164 



ELEMENTS OF /IPPLIED MICROSCOPY. 



below that temperature. , The relation of these various 

 points is made more clear in Fig. 59, in which the outer 

 limits of the oblique lines represent the fusing-points of 

 pure silver and copper. 



Fig. 59. — Curve or 'Solidification for Alloy of Silver and 

 Copper. (After Sauveur.) 



The alloy of such composition as to show but one point 

 of solidification, the lowest one possible for any mixture 

 of the metals concerned, is known as the eutectic alloy. 

 From any other mixture the metal which is in excess 

 crystalUzes out first" until the proper proportions are 

 reached for the formation of the eutectic. Similar phe- 

 nomena are manifest in ordinary solutions, and the solu- 

 tion of such strength as to show a single minimum freezing- 

 point is called the cryohydrate. 



