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The Platinum Metals
U
James L Marshall, Beta Eta 1971, and
Virginia R. Marshall, Beta Eta 2003,
Department of Chemistry, University of
North Texas, Denton,TX 76203-5070,
jimm@unt.edu
n 1735, the French Academy commissioned
a scientific expedition to New Granada' to
measure a degree of the meridian at the
equator to detect any deviancy from a perfect
sphere of the earth. The results would detemine
who was correct: Newton, who thought the
earth was flattened at the terrestial poles, or
Descartes, who predicted the earth bulged at
the poles.2 The expedition included 13 profes-
sionals, including Antonio de Ulloa y de la
Torre-Giralt (1716-1795), mathematician-
explorer and a sailor in the Spanish navy,
(Figure 1). When de Ulloa returned in 1744, his
ship was captured by the British, and he was
taken to England. Because of his scientific
stature, he gained the respect of the scientific
community and was even elected a member of
the Royal Society in London. He was allowed to
return to Spain and he published a full account,
of his travels to the New World.3 In this account
de Ulloa described a new metal which was
known in the Spanish colonies as platina di
pinto ("worthless little silver of the Pinto River")
or oro blanco ("white gold").4 Antonio de Ulloa
is generally credited with the "discovery" of the
metal in the New World because his was the
first published account of the metal in Europe1
(Figure 2).
'AAA y
Figure 1. Bust of Antonio de Ulloa (S 00 00.19 WN
780 27.27) at Mitad del Mundo ("Middle of the
World") at Pichincha, Ecuador, 35 km north of
Quito, Ecuador. Mitad del Mundo is a park
commemorating the astronomical measurements
made at the equator by de Ulloa and colleagues in
1736. de Ulloa's statue is only one of 13 including
that of his principal colleague Jorge Juan y
Santacilla (1713-1773). The park holds a
museum, planetarium, other monuments, and
other usual tourist attractions. de Ulloa had a
varied career, credited with the discovery of
platinum (Note 1), then becoming the first
governor of Spanish Louisiana (1766-1768), and
later establishing the first mineralogical laboratory
in Madrid. Courtesy, Miguel A. Monjas, under
GNU License.
Originally, platina was recognized as use-
less, because it was difficult to work, its melting
point being beyond normal forging tempera-
tures (700-800 above copper, silver, or gold).'
Found mainly in Choc6, Colombia, it interfered
with the preparation of malleable forms of gold
and was considered as "useless slag." The
Spanish government was concerned that gold
might be adulterated with platina and ordered
it discarded; from the river sands, the gold and
platinum grains were laboriously separated by
hand and the unwanted platina was dumped
into rivers and landfills. However, de Ulloa sus-
pected the new metal might be of value, and he
apparently was able to deliver some of the
metal to Spain for further investigation.'
In spite of Spain's attempts to maintain
secrecy of platinum and its potential use to
"debase" gold, reports of the new metal from
the New World began to circulate in Europe.
Shortly after de Ulloa's report, Sir William
Watson (1715-1787) and Dr. William Brownrigg
(1711-1800) contributed a paper to the Royal
Society of London' more fully describing the
properties of this new metal (Note 1).
After the report of Watson and Brownrigg of
platina, research on the new metal commenced
m Europe. It was becoming clear that platina
was a new metal in its own right, even though
George-Louis Leclerc, Comte de Buffon
(1707-1788), the famous scientist known for his
Histoire naturelle, considered the metal merely
as an alloy of iron, gold, and mercury."a In 1777
the Swedish Tornbern Bergman (the mentor of
Scheele7) proposed that platina be named
platinum in accordance with Linneaus' proto-
col," although full acceptance of the new name
did not occur until the mid-1800s.1a
The curiosity of skilled laboratory chemists
led to further knowledge of the platina.
Marggraf 7 in Berlin in 1757 found that platina,
like gold, would dissolve in aqua regia1'; he
marveled that the chloride of platinum com-
pounds could not be precipitated by lead solu-
tions (we now know that chloride is covalently
coordinated in the hexachloroplatinate anion,
PtCl62-).
Scientists rued the intractability of platinum
but realized its chemical inertness promised
usefulness in chemical laboratory ware. Pierre-
Joseph Macquer, chemist at the Jardin du Roi in
Paris, was able in 1758 to melt small buttons of
platinum by means of a large burning mirror;
but to melt platinum in quantity required
extreme means such as the oxy-hydrogen torch
which was not readily available until the begin-
ning of the 19th century.9bi
THE HEXAGON/SPRING 2009
8
