View through the element of a catalytic converter, a device which reduces the toxic emissions from an internal combustion engine by converting the harm- ful exhaust by-products into relatively harmless ones. The inner surface is coated with an alloy containing platinum, rhodium and palladium. Oxidation catalysts convert hydrocarbons to carbon dioxide and water. Three-way catalysts convert oxides of nitrogen back into nitrogen. The addition of a catalytic converter to a car necessitates the use of unleaded fuel since the lead compounds added to regular petrol as anti- knocking agents can 'poison' the catalyst.