140 RESEARCHES ON THE VOLATILE HYDROCARBONS. 
zole Series.” I cannot better present his results than by quoting the following 
table : — 
Formula. Boiling-point. Difference. 
Benzole, Cy Hs = C3 (C, He) 80°.8 } 22°.9 
Toluole, Cy Hy = OC, 4 (C, A) 103°.7 } 22°.5 
Xylole, Cis Hi = OC; 5 (C, My) 126°.2 { 22°.2 
Cumole, Cis Fiz = Cy 6 (C, He) 148°.4 ? 22°38 
Cymole, Cy Hy = Cy 7 (C, Ha) 170°.7 
Church states that he obtained all of these bodies from coal-naphtha, and also that 
he obtained benzole from benzoic acid, toluole from toluylic acid, xylole from wood- 
spirit, cumole from cuminic acid, and cymole from oil of cumin; and that he has 
found the corresponding bodies from these different sources to be identical. It will 
be observed that Church claims to have found in coal-tar a body boiling at 126.2, 
which he calls aylle, thus supplying from this source a fifth member of the benzole 
series; whereas Mansfield and Ritthausen found only four bodies within the range of 
temperature indicated by the table. It will also be observed that his determination 
of the boiling-point of toluole is much lower, and that of cumole much higher, than 
the corresponding determinations of Mansfield and Ritthausen ; thus giving room for 
a middle member between them, and preserving a remarkable uniformity of differ- 
ence — viz. 22° and a fraction — between the boiling-points of any two contiguous 
members of the series, for the addition of C, H,. 
That the earlier investigators had found in coal-tar naphtha only the two lower 
members (C,, H, and C,,H,) and the two upper members (Cys Hy, and Cz) H,,), indi- 
cating the absence of the middle member (C,,H,) of the benzole series, was always 
to me an anomaly which I could not reconcile with any plausible theory in regard to 
the formation of these bodies ; and I was led, therefore, to question whether this body 
had not been overlooked in making the separations. The alleged discovery of this 
body in coal-naphtha by Church, together with the beautiful uniformity of the 
boiling-point difference throughout the series which he presented, and the apparent 
care with which the whole research had been conducted, led me to regard his results 
as being more reliable than those which had previously been published. I remained 
under this conviction until I had discovered the boiling-point difference of 30° in other 
series of hydrocarbons,* which led me to doubt the accuracy of Church’s determina- 
tions of boiling-points, and to consider those of Mansfield and Ritthausen as probably 
more correct. 
In the first paragraph of his paper, Church remarks that, “ although doubts still 
* See the following Memoir on this subject. 
