( -194 ) 



So for the teinporatiife. al wliicli tlic \a|Kiiir t('ii>ioji ciii-Ne ha> 



feaclicd it> iiiaxiiiiiim. llic /•-/-ciii-nc is asccmliiii;-. 



dp 

 Fiiiallv 1 sliall bi-ieHx- point out llial llu' xaliic for — al 1(51 , 



• ' dT 



calciilaicd fi-oiii the \a|»<iiir tension cnrxe liarnionizes well with the 



theoretical xalue ~. For the raii^e of teui[ieralnr(' between 15U' — 



170'', ƒ> may be fonntl from the following- inter|»olati(»n fonnnia 

 !> =/',,„ -f 5.5 (7— 15Uj — U.15 I/ — 1Ó0)'' 

 i"'or IGi follows from this 



du 



-^ = 2.2 

 dT 



and 



p lOul 



- = r= 2,3. 



T 434 



It follows from the coiislrnclioii that the /•-/-ciiiv c for the salu- 

 I'ated sobitions can ha\'e a maxininin, bnt ii is not easy to deduce 

 this theoretically. 



We «hall now contijine th(> discnssioji of liu. 4. 



If we take a conccnlratiun ./', \vith a \'olnnie .i\i\ and at tlic 

 tem|)('ralni'c for \\hich the tirst /•-./•-section holds, \\e arc in the 

 three-j)hase-triaiigle hfe, and so we have side by side N/j -\- I, -\- (1. 

 At the temperature foi- which the second /•-./•-section is drawn, the 

 poiiit /;, is no loiiuei- in the thi-ee-phase-1rian.üle, bin m the reuion 

 foi' >/; 4" ^'- ''"' li'p'id ha> iherefoi'e disa]>peare(l, and oidy solid 

 B -\- \aponr i>> left. 



At the tenipei'atnre corresponding to the third /'-,r-section the j)oint 

 t\ has retnrjied to the three-j)hase-ti-ianLzle and solid 7> -{- \apour 

 has therefore been [tartly converted into a li(pn(l. At the temj)ei'a- 

 ture correspondino- to the fonrth /•-,/-sectio]i the poijil /•. is fonjid in 

 the region of the nnsatnrated li(pnds with their \a|)oiirs and at the 

 nieltinu" point of the snbstance />, v, lies in the regi<»n of the 

 \aponi- and so e\ei'ything has exapoi'ated. 



If on the othei- hand we had started from die concenti-ation ;r.^ 

 w ith a \olnme .r., /•„, we shonld ha\e left the thi'ee-phase-triangle 

 with increase of tenijterature and we shonld have reached the i-egion 

 for SB-\-(jr, and have jtassed from thei-e straight into the gas- 

 region. As v.^ is sitnated above the r-t-vnv\Q /y//^, there is here nolhiiig 

 retrograde as in the case di.scussed abo^■c. It is obvions that the 

 retrogi'ade jdienonienon will occnr for conditions lying abo\e the 

 tangent drawn to the ^•-/-cnrve hh^ fi-om a cei'tain point ƒ (between 



