XI. On the high-temperature standards of the National Physical Laboratory: An account of a comparison of platinum thermometers and thermojunctions with the gas thermometer

Abstract

In a paper “On the Comparison of Gas and Platinum Thermometers,” read before the Royal Society in 1900, Dr. P. Chappuis and the author described a series of experiments in which several platinum-resistance thermometers, constructed of wire of specially high purity, were compared with the gas thermometer at a number of steady temperatures from below zero to above the boiling-point of sulphur, and in one set of measurements to just short of 600°C. The results were such as to substantially confirm the conclusion of Callendar and Griffiths that the indications of platinum thermometers may he reduced to the normal scale by the employment of Callendar’s well-known difference formula d ≡ T- pt =δ [(T/100) ² - T/100] where d = the difference between T, the temperature on the normal scale, and pt = the “platinum” temperature. The constant δ for pure platinum wires is approximately 1.5, the three temperatures chosen for its determination being 0°, 100° and the boiling-point of sulphur.