46 ELECTROCHEMICAL INVESTIGATION OF LIQUID AMALGAMS 



be calculated separately. When thus treated the final results from tht 

 two are essentially identical, and may be averaged together. As the 

 details may be worked out from the data, by anyone wishing to verify the 

 results, further space need not be wasted by their minute presentation. 



It is enough to present the final table of values for the function * 



Cup 1-2 0.00397 



i-3 0.003855 



1-4 0.003794 



Cup 2-3 0.00375 



2-4 0.003715 



3-4 0.003685 



Thus it is clear that in the case of zinc amalgams, as in all other cases 

 thus far studied, the temperature coefficient of the electromotive cell 

 becomes nearer and nearer the limiting value as the dilution proceeds. 

 In the most dilute cell measured, whose two amalgams contained respec- 

 tively about o.io and 0.03 per cent of zinc, the value of the temperature 

 coefficient had come within 0.7 per cent of the requirement of the gas law. 

 The significance of these results as regards the theory of the galvanic 

 cell will be discussed in a later section, after the facts concerning other 

 cells have been presented. 



It will be observed that the first value given for the temperature coeffi- 

 cient exceeds the ideal value by as much as 8.5 per cent. This high value 

 for the temperature coefficient, which appears wherever the most con- 

 centrated amalgam was concerned, might possibly be due to the crystal- 

 lization of zinc at o. That this, however, was not the case seems almost 

 certain from the regularity of the results obtained, and from the fact that 

 the temperature coefficient between 15 and o, and between 30 and o 

 for even a stronger amalgam than was here used, were nearly the same. 



The point was, however, also experimentally investigated in the fol- 

 lowing manner. Both the limbs of an H tube were filled with a 0.91 per 

 cent zinc amalgam, and the potential between them at o was measured 

 and found to be almost zero. Then a small quantity of pasty zinc amalgam 

 was added to one limb, and a large and permanent potential was produced 

 in the direction indicated by theory. In another similar cell, one of the 

 limbs was very slightly diluted with mercury and again a permanent poten- 

 tial, in the direction foretold by theory, was observed. These facts could 

 not be explained if the parent amalgam had crystallized out at o, but are 

 precisely what would be expected from an unsaturated amalgam. 



Control experiments were made in which an amalgam known to be more 

 than saturated replaced the 0.91 per cent amalgam in the above experi- 

 ments. On the dilution and on the concentration of one of the sides of 

 the cell no permanent potential greater than o.ooooi volt was obtained, 

 showing in this case that the presence of the solid phase caused the effec- 

 tive concentration of the amalgam to become constant. 



