LIVING MATTER AND ITS PRODUCTS 143 



of any fixed quantity of matter from one chemical form to the 

 other, we have: 



C+H+V=0 



If attention be paid to change of sign any of these three quantities 

 may be moved from one side of the equation to the other. 



Hence if C represent chemical energy disappearing and given 

 out in the other two forms we have: 



Let us take it that a grm. molecule of the substance changes 

 chemical form, and that the volume of the solution in which such 

 a change occurs is so large that no appreciable change takes place 

 in the osmotic pressures of the two substances in solution. 



Then in the above equation C is the change in chemical energy 

 accompanying a change in chemical constitution from the first 

 form on one side of the chemical equation to the other form 

 on the other side of the chemical equation. As C is dependent 

 only on the change in chemical constitution it is a constant, the 

 value of which is determined by the sum of the values of (1) the 

 heat (H) for the change of a grm. molecule at given concentrations 

 (Pj. and P 2 ) in solution of the two substances on the two sides of the 

 chemical equation, (2) the change in volume energy due to the 

 conversion of a grm. molecule of the first substance at pressure P x 

 into a grm. molecule of the replacing substance at pressure P 2 . 



The heat energy produced by the change of a grm. molecule 

 when the first substance has a pressure P x and the second substance 

 a pressure P 2 is a variable quantity dependent upon the values 

 of P! and P 2 . 



The value of V, the change in volume energy for the change 

 of a grm. molecule of first substance at osmotic pressure P x into 

 second substance at pressure P 2 , is also a variable. 



When as the result of a reaction a grm. molecule of a sub- 

 stance comes into solution at a definite pressure, a certain fixed 

 amount of volume energy appears dependent upon the pressure, 

 and as a result the heat produced will be less by this amount ; and 

 similarly when a grm. molecule disappears at another different 

 pressure, a definite amount of volume energy disappears, and by 

 this amount the heat of reaction will increase. Accordingly the 

 difference in these two amounts will express V, the change in 

 volume energy in the reaction. 



