3 



At intervals portions of the main solution were made slightly 

 alkaline with sodium carbonate and their rotations read. These 

 readings give the real course of the hydrolysis and are shown in 

 column 3 of Table I 

 and curve II of figure 1 . """' 

 The emulsin solution 

 before the addition of 

 the salicin had a rota- 

 tion of -3.0 in a 50 

 cm length ; as the ad- 

 dition of sodium car- 

 bonate to the emulsin 

 in the absence of sali- 

 cin did not change its 

 rotation, the latterwas 

 corrected for by the 

 subtraction of 3.0 

 from all the readings, 

 referred to -62.0 



FIG. 1. Real (I) and apparent (II) courses of the hydrolysis of 

 salicin by emulsin. 



As thus corrected, the readings were all 

 as the specific rotation of salicin for sodium 

 light, the factor by w T hich they were multiplied being 5.17. 



TABLE I. Real and apparent courses of the hydrolysis of salicin by emulsin, temperature 



30 C. 



1 -p -p 



Calculated by the usual formula, ki= - log 9~ ^ ; the value of R<x is calculated from the motec-ular 



t R RCO 



weights and specific rotations of salicin and glucose, as other experiments which have been made by the 

 authors show that the hydrolysis of salicin by emulsin is a complete one. 



The data of Table I show that the usual polariscopic method of 

 following the hydrolysis by reading the rotation of the neutral or 

 slightly acid solution gives wholly incorrect results. The true rxt-nt 

 of the hydrolysis can only be found when means are taken to correct 



[Cir. 47] 



