A method for determining the acid value of oilseeds. A reagent kit for the rapid extraction of the free fatty acids from oilseeds which consists of reagents: "A" and "B". Reagent "A" contains a tertiary amine (such as triethanolamine) in water and an alcohol-hydrocarbon mixture as solvent. Preferred is water/isopropanol/heptane. Reagent "A" allows rapid (1-2 min) solid-liquid extraction of the free fatty acids and some other acids from oilseeds. Reagent "B" contains a strong acid and an inorganic salt in water. Reagent "B" enables the rextraction (liquid-liquid; about 5 min) of the free fatty acids only into a separate hydrocarbon phase, which can be used for the acid value determination.