COMPLETE FREEZING-POINT CURVES OF BINARY ALLOYS. 
45 
sharp to the naked eye ; the upper boundary line was convex, the lower boundary 
quite straight. — 
At 54‘47 atomic per cents, of lead the ingot weighed 519 grams, while the sum of 
the weights of the metals used was 520 grams. 
The face cut on this ingot showed that the upper layer of lead-coloured metal was 
so thin as to be barely visible. The copper coloured layer had more grey in it, and 
was only 5 millims. deep. Its line of separation from the lower lead-coloured layer 
was somev/hat irregular. This grey layer formed the bulk of the alloy, being 
6 centims. long. 
As before, it had a reddish tinge from the spots of copper scattered through it. 
These were uniformly distributed, except near the top, where complete separation had 
not occurred. The copper tinge was less pronounced than at 24'76. 
At 53T5 atomic per cents, of lead the ingot weighed 312’5, while the total weights 
of the two metals come to 317‘4. 
As might be expected, this strongly resembled the preceding alloy, except that it 
was less homogeneous, cavities being visible, especially in the lead part, containing 
octahedral crystals of copper. 
At 80'3 atomic per cents, of lead the alloy weighed 427 grams instead of 430. 
This alloy was homogeneous to the eye, being lead-coloured throughout. In some 
lights the upper 2 centimetres had the faintest reddish tinge, but this detail was 
uncertain. Only a very few minute specks of copper could be detected even by 
careful examination with a lens. There were no cavities in the alloy. 
It will be noted, by comparison with fig. 9, that while the first three ingots 
which show separation into two layers correspond in composition to points on the flat 
part of the curve, the fourth ingot, which is homogeneous, corresponds to a point on 
the descending portion of the curve. 
