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XXXVI. An Improved Calorimeter for the Application of the 

 Method of Mixtures. By F. A. Waterman*. 



THE determination of the specific heat of solids by the 

 Method of Mixtures, as employed by Regnault, is 

 especially subject to error arising from the determination of 

 the radiation correction. For the purpose of avoiding this 

 source of error, Mr. M. N. Hesehus f has suggested that the 

 calorimeter-cup be introduced into, the bulb of an air-ther- 

 mometer and maintained at a constant temperature by the 

 introduction of a sufficient amount of cold water, of known 

 temperature, immediately after the introduction of the heated 

 solid. By this means both the radiation-correction and the 

 " water equivalent " of the calorimeter-cup are avoided. 



The heat received by the cold water being equal to that 

 given out by the heated body, the following simple equations 

 may be used : — 



MS(T-0)=ro*(0-*), 

 in which 



M=mass of substance, the specific heat of which is to be 

 determined. 



m=mass of cold water introduced into the calorimeter- 

 cup. 



T = temperature of the heated body. 



— initial temperature of the calorimeter-cup. 

 t = temperature of cold water introduced into calorimeter- 

 cup. 



5= mean specific heat of water at the temperature used. 



S = specific heat sought. 



From this equation we have 



~__ ms(d — t) 

 M(T-0)' 

 the working equation used. 



The results obtained by this method, as submitted by 

 Mr. Hesehus, do not appear to be as accurate, however, as 

 those obtained by the Method of Mixtures as practised by 

 Regnault. The ten determinations given of the specific heat 

 of brass varied from *0821 to °0969, or, omitting the result 

 '0821, which was apparently erroneous, nine determinations 



* Communicated by the Author. 



t Journal de la Societe Physico-chemique Russe, Nov. 1887 ; Journal 

 de Physique, torn. vii. p. 489, 1888. 



Phil. Mag. S. 5. Vol. 40. No. 246. JS'ov. 1895. 2 G 



