214 TRANSACTIONS OF THE 
THE LIQUID SULPHUR DIOXIDE METHOD OF DE- 
TERMINING AROMATIC HYDROCARBON OILS. 
By THOMAS JOSEPH. 
(Abstract). 
Oils and tars are for the most part complex mixtures of 
solids and liquids, not all of the same type, but belonging 
to widely different chemical groups. Since the commercial 
value of the oil or tar depends upon the relative amounts 
of these various components, a method of making quantita- 
tive determinations is of considerable importance, and a 
number have been proposed. These methods all remove 
the constituents of basic nature by washing a dilute acid, 
and those of acid nature by washing with a dilute alkali. 
There remain then to be determined (a) unsaturated hydro- 
carbons, either cyclic or open chain compounds, (b) benzene 
derivatives and (c) saturated hydrocarbons, either cyclic or 
open chain compounds. The method most commonly pur- 
sued from this point on is to remove the unsaturated 
hydrocarbons by shaking with ordinary concentrated sul- 
phuric acid, the unsaturated compounds dissolving in the 
strong acid, and are then easily separated from the lighter 
layer of immiscible oil. The benzene derivatives are then 
dissolved in dimethy] sulphate, leaving the saturated hydro- 
carbons unattacked. 
Several objections attach to this method, the most 
serious being that none of the separations are complete 
and exact. The sulphuric acid will dissolve some of the 
benzene derivatives, and the dimethy]! sulphate will dissolve 
some of the saturated hydrocarbons, especially if these are 
of low boiling point. Another serious objection is that 
while dimethyl sulphate is almost odorless, and so gives 
no warning, it is at the same time a very active poison. 
In October of 1915 Dr. W. F. Rittman, of the U. S. 
Bureau of Mines, published the details of a different 
method, in which unsaturated compounds and benzene deri- 
vatives are removed together by dissolving in liquid sulphur 
