Examination of a Native Sulphur et of Bismuth. 31 



bismuth was prepared, and the three following experiments 

 tried with it: one quantity was precipitated by potassa in great 

 excess, another by ammonia, and these were digested at a 

 boiling heat for about six hours ; the third portion was added 

 gradually to a large quantity of very hot solution of potassa; 

 and the whole three collected and well washed, dissolved in 

 nitric acid and tested as before; muriatic acid was however 

 detected in each. It was evident from these results, that mu- 

 riatic acid could not be employed in the analysis, or that, if 

 employed, it must be separated before the precipitation of 

 the oxide of bismuth. 6*88 grs. of the mineral were digested 

 in nitric acid as long as any sulphur remained undissolved ; it 

 was then filtered, and gave '345 gr. silica. The sulphuric 

 acid was next separated by a solution of nitrate of baryta added 

 as long as any precipitate was occasioned, and the sulphate of 

 baryta, after heating to redness, weighed 9*654? grs. After the 

 excess of baryta had been carefully removed, ammonia added 

 in excess threw down the oxides of bismuth and iron as be- 

 fore, and held the oxide of copper, which was obtained in the 

 manner before stated, and equalled *306 of a grain. The weight 

 of the mixed oxides was 5**594 grs., which were then dissolved 

 in muriatic acid, and a current of sulphuretted hydrogen passed 

 through the solution, and the whole thrown upon a filter : the 

 clear solution which passed through was boiled for some time, 

 and after the addition of a little nitric acid to bring the iron 

 to the state of peroxide, ammonia was added, and the oxide 

 collected weighed '344 gr. ; deducting this from the weight of 

 the mixed oxides, leaves 5*25 grs. as the quantity of oxide of 

 bismuth ; the results are, therefore, 



Oxide of bismuth 5*25 = 4*718 bismuth. 



Sulphate of baryta.... 9*654 = 1*309 sulphur. 



Peroxide of iron *344 = *241 iron. 



Peroxide of copper... '306= *245 copper. 



345 silica. 



6*858 

 022 loss. 



6*880 



Or, we may consider the mineral to be constituted of 5*7815 

 grs. sulphuret of bismuth, being in the proportion of 1 atom 

 bismuth -f 1 atom sulphur, and that the iron, copper, and 

 silica are merely parts of the matrix which cannot be sepa- 

 rated mechanically from the pure mineral. 



IX. Re- 



