The history of palladium naturally starts with the history of platinum and the platinum group metals of which palladium is a member. Whether platinum was recognized as a separate body by early civilizations is doubtful. Traces of it have been found among artifacts from ancient Egypt, the best known example being a small strip of native platinum set on the surface of a box among many hieroglyphic inscriptions, dated to the seventh century BC and from Thebes. It had been hammered out in the same fashion that Thebian craftsmen treated silver, and most likely had been mistaken by them for silver.
The most successful early exploitation of platinum occurred rather in the Americas – the New World – by the Esmeraldas people in the coastal region of Northern Ecuador many centuries before the arrival of the Spanish. Small pieces of jewelry, rings, pendants, etc., have been found made of platinum or of platinum and gold combined, which displayed significant and sophisticated metallurgical skill. William Farabee, distinguished anthropologist of the University of Pennsylvania (1865-1925) wrote about one find:
“The native Indian workers of Esmeraldas were metallurgists of marked ability; they were the only people who manufactured platinum jewelry. In our collection will be seen objects of pure platinum, objects with a platinum background set with tiny balls of gold used to form a border, and objects with one side platinum and the other side gold.”
The Indian’s metallurgic method aroused considerable curiosity, and further study by others pointed to the conclusion that they had used a quite sophisticated technique of powder metallurgy – sintering in the presence of a liquid phase. Radio carbon dating has placed the date of these artifacts to between the first and fourth centuries AD.
Photomicrographs of some samples, both of objects identified as starting materials and of finished pieces, clearly showed the presence of sintering and the dispersion of platinum particles in a gold matrix. Few of platinum finds from Ecuador or Columbia have an archeological context, unfortunately, because they were found by treasure hunters. Jewelry appears to have continued to be made up until the time of the conquest. Many centuries passed before the Spanish rediscovered the source of the platinum and longer yet before the scientists of Europe could make it malleable and useful.
The Spaniards Use of Gold & Platinum
The Spanish interest in the resources of their conquests was centered on gold. Quite early in their explorations of the coastal areas, the Spanish learnt that gold was present in the Choco region, a long narrow strip of country between the Andes and inland from the Pacific. Access problems prevented early exploration: high temperatures, extreme rainfall, dense jungle, swamps, meandering rivers and hostile natives. In the 1560s several small expeditions did report finding deposits of gold and another metal which later became called platina. By 1690 the Choco region became settled and pacified, and exploitation of mineral resources began.
Although the sources of gold found in alluvial deposits here were among the richest known then in the world, they found themselves dealing with what most likely seemed to the Spanish a big nuisance. Concentrated in the gold in washing were white grains like small shot accompanied by heavy black magnetic sands. A great deal of labor was required to remove it, either by labor intensive sorting by hand or by a process of amalgamation, which was expensive, required difficult-to-obtain mercury and was not especially effective. This nuisance material was, in fact, platinum deposits which occurred in varying amounts.
The Spaniards called this white metal Platina, a derogatory diminutive of plata, their word for silver. A few ornaments and utensils were fabricated from this metal after Spanish craftsmen perhaps learned some of the Indian methods of working with it. In 1557, Julius della Scalla noted the difficulty of melting the metal obtained from the Spanish American possessions. Scientific investigation of the platinum metals did not occur for another 200 years, however. In 1753, a small bag of platinum was sent to Spain with the note:
“In the Bishopric of Popayan, Suffragan of Lima, there are several gold mines among which there is one called Choco. In a part of the mountains which contain it there is a large quantity of a sort of sand which the people of this country call platina and white gold.”
William Bowles, an Irish naturalist working for the Spanish government, was asked what uses the metal could be put to. He investigated the material and reported:
“Platina is a metallic sand that is sui gneris which can be very pernicious in the world because it mixes easily with gold and because, although by chemistry it is easy to find the means of recognizing the fraud and of separating the two metals, since this means would be available only in the hands of a few people and as cupidity is a general malady, temptation seductive, the means of deceiving easy and in everybody’s reach, there can be great danger in letting platina loose in commerce.”
