In preparing chloride of silver by double decomposition, the white clotty masses which first form must be washed repeatedly with water, in order to free them from soluble nitrate of soda, the other product of the change. When this is done, the salt is in a pure state, and may be dried, etc., in the usual way. _Properties of Chloride of Silver._--Chloride of silver differs in appearance from the nitrate of silver. It is not met with in crystals, but forms a soft white powder resembling common chalk or whiting. It is tasteless and insoluble in water; unaffected by boiling with the strongest nitric acid, but sparingly dissolved by concentrated hydrochloric acid. Ammonia dissolves chloride of silver freely, as do solutions of hyposulphite of soda and cyanide of potassium. Concentrated solutions of alkaline chlorides, iodides, and bromides are likewise solvents of chloride of silver, but to a limited extent. Dry chloride of silver heated to redness fuses, and concretes on cooling into a tough and semi-transparent substance, which has been termed _horn silver_ or _luna cornea_. Placed in contact with metallic zinc or iron acidified with dilute sulphuric acid, chloride of silver is reduced to the metallic state, the chlorine passing to the other metal under the decomposing influence of the galvanic current which is established. _Preparation and properties of the Subchloride of Silver._--If a plate of polished silver be dipped in solution of perchloride of iron, or of bichloride of mercury, a _black stain_ is produced, the iron or mercury salt losing a portion of chlorine, which passes to the silver and converts it superficially into subchloride of silver. This compound differs from the white chloride of silver in containing less chlorine and more of the metallic element; the composition of the latter being represented by the formula AgCl, that of the former may perhaps be written as Ag{2}Cl. (?) Subchloride of silver is interesting to the photographer as corresponding in properties and composition with the ordinary chloride of silver blackened by light. It is a pulverulent substance of a bluish-black color, which is decomposed by ammonia, hyposulphite of soda, and cyanide of potassium, into chloride of silver which dissolves, and insoluble metallic silver. Silver, Bromide of. Symbol, AgBr. Atomic weight, 186. This substance so closely resembles the corresponding salts containing, chlorine and iodine, that a short notice of it will suffice. Bromide of silver is prepared by exposing a silvered plate to the vapor of bromine, or by adding solution of bromide of potassium to nitrate of silver. It is an insoluble substance, slightly yellow in color, and distinguished from iodide of silver by dissolving in strong ammonia and in chloride of ammonium. It is freely soluble in hyposulphite of soda and in cyanide of potassium. Silver, Citrate of. (_See_ Citric Acid.) Silver, Iodide of. Symbol, AgI. Atomic weight, 234.