io°' The folution is then to be carefully poured off, and the 

 undiffolved mafs wafhed and fhaken in diflilled water; the whole 

 thrown on a filtre and fweetened as long as the water that 

 paffes through has any tafte ; the contents of this water, fhould 

 be precipitated by a folution of mild mineral alkali ; this 

 precipitate alfo being waflied and dried in a heat below rednefs 

 fhould then be weighed ; thus we have another method of finding 

 the weight of the calcareous matter. 



il"' The undiffolved mafs is next to be dried in the heat 

 already mentioned, and the difference between its weight and 

 the weight of the whole earthy mafs before folution fhould be 

 noted, as it furnifhes a third method of difcovering the weight 

 of the calcareous matter of which it is now deprived. Suppofing 

 this to amount to 150 grains, the weight of the undiffolved 

 refiduum fhould in the above cafe be 385 — 150=235 grains. 



I a"" Reduce the dried mafs into the fineft powder, throw it 



into a Florence flafk or glafs retort and pour on it three times 



its weight of pure oil of vitriol, digeft in a flrong fand heat, and 



at lal^ raife the heat fo as to make the acid boil; afterwards let 



it evaporate nearly to drynefs ; when cold pour on it gradually 



fix or eight times its weight of diftilled water, and after fome 



hours pour off the folution on a filtre ; the filtre fhould previoufly 



be weighed and its edges foaked in melted tallpw * ; the fubflance 



- oil} j.':f^i!o 



Vol. V. A a found 



- ' 'An ingenious contrivance of Dr. Black's. 



