168 
RESEARCHES ON THE VOLATILE HYDROCARBONS. 
57.1 + 2 = 28°.6 
Average boiling-point difference = 28°.6. 
2p Series. (ot completed.) * 
: Range of Tempera- 
Difference of Aoi P 
aye ci Elemen' ane é ture within which the 
Formula. (?) Boiling-point. ee ay paibogsaint substance would all 
- distil. 
° ° 
Co Hy 
by Elna 68.0 C, H, 1 
ig Ele 98.5 C, H, 30.5 0. 
Oy Fis 125.1 C, H, 26.6 
3. Of Hydrocarbons obtained from Coal-tar Naphtha. 
j Range of Tempera- 
Name of Substance. Formula. Boiling-point. ened poling point es nib ine 
anes distil. 
° ° ° 
Benzole, Cy Hg 80.0 0.8 
Toluole, Cy, Hs 110.3 Cc, A, 80.3 0.7 
Xylole, Cig Hy 139.8 C, H, 29.5 0.4 
Isocumole, Cig Hy, 169.9 C, H, 30.1 1.0 
89.9 
Average increment of boiling-point for the addition of C, H, = 89.9 + 8 = 29°.97. 
4. Of Cumole from Cumime Acid, and Cymole from Oil of Cumin. 
. Range of Tempera- 
Difference of Pre . 
S . Elementary ae ‘ ture within which the 
Name of Substance. Formula. Boiling point. difference, Polling-poink substance would all 
and. eye 
distil. 
° ° ° 
Cumole, Cis Hye 151.1 3.6 
Cymole, 9 ys 179.6 C, H, 28.5 12 
With only a single exception, the results presented in the above tables point clearly 
to 30° as the common increment for the addition of C,H, in homologous series of 
hydrocarbons. Indeed, leaving out of the calculation the third series from petroleum 
(having the general formula C,H,),— which must remain anomalous, — and also the 
products from oil of cumin, the average of all the other boiling-point differences is 
29°.75. The few individual variations from the number 30°, rarely exceeding a single 
degree, may reasonably be attributed to errors of the thermometer (especially in case 
of temperatures above 100°), or in some instances to a want of purity of one of the 
compared substances ; which latter cause I doubt not is the case with the body from 
petroleum boiling at 37°, as upon this body I had bestowed less labor in fractioning 
than upon most of the others, on account of the extreme volatility and consequent 
* See foot-note on the preceding page. 
