VELOCITY OF REACTION. HOMOGENEOUS SYSTEMS 6 1 



Further we have : 



In many cases the first term, i, in the denominator is 

 little as compared with the terms under the sign of sum- 

 mation and may therefore be neglected. In this case we 

 get the formula of Bodenstein if we put n i, and suppose 

 the terms under 2 to be two, one in which /= i and g = o, 

 another in which / = o and q\. In nearly all cases 

 hitherto investigated the velocity of reaction is nearly pro- 

 portional to the first power of the concentration of enzyme 

 present; therefore the deduction is given only for this 

 case. The more general formula, in which this concentra- 

 tion enters to another power than I, is very complicated. 

 A very common case is that in which only one term with 

 /=o and q= i enters under the sign 2 ; this is the case 

 in the digestion of egg-white by pepsin and trypsin and 

 for the hydrolysis of fat by means of lipases. Here also 

 the term i may be dismissed. This holds good even for 

 the experiments of Armstrong, in which the product of 

 reaction is proportional to the square root of the time of 

 reaction. Here/ = i and 4=1, i.e. the chief influence is 

 due to the formation of a compound between the enzyme, 

 the reaction-product, and the original substance. The for- 

 mula is evidently not valid, if the quantity of substance 

 acted upon by the enzyme or the reaction-product is to a 

 great part bound by the enzyme. Therefore the formula 

 gives no good values for the experiments of Terroine with 

 small quantities of maltose. It will be necessary to carry 

 out a large number of experiments in order to verify this 



