652 
ON THE LIQUATION OF METALS OF THE PLATINUM GROUP. 
ammonium chloride and by pure zinc, as in the palladium-platinum series, and 
weighed as metallic platinum. 
In these analyses, accurately weighed portions of pure rhodium and pure platinum, 
in the proportions of platinum 900, and rhodium 100 parts, were dissolved and 
treated as standards to ensure accuracy in the results of the analyses. 
In the case of the gold-aluminium alloys, several methods were tried for the 
determination of the gold in these various alloys, direct cupellation with lead, and 
the removal of the aluminium by dissolution in hydrochloric acid, but neither yielded 
satisfactory results. The process adopted, therefore, was to ascertain accurately the 
proportion of gold in the various portions of the alloys removed for analysis by 
the following method, the aluminium being found by the difference. 
Determinations of 50 grains each from the various portions of the alloys removed 
for examination were carefully fused in small clay crucibles with litharge under a 
flux of borax and potassium carbonate, with a small proportion of powdered charcoal. 
The button of lead so obtained was removed, and the slag re-fused with a further 
small quantity of litharge and powdered charcoal. The resulting lead buttons were 
then cupelled, and yielded the gold contained in the alloy (the whole of the aluminium 
having combined with the fluxes employed). The gold so obtained was then 
cupelled in pure lead with two-and-three-quarter times their weight of fine silver, 
and parted in nitric acid. The gold thus purified was washed, dried, annealed, and 
weighed. 
This process for the determination of the gold was employed for every one of the 
aluminium gold alloys. 
All these analyses were checked by means of synthetical standards made up of 
gold and aluminium in the same proportions as in the alloys for examination. 
