ied until
constant in weight. The result multiplied by 20 gives the percentage of
fatty acids in the sample.

A quicker method, and one which gives accurate results when care is
bestowed upon it, is to proceed in the manner described above as far as
the decomposition with mineral acid, and to then add 5 or 10 grammes of
stearic acid or beeswax to the contents of the beaker and heat until a
clear layer of fatty matter collects upon the acid liquor.

Cool the beaker, and when the cake is sufficiently hard, remove it
carefully by means of a spatula and dry on a filtering paper, add the
portions adhering to the sides of the beaker to the cake, and weigh.

The weight, less the amount of stearic acid or beeswax added, multiplied
by 20 gives the percentage of fatty acids.

Care must be taken that the cake does not contain enclosed water.

The results of these methods are returned as fatty acids, but are in
reality insoluble fatty acids, the soluble fatty acids being generally
disregarded. However in soaps made from cocoa-nut and palm-kernel oils
(which contain an appreciable quantity of soluble fatty acids) the acid
liquor is shaken with ether, and, after evaporation of the ethereal
extract, the amount of fatty matter left is added to the result already
obtained as above, or the ether method described below may be
advantageously employed.

Where the soap under examination contains mineral matter, the separated
fatty acids may be dissolved in ether. This is best performed in an
elongated, graduated, stoppered tube, the total volume of the ether,
after subsidence, carefully read, and an aliquot part taken and
evaporated to dryness in a tared flask, which is placed in the oven at
100 deg. C. until the weight is constant.

In a complete analysis, the figure for fatty acids should be converted
into terms of fatty anhydrides by multiplying by the factor 0.9875.

In this test the resin acids contained in the soap are returned as fatty
acids, but the former can be estimated, as described later, and deducted
from the total.

_Total Alkali._--The best method is to incinerate 5 grammes of the soap
in a platinum dish, dissolve the residue in water, boil and filter,
making the volume of filtrate up to 250 c.c., the solution being
reserved for the subsequent determination of salt, silicates, and
sulphates, as detailed below.

Fifty c.c. of the solution are titrated with N/1 acid, to methyl orange,
and the result expressed in ter