The preparation of the novel solid acid catalyst AlCl2(SG)(n), previously synthesized in CCl4, has been accomplished with a sealed-tube gas-phase reaction using an extended contact time. Reactivity studies and spectroscopic investigations indicate the similarity in the catalysts prepared via the two different methods. The hydration level of the silica support, prior to use in catalyst synthesis, is examined in this work. Excessively dry silica is deficient in surface silanol (Si-OH) moieties and yields an ineffective catalyst. Exposure of this dry silica to humid air allows sufficient hydration for the preparation of an active catalyst. Calorimetric titration and spectral studies-show that the Bronsted acidity of the solid gives rise to its strong acidity.