The silver voltameter. Part III.―The solvent properties of silver nitrate solutions

Abstract

In an earlier paper by Mr. F. E. Smith and a second paper by the author in conjunction with Mr. F. E. Smith it was shown that the weight of silver deposited by a given current was influenced in a very important degree by impurities in the silver nitrate solutions. The most important impurities are those which are capable of exerting a reducing action upon the silver nitrate. But there is also a group of substances to be considered which are soluble in silver nitrate solutions, though almost insoluble in water: these are precipitated when the silver nitrate solutions are impoverished at the cathode by the passage of the current and cause an appreciable increase in the weight of the deposit. They may be removed by diluting the silver nitrate solutions, filtering off the precipitation will be freely soluble in the concentrated mother-liquor from which the crystals have separated, and may be got rid of the usual way by draining on the pump and rinsing cautiously with water. In view of the importance of these impurities in the experimental determination of the electrochemical equivalent of silver, and the interest of the problem from the standpoint of the theory of solutions, it appeared to be desirable to pursue the matter further and to make quantitative measurements of the solvent properties of silver nitrate solutions for some typical substances which are insoluble, or nearly so, in pure water. The present paper includes measurements of the solubility of silver chloride, bromide, iodide, and sulphide. The solubility of the iodide has already been investigated somewhat fully by Hellwig, but only a few incidental measurements have been made in the case of the other salts.