Platinum Metals Review - Volume 17, Issue 2, 1973

The platinum metals do not react with most molten oxides and halides and therefore they have many applications in crystal pulling. They can be used not only for crucibles but also for heat shields and baffles to control both the spatial and temporal temperature distributions. The construction and use of these components is described in this article.

The standard of accuracy of all platinum: rhodium-platinum thermocouples produced by Johnson Matthey Metals Limited is extremely high. However, individual thermocouples for special purposes can be supplied to even higher standards of accuracy following their precision calibration by the National Physical Laboratory.

The tail gas stream from ammonia oxidation plants for the production of nitric acid contains nitrogen oxides, which present a pollution problem. These pollutants can be eliminated successfully by reduction with a fuel gas over Honeycat platinum on ceramic honeycomb catalyst, which has been developed and is produced by Matthey Bishop Inc. and Johnson Matthey Chemicals Limited. Such Honeycat installations in nitric acid plants are becoming numerous and widespread.

The original metric standard of weight adopted in 1799 was a kilogram fabricated from platinum. The presentinternational standard kilogram was made nearly a century ago from 10 per cent iridium-platinum. Johnson Matthey was deeply concerned with this work and since then has regularly supplied further national prototypes and working standards toastrict specification.