110 THE ROYAL SOCIETY OF CANADA 
where K is the equilibrium coefficient, which is constant at a given 
temperature, q is the “heat of reaction,” and T the absolute tempera- 
ture. q, expressed in gm-calories, represents the change of the total 
energy, and is the sum of the heat produced in the process and of the 
external work performed. Hence, the actual heat produced in the 
process of solution (Q) is given in the present case by 
q = Q — RT, 
where R is the gas constant expressed in gm-calories and equals 1.99. 
Applying the general formula to the case here, S takes the place 
of K, and we have 


d log, S — 6 Jeti (8) 
dT Ral? Rae 
or d log, 8 1 OA 
dT Ak hile 
Q is nos a constant since it varies with the temperature; but we can 
obtain approximate values of Q by considering it constant between very 
close limits of temperature and integrating the equation between these 
limits. 
Let S, = the solubility coefficient at absolute temperature T, 
and $, = the coefficient at absolute temperature T, which is not 
very different from T,. 
Integrating the equation just given and substituting corresponding 
values of S and T, we have 

Q. 
log. S = los T+ —— CC 
RY, 
Q. 
log, 8, = Jog, 7; + —— + C 
RYT, 
C being the coefficient of integration. 
Subtracting 
O Fa 1 
log, 8; — log, $, = log, T, — log, T, + — § — —— fs 
? Ai ee 
from which | Ss, I 
ee) | Woy Oe 
S, dhe 
Bes 
1 1 
Ate 
From this equation Q can be calculated. 
