RESULTS WITH CADMIUM AMALGAMS. 



49 



All these points lie upon a very satisfactory curve except point 4. It will 

 be remembered that this amalgam was prepared outside the cell, as were 

 Nos. 1, 2, and 3. The result shows that clearly amalgam 4 was dilute 

 enough to begin to show the effect of oxidation, like that found in the case 

 of zinc. On the other hand, oxidation has evidently not caused an appre- 

 ciable error in the ordinate 3; hence points (7) and (8), based upon point 

 (3), are right also. The curve is plotted in figure 8. 



Attention is called to the fact that this curve of potentials is very similar 

 in form to that of zinc, except that the sign of its curvature is exactly oppo- 

 site. This point will be discussed later. 



0.2 



0.4 



0.6 



0.8 



log 2 log4 



log8 



log 16 log 32 log 64 



Fig. 8. Results with Cadmium Amalgams. 



Deviations from the theoretical potential are plotted as ordinates; logarithms of 

 the concentration-ratios as abscissae. The most concentrated amalgams at the origin 

 contained 2.95 per cent of cadmium. 



THE TEMPERATURE COEFFICIENT OF AMALGAM CELLS. 



Three pairs of cadmium amalgams were investigated with great care at 

 30 , at 1 5 , and o. The warm thermostat (described above) maintained 

 its temperature within one-hundredth of a degree. The intermediate bath 

 had a cold-water coil more than sufficient to compensate for the warming 

 effect of the surroundings; the adjustment of temperature was accom- 

 plished by an incandescent lamp with the usual electric cut-off. The lowest 

 temperature was attained in a large zinc trough surrounded by cotton wool 

 and placed inside a wooden box ; clear ice, finely divided and nearly covered 

 with distilled water, was used to maintain the temperature constant at o C. 



All temperatures were read upon the Reichsanstalt thermometer already 

 described ; corrections were made for the zero point in melting ice, for the 



