«The Reacting Components in Solutions of the Complex Cyanide Ions.»—The extraordinary values, obtained for the constants expressing the condition of equilibrium between cyanide ions and some of the simple metal ions, such as gold and silver ions, and their complex ions, have led to inquiries concerning a question of fundamental interest in the theory of complex ions and in the theory of ionization itself. In a 0.05 molar solution of KAg(CN)_{2}, containing an excess of 0.1 mole of CN^{−}, per liter, the concentration of silver-ion is only 5E−21. And yet, the addition of potassium hydrosulphide (sufficient to make [KSH] = 0.1 molar) will precipitate silver sulphide practically instantaneously from the solution.[464] In solutions containing a larger excess of cyanide, the concentration of the silver-ion is enormously reduced, and yet, while we can no longer precipitate silver sulphide from such a solution, metallic silver may be precipitated by zinc or by the action of an electric potential at the cathode (Chapter XV). The question may be asked, ‹whether we must consider that in these actions the minute quantity of free silver ions, present at any moment, is alone capable of the reactions› indicated, and that the ‹decomposition of the complex› into its ‹components›—as one of these, the silver-ion, is removed by precipitation—takes place with ‹sufficient speed› to account for the ‹rapid actions, wholly, as direct actions of the silver ions›. The alternative to an affirmative answer to this question is, that silver sulphide or silver ‹may be precipitated by direct action of the precipitant› on the ‹complex› ions, rather than on the ‹silver ions›. We may indicate the first course suggested for the action, as follows: 2 Ag(CN)_{2}^{−} + S^{2−} ⇄ 4 CN^{−} + 2 Ag^{+} + S^{2−} ⇄ Ag_{2}S ↓ + 4 CN^{−}. I The second, suggested, course of the action would be the following: 2 Ag(CN)_{2}^{−} + S^{2−} ⇄ Ag_{2}S ↓ + 4 CN^{−}. II This second action would mean that we could obtain reactions of silver ions, such as the precipitation of silver sulphide, ‹without the intermediate formation of the free ions themselves›. The consequences of the first, the ordinary, conception of such actions ‹as direct actions of silver ions›, have been analyzed by Haber[465] from the point of view of the velocities of the actions, by which the complex must be formed from its components and be decomposed into them, in order to satisfy the facts concerning the precipitations. [p233]