92 M. B, Wiedemann on the Specific Heals of Gases, 



sented as a function of tlie temperature by the equation 



where a and b are constants. 



If. however, c x is the moan specific heat between r°and 100°, 

 c 9 that between r° and '200°, then £ = 100 in one case, and in 

 the other =200, and then Q is equal to the mean specific heat 

 c multiplied by the temperature-increase ; so we have 



Q=c(*-t), 



r 1 = (100-T) = a(100-T) + K 1 00-r) 2 , 

 c 2 = (200-t) = «(200-t) + &(200-t) 2 , 

 or 



Cl = a + b(100-r), 

 c 2 =a + 6(200 -t), 

 equations from which a and b may be immediately deduced. 

 But the specific heat is the change in the quantity of heat con- 

 tained in unit weight of the body for unit of temperature, i. e. 



dQ 

 dt 

 For the true specific heat at temperature t it follows that 



C = a + 2b(t-r); 

 from which we can directly deduce the relative heats. 



In the following Tables the obseryed and calculated results 

 of the determinations of specific heats of yarious gases made in 

 accordance with the methods described aboye are recorded. In 

 those Tables, — 



W represents the weight of water in the calorimeter ; 



G the weight, in kilogrammes, of water entering the balloon, 



and the volume, in litres, of the gas flowing from the 



balloon ; 

 B the barometric pressure ; 

 p the pressure read off on the manometer k ; 

 % the temperature of the gas in the caoutchouc balloon ; 

 n the duration of the experiment, in minutes ; 

 a the volume of gas passing from the balloon per minute ; 

 t the temperature of the surroundings ; 

 T the mean temperature of the calorimeter during the initial 



period ; 

 m the rise of temperature of the calorimeter in each minute 



of the initial period ; 

 Tx the mean temperature of the calorimeter during the final 



period ; 

 m l the rise of temperature of the calorimeter in each minute 



of the final period : 



