ette into a measured volume of the oil with
constant agitation, until the oil forms a clear solution with the
alcohol. Having noted the quantity of alcohol added, it is well to run
in a small further quantity of alcohol, and observe whether any
opalescence or cloudiness appears.

_Acid_, _ester_, and _saponification values_ are determined exactly as
described under fats and oils. Instead of expressing the result as
saponification value or number, the percentage of ester, calculated in
the form of the most important ester present, may be obtained by
multiplying the number of c.c. of N/1 alkali absorbed in the
saponification by the molecular weight of the ester. Thus, to find the
percentage as linalyl acetate, the number of c.c. absorbed would be
multiplied by 0.196 and by 100, and divided by the weight of oil taken.

_Alcohols._--For the estimation of these, if the oil contains much ester
it must first be saponified with alcoholic potash, to liberate the
combined alcohols, and after neutralising the excess of alkali with
acid, the oil is washed into a separating funnel with water, separated,
dried with anhydrous sodium sulphate, and is then ready for the alcohol
determination.

If there is only a small quantity of ester present, this preliminary
saponification is unnecessary.

The alcohols are estimated by conversion into their acetic esters, which
are then saponified with standard alcoholic potash, thereby furnishing a
measure of the amount of alcohol esterified.

Ten c.c. of the oil is placed in a flask with an equal volume of acetic
anhydride, and 2 grammes of anhydrous sodium acetate, and gently boiled
for an hour to an hour and a half. After cooling, water is added, and
the contents of the flask heated on the water-bath for fifteen to thirty
minutes, after which they are cooled, transferred to a separating
funnel, and washed with a brine solution until the washings cease to
give an acid reaction with litmus paper. The oil is now dried with
anhydrous sodium sulphate, filtered, and 1-2 grammes weighed into a
flask and saponified with alcoholic potash as in the determination of
ester or saponification value.

The calculation is a little complicated, but an example may perhaps
serve to make it clear.

A geranium oil containing 26.9 per cent. of ester, calculated as geranyl
tiglate, was acetylated, after saponification, to liberate the combined
geraniol, and 2.3825 grammes of the acetylated oil required 9.1 c.c.