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b and c and this line parallel to the /--axis is smaller than the area 

 between the branches a and b above this parallel line, Maxwell's 

 line would have to lie higher, and hence is not possible. A fortiori 

 the combination (</, d), which would require a still higher value of 

 the pressure of Maxwell's line, will be excluded. For similar reasons 

 the combinations (b, e) and u\ e) must be rejected. From this follows 

 that the (/-line which is of somewhat higher degree than that passing 

 through 1\ must remain on the left side before the point o of fig. 1, 

 and on the right side of the ridge of the vapour branch of the 

 binodal line. If we continue to raise the value of q, the possibility 

 of the combinations (a, c) and {a, </), begin simultaneously, i. e. when 

 the pressure of the point 3, which may be considered as the top ot 

 c and (/, has risen so high that the Maxwell line for the combination 

 (a, c) would just, go through point 3. In the same way the possi- 

 bility for the combinations {b, e) and (c, e) begins at the same time, 

 i. e. when the pressure of point 2, which is the lowest point of the 

 branches b and c, has descended so low, that the Maxwell line for 

 the branches c and e would just pass through point 2. If all these 

 possibilities exist, the twelve points can be pointed out on thé q-\me. 

 Which of these two simultaneously beginning possibilities presents 

 itself first on rise of the degree of the (/-line, will probably not be 

 bound to a general rule. If we now follow such a (/-line, beginning 

 ai small volume on the left side of fig. 17, we first meet point 2 

 on the binodal curve, which proceeds regularly from left to right 

 on the liquid side; then 6 and 5 follow before we pass through the 

 spinodal curve. When the (/-line rises again, we meet 4 and 3, 

 which have then to lie more to the right than on the (/-line, for 

 which tig. 17 has been drawn. When the (/-line again descends we 

 first meet point I, then 6, afterwards 5 and 4, and at last on the 

 vapour side the points 3, 1 and 2 in this succession. But of all 

 these points only the points 2 are stable. The points 1 and (i are 

 metastable. The others are unstable. And on further rise of (/ we 

 reach that special (/-line which is to be considered as the principal 

 one for the phenomena of coexistence, and which, with three-phase- 

 equilibrium, passes through the three coexisting phases. This co- 

 existence of three phases is met with when (see fig. 16) the Maxwell 

 line for the combination (a, c) is the continuation of the line for the 

 combination (c, a). At the same time this line is also the Maxwell line 

 for the combination [a, e). Then the points 1 and 2 or 2 and 1 coincide 

 on the vapour side. On the liquid side on the left the points 2 and 6 

 or 6 and 2 coincide, on the right on the liquid side the points 1 

 and 6 or 6 and 1. The points 3, 4 and 5 have remained; of them 



