_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, Nitrite 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. The properties of Nitrate of Potash are described as far as necessary at page 190. NITRATE OF BARYTA. 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. Symbol, PbO NO{5}. Atomic weight, 166. Nitrate of Lead is obtained by dissolving the metal, or the Oxide of Lead, in _excess_ of Nitric Acid, diluted with 2 parts of water. It crystallizes on evaporation in white anhydrous tetrahedra and octahedra, which are hard, and decrepitate on being heated; they are soluble in 8 parts of water at 60°. Nitrate of Lead forms with Sulphuric Acid, or soluble Sulphates, a white precipitate, which is the insoluble Sulphate of Lead. The _Iodide_ of Lead is also very sparingly soluble in water. NITRATE OF SILVER, _See_ Silver, Nitrate or. NITRO-GLUCOSE. When 3 fluid ounces of cold Nitro-Sulphuric Acid, consisting of 2 ounces of Oil of Vitriol and 1 ounce of highly concentrated Nitric Acid, are mixed with 1 ounce of finely powdered Cane Sugar, there is formed at first a thin, transparent, pasty mass. If it is stirred with a glass rod for a few minutes without interruption, the paste coagulates as it were, and separates from the liquid as a thick tenacious mass, aggregating into lumps, which can easily be removed from the acid mixture. This substance has a very acid and intensely bitter taste. Kneaded in warm water until the latter no longer reddens litmus-paper, it acquires a silver colour and a beautiful silky lustre. It may be used in Photography to confer intensity upon newly mixed Collodion; but is inferior to Glycyrrhizine employed for the same purpose. NITRO-HYDROCHLORIC ACID. Symbol, NO{4} + Cl.