THERMO-ELECTRIC QUALITY UNDER PRESSURE. 



347 



Heraeus platinum: 



E = (-3.092 f -0.01334 f-) X 10-« volts, 



p = (-3.092 -0.02668/) {t + 273) X lO"" volts, 



a = -0.0266S(/ + 273) X 10-« volts/°C. 



Baker's platinum : 



E = (- 1.788 f-0.0173/- + 0.000042 f'^) X lO'^ volts, 



p = (_i.7SS -0.0346 f + 0.000126/-) (/ + 273) X 10-« volts, 



a = (-0.0346 - 0.000252/) (/ + 273) X lO'^ volts/^'C. 



40° 50° 60° 70° 



Temperature 



Pure Platinum 



90° 100" 



Figure .33. Heraeus Platinum. Thermal E.M.F. of a couple composed 

 of one branch of uncompressed metal, the other compressed to the pressure 

 in kg. /cm - indicated on the curves, the junctions being at 0°C and the tempera- 

 ture plotted as abscissae. 



