THE HYDROCARBONS AND THEIR DERIVATIVES. FLAME 353 



The hydrocarbons of the benzene series exhibit, in fact, many of 

 the properties of defines, combining directly with hydrogen and 

 with the halogens to form saturated compounds such as hexa- 

 hydrobenzene CeHi2 and benzene hexabromide CeHeBre. 



The second member of the aromatic series is toluene C 6 H 5 .CH 3 . 

 The third is xylene C 6 H4.(CH 3 )2. Naphthalene Ci H 8 and anthra- 

 cene CuHio are members of more complex series, containing more 

 than one ring. 



Of all hydrocarbons, those of the aromatic series, with their 

 derivatives, are the most important. They are of particular 

 significance in the dye-stuff and explosive industries, and in the 

 manufacture of synthetic perfumes and drugs. They give alde- 

 hydes, acids, esters, etc., similar to those listed under the paraffin 

 hydrocarbons (pp. 347-50). In addition to these, the following 

 extremely valuable classes of derivatives should be noted : 



(1). Phenols. The substitution of hydroxyl for a hydrogen 

 atom in benzeae' gives phenol C 6 H 5 OH, a substance quite different 

 in many'of its properties from an alcohol, although it resembles 

 the alcohols in forming esters with acids (see p. 349). Phenol, 

 when pure, is a colorless solid melting around 40, with a charac- 

 teristic odor. It is strongly antiseptic, corrosive and poisonous. 

 In solution it is a weak acid. 



(2). Nitro- compounds. Nitrobenzene CeHsNC^ is obtained 

 by the action of a mixture of concentrated nitric and sulphuric 

 acids upon benzene in the cold : 



C 6 H 6 + HN0 3 -> C 6 H 5 .N0 2 + H 2 O. 



It is a pale yellow liquid, with a smell resembling bitter almonds, 

 and is used in scenting cheap soap. 



(3). Amino- compounds. Reduction of nitrobenzene by a 

 metal in acid solution gives aniline CeHs.NH^. The amino- 

 compounds are derivatives of ammonia, and their solutions 

 accordingly are weakly basic. Aniline, when pure, is a colorless, 

 oily liquid, boiling at 185. It is the parent substance of the 

 countless aniline dyes. 



