THERMO-ELECTRIC QUALITY UNDER PRESSURE. 



343 



PaUadium. This was the same piece of wire whose pressure coeffi- 

 cient of resistance was measured. The silk insuhition was removed, 

 and it was used in three parallel strands; there was not enough 

 material at hand to use more than three strands. More trouble 

 from breakage was found with this substance than with any other. 

 Twice during the runs it broke, and the apparatus had to be taken 

 apart and set up again. Fortunately the breaks occurred at the end 

 of the wire, so that it was sufficient merely to resolder them. The 

 breakage was probably intimately connected with the small size of 

 the wire and the small number of strands. Much care had to be 



o 



X 



o 



> 



UJ 

 "3 



4) 



H 



Temperattire 

 Palladium 



Figure 31. Palladium. Thermal E.M.F. of a couple composed of one 

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

 kg./cm.2 indicated on the curves, the junctions being at 0°C and the tempera- 

 ture plotted as abscissae. 



taken to so manipulate the pressure as to avoid tension effects from 

 viscous drag. 



At atmospheric pressure its thermo-electric behavior against lead 

 is given by the formulas: 



E = (-5A9Qt-0m7mf) X 10-6 ^,oitg^ 



P = (-5.496 -0.0352 (t + 273) X lO'^ volts, 



a = - 0.0352 (t + 273) X lO^" volts/°C. 



The readings under pressure went smoothly, except for the two 

 breaks mentioned. The irregularities were somewhat greater than 

 normal; probably the effect of viscous drag was not entirely elimi- 



