Dr. H. F. Weber 07i the Specific Heat of Carbon, 255 



The apparatus emplo3^ed for the investigation was the ice ca- 

 lorimeter invented by Professor Bunsen. In order to be sure 

 that I had a pure substance, and to exclude all condensation of 

 gas and heat of moistening, I first subjected the diamond to a 

 thorough examination. Geh.-Hath G. Rose was so good as to 

 le.nd me the two largest and purest diamonds (weighing respec- 

 tively 44 ^^ and 634 milligrammes) in the mineral collection here. 

 In a preliminary trial the two diamonds were investigated sepa- 

 rately as to their mean specific heat betv/een 0° and 100°. Three 

 experiments gave, for the larger, 



0-1431 

 0-1439 

 0-1432 



Mean . . 0-1434; 



and for the smaller, 



0-1436 

 0-1439 

 0-1441 



Mean . . 0-1439 



The Httle difi'erence in these two mean values permitted me, 

 in the subsequent investigations, to employ the two diamonds 

 together, so that I could operate with a mass of 1081 milli- 

 grammes. The diamonds were heated to t°, cooled in the ice 

 calorimeter to 0° ; and from the amount of heat Q given out in 

 the calorimeter, the weight G of the substance, and the tempe- 

 rature-interval t—0=t the mean specific heat Co^t between 

 0° and t° was calculated, according to the equation 



Q=G.^.Co_^ 



For 12 difi'erent temperatures, which weve almost symmetri- 

 cally distributed in the interval 0° to 200°, 33 determinations 

 were made. These gave the dependence of the mean specific 

 heat Co-t between 0° and t° upon the temperature t in the fol- 

 lowing slightly parabolic form : — 



Co_, = 0-0947 4- 0-000497^f-0-00000012/2. . . (1) 



The variability with the temperature being so great, the mean 

 specific heat has only a formal signification, very rarely capable 

 of evaluation. In such a case, from the mean the real specific 

 heat for the temperature t must be derived — i. e. that quantity 

 of heat which the unit of weight at t° requires in order to raise 



