TO THEIR STATE OF IONIZATION MACGREGOR. 227 



These constants are obtained from solutions of too great 

 concentration to be regarded as exact values. Nevertheless it 

 may be admissible, tentatively, at least, and so far as these two 

 salts are concerned, to draw the following conclusions : Undis- 

 sociated and dissociated molecules are nearly equally effective in 

 increasing the density, those dissociated, however, being some- 

 what the more effective of the two. (2) Undissociated molecules 

 diminish the thermal expansion, those dissociated increasing it to 

 a greater extent. (3) In the case of viscosity it is the undis- 

 sociated molecules which have the preponderating influence, 

 those dissociated having but a slight effect, which may be an 

 increasing or a diminishing effect. Thus Arrhenius's expecta- 

 tion that all dissociated ions would be found to diminish 

 viscosity seems to be only partially realized, though possibly 

 from observations on more dilute solutions, both Z's might be 

 found to be negative. (4) In the increase of surface-tension 

 the undissociated molecules have about twice as great an influ- 

 ence as the dissociated. (5) In increasing the refractive index 

 it is the dissociated molecules which have the preponderating 

 influence ; and their superiority is greater in increasing the 

 refractive power than increasing the density. 



MIXTURES OF SOLUTIONS. 



For a solution containing several salts, 1, 2, etc., the value of 

 a property, according to the conception under consideration, 

 will be : 



P = P w + k l (l-a l )n l + l l a l n l +k 2 (l-a 2 )n^ + l 2 a 2 n^+&c. ) . (2) 



the TI'S being numbers of gramme-equivalents per unit volume 

 o the solution. If the solution have been formed by the 

 mixture of the volumes Vi and Vz of two simple solutions 

 of salts, having one ion in common, for which, before the mix- 

 ing, the property had the values : 



then, since on mixing, the state of ionization will, in general, 



