544 Adams and Johnston — Standard Scale of Temperatures. 



Table V. — Comparison of the " Corrected" Temperatures (measured by the 

 Kesistance Thermometer) with Determinations by the Gas Thermometer 

 and with Thermoelements. Thermodynamic Scale. 









" Corrected" 









Temp, based on 



. temps, from re- 









gas thermometer 



sistance ther- 



Differences 







measurements 



mometer meas- 







(D. & S.) 



urements 

 (W. &B.) 









I 1 



II 



II — I 



Nph. 



b.p. 



217-95 2 



217-97 



+ 0-02 



Sn 



f.p. 



231-73' 



231-88 



•15 



Bnz 



b.p. 



305-90 4 



305-91 



♦01 



Cd 



f.p. 



320-92 3 



320-92 



•oo 



Pb 



f.p. 



32Y-39 3 



327-35 



— -04 



Zn 



f.p. 



419'4 4 



419-24 



— -16 



S 



b.p. 



444-55 5 



444-55 



•00 



Sb 



f.p. 



630'0 4 



630-36 



+ 36 



Ag 



f.p. 



960-4 4 



960-7 



+ 3 



Cu 



f. P . 



1083-2 4 



1082-8 



— -4 



1 The temperatures are given to hundredths for purposes of comparison. 

 2 Holborn and Henning, Ann. Physik, xxxv, 761-74. 1911. 



3 From the thermoelectric measurements of Table IV above. 



4 Temperatures transferred from gas thermometer measurement to fixed 

 point by thermocouples. 



5 Direct gas thermometer determination. 



peratures below 0° C. Indeed Travers and Gwyer say : " A 

 standard scale of temperature, based on Callendar's three fixed 

 points, using standard wire, and taking 1*5 for the value of 8, 

 would obviously lead to absurd results at low temperatures ; and 

 the converse may be said of our own observations,"* and con- 

 clude that the Callendar formula cannot be made use of except 

 for interpolation. There is thus ground for believing that the 

 accuracy of the results calculated from the change of resistance 

 of pure platinum by means of the simple Callendar formula 

 is, to some extent, fortuitous. The small variation of 8 intro- 

 duces uncertainties which would appear to be too great for the 

 most accurate work, except over the temperature range included 

 between the fixed calibration points (0°— 444*55°), and a short 

 region beyond (perhaps to 750°). f On the other hand, it must 

 be admitted, that the cubic term (which expresses the varia- 

 tion of 8 with the temperature) is very small — so small that its 

 effect is scarcely greater than the uncertainty in the gas ther- 

 mometer determinations at higher temperatures. 



* Proc. Eoy. Soc. London, lxxiv, 1904-5. 



f The effect of slight changes of 6 on the calculated temperatures may be 

 gauged from the following : that a change of 0-2° in the boiling point of sul- 

 phur changes 6 by 1 per cent (and proportionally for oth°r small changes) ; 

 this in turn affects temperatures of 300°, or lower, by - l° or less, but affects 

 the antimony point by 0'5°, and the copper point by 1*6°. 



