CONCENTRATED AQUEOUS SOLUTIONS, AND HYDRATION OF THE SOLUTE. 867 



The hope was consequently entertained that notwithstanding the doubtful nature of 

 the above assumptions, the computations referred to might throw some light on the 

 constitution of concentrated solutions, and afford additional evidence, either in confirma- 

 tion of, or in opposition to, the hydration theory. 



The hydration calculations were made from the following formulae : — 



mWAE 

 (1 +n- l a )Aw 



mW'AE 

 C = 



(1 +n- \ a )Aw 



From which W - W = W ( C ~ c ') 



C 



The number of molecules of water of hydration per molecule or ion of salt in 

 solution, on the assumption that both ions and molecules hydrate, 



(W - W')m 

 ~ 18w(l+»^i») ; 



the number per ion, if ions only hydrate, 



= (W - W')m 

 J Snato ' 



the number per molecule, if molecules only hydrate, 



_ (W-W)m 

 18(1 -a)w " 



In the above formulae C is the observed elevation of the boiling-point constant, and 



C the theoretical value of the constant. 



i 



m — molecular weight of salt. 



W == weight of water used in an experiment in grammes. 

 W'= ,, ,, acting as solvent, in grammes. 



A E = increment of elevation due to A w grammes of salt added to the solvent or 



a solution. 

 A w = increment of salt added to solvent or solution. 



n = number of ions into which a molecule of salt dissociates. 

 a = Mv/m^ assumed to be the ionization coefficient, Avhere /j. v is the equivalent 

 conductivity at the concentration l/v, and // x the equivalent con- 

 ductivity at infinite dilution, each at 99 '4° Centigrade. 



Freezing-point calculations were made by the use of the formula 



K= mM ±- (1) 



W(l+«-l a ) v 



when K is the value of the depression constant, and A the observed depression. The 



other symbols have the same meaning as given above. 



From (1) the various expressions for calculating the amount of hydration may 



easily be deduced ; and they correspond with those already given above in the 



case of the boiling point for the calculation of boiling-point hydration data. When 



