never used in exact chemical equivalents, but an excess is always
taken. Potash soap is much more soluble than a soda soap; it therefore
penetrates the fiber, and consequently removes dirt and grease much more
quickly. Notwithstanding, also, that its chemical combining equivalent
is greater than that of soda, it is, nevertheless, the strongest base,
and always combines with any substance in preference to soda. For these
reasons--probably combined also with the fact that in the whole realm of
the animal and vegetable kingdoms, to which all textile fabrics belong,
potash is more naturally assimilated than soda--a smaller quantity of
potash soap will do more practical work than a larger quantity of soda
soap.

There are other reasons why potash soaps have not been used; originally
soft soap was made either with fish oil or olive oil. Fish oil is
objectionable, as the strong smell imparted to the soap renders it unfit
for many finishing purposes. Nothing can be better than olive oil soap,
but it is a costly article, and only can be used for finer purposes.
There are now, however, many of the seed oils that are much cheaper.
Linseed, rape seed, and cotton seed all produce a good soap. Cotton seed
oil is particularly suitable for the purpose; the manufacture of this
oil during the last few years has been brought to great perfection, and
the cost is now much less than that of tallow or of any other seed oil.
It is now difficult to distinguish a well refined cotton seed oil from
olive oil; it is therefore in every way suitable for making soft soap.
One of the chief causes, however, why potash soap has not been
more generally made is that a convenient form of potash has been
unobtainable. For many years the only source of potash was from the
ashes of burnt trees. These ashes are collected, mixed with lime,
lixiviated, and the resulting lye boiled down. The result is a very
impure form of potash, also of a very variable composition, depending