II. A comparison of platinum and gas thermometers, including a determination of the boiling-point of sulphur on the nitrogen scale. An account of experiments made in the laboratory of the Bureau International des Poids et Mesures Sèvres

Abstract

In a paper entitled “ The Practical Measurement of Temperature/’ read before the Royal Society in 1886, Professor Callendar drew attention to the method of measuring temperature based on the determination of the electrical resistance of a platinum wire. He showed that the method was capable of a very general application, and that the platinum resistance thermometer was an instrument giving consistent and accurate results over a very wide temperature range. Callendar pointed out that if R 0 denote the resistance of the spiral of a particular platinum thermometer at 0°, and R 1 its resistance at 100, we may establish for the particular wire a temperature scale, which we may call the scale of platinum temperatures,such that if R be the resistance at any temperature T° on the air-scale, this temperature on the platinum scale will be R-R 0 /R 1 -R 0 X 100°. For this quantity, Callendar employs the symbol pt , its value depending on the sample of platinum chosen.