THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



AUGUST. 



XII. On the Specific Heats of Gases. 

 By Eilhard Wiedemann*. 

 [Plate I.] 



SINGE the publication of Regnault's work on the specific 

 heats of gases this subject has not, so far as I am aware, 

 been experimentally dealt with. The apparatus required to 

 carry out such investigations as those of Regnault is not 

 usually at the command of many physicists. 



I have sought to discover methods which would enable the 

 experimenter to prosecute with exactness, yet with less com- 

 plicated appliances, this inquiry, which has such important 

 bearings upon the mechanical theory of heat and also upon 

 molecular chemistry. 



In the following first communication the methods of obser- 

 vation will be described, measurements of the specific heat of 

 air will then be given, and, lastly, the relation between specific 

 heat and temperature in the case of a few gases will be in- 

 vestigated f. 



In performing his measurements Regnault used an appa- 

 ratus which consisted essentially of three parts — the vessel for 

 storing the gas (gasometer), the heating-apparatus, and the 

 calorimeter. Regnault's gasometer was of copper foil 5 millims.. 

 in thickness, and had a capacity of about 30 litres ; the gas 

 to be examined was compressed in it by means of a force- 

 pump. Pressures varying from 3000 to 4000 millims. of 



* From Pogg. Ann. der Physik und Chemie, vol. clvii.pp. 1-42. Trans- 

 lated by M. M. Pattison Muir, The Owens College, Manchester. 



t It need hardly be mentioned that Regnault has himself fully dis- 

 cussed the sources of error which may arise in his own methods of obser- 

 vation. 



Phlh Maq\ S.5.Yol. 2. No. 0. Ana. 187(3. G 



