When you think about jewelry, what comes to mind? Jewelry, of course, but I bet you also think of silver, gold, and platinum. Did you know that platinum is considered a precious metal? Precious metals are rare and have significant economic value. Let’s discover together what platinum is.
Discovery of Platinum
Platinum has been around for so long that its discovery cannot be attributed to a single individual. A small amount of platinum was used in ancient Egypt around 700 BCE; platinum was found on a coffin in the tomb of Queen Shapenapit in Thebes. Unlike other materials, it wasn’t found in Greek, Roman, or Chinese cultures.
However, people on the other side of the globe were using it. In South America, on the border between Colombia and Ecuador, funeral artifacts containing platinum were discovered about 2,000 years ago.
A Sample of Platinum
Since we do not know who discovered platinum, the real question is who decided that platinum was a unique metal, and when did this happen? An Italian scientist named Julius Scaliger was probably the first person to determine that platinum was unique. In 1557, he wrote about a metal from Central America that did not melt, giving it the name platinum. Unfortunately, few paid attention to Scaliger, so platinum was rediscovered later.
In the 18th century, the Spaniards who conquered South America became interested in a strange metal that resembled silver but did not tarnish. In 1735, Antonio Ulloa studied platinum in Panama and presented his findings to the Royal Society of London. It was at this time that people began to recognize that platinum was indeed a unique metal and element!
Platinum in Practice…
Among metals, platinum is one of the least reactive metals. It is highly resistant to corrosion, even at high temperatures, making it a metallic element. Therefore, platinum is generally found in its uncombined chemical form as native platinum. It is present in certain nickel and copper ores as well as in some native deposits, primarily in South Africa, which accounts for 80% of global production. As platinum is naturally found in alluvial sands in various rivers, pre-Columbian indigenous people in South America were the first to use it to make artifacts.
Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dental equipment, and jewelry. Being an important metal, it poses health hazards when exposed to its salts; however, due to its corrosion resistance, metallic platinum has not been linked to adverse health effects. Compounds containing platinum, such as cisplatin, oxaliplatin, and carboplatin, are also used in chemotherapy for certain types of cancer.
History of Platinum
Archaeologists have found traces of platinum in gold used in the burials of ancient Egypt as early as 1200 BCE. The metal was used by pre-Columbian Americans near present-day Esmeraldas, Ecuador, to make objects from a white gold and platinum alloy. To work the metal, they combined powders of gold and platinum through the sintering process. The resulting alloy was soft enough to be shaped with tools. The platinum used in these objects was not the pure element but a mixture of the platinum group metals, with small amounts of rhodium, palladium, and iridium.
European Discovery: The first reference to platinum in European culture can be found in the writings of the Italian humanist Cesar Scaliger in 1557. The writing outlined an unknown metallic element found between Darien and Mexico, “which no Spanish fire or device has yet been able to liquefy.” Antonio de Ulloa is credited in European history as the discoverer of platinum. In 1748, Antonio de Ulloa established the first mineralogical laboratory in Spain and was the first to systematically study platinum. In 1752, Henrik Scheffer named it “white gold.”
Characteristics of Platinum
- We can see pure platinum as a shiny, ductile, and malleable metal.
- It is silvery-white in color. Platinum has a higher ductile strength than silver, gold, or copper, making it the most ductile of pure metals.
- It is corrosion-resistant, stable at high temperatures, and has stable electrical properties.
- Platinum oxidizes at 500°C; this oxide is often easily removed thermally.
- It reacts vigorously with fluorine at 500°C to form platinum tetrafluoride.
- It is also attacked by chlorine, bromine, iodine, and sulfur.
- Platinum is insoluble in hydrochloric acid and nitric acid but dissolves in hot nitrohydrochloric acid.
- The most common oxidation states of platinum are +2 and +4.
- +1 and +3 oxidation states are relatively less common.
- While elemental platinum is generally unreactive, it dissolves in hot nitrohydrochloric acid to form aqueous chloroplatinic acid.
- Platinum is a soft acid and has a strong affinity for sulfur, as seen in dimethyl sulfoxide.
Production of Platinum
Platinum, along with other platinum group metals, has been commercially obtained as a byproduct of nickel and copper extraction and processing. During the copper electrorefining process, noble metals like silver, gold, and platinum deposit at the bottom of the cell as “anode mud,” which serves as the starting point for platinum group metal extraction.
If pure platinum is found in alluvial deposits or other ores, it is isolated from them through various methods of impurity removal. Since platinum is significantly denser than many of its impurities, lighter impurities are often removed by simply floating them in a liquid. The two impurities, nickel and iron, are removed by passing an electromagnet over the mixture. Because platinum has a higher melting point than most other substances, many impurities are often burned or melted away without the platinum melting. Finally, platinum is immune to hydrochloric and sulfuric acids, while other substances are easily attacked by these acids. Metallic impurities are often removed by stirring the mixture in either of the two acids and recovering the remaining platinum.
An appropriate method for refining raw platinum, which contains platinum, gold, and other platinum group metals, is to treat it with nitrohydrochloric acid. In this process, platinum, palladium, and gold dissolve, while osmium, iridium, ruthenium, and rhodium do not react.
Applications of Platinum
- Catalyst – Platinum is primarily used as a catalyst in chemical reactions. It has been used as a catalyst since the early 19th century. Since then, platinum powder has been used to catalyze the ignition of hydrogen. Platinum is also used in the petroleum industry as a catalyst, especially in catalytic reforming of straight-run naphthas into high-octane gasoline, which becomes rich in aromatic compounds. Its most vital application is in catalytic converters in automobiles, where it enables the complete combustion of low concentrations of unburned hydrocarbons from exhaust gases into water vapor.
- As an Investment – Platinum is a valuable and rich raw material. Platinum is used in jewelry, typically in the form of alloys containing 90-95%, due to its inertness. It is also used for its prestige and intrinsic value as a precious metal. In watchmaking, companies like Rolex, Patek Philippe, Breitling, and others use platinum to produce their limited edition watch series.
- Standard – From 1889 to 1960, the meter was defined by the length of a platinum-iridium alloy bar (90:10), known as the International Prototype of the Meter. The platinum resistance thermometer (SPRT) is one of the four types of thermometers used to define the International Temperature Scale of 1990 (ITS-90), the international standard for temperature measurements. The resistance wire inside the thermometer is made of pure platinum.
- Other Uses – Platinum is also used as an alloying agent for various metal products, including fine wires, non-corrosive laboratory containers, medical instruments, dental prostheses, electrical contacts, and thermocouples. Platinum-cobalt, an alloy consisting of roughly three parts platinum and one part cobalt, is used to create relatively strong permanent magnets. Platinum-based anodes can be found in ships, pipelines, and steel docks. These are some of the diverse applications of platinum, ranging from its role as a standard in defining length and temperature to its use in various industrial and medical applications. Platinum’s unique properties make it a valuable material in a wide range of fields.
Questions and Answers About Platinum
Q1. How can I tell if my ring is genuine platinum?
Answer – All platinum jewelry carries a marking indicating its authenticity. Look for words like “Platinum,” “PLAT,” or “PT,” or preceded by the numbers “950” or “999.” These numbers refer to the purity of platinum, with “999” being the purest.
Q2. Does platinum stick to a magnet?
Answer – Gold, silver, and platinum are not magnetic. It’s important to note that if a metal is attracted to a magnet, it must be an alloy mixture and not a precious metal.
Q3. Does platinum wear out?
Answer – Platinum is very durable. While other precious metals, when scratched, lose metal and wear out, platinum does so at a much slower rate.