Open AccessThe isotherms of CO 2 in the neighbourhood of the critical point and round the coexistence line
Author(s) -
Andreas Michels,
B. Blaisse,
Christoph Michels
Publication year - 1937
Publication title -
proceedings of the royal society of london. series a, mathematical and physical sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.814
H-Index - 135
eISSN - 2053-9169
pISSN - 0080-4630
DOI - 10.1098/rspa.1937.0114
Subject(s) - capillary action , capillary condensation , dew point , condensation , cylinder , thermodynamics , critical point (mathematics) , materials science , mechanics , mathematics , chemistry , adsorption , physics , geometry , organic chemistry
The isotherms of CO2 between 0 and 150°C. and up to 3000 atm. have been previously published by two of the authors (Michels, A. and C. 1935). The method used for these measurements was not suitable, however, for determinations in the neighbourhood of the critical point and the coexistence line. A second method has therefore been developed by which both the critical data and the coexistence line can be determined. This method and the results obtained are described in the present paper. The Method and Apparatus The method was based on the one developed by Michels and Nederbragt (1934) for the determination of the condensation points of a binary mixture. While, however, for the measurements of condensation points, it was not necessary to know the quantity of gas in the apparatus, this knowledge is essential for the determination of isotherms. A new apparatus was therefore constructed in which this quantity could be determined. A diagrammatic sketch showing the principle employed is given in fig. 1. In a steel vesselA , a glass bellB is suspended which is connected through the steel valveH and the capillaryJ to a cylinder containing a supply of the gas to be examined. A steel capillaryC connectsA with a second steel vesselD , placed on one scale pan of a balance. InsideD a steel tubeE , which is coupled toC , reaches to the bottom. The capillaryF is connected to the top ofD and leads to a cylinder of pure nitrogen and to an apparatus for measuring the gas pressure. The capillariesC andF are flexible, and are supported atG at such a distance from the scale pan that the variations in the forces acting on the latter during the swinging can be neglected. Before starting the measurements, the vesselsA , the glass bellB and the tubeC are completely, and the vesselD is partly filled with mercury. The valveH is then opened and CO2 gas admitted to the glass bell, driving mercury out ofA intoD . The pressure inD is balanced by nitrogen introduced throughF . When sufficient CO2 has entered the glass bell, the valveH is shut. As the filling operation is carried out at a temperature and pressure at which the isotherms of CO2 are known, the amount of gas inB can be calculated from a knowledge of the volume.