402 THE CHEMISTKY OF ESSENTIAL OILS
Ten c.c. of the oil are heated for one hour on a sand-bath in an
acetylation flask with twice its volume of formic acid (specific gravity,
1*226). It is advisable to add a few pieces of pumice to assist the boil-
ing. The contents of the flask are cooled and 100 c.c. of water added,
and the whole transferred to a separator. The acid layer is run off, and
the oil is washed with water until the washings are neutral. It is then
dried by means of anhydrous sodium sulphate and filtered. The formy-
lated oil is then saponified with alcoholic potash in the usual manner,
free acids being first neutralised, and the percentage of citronellol in the
original oil calculated from the following formula :—Total citronellol =
0
'
156 x x 10
°.
w - (0-028)
where x is the number of c.c.'s of normal alcoholic potash absorbed and
w the weight of formylated oil.
It was found by experiment that practically the same results were
obtained in the case of geranium oils, whether the oil was first saponified
or not. It is, therefore, sufficiently accurate to formylate the oil without
first decomposing the esters, since the formic acid apparently acts on the
alcohols whether combined or not.
Jeancard and Satie
j
determine the stearoptene as follows :—
Ten grams of the otto are weighed into a beaker and 50 c.c. of
acetone are added. The liquid is cooled to - 10° or thereabouts, without
shaking, and then filtered through a funnel kept in a refrigerating mix-
ture. The stearoptene is washed several times with cold acetone, and
dried on the weighed filter paper in vacua over sulphuric acid.
Burgess finds that for the estimation of the stearoptene 85 per cent,
•alcohol gives the most accurate results. He finds that 5 grams of
the otto (in these experiments he also used 5 grams of a standard
solution of stearoptene in geranium oil, and in citronellol—see table), in
"25 c.c. of the solvent—or, if a weaker alcohol be used, 50 c.c.—is the
most suitable quantity for the determination. Solution is effected by
means of heat, and the liquid is then cooled in ice for five or six hours.
'The stearoptene is then filtered off on paper over a filter pump and
washed, once if 85 per cent, alcohol be used, twice if a weaker spirit be
^employed ; the paper with the separared stearoptene is then dried in
-vacuo over sulphuric acid for twelve hours. It is not necessary to tare
the filter paper, since the stearoptene can be removed in one cake from
the paper, and weighed on a watch glass.
The appended table (p. 403) shows the results obtained with the
various solvents on otto of rose, and on standard solutions of stearop-
tene in geraniol, and in citronellol. With acetone, he tound in some
cases that a further separation of stearoptene took place, so that he
has recorded the results in the form of the two weighings of the stearop-
tene where necessary.
By addition of alcohol and freezing the stearoptene can be almost
^entirely separated on a filter pump and washed with alcohol and finally
•dried." It should then melt between 32^3 and 37°, usually at 33° to 34 °
.Spermaceti, and most samples of paraffin wax, will cause this to be
rather higher, as will also " guaiacum wood " oil if present in more than
very small quantities. Salol and antipyrin have been found as solid
adulterants.
1
Bull. Soc. Chirn., Paris (1904), 934.