Metals. M 1 N E R 
unites, fays Chaptal, two qualities never before met with 
in one and the fame fubftance—when formed into a mir¬ 
ror, it reflects but one image, at the fame time that it is 
as unchangeable as a mirror of glafs. As this metal, 
then, pofielfes fo many valuable qualities, it is to be hoped 
the court of Spain will lay afide its ltupid narrow policy, 
and revoke the decree which has been palled againft it; 
and that the Spanilh government will neither delpife fo 
rich a treafure as its mines of platinum, nor refufe to the 
world the numerous advantages which may be derived 
from a fubftance that promiles to be of fo much import¬ 
ance in commerce and the arts. 
During the year 1806, feveral new and important expe¬ 
riments were made by different chemilts on crude pla¬ 
tinum, from which the molt curious refults have been ob¬ 
tained. In endeavouring to difcover the caule of the dif¬ 
ferent colours of the triple falts of platinum, M. Defcotils 
perceived that the red colour of fume of them was owing 
to the prefence of an unknown metal. Fourcroy and 
Vauquelin, on their part, examined the black powder 
which remains after dilfolving platinum ; and, finding 
that, in fome of their experiments, it exhaled a flrong me¬ 
tallic odour, and in others alfumed a more fixed form, 
they were led to regard it as a new metallic fubftance, the 
different properties of which they attributed to its dif¬ 
ferent degrees of oxyge*nation. During this fame period, 
Mr. Tennant examined this black powder, and fucceeded 
in leparating it into two metals, one of which was fixed, 
and the other extremely volatile ; while Wollafton dilco- 
vered that in the folution itfelf, which was fuppofed to 
contain only platinum, there was a mixture of two other 
metals, which not only differed from thole which form the 
black powder, but alio from platinum itfelf. Thus, after 
having been l'ubje£ted to a long feries of the molt accurate 
experiments during the courfe of forty years, chemifts 
have fucceeded in detaching eleven different metals from 
this lingular mineral, viz. 1. platinum; 2. gold; 3. filver ; 
a. iron; 5. copper; 6 . chrome; 7. titanite. The two laft 
were difcovered by Fourcroy and Vauquelin, in the dif¬ 
ferent coloured finds which are always mixed with it. 
The two new metals feparated from the folution of 
platinum in the nitro-muriatic acid by Dr. Wollafton, 
are : 8. Palladium, a white ductile metal, heavier titan 
filver, very fuiible when united with fulphur, foluble in 
nitric acid, colouring its folution of a beautiful red, pre- 
cipitable in a metallic Hate by the fulphat of iron ; yield¬ 
ing a dingy green precipitate with the prufliat of pot-afh, 
forming with foda a triple fait, foluble in alcohol. 9. Rho¬ 
dium, a grey metal, eaiily reducible, fixed and infufible, 
imparting a rofe-colour to its folutions in acids, which is 
rendered much deeper by the addition of muriat of tin, 
precipitated by the alkalies of a yellow colour, but not 
at all by the prufliat of potafh, the triple fait of which 
with foda is infoluble in alcohol. 
The two metals difcovered by Mr. Tennant in the 
black powder after folution are : 10. Iridium, a very 
hard white metal, difficult of fufion, nearly infoluble in 
the nitro-muriatic acid, and wholly fo in all the others ; 
oxydizable, and foluble by the fixed alkalies, the oxyd 
being foluble in all the acids, and imparting to the dif¬ 
ferent folutions various vivid and lively colours. It is 
thefe falts which give the red colour to thofe of the pla¬ 
tinum. 11. Ojinium, a metal hitherto irreducible, the 
oxyd of which, in the form of a black powder, is ex¬ 
tremely volatile, having a flrong odour; it is very fufible, 
diffolves readily in water, exhales with it in the form of 
vapour, to which it imparts a ltrong tafte and fmell. The 
folution becomes of a blue colour by the addition of the 
fmalleft quantity of the tindture of galls. 
No veins or confiderable maifes of pure platinum have 
ever been difcovered. Some fragments, how'ever, weigh¬ 
ing from ten to forty grains, have occafionally been found, 
and are prelerved as mineralogical curiofities. An ex¬ 
traordinary large fpecimen of this kind, exceeding the 
iize of a pigeon’s egg, is faid to have been given by Hum¬ 
boldt to the National Muleum of France j it weighs 1088 
A L O G Y. Metals. 470 
grains, and its fpecific gravity is 15*6. It was found in 
1800, in the mines of Taddo, in the diftridt of Choco. 
