1904.] Properties of ike Alloys of Silver and Cadmium. 22 5 



similar case of the silver-zinc alloy AgZn has been investigated by 

 Heycock and Neville,* who also refer to the colour of the alloy AgCd. 



The cooling curves of some alloys containing about equal numbers 

 of atoms of silver and zinc were also prepared for comparison, and were 

 found to be very similar to the cooling curve of AgCd. The freezing 

 point of the alloy containing 51 atoms of zinc to 49 atoms of silver 

 is at 693, and the evolution of heat by the alloy in the solid state 

 is at 281. The corresponding temperatures in the case of the alloy 

 containing equal numbers of atoms of silver and zinc were "found to 

 be 690 and 271. These results can be correlated with the facts 

 observed by Heycock and Neville, who showed that the silver-zinc 

 alloy could be made to assume a red tint if heated to a temperature 

 near 300, the lowest effective temperature being 285, and suddenly 

 chilled. The disappearance of the red tint thus appears to coincide 

 with an evolution of heat in both cases. The red tint can also be 

 obtained in either case by abrasion. It is well shown in filings and 

 sometimes in polished specimens. 



The liquidus curve of the silver-cadmium alloys shows a well-marked 

 cusp at about the 40-per-cent. alloy, pointing to the existence of the 

 compound Ag 2 Cd 3 . This alloy is hard and excessively brittle, breaking 

 with a conchoidal fracture, a proof of homogeneity of structure. 



The remainder of the freezing point curve is of an ordinary type, 

 consisting of two branches meeting at a minimum at about the alloy 

 containing 1*2 per cent, of silver, which solidifies at 315 or 8 below 

 the freezing point of pure cadmium, f Further additions of silver 

 raise the freezing point until a maximum of 676 is reached at the 

 40-per-cent. alloy. A branch of the curve of equilibrium was observed 

 containing about 10 per cent, of silver solidifying at 332. 



The liquidus curve is thus seen to consist of 7 parts, which are as 

 follows : 



(1) Between pure silver and the compound Ag 4 Cd, convex upwards. 

 The two constituents appear to be isomorphous. 



(2) Between the compounds Ag 4 Cd and Ag 2 Cd, concave upwards. 



(3) Between the compounds Ag. 2 Cd and Ag 3 Cd 2 . Nearly a straight 

 line with a horizontal branch corresponding to the freezing point of 

 the compound Ag 3 Cd 2 . 



(4) Between the compounds Ag 3 Cd 2 and AgCd, there is a horizontal 

 branch corresponding to the freezing point of the compound Ag 3 Cd 2 . 

 There is also probably another corresponding to the freezing point of the 



* ' Camb. Phil. Soc. Proc.,' vol. 9, Pt. 4, 1896. 



f Eudberg ('Poggend. Annal.,' vol. 71, 18*7, p. 460) and Rieinsdijk (' Archives 

 Neerlandaises,' vol. 3, 1868, p. 29) both gave the melting-point of cadmium as 320, 

 and Oautier (loc. cit.) takes it as 322. The temperature of 323 adopted here was 

 determined by comparison with the melting-point of pure lead, which was taken 

 as 326. 



