RECENT PROGRESS IN THE STUDY OF ALLOYS. 83 



of the conjugate alloys of pairs of metals at the temperatures 

 at which solidification commences ; in other words, of the 

 solubilities of the two metals in each other at the commence- 

 ment of solidification. The writer is disposed to think that 

 these solubilities at the freezing point, the eutectic * alloys 

 in fact, give the limiting proportions in which the metals 

 can be usefully alloyed for metallurgical purposes. A few 

 of these solubilities have been published by Heycock and 

 Neville, but as yet only one conjugate of each pair has been 

 studied, and the metal pairs most useful in metallurgy, such 

 as copper-tin, copper-zinc, and copper-aluminium, have not 

 been discussed. A careful studv of the coolinsf curves ob- 

 tained by Roberts Austen would perhaps give us these 

 solubilities. 



Conjugate solutions, such as those above described, have 

 been found by Konovalow 2 to possess a remarkable pro- 

 perty. It is this, that if either or both of the components 

 be volatile, then the vapour given off by each of the two 

 conjugates is identical in pressure and in composition, 

 though the two conjugate liquids may be very different 

 from each other. Consequently the two conjugates would 

 begin to boil at the same temperature. This property is 

 not at present of importance in the case of conjugate alloys 

 on account of the low vapour pressure of the metals at the 

 temperatures we can command ; but, as Ostwald has pointed 

 out, a corresponding property as to the temperature at which 

 a pair of conjugates would refuse to dissolve either of the 

 metals in the solid form may be important. It seems pro- 

 bable from theoretical considerations, that if the pair of 

 conjugate alloys be formed at so low a temperature, that 

 one of them is saturated with the solid metal A ; then the 

 other conjugate is also saturated with A at the same tem- 

 perature. If heat is now subtracted from either conjugate 

 the first result will be the same, namely, the precipitation 

 of solid A. Continued abstraction of heat will, however, 

 affect the two alloys differently — that richest in A will be 



1 That mixture of two substances which has a lower melting point than 

 mixtures of the same substances in other proportions is said to be eutectic. 



2 Loc. cit. 



