102 Professor H. L. Callendar [March 10, 



Table II. — Fusing Points by "Platinum" Methods. 



The results above given for the expansion method (1) were 

 obtained by assuming the expansion to be uniform, and taking the 

 F.P. of gold as 1061°. The results of Violle by the specific heat 

 method (2) were deduced by assuming a linear formula for the 

 specific heat of platinum. The discrepancies of the various results 

 obtained by the thermo-electric method (3) are partly due to errors 

 of observation, and partly to extrapolation, i.e. to differences in the 

 formulae of reduction. The high value found by Becquerel for the 

 F.P. of copper as compared with gold and silver is probably to be 

 explained by the use of a much thicker wire in the case of copper. 

 The very accurate and consistent experiments of Heycock and 

 Neville leave little doubt that the F.P. of pure copper is at least 20° 

 above that of gold. The much smaller difference of 4° to 5°, given 

 by Barus, may possibly be explained by contamination with oxygen 

 or other impurity. In the case of silver and gold, Messrs. Holborn 

 and "Wien adopted the Becquerel method of observing the fusion of 

 fine wires. In the case of copper, they adopted the much moro 

 accurate method of observing the freezing point of a large mass of 

 metal in a crucible, which had been employed by the writer in 1892, 

 and was used by Heycock and Neville throughout their researches. 

 The Becquerel method is very liable to give results which are too 

 high. 



The determination of the higher fusing points of palladium and 

 platinum is necessarily attended with greater uncertainty because it 

 involves extrapolation, and is therefore more dependent on the 

 particular formula of reduction assumed, in addition to the experi- 

 mental difficulties of the higher temperatures. Considering all the 

 obstacles to be encountered, it would be unreasonable to expect such 

 different methods to give any closer agreement at these points. 



Whatever the origin of these discrepancies, there can be no 

 question that they greatly retard the progress of research and dis- 

 covery at high temperatures. With the object of helping to remove 

 these obstacles, the writer has recently been engaged, in conjunction 



