COMPLETE FREEZING-POINT CURVES OF BINARY ALLOTS. 
61 
straight line, the freezing point being constant at 954°. On this flat the freezing 
point of each alloy is marked by a prolonged period of constant temperature, but the 
character of each freezing point difiPers from that of a eutectic mixture, inasmuch as 
after a prolonged halt the temperature begins to fall again while some of the alloy is 
still liquid. With more than 65 atoms of lead the curve gradually droops and 
finally becomes nearly vertical. 
The character of the solid alloys, as described in the notes to Table IV., throws 
a clear light on the meaning of this curve. The sloping parts of the curve correspond 
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Degi’ees Centigrade and atomic per cents, of lead. 
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to the separation of solid matter from a homogeneous liquid, but for all alloys 
corresponding in composition to points on the flat, the liquid has separated into two 
conjugate liquids at some temperature above the freezing point. The composition of 
each of these two liquids will depend on the temperature, but provided there be 
more than 17, and less than 65 atomic per cents, of lead in the whole alloy, the 
quantity of lead present will not affect the composition of either conjugate, but only 
the amount of each conjugate present. Consequently all alloys between these limits 
are qualitatively identical, and therefore must freeze at the same temperature. The 
prolonged period of constant temperature noticed during the freezing of each alloy 
whose composition lies between these limits is easily explained. Let us suppose the 
