COMPLETE FREEZING-POINT CURVES OP BINARY ALLOTS. 
33 
points of this series. A probable explanation is that the silver was not fully molten 
at the moment of adding the first and second cjuantities of copper, and so the solution, 
whose freezing point was taken, was at the time richer in coj^per than the figures 
indicate. 
At 16 atoms, precipitate begins to form at the freezing point and can be watched 
forming freely as the mass slowly falls in temperature. 
At 34'48 atoms, a second lower freezing point, much more constant in temperature 
than the upper point, was noted. This is reached when the still liquid portion attains 
the composition of the eutectic alloy—40 atoms of copper. This freezing point, and 
all other similar eutectic points, have the temperature placed in brackets, to distinguish 
it from the upper first freezing point at which solid begins to separate. This eutectic 
point is probably the same whatever the proportions of copper and silver. When an 
alloy by partial solidification reaches this temperature, the thermometer no longer 
falls slowly as solidification progresses, but registers a quite constant temperature, 
until the whole mass is solid. 
The total weight of the metals used in this series was 318‘4 grams, but the ingot 
of alloy was found to weigh 315 grams, and a little was left on the stirrer. 
At 32T 8 atoms there was a trace of surfusion. 
Table Ia.— Freezing Points of Alloys made by adding Copper to Silver. 
Series 3.—182'57 grams Silver. 
(1-) 
Total weight of 
copper present. 
(2.) 
Percentage of 
copper. 
(3.) 
Atomic 
percentage of 
copper. 
(4.) 
Freezing point 
on the Centigrade 
scale. 
(5.) 
Atomic fall. 
8-739 
4-57 
7-55 
917-0 
5-70* 
17-447 
8-72 
14-01 
883-7 
5-44 
18-65 
9-27 
14-83 
880-0 
5-.39t 
19-99 
9-87 
15-73 
875-4 
5-38 
21-41 
10-50 
16-67 
870-7 
5-36 
23-03 
11-20 
17-70 
866-0 
5-31 
24-74 
11-93 
18-77 
861-1 
.5-27 
26-54 
12-69 
19-86 
856-3 
5-22 
28-24 
1.3-40 
20-87 
851-8 
5-18 
30-25 
14-22 
22-03 
846-7 
5-14 
.33-25 
15-41 
23-70 
839-5 
5-08 
39-66 
17-85 
27-03 
825-5 
4-981 
* As usual, at this stage, there was an abundaut precipitate at and after the moment of reading, and 
a few degrees below the recorded freezing point stirring became impossible, 
t Here the period of stationary temperature was very short. 
X lu most of the above experiments there was an abundant precipitate at the moment of reading the 
temperature, but the freeziiig point, though quite marked, was not constant for long. 
MDCCCXCVir.—A. F 
