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When So Little Means So Much
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# : |
19933 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
4 / 1992 |
3,011 Words |
| Author
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Harold Goldwhite
Harold Goldwhite is professor of chemistry at California
State University, Los Angeles. |
In the seventeenth century in that part of South America now known as Colombia, prospectors found gold--but it was sometimes contaminated with a silvery black material that was as dense as gold. They called this nuisance material platina, a diminutive of plata, the Spanish word for silver. Platina became the source not only of platinum but of the platinum group of precious metals, which includes iridium, osmium, palladium, rhodium, and ruthenium. Platinum is the most familiar of those metals, and the average person, if asked to give some uses for it, would probably be hard pressed to think of any apart from jewelry. Yet platinum is essential to the chemical industry, the glass industry, electronics, and laboratory science. Platinum has also recently proved to be the basis of a valuable anticancer drug.
The current cost of platinum is about $340 an ounce, almost as costly as gold, yet platinum has such a remarkable range of essential industrial uses that it is classified as one of the strategic minerals.
The dark grains of platina, which were such a nuisance to the early gold miners of South America, had a remarkable property: They could not be melted in the hottest furnaces available at the time. But platina was clearly metallic; it could be flattened with a hammer and could even be soldered with gold. Indeed, platina grins could be dissolved in molten gold, which raised concerns that platina might be used to debase gold coins.
In response, the Spanish occupiers of Central and South America put an embargo on platina that probably stimulated the development of a modest trade in the material. Via the islands of the Caribbean, platina reached Europe, where in the 1770s it began to attract the attention of scientists.
Platina was soon found to be not only impossible to melt in the furnaces available at that time, but it was also as resistant to the attack of chemical reagents as gold. It became clear during the eighteenth century that if a pure metal could be extracted from platina and made into chemically resistant objects, it would be quite useful and valuable. Many scientists attempted to do this; it was an Englishman who finally perfected a method. William Hyde Wollaston, a physician trained at Cambridge University, abandoned medicine for chemistry in order to try to purify the metal of platina. From 1805 to 1814, Wollaston and a colleague, Smithson Tennant, made a scrupulously careful chemical study of platina. They showed that it was an alloy of primarily platinum with substantial amounts of a new metal,
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