Shinku

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In the previous paper, it is reported that it is impossible, due to a lack of reproducibility of the capillary depression, to measure pressures accurately in the range of 10^-5 Torr with the McLeod gauge without remarkably increasing the volume of the compression bulb. However, the construction of a gigantic McLeod gauge having the bulb volume more than about 2, 000 cm³ is presumably impracticable. A new gauge devised here consists of two bulbs of about 1, 000 cm³ each in volume, one of which is used for art ordinary gauge, and the other for accumulating the gas into the ordinary, bulb as the Toepler pump. (the gauge is illustrated in Fig. 3.) P_n, the pressure after the n th accumulation of gas, is, given by
P_n/P = bⁿ+ab (1-bⁿ) /V_M (1-b) …… (5)
where a = V_T + V_BD ; b V_M/ (V_M + υ _BD+ υ _DC); P is the pressure to be measured in the system ; V_M is a bulb volume above C ; and V_T is a volume between A and B. The result have revealed that the pressure measurements can be made with accuracies of ± 4% at 1 × 10⁵ Torr and ± 6% even at 6 ×10^-6 Torr. The achievement of this paper shows an improvement on the accuracy of the standard McLeod gauge which has been installed as the Vacuum Standard in the Electrotechnical Laboratory.

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