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generation of heat, and when this conversion lias been completed, 

 the temperature falls on further withdrawal of heat and with internal 

 equilibrium the i-hombic sulphur moves along the line S, S3, which 

 is the continuation of S'S^. 



It is easy to see that the course of these lines for the solid 

 substance in internal equilibrium, is in agreement with the obser- 

 vation. 



The fact e.g. that the rhombic sulphur melts at a higher tempe- 

 rature according as it is heated rapidly from a lower temperature 

 can just as well be accounted for when we take this view of the 

 matter, as when we take that indicated bj^ fig. 1, for according as 

 we start from a lower point on the line S^ S,, we shall reach when 

 heating rapidly either the melting-point surface S'li'SJ^, or the 

 melting-]ioint surface S'L' >S'i/i at a higher temperature. 



It may finally be pointed out here that if we assume Sr and 

 Sm to be always in internal equilibrium, and Sy. to behave as a 

 true component, some more conclusions may be drawn from the 

 figure for this case than have been already discussed. 



Then the liquid line of the melting-point surface starting from 

 I^S^ will meet the region of non-miscibility at g^ and a second liquid 

 A3 will make its appearance. The solid substance ƒ, will coexist 

 with the two liquid layers, so that a three-phase equilibrium prevails 

 here, which is invariant if the pressure is assumed to be constant. On 

 withdrawal of heat g^ is converted to ƒ3 -[-A3, and at lower tempera- 

 tures the melting-point surface will be formed by the line /g^'s for 

 the solid phases and by the line hj^ for the liquid phases. 



An analogous remark may be made with reference to the melting- 

 point surface starting from SJ^. The liquid line of this surface meets 

 the metastable part of the region of non-miscibility, which starts on 

 the plane for Sn -{- S/j., so that also here we get a three-phase equi- 

 librium, which is metastable, and which is indicated by f^f/Jt^. 



Below this three-phase temperature the metastable melting-point 

 surface is indicated by the lines that run from /\ and h^ to lower 

 temperatures. If now the liquid lines intersect each other, as is 

 assumed here, this means that a liquid which coexists both with mono- 

 clinic and with rhombic mixed crystals, is found in this point of 

 intersection. It follows from this that also these mixed-crystal phases 

 are in equilibrium with each other, and so that they must lie on 

 the transition surface. 



So, as is at once clear, the three coexisting i)hases are found by the 

 meeting of the two melting-point surfaces and the transition surface. 

 Of the two melting point surfaces the liquid lines meet; this 



