Platinum: A Noble Metal

The word “Platinum” was derived from the Spanish word platina, which means ‘little silver’. More recently discovered than metals such as iron, copper and gold, Platinum is now the 72nd most common metal in the earth’s crust.

Man’s interest in platinum was only piqued in the 17th century when archaeologists discovered large amounts in South America. 

Platinum is very expensive and rightly so as it is one of the rarest and most precious of metals. According to a 2018 survey, it costs around $30,000 or £20,000 per kilogram, which makes it about $14,000 or £10,000 per pound.

Traces of platinum are extremely rare and usually found in specific regions of the world such as South Africa, Russia, and North America. 

Recycled elements from jewellery and electronics provide a substantial proportion of the total world supply.

The Atomic symbol of platinum is “Pt” and its Atomic number is 78. 

 It can be found deep in the middle of the periodic table in group VII, along with other elements which are mutually known as the “transition metals”. Its close neighbours include Iridium, Osmium, Rhodium, Ruthenium, and Palladium which along with Platinum often make a group called platinum group metals (PGMs). 

The Discovery of Platinum in 1750

Although platinum occurs as grains and nuggets in the alluvial sands of many rivers, there is no evidence of its discovery or use by ancient peoples. 

Charles Wood, a metallurgist and assayer, found platinum in Cartagena in New Spain and took it to Jamaica, then in 1741 sent some of it to his relative, Dr. Brownrigg. In 1750 Dr Brownrigg presented his findings of these specimens to the Royal Society of London. The exhibit included the ore as found in Nature, the purified metal, the fused metal, and a sword with a pummel made partly of platinum.

From the very beginnings of modern industry, the inherent characteristics of platinum - its high melting point combined with its exceptional resistance to corrosion - opened up fields for its application and gave it a unique place in the history of research and invention. 

Platinum Group Metals (PGMs)

The platinum group metal (PGMs), also referred to as The Platinum Group Elements (PGEs) include:

• Platinum (Pt)
• Palladium (Pd)
• Iridium (Ir)
• Osmium (Os)
• Rhodium (Rh)
• Ruthenium (Ru)

Some of the properties of PGMs are high melting points, resistance to corrosion and catalytic properties. These elements are well known for their catalytic properties because they aid in the process of speeding up chemical reactions, without being changed themselves in the process. 

The catalytic properties of platinum were identified in the 1820s when a German chemist, Johann Wolfgang, discovered them.

Naturally occurring platinum-rich alloys were originally found in rivers, mainly in Colombia and Ecuador and they were used for making jewellery.

In the 1500s, Europeans considered platinum worthless because they thought it had no use. Then small chunks of platinum-enriched pieces travelled from South America to Europe during the late 1740s, and in 1750 Platinum was announced as a new metal.

Iridium and Osmium gained recognition in 1803, along with Palladium and Rhodium in 1804 and Ruthenium in 1807.

In chemistry, PGMs and gold are considered Noble metals because they show extraordinary resistance to chemical attack even at extremely high temperatures. 

Silver, copper, gold, and PGMs are the only native metals that occur in their purest form in nature.

Uses of Platinum Group Metals

Along with the use of platinum as jewellery, it has also been widely used in industrial areas. So, what is Platinum used for?:

• In catalytic converters which decrease the harmful carbon and oxide emissions in automobiles.
• To manufacture silicone, plastics and to produce nitric acid, which in turn is used in fertiliser.
• The Petrochemical industry uses platinum as a catalyst to treat gasoline, fuel, oil and petroleum products.
• PGM elements help to increase storage capacities in computer hard disk drives. 
• Also widely used in electronic devices and ceramic capacitors.
• In Glass-manufacturing industries, PGMs are used to produce fibreglass, liquid-crystal and flat-panel displays
• Used as a coating for industrial crucibles in which to manufacture chemicals and synthetic materials.
• Used in medical implants such as pacemakers as it doesn’t corrode inside the body and the risk of allergic reaction is very rare. 
• Also used in the medical drugs industry.
• Platinum alloys are widely used in the jewellery industry, due to their hardness, bright white colour, and anti-tarnishing properties.  
• Platinum, palladium and rhodium are also for investment in the form of coins and bars.

