Dr. F. Tinker on Osmotic Pressure. 



449 



and also \(3Y ; so that we have, 



, 7le (a) n€ (a) 



can neglect ^ ^^ 



for most moderately strong solutions, 



PV 1 -HTIog.^+Q [27] 



This equation is similar to that Van Laar and others have 

 given for the ideal solution, except that the heat of dilution 

 is included. 



Apart from the fact that the method of analysis adopted 

 in the preceding pages throws much light on the anomalies 

 of osmotic pressure and osmotic flow, still further con- 

 firmation of its intrinsic soundness becomes apparent when 

 we consider in detail the fundamental relationship which has 

 been deduced between the coefficient of compressibility of a 

 liquid and its free space. 



The following table shows the value of (V — b) for various 

 liquids, calculated from equation [20] by means of com- 

 pressibility data given in Landolt-Bornstein. The value of 

 the pressure inside the liquid is also given, being calculated 

 from the relationship 7r/3=l *. 



Liquid. 



Temp. 



°C. 



Compressibility, 

 /3X10 6 . 



(V-*). 



in c.c. 



in atmos. 



5920 

 6550 



14700 



9600 

 11100 



5810 



3150 



6290 



7460 



8270 



Ether 



Ethyi Chloride... 

 Ethylene 



13-5 

 15-2 

 100 

 13-3 

 160 

 130 

 200 

 230 

 230 

 230 



169 (at from 8-25 atmos.) 3*97 

 153 „ 8-34 „ 3-60 



68 — 1-58 

 104 „ 8-37 „ ! 2-44 



90 „ 8-37 „ 213 

 172 „ 8-37 „ 4-05 



Ethyl Acetate . . . 

 Benzene ....'. 



Arnylene 



Pentane 



Hexane 



318 — 

 159 „ 0-1 

 134 „ 0-1 



7'63 

 385 

 3-25 



Heptane 



Octane , 



121 „ 0-1 „ 



2-94 



The subjoined table gives the figures for ethyl ether at 

 various temperatures also, Amagat's compressibility data 

 being used f. 



The intrinsic pressures calculated from the relationship in 

 question are evidently of the usually accepted order of 



* This simple relationship follows immediately from the two 

 relations p = ^nm and tt=— — =. 



t Ann. Chim. Phys. (6) xxix. p. 505 (1893). 



