Dissociation of Compounds in Water. 489 



by Arrhenius *, in reference to osmotic pressure, and then he 

 has shown the relation between osmotic pressure and lowering 

 of the freezing-point. In the formula for osmotic pressure, 



tt-AK + BK 2 , 



7r= osmotic pressure, A = product of gas constant R with the 

 absolute temperature, B a new constant, a measure of the 

 difference between the attractions of the solvent-dissolved 

 body and the dissolved body-dissolved body, K = concen- 

 tration. When the concentration K is small, BK 2 vanishes 

 with respect to AK, and we have the law for ideal gases. 

 But as K increases, the osmotic pressure would increase or 

 decrease relatively, depending on whether B is positive or 

 negative. But with water as a solvent, B is generally posi- 

 tive. Thus as solutions which satisfy the above condition 

 increase in concentration, the osmotic pressure would increase 



IT 



more rapidly, and ^ would increase. Later in the same 



communication he has shown the proportionality between 

 osmotic pressure and lowering of the freezing-point. Since 

 the lowering of the freezing-point is proportional to the 



c 



osmotic pressure, ^ (e = lowering of freezing-point) would 



increase, and this agrees with the facts of experiment. 



On the other hand, Bredig f has pointed out that when — 



vi 



for very dilute solutions is great as compared with -, non- 

 electrolytes may show too great a lowering of the freezing- 

 point. K = the attraction between the molecules of the solvent 

 and those of the dissolved body ; v = volume of the dissolved 

 body ; a = attraction of the molecules of the dissolved body 

 for each other ; and vi = volume of the solvent. 



Natanson J has also discussed results from freezing-point, 

 boiling-point, and osmotic-pressure determinations. 



These theoretical considerations may prove to be competent 

 to explain all the facts which may be brought to light. On 

 the other hand, it may be necessary to supplement the 

 present theories to account for them. In reference to this it 

 seems that we must wait until many more compounds have 

 been investigated, and more facts are at hand. 



Dextrose. — The molecular lowering for dextrose agrees 



* Arrhenius, Zeits. phys. C/iem. x. p. 51. 



f Bredig, ibid. iv. p. 444. 



X Natanson, Zeits. phys. Chem, x, p. 748, 



