I 9 8 OF THE ASBESTINE EARTH. 



them, a green, or bright red. If an acid was 

 poured upon the green liquor, it \vas changed to 

 a red ; it* upon the red liquor, the colour was at 

 firft much heightened, but afterwards affuming 

 a yellowifh tint, became gradually fainter, and 

 at length wholly difuppcarcd. To the fmall 

 portions of magnefin, which almofl always ad- 

 heres to the charcoal, we may attribute all thefe 

 phenomena, as will be found explained elle- 

 \vhcre *. 



The powder thus prepared was boiled in aqua 

 regia, until all the foluble part of it was diflblv- 

 ed. The filiceous part remaining \\as collcded 

 in a filtre, and waflied in warm water. To the 

 folution concentrated by evaporation, fome 

 drops of flrong vitriolic acid were added ; and, 

 if after a quarter of an hour there were no figru 

 of terra ponderofa in it, a quantity cf the fame 

 acid iull'icicnt to faturatc the calcareous earth 

 was then pcurcd in, and, by a gentle evapora- 

 tion, almoit the whole of the gypi'iim was lepa- 

 ratcd. This being collected, the folution was 

 again difturbed by aerated alkali, and received 

 on a filtre : The precipitate was then wafhed; 

 :md, while yet moid, vitriolic/acid was gradual- 

 Iy added to it, umil none of it remained ex- 

 cept perhaps a fn tall portion of gypliiin that 

 fonictimes eluded the firfl icparatic;n. On boil- 

 ing the water of the precipitation, it depofu 



^ ted 



2 Vol. ?C 220, 



