soda converts the non-hydratable phosphatides into sodium salts, which are less oil soluble. The free fatty acids are converted into sodium soaps which improve, in combination with intense water washing, the efficiency of phosphatides removal. However, the drawback of this caustic pre-treatment is the production of high quantities of soapstock which needs to be treated accordingly. Practically, the non-hydratable phosphatides are activated by adding 0.03% to 0.1% (w/w) of concentrated phosphoric acid to the crude oil. In order to avoid emulsion, the quantity of caustic solution is
calculated based on the initial free fatty acid content with some excess (10–30%) and a 20–22° Be caustic solution is thoroughly mixed to the oil at 90–95°C.