The common uses of platinum are:

• As a catalyst in chemical reactions
• Jewellery making, often used in place of gold
• Platinum-cobalt is used to produce strong magnets
• Oxygen sensors
• Anodes used in pipelines and ships
• Automotive industry: Turbine engines, Spark plugs, Catalytic converters
• Anti-cancer drugs and medications
• Electronics - non-corrosive wires and  electrodes

Physical Properties of Platinum

• Platinum is a shiny, white-grey metal.
• It is both flexible and ductile.
• It can be thinned down to a flat sheet of 100 atoms (thinner than aluminium foil)
• It can be modified into very thin wire.
• It has an excellent resistance to corrosion even at relatively high temperatures and pressures.
• The atomic weight of platinum is 195.084 u.
• It has a melting point of about 1,773°C or 3,223°F.
• Platinum has a boiling point of around 3,827°C or 6,921°F.
• Its density is about 21.45 grams per cubic centimetre, which makes it one of the densest metals.

Chemical properties of Platinum

• Platinum is a moderately inactive metal, so it does not decay or tarnish when it is exposed to air.
•  It is acid-resistant but it will dissolve in Aqua regia (a mixture of hydrochloric acid and nitric acids)
• Platinum also dissolves in extremely hot alkalis. Such as sodium hydroxide and lime water.
• At high temperatures, platinum absorbs massive amounts of hydrogen.
• Platinum occurs naturally in the form of 6 isotopes: 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt. 
• The Electrochemical equivalent is 1.816 g/A/h.
• It has an Electronegativity of 2.2 and an Electrode potential of 1.2V
• The Ionic radius of platinum is 0.650 Å.

Mechanical properties of Platinum

• The tensile strength of platinum is 125-165 MPa.
• Platinum’s modulus of elasticity is 171 GPa.
• The Poisson’s ratio of platinum is 0.39.
• The Platinum has a shear modulus of 62 GPa.
• The hardness grade for platinum in the MOH hardness scale is 4-4.5.

Thermal Properties of Platinum

• The thermal expansion coefficient of platinum at 20°C/68°F is 9.10 µm/m°C.
• The thermal conductivity of platinum is 69.1 W/mK.

Platinum Jewellery Making

Within the jewellery making industry, both PGMs and platinum are used. 

Rhodium is frequently used as a plating for white gold and silver because of its non-tarnishing properties.  

Palladium and iridium are commonly alloyed with other metals or used alone to make jewellery pieces. The most common platinum alloys can include 90-95% platinum and 10% iridium or 5% ruthenium. For stronger and harder alloys, ruthenium is mainly used. 

Due to the rare occurrence of PGMs, platinum jewellery is considerably more expensive than gold jewellery. 

The history of using platinum for jewellery-making dates from 2,000 years ago when indigenous South American people made rings and other ornaments out of platinum. Egyptians used it in the 7th century BC, whereas Europeans started using it in jewellery making in the 18th century. Currently, China is the largest market for platinum jewellery.

How to Polish Platinum Jewellery

Polishing of Platinum jewellery is not an easy task. Polishing takes more effort and cost than it would do polishing other metals. 

Other metals leave their surface area with abrasive manipulation, however, when platinum is scratched or abraded, it actually moves the metal instead of losing the surface finish. This gives it the advantage of durability and contributes to its strength, but means the polishing of platinum requires specific tools. 

It is pertinent to highlight that any scratches on platinum jewellery that aren’t removed in the early stages of fabrication do not go away with repeated polishing.

When platinum is used in conjunction with gold or other metals, the platinum must be polished first or polished separately otherwise the other metals will be over-polished.

After cleaning the metal there are two ways to polish the metal; mass tumbling or hand polishing for more precise polishing.

