Frederick Guthrie on Eutexia. 463 



liquefaction than that given by any other proportion. Here, 

 again, the cryohydrates completely satisfy the definition. 

 But it will be shown that they constitute only one term of 

 a series ; that their melting or liquefaction is quite continuous 

 with the so-called fusion of mixed metals or salts ; and that 

 the eutectic alloys of metals, many of which have been long 

 imperfectly known, and the eutectic alloys of salts, which I 

 shall describe (§§ 207-229), are the perfect homologues of the 

 cryohydrates. Let me, in a word, invite my readers, while 

 looking upon water as fused ice, to trace the analogy between 

 the behaviour towards solids of water on the one hand, and 

 some other fused substance on the other. 



Eutectic Metallic Alloys, 



§ 195. Metals mix with one another in various proportions 

 forming Alloys, many of which are in extensive use in the 

 arts. Amongst the most instructive aspects of alloys is cer- 

 tainly that which results from a comparison of the properties 

 of the alloy with those of its constituents. And, further to 

 specialize, the discussion of the relation between the tempera- 

 ture of fusion of the mixed metal and the temperatures of fusion 

 of its elements forms a chapter of the highest significance. 



§ 196. In studying this chapter, I employ Bismuth as one 

 of the elements on account of its low melting-point, and 

 because it can be got very pure. Fused bismuth will be the 

 homologue of the water or fused ice of my previous memoirs, 

 and the metal with which it forms alloys will be the homologue 

 of the salt. The bismuth used in the following experiments 

 melted at 263° C. 



§ 197. Bismuth and Zinc. — It has been asserted that when 

 bismuth and zinc are melted together two alloys are formed 

 which do not mix, the upper being an alloy of 2*4 bismuth 

 and 97*6 zinc, and the lower of from 8*6 to 14*3 bismuth and 

 from 91*4 to 85*7 zinc (see § 206). Such a condition and 

 such a ratio may accidentally exist ; but is only occasional. 

 Let bismuth be fused and heated to about 350°, and let as 

 much melted zinc be added in small quantities at a time as 

 the bismuth will form a liquid alloy with at about that tem- 

 perature. Let now the temperature be watched until it has 

 sunk to about 250°. The liquid is run off and a little bismuth 

 is added to the contents of the crucible, which is heated until 

 fusion ensues, and a second amount of liquid at 250° is again 

 obtained. This and the quantity obtained by the first process 

 are melted together and allowed to cool gradually. The 

 temperature sinks almost immediately to 248°, and remains 

 constant at that temperature. The alloy maintains the same 



212 



