The boiling point of sulphur corrected by reference to new observations on the absolute expansion of mercury

The very accurate observations of Eumorfopoulos on the boiling point of sulphur with an air thermometer of the type described by Callender gave a final value 443°·58 C., and appeared to cast some doubt on the value previously assumed, namely 444°·53 C. on the scale of the constant-pressure air thermometer. It was pointed out, however, by Eumorfopoulos, and also in a note appended by Callender, that the result depended on the assumption of Regnault’s results as recalculated by Broch for the absolute expansion of mercury, and that the final value could be readily corrected when the expansion of mercury had been redetermined by observations then in progress at the Royal College of Science. These observations have now been extended successfully to a temperature of 300° C. They will be published in full as soon as the final reductions have been made. But as the results exactly confirm the value previously assumed for the boiling point of sulphur, it appeared desirable to remove this uncertainty at the earliest possible date. So far as we are aware, no serious attempt has been made to redetermine the absolute expansion of mercury above 100° C. since the time of Regnault, and it appeared that with modern facilities for accurate measurement a considerable improvement on his work might be effected. The apparatus employed was designed and in part constructed at University College in 1900 while the experiments of Mr. Eumorfopoulos were in progress. The essential points of the design were as follows: In place of the single pair of vertical tubes 1·5 metres long employed by Regnault, six pairs of tubes, each 2 meters long, were connected in series giving a total length eight times as great.