Attraction of Mass, and some New Gas Equations. 85 



and give p c , c , and — the values given bv equations (17^ 



Vc 1 



and (19) for T<273, and^c, ct c , and — the values o£ equa- 

 tions (22) and (23 a), we obtain at once 



1 2 

 * + - 2 = -, (G) 



n 2, n v ' 



a quadratic equation in which all constants belonging to a 

 particular gas have disappeared. 



The corresponding cubic equation is 



e + \ = — , (GO 



rr n — q v ' 



in which 



9. = 



n 



,n 



V 



but which for given values of n at once converts into the 



-quadratic form. 



For every value of e we have two values of n x and n 2 , 



denoting the volume of the saturated vapour n 1 v C) and of the 



liquid the moment all vapour has been liquefied. At the 



de 

 vertex of the curve for which — = 0, the two values of n 



^coincide, and 



n = 1, 

 e = 1; 



i. e., p = p c , v = v c . 



Giving e successive values for the same gas, then 



n x v c is the volume of the saturated vapour, 



n 2 v c is the volume of the liquid thereof, 



at the pressure ep c , the vapour-pressure. 

 * Giving e the same value for various substances, then the 

 volumes at the saturated-vapour pressures e . p c must be 

 -equal multiples of n Y . v c and n 2 . v c , I have not yet verified 

 the latter deduction. The former I have examined for 



pressures of 1 atmosphere. Thus for e= — : 



Solving equation (G) we find 



*-HH}' <»> 



;■ = ;-{'.-.-}' « 



and must obtain such values for n that for the vapour 



