124 ON A PROCESS OF FRACTIONAL CONDENSATION. 
Of the New Process. 
The chief distinctive feature of my process, as compared with the common < 
consists in this, — that the operator has complete and easy control of the temperat 
of the vapors given off in distillation ; and consequently can readily cool these vay 
to the lowest limit of temperature which the most volatile portion, under the circ 
stances, is able to bear and retain its vaporous condition. It will be seen at a gla 
that, under these conditions, the operator has it in his power to secure in any « 
the very largest possible amount of condensation of the heavier from the lig! 
vapors. The liquids resulting from the condensation of the less volatile portion 
course fall back into the retort, while the vapors of the more volatile parts conti 
to go forward to a cold condenser, descending in the opposite direction, from wk 
the condensed product falls into a special receiver. In this manner he is able 
obtain, in each successive operation, a series of products which shall contain 
minimum quantity of the less volatile constituents, which a single distillation is cx 
ble of affording. 
Of the common process, on the contrary, nearly the reverse of all this is true: 
operator having no control whatever ; being forced to receive the vapors at the t 
perature which they naturally acquire in passing from the retort, and laden with s 
proportion of the less volatile bodies as may be carried forward with them.* 
* The only apparatus, of which I have any knowledge, which can be regarded as bearing any analogy tc 
own, is that employed in the rectification of alcoholic spirits, on a manufacturing scale. In one of the « 
forms of this apparatus, that of Solimani, to which my attention was first called by a friend, after my prc 
had been in use more than a twelvemonth, the temperature of a dephlegmator is kept within such limits : 
give alcohol of any required strength more readily than by the common methods. The mode of constructic 
this apparatus is, however, only adapted to manufacturing purposes, and it could not be utilized in the 1 
exact experiments required in scientific research. Either on account of its complication, or some other c: 
the apparatus of Solimani has, I believe, long since been abandoned. 
Mansfield (Quarterly Journal of the Chemical Society, 1849, I. 264), observing that “the boiling-poi 
benzole is the same as that of alcohol of sp. gr. 0.825,” remarks that “any of the summary processes of re 
cation which are practised by distillers in the manufacture of alcoholic spirits, are applicable to the separ: 
of benzole from the less volatile fluids of naphtha”; and, appended to his scientific treatise on coal-tar, u 
the title “ Of a Practical Mode of Preparing Benzole,” goes on to describe a process for that purpose, w 
I believe, he had previously patented. It appears that Mansfield did not employ this process in his rese: 
but obtained his benzole, as well as the other less volatile hydrocarbons, in the usual manner, — by si 
distillation. 
In the belief that no process of fractioning at all analogous to mine has ever been employed in scie 
research, and that I am not in any way directly indebted to any of the devices of my predecessors, I 
taken no special pains to consider these devices in much detail. I may say, however, that I have foun 
