( 597 ) 

 dT dTy /•-! \ dT-, , 1 dh 



Tdx^ Tydx ' 2>c [Tyd.v f—lhd.v 



8 /•_ 1 9 



Witl) /"= 4 and x =z — we find ai>-ain '— - — = --, bnt with /= 7 

 -^ 3 ° 2x 16 ^ 



and x=— , '^^ rises to 0,8. With ƒ = 6,7 and x. = 3,56 (Keesom's 



vahies for carbonic acid) the valne is not appreciably different from 



dT, , 1 db 



0,8. If we calcnlate with— -= — 0,493 and -— = — 0,271, 



dT 

 r = 6,7 and x i= 3,56 the valne of 7--—, we find for this valne 



— 0,259. Thongh 0,259 is smaller than the values calcnlated from 



Keesom's observations, 0,284 for ,7; = 0, i 047 and 0,304 for .>■ = 0,1994, 



we mast not forget that the calculated valne wonld hold for the 



limiting case, viz ,v = ; and the fact that for A,i' = a smaller 



valne than 0,284 wonld have to be expected is at least in harmony 



Avith the circumstance that the amount is found higher for a higher 



value of X. 



It is evident from all tl is that though we cannot do quite without 



dT 

 the equation of state for the calculation of 777-— for the plaitpoint 



1 div 



line, yet it is not necessary to know the form of the quantity h. 



For the calculation of the quantitv r, ^oi' t'^e beginning of the 



' p dT 



plaitpoint line we have from the formula : 



J)'V JvT VÖ7' 



the relation : 



Tdp\ _ T /dp\ 1 rdp\ Tdx. 



or 



p dTJi,i p \dTji, p \dxjTu dT 



( dT, 1 1 db 



Tdp\ _ ~ ^''~^^ \Y^v ^ '{f^)b d^v 



p clTj^i * ' dT,. f~\ ( dT, 1 I dhy 



T,dx "^ "2>r i Tydx ^ (7^ b'd~v\ 

 or in numerical value for the mixture of oxygen and carbonic acid: 



T dp\ — h,l \— 0,493 - 0,047| 



- -£- = 6,7 + — 1-J '- i = 6,7 - 11,28 = - 4,58 



p dTj,A ^ - 0,259 



With the mixture x = 0,1047 Keesom has found — 6,3 and with 

 X = 0,1995 the amount found was — 6,08. 



