On the absolute expansion of mercury

Abstract

Regnault’s experiments on the absolute expansion of mercury were reduced by Wüllner, and subsequently by Broch. Their reductions differed by nearly 1 per cent, at 300°C. Regnault’s own reductions differed by nearly 1 per cent, from either at 40°C. Chappuis’ later determinations by the weight thermometer method, which were not absolute, agreed, fairly well with Wüllner’s reduction of Regnault at low temperatures, but differed from Wüllner in the opposite direction to Broch by more than 2 per cent, when extrapolated to 300°C. The object of the present investigation was to repeat Regnault’s method on a larger scale with modern appliances, and the apparatus was designed to secure an order of accuracy of 1 in 10,000, or 0·01°C., which, it is believed, has been substantially attained. The principal modifications made in Regnault’s apparatus were as follows: —(1) In place of the single pair of hot and cold columns, each 1.5 metres long, employed by Regnault, six pairs of hot and cold columns, each nearly 2 metres long, were connected in series as a multiple manometer, giving nearly eight times the expansion obtainable with Regnault’s apparatus.