Mr Adie, On Bismuth. 24:3 



The non-volatile residue appeared to be concentrated in the 

 fractions of the precipitate which came down last, and this obser- 

 vation was checked by distillation of four fractions precipitated 

 by ammonia instead of potash. Thus in one case, the third 

 fraction weighing 46 gm. yielded 0"01 gm., and the fourth fraction 

 weighing 159 gm. yielded 0'3b' gm. of residue. 



The sulphates separating from concentrated sulphuric acid 

 were also distilled. In one case the sulphates separating out 

 from sulphuric acid saturated with bismuth oxide at 240° and 

 allowed to cool (i) from 240° to 170°, (ii) from 170° to 100°, 

 (iii) from 100° to 20°, were in the approximate ratio of 8 : 1 : 24. 

 These fractions were dissolved in nitric acid, precipitated by 

 ammonia and distilled in chlorine, but as they left residues this 

 method was abandoned. 



Lastly the beautifully crystalline sulphate Bi 2 3 , 4S0 3 , 7H 2 

 twice recrystallised, was treated as above and distilled in chlorine, 

 but left a small residue*. 



8. The method finally adopted was as follows :— 

 150 gm. of pure (B.P.) bismuth oxide were dissolved in 400 c.c. 

 of pure redistilled nitric acid (T42); to the clear filtered solution 

 were added about 5 litres of distilled water and 300 c.c. of 

 ammonia ('880). The precipitate was collected on linen, washed, 

 and dried (= B^), and represented nearly the first three fractions 

 (i), (ii), and (iii) above ; it contained about two-thirds of the 

 bismuth taken. The filtrate was then rendered alkaline by 

 ammonia, requiring about 100 c.c, and the precipitate (=R 4 ) was 

 filtered, washed, and dried in the same way and contained about 

 one-third of the bismuth taken. 



The dried precipitates were then placed in one-half of a long 

 wide combustion tube (about 1 metre long and of 2 cm. bore) 

 with a loose plug of glass wool in the middle, after removing any 

 loose fibres of glass. The tube was fitted with corks and single 

 tubes, one of which was connected with an aspirating bottle, and 

 the other with sulphuric acid driers. The tube was then gently 

 heated in a combustion furnace, and a gentle current of air 

 sucked through. Steam and nitrous fumes were given off and 

 the bismuth oxide was left dry, porous and completely oxidised. 

 When all nitrous fumes had been given off the temperature was 

 raised, a chlorine Kipp attached to the sulphuric acid drier and 

 a tube ending in a down draught to the other end. The current 

 of chlorine was regulated so that nearly all the bismuth chloride 

 condensed in the empty half of the tube which was not heated, 



* Mr K. C. Browning also showed that it was impossible to obtain bismuth 

 oxide free from this residue, by precipitation as sulphide. 



