SURFACE ACIDITY OF COLORED BINARY METAL OXIDES By

Eighteen species of colored binary metal oxides were prepared and the acidities in their oxidized and reduced states were determined by back titration of n-butylamine benzene solution with hydrochloric acid. The acidities obtained by the back titration method have been shown to correlate well with those by usual amine titration method. All the colored oxides were found to have fairly large acidity above 0.14 mmol/g and 0.0015 mmol/m2, the largest acidity being found for Ti02 ·Fe203 in oxidized state. It was also found that most of the oxides decrease their acidities on reduction, whereas reduction increases the acidities of A120 3 · CdO and A120 3 · Cr203