TO THEIR STATE OF IONIZATION—MACGREGOR. 22 
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. (8) 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 /’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, ete., the value of 
a property, according to the conception under consideration, 
will be :— 
P=P_ +k, (1-,) ny +l,a, ny +k, (1-4) 2g +l,agngt&e., . (2) 
the n’s being numbers of gramme-equivalents per unit volume 
o the solution. If the solution have been formed by the 
mixture of the volumes v, and v2 of two simple solutions 
of salts, having one ion in common, for which, before the mix- 
ing, the property had the values :— 
P,=P,,+k, d—a,)n, ene (3) 
P,=P,,+k, 1-4.) n2+l,agne, 
then, since on mixing, the state of ionization will, in general, 
