Abstract
TWO papers on the psychrometer formula, re-orinted from recent Proc. Roy. Soc., Victoria (vols. xxiv. and xxv.), discuss a modification, proposed bv Dr. Ekholm, of the Stockholm Meteorological Office, to be made in Regnault's formula for the wet- and dry-bulb, hygrometer, which would have important consequences if confirmed. The formula so-modified would be x = ηf—AB(t-t′). where x and f are respectively the actual vapour-pressure and the saturation vapour-pressure at the temperature t′ of the wet bulb. A is the ordinary psychrometric constant, and η the coefficient, less than unity, inserted by Ekholm to allow for a supposed diminution of vapour-pressure at the surface of the wet bulb due to hygroscopic action of the material covering it. The first paper, by Dr. E. F. J. Love-and Mr. G. Smeal (Government research scholar), dealt with temperatures near the freezing point, and the second, by Mr. Smeal, dealt with temperatures up to 31·4°C. The discussions appear to have proved that the suggested coefficient, being so nearly unity, is not wanted, especially if the covering be thin muslin and be kept clean. The factor, A = 0·00072, derived from the observations and careful computations, varies slightly according to wind force. In the event of any modification of the simple formula being accepted it might be in this sense, but we suggest that it would be more to the point if one formula were selected from among those which already exist, and be recommended for general adoption.
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Atmospheric Humidity and Temperature . Nature 91, 69–70 (1913). https://doi.org/10.1038/091069b0
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DOI: https://doi.org/10.1038/091069b0