consequently 



"<.7-,(2-.7vr[2(2-.7;,)(l-ö%(l-.l'c))-3<>.re] • • • ^^ 



If, therefore, « = or ]> than this vahie, then -^ becomes on 



o.v 



one or two places on the meltingpoint-line. 



dftj 

 Jbrom the expression foi' y- (see above) it follows immediately, 



I hal when A, and consequently «, should be neqative, ^-^ can never 



Ox 



become 0, still less positive. The occurrence of /^«.v^/7>Ar' conditions on 



the meltingpoint-line may, thei'efore, only be expected in the case 



of jtositive a, and oidy then, as soon as « reaches or exceeds the 



value, given by (/>). 



The i-elations {a) and (/;), Avhen united, give therefore the con- 

 dition for stable phases along the entire meltingpoint-line. 



In our example r =i — 0.74, and (*^7) gives ,Vc = 0.863. Tlie equa- 

 tion (/>) further gives with /7 = 0.396 : 



— 27X0,396X(0,137)^ 



" <0,863x(l,137f [2X1, 137(1 — 0,396 Zor/O,137)-3XO,396XO,863]' 



that is to say 



— 0,180 — 0,180 — 



« :^ or -^ — or -:p 0,0592. 



< 2,274x1,787 — 1,025 < 3,04 < ' 



Now, in our case a was 0,0453, so that everywhere we find 

 ourselves in the stable region (as may in fact be seen from the 

 shape of the observed meltingpoint-liiie). If « had been 0,059, we 

 should have had a point of intlection with horizontal tangent ; and had 

 « been 0,059, we should have noticed the occurrence of a horizontal 

 tangent in two places of the meltingpoint-line. This last case is, of 

 course, not realisable, as the liquid amalgam would break up into 

 two heterogenous liquid phases of different composition. ^) 



1) It is perhaps not devoid of importance to observe, that when the solid phase 

 forms a solid solution of the two components, the presence in the meltingpoint- 

 line of a point of inflection with a horizontal tangent points as before to ^instable 

 conditions. Fov in the general relation 



