L42 RESEARCHES ON THE VOLATILE HYDROCARBONS. 



but that it has the formula which has been assigned to xylole, containing C 2 H 2 less 

 than that of cumole. 



5. That the body obtained from coal-tar naphtha, boiling at 170°, is quite a different 

 body from cymole obtained from oil of cumin, — with which it has been considered 

 identical, as assumed by Mansfield, — these bodies differing from each other by C 2 H 2 . 



6. That cumole from cuminic acid, and cymole from oil of cumin, do not even 

 belong to the benzole series. 



7. That the Parabenzole of Church was in all probability only a mixture of benzole 

 and toluole. 



Of the Quality of Naphtha employed in this Investigation. — As I have taken occasion to 

 question the existence in coal-tar naphtha of two of the substances which it has been 

 said to contain, — viz. cymole, C 2 oHj 4 , and parabenzole, C 12 H 6 , — it is a matter of 

 some importance that I should clearly state the kind or quality of the naphtha 

 employed. The tar from which this naphtha was obtained was a mixture of the tar 

 furnished by the following companies, viz. the New York and the Manhattan Gas- 

 Light Companies, of New York ; Brooklyn Gas-Light Company, of Brooklyn, N. Y. ; 

 Albany Gas-Light Company, of Albany, N. Y. j and the Gas-Light Companies of New- 

 ark and Jersey City, in New Jersey. It was mostly made from Cannel and Newcastle 

 caking coals, which were imported from Liverpool, and mixed in the proportions of 

 one third to five eighths Cannel, to two thirds to three eighths Newcastle. In some 

 of the works a portion of the caking coal was from mines in Pennsylvania. The tar 

 from these different gas-works, as regularly received at the naphtha manufactory, was 

 poured into a large tank provided for this purpose. The stills were uniformly charged 

 with tar directly from this tank ; so that there can be no doubt that the naphtha 

 employed was made from a mixture of the tar supplied by the six different companies 

 above enumerated. Most of the gas-works referred to are large, the annual produc- 

 tion of tar amounting in the aggregate to upwards of 50,000 barrels. It does not 

 appear, therefore, that the absence of the bodies in question from the naphtha which 

 I have employed, can be attributed to any peculiarity of the tar. The naphtha was 

 prepared in a manufactory in New York over which I had at that time personal con- 

 trol, and was purified under my own direction. The process of purification did not 

 differ essentially from that in common use in England, the reagents employed bein 

 oil of vitriol and alkali. One hundred barrels of the purified naphtha were subjected 

 under my personal superintendence, to repeated fractional distillation from an iron 



The chief object in operating on so large a quantity, was to insure the detec- 



cr 



till 



