LIVING MATTER AND ITS PRODUCTS 163 



The effect of change in temperature is on the whole opposed to 

 that of change of chemical energy ; a rise in temperature having the 

 same effect as a drop in chemical energy and tending to increase 

 the reversibility of the reaction. 



This is seen from the fact that the part of the constant K, which 

 changes with alterations in chemical energy C and temperature T, 



c 



is the expression e RT , in which it is clear that similar changes in C and 

 T balance each other. In the simple form of reaction P B = K.P A , 



illustrated in the diagram (p. 158), this is quite clear, for increase in 



p ? 

 T will cause similar increase in the expression RT log p", and hence 



* A 



will place each point on the curved line farther from the base-line, and 

 so bring the equilibrium point that is, the point where the curved and 

 horizontal lines lie at an equal distance from the base-line XX' nearer 

 to the mid point. Accordingly increase of temperature acts like low 

 value of chemical energy and increases reversibility. 



In the more complex forms of reaction, such as P B = K.P 2 A , etc., 

 the form of the curved line representing change in osmotic energy 

 varies; it is still asymptotic at both ends, but no longer crosses the 

 zero line at the mid point between X and X'. Hence increases from 

 zero in the value of C in one definite direction only will up to a certain 

 limit bring the point of crossing nearer the mid point, and so increase 

 reversibility. Similarly, if the value of C is taken as fixed, increases 

 in T up to a fixed limit will decrease the reversibility, but later for 

 higher values will increase it. Hence in those cases where the number 

 of molecules is altered in the reaction there is at a certain given point 

 in each case of change in C or change in T, a reversal in the effect. For 

 higher values of C or T, however, effects of increase of C to high positive 

 or negative values is to throw the crossing farther along towards the 

 asymptotic portion of the line at either end, and so diminish the rever- 

 sibility ; while effects of increase of T at higher values, C being fixed and 

 moderately low, is to throw the crossings farther from either end point 

 and so to increase reversibility. 



