|40 RESEARCHES ON THE VOLATILE HYDROCARBONS. 



zole Series." I cannot better present his results than by quoting the following 



tabl 



e 



Formula. Boiling-point. Difference. 



Benzole, C,, H 6 = C 6 3 (C 2 H 2 ) 80 .8 . 22 o 9 



Toluole, C I4 H 8 = C 6 4 (C 2 H 2 ) 103°.7 ^ 2r5 



Xylole, C 16 H 10 = C e 5 (C 2 H 2 ) 126 .2 . 22 <, 2 



Cumole, C 18 H 12 = C 6 6 (C 2 H 2 ) 148°.4 > 22 o 3 



Cymole, C* H M = C e 7 (C 2 H 2 ) 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- 



and that h 



spirit, cumole from cuminic acid, and cymole from oil of cumin 

 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 xyble, 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 Co H 



2 Xi 2 



That the earlier investigators had found in coal-tar naphtha only the two lower 

 members (C 12 H 6 and C 14 H 8 ) and the two upper members (C 18 H 12 and C20 H 14 ), indi- 

 cating the absence of the middle member (C 1& H 10 ) 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 subiect. 



