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60 REPORT OF SCHIMMEL & Co. APRIL 1914. - ‘ 
eliminated hydrocarbons. Bdécker prescribes the following modus operandi: from 100 to ™ 
200 cc. of oil is fractionally distilled in vacuo. The distillation is only continued up 
to the point where the separate fractions of about 10 cc. each still show dextrorotation. 
These fractions are put together as the “terpene-containing portion” of the oil, the 
rest constituting the “sesquiterpene-containing portion”. Each of these portions is then 
freed from citral by means of sodium sulphite, and in both cases the residue is treated 
with 100 times its quantity of ice-cold 51 p.c. alcohol in the manner detailed above, 
a large glass flask being, if necessary, substituted for the funnel. The alcoholic solution 
is separated by means of a syphon from the portion which has remained undissolved. 
The oils which have been separated are estimated quantitatively, and from the values 
thus obtained the percentage-proportion of terpenes and sesquiterpenes in the original 
oil is calculated. For purposes of further identification the rotation is estimated, and, 
if necessary, the characteristic derivatives are prepared. The terpenes, of which the 
principal constituent is d-limonene, are characterised by a pronounced dextrorotation; 
they yield a liberal proportion of limonene tetrabromide, whereas the sesquiterpenes, 
which consist chiefly of bisabolene, are lavorotatory and may be identified from the 
bisabolene trihydrochloride. 
Bocker has tested his method successfully with a whole series of experimental 
mixtures. In the case of a terpeneless lemon oil of his own manufacture he found 
51,5 p.c. citral and 21 p.c. hydrocarbons; another sample of the same description, 
free from terpenes and sesquiterpenes, gave 62 p.c. citral and imponderable traces: of 
hydrocarbons. For terpeneless lemon oil, Bocker considers a hydrocarbon percentage 
of 25 to 30 to be normal. He assumes that the hydrocarbon content of other concen- 
trated essential oils may be estimated in a similar manner and is engaged in experi- 
ments on the subject. 
It is familiar ground that the terpeneless lemon oils are differentiated in those 
which have been freed from terpenes only, and those which have also been freed from 
sesquiterpenes. Moreover, according to the different methods of treatment, which are 
kept secret by the various manufacturers, the elimination of hydrocarbons is more or 
less complete, hence the characters of the resulting oils exhibit somewhat considerable 
divergences. E.]. Parry’), who has examined a series of such concentrated lemon oils, 
has observed the following limits of value: — 
Terpeneless Terpene- and sesquiterpeneless 
diso. . 0,8935 to 0,899 0,898 to 0,902 
a . . —5° to —8°30' + 1° to — 3° 45’ 
Np . . about 1,4810 = 
Citral . 42 bis 48 °/o average 05 °/o or a little more. 
The terpeneless oils did not contain above 5 p.c. of terpenes; generally the pro- 
portion was even less than that. A higher terpene-content is expressed by a reduction 
of solubility and a lower specific gravity. Moreover, the lzvoration diminishes, and, 
where this is possible, is converted into dextrorotation. The particulars given of 
terpene- and sesquiterpeneless oils refer to preparations in which little or no hydro- 
carbons were left. 
In connection with the above, Parry further observes that although it is true that 
the solubility of lemon oil is increased in proportion to the degree of completeness 
1) Chemist and Druggist 88 (1913), 378. 
