58 ELECTROCHEMICAL INVESTIGATION OF LIQUID AMALGAMS 



and the two members were calculated separately and compared. Thus 

 all the errors, both of theory and observation, were heaped upon the 



smallest term involved f-^r] and naturally formed a much larger per- 



\vr I 



centage of this smallest term than they would when applied, as in the 



RT c 



present paper, to the much larger term ^- /# - L . Cady's equation thus 



V 1 C% 



failed as applied to the calculation by difference of the smallest term ; but 

 the present method of presentation shows that the equation may be of 

 use in calculating approximately the temperature coefficient of an amalgam 

 cell. 



As the amalgams become more dilute, the fulfilment of the equation of 

 course becomes more exact, because the concentration ratio gives more 

 and more nearly an exact measure of the osmotic work, and all the other 

 irregularities probably decrease. Thus for the cell M3-M4 (or N3-N/).), 

 (pages 45 and 46), where 7^ = 0.01395 volt, ATT for 29. 96 =0.001541 volt, 

 and the ratio of the concentrations is 3.305: I, the following results are 

 calculated : 



Temperature coefficient calculated from concentrations.. 0.0000515 

 Actually observed temperature coefficient ............... 0.0000514 



The difference is only 0.2 per cent, an amount distinctly less than the 

 experimental error. 



Similar calculations for lead give similar results ; for example, let us 

 take the cell Pi-P2, having a concentration ratio equal to 2.53. Then 



8.316 0.9282 



2X96,530 



= 0.0000392 



Difference = 0.0000008 



In the more dilute cell Qi-Q2 where the concentration ratio = 6.21, we 

 have 



Temperature coefficient calculated from concentrations = 0.0000786 

 Temperature coefficient actually observed ............. =0.0000793 



With this more dilute amalgam the difference is less than I per cent 

 instead of being 2 per cent as in the case of the more concentrated lead 

 cell. 



Turning back, now, to cadmium, investigated by Richards and Forbes, 

 we find that the results recorded there give somewhat similar indications, 

 when compared according to the present method. Thus the cell 1-5 <s 

 (made from an amalgam containing 2.955 P er cen t f cadmium and 

 another amalgam obtained by diluting 12.226 grams of this amalgam with 



48 Carnegie Institution of Washington Publication No. 56, 46 (1906). 



