Disulphuret of Bismuth. 265 



then a cherry red for half an hour. The disulphuret weighed 719 

 grains. Bismuth is volatile at a bright red heat, which would ac- 

 count for the loss. To ascertain whether this mass was a definite 

 compound, the following analysis was made. 



Analysis. 



(a) 176 grains of the disulphuret of bismuth were treated with 

 nitric acid, a little diluted. Nitrous acid fumes were evolved in 

 abundance for a little time, and after a few hours the action had en- 

 tirely ceased. More acid was added, to be sure that all the bismuth 

 was oxidized and dissolved, but no further action was observed. 



(b) The solution (a) was carefully decanted from the lumps and 

 sediment of sulphur and sulphate of bismuth, and these latter re- 

 peatedly washed with water acidulated with nitric acid, to prevent 

 any precipitation of subnitratc. 



The sulphur and sulphate of bismuth, when dry, weighed 23.3 

 grains. 



The sulphur and sulphate by ignition lost 8.8 grains of sulphur. 



The remainder, which was sulphate of bismuth, contained 



Sulphuric acid, 4.833 = 1 .933 sul. > Acording to Thomson's 

 Oxide of bismuth, 9.667=8.700 bis. ^ atomic numbers. 



14.500 



(c) The solution and washings of (b) were precipitated by solu- 

 tion of carbonate of annnonia. The precipitate fell in abundance 

 after the excess of nitric acid was neutralized. The carbonate was 

 washed and dried, on its double filter, for several days, and the heat 

 for the last 48 hours was such as to begin to char the paper of the 

 filters. The dried carbonate of bismuth weighed 183.5 grains. 



(c') To ascertain the proportion of oxide of bismuth in the car- 

 bonate, 33.7 grains of the carbonate were gradually heated in a tube 

 to redness. Carbonic acid, water, and nitrous acid fumes were evol- 

 ved. The nitrous acid was small in quantity, and evolved at a red 

 heat, so that there must have been some subnitrate precipitated with 

 the carbonate. The loss of weight was 3.85 grains =11.424 per 

 cent. In another experiment, 6.8 grains lost 0.78 grains = 1 1 .470 

 per cent. The mean of these two losses is 1 1 .447 per cent. Had 

 the whole 183.5 grains of carbonate been heated, the loss would 

 have been 21.005; iience the 183.5 grains of carbonate of bismuth 

 contained 162.495 grains of oxide of bismuth = 146.245 of bismuth. 



Vol. XXVIl.— No. 2. 34 



