532 Day and Sosman — Nitrogen Thermometer Scale 



8. Summary. 



The new gas thermometer temperatures which this investi- 

 gation has given us are brought together in Table VI, ex- 

 pressed (column 2) in terms of nitrogen expanding at con- 

 Concerning the sulphur used with the air thermometer, the following 

 information is offered (p. 140) : 



" The sulphur used on the Friday was poured out of the apparatus before 

 it solidified. It was found to be much discoloured, owing to the presence of 

 various impurities due to residues of oil, red lead, etc., used in fitting the 

 iron tubes together. Fresh sulphur was used on the Saturday, and this, on 

 examination, appeared to have suffered hardly any change." 



Notwithstanding the fact that the conditions surrounding the observations 

 of Saturday appear the more favorable, these are rejected, with this state- 

 ment (p. 140) : ■ . 



" The mean values of t deduced from the observations with the platinum 

 thermometers Mj and M 2 , by assuming the value d= 1*570 in formula (d), are: 

 On Friday, t = 444 '78° C. 

 On Saturday, t - 444-84° C. 



"The mean values of t deduced from the simultaneous observations with 

 the ail thermometer are : 



On Friday, * = 444 "80° C. 

 On Saturday, t = 444*52° C. 



"The value found on Friday is seen to agree perfectly with that de- 

 duced from the observations with the platinum thermometers. The value 

 of t deduced from Saturday's observations is 0*32° too low ; but it is prob- 

 able that the value of mk, used in reducing the observations taken on that 

 day, is a little too great." 



"...'. We may, therefore, conclude that these experiments, so 

 far as they go, are a complete verification of the value of 6 found in 1887, 

 and show that the platinum wire has not altered appreciably in the 

 interval." ^ 



Of the apparatus used, the following details are taken from another part 

 of the paper (p. 120) : 



*' Two new thermometers, M x and M 2 , were therefore constructed out of 

 the remainder of the old spiral [1887], and were very carefully compared 

 with the air thermometer at a temperature very near the boiling-point of 

 sulphur. . . . The result agrees perfectly with that found in 1887, and 

 shows that the value of the ^-coefficient has not altered appreciably in the 

 interval. 



■• The apparatus used for this comparison [the sulphur bath used with the 

 air thermometer], although useful as a constant high-temperature bath, was 

 not very well suited for determining the actual temperature of the sulphur 

 vapour. Another series of experiments was therefore undertaken in a Meyer 

 tube, which proved to be more convenient for the purpose." 



On page 145 occurs the following statement of the final result (obtained in 

 the Meyer tube with resistance thermometers only) : 



•■ Assuming 6= 1*570 for thermometers L, Mi and M 2 , we find for the 

 corresponding air-temperature the value 



t = 444*53° C. 



We believe this to be within 0*1° of the true temperature of the vapour of 

 sulphur boiling freely under a pressure of 760 mm ." 



The value assumed for 6 is entirely dependent upon the temperature 

 determined with the air thermometer, and can not be more accurate than 

 this determination. From the air thermometer measurements above quoted, 

 0*5° would appear to be a fairer measure of the uncertainty of the final sul- 

 phur point. 



