94 



Dr. W. M. Bayliss. 



[Apr. 7, 



of conductivity changes from 1300 to 1800 recip. megohms. The total change 

 being about 3500, this is therefore the middle part of the reaction. 



Invertase was taken as a case where only one of the components of the 

 system, viz. the enzyme, is in the colloidal state, the substrate, cane-sugar, 

 being in true solution. It might be expected that the conditions would be 

 such as to give a relationship more nearly that of a linear one. 



The invertase experiments were made at a temperature of 25° C, in order 

 that the rate of the reaction should not be too rapid. Samples were removed 

 at intervals, mercuric nitrate added to precipitate the enzyme, excess of the 

 reagent removed by caustic soda, filtered, made up to known volume, and 

 finally the optical rotation determined for the mercury green line, using a 

 three-field polarimeter by Schmidt and Haensch. The results were dealt with 

 in a manner similar to those with trypsin and give the curve F of fig. 1. 

 The value of n for the stage of the reaction taken, viz., time taken for one- 

 quarter inversion, is unexpectedly high, 3 - 7. I am unable to suggest an 

 explanation for this wide divergence from both the linear and the square-root 

 "laws." The separate curves of velocity of reaction were very nearly 

 straight lines. 



It seemed that it would be of interest, in view of the way in which the 

 value of n in the adsorption of Congo red by paper is affected by the presence 

 of electrolytes, to investigate how it is altered in the case of enzyme and 

 substrate when electrolytes are present. I have shown* that, in the former 

 case, the value of n is increased by the presence of electrolytes, so that the 

 process approaches more nearly to a chemical one, the amount taken up being 

 more nearly the same at different concentrations. In a chemical reaction 

 with precipitation, of course, n is infinite, since y 1/n must be unity. 



As an example from the case of Congo red and paper, n was found to 

 have the value of T15 in the absence of foreign electrolytes and 1*67 in the 

 presence of 0'002 molar calcium sulphate, or 0-04 molar sodium chloride. 



The corresponding experiment with trypsin was performed as follows : — 



Four conductivity vessels were filled with : 



A. 10-per-cent. ammonium caseinogenate 5 c.c. + H 2 5 c.c. + 5-per-cent. trypsin 2 c.c. 



B. „ „ + „ + 5/3-per-cent. „ 2 c.c. 



C. „ „ +0-013 m. CaS0 4 5 c.c. +5-per-cent. 



trypsin 2 c.c. 



D. „ „ „ -|-5/3-per-cent.' 



trypsin 2 c.c. 



In thermostat at 38° C. Conductivity determined at intervals, curves 

 drawn, and values of n, etc., calculated as in previous experiments. Table IV 

 gives the data obtained. 



* ' Kolloid-Zeits.,' 1910, vol. 8, p. 4. 



