106 M. E. Wiedemann on the Specific Heats of Gases. 



crease of temperature. On account of the saving of material 

 it "was possible to give a wider expansion to the research in a 

 comparatively shorter time. 



The following Table contains the numbers represented in a 

 somewhat different manner. Columns L, II., and III. con- 

 tain the true specific heats of the various gases calculated on 

 unit weight. Column IV.- gives the difference between the 

 true specific heats at 0° and at 200°, stated in percentages of 

 the specific heat at 0°. The fifth, sixth, and seventh columns 

 give the true specific heats calculated on unit volume, the spe- 

 cific heat of unit volume of air being taken as 02389 ; the 

 eighth column shows the specific gravities of the gases ; and 

 the ninth contains the proportion, estimated by Pegnault, of 

 the products of the volumes V and V x and the pressures P and 

 P 1? when P is taken as about one atmosphere and P x as about 

 two atmospheres. The deviation of the number so obtained 

 from unity (to which it is equal in the case of perfect gases) 

 may be taken as a measure of the deviation from the state of 

 perfect gas. 





Specific heats of equal weights. 



Specific heats of equal volumes. 



I. 

 0°. 



II. 

 100°. 



III. | IV. 

 200°. 



V. 



0°. 



VI. 



100°. 



VII. 

 200°. 



vni. 



Spec, 

 grav. 



IX. 

 PV 



Air 



0-2389 



3-410 



0-2426 



01952 



0-3364 



0-1983 



0-5009 



0-2169 

 0-4189 

 0-2212 

 0-5317 



0-2387 



0-5015 

 0-2442 

 0-5629 





 

 



22-28 

 49-08 

 23-15 

 12-38 



0-2389 

 0-2359 

 0-2346 

 0-2985 

 0-3254 

 0-3014 

 0-2952 



0-3316 

 0-4052 

 0-3362 

 3134 



0-3650 

 0-4851 

 0-3712 

 0-3318 



1 



0-0692 



0-967 



1-529 



0-9677 



1-5241 



0-5894 



1-00215 



1-00293 

 1-00722 



1-00651 

 1-01881 



Hydrogen . . . 

 Carbonic oxide 

 Carbonic acid. 



Ethylene 



Nitrous oxide . 

 Ammonia 



As, according to Avogadro's law, equal volumes of different 

 gases contain equal numbers of molecules, it follows that the 

 specific heats of equal volumes of gases are also expressive of 

 the molecular heats of these gases. 



The specific heats calculated from the foregoing experiments 

 for constant pressure are made up of two parts : — first, the heat 

 connected with the expansion of the gas for overcoming the 

 external pressure, which is calculated (from the coefficient of 

 expansion and equivalent of heat) to be O06902 thermal unit 

 for altering the temperature of 1 gram of air through 1° ; 

 secondly, the heat connected with the internal work of the gas, 

 which might also be calculated from the estimation of the spe- 

 cific heat at constant volumes. The present does not appear 



