted, the gelatinous precipitate, heated to redness, weighed 1,4 grains^[2], which afforded as close a coincidence with the former result as may be well expected: in processes of this kind.

4. Having never been able to obtain, by the mere evaporation of the water, any appearance of crystals resembling alum, I was

1. The particulars of the manner in which the silica is separated, by the intervention of muriatic acid, will be detailed under the head Silica, in another part of this paper.
2. The real weight was 1,6 grains, but 0,2 grains were deducted, on account of the quantity of silica known, by other experiments, to have been present, as will be seen under the head Silica. It may be proper to mention, that the gelatinous precipitate, during its gradual desiccation, shrunk into small fragments resembling coarsely pulverised glue, an appearance which is well known to characterize alumine.