f water and
manganese sulphate or other metallic salt. It is further stated that
acetic acid may be added at the beginning of the operation, or use may
be made of that formed during the process, though in the latter case
hydrolysis is somewhat slower.

Experiments have been carried out by Lewkowitsch and Macleod (_Journ.
Soc. Chem. Ind._, 1903, 68, and _Proc. Roy. Soc._, 1903, 31) with
ferments derived from animal sources, _viz._, lipase from pig's liver,
and steapsin from the pig or ox pancreas. The former, although it has
been shown by Kastle and Loevenhart (_Amer. Chem. Journ._, 1900, 49) to
readily hydrolyse ethyl butyrate, is found to have very little
fat-splitting power, but with steapsin more favourable results have been
obtained, though the yield of fatty acids in this case is considerably
inferior to that given by castor seeds. With cotton-seed oil, 83-86 per
cent. of fatty acids were liberated as a maximum after fifty-six days,
but with lard only 46 per cent. were produced in the same time. Addition
of dilute acid or alkali appeared to exert no influence on the
decomposition of the cotton-seed oil, but in the case of the lard,
dilute alkali seemed at first to promote hydrolysis, though afterwards
to retard it.

Fokin (_Chem. Rev. Fett. u. Harz. Ind._, 1904, 118-120 _et seq._) has
attempted to utilise the pancreatic juice on a technical scale, but the
process proved too slow and too costly to have any practical use.

_Rancidity._--The hydrolysing power of enzymes throws a good deal of
light on the development of rancidity in oils and fats, which is now
generally regarded as due to the oxidation by air in the presence of
light and moisture of the free fatty acids contained by the oil or fat.
It has long been known that whilst recently rendered animal fats are
comparatively free from acidity, freshly prepared vegetable oils
invariably contain small quantities of free fatty acid, and there can be
no doubt that this must be attributed to the action of enzymes contained
in the seeds or fruit from which the oils are expressed, hence the
necessity for separating oils and fats from adhering albuminous matters
as quickly as possible.

_Decomposition of Fats by Bacteria._--Though this subject is not of any
practical interest in the preparation of fatty acids for soap-making, it
may be mentioned, in passing, that some bacteria readily hydrolyse fats.
Schriber (_Arch. f. Hyg._, 41, 328-347) has shown that in the presen