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



Experimental Results : Solutions of Saponin. 



Fig. 1 shows the results of an experiment with a solution 

 of saponin containing 1 part in 106,000 o£ water. The con- 

 secutive points have been joined together by straight lines. 



Fijr. 1. 





800 



800 



S3 

















o 

















k-4 





— «*-v/ 



v A 











700 

 GOO 



f 





iU> 



r 1 

















Age of 



vWacE 



■; Days 



















20 



'30 



40 



50 



60 



70 



As will be seen later, a smooth curve drawn so as to give 

 the closest fit to the points would have no physical meaning. 

 Three important facts will be noticed from these results : — 



(1) The constancy of the surface-elasticity over a pro- 



longed period does not necessarily indicate equi- 

 librium between the surface pellicle and the body 

 of the solution — the elasticity being liable to 

 increase suddenly to a higher value after remaining 

 constant for several days. 



(2) The surface- elasticity is very liable to sudden fluc- 



tuations of value, especially in the later stages of 

 the experiment. 



(3) There is no sign of equilibrium even after several 



weeks. 



Fig. 2 shows the results of experiments with solutions of 



saponin of different concentrations. The horizontal lines 



have been drawn to correspond to multiples of 4:6'8 dynes 



per cm. In the first instance the results were plotted in the 



80. 



