142 RESEARCHES ON THE VOLATILE HYDROCARBONS. 
but that it has the formula which has been assigned to xylole, containing C, H, 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, H;. 
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.H,,, and parabenzole, C,,H,,— 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.; 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 being 
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 
still. The chief object in operating on so large a quantity, was to insure the detec- 
