518 Day and Sosman — Nitrogen Thermometer Scale 



of our final results (1911) was accurately summed up in one of 

 our closing paragraphs as follows : 



"The chief source of present uncertainty [in high-tempera- 

 ture gas-thermometer measurements] is the temperature dis- 

 tribution over the surface of the bulb in an air bath. It would 

 be possible to eliminate this error in the lower portion of the 

 scale by substituting a liquid bath which could be stirred. 

 In fact, this was done for temperatures below 500° in the 

 earlier work of Holborn and I)ay, but has not, so far, been 

 tried in the present investigation because of the relatively 

 secondary importance of the lower temperatures to the ultimate 

 purpose of the investigation (the study of silicates). For the 

 higher temperatures, no -satisfactory liquid bath has been 

 found."* (Publication of the* Carnegie Institution ISTo. 157, 

 p. 125, 1911.) 



The lower temperatures upon this scale, determined in an 

 air bath, come out about 1° lower than the corresponding 

 temperatures of the Reichsanstalt scale (determined in a liquid 

 bath). These temperatures are compared below : 







Holborn and 

 1900 



Day 



Day and Sosman 

 1911 



Cadmium 

 Zinc 



(melting point) 



a u 



321-7° 



419-0 





320-0° 

 418-2 



Antimony 



T " " 



_._. 630-6 





629-2 



This circumstance was the more conspicuous, and perhaps 

 the more open to suspicion, because a discrepancy of precisely 

 the same order of magnitude (1°) had appeared between air- 

 bath and liquid-bath determinations in the neighborhood of 

 400° in the work of Holborn and Day in 1900, which even- 

 tually led them to reject the measurements made at that 

 temperature in the air bath. It is, therefore, not surprising 

 that the reappearance of this discrepancy should attract con- 

 siderable attention even though this difference of 1° is within 

 the stated and admitted limits of accuracy of the Reichsanstalt 

 scale (2° to 3°). It is also serving a useful purpose in directing 

 attention to an uncertain t} 7 which had remained undisturbed 

 for so long that it probably had been forgotten, for there is 

 abundant reason to believe that to-day, with a modern gas 

 thermometer, adjusted to give appropriate sensitiveness, these 

 temperatures can be determined with much greater accuracy 

 than 1°. 



That the Reichsanstalt is also of this opinion is shown by the 

 recent publication of a new series of measurementsf of these 



* Prof. Holborn has directed attention to the same limitations in our 

 results at these temperatures, in a recent paper, to which further reference 

 will be made presently. 



f Holborn and Henning, Ann. Physik (4), xxxv, 761-774, 1911. 



