Glycerol and spent lye clarification - Illinois Institute of Technology

means must be employed to render them insol-
uble. This is best accomplished by the
addition of metallic salts, forming insoluble
metallic oompo-unds, which are coagulated when
the lye is neutralized.
The chief aim in using a metallic salt
in the purification of soap lyes is the removal
of the soaps of the lower fatty acids, formic,
acetic, butyric, caprylic, etc,.
The amount of aluminum sulphate to be
used depends on the cleanliness of the lye
and its freedom from soap and gelatinous
matters. The least amount that will give a
good cake in the filter press and not gum the
cloths is the amount to use. This salt can
bo added either dry or dissolved in water and
will neutralize about one third its weight of
caustic soda. An exoess of caustic soda in
the lye has the tendency to form aluminum
hydrate which will retard filtering.
There are anumber of compounds on the
market for which special advantages in lye