IN LIVING MATTER 27 



For the heat of reaction at any other point we have 



or using the same notation as in the other cases, 



or 



H^RTlog - P **~ . % 2 . 

 PA PQ P 2 B 



But the zero pressure P and p Q is always the same, hence 



4. The most general form of the equation is where a number 

 of substances, A, B, C 3 &c., react with one another to form a 

 number of other substances, A x , B x , C', &c., and where the number 

 of molecules of each substances entering into reaction varies. 



Let the chemical equation be represented by 



a A. + 6B + cC + &c. 5 a A! + 6'B' + c'C' 4- &c., 



in which the small letters represent the numbers of molecules of each 

 substance respectively entering into reaction. Then the expression 

 for the change in volume energy becomes 



\a' log |' + 6' log ^ + c' log |^ + &c. - (a log | + 6 log |? 



^0 ^0 ^0 ^0 ^0 



RT 



This expression can be written 



For equilibrium, as before, this expression is equal to C, the energy 

 evolved when a grm. molecule of each substance changes from the 

 left-hand side of the equation to the right, and hence 



P . P . P? . &C. - [a+& +C +&c.-(a'+b'+c'+&c.)] 



or 



c 



c. - (a+6+c+&c.) R 



