22 Mr. J. Kam on van der WaaW Equation and 



Take a cubic centimetre of the mixture of m 1 grams of 

 dry air and m 2 of aqueous vapour ; and let heat be supplied 

 to raise the temperature 80 degrees, without change of 

 volume ; denoting by C the S.H. of the mixture at constant 

 volume, 



(«! + m 2 ) C 80 = m lCl 80 + m 2 c 2 80, C = m ^ + m * c * . ( 2 ) 



m 1 + m 2 



and similarly, if K denotes the S.H. at constant pressure, 



nil + m 2 ^ ' 



Also for each constituent gas respectively, with gravitation 

 measure of the pressure, 



^i pi w^c, ?z x 2 m 2 c 2 u 2 2 ,. 



V = <m*i = </-£;> ^=1T7' ^ = -17 7' (4) 



and for the mixture, 



p-&¥^ -*,+*, (5) 



ffljCi ^x 2 7?l 2 C 2 W 2 2 



<7 C W]+m 2 mxCi + m^z m 1 + m 2 ^ ' 



the special case for two gases of Niven's general formula, 

 derived in the same way. 



The Smithsonian Tables will provide the numerical data 

 from which U can be given in a tabular form from p, m, c, k 

 of dry air, and aqueous vapour of given saturation. 



1 Staple Inn. W.C. 

 Oct. 1915. 



II. A Criticism on van der WaaW Equation and some New 

 Equations derived therefrom. By James Kam *. 



Preface. 



IN the following deductions I take it for granted that the 

 factors a and b of van der Waals' equation have the 

 effect : 



The factor a of diminishing the gas-pressure towards 



the exterior with a value P 2 = ™ , the " Inward 

 Pressure " ; 

 The factor b of increasing that pressure at the rate 



* Communicated by the Author. 