Platina was thus prohibited for export from New Granada to Europe. That did not stop the fraudulent use of patina for gold, however. Colonial escudos and doubloons have been found made of platinum, then gilded to look like gold.
All of the gold output from Choco went to two mints, at Santa Fe de Bogota and Popayan, where a second, final separation of the metals was done. The excess platinum was thrown into the Bogota River “two leagues” from Santa Fe or into the Cauco, about 1 league from Popayan.
After 1759, samples of platinum were collected from these dumps to be sent to Europe for scientific investigation. Other samples had already reached Europe, either legitimately or through smuggling.
Palladium was finally isolated from platinum and identified as a separate elemental metal in 1803 by William Hyde Wollaston, a brilliant researcher who made many contributions to science. Wollaston made important discoveries in astronomy (the dark lines in the solar spectrum, a crucial tool in stellar astronomy today), biochemistry (he discovered cystine, the first amino acid), physiology (he was the first to postulate that human hearing is limited to certain frequencies), and physics (in atomic theory and crystallography).
The Wollaston Medal is named after him: the highest award granted by the Geological Society of London, first granted in 1832. (It was originally made of palladium.) He even had an island in the Arctic named after him, in recognition of a navigational instrument he invented.
Wollaston had formed an association with Smithson Tennant to conduct experiments in chemistry. As the 19th century dawned, that platina is dissolved in aqua regia was well known, with an insoluble black residue remaining. The partners decided between them that Wollaston would investigate the soluble portion and that Tennant would examine the insoluble residue. Wollaston then was able to separate out palladium in 1802 and rhodium in 1804. Tennant announced his discoveries of indium and osmium in 1804.
Wollaston’s process began with with platina - a natively occuring platinum mix which came from South America. To refine it, the common practice was to dissolve it in aqua regia (a mixture of hydrochloric and nitric acids). Adding ammonium chloride would then cause the platinum to precipitate out of solution in the form of an insoluble complex salt. Wollaston went further, adding iron, and treating the precipitate again with aqua regia. Adding iron a second time, he obtained a new precipitate, different than the previous ones.
When he treated this new precipitate with nitric acid, he obtained a reddish solution. This readily combined with mercury into an amalgam that when decomposed by heat left a new white metal.
Wollaston initially named his discovery “ceresium,” after the newly-discovered asteroid Ceres. But he soon changed it to palladium, after a different new asteroid: Pallas, which in turn was named after the Greek Goddess of wisdom.
Wollaston didn’t announce his discovery; he apparently thought it would have commercial value, and didn’t want to tell others how to make it. In April 1803, he anonymously printed notices of palladium’s properties, and made it available for sale in a Soho shop.
Other scientists were skeptical, especially chemist Richard Chenevix. He believed that palladium was a fraud; he suspected it was only an alloy of platinum, and not a new metal at all. Chenevix even claimed to have created his own palladium by combining mercuric oxide, platinum, aqua regina, and ferrous sulfate.
Wollaston rebutted Chevenix’s claims, anonymously offering a reward of twenty pounds to anybody who could synthesize palladium. After many failures, chemists finally accepted palladium as a new metal.
Wollaston finally went public with his discovery in February of 1805. His secrecy over palladium put him into disfavor with scientists of the day who favored open communication to further scientific progress. Nonetheless, the importance of his contributions were recognized; the prestigious Royal Medal from the Royal Society was awarded to him for solving the riddle of malleable platinum. He made and sold the metal for years but refused to reveal the process until shortly before his death in 1826.
