418 



If then the expressions fl) and (2), are compared, it appears that 

 the vahie of dp can be greater or smallei' than dp^. ¥ov tlie same 



solution dx is namely ^ d,i\. Hence if > — the change in 



.t'j V 



external pressure will be greater than the osmotic pressure; if 



V. 



-<^~ the osmotic pressure will increase more rapidly than the 



pressure along the liquid binodal. In the tirst case the thermodynamic 

 potential A will be greater in the mixture than in the pure state; 

 in the second case it will be smaller. The former is the case for 

 the dilute solutions of hexane in water; the latter for dilute solu- 

 tions of water in hexane. 



The case, therefore, which presents itself on the waterside will 

 .evidently in general be found when the liquid branch in the P-a' 

 section rises very rapidly in pressure with increase of x, i.e. much 

 more rapidly than the corresponding gas binodal. Then the value of 



~ can be greater than the quotient of vapour- and liquid volume. 



The discussed phenomenon will, accordingly, be met with in several 

 cases. Solutions of gases sparingly soluble in water, e.g. hydrogen, 

 will certainly present the same phenomenon. 



Anorg. Chem. Laboratory of the Universitii of Amsterdam. 



Physiology. — " Variations of state in gelatin-solutions.'" By 

 L. Arisz. (Communicated by Prof. H. Zwaardemakkr ) 



In a previous communication^) a number of experiments were 

 discussed from which it appeared that a gelatin-solution undergoes 

 a change by a variation of temperature, in consequence of which 

 the intensity of the TvNDALL-phenomenon assumes another value 

 under for the rest equal conditions. The following formula has been 

 given by Lord Rayleigh for the intensity of the Tyxdali. -phenomenon: 



V = size of the particles 

 r rr: distance of the particles 

 7. =z wavelength 

 As particles to which the dispersion must be attributed the gelatin 



1) These Proc. XVI p. 331. 



