CALORIMETRICAL MEASUREMENTS. 303 



heating the circuit by the passage of the current. The only pre- 

 caution is to keep the temperature of the bisulphide constant, 

 especially in the most efficacious layers. 



917. CALORIMETRICAL MEASUREMENTS. The calorific energy W, 

 developed in time /, in a conductor of resistance R is 



If the wire is placed in a calorimeter, the quantity of heat Q 

 imparted to the liquid will be 



where J is the mechanical equivalent of heat, and therefore 



R/ 



Let M be reduced value of the total mass of the calorimeter, 

 T! - T the rise of temperature, apart from the correction for losses 

 by radiation or by conductivity \ we have Q = M (Tj - T ), and there- 

 fore 



R 



In order to allow for variations in the resistance of the wire 

 and the specific heat of the liquid, we must assume that these 

 variations are proportional to the temperature, and put 



R = R (i+aT), 



from this we have, for the temperature T, 



I 2 R, 

 J 



or 



^T R 



l+(a-y)T JM 



^ l*dt. 



