CALCULATIONS. 335 



During all this time the temperature of the enclosing vessel 

 only varied from 21'21 to 21'37. 



Study of the cooling. We then take a diluted solution of 

 potassium chloride, occupying the same volume as the above 

 liquid ; this is introduced into the same vessel and the 

 temperature raised so as to exceed by 3 that of the enclosing 

 vessel, just given. The progress of the cooling is again followed 

 for ten minutes ; then the excess of temperature is reduced to 

 2 by substituting a suitable volume of a cold solution of the 

 same composition for the heated solution contained in the 

 calorimeter. We then repeat the experiments on the rate of 

 cooling, corresponding to this last excess. 1 



Calculations. We thus possess all the necessary data for 

 calculating the heat disengaged during the experiment. 2 This 

 calculation is made without the aid of hypotheses, and according 

 to the rules already laid down for hydrocyanic acid (p. 306). 



In this way we obtain the quantities of heat disengaged 

 during the two stages of the experiment ; or, q l -f- q z . The 

 correction due to the cooling is 8 per cent, for the first stage of 

 the experiment in question; it reaches 12 per cent, for the 

 second stage. The total quantity of heat disengaged represents 

 the conversion of the liquid cyanogen chloride into carbonic 

 acid in solution and ammonium chloride, plus the heat pro- 

 duced in the complete saturation of the potash employed by 

 dilute hydrochloric acid. P being the weight of this potash, 

 it would give off, if treated separately with hydrochloric acid, 



p 

 h 13 '6 Cal. Let $ 3 be the quantity of heat disengaged 



by the conversion of the cyanogen chloride into carbonic acid 

 and ammonium chloride under the influence of pure water ; we 

 then get 



fc = 2i + ft - ~ 13-6 Cal. 



We have now only to multiply the quantity, q 3 , by the inverse 

 ratio of the weight, p, employed to the equivalent of cyanogen 



(\~\ * 

 chloride (61*5 grms.). It was found that q 3 X = 61*68 



Cal. (according to the average of the experiments). This value 

 represents the heat disengaged in the following reaction : 



CNC1 (liquid) + 2H 2 + water = C0 2 (in solution) + NH 4 C1 



(in solution). 



1 For this method, see "Annales de Chimie et de Physique," 4 6 seYie, 

 torn. xxix. p. 158. 



2 The only unknown quantity is the specific heat of liquid cyanogen 

 chloride. The approximate value, 0*4, was taken: it is near enough, on 

 account of the extreme smallness of the corresponding correction. 



