464: NITRATES NITRIC ACID Hamilton of St. Augustine, 111. ("American Journal of Medical Sciences," Oct. 1, 1865), recommends it to prevent pitting in smallpox. 7. Nitrate of Cobalt, or Gobaltous Nitrate (Co2NO 3 ,6H 2 O), is prepared by dissolving the oxide in nitric acid. It forms pinkish red, prismatic, deliquescent crystals of specific grav- ity 1*83. It is often employed as a reagent for the blowpipe, magnesium compounds yielding a pink-colored mass, those of zinc green, and those of aluminum blue. Adding a concen- trated solution of potassic nitrate to a solution of cobaltous nitrate, acidulated with nitric or acetic acid, throws down a beautiful orange- yellow precipitate, consisting of microscopic four-sided prisms, with pyramidal summits. Cobalt in nickel may be discovered by its means. 8. Nitrate of Copper, or Cupric Ni- trate (Cu2NO 3 ,6H 3 O), is made by dissolving copper in slightly diluted nitric acid. During the operation nitric oxide gas (NO) is copiously given off, 3Cu + 8HNO 3 , yielding 3(Cu2N0 3 ) + 2NO+4H a O. Concentrated acid yields perox- ide of nitrogen (NO 2 ). Cupric nitrate is a beau- tiful blue, highly deliquescent salt, crystallizing in rhomboidal prisms. At temperatures above 59 F., it crystallizes with 3H a O in needles of specific gravity 2 '047, which are very soluble in alcohol. Moderate heat converts it into insoluble basic nitrate, Cu2No3,3CuH 3 Oa. A further heat expels all the acid, leaving black oxide. Cnpric nitrate is used in medicine as an application to sloughing ulcers. If the crystals are folded in tin foil, they will act so powerfully upon the metal as to emit sparks, the tin being converted into stannic oxide. 9. Nitrates of Iron. These are commonly known as the protonitrate and the pernitrate ; in the new nomenclature they are known respectively as ferrous nitrate and ferric nitrate. The fer- rous nitrate may be formed by digesting iron turnings in very dilute nitric acid, and also by dissolving protosulphide of iron in cold dilute nitric acid of specific gravity less than 1'12. It crystallizes in pale green rhombohedrons, having the formula Fe2NO 3 ,6H,O. This salt is used in dyeing. The pernitrate or ferric nitrate is prepared by digesting metallic iron in nitric acid of specific gravity from ri2 to 1'3. A solution of it is used as an astringent and tonic in medicine, and as a lotion in sur- gery, under the name of liquor ferri nitratis (United States Pharmacopoeia). 10. Nitrates of Lead. Lead forms several salts with nitric acid, the principal of which are plumbic ni- trate (Pb2N0 3 ) and dibasic plumbic nitrate (Pb2N0 3 ,PbH 2 2 ). The first is formed by dissolving metallic lead or plumbic oxide (lith- arge, PbO) in an excess of slightly diluted nitric acid. It crystallizes in regular anhydrous octa- hedra, generally opaque. A dull red heat re- duces it to protoxide, with evolution of oxygen and nitric peroxide. Caustic ammonia added to eicess of the nitrate forms the dibasic salt. The nitrate of lead is used in chemistry in pre- paring other lead compounds, as for instance the iodide, which is done by the double decom- position of this salt with iodide of potassium. It is also used as a reagent in the laboratory. In medicine it is employed as an application to excoriated surfaces, and its solution forms Ledoyen's disinfecting fluid. 11. Nitrates of Mercury. Mercury forms a greater number of nitrates than any other metal. Among them are the normal subnitrate, or mercurous ni- trate, and the normal mercuric nitrate, the latter of which is used in medicine. The liquor Jiydrargyri nitratis is extensively used in the London hospitals for cutaneous diseases, and it has been employed as an application in boils, carbuncles, acne, lupus, and sloughing ulcers. In treating boils a full-sized drop of the liquor is applied to the apex of the furuncle. The unguentum hydrargyri nitratis forms the cit- rine ointment of the pharmacopeias, and is used as a stimulant and alterative application in various cutaneous affections, particularly of the scalp. All the other inorganic as well as organic nitrates of importance will be found under the heads of their bases. 12. Alcoholic Nitrates, or Nitric Ethers. When nitric acid is heated with alcohol, part of the alcohol is ox- idized, and the nitric acid is reduced to nitrous acid, which acting on the remainder of the alcohol produces nitrous ether and other bodies ; but if urea is added to the liquid, it immediately decomposes the nitrous acid, and nitrate of ethyl is formed. The other alcohol radicles may also be transformed by the action of nitric acid in the presence of urea into corresponding nitric ethers, as amyl nitric ether, methyl nitric ether, &c. They have some resemblance to the nitrous ethers. (See NITKITES.) NITRE. See NITRATES. NITRIC ACID, or Hydric Nitrate, the most im- portant compound of oxygen and nitrogen, formed by the union of nitric anhydride or anhydrous nitric acid (see NITEOGEN) and wa- ter. It was formerly called aqua fortis, and was known to the alchemists ; but its compo- sition was first determined by Cavendish in 1785. When nitrogen is mixed with about 12 times its volume of hydrogen, and a jet of the mixed gases is burned in the air or in oxy- gen, the water produced will be found to con- tain a small quantity of nitric acid ; and it was his experiments on the formation of water that led Cavendish to the discovery of the acid. If a number of electric sparks are passed be- tween two points over moistened litmus pa- per, a red spot will be produced on the paper from the action of nitric acid which has been formed by the combination of atmospheric ni- trogen and oxygen in the presence of watery vapor; and during a thunder storm the acid is produced in a similar manner in quantity sufficient to be detected by delicate tests. The formula of nitric acid is HNO 3 , and accord- ing to modern theory it is a compound of hy- drogen with a radicle called nitrion (NO S ), and is regarded as a salt of hydrogen. The nitrion is produced by the union of water with nitric
