RATIO OF SPECIFIC HEATS. 



25 



Temperature. 



15.60° c. 



15.60 



15.60 



liolonietcr. 



above 



V. — Kesults. 



Equation (1) uhicb is made the l);isis of the pi'o^sent experiments applies for 

 perfect gases, the intrinsic equation of wliich is of the foi'm due to Mariotte and 

 Gray Lussac : 



pv = RT, 



where ^ is the pressure coi-i-esponding to the volume v at the absolute temperature 

 T, and li is a constant. For aii-, oxygen, and hydrogen this equation is admissible, 

 provided the zero point of tlie absolute scale of teni|)era.ture be located in conform- 

 ity with the properties of the gases. This is done if the absolute temperature ^ is 

 computed from the temperature t in degrees centigrade by the formula 



in which a is the coefficient of expansion of the gas in question. We may remai'k 

 that the effect of this difference of a for the different gases in question is usually of 

 little sisfuificance. 



We made the computation in the same way foi- cai'bou-dioxide, although the 

 departure from the laws appertaining to perfect gases is appreciable for this body, or 

 at least is larger than for the other gases. Tlie values for a and ^ used in the pres- 

 ent paper ' are as follows : 



a. AiE. 



The air was taken directly from the atmosphere in the room and successively 



passed through concentrated sul[)huric acid, a drying tube containing calcic chloride 



' The values for tt communicated at the O.xford meeting of the British Association were found 

 for i/a — 273. Hence these results will differ slightly from the present series. 



