acids--a mixture of palmitic, oleic, and stearic acids--and not the
glycerine salts of these acids, like ordinary fats, soap is made by
causing them directly to unite with caustic soda. The fats are melted
in a copper, by means of a steam-jacket, or coil of steam-pipe in the
copper, and the soda-lye is run in until complete union has taken place.
The exact point of neutralization can easily be found by taking out
a small sample after stirring, and dissolving it in some methylated
spirits. A few drops of alcoholic tincture of phenol-phthalein are then
added, and as soon as a faint red color appears, addition of soda is
stopped. This shows that the fatty acids have been over-saturated.
Addition of a little more fat renders them perfectly neutral, and the
soap is then ladled out into wooden moulds, lined with loose sheets of
zinc.

The resulting soap is of a brown color, but is perfectly adapted for the
purpose of wool-scouring. It should here be mentioned that, in practice,
the soap is always made somewhat alkaline; in point of fact, it contains
about 2 per cent. of free alkali. This is found to assist in scouring; I
presume that the free alkali forms a soap with the oil added to the wool
during spinning, and if no free alkali be present, this oil would not be
so thoroughly removed.

It will be noticed that in this simple method of soap-making, there is
no salting out to separate the true soap from the watery solution of
glycerine, for no glycerine is present. The apparatus may be of the
simplest nature, and on any required scale, proportionate to the size of
the mill. It is a process which requires no specially skilled labor; in
any works some hand may be told off to conduct the process as occasion
requires; and as a very large proportion of the fatty matter is
recovered, the soap-bill is reduced to a very small fraction of the