Gold alloyed with Rhodium. 803. 
loy. The remainder of the solution took the colour of the 
protosulphate of iron. 
Vv 
In this state it occurred to the Chevalier Mendez, to add 
sulphuric acid to the solution in aqua regia, of 10 grains of 
another alloy, whose sp. gr. was 16.8, and to distil to dry- 
ness. When all the muriatic acid had passed over, and the 
liquor in the retort become very red, he changed the receiver, 
and a yellow matter passed with the acid, the gold remaining 
in the retort as if it were massive gold. The yellow matter 
was partly dissolved in the water, tinging it first yellow and then 
green, and the remainder formed an ochre-yellow sediment, 
which would be subtritosulphate of rhodium. On i 
water into the retort, the same sediment was formed, which 
was separated by decantation ; and the gold was twice melt 
with potash and nitre, leaving a scoria, the first time, of a 
deep pistachio-green colour, and the second of a brighter 
green ; so that it would have been necessary to repeat the 
process several times, in order to have lefi the gold perfectly 
pure: it weighed, in the state in which we leave it, 8.2 
grains. - 
I feel compelled to say, that Dr. Wollaston is in error 
when he asserts, that the alloys of gold with rhodium are ve- 
ry ductile. The contrary has been observed in the smelting 
house here for years, and was attributed to the acridness of 
the acids, as if more than one were used, and as if that were 
not very volatile, and easy of decomposition. _We can now 
conceive, that arough metal, and in such quantity, must give 
roughness to the alloys which it forms. — 
I suppose that men of experience will not now say, that 
with the cupel, and two or three acids, any fraud in gold 
may be discovered ; since, in addition to the examples of pla- 
tina and palladium, which they before possessed, they now 
have that of rhodium; and iridium will one day afford also 
not to be obtained by softening the gold (as the French ex-. 
