( 272 ) 



As ill this derivation of (11) from (9) the quantity h of the equa- 

 tion of state was supposed constant, (11) must only be considered as 

 an approximation. 



If for the present we keep to this form, (IJ) may also be written : 

 dT _ clTy 9 / tlT, 1 db Y 



TdtVg Ty d.Vg l<dyl\, d.v^ 3 hdx 

 And taking into consideration that b = -^r—^ — ^^'^ ^i"^^ finally : 



dT dr, / dT, 1 dp. Y 



Tdx^ Tydx^ \Ty,d.i\ 4^ p,. dx 



The quantity T, occurring in this equation, represents the critical 



temperature of tiie unsplit mixture. For this quantity I have already 



demonstrated in my Tiiéorie Moleculaire that it may get a minimum 



value for some sorts of mixtures — and the obser\ations of Kuenen, 



Quint and otiiers have furnisiied instances of the existence of such 



a minimum value. If the admixture should be of such a nature that 



such a minimum value existed, it would, of course, be perfectly 



dTy 

 absurd to substitute T... — T,. for — -. But the existence of such a 



dx 



minimum critical temperature is only to be expected, at any rate 

 oidy observed, when 2\ and 2\ differ little. Wlien they differ much, 



— - can be represented by Ty„— 1\ at least with approximation. As 

 dx^ 



I) depends on x linearly at least with some approximation, we may write 



\ db />/, />xi 



b dx^ Ty.j 



Let us with these approximate values compare equation (1) with 



Keesom's observations on the mixtures of carbonic acid and oxygen '). 



Tlie critical temperatures of these substances differ sufïiciently 



to enable us to use the approximate values. Ty„ (for oxygen) 



is namely about half of Ty^ (that of carbonic acid) — and 



dTy , , 154,2-304,02 

 so we put for — -— the value = — 0,493, and tor 



lydx^ c>U4,U-i 



154,2 304,02 



L— the value -^ ^^ or — 0,271. With these values 



h dx, 304,02 



72,98 



I) These Proc. YI, p. 016. 



