ge in opposite directions is assumed to be equal, then
the product of the concentrations of the substances entering into
the reaction stands in a constant ratio to the product of the
concentrations of the resulting substances, as given in the expression
above for the solutions of acetic acid. This principle is called the
!Law of Mass Action!.

It should be borne in mind that the expression above for acetic acid
applies to a wide range of dilutions, provided the temperature remains
constant. If the temperature changes the value of the constant changes
somewhat, but is again uniform for different dilutions at that
temperature. The following data are given for temperatures of about
18 deg.C.[1]

==========================================================================
| | | |
MOLAL | FRACTION | MOLAL CONCENTRA- | MOLAL CONCENTRA- | VALUE OF
CONCENTRATION | IONIZED | TION OF H^{+} AND| TION OF UNDIS- | CONSTANT
CONSTANT | | ACETATE^{-} IONS | SOCIATED ACID |
______________|__________|__________________|__________________|__________
| | | |
1.0 | .004 | .004 | .996 | .0000161
| | | |
0.1 | .013 | .0013 | .0987 | .0000171
| | | |
0.01 | .0407 | .000407 | .009593 | .0000172
| | | |
===========================================================================

[Footnote 1: Alexander Smith, !General Inorganic Chemistry!, p. 579.]

The molal concentrations given in the table refer to fractions of a
gram-molecule per liter of the undissociated acid, and to fractions of
the corresponding quantities of H^{+} and C_{2}H_{3}O_{2}^{-} ions
per liter which would result from the complete dissociation of a
gram-molecule of acetic acid. The values calculated for the constant
are subject to some variation on account of experimental errors in
determining the percentage ionized in each case, but the approximate
agreement between the values found for molal and centimolal (one
hundredfold dilution) is significant.

The figures given also illustrate the general principle, that the
!relative! ionization of an electrolyte increases wi