for the mutarotation of the glucose. If the mutarotation is not 

 corrected for, the apparent course of the hydrolysis is measured, and 

 the data of column 4 show that this course does not follow the uni- 

 molecular law, since its velocity-coefficient decreases regularly during 

 the reaction. On the other hand, the data of column 5 show that 

 the course of the real hydrolysis follows the unimolecular law, for 

 its velocity-coefficient shows no regular variation. These results 

 largely explain why previous investigations, in particular those of 

 Henri, have led to the conclusion that the hydrolysis of salicin by 

 emulsin does not follow the unimolecular law, for Henri measured 

 the apparent rate and obtained a regularly decreasing coefficient 

 similar to that shown in column 4. 



The real rate of hydrolysis at was also measured, and the results 

 are reported in Table II. The concentration of the salicin was 3.5 

 per cent. The first reading was taken one hour after mixing the 

 salicin and emulsin because the temperature was somewhat above 

 zero during this hour; this reading is accordingly lower than 62.0, 

 the specific rotation of salicin. 



TABLE II. Real course of the hydrolysis of salicin by emulsin, temperature' C. 



This experiment shows a satisfactory constancy for the value of 

 kj, proving that the erizymotic hydrolysis follows the unimolecular 

 law. 



The real rate of hydrolysis was also measured at 30 C. in a third 

 experiment, as shown in Table III. The salicin solution was of 5 

 per cent strength. In this experiment the action of the emulsin 

 was stopped by quickly heating portions of the solution, a procedure 

 which also brings the mutarotation to completion; it has the advan- 

 tage over the addition of sodium carbonate that the red color which 

 the latter forms with salicyl alcohol is not produced in such intensity 

 and the polariscopic view is accordingly clearer. 



[Cir. 47] 



