Determination of aluminum oxide in and on high-purity aluminum by a phenol dissolution method

A simple rapid determination of aluminum oxide in aluminum is described. Aluminum reacts with phenol at 180°C forming aluminum phenoxide but aluminum oxide does not. After the reaction, the aluminum oxide is filtered off and brought into aqueous solution by fusion with potassium hydrogensulfate for determination by atomic absorption spectrometry or by the 8-quinolinol spectrophotometric method. The reaction between aluminum and phenol is stoichiometric. The procedure is applicable to the determination of aluminum oxide in commercial aluminum metals of various forms. The method is relatively rapid and appears to be superior to the conventional bromine—methanol method.