Some Properties of Gold-Iron Thermocouple Wire

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Abstract
Gold wire with nominal 0.02 at.% iron manufactured by Sigmund Cohn has been calibrated vs Hoskins' Chromel‐P from 0.4 to 85°K. The high sensitivity of this dilute solution, its reproducibility upon cycling from room temperature, and stability upon aging were favorably confirmed. Thermopower variations on the order of 0.3% have been detected in spools of wire arbitrarily drawn from the 0.02 at.% bar. Thermoelectric emf measurements upon a recently cast nominal 0.07 at.% bar show potential variations smaller than 0.1%, thus allowing for accurate absolute temperature prediction from arbitrarily drawn wire. The Au–Fe thermocouple wire, particularly the annealed 0.02 at.% wire, is useful as an absolute thermometer down to 0.4°K owing to an anomalously high thermopower; however, individual lengths must be calibrated against a known standard if accuracies of better than ±0.05K° in temperature are desired below 1°K.