[ 93 ] 



were carefully colleded on filtering papers; thefe, with 

 the powders upon them, were dried and weighed ; the papers 

 were then exadly cleared of the powders, and again weighed ^ 

 by this means the refiduum of a was found to be 7, 9 grains ; 

 of ^. 6,6 grains, and of f 8, 3 grains; fo that four ounce 

 meafures of pure lime water diflblved of litharge 2, i grains, 

 of calx 3, 4 grains, and four ounces and a half of the fame 

 liquor diflblved, 1,7 grains of minium. All the filtered liquors 

 ftruck a deep black colour with hepatic air, and let fall a white 

 precipitate on the addition of marine acid. 



To the produdion of the black precipitate, afforded by hepatic 

 air, the prefencc of atmofpheric, or rather vital air, appears to 

 be necefTary, as may be inferred from the following obferVation : 

 Hepatic air was generated in the phial D, 

 to the fide of which was adapted the bent 

 tube E, whofe extremity, plunged to the 

 depth of between two and three inches 

 under the furfacc of the liquors above- 

 mentioned, which were feverally put into 

 the fmall glafs jar F. The phial being then flopped, the ftrcam 

 of hepatic air, ifTuing through the tube, pafled through a con- 

 fiderable part of the liquors and efcaped at their furface; 

 there the black colour firft appeared ; the tranfparcncy of the 

 lower parts was not difturbed, unlefs by the fubfidencc of the 

 precipitate formed at the top. 



The fame conclufion is fuggefled by the following obfervation. 

 On lifting up the tubulated phial, part of the liquor remained 



fufpended 



