Page:Outlines of Physical Chemistry - 1899.djvu/74

 ��OUTLINES OF PHYSICAL CHEMISTRY

��necessary to point out that the values of a and b depend on the nature of the gas under examination.

Application of the Equation. — In order the better to un- derstand these theories let us take an example, and again we shall choose Andrews's observations on carbon dioxide.

It has been found that Van der WaaWs equation con- veniently expresses the behaviour of gaseous carbon dioxide

��6/2 -

���so-

��if we put a = 0-00874 and b = 0-0028. At 0°C. and under one atmosphere pressure we should have :

��which gives for r the value

��At the temperature t°G. the equation will be :

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��(

��, + !<«») (, - 0«BS) = !™» x (278 + .).

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