Prof. W. H. Miller on the Form of an Alloy of Bismuth, 49 



The plane angles of the face c are 72° 17' and 107*^ 43'. 

 Twins. Twin-face c. 



Cleavage, c, very perfect and easily obtained. 



Analysis. 



Specific gravity = 9*46. 



A well-crystallized portion of it was reduced to powder, ex- 

 amined in the usual manner, and found to consist of sulphur, 

 bismuth, copper, and nickel. 



Estimation of Sulphur. — 10*43 grs. were digested in warm 

 nitric acid, till the sulphur which separated had melted into a 

 globule. Weight of sulphur globule 0*19 gr. It was roasted, 

 and the residue weighed 0*04 gr. This was dissolved in nitric 

 acid and added to the original solution, from which the sulphuric 

 acid was precipitated and weighed as sulphate of baryta. Weight 

 of sulphate of baryta obtained 1'05 gr. 



Estimation of the Metals. — 10*43 grs. were dissolved as above, 

 the solution diluted, and a current of sulphuretted hydrogen 

 passed through it. The sulphurets were collected on a filter, 

 and washed with acidulated water containing sulphuretted hy- 

 drogen. The nickel was precipitated as oxide by caustic potash, 

 reduced by hydrogen, and weighed as metal 0*59 gr. 



The sulphurets were dissolved in nitric acid, and the bismuth 

 separated from the copper by means of carbonate of ammonia. 

 The treatment with carbonate of ammonia was repeated in order 

 to remove the last traces of copper from the precipitated bismuth, 

 which was ignited and weighed 10*27 grs. 



The ammoniacal filtrate was evaporated to dryness and the 

 ammoniacal salts expelled. The residue was dissolved in nitric 

 acid, and the copper precipitated as oxide by caustic potash. 

 Weight of oxide of copper 0*30 gr. 



Results tabulated. 

 Bismuth .... 88-49 

 Nickel .... 5-65 

 Copper .... 2-29 

 Sulphur .... 2*82 

 99*25 

 Estimating the sulphur in combination with the copper and 

 a portion of the bismuth, and considering these sulphides as 

 foreign matter, the formula will be very nearly that of NiBi^, 

 the atomic weight of bismuth being taken as 208. 



Phil. Mag, S. 4. Vol. 12. No. 76. July 1856. E 



