by all investigators. Balbiano and
Marcusson doubt the validity of Lewkowitsch's conclusions, and Fanto,
experimenting on the saponification of olive oil with caustic potash, is
unable to detect the intermediate formation of any mono- or diglyceride,
and concludes that in homogeneous solution the saponification is
practically quadrimolecular. Kreeman, on the other hand, from
physico-chemical data, supports the view of Geitel and Lewkowitsch that
saponification is bimolecular, and though the evidence seems to favour
this theory, the matter cannot be regarded as yet definitely settled.

Hydrolysis can be brought about by water alone, if sufficient time is
allowed, but as the process is extremely slow, it is customary in
practice to accelerate the reaction by the use of various methods, which
include (i.) the application of heat or electricity, (ii.) action of
enzymes, and (iii.) treatment with chemicals; the accelerating effect of
the two latter methods is due to their emulsifying power.

The most usual method adopted in the manufacture of soap is to hydrolyse
the fat or oil by caustic soda or potash, the fatty acids liberated at
the same time combining with the catalyst, _i.e._, soda or potash, to
form soap. Hitherto the other processes of hydrolysis have been employed
chiefly for the preparation of material for candles, for which purpose
complete separation of the glycerol in the first hydrolysis is not
essential, since the fatty matter is usually subjected to a second
treatment with sulphuric acid to increase the proportion of solid fatty
acids. The colour of the resulting fatty acids is also of no importance,
as they are always subjected to distillation.

During the last few years, however, there has been a growing attempt to
first separate the glycerol from the fatty acids, and then convert the
latter into soap by treatment with the carbonates of soda or potash,
which are of course considerably cheaper than the caustic alkalies, but
cannot be used in the actual saponification of a neutral fat. The two
processes chiefly used for this purpose are those in which the reaction
is brought about by enzymes or by Twitchell's reagent.

I. _Application of Heat or Electricity._--Up to temperatures of 150 deg. C.
the effect of water on oils and fats is very slight, but by passing
superheated steam through fatty matter heated to 200 deg.-300 deg. C. the
neutral glycerides are completely decomposed into glycerol and fatty
acids