1886.] on Becent Progress in the Coal-tar Industry. 453 



resemblance, whilst the ending in ' ol ' corresponds better to its pro- 

 perties and mode of production. It wonld have been perhaps better 

 if the name which the discoverer, Faraday, had given to this body- 

 had been retained, as its relation to benzoic acid and benzoyl com- 

 pounds is not any closer than it is to that of the tar or coal from 

 which it is obtained." 



Almost at the same time Peligot found that the same hydrocarbon 

 occui's, together with benzene, C13H10O (diphenylketone CO(CoH5)^), 

 in the products of the dry distillation of calcium benzoate. 



The different results obtained by Mitscherlich and Peligot arc 

 represented by the following formula : — 



C-HgO. + CaO = CgHe + CaCOg. 

 (C;H.d2)2Ca = CisHioO + CaCOg. 



Peligot obtained benzene only as a by-product, exactly as in the 

 preparation of acetone (dimethylketone) from calcium acetate, a 

 certain quantity of marsh gas is always formed. 



It is not clear how Liebig became acquainted with the fact that 

 benzene is formed by the dry distillation of coal, as his pupil Hof- 

 mann, who obtained it in 1845 from coal-tar, observes: "It is 

 frequently stated in memoirs and text-books that coal-tar oil contains 

 benzene. I am, however, unacquainted with any research in which 

 this question has been investigated." It is, however, worthy of 

 remark that about the year 1834, at the time when Mitscherlich had 

 converted benzene into nitrobenzene, the distillation of coal-tar was 

 carried out on a large scale in the neighbourhood of Manchester ; the 

 naphtha which was obtained was employed for the purpose of dissolving 

 the residual pitch, and thus obtaining black varnish. Attempts were 

 made to supplant the naphtha obtained from wood-tar, which at that 

 time was much used in the hat factories at Gorton, near Manchester, 

 for the preparation of " lacquer," by coal-tar naphtha. The substitute, 

 however, did not answer, as the impure naphtha left, on evaporation, 

 so unpleasant a smell, that the workmen refused to employ it. It 

 was also known about the year 1838, that wood-naphtha contained 

 oxygen, whilst that from coal-tar did not, and hence Mr. John Dale 

 attempted to convert the latter into the former, or into some similar 

 substance. By the action of sulphuric acid and potassium nitrate, he 

 obtained a liquid possessing a smell resembling that of bitter almond 

 oil, the properties of which he did not further investigate. This was, 

 however, done in 1842 by Mr. John Leigh, w^ho exhibited considerable 

 quantities of benzene, nitrobenzene, and dinitrobenzene, to the 

 Chemical Section of the British Association meeting that year in 

 Manchester. His communication is, however, so printed in the 

 Report, that it is not possible from the description to identify the 

 bodies in question. 



Large quantities of benzene were prepared in 1848, under Hof- 

 mann's direction, by Mansfield, who proved that the naphtha in coal- 

 tar contains homologues of benzenes, which may be separated from it 



