490 



llic coiicciitralioii of' llio lifjiiid jiiid n^ lliosc lor tlif \ iipoiir (-(Kwi^liiiu 



with this li(|iii(l. Iii iuMitioii llic relation l)et^\■eell the \dluiiies of 



liiliiid and vapour inav he read tVoiii ihe pieces, iiilo wliich the 



linnid "i'"i 



[toint /•. divides tlie iiodal line: it is \iz. = . 



vapour It i\ 



With a t'oncentialioji .r., and xolnnie .r.,r,^ we ai-e in the i-e,üion 

 Sn-\-(T; the mol. \()ls. and the coiicentratioii of tiie \ ajioni- coexistiiij^- 

 with solid Vj, are denoted hv /•, ; the relation of llie xolnnies hy 

 solid "i^i 



vaponr f v.. 



If we now take a concentration ./■, with a \olunie r, i\, we are 

 in the three-phase-triajiüle. The mol. vols, of the three phases ai'e 

 indicated l)y the three anules; the i-elati\e volumes are found \)\ 

 lirawing- a line from / tlii'ouüii /•.,, till il intei'sects liie line /)t\ 'J'he 



solid ^'-^\ liquid hn^ 



relation t—. =:-;'- ;iiid the relation = — '- . If tinally 



Hqnid-\-vapoiir y r, vapour m, 



we have a concentration ./,, with a volume ./,, /\, we are in the region 

 lj-\-Sr,; tlic mol. vols, of the coexisting phases are now expressed 



liquid '"4 "'4 



l»v //, and ii\, the rela1i\e (luanlities Iteinu' indicated i>v — ,.tt^ = • 



^ ^ - ■ solid B v^fi^ 



When the leni|)erature rises, this /-.r-section snlfers a change; in the 

 llrst place the curves u// and Ar uvq moved lowei' and the curxcs 

 (/e ajid I't' are moved u|)ward. The displacement of the ]»oint /' 

 however is vei*y >mall compai-ed with the other (lisplacemeiU>. 'i'lie 

 points A and r are also moved to the right, because the >olultilily 

 of li in A is supposed to iticrease with rise of temperature. 



These are the (dianges for the case that we are still below the 

 critical leniperature of A: when wo have reached this temperature, 

 llie cui'\-es /jii and cd pa>> without a break into each (dhcr au<l 

 with rise of temperatiii'e ii|> to I he melting |)oinI of />' we get a 

 -eiMt'-- of conditions represented in Fig. 4. (p. 4i)l). 



The !>iiiodal cui'xcs />/',■ with llie plail|)oints in /' lie all inside 

 each oilier: they caunol i»e |ir(tloiige(l to ihe /> >idc liejiiw ihe 

 melting temperature of />, because the substances J and /i become 

 nnscible in all pi-opoi-liou> only al the melting point of /i. .lu>i abox'e 

 the critical lemperaiui-e of A ilie iioflal lines for the saturated \apours 

 and li(pii(U liaxc a slroniily >laiuiuü position; al liiiihei' U'inpei-aluro, 

 howexer. diey slant les>. because the dill'ertMici' iu couceulialion 

 i>etweeu A and r bec(tmes smaller. 



The cur\e l> l>J>J>i is the /--/-cuive for the .saturated \ apours, the 



