1891 .] to the Metallurgy of Bismuth. 79 



I stated in this paper that bismuth " frequently contains a small 

 proportion of copper, an element most detrimental even in small 

 traces, and hitherto only eliminated by a wet process, costly in prac- 

 tice and tedious in operation. It is necessary by such method to 

 dissolve up the whole of the alloy, and precipitate the bismuth, in the 

 usual manner a bulky operation, and one requiring a considerable 

 amount of time. It became therefore advisable, in order to treat 

 cupriferous bismuth rapidly and upon a commercial scale, to effect 

 this separation, it' possible, by means of a dry process." 



In further researches in the metallurgy of this interesting metal, 

 a case was found in which bismuth contained a very small proportion 

 of copper, under 0'5 per cent., but sufficient to render the metal use- 

 less, and in fact, to destroy those characteristic properties upon which 

 its industrial applications depend. 



Instead of treating this cupriferous bismuth by fusion with bis- 

 muth sulphide, which necessitates a temperature sufficiently elevated 

 to bring about a complete fusion of the bismuth sulphide, and conse- 

 quently, unless very great care be taken, great loss by volatilisation 

 of bismuth, it occurred to me to fuse the alloy, and, at a temperature 

 a little above its melting point, to add a small proportion of sodium 

 monosulphide. The mass was then stirred well, so as to bring every 

 portion of the fused alloy into contact with the fused sulphide. 



After about one hour's stirring, a test was made of the molten 

 metal, and it was found that the amount of copper in it was very 

 considerably decreased. 



By skimming off the film of scoria which had risen to the surface, 

 adding a further small proportion of the sodium monosulphide, and 

 continuing the operation of stirring, every trace of copper was 

 eliminated, and the bismuth so freed from copper rendered in every 

 way suitable for industrial use. 



The first experiment was made upon a quantity of 105 kilograms, 

 which yielded 94 kilograms of bismuth free from copper, and about 

 11 kilograms of skimmings containing the whole of the copper, their 

 bismuth contents of course being available for reduction with further 

 and larger quantities of skimmings as they accumulated. 



This process has been repeated upon very considerable quantities 

 of cupriferous bismuth, and has proved to be successful. 



This question of keeping the temperature low is of much import- 

 ance, for the lower the temperature the less tendency there is for the 

 bismuth to volatilise, and as it is necessary to obtain the bismuth 

 free from traces of impurity, which entirely change its nature, it will 

 be seen that any improvement in manipulation, or in the process 

 itself, which enables pure metal to be obtained possesses much 

 interest. 



