Page:Outlines of Physical Chemistry - 1899.djvu/275

 evidently not be modified. The concentration of the

unitary molecules C 2 H 4 2 and of the HOH molecules will

be reduced to a fifth, that of the unitary molecules

.1.

C2H 3 2 Na and of the NaOH to four-fifths of the original value. Now the equations

°T = W 'T

show that the acetic acid and the sodium acetate continue to be in equilibrium with their products of hydrolytic decomposition. There is, therefore, neither any further dissociation nor a reunion of the dissociated molecules, and the electric conductivity of the mixed solution will be equal to i that of the acetic acid solution plus £ that of the sodium acetate solution. It is evident that, instead of taking 4 litres of the sodium acetate solution, we might have taken any amount of ifc and we should always arrive at an analogous result.

By the mixture of heterohydric solutions (in which

u x %Wi) 9 the equilibria are disturbed and reactions take place. The reader may easily be convinced of this by following an example.

Two acid solutions are isohydric when the molecules + HOH contained in them have the same concentration.

It is now expedient to apply ourselves to a practical example, and ascertain the degree of dilution of a hydro- chloric acid solution which would be isohydric with a solu- tion of one equivalent of acetic acid in 8 litres of water. For this acetic acid solution the degree of dissociation is 0;0119 (page 255) : in 1 litre there is, therefore,

°' 0119 = 0-0015 equivalent

s

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