506 



At 



-:wtJ :m '■/ i^s iij ic>-< !ƒ jj 2/ i 



Fig. 1. 

 The di/Ferences between tlie calil)rations of 1913 and 1907 are 

 less than Vso^*^ of a degree throughout. The fact that tlie differences 

 with the first calibration (1906) are more considerable must un- 

 doubtedly be attributed to the mechanical treatment of the wire: 

 after the first calibration the wire broke, and had lo be re-wound. 

 It must be ascribed to chance, that the deviations are so small just 

 at the points of the second calibration. 



§ 6. The field of utlUty of the pbitinuiii reslskuice thertnonicter 

 at low temperatures. Resistance thermometers for other fields of tem- 

 peratures. The curve in tig. 1 shows at once the peculiar behaviour 

 of platinum below — 200°. At this temperature a change of direction 



in Ihe line which gives the resistance 

 as a function of the temperature is 

 sharply marked. In fig. 2 the deviations 

 from the formula given above in the 

 oxygen field are once more represented 

 (circles) and also those for the thermo- 

 meters Pti (squares) and Ptr, (triangles), 

 which were also directly compared with 

 the hydrogen-thermometer by Dr. G. 

 DousMAN and us. It is clear from the 

 curves' that we have to deal with a 

 specific peculiarity of platinum, which 

 makes it very unsuital)le to be used 

 as a thermometer in this field, as accurate interpolations are im- 

 possible. For this reason in the field of temperatures below — 200°C. 



•»wt 



Fig. 2. 