Platinum, in the granular form juft defcribed, which is pro¬ 
perly that of an ore, ftill containing a variety of impuri¬ 
ties, fluctuates in its fpecific gravity between 15 and 17. 
In oneinltance Dr. Wollafton law it reach 17-7 ; but this 
is the heaviefl fpecimen he ever met with. Phil. Tranf. 
1805. 
The fpecific gravity of malleable platinum is generally 
found to be about 21*3, not riling to 22 or 23, as fome 
French chemifts have erroneoully Hated ; but being fub- 
jedt to flight variations according to the different degrees 
of denlity it has received during the procels of hammer¬ 
ing. Gold, the next heavielt metal, is 19-3 ; and there¬ 
fore the denlity of platinum is much more confiderable 
than that of any other known fubftance. In its native 
Hate, however, the fpecific gravity of the platinum ore 
does not, as was obferved before, exceed 177 ; whilft 
that of the grains of Iridium and Olinium above-men¬ 
tioned is 19*15, which is a higher degree of fpecific gra¬ 
vity than that of any other known native fubftance. 
The great dudlility of platinum has been put in a very 
ftriking light by fome recent experiments of Dr. Wollafton. 
(Phil. Tranf. for 1813.) This philofopher, whole dex¬ 
terity in mechanical operations is no lels conlpicuous 
than his views in natural lcience are acute and refined, 
fucceeded, by a new and ingenious procels, in drawing 
platinum wire fo linall as the Y^^th, ol ' even T7 J 5s th 
part of an inch in diameter ; and the tenacity of the lat¬ 
ter was ftill fuch as to fupport 17 grain without break¬ 
ing. The method by which Dr. Wollafton fucceeded in 
obtaining fuch very fine wire was lhortly this : a piece of 
platinum wire, previoufly drawn, by the ul'ual means, to 
the T <^yth of an inch, was fixed longitudinally in the cen¬ 
tre ot a Ihort cylindrical mould of one-third of an inch 
in diameter; the mould being afterwards filled with 
melted filver, a cylinder of this metal was evident, that 
by drawing the filver rod to -J g th, the platinum wire was 
reduced to Yo’ooth of an inch; and this was repeated, till, 
by a fucceflion of fimilar reductions, the extremely-fmaU 
wires above-mentioned were obtained. The filver coat¬ 
ing was then removed by dilute nitrous acid, which left 
the platinum wire untouched. Very fine wires of this 
kind have been employed by Dr. Wollafton to meafure the 
inteniity of very linall Voltaic batteries. And it has been 
obferved, that platinum, which is the molt infufible me¬ 
tal by other means, melts, by the operation of the voltaic 
pile, fooner than zinc. During the fufion of platinum 
v.fire in vacuo, a number of vivid fparks W'ere given out, 
which Dr. Davy imagined proceeded from the difengage- 
rnent of hydrogen, which forms a conllituent part of car¬ 
bon and the metals. 
The difficulty of reducing this metal to the malleable 
Hate, and its great importance in the conftrudtion of che¬ 
mical vellels, are well known. Hitherto it has only been 
done for fale in Paris and in London. Parifian platinum 
is by far the deareft: its fpecific gravity is in general not 
fo high as our London platinum, though it fometimes ex¬ 
ceeds 21. M. Leithner, who has the charge of the porce¬ 
lain manufactory at Vienna, has lately propofed a new 
method of rendering platinum malleable. It is exceed-, 
ingly Ample, and appears to anfwer well enough in a finall 
fcale, though it is not adapted for the conftrudtion of 
large vellels. It coniifts in making up the fine powder of 
pure platinum into a palte with oil of turpentine, and 
laying it in coats upon paper, allowing one coat to dry 
before another is applied, and continuing to add coats 
till the layer of platinum is of lufficient thicknefs. When 
this is done upon porcelain, and the veflel afterwards ex- 
pofed to the temperature of from 14 0 to 18 0 Wedgwood, 
the platinum adheres, and may be burnilhed. When laid 
upon paper, and then expofed to a ltrong heat gradually 
railed, a llieet of platinum remains, which may be ham¬ 
mered, and converted into any lhape that is wanted. 
It is by methods of this kind that utenfils of platinum, 
though ftill expenlive, have gradually become lefs fcarce, 
and 
