RESEARCHES ON THE VOLATILE HYDROCARBONS. 171 
That the difference may also be /ess than 19° in some series receives confirmation 
from the facts presented in the following tables. 
6. Of the Nitro-compounds derived from the Hydrocarbons of the Benzole Series. 
Bytes ner iain "ine Dinwrenee’ | Bolling pst 
Nitro-benzole, C,, H; NO 213.1 ; 
Nitro-toluole, ° Cy, H, NO, 995.9 C, H, 13.8 
Nitro-xylole, C,, H, NO, 239.3 C, A, 13.4 
Nitro-isocumole, C,, Hy, NO, C, H, 
7. Of the Alkaloids derived from the Hydrocarbons of the Benzole Series. 
Name of Substance. Formula, rr Ditesne Balliogepeint 
Aniline, C,H, N 184.6 ‘ 
Toluidine, Cy H, N 201.7% C, H, 17.1 
Xylidine, Cy, Hy N 216.0* C, H, 
Iso-cumidine, Cys Hig N C, H, 
In regard to the results presented in the last two tables, it may be remarked, first, 
that of the difference shown in the table of nitro-compounds, viz. an average of 13°.6, 
the discrepancy between this and the number 19°, being 5°.6, is so large as to leave 
no room for reasonable doubt that this is one of those exceptional series in which 
the boiling-point difference is less than 19° for the elementary difference of C, Hy. 
As this series does not appear to have been examined by Kopp, I have taken care 
to make as accurate a determination of the difference as circumstances would allow. 
The boiling-points were corrected as usual for pressure and the upper mercurial col- 
umn. The boiling-points which have already been published of these bodies, so far as 
I have noticed, appear to have been given in the observed, i. e. uncorrected tempera- 
tures. The quantities of nitro-benzole and nitro-toluole which I operated upon were 
sufficiently large, and of a high degree of purity, presenting perfectly constant boiling- 
points. The quantity of nitro-xylole, however, was not so large as would have been 
desirable. Although the boiling-point of this body is doubtless very nearly correct, 
those of nitro-benzole and nitro-toluole are more to be relied upon ; and omitting the 
fraction, the number 14° may, I think, be safely taken as the true boiling-point differ- 
ence in this series. Secondly, that the less striking difference presented in the series of 
alkaloids, being only 2° under the number 19°, cannot reasonably justify the assump- 
tion that this small discrepancy of 2° is attributable to impurity of the substances, or to 
* Not corrected. 
