£ 
Fig. 5. 
the first term of (3) will be large if as— »_ 
large, that is to say when the initial directions. 
of the branches of the melting diagram line differ 
greatly (Fig- S<*)- . ,. „ 
The second term of (3) the partial pressure of 
the component B will as a rule be greater ') when 
this component gets more volatile; as in the case 
of this chief type I we have assumed that ite 
triple point pressure is smaller than that of A 
we shall have the most advantageous conditions 
when they differ as little as possible. 
For the case la is, therefore, required 1. » 
i-ig. ji 0r caoo aw - L 
type of melting diagram with greatly diverging branches near the 
/1-axis and 2. about equal triple point pressures. 
Case lb (minimum pressure) makes two demands: 
fall, but followed by a rise; if this second demand is not fulfill 
we are dealing with Ie. This second demand means of course 
a small difference of the triple point pressures; the i^ ^mand a 
small P, is, therefore, in regard to the 
to the second and is, in consequence, determined alogetherbythe 
first term of (3). In order that this may be as small as possib 
is, of coarse, required that «-« shall approach 
possible, a demand which is complied with in a me!Iting d ag 
with branches almost coinciding in the initial direction. ( g- )_ 
We arrive at an identical result if we start from the triple pomt 
of B and examine the vapour pressure P, 0 a iqm , 
little of A, when that liquid can also coexist with a solid phase. 
In this case the relations (f), (2), and (3) become: 
Tt = Tl -^W-*t) .< 1Wl > 
1*,=pA+*LP'r, ■ . 
P\ = P'r, 
1 (xs — ^l) 
■¥pa 
(3bis) 
which will be readily understood on considering that the 
signs have the same significance for B as the non-accentuated ones 
had above for A. - - 
