oj Gibbs's Theory of Surface- Concentration. 519 
It is worthy of note that these values are of quite the same 
order as those obtained at the very curved surface in the 
emulsion method. 
The calculated amount for this particular concentration 
(0*25 per cent.) gave 
^7p — = 3' 6 x 10 -8 gram per square cm. 
We therefore find in this case also, that the experimental 
value for T far exceeds the calculated value. Thus over 
98 per cent, of the total observed effect is z^accounted for in 
the theoretical calculation. 
This result is unexpected, especially when one remembers 
that in this latter method of determining T the condition of 
planeness of surface is fulfilled to a very high degree of 
approximation ; for the drops at the surface of which 
adsorption took place were of practically the same diameter 
as those produced by the drop-pipette in carrying out the 
measurements of — ; i. e., the drops are very large in com- 
parison to the sphere of molecular action. One would have 
expected, therefore, that the calculated result (dependent as 
it is on the value of -7-) would be in good agreement with 
dc J ° to 
the experimental value of T. 
One point of considerable interest lies, however, in the 
good agreement observable in the experimental values of Y 
obtained by the two methods. On the one hand, it appears 
to point (at least as far as one may rely on the accuracy of 
the determinations of V) to the fact that the tension even at 
very great curvatures does not differ appreciably from that 
at an approximately plane surface. On the other hand, since 
the portion of the adsorption which is unaccounted for is so 
much greater than the value required by theory, it is possible 
that even considerable variations in this latter would be 
undetected owing to the " swamping " effect of the excess 
values. 
Discussion of Results. 
The net result of the foregoing experiments is to show 
that between observed and calculated values there is a very 
great discrepancy — the actual quantity adsorbed being about 
eighty times the calculated amount. The most obvious 
explanation lies in the existence of some assumption in the 
theory which has been overlooked in practice. 
