i guess if it is distilled all bacteria that could be in the compound will be denatured and killed, but if you mean how are contaminants removed, solid contamination can be filtered out where as liquid contaminants can be distilled away
Glycerol is miscible in water and ethanol. It is insoluable in ether, benzene and chloroform.
Check the Merck Index or Hawley's Condensed Chemical Dictionary