Platinum Metals Review - Volume 14, Issue 3, 1970

The exhaust gases emitted by diesel engines are frequently both a health hazard and a nuisance to the public. These emissions can be minimised by careful engine design but catalytic combustion provides a more effective method of purification. THT catalysts incorporating platinum have given excellent results in test units. They are suitable for diesel-engined road vehicles and for diesels working in enclosed conditions.

Metals of the platinum group are being produced in appreciable and growing quantities as by-products of nuclear fission in atomic reactors. It has been suggested that rhodium, palladium and ruthenium might possibly be separated in the reprocessing of spent fuel and be used in industry but from calculations recently made it is now shown that their levels of radioactivity would be unacceptably high and their use would entail a risk of contamination of world stocks of all the platinum metals. The growth of mining operations is expected to provide ample supplies of all the platinum group metals and there is no prospect of exhausting mineral resources in the foreseeable future.

Severe reactions can occur between heated platinum and the more refractory oxides when the oxidising potential of the surrounding atmosphere is reduced below a critical level. In the second part of this paper it is shown that the severity of these reactions is largely controlled by the surface area of the refractory and by the ability of oxygen to escape from the reaction zone. Alloying occurs predominantly by vapour phase processes. Under vacuum conditions complicating effects are introduced by platinum vapour particularly in the presence of steep temperature gradients.

The platinum metals featured in many of the researches reported and in the new devices described at the Fifth International Conference on Contacts, held in Munich in May. Nearly 600 workers attended and 22 countries were represented. A varied programme of papers dealt with both theoretical and practical aspects of contact behaviour.