In the long gap between the boiling point of sulphur (444°60 c.) and the freezing point of gold (1063° c.) there is no fixed point which can conveniently be used for the routine calibration of thermocouples in terms of the International Temperature Scale. The boiling point of selenium (about 690° c.) is suggested as a possible fixed point in this region, and as a first step towards enabling it to be used for this purpose the precise determination of its value has been undertaken. The determination was carried out in a silica boiling tube similar to that normally used at the sulphur point, having a re-entrant tube fitted with a radiation shield. By connecting the apparatus to a reservoir the variation of the boiling point with pressure over the range 700 to 800 mm. of mercury was also determined. The measurements were made by means of three standard platinum vs. platinum-rhodium thermocouple

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freezing point international temperature calibration of thermocouples platinum vs platinumrhodium thermocouple silica boiling tube reentrant radiation sulphur 444img srchttpejioporgiconsentitiescenterdotgif altcenterdot alignabsmiddle gold

M de Selincourt,.The boiling point of selenium. 52 (3),348.

M de Selincourt,"The boiling point of selenium" 52

M de Selincourt,"The boiling point of selenium"