442 CHEMICAL DYNAMICS 



From these results it is clear that the velocity of reversion is 

 by no means directly proportional to the concentration of pepsin, 

 nor even proportional to the square root of the ferment-concen- 

 tration. While the velocity of synthesis in the most concentrated 

 solutions (25 to 15 cc. of 10 per cent pepsin in 100 cc.) roughly 

 approximates to direct proportionality to the concentration of 

 ferment, in the more dilute solutions (10 to 5 cc. of 10 per cent 

 pepsin in 100 cc.) the velocity of synthesis falls off with extraor- 

 dinary rapidity as the concentration of the ferment diminishes. 

 Making every possible allowance for experimental error arising 

 out of loss of material during the estimation, an increase in 

 pepsin-concentration from 1.0 per cent to 1.5 per cent multiplies 

 the velocity of the synthesis over 10 times, while an increase in 

 pepsin concentration from 1.5 per cent to 2.5 per cent only 

 doubles it; these facts are obviously irreconcilable alike with 

 direct proportionality between the velocity of synthesis and the 

 concentration of ferment, and with the Schiitz rule of propor- 

 tionality to the square root of the concentration of the ferment. 

 The velocity of reversion does not bear the same relation to the 

 concentration of ferment that the velocity of hydrolysis does; 

 hence the ratio of the velocity constants of hydrolysis and re- 

 version must be dependent upon the concentration of the ferment, 

 or, in other words, the equilibrium between protein and its products 

 must, to some extent, be altered by pepsin. 



We have seen that a reversion of the hydrolysis of paranuclein 

 can be brought about without any previous concentration of the 

 products of its hydrolysis, provided the temperature be raised 

 to 60-70 degrees. In the light of this fact there can be little 

 doubt that a shift in the station of equilibrium between para- 

 nuclein A and its products occurs as a result of the addition of 

 pepsin and that this shift in equilibrium is favored by a rise in 

 temperature. 



That a shift in equilibrium is involved even at lower tempera- 

 hydrolysis (56). The number of cubic centimeters neutralized by one gram 

 given above is the lower figure, obtained directly after complete solution, 

 judged by the disappearance of obvious particles within the solution. I have 

 obtained figures as high as 5.2- after allowing the solution to stand for about 

 an hour at a warm temperature before titration. The titrations in the experi- 

 ment described were performed immediately after the complete disappearance 

 of obvious particles. 



