Platinum Metals Review - Volume 16, Issue 3, 1972

Stringent regulations governing automobile exhaust emissions are due to come into force in the United States. Johnson Matthey have undertaken the development of platinum-based catalytic reactors for control of these exhaust emissions. Two new types of catalyst have demonstrated the feasibility of exhaust control by catalytic means, and have been incorporated on test vehicles to achieve emission levels well below the specified levels for 1975 and 1976 model year cars. Extended road mileage on the former system has shown that good durability can be obtained, with emissions below 1975 limits for 25,000 miles.

Accurate correlation between the purity and the properties of platinum is essential both to quantify the properties of the metal with a view to its practical applications and to establish the behaviour of platinum as a representative metal for various physical and chemical measurements. The authors of this paper describe the systematic purification of a platinum bar by vacuum-melting and zone-refining. The final residual resistance ratio obtained was very high. The purity of the platinum, as indicated by optical and mass spectrography, then compared well with the best values previously reported.