C

NAPHTHALENE  ,oH8, a hydrocarbon discovered in the " carbolic " and " heavy oil " fractions of the coal-tar distillate (see COAL-TAR) in 1819 by A . Garden . It is a product of the action of heat on many organic compounds, being formed when the vapours of ether, camphor, acetic acid, ethylene, acetylene,, &c., are passed through a red-hot tube (M . Berthelot, Jahresb., 1851), or when petroleum is led through a red-hot tube packed with charcoal (A . Letny, Ber., 1878, II, p . 1210) . It may be synthesized by passing the vapour of phenyl butylene bromide over heated soda lime (B . Aronheim, Ann., 1874, 171, p . 219); and by the action of ortho-xylylene bromide on sodium ethane tetracarboxylic ester, the resulting tetra-hydronaphthalene tetracarboxylic ester being hydrolysed and heated, when it yields hydronaphthalene dicarboxylic acid, the silver salt of which decomposes on distillation into naphthalene and other products (A. v . Baeyer and W . H . Perkin, junr., Ber., 1884, 17, P .

451):

C6H4<CH2Br+Na•C(CO2R)2 C6Ha ~•CHCH2•C2•C(CO(CO22RH)2 )2 CioH8 C6H9`CHCH22•CH H•C0CO22HH C6H4`CH2•C(CO2H)2 " Nape," the back of the neck, is of doubtful origin; it may be a variant of " knap," a knob or protuberance . It is a colourless solid, which melts at 8o° C., and boils at 218° C . It crystallizes in the monoclinic system; it is to be noted that a- and /3-naphthol assume almost identical forms, so that these three compounds have been called isomorphous . It is insoluble in water, but is readily soluble in alcohol, and ether . It has a characteristic smell, and is very volatile, distilling readily in a current of steam . It acts as a weak antiseptic . It is used for enriching coal gas, as a vermin killer, in the manufacture of certain azo dyes, and in the preparation of phthalic acid (q.v.) . When passed through a red-hot tube packed with carbon it yields f3/3-dinaphthyl, (C10H7)2 . It forms a crystalline compound with picric acid . It readily forms addition products with chlorine and with hydrogen; the dichloride, CIOH8C12, is obtained as a yellow liquid by acting with hydrochloric acid and potassium chlorate; the solid tetrachloride, Clo Ha C14, results when chlorine is passed into naphthalene dissolved in chloroform . Numerous hydrides are known; heated with red phosphorus and hydriodic acid the hydrocarbon yields mixtures of hydrides of composition Clotho to C1oH2o . Sodium in boiling ethyl alcohol gives the a-dihydride, CloHlo (E .

Bamberger, Ber., 1887, 20, p . 1705); and with boiling amyl alcohol the (3-tetrahydride, CIOH12 (E . Bamberger, Ber., 189o, 23, p . 1561) . The a-tetrahydronaphthalene is formed when naphthalene is heated with phosphonium iodide at 170°-190° (A. v . Baeyer) .