The spectra also showed that the extraction with these low polarity
solvents causes no appreciable loss of glycerol and does not remove
methanol or sodium acetate, even though there was some water in
the extracted crude glycerin (Fig. 2). The substance entering the first extraction
step (extraction 1) contained 74% wt. of raw glycerin and 26%
wt. of other impurities (see Table 1). The refined substance after the
first extraction step corresponds to 92.1% wt. of the raw substance entering
the extraction 1, and has a glycerin concentration of 85.3% wt.
and 14.7% wt. of other impurities (refined 1). Based on the raw
substance entering the extraction 1, this represents the removal of a
total of (26–14.7/0.921)/26 × 100%=38.5%wt. of impurities. Those impurities
were mainly fatty esters and residual biodiesel.