Nitrite of Silver is a compound of Nitrous Acid, or NO3, with Oxide of Silver. It is formed by heating Nitrate of Silver, so as to drive off a portion of its Oxygen, or more conveniently, by mixing Nitrate of Silver and Nitrite of Potash in equal parts, fusing strongly, and dissolving in a small quantity of boiling water: on cooling, the Nitrite crystallizes out, and may be purified by pressing in blotting-paper. Mr. Hadow describes an economical method of preparing Nitrite of Silver in quantity, viz. by heating 1 part of Starch in 8 of Nitric Acid of 1·25 specific gravity, and conducting the evolved gases into a solution of pure Carbonate of Soda until effervescence has ceased. The Nitrite of Soda thus formed is afterwards added to Nitrate of Silver in the usual way.
Properties.—Nitrite of Silver is soluble in 120 parts of cold water; easily soluble in boiling water, and crystallizes, on cooling, in long slender needles. It has a certain degree of affinity for Oxygen, and tends to pass into the condition of Nitrate of Silver; but it is probable that its Photographic properties depend more upon a decomposition of the salt and liberation of Nitrous Acid.
Properties of Nitrous Acid.—This substance possesses very feeble acid properties, its salts being decomposed even by Acetic Acid. It is an unstable body, and splits up, in contact with water, into Binoxide of Nitrogen and Nitric Acid. The Peroxide of Nitrogen, NO4, is also decomposed by water, and yields the same products.
Symbol, AgO (C4H3O3). Atomic weight, 167.
This is a difficultly soluble salt, deposited in lamellar crystals when an Acetate is added to a strong solution of Nitrate of Silver. If Acetic Acid be used in place of an Acetate, the Acetate of Silver does not fall so readily, since the Nitric Acid which would then be liberated impedes the decomposition. Its properties have been sufficiently described at [page 89].
Symbol, AgO S2O2. Atomic weight, 164.
This salt is fully described in Part I. [page 129]. For the properties of the soluble double salt of Hyposulphite of Silver and Hyposulphite of Soda, see [page 43].