C H ET M ] 
^t'ld produced no change ryhatfoever in grains of platina. 
Margraaf likfevvife obtained from this acid, diltilled from 
the metal, a white fublimate, which appeared to him to 
be arfcnic, and a reddilh fublimate, whole properties he 
could not examine on account of its.tjeing in lo lrnall a 
quantity. All thefe appear, however, to be foreign to 
the platina itlelf: this metal, therefore, refembles gold by 
the flight adlion of the Ample acids upon it; but the ana¬ 
logy is ftill more evident by its folubility in the oxyge¬ 
nated muriatic acid, and in nitro-muriatic acid. The 
hilt of thefe acids difl’olves platina with facility, and 
without the a Alliance of a llrong heat; feventy or eighty 
degree's of heat in the atmofphere being lufficient to fa¬ 
cilitate this folution, which takes place without any fen- 
Jlbfe feftervefcence, and in other relptdls does not differ 
from the fallowing. 
The nitro-muriatic acid, bell; adapted to diflolve pla¬ 
tina, is compoled of equal parts of the muriatic and ni¬ 
tric acids. To effodl this folution, which in general is- 
lefs eafily performed than that of gold, one ounce of pla¬ 
tina muff be put into a retort, on which a pound of ni- 
tro-muriatic acid, in the proportions here mentioned, 
muff be poured; the retort is then to be placed on a 
land-bath, with a receiver applied ; as Toon as the acid is 
hot, a few bubbles of nitrous gas are extricated, and the 
adtion of the mixed acid proceeds without violence or 
rapidity. The colour of the fluid becomes at firff yellow, 
afterwards orange, and at laff of a very deep brown. 
When the folution is finilhed, reddilh and black particles 
of land are found at the bottom of the retort, from which 
the faturated liquor is to be leper a ted by decantation : 
final! irregular cryftals of a dulky colour are gradually 
depofued, which confilt of a combination of the acid and 
platina. The folution of platina is of a deeper colour 
than that of any other metal. Though it appears of a 
dark brown, yet, if it be diluted with water, it aflumes 
firff an orange colour, which loon becomes yellow, and 
refembles the folution of gold : it tinges animal matters 
of ablackilh brown, not at all inclining to purple. Baume 
affirms, that platina fufed in the focus of a burning mir¬ 
ror, and diflolved in aqua regia, does not aflume a brown 
colour, like that of platina in grains, but that the folu¬ 
tion is of a deep orange-yellpw colour. Macquer affirms, 
that, by evaporating and cooling the folution of platina, 
much larger and more regular cryftals ate obtained, than 
thofefpcntaneoufly depofited by the faturated fluid. Lewis, 
having left this folution to evaporate in the open air, 
obtained cryftals of a deep red, of a moderate (ize, irre¬ 
gularly formed, and refembling the acid of benzoin, 
though thicker : Bergman deferibes it as being of an oc¬ 
tahedral form. This fait is (harp, but fcarcely cauftic; 
it melts in the fire, the acid being diflipated, and a refi- 
due is left in the form of an obfeure grey oxyd. Con¬ 
centrated fulphuric acid occafions a precipitate of a deep 
colour, which, doubtlefs, is a fulphat of platina.; the mu¬ 
riatic acid, in a certain time, produces a yellowilh depo- 
fition. Alkalis and the, falino-terreftvial fubftances de- 
compofe this folution of platina : the carbonat of potafli 
produces an orange-coloured precipitate in' the folution 
of platina, which is not a pure oxyd. Macquer and 
Baume have observed that its colour is owing to a cer¬ 
tain quantity of acid it contains. It mull therefore be 
conlidered as a mixture of a portion of the oxyd of pla¬ 
tina with muriat of potafli, or as a kind of triple lb It. 
The cauftic ammoniac precipitates platina of an orange 
yellow : this precipitate is a triple fait, like the foregoing. 
