Physics. — " On the nieasureinent of very low temperatures. 

 XXVIII. Comparison of the platinum, and the gold resistance 

 thermometers with the heli lunthermom eter" . By P. G. Cath, H. 

 Kamerlingh Onnes and J. M. Burgers. Comimiiiicatioii N". 152c' 

 from the Physical Laboiatory at Leiden. 



(Communicated in the meeting of Sept. i29, 1917). 



§ 1. Introduction. 



The measurements of the galvanic resistance of gold and platinum 

 communicated in Oomm. Nl^ 99rï, 996, 141 a extend over all the 

 temperature-ranges which could be covered by means of crjostats 

 filled with liquefied gases. The temperatures from 55° K. to 27° K. 

 as falling outside those ranges could not be investigated. Still it is 

 exactly in this region that the temperature change of the galvanic 

 resistance of some pure metals shows peculiarities which render a 

 further investigation very desirable. Even from the early investigations 

 by H. Kamerlingh Onnes and J. Clay ^) it appeared that the strong 

 change of the galvanic resistance which shows itself at hydrogen- 

 temperatures must have its beginning in the range in question. 

 Nernst '') has noticed that the difference between two platinum- 

 thermometers expressed in their resistance at 0° C. can be approxi- 

 mately represented by a linear function of either of the resistances. ') 



1) H. Kamerlingh Onnes and J. Clay, Leiden Comm. N". 1 07c, p. 25. 



») W. Nernst, Sitz. Ber. Berl. Akad. 1911, p. 314. 



') This follows immediately from Matthiesen's rule. The applicability of this rule 



in the region of low temperatures was shown by Fleming down to — 190^ C. As 



regards its extension to still lower temperatures, Kamerlingh Onnes and Clay found 



that, although at the temperatures to be reached with liquid hydrogen the additive 



resistance is no longer exactly equal to that at less low temperatures, still the 



formula r^j'^r^-^px by which they represent the difference between the 



resistance r^y of a wire of the pure or ideal material at T and the resistance r^j 



of a wire of the same dimensions of a material containing an admixture .c (p large 



and constant I, in a first approximation gives a representation of the influence 



which small impurities have on the change of resistance with temperature (Leiden 



Gomm. N". 99c, p. 20, July 1907). Putting r^^f/r^.^ = u- and comparing two 



wires I and II, we get «fjj — ?{'] — A' (1 — m;|), that is Nernst's formula with 



, Pn^n — Pl^I 



A = . Gomp. note on page 1169 further on. 



1 —PlXi 



