176 DICKINSON AND MUELLER: RESISTANCE THERMOMETER SCALE 



TABLE V 



Comparative Table. Thermodynamic Scale 



POINT 



Benzophenone 



Cadmium 



Zinc 



Sulfur 



Antimony 



PHYSICS. -^-Comparison of the resistance thermometer scale with 

 the nitrogen scale from 300° to 630°. H. C. Dickinson and E. 

 F. Mueller, Bureau of Standards. 



The temperature scale which at presents serves as the basis 

 for the work of the Bureau of Standards in the interval 100° to 

 600°C. is the scale of the platinum resistance thermometer as 

 defined by the work of Waidner and Burgess : Platinum resistance 

 thermometry at high temperatures. 1 The resistance thermometer 

 scale was established by assigning to the temperature of the sul- 

 fur boiling point the value 444? 70 at normal pressure, as the 

 best value available at the time. On this resistance thermometer 

 scale the following temperatures, among others, were found: 



Boiling point of benzophenone 306?02 



Boiling point of sulfur (by definition) 444?70 



Freezing point of antimony 630T71 



A direct comparison of the temperatures cale as defined above, 

 and the temperature scale of the nitrogen gas thermometer pre- 

 viously described by Day and Sosman, was suggested, and as such 

 a comparison seemed very desirable we undertook the resistance 

 thermometer measurements. Two thermometers were used, one 

 "D" of the ordinary Callendar type which had been in use in the 

 laboratory, and the other "R" constructed especially for this 

 work. The latter was made with the lower part bent into the 



1 Bull. Bureau Standards, 6: 149-230. 1910. Reprint No. 124. 7:3-11. 1910. 

 Reprint No. 143. 



