To prepare pure Nitrate of Silver from it, dissolve in Nitric Acid and evaporate until crystals are obtained. Then wash the crystals with a little dilute Nitric Acid, redissolve them in water, and crystallize by evaporation a second time. Lastly, fuse the product at a moderate heat, in order to expel the last traces of Nitric and Nitrous Acids. SILVER, AMMONIO-NITRATE OF. Crystallized Nitrate of Silver absorbs Ammoniacal gas rapidly, with production of heat sufficient to fuse the resulting compound, which is white, and consists of 100 parts of the Nitrate + 29·5 of Ammonia. The compound however which Photographers employ under the name of Ammonio-Nitrate of Silver may be viewed more simply as a solution of the Oxide of Silver in Ammonia, without reference to the Nitrate of Ammonia necessarily produced in the reaction. Very strong Ammonia, in acting upon Oxide of Silver, converts it into a black powder, termed _Fulminating Silver_, which possesses the most dangerous explosive properties. Its composition is uncertain. In preparing Ammonio-Nitrate of Silver by the common process, the Oxide first precipitated occasionally leaves a little black powder behind, on re-solution; this does not appear however, according to the observations of the Author, to be Fulminating Silver. In sensitizing salted paper by the Ammonio-Nitrate of Silver, _free Ammonia_ is necessarily formed. Thus-- Chloride of Ammonium + Oxide of Silver in Ammonia = Chloride of Silver + Ammonia + Water. SILVER, OXIDE OF. Symbol, AgO. Atomic weight, 116. This compound has already been described in Part I., page 17. SILVER, CHLORIDE OF. Symbol, AgCl. Atomic weight, 144. The preparation and properties of Chloride of Silver are given in Part I. page 14. SILVER, BROMIDE OF. Symbol, AgBr. Atomic weight, 186. See Part I. page 17. SILVER, CITRATE OF. _See_ Citric Acid. SILVER, IODIDE OF. Symbol, AgI. Atomic weight, 234. See Part I. page 16. SILVER, FLUORIDE OF. Symbol, AgF. Atomic weight, 127. This compound differs from those last described in being soluble in water. The dry salt fuses on being heated, and is reduced by a higher temperature, or by exposure to light. SILVER, SULPHURET OF. Symbol, AgS. Atomic weight, 124. This compound is formed by the action of Sulphur upon metallic Silver, or of Sulphuretted Hydrogen or Hydrosulphate of Ammonia upon the Silver salts; the decomposition of Hyposulphite of Silver also furnishes the black Sulphuret. Sulphuret of Silver is insoluble in water, and nearly so in those substances which dissolve the Chloride, Bromide, and Iodide, such as Ammonia, Hyposulphites, Cyanides, etc.; but it dissolves in Nitric Acid, being converted into soluble Sulphate and Nitrate of Silver. (For a further account of the properties of the Sulphuret of Silver, see page 146.) SILVER, NITRATE OF. Symbol, AgO NO{5}. Atomic weight, 170. The preparation and properties of this salt have been explained at pages 12 and 362.