260 Mr. F. E. Smith on Cadmium Amalgam* 



upper ascending curves show that the amalgam is completely 

 solid. 



It is evident, however, from the results given in Tables I. 

 to III. that the electromotive property of! an amalgam may 

 depend to some extent on its previous thermal treatment. 

 Whereas, originally, the E.M.F.'s of cells at 0° C. with 

 amalgams containing from 3 to 13*5 per cent of cadmium, 

 were nearly identical, we find after heating to 45° C. and 

 subsequent cooling that the limits are 3 and 14*5 per cent. 

 Similarly at 15° C. an approximate constancy of E.M.F. 

 was originally obtained with 5 to 14 per cent, amalgams, 

 but after the cells were raised to 45° C. and then cooled 

 to 15° the range was extended to 16 per cent, amalgams. 

 Hence it appears possible that if an amalgam rich in cadmium 

 is raised to a temperature at which the solid and liquid phases 

 are present, it may, on cooling, leave different electromotive 

 properties owing to the persistency of the tivo phases. This 

 persistency may be due to lack of homogeneity of the amalgam. 

 The curves in fig. 2 show that the amalgams containing from 

 9 to 17 per cent, of cadmium were partly liquid and partly 

 solid at 45° C, while the 18 and 10 per cent, amalgams were 

 fairly close to their transition temperatures. Referring to 

 Table III. and to the curves in fig. 2, we see that the 

 amalgams which show the greatest changes in their electro- 

 motive properties (these are the amalgams containing from 

 14 to 17 per cent, of cadmium) are partly liquid and partly 

 solid at 45° C, but are normally quite solid at 0° C. Other 

 amalgams containing 14, 15, 16, and 17 per cent, of cadmium 

 were prepared, and their general appearances before and 

 after heating to 45° C. were carefully noted ; there is no 

 doubt that these amalgams appeared to be more liquid after 

 the hea treatment. 2' he final appearance of the amalgams 

 is explained if we suppose that a Layer of amalgam of compa- 

 ratively low cadmium concentration surrounds a core of higher 

 cadmium concentration . 



The curves in fig. 2 are worthy of notice. The slopes of 

 the higher ascending curves are almost identical for the 

 temperatures 15° C. to 45° C, but only the upper part of 

 the higher curve at 0° 0. is approximately parallel to the 

 others. (To avoid confusion the curves for 5° and 10° are 

 not given.) Now if the upper part of the curve at 0° is 

 continued so as to be approximately parallel to the curves at 

 20°, &c, it meets that part of the curve corresponding to the 

 two-phase system at a point indicated by 11 per cent, of 

 cadmium. It is possible that the curve thus drawn was not 



