140 



BUTLER 



ART. D 



A comparison of the observed osmotic pressure of solutions of 

 cane sugar, a-methyl glucoside and calcium ferrocyanide with 

 values calculated from the vapor pressures by means of this 

 equation has been made by Berkeley, Hartley and Burton,* 

 taking for Vi the mean value between Po and P. The following 

 table gives their data for solutions of cane sugar and a-methyl 

 glucoside at 0°C. 



TABLE IV 



Concentration, 

 grams sugar in 

 100 grams water 



loge(po/p) 



vi 



Calculated 

 osmotic 

 pressure 



Observed 

 osmotic 

 pressure 



Perman and Urryf have expressed Vi as a linear function of 

 P — Po, by the equation 



V, = h' (1 - s(P - Po)), 



and (184) then becomes 



At f^ 



— log (px/pi«) = - j^^ -V.' {1 - s{P - Po)} dP 



Ml 



= - h' (P - Po) 1 - 



(■ 



s(P - Po)' 



)■ 



(185) 



where the relatively small term sPo'^ is neglected. 



♦ Phil. Trans., 213, 295 (1919). Osmotic pressures from Proc. Roy. 

 Soc, A, 92, 477 (1916). 



t Proc. Roy. Soc, A, 126, 44, (1930). 



