High-temperature annealing requirements for Pt may be judged from the work of McLaren and Murdock [30]. When uniformly annealed at 1150°C, 1300°C or 1450°C the emf developed by Pt at the Sn point (~232°C) decreased, and the decrease tended to plateau at about 10 h. At this time, the measured emf was similar for all annea- ling temperatures and for l l50°C no further change was observed out to 44 h. For higher temperatures, the annealing effect continued, with a change of about -0.008 ~tV being observed per hour of annealing at 1300°C, for example. The measured changes are likely to be proportional to the temperature of measurement and so at this rate the effect of 100 h of further annealing at 1300°C on the emf at 630°C would be -2.2 IxV (equivalent to -110 mK for a Seebeck coefficient of 20 I~V K -1, see Fig. 2). Once again, to stabilize thermoelectric properties a uniform anneal for 10 h seems to be required.