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The specific heat of water vapour and the theory of the dissociation of water vapour at high temperatures

Published online by Cambridge University Press:  24 October 2008

W. H. McCrea
W. H. McCrea
Affiliation:
Trinity College
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Extract

The following is an attempt to account theoretically for the observed specific heat of water vapour. The usual theory of the vibrational specific heat together with the theory of the dissociation of the H2O molecule at high temperatures is found to account satisfactorily for the observed facts. It is shown, also, that at temperatures near 100° C. there is an effect due to polymerisation.

Type
Research Article
Information
Mathematical Proceedings of the Cambridge Philosophical Society , Volume 23 , Issue 8 , October 1927 , pp. 942 - 950
Copyright
Copyright © Cambridge Philosophical Society 1927

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References

* The Specific Heats of Gases (Benn, 1925), Table C.Google Scholar

* Phil. Mag. (7), 3, p. 273 (02. 1927).CrossRefGoogle Scholar

* Phys. Rec. XXI, p. 653 (1923).Google Scholar

* Fowler, R. H., Phil. Mag. (6), 45, p. 1 (1923).CrossRefGoogle Scholar

† I have calculated that, for the amount of dissociation found experimentally, the value of at 1700° K is very nearly .

* There is no simple expression for the energy levels when all the moments are unequal, but the form of r3 (T) must be very similar. If two of the moments of H2O are 3 and 1 × 10−40 the other should strictly be taken as 4 or 2 × 10−40.

† Darwin, and Fowler, , Phil. Mag. (6), 44, p. 450 (1922).CrossRefGoogle Scholar

* The Specific Heats of Gases, p. 178.Google Scholar

* Partington, and Shilling, , loc. cit., p. 169. [There seems to be a misprint in their final result for Dr, 0·449T occurring in place of 0·249T.]Google Scholar

* Zeit. für Phys. vol. 42, p. 396 (1927).Google Scholar

† DT is derived from the observed specific heat of steam and it would be better to use the calculated specific heat based on the elementary theory since we now see that a large part of the former is due to dissociation. The variation of DT with T is not, however, large.