of Mineral Substances. 37 



of a grass-green saline mass, which was redissolved and largely 

 diluted, by which a milky mixture was obtained ; this was set 

 aside in a warm place, where it deposited a white precipitate, 

 which was collected, washed and dried by heat: it weighed 94 

 grains. 



c. To determine the proportion of metallic bismuth contained 

 in this precipitated oxide, 100 grains of pure bismuth were di- 

 jested in muriatic acid, nitric acid being gradually added till 

 the metal was dissolved ; this solution was then evaporated in 

 a sand heat to a saline mass, which was put into a large quan- 

 tity of water, and the precipitate washed and dried as before ; 

 it weighed 122 grains. The remaining acid liquor was neutra- 

 lized with carbonate of potassa, by which a further portion of 

 oxide of bismuth, amounting, however, only to ^ grain, was 

 obtained. So that it appears from this experiment that the 94 

 grains of precipitate obtained in the analysis from 200 grains 

 of the ore, are equivalent to 77 grains of bismuth. 



d. The filtered liquor remaining after the separation of the 

 oxide {b), was of a blue colour ; it was saturated with potassa to 

 separate the copper, which, though at first thrown down in the 

 form of a blue precipitate, became, after having been some time 

 gently heated, of a brown colour ; it was collected, edulcorated, 

 dried, and ignited, and was then found to weigh 70.75 grains, 

 equivalent to 56.5 grains of copper. 



Hence, 200 grains of this ore have yielded 



Bismuth 77 grains 



Copper 56.5 



Sulphur 20.5 



Silica 87 



191 

 But as the silica is to be considered as derived from ihe 

 quartzose matrix of the ore, the components afforded by 100 

 parts of the pure ore will stand thus — 



Bismuth 47.24 



Copper 34.66 



Sulphur 12.58 



94.48 



