PHENYL, AND THE PirENvr.Ltc Guour. Phenyl is an organic radical, which has not yet been isolated. Its most important compounds are: (I.) carbolic or pheuic acid (HO,C,2140), known also as phenyl, hydrated oxide of phenyl, and phenyl alcohol. See CARBOLIC ACID. (2.) Hydride of phenyl known also as ben zo]e, benzine, and phene. See BENZOLE. (3.) Phenylamine or phenylia or better known under the name of aniline, one of the most important of the artificially formed bases.
Aniline derives its name from will, an obsolete name for indigo, which is one of the sources from which it is most readily procured. It exists amongst the products of the distillation of coal, and probably other organic compounds, but is always obtained by the. manufacturing chemist either from indigo or from nitro-benzole. Dr. Hofmann, to whom we are mainly indebted for our knowledge of the chemistry of this substance, gives the following directions for obtaining it from indigo: " Powdered indigo boiled with a highly concentrated solution of hydrate of potassa, dissolves with evolution of drogen gas to a brownish-red liquid, containing a peculiar acid, called the arithranille acid. If this matter be transferred to a retort, and still further heated, it swells up, and disengages aniline, which condenses in the form of oily drops in the neck of the retort and in the receiver. Separated groin the ammoniacal water by which it is accompanied and re-distilled, it is nearly colorless. The formation of aniline from indigo is represented by the following equation: Indigo. Hydrated Potassa. Aniline. Carbonate of Potassa.
Cial5NO2+ 4(K0,110)± 2110 = 411." By this process, the indigo is made to yield about one-fifth of its weight of pure ani line. Nitro-benzole is converted into aniline by the action of various reducing agents, such as hydrosulphate of ammonia, or acetate of protoxide of iron; and the distillation of one part of nitro benzoic, one part of acetic acid, and one and a half parts of iron filings, is regarded by Hofmann as the best means of preparing aniline, which is now required in large quantities for the dyers.
When pure," says Dr. Hofmann, " aniline forms a thin, oily, colorless liquid, of faint vinous odor, and aromatic burning taste. It is very volatile, but has nevertheless a high boiling-point, 359.6°. In the air it gradually becomes yellow or brown, and i acquires a resinous consistency. Its density is 1.028. It is destitute of alkaline reaction on test paper, but is remarkable for the number and beauty of the crystallizable com pounds it forms with acids. Two extraordinary reactions characterize this body;and distinguish it from all others—viz., that with chromic acid, and that with solution of hypoehlorite of lime. The former gives with aniline a deep greenish or bluish black precipitate; and the latter, an extremely beautiful violet-colored compound, the fine tint of which is, however, very soon destroyed." In the manufacture of aniline on a large
scale several bases having higher boiling points than aniline are formed. To one of these—a beautiful crystalline compound, represented by the formula C2411i4N2—the name of prim niii»e has been given, from its being isomeric with aniline. Aniline is a substance of the greatest. importance in theoretical organic chemistry, from the large number of derivatives and substitution products which it yields, and for the knowledge of which we are almost entirely indebted to Hofmann, whose investigations originally appeared in a series of papers in the Transactions of the Philosophical Society. These compounds are, however, for the most part of too complicated a nature to be noticed in these pages. Bat. independently of its theoretical importance, this substance has recently been extensively employed in the arts, a series of pigments of unequaled beauty having been obtained from it by the action of oxidizing agents. It is to Mr. W. Perkin that we are indebted for the idea of applying practically the property possessed by ani line of forming violet and blue solutions with chromic acid and with hypochloride of lime, to which we have already referred; and he succeeded in fixing these colors, and adapting them to the use of the dyer. The most important of these coloring matters are described in the article DYE-STUFFS (q.v.).
(4.) Trinitrophenic acid [HO,C12112(N04)30], in which three of the equivalents of the hydrogen of phenic acid•are replaced by three equivalents of the group, known as carbazotic acid (q.v.), and picric acid. In addition to the remarks contained in the article on CARHAZOTIC Acm, it may be noticed that while a solution of this acid com municates a bright yellow tint to animal textures, as the skin, wool, and silk, it has no such effect on tissues composed of vegetable fibers, such as cotton and linen, and hence it may be employed to ascertain whether the materials of any tissue belong to the animal or to the vegetable kingdom. A solution of a salt of this acid, when treated with indigo, yields a beautiful green color, which is employed in the manufacture of artificial flowers, and for various other purposes. In doses of 1 to 10 grains, it acts on rabbits as a strong poison, occasioning convulsions and speedy death. It has been prescribed in small doses, with moderate success, in cases of intermittent fever; but patients to whom it is given should he previously informed that it possesses the property of giving to the eye a yellow, and, as it were, a jaundiced appearance. All the sails of this acid ar;...‘ of a beautiful red or yellow tint, and most of them form brilliant crystals. When heated, or in some cases when only struck, they explode with considerable violence.