Platinum

Platinum is a precious metal, second in value only to rhodium—it is currently worth twice as much as gold. It has a face-centered cubic crystal structure. Platinum is already soft at room temperature (HV 55) and very ductile—it can be cold-worked over 90% by rolling and drawing. Unworked platinum’s elastic modulus is 165 GPa. Despite its high melting point, platinum recrystallizes between 500–550°C. Alloying, with for example rhenium or iridium, improves its physical strength. Also dispersion hardening with finely dispersed oxide particles improves strength at temperatures over 1200°C. Platinum is resistant to glass melts and insoluble in acids, but dissolves in aqua regia to form chloroplatinic acid. Alkalis, cyanides and many other molten salts can corrode it. Platinum is the metal most resistant to oxidation at temperatures over 1200°C, oxidizing only slowly in air to create the volatile oxides PtO and PtO₂. Platinum occurs in compounds with valences of +2, +4 and occasionally 0.

The introduction of mining to the Bushveld Complex near Johannesburg/Pretoria launched South Africa as the top platinum producer in the 20th century. There platinum is found in ores combined with other precious metals—iron/nickel copper/chromium—containing silicates and sulfides (approx. 75% of global output). Other producers include Russia, Canada and the USA. The precious metals present in the ore as chalcogenides or alloys can be concentrated in a complex process using gravity separation, flotation, scorification in a smelter and then bessemerization of the matte. Leaching the matte with sulfuric acid leaves a precious metal concentrate behind. Before separating the individual precious metals, this concentrate is dissolved in oxidized hydrochloric acid, from which platinum can be refined with selective process steps including reprecipitation and ion exchange. The pure platinum as a platinum sponge is further reduced using a wet chemical or separated with an electrolytic process. Secondary sources—such as recycling used catalysts from the petrochemical and chemical industries, and alloys from the glass and chemical fertilizer industries—are particularly important for platinum recovery.

Platinum is primarily used in diverse catalytic applications. Heraeus produces carrier catalysts for purifying exhaust emissions, platinum-rhodium gauzes for chemical fertilizer and hydrocyanic acid production as well as for homogenous catalysis, for example the Karstedt catalyst for hydrosilylation used in silicon production. Heraeus produces a broad array of laboratory equipment, including crucibles, dishes and other special products made from platinum and platinum alloys. The automotive industry utilizes high-quality spark plug electrodes from Heraeus, along with our pastes and semifinished goods in various sensors. Dispersion hardened platinum materials (DPH) developed by Heraeus are used in applications where strength and resistance to high temperatures are crucial. It is also used in feeder systems, large components and glass fiber bushings for the glass industry. Heraeus produces pharmaceutical ingredients containing platinum for chemotherapy drugs, such as cisplatin and oxaliplatin. Heraeus also uses platinum alloys to manufacture electrodes for pacemakers and other precision components for medical technology applications, as well as primary products for the jewelry and dental technology industries.