The property of thefe two alkalis in forming -triple 
falts, is very ufeful, when the objedt is to feparate gold 
from platina. Diflolve the whole, pour on fome potafli, 
and a triple fait will be formed with the platina, while 
the gold remains in iblution. Or it may be feparated by 
means of a fuipliat of iron, which precipitates the gold, 
and not the platina. Soda, however, forms no triple nit 
with muriat of platina ; but the platina is converted into 
S T R Y. 319 
an oxyd; and precipitated litne and barytes have the fame 
effedt. The platina thus converted into an oxyd may 
then be diflolved on the other, and form falts ; but thefe 
ffilts have not been examined. 
To obtain a very pure folution of platina, it fliould firff 
be digefted in muiiatic acid, which diflolves the iron, if 
there be any. The prefence of iron in a Iblution of pot¬ 
afli, may be afeertained by means of Pruiliat of potafh ; 
for platina is not precipitated by that fait,; but iron is. 
The galiic.acid precipitates' the folution of platina in a 
dark coloured glafs, which grows paler by degrees. 
Mol of the neutral falts have no adlion on platina. 
Margraaf heated platina by a ftrong fire, with fulphat of 
potafh and foda ; thefe falts melted, and the platina re¬ 
mained in grains without alteration : it only communi¬ 
cated a flight reddilh colour to the inline fubftances, 
doubtlefs on account of the iron communicated by the 
metal to them. 
Nitre produces a lingular alteration in platina, accord¬ 
ing to the experiments of Lewis and Margraaf. Though 
no detonation is produced when a mixture of both fub¬ 
ftances is thrown into a red-hot crucible ; yet, by a 
ftrong heat long continued, inch as Lewis applied for 
three fuccelfive days and nights to a mixture of one pa.rt 
of platina and two of nitre, the metal becomes of a nifty 
colour. If the mixture be boiled in water, the fluid dif- 
lolves the alkali, which takes up the brownifiiqiowder, 
and the pldtina feparated from the liquid is found dimi- 
nifhed more than one-third or its weight. The brown 
powder taken up by the alkali may be lepar.ited by fil¬ 
tration. It appears to be a kind of oxyd of platina) mixed 
with a finall quantity of oxyd of iron. Lewis converted 
this oxyd to a whitifh grey colour, by diftiiling it a great 
number of times with ammoniacal muriat. Margraaf, 
who repeated this experiment, adds two important fadts ; 
the firff is, that platina, combined with the alkali of ni¬ 
tre, and diluted in a certain quantity of water, forms a 
jelly ; and the other, that, by heating the por tion of me¬ 
tal feparated from the jelly, diluted with water and fil¬ 
trated, it becomes of a black pitchy colour. This expe¬ 
riment certainly thews a great alteration of the platina, 
and requires to be continued, in order to decide whether, 
by virtue of repeated oxydations with nitre, it be poflible 
to reduce the whole of the metal into a brown powder, 
and efpecially to determine the ftate of the platina thus 
oxy dated. 
All the properties of platina which we have examined, 
appear to prove that thisYubftance is a peculiar metal: 
its want of dudlility and fufibility, which have been ccn- 
fidered by fome writers as llrong objedlions to this opi¬ 
nion, are not capable of overthrowing it, fince there is, 
perhaps, a lei's difference between the fufibility of platina 
and forged iron, than between that of forged iron and 
lead, and fince its want of dudlility arifes from its not 
having undergone complete fufion. As to the opinion of 
tliofe philofophers who coniider platina as a natural alloy 
of iron and of gold, however ingenious and fatisfadlory it 
may appear, it is impoffible to admit it, until the metal 
lias been feparated into the two others by an accurate 
abalyfis, and until platina can be better imitated by the 
artificial alloy of gold and of iron. Macquer has made a 
very ftrong objection againft this laft opinion, by observ¬ 
ing, that the more platina is deprived of the iron it con¬ 
tains, the greater is the difference between its external 
appearances and thole of gold. 
The important ufes to which this metal may be applied 
will be eafily conceived, when it is conlidered that it unites 
the indeltrudtibiiity of gold to a degree of hardnefs almoft 
equal to that of iron ; that it refills the adlion of the molt 
violent fire, and alio of the inch concentrated acids. It 
cannot be doubted but that chemiftry and the arts would 
be in the higheft degree benefited by its being applied to 
ufeful purpoles, Crucibles have been made with platina, 
and fpoons or ladles for allays by the blow-pipe. Conte 
availed 
