This method is for determining phenols and hindered phenols in petroleum fractions up to and including No. 2 distillates; e.g., gasolines, naphthas, kerosines, jet fuels, No. 1 fuels and No. 2 fuels. The procedure gives nicely defined titration curves and endpoints on samples up to No. 1 distillate, but No. 2 oils sometimes give titration curves with ill-defined endpoints. There is no way to predict this behavior, so the analyst must simply try it on the sample.
Phenols as hindered as butylhydroxytoluene (BHT) can be titrated directly using this method. Provision is included to overcome the acidity of mercaptans and thiophenols via a mild oxidation to the corresponding disulfides.
PHENOLS AND THIOPHENOLS IN PETROLEUM PRODUCTS BY SPECTROPHOTOMETRY, which can be used with accuracy on gasolines and on refinery caustic solutions.