[ 275 3 



he ufed an earthen retort, as he fimply heated it to rednefs, whereas 

 a ftrong white heat is requifite to expel fixed air from chalk, 

 2 CrcU. Beytr. 199. I -believe unpurified fal ammoniac would yield 

 more aerated vol-alkali than the purified, on account of the oil it 

 contains, which affords fixed air. Another certain proof that 125; 

 grains chalk are not aclcd upon by the acid contained in the 100 

 parts fal ammoniac, but contribute to the increafed quantity of 

 aerated alkali merely by the fixed air expelled from them by heat, 

 is that the refiduum contains fome calcareous earth which the acid 

 had not attacked, as Richter has obferved, i Stock. 2 Theile 98 

 and 99. 



Several important deduflions may be deduced from the know- 

 ledge of the compofition offal ammoniac, for inftance, an eafy ex- 

 plana'ion of its great refrigerating power, &c. which being impro- 

 per for this place, I omit. 



Vitriolic Ammoniac. 



100 grains of cryftallized vitriolated vol-alkali and 300 dry flacked 

 lime, pneumatically diftilled in a pneumatic apparatus and a ftrong 

 fand heat, Bar. 30,2, Therm. 66^, afforded 78,41 cubic inches of 

 alkaline air, = 14,24 grains. 



M m 2 Prom 



N 



