448 THE CHEMISTEY OF ESSENTIAL OILS
and a distillation value of 92*8, and one containing 5 per cent, of ethyl
succinate gave a direct value of 127*6 and a distillation value of 91*5.
Umneyi has made a critical study of this method, and recommends
the following apparatus to be used in the process (see Fig. 47):—
(a) A 3 litre Jena glass flask.
(b) A rubber connection, the removal of which, of course, immedi-
ately cuts off the steam supply.
(c) A long-necked CO 2 flask of Jena glass and 150 c.c. capacity.
(d) The most suitable splash head for the operation.
(e) A Davies' condenser.
(/) A 500 c.c. Erlenmeyer flask.
FIG. 47.
The results obtained, unless the special precautions described be
adopted when calculated as percentages of .ester in the oil, are consider-
ably too high. Whilst some of the causes may be apparent to many,
nevertheless the following is a list constructed to include the more im-
portant of these causes, and will serve to indicate in what manner the
necessary amendments should be made :—
- The use of methylated spirit (unpurified by further distillation)
" in the preparation of the standard potash solution employed by some
experimenters in the saponification of the oil. - The use of hydrochloric acid in neutralising the excess of alkali
after saponification. - The employment of water in the steam generating flask which
has been insufficiently boiled to free it from carbon dioxide and other
impurities. - The sulphuric acid, used to acidulate before distillation, may be
advantageously replaced by phosphoric acid. This modification, whilst
(^1) P. and E.O
M. (1914), 116.