254 Mr. F. E. Smith on Cadmium Amalgams 



(3) A large number of the vessels may be grouped together 

 and the positive poles connected. The difference in 

 E.M.F. between any two negative poles, even though 

 they be in different cells, may thus be directly 

 measured. 



(1) If there is any doubt about small differences in E.M.F. 

 and a suspicion that they are due to slight differences 

 in the depolarizers, the 10 per cent, amalgam poles 

 may be connected together, and the differences in 

 E.M.F. measured between these and other amalgams. 

 (Preliminary observations had proved the reliability 

 of the 10 per cent, amalgam.) 



(5) The cells may be immersed in ice, water, oil, or other 

 liquid, and they cannot leak through the junction of 

 platinum with glass. 



Preparation of the Materials. 



The cadmium sulphate, the mercury, and the mercurous 

 sulphate were prepared by methods which are fully described 

 -elsewhere 12 . 



The cadmium was from various sources. Some was 

 purchased from Messrs. Baird and Tatlock ; another lot 

 was from Messrs. Harrington's and further samples were 

 procured from Kahlbaum's and Merck's. In addition, a 

 considerable quantity was prepared by electrolysing pure 

 cadmium sulphate, an anode of commercially pure cadmium 

 and a cathode of platinum being used. 



The Cells. 



The cells experimented with are divided into groups, the 

 division being due partly to the heat treatment of the 

 amalgams, and in part to the source of the cadmium. 



Group I. — Cadmium from Baird and Tatlock. 



Range of amalgams : — 1 to 20 per cent, of cadmium. 



Manufacture : — Three amalgams were first made ; these 

 contained 20, 15, and 10 per cent., respectively, of cadmium. 

 All oxide and dross was removed by washing with very dilute 

 sulphuric acid while the amalgams were hot and completely 

 liquid. Each amalgam was then chilled with ice-cold water 

 and broken into small pieces. From the 20 per cent, amalgam 

 other amalgams estimated to contain from 19 to 16 per cent, 

 of cadmium were made ; the 15 per cent, amalgam was 



