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



in addition an important fact not shown very decidedly 

 fig. 2, viz. that the stepwise mode of increase of the surface- 

 elasticity is not entirely due to the molecular dimensious of 

 the surface-layer — the actual rate of surface separation varies 

 in an irregular manner. The history of the surface-layer 

 of the 1 in 145,000 solution between the ages 28 and 4-0 days 

 shows this very clearly. Another noteworthy point is that 

 the increase of the surface-elasticity in the case of the two 

 dilute solutions is, broadly considered, linear from near the 

 beginning to the end of the experiment. 



In the case of concentrated solutions of peptone and 

 albumin there is a rapid initial thickening of the surface- 

 film followed by a rapid thinning. In some cases this was 

 followed by a second thickening much slower, however, than 

 the first. 



The results of a number of experiments are summarized 

 in Tables II. and III. 



Table II. 

 Solutions of Peptone. 



Age of 

 Surface 

 (days). 



Molecular Thickness of Surface Layer. 

 Concentration : 1 part in 



89 



183 



530 



1152 



2900 11,170 



27,000 



145,000 



1 



2 



3.'.'.'.'.'. 

 4 



6.'.'.'.'.'. 



7 



8 



9 



10 



11...... 



12 



13 



14 



15 



20 



25...... 



;:o 



40 



50...... 



60 



2-3 



4 

 7 

 9 

 10 

 6 

 2 



1 

 1 

 1 

 1 



2 

 2 



7 



9-io 



9 



9 

 9 



7-8 



5 



9 

 11 

 10-11 

 11 

 10 

 10 

 10 

 10 

 10 

 ... 



11 



8-9 



8-9 



29-30 

 24-25 



19 



15 



11-12 



ii 



10-11 

 8-9 



7-8 

 7 

 6 

 6 



6-7 



1 



... 



8 

 9-10 

 9-10 



8 



8 



8 



9-10 

 12 

 12 

 12 

 12 

 12 

 12 

 12 

 12 

 12 



12-13 



13 

 14-15 



14 



15 



16 

 17-18 



19 

 21-22 



4-5 



7 



*9 

 9-10 



w . 



15 



20 



28 



7-8 

 8 



10 

 10 



12 



12 



12 



12 



13 

 14-15 



15 

 17-18 



19 

 °2-23 

 ~27 



29 



