of
N/1 alkali for its saponification.

Now every 196 grammes of geranyl acetate present in the acetylated oil
correspond to 154 grammes of geraniol, so that for every 196 grammes of
ester now present in the oil, 42 grammes have been added to its weight,
and it is therefore necessary to make a deduction from the weight of oil
taken for the final saponification to allow for this, and since each
c.c. of N/1 alkali absorbed corresponds to 0.196 gramme of geranyl
acetate, the amount to be deducted is found by multiplying the number of
c.c. absorbed by 0.042 gramme, the formula for the estimation of total
alcohols thus becoming in the example given:--

9.1 x 0.154 x 100
Per cent. of geraniol = ---------------------- = 70.2
2.3825 - (9.1 x 0.042)

The percentage of combined alcohols can be calculated from the amount of
ester found, and by subtracting this from the percentage of total
alcohols, that of the free alcohols is obtained.

In the example quoted, the ester corresponds to 17.6 per cent. geraniol,
and this, deducted from the total alcohols, gives 52.6 per cent. free
alcohols, calculated as geraniol.

This process gives accurate results with geraniol, borneol, and menthol,
but with linalol and terpineol the figures obtained are only
comparative, a considerable quantity of these alcohols being decomposed
during the acetylation. The aldehyde citronellal is converted by acetic
anhydride into isopulegol acetate, so that this is also included in the
determination of graniol in citronella oil.

_Phenols._--These bodies are soluble in alkalies, and may be estimated
by measuring 5 c.c. or 10 c.c. of the oil into a Hirschsohn flask (a
flask of about 100 c.c. capacity with a long narrow neck holding 10
c.c., graduated in tenths of a c.c.), adding 25 c.c. of a 5 per cent.
aqueous caustic potash solution, and warming in the water-bath, then
adding another 25 c.c., and after one hour in the water-bath filling the
flask with the potash solution until the unabsorbed oil rises into the
neck of the flask, the volume of this oil being read off when it has
cooled down to the temperature of the laboratory. From the volume of oil
dissolved the percentage of phenols is readily calculated.

_Aldehydes._--In the estimation of these substances, use is made of
their property of combining with sodium bisulphite to form compounds
soluble in hot water. From 5-10