644 



RICE 



ART. L 



51 . Some General Ideas and Definitions Concerning the Possibility 

 of a NeiD Homogeneous Mass Being Formed at a Line 

 of Discontinuity or at a Point of Concur- 

 rence of Such Lines 



Of course bulk phases might develop at a line of discontinuity 

 or at a point where such lines meet. Gibbs considers the first of 

 these possibilities in the subsection beginning on page 289, the 

 second in the subsection beginning on page 297. The argument 

 in each case runs on very much the same lines as in the treat- 

 ment in pages 258-264 of the possible formation of a new phase 

 between two phases, although it might not appear so on first 



B 



Fig. 6 



reading. We shall recast the argument in pages 289-297 so as 

 to bring out this feature. 



First of all there must be certain relations between the surface 

 tensions in order that the problem may not be trivial. In the 

 first instance aBcit, n), crcAit, m), o-^b(^, M),must satisfy conditions 

 of equilibrium, which necessitates any one of them being less 

 than the sum of the other two. Now we assume that we know 

 of a phase D and that we know for it the functional forms of 

 (TAoit, fi), (TbdH, m), (Tcoit, m) as well as Voit, m)- The values of 

 (Tbc, <rcA, (Tab determine the angles at which the surfaces B-C, 

 C-A, A-B meet where no phase D exists. If the phase D is 

 formed and is in equilibrium, (Tad, obd, (Tab will have to satisfy 



