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ON AN EXPEEIMENTAL MODIFICATION OF VAN DEB 
WAALS'S EQUATION. 
By John P. Dalton, M.A., D.Sc, Victoria College, Stellenbosch. 
Some years ago" the author pubUshed a complete table of 
saturation constants derived from the well-known van der Waals 
equation — 
and, by their means, investigated the reliability of the equation in repre- 
senting experimental results, especially within the saturation region. 
The equation was found, as expected, to give an excellent qualitative 
indication of the nature of the results to be expected under given 
conditions, while it completely failed to give any reliable quantitative 
estimates. Many modifications of the above equation have been proposed 
from theoretical considerations based upon assumptions more or less 
convincing, but the arbitrary nature of such assumptions seems to 
suggest that a direct appeal to experiment is to be preferred. In the 
following an attempt is made on the lines indicated by KuenenI to 
modify the equation experimentally, and the improvement effected is 
brought to light by comparison with such data as are at present 
accessible. 
(Eeceived October 11th. Eead October 15th.) 
§ 1. Introduction. 
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* J. P. Dalton : Phil. Mag. (6), 13, 1907, pp. 517-542. 
f J. P. KuENEN : Die Zustandsgieichung (Vieweg), 1907, p. 128. 
