Impurities of Commercial Nitric Acid.—These are principally chlorine and sulphuric acid; also peroxide of nitrogen, which tinges the acid yellow, as already described. Chlorine is detected by diluting the acid with an equal bulk of distilled water, and adding a few drops of nitrate of silver,—a milkiness, which is chloride of silver in suspension, indicates the presence of chlorine. In testing for sulphuric acid, dilute the nitric acid as before, and drop in a single drop of solution of chloride of barium; if sulphuric acid be present, an insoluble precipitate of sulphate of baryta will be formed.
Nitrous Acid. (See [Silver, Nitrate of.])
Nitrate of Potash.
Symbol, KO NO{5}. Atomic weight, 102.
This salt, also termed nitre or saltpetre, is an abundant natural product, found effloresced upon the soil in certain parts of the East Indies. It is also produced artificially in what are called nitre-beds.
Nitrate of potash is an anhydrous salt,—it contains simply nitric acid and potash, without any water of crystallization; still, in many cases, a little water is retained mechanically between the interstices of the crystals, and therefore it is better to dry before use. This may be done by laying it in a state of fine powder upon blotting-paper, close to a fire, or upon a heated metallic plate.
Symbol, BaO NO{5}. Atomic weight, 131.
Nitrate of baryta forms octahedral crystals, which are anhydrous. It is considerably less soluble than the chloride of barium, requiring 12 parts of cold and 4 of boiling water for solution. It may be substituted for the nitrate of lead in the preparation of protonitrate of iron.
Nitrate of Lead.