1831.] 
41 
supposed to be Platina from A va. 
k. The black powder, left untouched by the soda, was boiled in nitro- muriatic 
acid, which dissolved all but 8,3 parts (D), (for one or more repetitions of the 
process are necessary to effect the solution of the whole.) The solution was bright 
oi ange at first, but became darker under concentration, until it was of a dense 
brown. Tested with green sulphate of iron, it became nearly colourless, which is a 
distinguishing mark of iridium. 
During concentration, some pearly flat acicular crystals were deposited (as had 
also been marked in the solution b). These were found to be soluble in boiling 
water, and were, therefore, washed off, and set aside for further scrutiny, (B.) 
/. The clear decanted acid solution, evaporated to dryness, yielded dark brown 
muriate of iridium, 29,3 ; which further heated to 1900° ? Far. was reduced 
into the characteristic bluish black sponge of iridium, weighing 13,5 1 
to which must be added a proportion (say half) of the residual 8,3 4,2 J 
A portion of this sponge, ignited in the apex of the blowpipe flame, was, with 
difficulty, made to assume a metallic, light grey lustre, iridium being much 
more refractory in this respect than platina itself. 
The daik brown colour of the neutralized solution f, which also gave a dark brown 
piecipitate with ammonia, shews that some iridium might remain therein ; still, the 
deficiency upon the original black powder g (53,4) could only be accounted for, by 
a large portion of the oxyd of osmium having been dissipated. 
Ihe solution^' was not affected by muriate of ammonia, nor by sulphate of iron : 
b\ muriate of tin, it became colourless ; prussiate of ammonia turned it green. 
It did not exhibit any trace of lead. Until an opportunity offers, of further 
analysis, it will be safe to look upon the whole of g as iridium and osmium. 
Examination of A. 
m. The white precipitate, 17,2, obtained in the first process, was submitted to the 
following tests before the blowpipe. 
1. Alpne, at a red heat, it was unaltered, and did not lose weight. 
2. Gradually raised the flame, acquired a faint grey tinge, and the matter dissi- 
pated without fusion, leaving a refractory alloy on the platina wire. 
3. With borax, it formed an opake dirty green enamel, with occasional specks of 
black. 
4. On charcoal it dissipated in fumes, having an odour resembling that of arsenic, 
and leaving globules of a steel coloured metal behind : a slight yellow tinge, like 
that of litharge, spread around. 
5. Heated on a support of mica (the most convenient for minute examinations), 
it gave out fumes of arsenic : the yellow oxyde of lead then penetrated, and fused 
with the mica : — finally, a round globule of infusible metal remained, imbedded 
apparently in scoria of iron. 
6. Heated low red, with charcoal powder, in a test tube, it did not yield a metallic 
ring of arsenic ; apparently, requiring a higher heat than the tube would bear for 
its decomposition. 
7. It was quite insoluble in water, and very slightly soluble in strong nitro- 
muriatic acid. Ammonia separated it thence in a flocculent, white form. 
I am at a loss to pronounce, with accuracy, upon the nature of the above substance, 
from the minute quantity submitted to trial. Arseniate of lead alone would have 
been more fusible ; and no mention is made in Mr. Lane’s notice, of the admixture 
of either of these metals in melting the ore, and they are not otherwise commonly 
found in combination with platina. It seems rather to be a mixture of the arseni- 
ates of lead, iron and platina ; but it is strange, that arsenic should be able to resist 
the heat of a forge in a close crucible, without sublimation. From my own expe- 
