ELECTROCHEMICAL INVESTIGATION OF LIQUID AMALGAMS 71 



SUMMARY. 



The results obtained in the foregoing papers may be summarized as 

 follows : 



(1) The electromotive forces of various cells, containing amalgams of 

 thallium, indium, tin, zinc, lead, copper, and lithium, have been measured 

 at o and 30, with many precautions against experimental errors. 



(2) The temperature coefficients of cells containing zinc amalgams 

 were also obtained by actually opposing cells at o against cells at 30. 



(3) It is shown that in every case the more concentrated amalgams 

 deviate by appreciable amounts from the theoretical values calculated 

 from the simple concentration law, thallium and indium resembling cad- 

 mium in giving potentials higher than those demanded by the concentra- 

 tion law ; whereas lead and tin resemble zinc in giving potentials lower 

 than those demanded by the concentration law. Thallium showed the 

 greatest positive deviation, and tin and lead the greatest negative deviation. 



(4) It is shown further that on the average about three quarters of 

 each of these deviations are to be explained by the heat of dilution of the 

 amalgam, according to the equation of Cady. 



(5) The other quarter of the deviation, not explained by the equation 

 of Cady, must be ascribed either to experimental error or more probably 

 to the inexactness of the concentration law. Such inexactness would be 

 caused either by polymerization or by the formation of hydrargyrates, 

 according as the computed potential is greater or less respectively than 

 the observed potential. 



(6) It is shown that the equation of Cady requires that the temperature 

 coefficient of a cell of this type should be equal to the total concentration 

 effect divided by the absolute temperature, and should be independent of 

 the temperature. The verification of these conclusions is shown to hold 

 approximately in all the cases studied, by comparison with the actual 

 values. This fact affords a simple method of computing with moderate 

 accuracy the temperature coefficient of the electromotive force of cell of 

 this type, without having recourse to electrical measurement. 



(7) It is shown that the equation of Cady is not well adapted for com- 

 puting the heat of dilution, for in this case all the errors and deviations 

 accumulate upon the smallest term of the equation. 



(8) The heats of dilution of these various amalgams are computed 

 with the help of the equation of Helmholtz ; and it is shown, as was to be 

 expected, that the heat of dilution decreases very rapidly as the dilution 

 progresses. 



(9) The difficulties of actual thermochemical measurement of the heat 

 of dilution of amalgams are emphasized. 



