507 



a gold theriuuiiietei' is prefemble to a pliitiniim one, as has already 

 been pointed out by Kamkumngii Onnks and Ci,ay '). 



At hydrogen temperatures both phitiuuui and gold are no longer 

 approximately linear. Here and at licliuiu temperatures manganine 

 and constantin proved to be nearly linear and fit I'or resistance 

 thermometers. Concerning ihese we refer to a future comm, dealing 

 with resistance measurements in particular lor the determination of 

 the specific heat of mercury at helium temperatures. 



§ 7. Comparison of our thcrinoincier Pti with other platiiuaa 

 reóistance therinoinctei's. Comparing- our measurements with those of 

 F. Henning ') formulae of the form: 



AA^ = J/(A'— 1) + X{Il—\y and a' 



(I'N 



J/= — (l_100c-)-l 



were used. This was done because there w^ere objections to a direct 

 determination of the temperature coefticient by measuring the resistance 

 of Pt'j at 0° C. and 100° C. which since (he first calibration had 

 never been brought to a temperature aboxe the ordinary. We found 



E = 



W 

 W 



A = 



W 



t 



- 23.96 



43.09 



6J.50 



79.57 



102.72 



113.58 



130.46 



182.88 



186.79 



(K.O. and H. 

 0.90523 

 0.82893 

 0.75511 

 0.68233 

 0.58822 

 0.54359 

 0.47389 

 0.25234 

 0.23554 



These numbers give : J7 = — 0.0078758 



jS/ = — 0.0007605. 

 And further c = — 0.30.10-^ 



100«' = 0.38821 

 From the results it a|)peais that our platinum thernmmeter, as 

 regards its constants, lies between the platinum thermometers ^'". 1 

 and N". 7 used by Hennino in his investigation. This was to be 

 expected, as these thermometers, like oui's, were obtained from 

 Heraeus, N". 1 and Ft/ being of earlier date. The dilfercnce with 

 the values calculated by Henning is caused by the fact thai his 

 calculation was based on our calibration of 1906, which di fiers from 

 our present one and that of 1907 (Comp. § 5). 



1) Gomm. N". 95. Uöed also by Gkommelin, Comni. N". iiOa. 



2) Ann. der Phys. 4ie-Folge Bd. 40, 1913. 



