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The humid way afFoided a ftlll further 

 elucidation. Having reduced to powder 

 twelve ounces of the black, and twelve of 

 the fpotted glafs of Lipari, they were left 

 feparately during twelve hours in digeftion 

 with heat in diftilled water. The water, 

 when filtrated, did not in the leafl: change 

 the colour of the tincture of turnfole ; a 

 proof that in it there either exifted no acid" 

 difengaged, or that it was extremely weak. 

 On trying the fame v/ater wiih nitrate of 

 filver, a flight turbidnefs was produced ; 

 and, after four-and-twenty hours, an ex- 

 tremely fmall fediment. 



As I knew that the muriatic acid, though 

 weak, always produces white fleeces or 

 ftreaks in the folution of the nitrate ot filver, 

 I entertained feme doubt whether this tur- 

 bidnefs might be the effed: of this acid ; 

 and, to remove it, I refolved to try whether 

 a fimilar turbidnefs, but without fleeces or 

 rtreaks, might not be produced by nitrate 

 of filver in diftilled water in which a drop 

 of muriatic acid had been infufed. On 



making 



