A Comprehensive Treatise on Inorganic and Theoretical Chemistry

PLATINUM 5
§ 2. The Occurrence of the Platinum Metals
The six platinum metals—platinum, iridium, osmium, ruthenium, rhodium,
and palladium—form a group which occur in nature associated together as indefinite
alloys, and generally uncombined. Estimates of the percentage elementary
composition of the igneous rocks of the earth's crust are considered by F. W. Clarke
and H. S. Washington 1 to include platinum nxlO -9 , where n is an undetermined
integer ; iridium and osmium, each n X 1O -10 ; and ruthenium, rhodium, and
palladium, each nxlO -11 . J. H. L. Vogt gave nxl0 _1 ° for platinum. I. and
W. Noddack's estimates are indicated below, and for a later estimate, they gave
5-0 X 1O -8 . The subject was discussed by G. Berg, W. Vernadsky, F. Bernauer,
A. B. Fersmann, I. and W. Noddack and O. Berg, P. Niggli, E. Herlinger,
V. M. Goldschmidt and C. Peters, G. Tammann, O. E. ZvyagintzefT, and P. Vinassa.
Platinum has been reported from extra-terrestrial sources. Thus, J. M. Davison 2
observed platinum and iridium in the meteoric iron of Coahuila, and Toluca, Mexico ;
H. H. Niniger, in the meteoric iron of Ballinger, Texas ; A. Liiversidge, in the meteoric
iron of Boogaldi, New South Wales ; J. C. H. Mingaye also noted platinum in meteoric
iron. The subject was discussed by G. Osann, G. P. Merrill, and O. C Farrington.
Later they gave for platinum in meteorites 7xlO~~ 6 . G. P. Merrill reported the
presence of platinum, palladium, iridium, and ruthenium in meteorites ;
J. C. H. Mingaye, of platinum, palladium, and iridium. Possibly if the platinum
metals had been sought in many other meteorites, they would have been found.
J. IJ. Howe said that it is probable all meteorites contain platinum. I. and
W. Noddack's estimate's for percentages are as follow, atomic* distributions are
relative to oxygen unity.
1'la/tin.um
Iridium
Osmium
Palladium
lthoflium .
Ruthenium
Earth's
crust
8OxIO- 11
. 3OXlO- 12
6OxIO- 12
8-5 vlO- 13
9() x 10- 13
2-3 xlO- 13
Igneous
rocks
8-3 x IO- 8
—
_.
—
_ _
—
Meteoric
iron
1-77 x10-°
2-3 X 1O- 5
8-8 X I0-«
1-9 xIO- 5
5-Ox 10~«
2-39 X 10~ a
Troilite
3-Ox 10-«
fi-OX10~ G
10XIO- 5
4-5 XlO 6
IO x K)- 8
4-20X K)- 6
Atom.
distribution
2-3 X 10-«
3-2 X IO 7
1-4 X H)-«
4-6 X IO 6
1-3 X 10-«
61 xlO-«
O. O. Hutchins and TC. L. Holden 3 observed that 16 lines of the platinum
spectrum coincide with lines in the solar spectrum. H. A. Rowland, and M. N. Saha
classed platinum, iridium, osmium, and ruthenium amongst those elements
whose presence in the solar spectrum is doubtful ; and palladium and rhodium
amongst the elements present in the solar spectrum. The subject was discussed
by H. M. Vernon, JE. F. Baxandall, J. N. Lockyer, and H. N. Russell. IT. von
Kluber classes platinum amongst the elements of doubtful occurrence in the fixed
stars.
Platinum usually occurs in nature as a native metal alloyed with one or more
members of its family, and to a less extent with iron, nickel, chromium, etc.
O. Id. Zvyagintzeff 4 studied the subject. Some of the native alloys have received
special names—e.g. native platinum, native iridium, native platiniridium, native
palladium, allopalladium, iridosmine—neoyanskite or osmiridium with over 40 per
cent, of iridium, and siserskite, or iridosmium, with 30, or less, per cent, of iridium
—palladium gold, rhodium gold, and ferroplatinum. Very few compounds of the
platinum metals occur as minerals. There are only COOperite, represented at first
by Pt( As,S)2, and later by PtS ; braggite, (Pt,Pd,Ni)S ; laurite, RuS2, or (Ru5Os)S2 ;
potarite, PdHg ; sperrylite, PtAs2 ; and stibiopalladinite, Pd3Sb.
In addition to the six members of the platinum family, there may be present
iron, copper, gold, etc. Consequently native platinum may be host to a number
of guests or strangers, and the form of native platinum which is ataracted by a
magnet, was named by J. F. L. Hausmann polyxenite—from rroXvs, many, and
£eVoy, a guest. A. Breithaupt called the latter sideroplatinwrn—from criS-qposy iron
—or simply ferroplatinum. A great number of analyses of native platinum have