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5. to the attraction and repulsion by all the molecules V—_NX;", 
Mn. 
During the greater part of 4 the Ath molecule S is found in 
volume elements far inside the region G, and only during a very 
small part of 6 in the periferie volume elements of G close to the 
surface 2. Let us now first direct our attention to a volume element 
de dy dz far in the interior of the region (G, far from &. Repeatedly 
the molecule .S; is found for a short time in this element. 
In this we find that: 
An Xp, Vn Va", Ze + Zi 
assumes now positive, now negative values of rapidly varying 
amount, and — because we are far from @, in the midst of the 
homogeneous solution — equally frequently equally large positive as 
negative values. Because besides X7’, Yn’, Zi’ are always zero, 
it is clear that the mean contribution to the virial yielded by the 
ht molecule S, i.e. S;, during its residence in an “internal” volume 
element dx dy dz of the region G, is: 
de dy dz{e#X,+yY,i2AJ—=0..... (1) 
and likewise for every “internal” volume-element. This is no longer 
the case for ““peripheric” volume elements close to the surface @. 
Here in the direction of the normal to 2 the symmetry is disturbed: 
1. The force exerted at the impact by 2 on the molecule Sj is 
always directed inward ; 
2. The joint molecules S, which act on S, all lie on one side 
of 2 (the inside); 
3. On account of the presence of the molecules S the concen. 
tration of the water on the inside of @ is different from that on 
the other side. 
Let us now add the contributions yielded by all the mole- 
cules S during their presence in all the ‘‘peripheric” volume elements 
to the second term of the equation (A): Thus we get corresponding 
to the above mentioned three kinds of forces an expression with 
three terms: 
yi (A7 Uh, a. % Yh + Lh Zh) = W' + w" ao Vi Aenea. (2) 
If the concentration C, of the molecules decreases to zero, W' 
becomes small of the same order of magnitude as Cy, on the other 
hand W" and W" of higher order. 
1) We draw attention to the fact, that this holds as well for repulsive as- for 
attractive forces. 
