104 



OSMOTIC PRESSURE OF AQUEOUS SOLUTIONS. 



If it can once be determined what rule or law governs the magnitude 

 of the osmotic pressure of the solute in such " ideal" solutions, it will 

 be practicable to study effectively the subject of hydration in aqueous 

 solutions. No other method of equal comprehensiveness and promise 

 is available, except perhaps the vapor -pressure method, and that, in its 

 present imperfect condition, is not adapted to the investigation of hydra- 

 tion. It is to be hoped that the study of solutions at high temperatures — ■ 

 at temperatures so high as to preclude the existence of hydrates — will 



Table 6. — Volume of weight-normal solutions of glucose at 0°. 

 [Sp. gr. glucose at 0° = 1.5567.] 



Table 7. — Volume of weight-normal solutions of cane sugar at 0° 

 [Sp. gr. cane-sugar at 0° =1.59231.] 



eventually reveal the simplest forms of the laws governing the osmotic 

 pressure in aqueous solutions. If these are once established, we can 

 then measure hydration at lower temperatures by the apparent abnor- 

 malities of the osmotic pressure. It is not to be ignored, of course, that 

 other factors than hydration may assert themselves at the lower temp- 

 eratures and obscure, to some extent, the results. 



The reasons given or implied in the foregoing statement are those 

 which decided the author and his collaborators to adopt, in the be- 

 ginning, the weight-normal system of solutions for the measurement of 



