Solutions of Saponin, Peptone, and Albumin. 



507 



It has already been mentioned that the surface-elasticity 

 sometimes decreased during the taking of a reading. At 

 first this was attributed to the impairing of the elasticity by 

 the motion set up. It was found, however, that this decrease 

 occurred only in certain cases. In other cases the elasticity 

 was unaffected by the taking of the reading. This point 

 was further investigated in the light of the above theory. 

 It was found that the decrease always occurred between con- 

 secutive molecular values, and that if the process of taking 

 the observations was continued, the surface-elasticity generally 

 decreased to the lower molecular value and then remained 

 constant. This was not always the case. Occasionally an 

 intermediate value was found to be stable, and in a few cases 

 the elasticity fluctuated irregularly between two molecular 

 values. In these latter cases there was a striking increase 

 in the rate of damping of the oscillations. Thus at first it 

 might be possible to count twenty oscillations, and the 

 damping would increase till it was difficult to count ten. 



The molecules forming part of an incomplete molecular 

 layer are evidently easily detached from the surface pellicle, 

 even when the layer is sufficiently complete to give an elastic 

 effect nearly equal to that of a complete layer. The fact 

 that the surface-layer rapidly recovers its initial value, seems 

 to indicate that the detached molecules are not completely 

 absorbed into the body of the solution, but remain in a kind 

 of transition layer from which they easily separate out again 

 in the surface-film. In the cases where the recovery is so 

 very rapid that it occurs during the taking of the reading, 

 there will obviously be a damping effect produced which 

 will be absent when the cohesion between the pellicle and 

 the molecules of the incomplete layer is for the time being 

 totally destroyed. pj~ 3 



15 



14 

 15 



1 1 

















,/T^/' 



r iv 







/l !- 



f •' \ 







. 



^wV 1 







- ■■— 



k 











1 1 

 10 



pvi 











1 



Jays 







\ 



5 10 15 20 



Fig. 3 shows the results of an experiment with a solution 

 of saponin containing 1 part in ootiS of water. The horizontal 



