262° Intelligence and Miscellaneous Articles. 
editors of the Phil. Mag. and Journal of Science to insert in that 
journal. 
Feb. 18, 1836. H. J. Brooke. 
“* Dear Sir, “ Mexico, November 14, 1835. 
«<I have again examined the mineral you have been so kind as to 
name Riolite, and have found it to be not a seleniuret of zinc, but a 
native selenium ore with a variable mixture of sulphoseleniuret of mer- 
cury, and seleniurets of cadmium and iron. 
[ put in a retort 533 grs. which I washed to separate the carbonate 
of lime: as some particles were attached to the sides of the retort, 
I washed it down with some water, and at the moment many round 
little lumps of selenium arose to the surface, which was covered with 
a film of the same, proving that it was notcombined. There were sub- 
limed by the distillation 38 grs. of selenium and 13 of mercury, which 
was also amalgamated with selenium; and there remained in the re- 
tort 10 grs. of a yellow and grey powder, 
1. I treated the 10 grs. with muriatic acid, which dissolved the iron 
and the cadmium, and the selenium was precipitated as a black pow- 
der, which amounted to gr. 
2. I precipitated the diluted solution (1.) with a small bar of zinc : 
the grey and voluminous cadmium was easy to be distinguished from 
the iron: both amounted to 13 gr. 
3. The iron was dissolved in diluted muriatic acid, and the cadmium 
in concentrated ; and the last was precipitated again with a bar of zinc 
in a crucible of platinum, to which some cadmium was attached as a 
silver white metal, and some was precipitated as a dark grey powder, 
which deposited upon the charcoal at the blowpipe a reddish brown ring. 
4. Together with the black powder (1.) I observed another preci- 
pitate lighter in colour and heavier, which I separated by washing, 
and treated with hydrochloromuriatic acid. All was dissolved imme- 
diately, and red selenium arose to the surface, which was reduced 
to selenious acid by the addition of nitric acid : there remained only 
a melted globule of sulphur. At the same time some sulphate of lime 
was precipitated, which amounted to 14 gr. 
5. I precipitated the last solution with hydrosulphate of ammonia, 
and I obtained 63 grs. of sulphuret of mercury. 
6. The selenium (1.) was put in a little capsule over the lamp in 
a dark corner of my room with some sulphuric acid, and gave many 
small flashes of light on the surface of the liquid of the selenious acid 
which sublimed; I smelled some sulphurous acid, and the decanted 
solution precipitated red selenium with water ; the remaining solution 
precipitated the same without water; and there was at the bottom 
selenious acid as a white powder. 
As the quantities of mercury and cadmium are variable, because I 
found more in other specimens, I think this mineral is nothing else 
than a mixture to which no formula can properly be applied. 
In the beginning, when I thought it wasa seleniuret of a fixed base, 
I treated it twice at the blowpipe with some iron and borax, and after 
washing the charcoal I found both times the next day very small double 
