in the Pyrites. 233 



him, that when the formality of this experiment con- 

 filled only in removing an acid fait, and the vege- 

 table fatrinefs acted here as an alcali •, this fattinefs, 

 as fuch, and in its unaltered ftate, cannot befaid to 

 effefr it-, but may, when in thecourfe of the ope- 

 ration it becomes reduced to an actual afh, and 

 thus to an alcaline (late. For, oil and fat, as fuch, 

 remove no acid ; but confiding themfelves moftly 

 of fuch, encreafe its quantity rather 5 but a lixivious 

 fait effects it. 



Still feveral difficulties offer that oppofe a poli- 

 tive declaration from Lemery's opinion. 



(i.J There will be requifite a much greater 

 quantity of alcali to obtund a certain quantity of 

 acid ; and in loam, by his own conceffion, there is 

 much acid. Again, what quantity of alcali afhes 

 doeslinfeed oil afford 5 nay, how much pure alcali 

 is procured from the alhes ? 



(2. J Why are not metallic earths reducible with 

 pot-afh and the like -, and fan* cornua, not again to 

 filver, but much, nay almoft all of it loft, when 

 repeated by trials with alcali : whereas pitch, far, 

 rofin, 2nd the like do, under proper treatment, re- 

 duce all the filver back to its metallic form : and 

 yet, in the one cafe, fuch fatty matters fcarce 

 in their whole fubftance and weight amount to fo 

 much, as does the pot-afh employed in the other, 

 tho' without any effect: and the leaft quantity of 

 coal-duft reduces my antimonium diapboreticum, as 

 ai.o my vitrum antimonii : whereas the former floats 

 in the alcali, and under due cover and fcreen from 

 coal-duft, for ever remains an earth, or goes foon- 

 er off in fume. 



What- 



