122 ON A PROCESS OF FRACTIONAL CONDENSATION. 
1. Warren de la Rue and Hugo Miiller,* in their paper entitled “ Chemical Examina- 
tion of Burmese Naphtha or Rangoon Tar,” after detailing the preliminary treatment 
by distillation in a current of steam, add that “A further separation of the various 
products was effected by repeated fractional distillations ; but no absolutely constant 
boiling-points could be obtained, notwithstanding the great number of distillations 
and the large quantity of material at command. It is true that considerable portions 
of distillates could be collected between certain ranges of temperature, tending to 
indicate a constant boiling-point; nevertheless it soon became evident that distillation 
alone could not effect the separations of the various constituents, and that recourse 
must be had to other processes.” The other processes resorted to were, treatment 
with sulphuric and nitric acids, either separately or mixed ; but still with very imper- 
fect results. This acid treatment, which was first proposed by De la Rue, and sub- 
sequently employed by C. Greville Williams,; Schorlemmer, and others, will be further 
noticed below. 
2. Frankland,f in speaking of a mixture of the hydrocarbons of the formule 
C, H, and C, H,,, (now generally considered as C, H,,), which have a difference of 
6° to 7° C. between their boiling-points, says, “The separation of two such bodies by 
distillation alone is impossible”; and suggests that the employment of anhydrous 
sulphuric acid may accomplish the object by dissolving out the body of the formula 
C. Hs 
3. And so recently as 1862, Schorlemmer,§ in his first paper “On the Hydrides of 
the Alcohol-Radicals existing in the Products of the Destructive Distillation of Cannel 
Coal,” remarks that “it was, however, found impossible to obtain a product of con- 
stant boiling-point by repeated fractional distillations”; and he also had recourse to 
the acid-treatment above referred to. 
4. Pebal,|| after an elaborate research on the petroleum from Galicia, in which 
Wurtz’s bulbs were employed, and also Kisenstuck,{] who made an extended investiga- 
* Proceedings of the Royal Society, VIII. 221. 
+ Philosophical Transactions, 1857, 447. 
+ Quarterly Journal of the Chemical Society, 1851, 3, 43. 
§ Journal of the Chemical Society, XV. 419. 
|| Annalen der Chemie und Pharmacie, CX'V. 20, asserts the “ Unmoglichkeit, das Gemenge durch fraction- 
irte Destillationen zu entwirren.” 
 Annalen der Chemie und Pharmacie, CXIII. 169, says as follows : — “Mit den 5° zu 5° aufgesammelten 
Destillaten wurde die fractionirte Destillation wieder von Neuem vorgenommen, aber nachdem diese Operation 
sieben Wochen mit etwas 50 Pfund Steinél fortgesetzt worden war, erhielt ich doch kein Product von irgend 
constantem Siedepunkt. Nach diesen Versuchen halte ich es fiir Unmdglich, das Steinél durch fractionirte 
Destillationen allein in Producte mit constantem Siedepunkt, zu scheiden.” 
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