f
sulphuric acid used in the first instance, allows a calculation to be
made as to the quantity of effective alkali in the soap, for example:--

23.86 grms. of soap (partly cocoa-nut oil soap).
17.95 " fatty acids with filter.
04.44 " filter.
-----
13.51 grms. of hydrates of fatty acids = 56.62 per cent.

28.00 cub. cent. of the diluted sulphuric acid applied for the
decomposition of the soap, of which 100 cub. cent.
represent 2982 grms. of carbonate of soda.

17.55 cub. cent. of alkaline fluid, which were used for the
saturation of the above acid, and of which 100 cub.
cent. saturate an equal quantity of that acid.
----
10.45 cub. cent. of the sulphuric necessary for the alkali
contained in the soap, representing 0.1823 grms. of
soda = 7.64 per cent.

A determination of the alkali as a sulphate afforded in another portion
of soap 9.57 per cent. of soda, because the sulphate of soda and
chloride of sodium present in the soap gave up their alkali.

The alkaline fluid applied by me was a saccharine solution of lime,
which can be naturally replaced by a solution of soda, and must be if
the chloride of sodium and sulphate of soda mixed with the soap shall be
determined in the following way:--

The fluid again exactly neutralized with alkali is evaporated to
dryness, and the residue gently heated to redness. As in the above
manipulation, the fluid was not heated to the boiling point, the
original chloride of sodium and sulphate of soda are contained in the
weighed residue, besides the soda of the soap and that which has been
added with the sulphuric acid, forming sulphate of soda. A second
exposure to a red heat with sulphuric acid converts the whole residue
into sulphate of soda, and from the increase of weight, by a comparison
of the equivalents of NaCl and NaO, SO_{3} the quantity of the former
may be decided. According to the equivalents which Kopp furnished in
1850, the increase of weight to the chloride of sodium is as 1:4.68. The
original sulphate of soda must be, lastly, found by the subtraction of
the same salt formed plus the calculated chloride of sodium from the
first heated residue.

In practice, it is seldom necessary to proceed with the determination of
the chloride of sodium and sulphate of soda, except with stirred and
cocoa-nut oil soaps; certainly less of the truth is seen if, after the
above determination of the fatty ac