l6 FSSAYS AND OBSERVATIONS 



that of its refpeclive refidue, equalled, 

 ■with remarkable exactnels, the original 

 weight of the marie from which it haci 

 been extracted. 



SECT. V. 



THESE precipitated powders are 

 totally foluble in acid fpirits ; for it 

 was by this folution that we obtain- 

 ed their reparation from the other parts 

 of the marles in which they exifted. 

 1 he knowledge of this lingle property, 

 however, is not fufficient to determine 

 their nature. The changes produced up- 

 on, them by the adion of fire mud be 

 alio confidered. 



E X p .E R. xvr. 



For this purpofe, feventy grains of 

 powder, extraded, in the manner deicri- 

 bed above, from the marie of Experiment 

 3. were for two hours detained in a ftrong 

 fire. The weight of the powder was 

 thereby reduced to 40 grains, and its co- 

 lour 



