OF METALS OF THE PLATINUM GROUP. 
G47 
M. 
This result is of special interest. The alloy has a composition which corresponds 
to the formula AhAu, the constituent metals therefore exist in atomic proportions; 
it would appear to be a true chemical compound. There is little or no evidence of 
liquation, the maximum difference between any two assays being only 2'8 parts in a 
thousand. As this is the most highly coloured alloy yet known, the simple atomic 
relations between its constituents is of much theoretical importance. It would appear 
to be as uniform in its composition as any alloy known. 
Several methods were tried for the determination of the gold in these various 
alloys of gold and aluminium. 
Cupellation with excess of lead to remove the aluminium proved quite useless. 
The removal of the aluminium by digestion in hydrochloric acid, and collecting the 
residual gold did not yield satisfactory results. 
The process adopted, therefore, was as follows :— 
Accurately weighed portions of fifty grains each of the alloys under examination 
were fused with litharge, under a flux of potassium carbonate and borax with a 
small proportion of powdered charcoal, and the resulting slag re-fused with a further 
small quantity of litharge and powdered charcoal. 
The lead buttons containing all the gold (the aluminium having combined with the 
fluxes employed) were cupelled, and the resulting gold cupelled with silver and 
parted with nitric acid in the usual manner. All these determinations were worked 
with checks or standards of fine gold and pure aluminium. 
This process for the determination of gold was employed for every one of the fore¬ 
going aluminium-gold alloys. 
Conclusions. 
I regret that time has not enabled me to examine more members of each particular 
series of alloys, so as to present results in fuller detail ; in fact, the silver-copper 
series is the only one upon which anything like exhaustive work has been done. No 
doubt, in every series of alloys there is one definite alloy which would yield a uniform 
