This method is for determining the concentration of acid oils inrefinery caustic. Part A separation of the acid oils by gravity, isa rapid determination for control purposes. The acid oilconcentration range which can be determined is from 1 liquid volumepercent (LV-%) upward, with no maximum limit. Part B separation ofthe acid oils by extraction, is reserved for a more precisegravimetric procedure as well as a volumetric measurement. It isapplicable to caustic samples containing as little as 0.1 wt- %acid oil.