Catalysts prepared from (a) 3% and (b) 1.5% Pd/C (Siberian active C, similar to390 m(2)/g, impregnated with PdCl2): (a) 4.3, 5.2, 6.4% (redox method) and 6.5% (capillary impregnation) PdxAu(100-x)/C (x = 80, 70, 60, 60), (b) 2.2, 3.2 (co-impregnation with aq. NH4AuCl4), and 2.7% (redox) (x = 80, 60, 70 atom %), resp., and activated 3 h in H-2 at 400degreesC, were studied by chemisorption of H-2, temperature-programmed hydride decomposition (TPHD), and X-ray diffraction (XRD). Both TPHD (20-120degreesC) and XRD showed in series a and b the degree of alloying to be higher (though not ideal) in the redox-method than in the impregnation-method catalysts, thereby instrumental in preparing high-selectivity hydrodechlorination (of freons) catalysts. Two more catalysts, 0.3 and 2.77% Pd/gamma-Al2O3, (A) heated 8degreesC/min in 10% H-2/He up to 300degreesC, and/or (B) heated 0.5 h in O-2 at 300degreesC, washed with He at 300degreesC. reduced with H-2 17 h/600degreesC, and washed with He 1 h/600degreesC, were studied in thermal desorption of pyridine. Treatment B resulted in similar to50 and similar to30% more pyridine desorbed from catalysts A, B, and carrier gamma-Al2O3, resp., presumably on account of the stronger acid sites generated. Unlike from gamma-Al2O3, desorption from the A and B at >400degreesC gave plenty of H-2 owing to decomposition of pyridine to an extent apparently related to the Pd%. 33 refs.