568 Mr. S. A. Shorter on Surface Separation from 



lines have been drawn to correspond to multiples of 46*8 

 dynes per cm. (the value deduced from the experiments 

 shown in fig. 2). Each reading consisted of ten observations 

 of as many oscillations as could be observed at once. Two 

 values of the surface-elasticity were calculated, one from the 

 first five, the other from the second five. The results con- 

 firm the above theory. It will be seen that whenever the 

 two values differ appreciably, the second value is less than 

 the first, and that this decrease always occurs between two 

 consecutive molecular values. 



Summary of Results : Solutions of Saponin. 



In Table I. are summarized the results of a number of 

 experiments, including those shown in figs. 2, 3, and 4. 



Table I. 

 Solutions of Saponin. 



Age of 

 Surface 

 (days). 



Molecular Thickness op Surface Layer. 

 Concentration: 1 part in 



45-4 



100 



5568 



10,000 



100,000 



106,000 



315,000 



10 6 



2-95X10 6 



10 7 



1 



2 



3 



4 



5 



6 



7 



8 



9 



10 



15 



20 



25 



30 



40 



50 



60 



70 



80 



90 



5-6 



7 



7 



8-9 



9 



9 



9 



9 



11 



12 



12 



12-13 



13 

 14-15 

 15 

 15 

 15 



7 



8-9 

 8-9 



10 



10 



10 



10 



11-12 



13 



13 



10-11 

 10-11 

 11-12 



12 



12 



12 

 13-14 

 13-14 



15 



15 



11-12 

 12^-13 



13 

 13-14 

 13-14 



14 



14 



8-9 



10-11 



12 



13-14 

 13-14 

 13-14 

 13-14 



11-12 

 13-14 

 13-14 

 13-14 



14 



14 



14-15 



14 



15-16 



16-17 



16 



17 



18 

 18-19 



20 



11 

 11-12 

 11-12 

 11-12 



13 



13 

 14 



14-15 



15 

 15-16 



16 



15 



16 



7-8 



9 



10 



10 

 10 

 10 



5 



6-7 

 6-7 



7-8 



7-8 

 7-8 



i'6 



10-11 

 10-11 

 11-12 



1-2 



2 



4 



4-5 



It will be seen that the rate of growth of the surface 

 pellicle does not vary much within wide limits of concen- 

 tration. The rate of growth is less, not only in the case of 

 very dilute solutions (as might be expected), but also in the 

 case of concentrated solutions. 



