488 Mr. W. C. M. Lewis : Experimental Investigation 



The tension was plotted against T, and the tangent to the- 

 curve taken at the point corresponding to a bulk-concentration 

 0*114 per cent. The tangent gives 



da 



7*25 ergs/cm. 2 



7-25 xlO 1 



dT 1 X 10 ~ 10 gram-moles/cm. 2 

 At this point 



r = 2 x 10~ 8 grm./cm. 2 = lx 10 -10 gram-moles/cm. 2 

 The equation therefore becomes 



7-25 x 10 10 



log;c 2 =log,f 1 + 



RT 



.-. l O g 10 c 2 = logio 0-0064 + 0-044 

 = -2*1498. 



.*. c 2 = 0*0071 gram-moles per litre 

 = 0-00138 grm./c.c. 



Now i£ D is the range through which the surface-concen- 

 tration effects are practically complete, it follows that the- 

 average concentration in the surface-layer is given by the 

 expression 



C2 ~B' 



or 



D = 



c 9 



and on substituting the values obtained above it is found that 



D = 14 x 10- 6 cm. 



It is evident that we have here obtained a value for the 

 u range of molecular action/' as may be seen by comparing 

 it with other estimates of the same quantity. 



Quincke 



Eeinold & Rucker. 



Wiener 



Plateau 



Drude 



Parks 



5X10" 

 1-2x10" 

 1-2x10" 



11-4x10" 

 1-7x10" 



13-4x10" 



Jobonnot from to 10 



Method. 

 " Wedge method." 

 Limiting thickness of soap film. 

 Effect on phase of reflected light. 

 Limiting thickness of glycerine film. 



„ ,, soap film. 



Wetting of powders. 

 Soap film. 



