318 Intelligence and Miscellaneous Articles, 



ON THE SPECIFIC HEAT AND THE HEAT OF FUSION OF PLATINUM. 

 BY J. VIOLLE. 



I. The specific liea-t of platinum was measured at 100°, 800°, 

 1000°, and 1200° upon some pure metal, for which I am indebted 

 to the kindness of M. H. Sainte-Claire Deville. 



The mean specific heat between zero and 100°, determined with 

 M. E/Ognault's classic apparatus, was found to be 0-0323. 



In order to obtain the mean specific heat between zero and 800°, 

 the porcelain reservoir of an air thermometer of M. Deville's and 

 an unglazed porcelain vessel containing the platinum mass (423-140 

 grammes) submitted to experiment were introduced into one and 

 the same horizontal mufile, which Mas heated with gas in a furnace 

 with a double easing, Perrot's system. When the temperature of 

 the entire apparatus had become quite stationary, the vessel con- 

 taining the platinum M'as taken out, the metal withdrawn and ra- 

 pidly plunged into a platinum eprouvette placed, with the orifice 

 upward, in the midst of the water of the calorimeter. Equilibrium 

 of temperature between the hot platinum and the water surround- 

 ing it was slowly established. Care had also been taken to place 

 the calorimeter within an enclosure with a constant temperature, on 

 the model of that adopted by M. Berthelot. The correction for 

 cooling was made by the method indicated by M. Eegnault and 

 carried out by M. Pfaundler. Of t^vo experiments thus conducted, 

 one gave 0-0364 at 787°, the other 0-0366 at 780°; therefore the 

 mean specific heat of platinum betw^een zero and 784° is 0-0365. 



The mean specific heat between zero and 1000° was obtained in. 

 precisely the same manner. An important change, however, was 

 introduced into a portion of the experiments. To avoid the uncer- 

 tainty which always exists respecting a correction for cooling, 

 although it is small (not exceeding 0°-3 for an excess of 11 or 12 

 degrees), in certain experiments the platinum eprouvette was 

 omitted and the hot platinum plunged directly into the water : only 

 an insignificant quantity of vapour was liberated ; and the time 

 required for attaining the stationary temperature Mas reduced from 

 fifteen or twenty minutes to a few seconds, M'hich did away with 

 any correction for cooling. The results of twelve experiments (the 

 first three by the old method, the nine others by direct immersion 

 of the platinum in the water of the calorimeter) were : — 



0-0376 at 985 



0-0376 at 1002 



0-0379 „ 1028 



0-0376 „ 1006 



0-0375 „ 991 



0-0377 „ 993 



0-0376 „ 1005 



0-0379 „ 979 



0-0377 „ 1023 



0-0379 „ 989 



0-0377 „ 1023 



0-0376 „ 979 



whence we have 0-0377 for the mean specific heat of platinum be- 

 tween zero and 1000°. 



On replaci'ng the Perrot furnace by another with a double casing, 



