on Osmotic Theory, 271 



We may, therefore, state that when the concentration a 

 is increased, in general, the osmotic pressure P a will decrease, 

 whilst P ft will increase; and there are four ways in which 

 the pressures on the liquids may be changed so as to keep 

 osmotic equilibrium. 



(1) Keeping p constant, p & will increase to p & ! , and p b de- 

 crease to p b ', that is, P a decreases while P 6 increases. The 

 graphs resulting from this view-point are given in the 

 diagram of " S and S," p. 260. 



(2) Keeping p a constant, p will be decreased to p' 

 (P a decreases), whilst p b will also be decreased to p b \ but the 

 change in p b will be greater than the change in p (P 6 

 increases at an enhanced rate). 



(3) Keepings constant, precisely the reverse of (2) will 

 result. 



(4) If we start with a system such that the three liquids 

 are in osmotic equilibrium and impose the restriction that 

 p and p b are both to remain constant, we cannot maintain 

 the equilibrium when the concentration is changed. We 

 can, however, measure the osmotic pressure if one or the 

 other of the pure liquids be shuttered off, and in this way 

 two new sets of osmotic pressures will be obtained. Thus, 

 in all there are four sets of complementary osmotic pressures. 



Fig. 3. 



1(10 % of 

 A. 



Whichever scheme of viewing osmotic phenomena we 

 adopt, the general character of the curves is that shown in 

 fig. 3. 



