Glycerol and spent lye clarification - Illinois Institute of Technology

With the agitator (air) in action a portion of
the acid is added - enough to just talre up the
free caustic - then add the aluminum sulphate.
After the chemical is well mixed in the lye
should be alkaline. Now enough acid should
be added to just carry the lye to the neutral
point or perhaps to the point of acidity as
indicated by the faint pink of the litmus
paper. Care should be exercised to thorough-
ly agitate the lye during all stages of the
treatment, stirring making the liquor uniform-
ly acid or alkaline as the case may be.
Agitating or stirring seems to facilitate a
more readily "setable" precipitate.
All lyes will contain nitrogenous matter,
the amount varying with the care used in
rendering, Tfhen lyes are thus treated this
is not removed, most of it appearing in the
crude, increasing the figure for non-volatile
orgajilc residue. If the lye is made alkaline
before evaporation this nitrogenous matter
partly decomposes and gives off ammonia gas.
11