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VI. Molecular Attraction and Attraction of Mass, and some 

 New Gas Equations. By James Kam *. 



SINCE the publication of my article, " A Criticism on 

 van der Waals' Equation, and some new equations 

 derived therefrom " f, I notice I have omitted an argument 

 without which the relation 2p c v c = constant and its deduction 

 cannot be understood. 



In submitting the explanation here, some repetition for 

 the sake of continuity of argument was unavoidable ; but 

 as the subject leads to entirely new expressions, and seems 

 to point to a general law ruling the cohesive forces, I publish 

 the results so far obtained under a new title. 



Introduction. 



The relation between pressure, volume, and temperature 

 during isothermal compression of a " perfect " gas is given 

 by the expression 



V 



the law of Boyle-Mariotte. 



For an actual gas according to van der Waals, the total 

 pressure IT (equal to the sum of the pressure p from the 

 exterior and the " Inward Pressure " pi) is expressed by 



if /3 is the t; co-volume " of the molecules of the gas contained 

 in v. 



The volume v is expressed in respect of v = l, 0° C. and 

 760 mm., and /3 is a function of v ; and it follows that for 

 the same pressure II but a temperature T 1? both v and ft 



T 



change at the rate y~. - 



The expression can therefore hardly be a correct version of 

 the physical process of isothermal compression. 



For suppose the same pressure II to be exerted at a lower 

 temperature Ti. Then the velocity of mean square c decreases 



T 



at the rate -Jf, i. e. proportional to the temperature. If the 



absolute value of v remains the same, the density increases 



T 

 at a rate smaller than -j^, say x times, and the co-volume 



* Communicated by the Author. 



t Kam, Phil. Mag. vol. xxxi. January 1916, p. 22. 



Phil Mag. S. H. Vol. 37. No. 217. Jan. 1919. F 



