Tuesday, 24 June 2014

“A quantity of platina was purchased by me a few years since with the design of rendering it malleable for the different purposes to which it is adapted. That object has now been attained. ” William Hyde Wollaston

On the 4th of June this year, for the first time since its inception in 1831, a woman - Professor Maureen Raymo of the Lamont-Doherty Earth Observatory, Columbia University, U.S.A. was awarded the highest award granted by the Geological Society of London – The Wollaston Medal. (Read about Professor Raymo here) 
         The Wollaston Medal                Professor Raymo receiving her medal .
The medal is named after William Hyde Wollaston and was originally made in Palladium – a new metal that he identified in 1803.
Wollaston was a brilliant man as well as being a noted philosopher and a shrewd business man, he made many contributions to science in a wide range of fields including important discoveries in chemistry, physiology, physics, botany, crystallography, optics, astronomy and mineralogy. He not only has this medal named after him but also the mineral Wollastonite and Isla Wollaston off the south coast of Chile - But it is his contributions to the world of metallurgy that I will write about in this blog.
The uninhabited Isla Wollaston off the south coast of Chile - brrrrr

Wollastonite - the mineral named after William Hyde Wollaston
He was born in Norfolk, England on August 6 1766, the second of 14 children of Francis Wollaston and Althea Hyde. He had a good education at Charterhouse School then Cambridge University from which he graduated with a degree in medicine. After seven years he stopped being a physician and to moved to London where he became involved with the Royal Society and pursued his many research interests. It is his experiments with the "newly discovered" metal called Platinum that lead to innovations  important for the world of Jewellery.
Platinum (from the Spanish word "platina" meaning "silver") is one of the Platinum Group of Metals (PGMs), the others being Palladium, Rhodium, Iridium, Osmium ( identified by Wollaston)  and Ruthenium, the six metals naturally occur in the same ore bodies.The PGMs are the densest known metal elements, highly durable and as they are exceptionally rare, expensive! 
Platinum was used by pre-Columbian Indians and ancient Egyptians - as seen in the Casket of Thebes, dating from 700BC, a box is decorated with hieroglyphics in gold, silver and an alloy of the platinum group metals. 
Platinum was re-discovered in the 16th century in South America. Whilst serving in South America from 1735 to 1746, the Spanish explorer and astronomer Antonio de Ulloa collected samples of platinum. He later wrote a report about the metal, describing how it was mined and used and because of this, De Ulloa is often given credit for discovering platinum. At this time platinum was seen as just a nuisance mixing with the gold nuggets and being difficult to separate from them, it had no special value to them.
The earliest European written reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger.  He refers to a noble metal "which no fire nor any Spanish artifice has yet been able to liquefy." 
European scientists and metallurgist were intrigued by the new metal but its properties, high melting point and great resistance to corrosion, presented a tough challenge to to them trying to understand and use the metal. Wollaston formed what appears to be a business partnership with a Cambridge friend Smithson Tennant to explore this new metal. It was during experiments in methods to refine platinum Wollaston discovered another metal which he name Palladium, followed in 1804 by Rhodium, Iridium and Osmium. Also at this time Wollaston perfected a method of producing malleable platinum. This now opened up a commercial opportunity, platinum that could be worked to provide corrosive resistant components for the gunmakers as well as durable laboratory equipment.
Among his first platinum products were crucibles and lids, marketed through William Cary, a well 
known London instrument maker. This can be seen at the London Science Museum.

By 1808 Wollaston was able to produce and market his malleable platinum in large quantities and the business prospered rapidly. His shrewd business sense lead to him keeping his method secret so that he made a considerable amount from his process. This was not a greed motivated action, it provided funding into his other experiments and research. Unfortunately his source of unrefined platinum dried up and by 1820 and he was no longer able to continue with this business. Just before his death in he disclosed the method he used, not that dissimilar to the methods used today. 

The Exceptional William Hyde Wollaston 1766-1828

A collection of notebooks and documents was discovered in the Department of Mineralogy and Petrology of the University of Cambridge in 1949 turned out to be the valuable Wollaston papers. The collection, now in the Cambridge University Library, includes twenty laboratory notebooks in Wollaston’s hand, eight of them devoted entirely to the purchase, purification, production and sale of platinum. One dealing with metal palladium, and three contain miscellaneous experiments on a wide range of subjects, including early research on crude platinum.

PGM's in Jewellery

  • Platinum - The availability of workable platinum saw the 18th century European court jewellers producing jewellery items in platinum and this continued with the great jewellers of the Edwardian and Art Deco periods such as Cartier and Tiffany. Today it is a popular precious metal for jewellery settings.  Platinum is commonly alloyed with other platinum group metals - palladium, ruthenium and iridium - and copper and cobalt to improve its manageability and durability.
    Among the main advantages of platinum jewellery are its strength and resistance to tarnish. It can be repeatedly heated and cooled without hardening and oxidation effects.
Cartier Platinum Art Nouveau Ring

  • Palladium - In 2009 the UK Hallmarking Act was amended by Parliament to incorporate palladium as a metal which requires hallmarking. Having received official recognition as a precious metal in its own right, compulsory hallmarking of palladium items weighing 1g came into effect as of January 1, 2010. Palladium has increased in popularity for jewellery items and like platinum it is strong and resistant to tarnishing. It is also used to make springs in analog watches.
  • Rhodium - although too brittle to be used to make settings it is a good hardener for platinum and palladium. Rhodium also makes a lustrous, hard coating for other metals in such items as table silver and is electroplated onto white gold to give a bright white finish.
  • Iridium - in jewellery, iridium is used in platinum/iridium alloys to strengthen the platinum. On its own It is an extremely brittle metal and therefore liable to crack if knocked. It also has an extremely high melting point making it difficult to work with, nor can it be sized.
  • Ruthenium - discovered in 1844 by the Russian chemist Karl Klaus. Ruthenium and platinum alloys have a high resistance to wear and are used in the manufacture of jewellery.
  • Osmium - is not used in jewellery making although Osmium-platinum alloys are used to strengthen the tips of quality fountain pens.
Other Facts about the PGMs
Platinum is one of the rarest elements - estimated to be about 0.01 parts per million in the Earth's crust. It can take up to six months to produce one ounce of high grade platinum from seven to 12 tonnes of mined ore. Once extracted the platinum rich ore this is ground up, the particles are then mixed with reagents (a reagent is a substance used in a chemical reactions to detect, measure, examine or produce other substances) and air is pumped through. Platinum-containing particles float to the top forming a froth. The froth is skimmed-off, dried out and smelted at temperatures exceeding 1,500° C, causing the separation of the platinum metal. The process is termed "Froth Floatation" read about it in detail here.
Other Applications:
PGMs are most often used as catalysts because of their chemical stability,
Some examples of other applications include: in the petroleum industry  - the catalyst in a catalytic converter  - Platinum is the most active catalyst and is widely used,  Palladium and rhodium are also used, in pacemakers and other medical implants (iridium and platinum), as a stain for fingerprints and DNA (osmium), in the production of nitric acid (rhodium), and in chemicals, such as cleaning liquids, adhesives and paints (ruthenium).
Further Reading -
Read about the other achievements of Wollaston.
Read in detail about the Wollaston and Tennant work with Platinum (no.9)

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