Van der Waals equation reduced

In conclusion, it may be said that van der Waals equations can only provide reasonably accurate representation over limited ranges of variation of the pressure and temperature. For this reason many attempts were made to produce a more satisfactory equation by modifying vanderWaals equations. Such modifications were made by Berthelot (See item b ), Callendar (See item c-2), Clausius (See item C3), Dieterici (See item d2), Hirschfelder et al (See item 113), Keyes (See item ki), Lees (See item I3), and Macleod (See item mi) Accdg to Dunkle (Ref 17), for high temps and moderate pressures which give rise to large values of V so that P55>a/v2, van der Waals equation reduces to Abel s equation (See item ai)... 

This is the van der Waals equation. In this equation, P,V,T, and n represent the measured values of pressure, volume, temperature (expressed on the absolute scale), and number of moles, respectively, just as in the ideal gas equation. The quantities a and b are experimentally derived constants that differ for different gases (Table 12-5). When a and b are both zero, the van der Waals equation reduces to the ideal gas equation. 

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