M.-E. Wiedemann on the Sjjccijic Heats of Gases. 89 



then, as the specific gravity of air at 0° and 760 millims. re- 

 ferred to water is _- , the weight of volume v of the oas 

 7<3*3' & h 



is 



v cr .\1 __ p + B 273*3.(7 v 

 U = 77M~T6T , (^7MT^)' TTM 



Lastly, if W represents the weight in kilos of water which 

 entered the balloon during the experiment, and if the litre be 

 taken as unit of volume, then 



p + B 273-3 . a W 

 U ~ 760 '(273'3 + #)* 773-3' 



In order to calculate the specific heat, we require also the 

 weight of liquid in the calorimeter, as also the water- value of 

 the calorimeter. The weight of liquid was determined by 

 direct weighing before every experiment : it varied from 59 

 to 61 grms. The water-value of the calorimeter was calcu- 

 lated. The specific heat of the silver used for making the 

 vessel was 0*0607 ; its weight amounted to 80*122 grms. ; the 

 water-value was therefore 5*07. The water-value of that part 

 of the thermometer which was situated in the calorimeter, and 

 which was measured, amounted to 0*3944. The total water- 

 value of the calorimeter was therefore 5*4644. A small error 

 in the estimation of the water-value of the thermometer would 

 not greatly influence the final result, because of the smallness 

 of the total figure. 



The rise of temperature observed by means of the thermome- 

 ter in the calorimeter must not be attributed solely to the heat 

 given up by the gas, and cannot be directly used for calcula- 

 ting the specific heat of the gas ; but a correction must be 

 applied, partly because of heat conducted through the German- 

 silver tube from the heating-vessel, and partly because of heat 

 radiated to or from the calorimeter. 



By passing air at the same velocity as was done with the 

 various gases through the calorimeter (surrounded with water 

 at the temperature of the air), it was proved that no appre- 

 ciable amount of heat is generated by friction of the particles 

 of gas against the silver gauze in the calorimeter. 



We assume that the amount of heat gained by the calori- 

 meter by conduction is constant for each unit of time during 

 the whole experiment*; and we designate the rise of tem- 

 perature per minute caused by this heating of the calorimeter 

 by ft. 



* R^gnault, Relation des experiences pour determiner les his et les don- 

 nfids physiques necessairea on ccUcul des Machincs-a-fcn, p. 79 ct scq. 



