530 



Prof. H. L. Callendar on a 



on measurement of the total heat of a mass of platinum by 

 means of a calorimeter. (3) The Thermoelectric Method, 

 based on measurements of the thermo-E.M.F. of a couple of 

 platinum and some other platinum metal or alloy. (4) The 

 Resistance Method, based on measurements of the electrical 

 resistance of platinum. 



Table II.— 



Fusing-Points 



by " Platinum " Methods 



• 



Method. 



Observers. 



Silver. 



Gold. 



Copper. 



Palla- 

 dium. 



Pla- 

 tinum. 





C. & E 



960 



1061 



1081 







1530 



1780 





Violle(1879) 



954 



1045 



1054 



1500 



1775 



(5) Thermoelectric ... 



Becquerel(1863) .. 



960 



1092 



1224 







ii 



Barus(1892) 



985 



1093 



1097 



1643 



1855 



ii 



„ (1894) 



986 



1091 



1096 



1585 



1757 



,, 



Holborn & Wien .. 



968 



1072 



1082 



1587 



1780 





Heycock & Neville 



961 



1061 



1082 









C. &E 



961 



1061 





1550 



1820 







Method (1) is of comparatively limited application owing 

 to the smallness of the expansion and to the difficulty of pro- 

 tecting the expanding wire from strain. As applied in Joly's 

 Meldometer, the method is extremely convenient for the 

 determination of the melting-points of small fragments of 

 minerals, but it would not be suitable for a practical standard 

 and has never been proposed for this purpose. 



The Calorimetric Method (2) is suited for the determination 

 of isolated points, but is incapable of continuous reading or 

 recording. It is also very laborious and wanting in sensi- 

 tiveness. The degree of accuracy attainable, though 

 sufficient for practical purposes in some cases at high tem- 

 peratures, is far too small for the purposes of a standard at 

 the lower points of the scale. 



The Electrical Methods (3) and (4), though mysterious to 

 the uninitiated, are far the most convenient and accurate in 

 practice. The sensitive portion of the electrical thermometer 

 is small and delicate, and can be placed at any distance from the 



* The values found by the expansion method were reduced to the scale 

 of the gas-thermometer on the assumption of 1061° for the Au F.P., and 

 of a linear formula for the coefficient of expansion. The results for 

 palladium and platinum by this method are probably too low owing to 

 sagging of the wire. 



