Elemental thermocouples, those whose thermo- elements are single elements, are not new and various combinations have been reviewed by Kinzie [1]. Interest in their potential was revital- ized as the period for formulating the International Temperature Scale of 1990 (ITS-90) approached. The Ptl0%Rh versus Pt thermocouple, the then existing interpolation instrument from 630 to 1064°C, was to be replaced by extending Pt resis- tance thermometry above 630°C and radiation pyrometry below 1064°C. As a result, realization of the scale in this temperature region would be improved by an order of magnitude. However, McLaren and Murdoek [2] suggested that compa- rable accuracy could be achieved with the Au