1160 
MR. G. F. RODWELL ON THE EFFECTS OF HEAT ON CERTAIN 
Discussion of the Results. 
1 . The copper-silver iodide alloys described in the foregoing pages vary in regard to 
the quantity of iodide of silver which they possess to the extent of 50 per cent.; 
the lowest, Cu 2 I 2 .AgI, containing 38 per cent, of iodide of silver, and the highest, 
Cu 3 I 3 .12AgI, 88 per cent. 
2 . It will be noticed, however, that the percentage of iodine varies hut little, for 
while Cu 3 I 2 .AgI contains 61'9055 per cent., Cu 2 I 2 .12AgI contains 55‘5695. 
3. The specific gravity of the alloys varies slightly, and is a little above the mean 
specific gravity of their constituents. This was also observed in the case of the five 
chlorobromiodides of silver previously described (p. 1140), and in that of the lead-silver 
iodide alloy (p. 1146), and while the specific gravity of Cu 2 I 2 is 5‘6936, and of Agl 
5‘6750, that of the alloys is as follows :—■ 
Cu 2 I 2 . Agl . 
, . . 57302 
Cn 2 I 2 . 2AgI . , 
, . . 57225 
Cu 3 I 2 . 3AgI . , 
, . . 57160 
On* 4AgI . , 
. . . 57064 
Cu 3 I 3 .12AgI . , 
. . . 5-6950 
4. The melting points do not differ much from each other, in fact those of Cu 3 I 2 .2AgI, 
Cu 2 T 2 .3AgI, Cu 2 I 2 .4AgI, and Cu 2 I 2 .12AgI, are practically the same; but they are 
considerably lower than those of their constituents: i.e., more than 100° C. lower 
than that of iodide of copper, and more than 30° C. lower than that of iodide of 
silver. This was also noticed in the case of the chlorobromiodides of silver, and in 
that of the lead-silver iodide alloy. 
5. While both the iodide of copper and the iodide of silver are highly crystalline in 
structure, even in thin layers, the copper-silver iodides are resinous in fracture and 
transparent in thin layers, even when they contain as much as 65 per cent, of iodide 
of silver. With greater percentages the structure becomes slightly crystalline. 
6 . It is obvious that some of the alloys possess three points of similar density; 
and others two, at different temperatures. Thus, in the case of Cu 2 I 2 .2AgI, the 
density is the same at 133° C., 265° C., and 334° C. 
7. When strongly heated in a current of carbonic anhydride the alloys remained in 
tranquil fusion, undergoing an extremely slow volatilization. Heated in a current of 
dry oxygen, iodine was freely evolved, and oxide of copper appeared on the surface of 
the mass. When heated in dry hydrogen, hydriodic acid was formed, and the iodides 
were reduced. 
