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ALU M. 



Vitriolic Acid combined with argillaceous 

 Earth. 



Synonymous Names, 

 f Argillaceous vitriol. 

 ALUM. < Aluminous fulphate. 



^Sulphate of alumine. 



Alum has a very aflringent and acid tafte ; its 

 cryftals are of the figure of an o&ohedron; it is 

 very rarely found in mineral waters. 



A. a. The earthy bafis may be detected by 

 the addition of lime water, which occafions a 

 turbid appearance, and a flaky precipitate will 

 be gradually formed, which is the earth of alum. 

 The vitriolic acid, uniting with the calcareous 

 earth of the lime water, forms Gypfum, which 

 is more foluble in water. 



b. A folution of alkali, either cauftic or 

 mild, vegetable, foffil, or volatile, added to 

 aluminous water, produces a white flaky ap- 

 pearance. The alkali combines in the fame 

 manner with the vitriolic acid, and precipitates 

 the earth of alum, either alone or combined 

 with fixed air, leaving vitriolated tartar, Glau- 

 ber's fahs, or volatile ammoniac, according to 

 the alkali made ufe of, diffolved in the water. 



c. By adding a folution of foap, the alumin- 

 ous water becomes turbid, and depofites a num- 

 ber of white flakes, the alkali of the foap unit- 

 ing 



