Precisionization of Gas Thermometry

Abstract

In order to improve the accuracy of gas thermometry, use of a large bore precision manometer for pressure measurent is contemplated. The loss of accuracy by large dead space inherent to large bore manometer is covered by isolating the manometer with mercury seal in a small U-tube. Between this U-tube and the manometer an auxiliary gas bulb is provided with which the manometer can be set at any desired pressure. Thus, in temperature measurement, the manometer is first set at the pressure calculated for the expected temperature, then the mercury is withdrawn from the U-tube allowing the free passage of gas between the manometer and thermometer bulb. The difference in pressure, if any, before and after the withdrawal of the mercury is read. From this difference, accurate gas pressure is deduced with the least worries about the dead space. An example carried out by this method is shown.