358 



DE. J. A. HAEKER ON THE HIGH-TEMPERATURE STANDAEDS 



master standard, and was compared with No. 2 in a specially arranged electric furnace 

 at temperatures up to 1200 C. before and after the investigation. 



The results of these comparisons show conclusively that Junction No. 2 has not 

 suffered any material alteration during its protracted heatings at high temperatures.* 



The E.M.F. of the two junctions, as given by a comparison made at the close of the 

 work, is shown in the following table : 





XIV. Formula for Thermojunctions. 



From the values of the E.M.F. of N.P.L. 1 and 2, as determined above by 

 HOLBORN, a formula involving two powers of the temperature was calculated by least 

 squares to give the relation between E.M.F. and temperature to represent the 

 Reichsanstalt's scale. 



The formula 



E, = 304 + 8'1 G5 t + 0-001663 t 2 



gives residuals at the four melting-points given above much smaller than their 

 probable error. 



The corresponding formula for HOLBORN and DAY'S own standard junction T 2 , 

 using only the values of the temperature obtained from the gas thermometer with 

 bulb of platinum-indium and employing the revised data for the expansion of this 

 material at high temperatures,! is 



E, = 310 + 8-048 t + 0-00172 t-. 



The following table gives side by side the E.M.F. of HOLBORN and DAY'S 

 junction T 2 , and of our own junctions at temperatures above 300 : 



* At the conclusion of the second set of comparisons the metallic lustre of some inches of the platinum 

 wire was decidedly impaired, due probably to the natural disintegration of the material, but this did not 

 appear to be accompanied by the smallest change in the E.M.F. of the junction. 



t HOLBORN and DAY, ' WIED. Annalen,' 1900, vol. 2, p. 520. The change from the original formula 

 for the expansion of the bulb involves a correction of the scale amounting to 4 at 1000. 



