The Elements of Qualitative Chemical Analysis, vol. 1, parts 1 and 2. / With Special Consideration of the Application of the Laws of Equilibrium and of the Modern Theories of Solution.

by Julius Stieglitz

[175] Van 't Hoff, loc. cit., I, 104, 159, etc.

[176] In regard to the variations of the equilibrium constant with changes of temperature and the relations which govern these changes see Smith's Inorganic Chemistry (1909), p. 260.

[177] The limitations are indicated in the preceding section.

[178] Stieglitz, Am. Chem. J., 23, 406 (1900).

[179] Vide Stieglitz, loc. cit.

[180] The table is based on the results of Noyes and Cooper, given in "The Electrical Conductivity of Aqueous Solutions," Carnegie Institution Publications, No. 63, pp. 138, 141 (1907).

[181] Ostwald [Z. phys. Chem., 2, 278 (1888)], was the first to develop this relation from the conductivity data for so-called "weak acids," and the law of chemical equilibrium, holding in such and similar cases, is often called Ostwald's Law of Dilution.

[182] The equilibrium ratio, used as an illustration in the text, is the equilibrium ratio for monobasic acids. For polybasic acids, the ratio would have the form demanded by the rule given p. [94]. For instance, for H₂X ⇄ 2 H⁺ + X²⁻, the expression [H⁺]² × [X²⁻] / [H₂X] should be constant, provided the ionization occurs according to the law of chemical equilibrium in its simplest terms. In point of fact, for strong acids, this ratio holds as little as does the equilibrium ratio for the monobasic acids.

[183] Owing to the instability of carbonic acid, which breaks down into carbon dioxide and water (H₂CO₃ ⇄ H₂O + CO₂), the carbonic acid is, in turn, in equilibrium with the carbon dioxide. For the sake of simplicity, this relation is not included in the detailed discussion, and wherever the symbols H₂CO₃ and [H₂CO₃] are used, they are intended to represent the total carbonic acid, present as such and as carbon dioxide. The detailed discussion of the complication mentioned will be given in connection with the analogous case of ammonium hydroxide and ammonia, and, as will be shown there, with the significance just attached to the symbols, the relations developed in the text are a rigorous expression of the facts.

[184] [H⁺], in all the equations used, represents as usual, the total concentration of hydrogen-ion.