When an item is tumbled it will usually always need further polishing by hand. Take a look at the Eternal Tools range of polishers particularly suitable for polishing platinum jewellery:

• EVEflex Technik: 900 grit Extra fine, Light Green
• Diatwist Single: radial polishing twist discs
• Diamond Polishing Paste
• Rubber Silicone Polishers: mounted in various shapes and sizes
• Dialux: Green and Grey polishing compounds
• Diapol diamond polishers
• Diamond abrasive polishing cloths
• Airflex Heat-free polishing wheels
• EVE Chrom Plus: silicone carbide abrasives
• EVE Soft Wheel: Use the green soft wheel as a final polish after EVE Chrom Plus

There are three steps involved with rotary and vibratory finishing. First, the platinum surface is attacked by tumbling the pieces in an abrasive compound, using ceramic media designed for heavy cutting. Thereafter,  a soap-based compound and a ceramic media with a finer grit can be used. And finally, stainless steel shot with a detergent. 

Platinum in Medical Sciences

Since the early 1970s, platinum has been used biomedically in various medical fields to treat ailments such as cardiac anomalies, stroke, and neurological conditions. Durability, flexibility, inertness within the body, electrical conductivity, non-corrosiveness and biocompatibility, make platinum the best choice for use in medical devices. 

The major uses of platinum biomedically are as follows:

• For body implants due to its outstanding biocompatibility. Unlike copper and nickel, it does not corrode inside the body.
• Platinum serves as an ideal electrode material due to its conductivity. 
• It is shown clearly in an X-ray, so doctors can easily monitor the device during the treatment.
• In cardiac disorders, platinum is used to make components for stents, defibrillators, pacemakers and catheters.
• Widely used in neuromodulation devices such as brain pacemakers to treat disorders like Parkinson’s disease and Alzheimer’s
• In cochlear implants to restore hearing to patients.
• As an Anti-cancer drug. Cisplatin is a simple platinum compound found by scientists in 1845. This played an important role in making testicular cancer less invasive in patients. Cisplatin, along with its successor drug, Carboplatin, is also extensively used in the treatments of breast cancer, lung and ovarian cancer.

Electronic applications of Platinum

• Platinum has been used in thermocouple devices to measure temperature.
• Platinum and its group metals are used in coating electrodes.
• Used in wires and other electronic components to make a barrier for corrosive and high-voltage environments.
• The optical storage systems and high-density hard disk drives have magnetic coating which is made up of platinum.
• Used to generate huge amounts of fibreglass, liquid-crystal display (LCD), cathode ray tubes and flat-panel displays.

 

Industrial Applications of Platinum

• Used as a catalyst in the production of nitric acid.
• Used in the manufacture of fertilisers.
• Refining crude petroleum with a platinum catalyst yields high-octane petrol but also a range of chemical intermediates required for the production of plastics, synthetic fibres, dyestuffs and pharmaceuticals. 
• Used in the manufacture of optical glass and fibre-glass.
• Used in the invention of the fuel cell enabling space to be conquered and man’s journey to the moon to be accomplished.

Pros and Cons of Platinum

Platinum conjures up expense, luxury and the greater things in life: Platinum credit cards, A music album that’s gone platinum, 70 years of marriage is a Platinum wedding anniversary. Its connotation with such things is not an accident. It is the rarest of all precious metals and its rarity in nature only makes it more desirable. However, just like every coin with two sides, platinum also has some advantages and disadvantages.

Pros

• Platinum is extremely durable and robust so it is an excellent choice for jewellery that is worn on a daily basis. It retains its perfect look as compared to other metals because it can tolerate extreme temperatures.
• It is hypo-allergenic so can be worn on the body or within the body with no adverse side effects.
• The silvery-white colouration of platinum makes a set diamond sparkle more prominently.
• Platinum jewellery looks better with age. The patina that occurs over time from marks can improve the look of a platinum ring, although you can always have it polished back to its original sheen.
• Non-corrosive. Meaning it won’t tarnish, rust, decay or oxidise.
• It can be thinned, flattened and made into wire or tubing

Cons

This Noble metal has just two disadvantages

• Price. More expensive than pure gold.
• Scarcity. Its rareness makes it extremely expensive.

Global Target Markets of Platinum

Platinum is rare but it is still the third most-traded metal in the world after silver and gold. The demand of using platinum throughout the world varies according to different industries. Today, Platinum is mainly used in the automobile industry, jewellery making, medical sciences and other industrial areas.

