RECENT PROGRESS IN THE STUDY OF ALLOYS. 81 



liquid, which can exist in presence of each other without 

 change, may conveniently be termed conjugate. 



The above applies to experiments conducted at a con- 

 stant temperature. If we work at a higher temperature the 

 compositions of the two conjugates will be altered. In 

 general, raising the temperature will cause B and A to 

 become more soluble in each other ; so that the two conju- 

 gates approach each other in composition as the temperature 

 rises, until finally a critical temperature is reached at which 

 the two conjugates have the same composition, and, there- 

 fore, are indistinguishable from one another. At this and 

 all higher temperatures the system will consist of one 

 homogeneous liquid, that is to say, A and B will be 

 miscible with each other in all proportions. Conversely, 

 if A and B are mixed at a temperature above the critical, 

 and the resulting homogeneous liquid be gradually cooled, 

 a temperature will be reached at which the liquid will 

 separate into conjugate layers. If temperature be plotted 

 horizontally and the percentage composition of the mixture 

 vertically, the composition of every possible pair of conju- 

 gates will be given by points on a curve, as in figure i ; and 



r/& t 



.'00 



it 



K 



0- 



t 



30 



4« 



6o 



»o 



I 



Li 



C 



/oo 



106 



2C O 



JO o 



t*oo 



imp 



er>a/~ur»e. 



the two points lying on the same vertical will correspond to 

 a pair of conjugates. Every point in the area of the figure 

 corresponds to a definite state of percentage composition 

 and temperature, but the points, such as P, R, or S, which 



