in the Isle of Wight, 231 



m tlie rixivlura 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 ap- 

 peared, both circumstances showing that all the alumine was preci- 

 pitated. This precipitate being dissolved in muriatic acid, in order, 

 to separate a minute portion of silica, which it contained*, and being 

 again precipitated by succlnat of ammonia with excess of ammonia, 

 formed a gelatinous mass, which being edulcorated, dried, and ulti- 

 mately 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 succlnat of ammonia, were omitted, 

 the gelatinous precipitate, heated to redness, weighed 1, 4 grains f, 

 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, 1 was 



* 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. 



+ 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 

 pulverized glue, an appearance which is well knowa to characterize alumine. 



