Chemistry of Essential Oils

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 :—

1. 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.


2. The use of hydrochloric acid in neutralising the excess of alkali
   after saponification.


3. The employment of water in the steam generating flask which
   has been insufficiently boiled to free it from carbon dioxide and other
   impurities.


4. 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.