On Gibbs's Theory of Surface- Concentration. 499 
Dr. Chree Las given the following approximate formula 
for use when c/l is small *: — 
ml = 7r(l-±7T*c*/P). 
It is stated to be satisfactory so long as ( c/Z) 3 7r 3 /6 coth7r 
is small compared with unity. As a matter of fact we find 
that, when c/l is one-sixth, Chree's formula is correct to within 
0*005 per cent., and the error is less than one per cent, even 
when c/l is one-half. 
The number of vibrations per second is given by the 
formula 
"EI 
pcol 4 
September 1907. 
-£v/; 
XLYII. An Experimental Examination of Gibbs's Theory of 
Surface-Concentration, regarded as the basis of Adsorption, 
with an Application to the Theory of Dyeing. (From the 
Muspratt Laboratory of Physical and Electrochemistry, 
University of Liverpool.) By W. C. M. Lewis, M.A.f 
Contents. 
I. Object of the investigation; the characteristics of Adsorption 
Phenomena. 
II. Theoretical Discussion ; Gibbs's Theory of Surface Concentration ;. 
Milner's Calculations. 
III. Experimental Methods and Apparatus ; Results. 
IV. Application to the Theory of Dyeing. 
V. Summary. 
I. Object of the Investigation. 
UNDER the term "Adsorption "are grouped phenomena 
which may be regarded as forming an intermediate 
stage between chemical combination on the one hand, and true 
absorption or solution on the other. Different types of 
Adsorption have been studied, but in general a solid substance 
(e. g. charcoal) has been utilized as the adsorbent body. 
The present paper is an account of an experimental attempt 
at measuring adsorption effects quantitatively and interpreting 
the values obtained in the light of Gibbs's theory of surface- 
concentration. The treatment is novel in that the adsorption 
has been measured at a liquid-liquid interface ; for it is only 
when dealing with liquid interfaces (or surfaces) that it is 
* Phil. Mag. [6] vol. vii. p. 517, May 1904. 
t Communicated by the Physical Society ; read February 28, 1908. 
