580 



Messrs. E. Beard and W. Cramer. 



discuss here the conditions on which adsorption depends. In connection with 

 the present problem the phenomenon of adsorption is of interest only in so 

 far as it presupposes as a preliminary condition a concentration of the 

 adsorbed material at the surface of the adsorbing material. It must also be 

 borne in mind that such a surface concentration may occur without adsorption 

 taking place, as in the case of foam, for instance, where the surface separates a 

 gas and not a solid from the liquid. We shall, therefore, use the general 

 term of " surface concentration " to describe the alteration of concentration 

 produced in a system by altering the surface energy, and the term 

 " adsorption " in order to designate the special result which is caused under 

 certain conditions by surface concentration. If it can be shown then that 

 under the conditions of our experiments invertase is adsorbed by glass beads, 

 we would have evidence that the factor of surface concentration accounts, at 

 any rate partially, for the retardation of the ferment action observed in our 

 experiments. If, on the other hand, no adsorption is observed, no conclusions 

 can be drawn either for or against this possibility, as one may conceive of 

 surface concentration occurring without adsorption. 



To test this point, experiments were carried out, in which invertase was 

 kept in contact with glass beads. Another portion of the same ferment 

 preparation was allowed to stand in a test-tube by itself at the same 

 temperature as a control. After a definite number of hours the ferment 

 solution was removed from the glass beads and its activity compared with 

 that of the control. The former preparation will be described in the Tables 

 as "contact invertase," the latter preparation as " control invertase." 



The following experiments may be given as examples of the results 

 obtained : — 



Experiment E. 14.5.14. Invertase D, 6.5.14, 5 per cent. 

 Kept for 93 hours at 38°, (1) in contact with beads ; (2) alone as control. 

 5 c.c. of each of these two preparations mixed with 5 c.c. sucrose solution, 

 5 per cent. Digested at 38°. 



Hours. 



Contact invertase. 



Control invertase. 







+ 3-26 



+ 3 -25 



5 



+ 3 25 



+ 2-23 



27 



+ 1-98 



-0-86 



(Note that in this experiment the relative amount of ferment used for inversion is very large.) 



