( 55 ) 



also a linear function of x. We shall further demonstrate this in 

 § 6, and show that in the case of such mixtures: 



a. o) is a linear function of x 

 0. V ,, ,, ,, ,, J, J, 



a 



C. 



d. the heat of mixing is = 0, 



o 



so that we may say : ideal mixtures are such for wliich the heat 

 of mixing is practically = 0, or ivith which no appreciable contraction 

 of volume takes place, when 1 — x Gr.mol. of one component is 

 mixed with x Gr.mol. of the second. 



The conditions a, b, c and d are sinmltaneously fulfilled, when 

 the critical pressures of the two components are by approximation 

 of the same value. 



3. For to — X rr- we may now write oy^, as a =z{l — x) io^ -|- 



ox 



ö'o> r _ , dto 



-j- tC (Oj, when - — = 0. Otherwise evidently to — x—-z=zv)y^ — 



- ^''A^J, - ''' "' \M)r ' ' J ^'' '^" '"""' '"""^ " " " èx='^' 

 and we get : 



f*i ('^-i/^) = C'l - «>i + p^'i + ^^' % (1 - '^O j 

 f^i (ö»i>o)= <^i — ">i +Po^i ' 



always when v^ and lo^ are supposed to be independent of the 

 pressure. For else tOj and z'l would have another value at the 

 pressure p than at the pressure p^. We must therefore also suppose 

 that our liquids are incompressible. But there is not the slightest 

 objection to this supposition for ordinary liquids far from the critical 

 temperature (and there is only question of such liquids in discussions 

 on the osmotic pressure). Onlj' when x draws near to 1, and so the 

 osmotic pressure would approach to go, v^ (and so also coj must no 

 longer be supposed to be independent of j>. 

 By equating these two last equations, we get : 



pv, + RT % (I — x) = p,t\, 



hence 