About the same time Wollaston began separating palladium, John Dalton began the study of a new field of study on atomic weights. He began with the gases, and in 1804, turned to metals. This landmark thinking inspired Swedish chemist J. J. Berzelius to propose determining the atomic weight of all elements then known. By 1814 he published a tentative table, based on oxygen taken as 100. The table included numbers for palladium, platinum and rhodium. He also proposed the use of the now familiar chemical symbols. We acquired Pt for platinum, while his initial proposal for palladium was Pl, and was later revised twice, ending with the present Pd. A number of compounds of the platinum metals saw exploration. A rose colored salt formed from palladium with ammonia and chlorine was reported in 1813.
Wollaston continued to refine and market platinum group metals for various applications. He was most successful marketing platinum, but considerably less so with palladium, and without a market for it, his stocks of palladium continued to grow. It was a metal that was available before technology found uses for it. Wollaston did market the metal for use in analytical weights. Eventually he gave a considerable quantity of palladium to the Royal Society. Unfortunately, Wollaston’s supply of native platinum ended in 1820, when he ceased offering his products to industry.
Percival Norton Johnson, son and former apprentice of assayer John Johnson who had a close relationship with Wollaston, in 1817, formed a gold refining company and began refining gold, the beginnings of what became the Johnson Matthey Company. Johnson took up refining platinum when Wollaston abandoned his work. Brazilian gold, which had high palladium content, became a specialty largely because his refinery was the only one capable of refining the ore and separating the palladium. Like Wollaston, he had trouble finding an outlet for the large stores of palladium he began to collect. He marketed the metal for use in chemical balances, for rust free surgical instruments, use as lighthouse reflectors, and as a substitute for steel in some circumstances, such as pen tips.
In 1820 Humphrey Davy first observed the process of catalytic oxidation, describing it as a “perfectly new principal in combustion.” It was German Johann Wolfgang Döbereiner though, who carried on the experimentation to fully understand the process, finding that platinum group metals in a fine powder, had the power to unite oxygen and hydrogen even at low temperatures.
The 1820s also saw the discovery of platinum metals in Russia, though rumors had persisted from earlier. In 1825, the Imperial Russian Government declared native platinum to be a State Monopoly, and required a state license for any dealings in associated metals. All refining was to take place at the St. Petersburg Mint. One result of this was the growth of a robust smuggling enterprise, with the metal finding its way out of Russia through black market channels. Russian successes at separating platinum from gold, rendering it malleable and producing utensils from it were noteworthy. Russian scientist Peter Grigorievich Sobolevsky made important headway in his research given that Wollaston’s process had not yet been published.
The 1830s saw discoveries of a number of properties of this group of metals. Michael Faraday’s experiments in electrochemistry provided further scientific insight for the platinum group metals. Faraday often used platinum plates as electrodes because it was resistant to reaction with the other elements involved. He coined the terms we still use today: anode, cathode, electrolysis, and electrolyte. William Robert Grove, chemist and lawyer, added to the experimentation and quite notably, developed the first platinum based fuel cell. During 1832, English chemist and astronomer Sir John Herschel made a remarkable discovery with platinum concerning the effect of light on certain chemical reactions, a discovery that placed his name among the inventors of photography. Swedish chemist J. J. Berzelius experiments with and coins the term “catalysis”. Real progress in applications of catalysis in industry would wait many decades.
In 1840, a researcher named Alfred Smee published a landmark book entitled “Elements of Electrometallurgy” in which he described the processes of plating with both platinum and palladium through the use of a galvanic current. He called the process platinating or palladiating. For palladium plating, Smee used nitro-muriate of palladium as an electrolyte, and a palladium anode, though the process did pose some difficulties.
Other researchers improved on the process through the decade. Another platinum group metal, ruthenium was discovered. During this period, the Russians, who had been using platinum for currency were now fighting an uphill battle using it. Coinage in platinum ceased, ending the sole commercial demand for the metal that had not yet developed other uses.
Mining output from the Urals collapsed. George Matthey who began an apprenticeship with Percival Johnson as a teenager, took charge of the firm’s platinum laboratory at age 20.
