ISO 5274:1979

Specifies an acid washing test. Gives some indication of the degree of refining but does not give a precise measure of the amount of unsaturated compounds present as different unsaturated compounds produce different colourations with sulphuric acid. Shaking together of equal volumes of the sample and 95 % (m/m) sulphuric acid. Comparison of the colour of the acid layer with that of standard matching solutions.