RESONANCE RAMAN-SPECTROSCOPIC STUDIES OF PH INDICATORS ADSORBED ON GAMMA-AL2O3

Resonance Raman spectra were recorded from methyl red, ethyl red and a lpha-naphthyl red adsorbed from toluene solutions on to gamma-alumina. The spectra shaw clear evidence for the protonation of all three indi cators. Adsorption data over a wide range of equilibrium concentration s give satisfactory fits to Langmuir isotherms. Together with the spec troscopic data, the isotherms permit the determination of the densitie s of Breasted acidic sites on the gamma-alumina surface. The densities of acidic sites decrease after calcination at 300 degrees C.