The 1850s began with a notable new partnership. George Matthey was successful in negotiating an arrangement with one of the Russian mine owners to be the sole platinum refiner and selling agent. One of palladium’s most important properties was discovered as a result of researches of Thomas Graham, London chemist. In 1854, he was investigating how red-hot platinum absorbed hydrogen and discovered it could do so for an indefinite period of time, and no other gases produced the remarkable effect. Turning to palladium, he found that it could absorb 5 or 6 hundred times its own volume in hydrogen. When exposed to coal gas, only the hydrogen penetrated the palladium. This decade also saw considerable improvements in the achievement of high temperatures for melting metals. In France, the use of coal gas and oxygen in blow pipes were investigated, and using crucibles of lime or magnesia, achieved some success with platinum. Using these principals, Frenchmen Deville and Debray devised a process to refine native platinum and filed patents in France and Britain in 1857. The British rights were immediately acquired by George Matthey.
The 1860s saw further progress in the commercial melting of platinum metals, though a problems with purity remained a concern. Separately in Germany, the firm Haraeus developed their own method for casting platinum. The growth of more available platinum metals fueled further search for applications. In 1867, an international metallurgical exhibition held in Paris was a huge success for the platinum products of Johnson Matthey, featuring over 15,000 ounces of platinum products including huge boilers. Scientific research of the 1860s and into the 1870s was influenced by the rise of German militarism and unification under Prussian dominance orchestrated by Otto von Bismarck with wars with Austria (1867), then France (1870-1871).
In 1888, rich copper nickel ore was discovered in Ontario, Canada containing some PGMs, but the successful extraction of these would wait years.
For over a hundred years, palladium was fairly rare. It had been produced in limited quantities from various sources. The Ural Mountains of Russia provided the vast bulk of the ores from which palladium was produced. Then in 1924, the great stores of South Africa were found.
Still, palladium could only be obtained from platinum ore by methods similar to Wollaston’s, or else by electrolytic refining of copper. But in 1930, the International Nickel Company of Canada began producing palladium in significant quantities from its rich ores, and the metal became more widely available.
For the first time, industry had affordable palladium, and was able to put its unusual properties to work. In 1931, a German company named Heraeus developed and patented alloys of palladium with silver and gold. These alloys were excellent materials in dentistry, and today are still used in bridges and crowns.
In the 1970s, another important application emerged. Growing concerns about pollution and the environment triggered a surge in pollution-reduction technologies. Thanks to its unique physical characteristics, palladium soon became an important part of these systems.
Modern catalytic converters rely heavily on palladium and its sister metal, platinum. These devices convert up to 90% of harmful gases in auto exhausts (hydrocarbons, carbon monoxide, and nitrogen oxide) into less harmful substances (nitrogen, carbon dioxide, and water vapor). Today, each car or light truck sold in the USA must have a catalytic converter.
Since the 1970s, demand for palladium has skyrocketed in other industries as well. Modern electronic circuitry uses palladium in electrical switches and contacts, for its superior conductivity and resistance to oxidation. Palladium pastes are also used in electronic components such as capacitors.
Today, palladium is in a unique situation. The metal is in demand from a wide range of global industries, yet is supplied by only a few mines across the world. Thus, any interruption to supply can have a dramatic impact on prices.
A perfect example of this occurred a few years ago. The biggest palladium supplier in the world is Norilsk Nickel in the Russian Federation, and in the year 2000, Norilsk’s deliveries of palladium became unreliable. The palladium market then was so tight that supply interruptions resulted in huge price surges. Palladium reached a high of $1090 per ounce in early 2001. Palladium is for the moment in oversupply and at less than a quarter of its high, but questions remain with many about future supply reliability.
Today, scientists are studying even more uses for palladium. The white metal is playing an especially key role in fuel cell research. The fuel cell is an exciting new technology: a device that combines hydrogen and oxygen, producing electricity, heat, and water, with virtually no pollution. The fuel cell promises to completely transform modern society, and palladium plays an important role in current research.
Truly, palladium is a metal for the 21st century!