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Many of thofe fprings called acidulae, received 

 this name from the mephitic air we have already 

 mentioned. If this acid be prefent, it may be 

 difcovered by an . infufion of fyrup of violets, 

 or by an infufion of lacmus, or archil (w)> 

 which are turned of a brighter or reddifh color 

 by it. This acid may be detected alfo by a 

 folution of lead in the nitrous acid ; the folution 

 fhould be fully faturated. The nitrous acid 

 uniting with calcareous earth, or foflll alkali, 

 falls in a white fediment, while the vitriolic acid 

 combines with the lead, 

 b. In its volatile fulphureous ftate. (See page 



2. An alkali is alfo very feldom found in 

 water in its proper Itate. 



a. When zfoffd alkali is prefent, it is more nicely 

 detected by the fyrup of violets, or infufion of 

 lacmus, than the former, thefe being turned 

 green by the leaft portion of alkali. If a con- 

 fiderable quantity of alkali were combined with 

 the water, it might be precipitated by a folution 

 of calcareous earth, or by acids. 



t>. A volatile alkali may be diftinguilhed by a 

 folution of corrofive fublimate mercury in water, 

 or in the nitrous acid, the alkali rendering the 

 folution white, a precipitation of a white powder 

 enfues ; but no change is produced, when the 

 alkali is the fixed or foflll, or if any, the mer- 

 cury will be precipitated in an orange, brown, 



(<u>) This is fo nice a teft, that even mephitic air is apt 

 to give it rather a brighter color. 



faince the firft edition, Dr. Prieftley makes a fimilar ob- 

 fcrvation on the authority of his correipondent M. Bregman 

 of Upfal. Philosophical Tranfactions, Vol. LXII. 1773. 



or 



