The existence of a precipitate in contact with a solution is a question of a ‹condition› of ‹equilibrium›; the question raised, as the result of Haber's calculations, deals simply with the ‹problem of the path, the mechanism by which equilibrium is reached›, but the answer to it ‹does not affect the conditions, on which the maintenance of equilibrium depends›. All the conclusions, drawn in our discussions of precipitation from solutions of complex ions, are concerned with ‹final conditions for equilibrium›, ‹i.e.› with the conditions under which a ‹precipitate can exist›, and not with the mechanism of its formation. The conclusions reached are valid, therefore, irrespective of what the decision may ultimately be in the question, whether the simple ions alone are acted upon, when their salts are precipitated, or whether the complex ions are also immediately concerned in the action. The precipitation of silver chloride from an ammoniacal solution[473] may serve to illustrate this point. In the first place, the precipitation of silver chloride from an ammoniacal solution, say by sodium chloride, may be considered to be the result of the direct interaction of chloride ions with the small quantity of silver ions present, ‹the complex serving only to renew the supply of silver ions›, as the latter are removed from solution, by the precipitation. The course of the action would be expressed by the equations [Ag(NH_{3})_{2}]Cl ⇄ [Ag(NH_{3})_{2}^{+}] + Cl^{−} ⇄ 2 NH_{3} + Ag^{+} + Cl^{−} ⇄ AgCl + 2 NH_{3}. (1) AgCl ⇄ AgCl ↓ When the precipitation is ended and equilibrium established, a trace of silver chloride is in solution, in contact with the precipitate, and, according [p236] to the principle of the solubility-product, we must have [Ag^{+}] × [Cl^{−}] = K_{AgCl}. Bodländer's experiments,[474] on the solubility of silver chloride in ammonia, prove that this relation is in perfect agreement with the facts. For the silver-ammonium-ion, the free ammonia and the silver-ion present in the solution, we must have the relation [Ag^{+}] × [NH_{3}]^2 / [Ag(NH_{3})_{2}^{+}] = K_{Instab. Const.}. This relation, according to the experimental evidence, is also found to hold. Now, we might, on the other hand, assume that the primary or main action, leading to the precipitation of silver chloride, is the interaction of the chloride ions ‹with the complex ions›, rather than with silver ions. Silver-ammonium chloride, [Ag(NH_{3})_{2}]Cl, might first be formed, for instance, and then decompose ‹directly› into silver chloride and ammonia. This is the simplest assumption we can make for this kind of action and is sufficiently illustrative of any kind of direct action between the chloride ions and the complex ions. The path of the action would then be expressed by the equations [Ag(NH_{3})_{2}^{+}] + Cl^{−} ⇄ [Ag(NH_{3})_{2}]Cl ⇄ 2 NH_{3} + AgCl ⇄ 2 NH_{3} + Ag^{+} + Cl^{−}. (2)