Although silver chloride has been used in many precise analytical researches, certain of its properties, upon which the accuracy of the work depends, have remained undesirably obscure. One of these properties, the solubility, has occasioned frequent comment regarding its anomalous character. Incidental to some recent work in this Laboratory, some of the facts underlying the anomalous behavior of silver chloride have been found. It is the purpose of the work described in this paper to supplement these findings.Reagents.-The reagents used in the experiments described in this report were purified by the methods employed in atomic weight determinations. Silver, ammonia, hydrochloric acid, nitric acid and sodium chloride were prepared by methods previously outlined.2 The purification of the ammonium, potassium and silver nitrate reagents has also been described.8 All water, nitric acid, ammonium nitrate and potassium nitrate were tested to ensure the absence of silver and chloride impurities.Three specimens of silver chloride were used. Specimen No. 1 was prepared by adding a liter of 0.1 M silver nitrate solution drop by drop to a liter portion of hydrochloric acid containing a 3% deficiency of HC1. Both solutions were 0.3 M in nitric acid. The precipitate was washed sixteen times over a period of a month with 250-cc. portions of water, in a glass-stoppered Pyrex bottle. After further washing with 0.3M nitric acid, the specimen remained in contact with a liter of this acid for about three months. Tests made upon the supernatant liquid showed that it contained substantially equivalent amounts of silver and chloride during this period. The silver chloride was then washed free of acid with a total of six 1600-cc. portions of water, over a period of several months. Immediately before the treatment described below it was again washed with six 250-cc. portions of water. Under themicroscope, samples of this specimen appeared as clusters of uniform grains about 0.005 mm. in diameter. Specimen No. 2, another equal quantity of silver chloride, was prepared and tested in the same manner as Specimen No. 1, with the same result. However, in this case the nitric acid solution left in contact with the material was 0.1 M in ammonium nitrate.When the tests were completed, the specimen was washed free of extra electrolytes with six 1600-cc. portions of water, over a period of several months. It was next dissolved in aqua ammonia (prepared by distillation in an all-Pyrex system) and reprecipitated by slow evaporation of the solution. The resulting precipitate was washed with 0.3 M nitric acid, then with six 250-cc. portions of water. This preparation consisted of coarse crystals approximately 100 times larger, on the average, than the particles of Specimen No. 1, and much less uniform in size and shape. Specimen No. 3, a slightly larger quantity of material, was prepared in the same general manner as the other specimens, but with silver and chloride from another source. After a thorough washing with water, the material was used in expe...