648 
MR. EDWARD MATTHEY ON THE LIQUATION 
mass on cooling, and it is known that in the silver-copper series this alloy (Leyol’s) 
contains 718 parts of silver per thousand. It is not certain, however, that this is the 
euctectic alloy of the series—that is, the one with the lowest melting point—but it is 
well known that when silver-copper alloys which contain more silver than 718 parts 
per thousand are cooled, the centre of the solidified mass is richer than the exterior. 
This is the case with standard silver for instance, which contains 925 parts of silver 
per thousand, and it is safe to conclude that an alloy rich in copper is the first to fall 
out from the mass, and that this alloy sets round the inner surface of the mould, 
driving a still fluid alloy—rich in silver—to the centre. The general rule in the 
present results, seems to be that in the cooling of a fluid mass of two united metals, 
an alloy rich in the more fusible constituent of the mass falls out first driving the less 
fusible constituent to the centre. The gold-platinum alloys (A, B, C, D, and E) seem 
to be always rich in gold externally. 
It is remarkable that the metals of the platinum group do not show much liquation 
among themselves, but, on the other hand, when gold is united to the members of the 
platinum group there is evidence of liquation. 
The gold-palladium one (F), follows the above rule. 
There is evidence that the alloy E, containing 750 parts of platinum and 250 
of gold, is near the composition of a true compound, as it shows hut little sign of 
liquation, and is, moreover, hard and brittle, differing materially from the rest of the 
series. The purple alloy of gold and aluminium M, AuAh, is almost certainly a 
true chemical compound, the solidified mass being as nearly uniform in composition 
as may be. The uniformity of the alloy (J) of platinum with 10 per cent, of rhodium 
is of much interest in view of the important part which the alloy is playing in 
pyrometric work. 
Conducting the experiments, the results of which are embodied in the present 
paper, has been very laborious, and although, as already stated, no complete series of 
the alloys of any two metals has been examined, quite sufficient data have been 
collected to afford valuable guidance to the metallurgist, who will now know what 
behaviour may be expected from the other members of the groups of the alloys in 
question. The gold-platinum series of alloys are of industrial importance, as native 
gold is so often associated with platinum, and it is somewhat surprising to find that 
assays made on pieces of metal cut from the exterior of an ingot cannot be trusted 
to rooresent the composition of the mass. The aim of the investigation has been to 
show tnat notwithstanding the great difficulty which attends the preparation of alloys 
of metals with very high melting points, it is possible to elicit from them the same 
kind of information which has proved to be so useful in the case of the more ordinary 
and tractable alloys. 
