fome Mineral Subjlances. 1 9 
it into an iron mortar. This matter in its fracture has 
appearances of rulandus’s falfe liver of antimony. 
I have alfo tried, in the fame proportion and manner, 
the following fubftances, and found the effects fo much 
alike, that they could be fcarcely diftinguifhed one from 
the other. 
Stellated fpar, from the ifland of Sheppy. 
Auvergne compact plated fpar. 
Erica formed fpar. 
Whited plated gypfum dried. 
Dried whiting. 
Fixed alkaly of tartar. 
Hence we may conclude, that the calcareous earth of 
thefe fpars and gypfum a£t on the antimony like fixed 
alkaly, forming a fort of liver of antimony. 
Of fome mineral fubftances which contain the earth of 
allum. 
Tobacco-pipe clay, of all fubftances I know, would 
be the fitted; to make allum with, was it neceflary ; but 
nature has fupplied it abundantly in other bodies, from 
which it is obtained with little art and expence. 
Two drams of dried tobacco-pipe clay, treated with an 
equal quantity of fixed alkaly of tartar, as in the laft ex- 
D 2 periments, 
