[215] The most reliable estimates of the concentrations of ions in these solutions are based on determinations of the degrees of ionization by means of conductivity measurements (see Chap. IV, and the previous footnote).
[216] Salts MeX ionize more readily (80–85% in 0.1 molar solution) than do salts Me″X2 or Me2X″ (50 to 70% in 0.1 molar solution), and these, again, more readily than salts Me″X″ (about 40% in 0.1 molar solution).
[217] The calculation of the condition of equilibrium can be made, with sufficient accuracy for our purpose, as follows: The denominator 0.9958 in the original proportion, being near its limit (its highest possible value is 1 in a molar solution), cannot change appreciably. Consequently, when the one factor in the numerator, [CH3CO2−], is made 0.53 / 0.0042, or 126 times as large as it was, the other factor, [H+], to maintain a constant proportion, must be made 1 / 126th of its original value and 0.0042 / 126 = 0.000,034. For more exact work, the new concentrations of the three components may be found by solving a simple quadratic equation.
[218] Küster, Z. für Elektrochem., 4, 110 (1897).
[220] See Part III for the application of this principle to ammonium hydroxide and its experimental confirmation. (Cf. Arrhenius, Z. phys. Chem., 2, 28 (1888); Stieglitz, Am. Chem. J., 23, 406 (1900).)
[221] For instance, in the first place, the action of 0.1 mole of HCl on 0.1 mole of C2H3O2Na, dissolved in a liter of water, and, in the second place, the action of 0.1 mole of NaOH on 0.1 mole of NH4Cl, in a liter of water, may be considered. The strong electrolytes (HCl, C2H3O2Na, NaCl, NH4Cl, NaOH) may be taken to be (roughly) 80% ionized. From the concentrations given and the constants involved, the direction and the presumable intensity of the main change in each of the two cases should be determined.
[222] Instances of such displacement are given in the footnote of the previous paragraph.
[223] E.g. 50 c.c. of 0.2 molar solutions.
[224] Mercuric cyanide and mercuric chloride are largely present in aqueous solution as [Hg(CN)2]2 and [HgCl2]2; see Chap. XII.