448 
ME. C. GEEVILLE WILLIAM;S OX S03IE OE THE PEODUCTS 
large scale at Bathgate, near Edinburgh. A ver}' partial examination of it has been 
published by Dr. Genthee*, with results which, as we shall afterwards see, are far from 
correct ; for he has assumed that the fractions obtained at particular boiling-points are 
homogeneous, and consist of different but isomeric hydrocarbons of the formula C^H". 
In addition to paraffine, long known as one of the products, he has detected picoline 
and phenole ; but, nevertheless, his results, on the whole, are rather in favour of the Gew 
that the Torbane-hill mineral is not a true coal in the sense generally understood by 
chemists. I do not enter here upon the much-disputed and litigated question of the 
nature of the mineral itself, my object being solely to study the chemical relations of 
the bodies produced by its decomposition under the mfluence of heat. 
The ordinary Boghead naphtha appears in commerce in the form of a nearly colour- 
less fluid of a very characteristic odour, quite different to that obtained from ordinaiw 
coal. Its specific gravity is only 0-750 at 15°, and is therefore greatly lower than that 
from the latter source, for even thoroughly purified benzole has a density of 0-850. 
Notwithstanding its small density the boiling-point was high, the lowest fraction that 
could be obtained in the first rectification being between 143° and 148°. That the fluid 
was a mixture of many bodies of very different boihng-points, was sho-wn by the fact that 
during the first distillation the mercury in the thermometer steadily rose to the highest 
range it was safe to allow. This complexity was still better seen by the sudden depres- 
sion of the boiling-point of the first fraction in the second distillation, for there was then 
obtained a considerable quantity of fluid between 121° and 126°, the second rectification 
thus causing a fall of no less than 22°; subsequent to this, the lowering of the mitial fr-ac- 
tion with the advance in the number of rectifications was less marked, but still decided, 
and after six distillations I was able to procure a portion boiling as low as 98°-5. 
It appearing evident that, previous to attempting any examhiation, it would be essen- 
tial to obtain the crude hydrocarbons of nearly constant boihng-point, they were sub- 
mitted to a tolerably complete fractionation, during which there were made, altogether, 
no less than one thousand distillations. 
An opinion has been hazarded by some persons, that in processes of fractional distil- 
lation a continual breaking up is taking place, which they suppose to account for the 
variations in the point of ebullition : that the supposition is incorrect uill be admitted 
by all chemists who have given close attention to processes of this kind, and the ques- 
tion is placed beyond doubt by the fact that the variation becomes less as the distilla- 
tions are more numerous, and, at last, the fractions distil almost entii-ely between the 
points at which they last came over, and doubtless might, if siifficient time was expended 
on them, be obtained perfectly steady. 
As soon as by the means described fractions were obtained of almost constant boiling- 
points, I proceeded to ascertain whether the fluids consisted of more than one substance, 
and, passing over the preliminary trials, it was soon found that more than one series of 
bodies were present. This was proved by the deportment of the mixed hydi-ocarbons 
* Liebig’s Annalen, xcvii. p. 277, and Chemical Gazette, 1856, No. 330. 
