TABLES 2O5-2O7. 



TABLE 205. Platinum Resistance Thermometers. 



Callendar has shown that if we define the platinum temperature, pt, by pt = ioo<{ (R R ) 

 /(Rioo Ro) } , where R is the observed resistance at t C., R that at O, R 100 at 100, then the re- 

 lation between the platinum temperature and the temperature t on the scale of the gas thermo- 

 meter is represented by t pt = S-{ t/ 100 i }-t/ioo where 8 is a constant for any given sample 

 of platinum and about 1.50 for pure platinum (impure platinum having higher values). This holds 

 good between 23 and 450 when 5 has been determined by the boiling point of sulphur (445.) 



See Waidner and Burgess, Bui. Bureau Standards, 6, p. 149, 1909. Also Bureau reprints 124, 

 143 and 149. 



TABLE 206. Thermodynamic Temperature of the Ice Point, and Seduction to 

 Thermodynamic Scale. 



Mean = 273.13 C. (ice point). 



For a discussion of the various values and for the corrections of the various gas thermometers to 

 the thermodynamic scale see Buckingham, Bull. Bureau Standards, 3, p. 237, 1907. 

 Scale Corrections for Gas Thermometers. 



See also Appendix, p. 438. 



TABLE 207. Standard Points for the Calibration of Thermometers. 



* Thermoelectric extrapolation, t Optical extrapolation, 

 m^v anH Vi<iman Journal de Physique, 1912. Mesure des temperatures elevees.) A few additional points 

 are?H.boa S ^-T S2 6; ^boils-ffioiCO,, sublimes- 78.5; Hg. freezes -38.87; Alumina melts 2000; 

 Tungsten melts 3400. 



SMITHSONIAN TABLES. 



