1369055 Purifying IC engine exhaust gases MUTSUI MINING & SMELTING CO Ltd 6 Sept 1971 [29 Sept 1970 14 Oct 1970] 41464/71 Heading F1B [Also in Division B1] Carbon monoxide and hydrocarbons in I.C. engine exhaust gases are oxidized in contact with a catalyst which consists of at least one manganese oxide together with at least one bismuth oxide with the optional addition of a lead oxide, alkaline earth oxide, silicon oxide, transition metal or transition metal oxide. Specified transition metals are Cu, Fe, Co, Ni, and rare earths, e.g. Y, Ce, La or Nd. In the Examples various catalyst compositions were used to carry out the oxidation at 300-550‹C with the introduction of secondary air into the exhaust stream.