BISMUTH. 
§ § 54 -] 
§ 854. Estimation of Bismuth. —The estimation of bismuth, when in 
any quantity easily weighed, is, perhaps, best accomplished by fusing the 
sulphide, oxide, or other compound of bismuth in a porcelain crucible 
with cyanide of potassium ; the bismuth is reduced to the metallic state, 
the cyanide can be dissolved out, and the metallic powder washed (first 
with water, lastly with spirit), dried, and weighed. 
Mr Pattison Muir has shown 1 that bismuth may be. separated from 
iron, aluminium, chromium, and manganese, by adding ammonia to the 
acid solutions of these metals. 
This observation admits of many applications, and may be usefully 
taken advantage of in the separation of bismuth from the nitric acid solu¬ 
tion of such animal matters as liver, etc. The acid liquid is partially 
neutralised by ammonia, and, on diluting with warm water containing a 
little sodium or ammonium chloride, the whole of the bismuth is precipi¬ 
tated as oxychloride, which may be collected, and fused with cyanide of 
potassium, as above. 
If the bismuth precipitate is in small quantity, or if a number of 
estimations of bismuth are to be made, it is most convenient to use a 
volumetric process. In the case first mentioned, the oxychloride could 
be dissolved in nitric acid, sodium acetate added in excess, and sufficient 
acetic acid to dissolve any precipitate which has been produced, and 
then titrated by the following method, which we also owe to Mr Pattison 
Muir:— 
Estimation of Bismuth by Potassium Dichromate. 2 —A solution 
of recrystallised potassium dichromate (strength, 1 per cent.) is 
prepared. A known weight of pure bismuthous oxide (Bi 2 0 3 ) is 
dissolved in excess of nitric acid, and a solution of sodium acetate is 
added to this liquid until a copious white precipitate is thrown down ; 
acetic acid is then added in quantity sufficient to dissolve the precipitate 
completely, and to ensure that, when the liquid is made up with water 
to a fixed volume, no precipitate shall be formed. A certain volume of 
this liquid is withdrawn by means of a pipette, placed in a beaker, and 
heated to boiling ; the potassium dichromate is then gradually run 
in from a burette, the liquid being boiled between each addition of 
the solution, until a drop of the supernatant liquid gives a faint reddish- 
brown coloration when spotted with silver nitrate on a white slab. 
Another very generally applicable volumetric method for bismuth has 
been proposed by Mr Muir. 3 This depends on the fact (observed by 
Sonchay and Leussen), 4 that normal bismuth oxalate splits up on boiling 
into a basic oxalate of the composition Bi 2 0 3 2 C 2 03 + 0II 2 , but slightly 
soluble in nitric acid. The process is performed by precipitating the 
bismuth by excess of oxalic acid, dissolving the precipitate (first purified 
1 Pattison Muir on “ Certain Bismuth Compounds,” Journ. Chem. Soc., p. 7, 1876. 
2 Ibid., p. 659, 1879. 3 Ibid., 1877. 4 Ann. Chem. Pharm., cv. 245. 
