THERMO-ELECTRIC QUALITY UNDER PRESSURE. 



361 



at atmospheric pressure is strikingly convex toward the temperature 

 axis, as was that of the other specimen. The two specimens are 

 probably of equal purity. 



The thermal electric behavior at atmospheric pressure against 

 lead is given by the formulas: 



E = (-74.42/+ 0.0160 f") X 10-« volts, 

 P = (-74.42 + 0.0320 n (t + 273) X W volts, 

 ■ a = 0.0320(/ + 273) X 10-« volts/°C. 



10'^ 20° 



SO'' 40° 50° 



Temperahire 

 Bismuth 



60° 70° 80° 



Figure 40. Bismuth. 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 temperature 

 plotted as abscissae. 



The pressure measurements of e.m.f. were satisfactory. The run 

 at 25° was made without previous seasoning, in the desire to obtain 

 all possible information before the confidently expected rupture, but 

 this fear proved groundless, and the series of runs was completed 

 without incident. Furthermore, it proved that seasoning was not 

 necessary, the zero correction at 2.5° after the first application of 12000 

 kg. being only 0.16% of the maximum effect. Readings could be 