In the automobile industry, platinum is used in the construction of auto catalysts. These autocatalysts are coated with platinum and other metals and are inserted inside a vehicle’s exhaust line, which helps to moderate the release of harmful exhaust fumes. The platinum auto catalysts convert harmful hydrocarbons and carbon monoxide into carbon dioxide, water vapours and nitrogen, which helps in controlling air pollution. 

The second largest demand for platinum is for the use of jewellery making.  Modified with other metals so that it can be easily moulded make it ideal for crafting jewellery. 

There are several other uses of platinum that work efficiently in different industries. Platinum and its group metals are used to make fertilizers for the fields, silicone making, hard disk drives, electronic devices, dental fillings and implants, glass-manufacturing and sensory devices used in homes. 

Platinum is used in various medical devices that are used to measure blood gases to detect oxygen. It is also used in catheters, stunts and various neuromodulation devices because of its durability, elasticity and biocompatibility. Along with that, it is also used in making anti-cancer drugs, the common one being Cisplatin.

Global Platinum Jewellery Market

Platinum is considered as one of the most precious metals in jewellery making because of its rarity, durability and strength.

Its natural colour is silver-white and is considered as much as thirty times more rare than gold. 

The higher the value of the piece of jewellery, the higher the percentage of platinum within it.

Hypoallergenic and heavy in weight so is mostly used to secure diamond settings and some luxury brand watchmakers also make limited-edition platinum watches.

Rings are the most common ornament in platinum jewellery, followed by earrings and necklace sets.

The Global platinum jewellery market is distributed into different types of products such as rings, necklaces, bracelets, earrings, anklets and watches. In terms of distribution channels, the platinum market is divided into franchise stores, online retailers and selling as independent vendors.

The platinum jewellery market is spread into the areas of North America, Europe, Asia Pacific, the Middle East, the African region and South America. North America is estimated to dominate the global platinum jewellery market, followed by Asia Pacific and Europe. 

These regions have a major share in platinum jewellery making because of their urban lifestyle, rise in economy and high spending rate on goods. India and China are also considered as newly emerging countries in the Asia Pacific in the platinum market.

Some of the leading manufacturers in the platinum jewellery market are Harry Winston, Société Cartier, Van Cleef & Arpels, Buccellati Holding Italia, Tiffany & Co., Graff, Bulgari S.p.A, Piaget, Chopard, and Mikimoto America among others.

Mining/Extraction of platinum

Platinum alloys are found in concentrated sands and river banks known as placer deposits. Most of these placer deposits are found in Russia. 

In the 19th century, platinum alloys from the Ural mountains were heavily mined. In the past few years, significant amounts of platinum deposits have been mined from two regions in Russia: the Kondyor mine in the Khabarovsk region and the Koryak mine in Kamchatka which produced 185,000 oz of platinum in 2005.

The drilling process has been taking place in some platinum-rich countries (mentioned above) and it is estimated that another 2,200 metric tons of PGM are present. 

Mining has been done to 900m below the surface but the bottom of the ore deposit is not yet touched. A rough geological estimate suggests that almost 1,000 to 6,200 metric tons of PGMs are present at the very bottom. 

The mining process of platinum is relatively simple. Platinum-bearing sand is scooped from mines or riverbeds. The sand is then washed until platinum grains or nuggets appear and then pulled from the remaining substance. Platinum is also mined in the form of ores. 

Most of these ores are found deep in the surface of earth so explosives are required to extract them and break them into several pieces. The broken rock is then collected and taken to the surface for further processing where it is crushed through machines and mixed with water to bind it with other metals.

In the flotation separation process, air bubbles carry platinum particles to the surface and then those particles are collected and dried into powder form. One ton of dried powder may contain 85 to 850 g of PGMs. To remove impurities, the powder is heated at extremely high temperatures. 

Air is used to eliminate unwanted iron and sulphur, and further chemical processes are used to remove any base elements from the powder. 

In the final stage, the mineral concentrate is dissolved in aqua regia and then filtered and purified to obtain pure platinum metal.

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Due to its high efficacy, durability and extraordinary strength, platinum is becoming a demand in the modern world. This Noble metal along with its other group metals is of great strategic importance to the industrial world.