oa Platinum and the Refractory Oxides

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.