104 On (In- />///"/'- Gold in ,W?V/ Lead. 



I stated that I was "trying to ascertain whether diffusion in the solid 

 metal is, or is not, accelerated by the simultaneous passage of a strong 

 electric current." I again referred to the subject in answer to Lord 

 Kelvin during the discussion which followed the reading of the present 

 paper, and stated that the experiments were incomplete. Su<-h experi- 

 ments take a long time, and it may be well to add that the arrange- 

 ment was just as is described above, except that the lead ordinarily 

 used for assaying was employed. Two cylinders, each - 88 cm. in 

 diameter, with gold clamped to their respective bases, were maintained 

 at a temperature of 150 for 544 hours, beginning on the 31st of 

 January of the present year. A current of 1-5 amperes was passed 

 through one of the cylinders only during the whole time, the current 

 passing from the gold to the lead. The amount of gold which had 

 diffused into each of the lead cylinders was then ascertained by the 

 method which has already been described. Gold was detected at a 

 height of 7'5 mm. in the case of the cylinder through which the current 

 had passed, while in the other case with no current it had reached a 

 height of 10 mm., the amoxint of gold in each section being also greater. 

 Subsequent experiments showed that a part at least of this difference 

 was due to imperfection in the contact between the lead and the gold. 

 Other experiments are now in progress in which far greater current 

 densities are employed. 



If these experiments confirm the previous one, they will show that a 

 solution of gold in lead does act, to a small extent, as an electrolyte. 

 The following method was adopted for ensuring contact between the 

 gold and the lead : 



My assistant, Mr. W. H. Merrett, succeeded in joining by fusion 

 discs of gold between two cylinders of lead, as is shown in the accom- 

 panying figure. Contact between the metals is, therefore, above re- 



proach, but it will be many weeks before the results can be recorded. 



Thirteen years ago I was unsuccessful in the attempt to electrolyse a 

 solution of gold in metallic lead by the passage of a current of 300 

 amperes through the molten mass.* The failure may have been due 

 to the fact that at the high temperature produced diffusion must have 

 been very rapid. If, therefore, separation of gold from the lead did 

 take place, uniformity of the solution may have been restored by diffu- 



British Association Report, 1887, p. 341. 





