Naphthaline (dolls), a hydrocarbon obtained from the distillation of numerous organic bodies, such as coal, wood, resin, oils, and animal substances; also by conducting the vapor of acetic acid, alcohol, ether, volatile oils, and camphor through red-hot tubes. It has been prepared by the passage through hot tubes of ethylene, marsh gas, and other hydrocarbons, as well as of a mixture of benzole and ethylene, sulphuretted hydrogen and disulphide of carbon, hydrogen, and the vapors of chloride of carbon. In general we can say that naphthaline is the product of the decomposition of organic matter at a red heat, just as the oxidation of the same bodies yields oxalic acid. Warren and Storer found naphthaline as a native product in the petroleum of Bur-mah. It was first noticed by Garden in 1820, was observed about the same time by Reichen-bach, and fully analyzed and its true chemical composition determined by Faraday. The most laborious researches upon it were made by Laurent, who was engaged for 20 years in the study of the substitution products of this interesting body. - The raw material usually employed in the preparation of naphthaline is coal tar, and the method recommended by Vohl is as follows: The dead oil is run into vats, and left in a cool place for six to eight days, when crystals of naphthaline are formed.
The liquid portion is then drawn off, the crystalline mass stirred up to a pap by a pestle, the adhering oil removed in a centrifugal machine, and the mass finally placed under a hydraulic press. The press cake is then transferred to an iron vessel provided with a steam coil and a stirrer, so arranged that it can be operated when the vessel is closed. The fused mass is then well mixed with a few per cent, of caustic soda, the lye run off, and the operation repeated three times, and finally washed with hot water until no further reaction can be perceived. In this manner all of the carbolic acid, creosote, resinous matter, and other impurities are removed. The still fluid, naphthaline is then intimately mixed with a few per cent, of sulphuric acid of 45° B., the acid let off, washed out with water, and the contents of the vessel agitated with strong caustic soda and left for two or three hours to subside, at a temperature of 100° C. The naphthaline thus treated is further purified by distillation over a free fire from cast-iron stills capable of holding a ton. At first naphthaline mixed with water passes over, but at 210° C. pure naphthaline distils, and so rapidly that 100 lbs. can be obtained in 20 minutes.
The naphthaline vapors are condensed in water at 80° C. in closed vessels placed in water baths, also kept at 80°. The pure naphthaline obtained in this way is run into conical glass, metal, or moistened wooden moulds, from the sides of which it separates by contraction on cooling, and is introduced into commerce in sticks like brimstone. Naphthaline, when pure, has the form of brilliant white, scaly, rhombic plates of peculiar odor, having a specific gravity of 1.151, according to Vohl; a melting point, according to Kopp, of 79.2° C.; and a boiling point of 216.4° to 216.8° C. It is in small quantities volatile at lower temperatures, and goes over copiously with steam. It possesses at first a weak, subsequently a burning taste; is insoluble in cold, very slightly in hot water; easily soluble in warm alcohol, ether, benzole, turpentine, volatile and fatty oils, and in acetic and oxalic acids. According to Vohl, the fused naphthaline absorbs air in the same manner as molten silver, which is richer in oxygen than the atmosphere, and gives it up again on cooling.
Naphthaline dissolves indigo, phosphorus, sulphur, succinic, benzoic, and oxalic acids, chloride of mercury, and the sulphides of:' arsenic, tin, and antynony, which on cooling usually separate in a crystalline condition. Caustic potash and dilute sulphuric acid do not act on naphthaline, but chlorine, bromine, nitric acid, and concentrated sulphuric acid readily attack it. It crackles in the hand like sulphur, and becomes negatively electric when rubbed with silk. It is destructive to moths, and is used as a substitute for camphor in the protection of woollens, plants, and objects of natural history. When burned in its pure state it gives rise to copious clouds of fine lampblack. - The researches of Laurent have shown the existence of a numerous series of substitution compounds, in which chlorine and bromine take the place of the hydrogen element, and sometimes replace each other. The bodies so formed are not of much practical importance, but their investigation has had a remarkable influence upon the recent progress of organic chemistry.
A table of a few of these compounds will serve to illustrate the manner of substitution:
................C10 H7 Br
C10 H7 Cl2
Naphthalic or phthalic acid, made by the oxidation of naphthaline by sulphuric acid and black oxide of manganese, can be converted into benzoic acid, benzole, nitro-benzole, and finally into aniline; and in this way naphthaline is one of the sources of aniline colors. Magdala red is a dye prepared by the action of nitrous acid on naphthylamine, which in turn is derived from naphthaline. Naphthaline yellow is made by digesting 100 parts of naphthaline for a few hours in a mixture of 200 parts of water and 20 parts of nitric acid, and dissolving the resulting crystals in ammoniacal water. Kopp's brown is produced by boiling nitro-naphthaline with sulphuric acid. Other compounds are naphthazarine, similar to alizarine, called also dianthine; naphthylamine, one of the most interesting; Perkins's violet; naphthaline alcohol, or naphthoie; Hoffmann's naphthaline red; naphthyl-rosaniline; and numerous others.