Glycerol and spent lye clarification - Illinois Institute of Technology

of the lye removed from the kettle. The best
practice is to get about 90 *fo of the glycerine
in the stock into the crude. To obtain this
yield necessitates the removal of at least
three pounds of lye per pound of stock sapon-
ified, not counting any rosin that may have
been used.
If rosin and nigre lyes are used there
will be much coloring matter from the rosin
and nigre. All lyes will separate some soap
on cooling and a storage tank should be provid-
ed for the lye waiting to be heated and from
which the separated soap can be skimmed.
No lyes should be drawn from the glycerine
tanks in the plant contsning sufficient
strength to raise the average of all the lyes
to more than 0.4 ^ total alkalinity. This
low figure will result in a large saving both
in caustic soda in the soap factory and acid
used to neutralize the alkalinity of the lye
in the glycerine plant.
After the soap has cooled and all the