Further experiments with liquid helium. B. On the change in the resistance of pure metals at very low temperatures, etc. III. The resistance of platinum at helium temperatures

Abstract

The resistance of a wire of very pure platinum at helium temperatures. As soon as the possibility had been attained, it lay at hand to extend to helium temperatures the investigation of the change of electrical resistance of sure metals that, in Comm. No. 99c (June 1907), had been brought down to the lowest hydrogen temperatures. For this purpose the resistance Pt _B which had been calibrated at hydrogen temperatures as well as at others with the resistance Pt _I of Comm. No. 996 (June 1907) was available It was constructed on the model of Pt _d (Comm. No. 996 § 2), and is indicated by Ω on Plate I of part A of the present paper, fig. 1. The thin platinum wire is wound round a glass cylinder and is kept tight on it by being wound while hot, and the thicker platinum ends W _a and W _b are fused to the glass. To these ends the double platinum leads $\mathop W\nolimits_{{a_1}}$, $\mathop W\nolimits_{{a_2}}$ and $\mathop W\nolimits_{{b_1}}$, $\mathop W\nolimits_{{b_2}}$ are attached; they are not, however, welded in the blowpipe, but are simply tin-soldered. The resistance was measured on the WEAT STONE bridge according to the method described in Comm. No. 99 and previous Communications The ratios of wt, the resistance at the temperature of the observation, to w₀, that at 0°C, are here given.