olution in water.

This theory is considered by Hillyer (_Journ. Amer. Chem. Soc._, 1903,
524), however, to be quite illogical, for, as he points out, the
liberated alkali would be far more likely to recombine with the acid or
acid salt from which it has been separated, than to saponify a neutral
glyceride, while, further, unsaponifiable greasy matter is removed by
soap as easily as saponifiable fat, and there can be no question of any
chemical action of the free alkali in its case. Yet another argument
against the theory is that hydrolysis is greater in cold and dilute
solutions, whereas hot concentrated soap solutions are generally
regarded as having the best detergent action.

Rotondi (_Journ. Soc. Chem. Ind._, 1885, 601) was of the opinion that
the basic soap, which he believed to be formed by hydrolysis, was alone
responsible for the detergent action of soap, this basic soap dissolving
fatty matter by saponification, but, as already pointed out, his theory
of the formation of a basic soap is now known to be incorrect, and his
conclusions are therefore invalid.

Several explanations have been suggested, based on the purely physical
properties of soap solutions. Most of these are probably, at any rate in
part, correct, and there can be little doubt that the ultimate solution
of the problem lies in this direction, and that the detergent action of
soap will be found to depend on many of these properties, together with
other factors not yet known.

Jevons in 1878 in some researches on the "Brownian movement" or
"pedesis" of small particles, a movement of the particles which is
observed to take place when clay, iron oxide, or other finely divided
insoluble matter is suspended in water, found that the pedetic action
was considerably increased by soap and sodium silicate, and suggested
that to this action of soap might be attributed much of its cleansing
power.

Alder Wright considered that the alkali liberated by hydrolysis in some
way promoted contact of the water with the substance to be cleansed, and
Knapp regarded the property of soap solutions themselves to facilitate
contact of the water with the dirt, as one of the chief causes of the
efficacy of soap as a detergent.

Another way in which it has been suggested that soap acts as a cleanser
is that the soap itself or the alkali set free by hydrolysis serves as a
lubricant, making the dirt less adherent, and thus promoting its
removal.

The most likely theory