6 ELECTROCHEMICAL INVESTIGATION OF LIQUID AMALGAMS 



truth, the value F must be diminished by 0.05 per cent, and becomes 96,530 

 coulombs per gram equivalent. This latter value is used in the work 

 which follows, and all atomic weights also are referred to this standard. 



The symbol v represents the valency of the metallic ion in the electrolyte 

 of the cell. Since thallous sulphate and indium sulphate were used as 

 electrolytes in the cells of thallium and indium amalgams, it is difficult to 

 conceive how the valency of the ions of thallium and indium could be 

 other than i and 3 respectively. The valency of tin will receive especial 

 consideration when that metal is discussed; in our experiments it was 

 undoubtedly 2, not 4. 



The work of Daniel Berthelot 20 probably affords the most accurate value 

 of R, which we may express conveniently in mayers. A mayer is the heat 

 capacity which is warmed I degree centigrade by i joule. According to 

 Berthelot's work, the space occupied by a gram-molecule of a perfect gas 

 at 760 mm. pressure, 45 latitude at the sea-level, may be taken as 22.412 

 liters (the atomic weight oxygen being 16.000), and the absolute zero at 

 273.08 C. These values are probably accurate at least to within 0.05 

 per cent. The value of R on this basis will be 



R= 76.00x13.596x980.6x22,412 =g 6 s< 



273.08 xio 7 



T, by which R is multiplied in the formula, is the temperature of the cell 

 referred to the hydrogen scale. This was fixed in our experiments by 

 means of four exactly known thermometers. Over the range of tempera- 

 ture employed in the following measurements these readings are closely 

 comparable with the corresponding thermodynamic temperatures. More- 

 over, the experimental determination of the temperature to within 0.01 



T" 



would fix the value of -f- 1 within one part in 30,000, a degree of accuracy 



Jo 



far greater than can be attained with the rest of the data used in calculat- 

 ing the electromotive forces. 



It appears, then, that the values of v, R, T, and F are known with 

 considerable accuracy, and it now remains to consider the concentration 



ratio -L. An error of o.i per cent in this ratio would cause an error of 



Ct 



o.ooooi volt in the electromotive force, and it is clear that the early investi- 

 gators have not determined this ratio with sufficient accuracy. If a weight 

 w of amalgam of concentration c^ is mixed with a weight nw of mercury 

 to form a new amalgam of concentration c z , it is not permissible in accurate 

 work to write 



""Tray. et Mem. du Bureau internat. des poids et mesures, 13, 113 (1903). 



