76 Transactions of the 



When coal is subjected to dry distillation, gases are driven off, 

 ■which after being purified form ordinary coal gas, while coke remains 

 in the retorts. Besides these products, liquids are condensed in the 

 receiyers. These, on standing, separate into two layers, the aqueous 

 one of which contains chiefly ammonia, while the composition of the 

 dark oily layer or tar is very complicated and varying. "When dis- 

 tilled, the water and ammonia are first driven off', and the distillate 

 may then roughly be divided into naphtha, creosote, and anthracene oil, 

 while a residue of pitch remains behind. The naphtha, which comes 

 over first and which is lighter than water, is treated with sodium 

 carbonate, tliereby precipitating sodium phenate or carbolate, from 

 which, on acidifying with sulphuric acid, carbolic acid or phenol is 

 produced. This latter is much used now as a disinfectant, for dress- 

 ing wounds, for preparing picric acid, &c. The liquid which is left, 

 after treating the naphtha with sodium carbonate, is distilled, when it 

 gives first of ail crude benzol, then solvent naphtha, and lastly heavy 

 or burning naphtha. The creosote portion of the distillate yields 

 naphthalene and liquid creosote, which is much used for pickling 

 timbers and for burning into lamp black. From the anthracene oil, 

 anthracene crystallises out, and the oil that is left is used for greasing 

 machinery. 



It is of benzol and anthracene I wish particularly to speak. Benzol 

 or benzene or phenene is a colourless, volatile, and highly inflammable 

 liquid, burning with a bright smoky flame. From a consideration of 

 its vapour, density, analysis, and chemical re-action, the formula 

 Cg Hg has been assigned to it. If fmning nitric acid be added to it a 

 very violent reaction ensues, unless care be taken, and a brown liquid 

 is formed. If this is poured into water, a yellow oil, which is nitro- 

 benzol, is obtained. This is used for coarse perfumery, under the 

 name of essence of miobane. It is from this that aniline and hence 

 aniline colours are obtained. 



In 1826 Unverborben found among the products of the dry 

 distillation of indigo, a base, which he named " crystalline," from 

 the ease with which some of its salts crystallised. 



In 1834 Runge found a body in coal tar oil, which he named 

 "kyanol," from the blue colour which it gave with bleaching powder. 



In 1840 Fi'itsche showed that anthranilic acid, a derivative of 

 indigo, decomposed, on being heated, into carbon, dry oxide, and a 

 basic substance, which he called " aniline," from anil, the Portuguese 

 name for indigo. 



In 1842 Zinin obtained what he called "benzidam," by the 

 reduction of nitrobenzol by sulphide of ammonium. 



In 1843 Hofmann showed that all these four bodies were one and 

 the same base, for which he kept the name of " aniline." 



For manufacturing purposes aniline is always got from nitrobenzol, 

 by reducing it with iron turnings and acetic acid. It is a somewhat 

 oily, colourless liquid, of a faintly aromatic smell, and burning with 

 a bright flame. Its characteristic property, however, is that it gives, 



