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Metalworking and applications

British scientist John George Children was the first to melt a sample of iridium in 1813 with the aid of "the greatest galvanic battery that has ever been constructed" (at that time). The first to obtain high-purity iridium was Robert Hare in 1842. He found it had a density of around 21.8 g/cm (0.79 lb/cu in) and noted the metal is nearly immalleable and very hard. The first melting in appreciable quantity was done by Henri Sainte-Claire Deville and Jules Henri Debray in 1860. They required burning more than 300 litres (79 US gal) of pure O and H gas for each 1 kilogram (2.2 lb) of iridium.

These extreme difficulties in melting the metal limited the possibilities for handling iridium. John Isaac Hawkins was looking to obtain a fine and hard point for fountain pen nibs, and in 1834 managed to create an iridium-pointed gold pen. In 1880, John Holland and William Lofland Dudley were able to melt iridium by adding phosphorus and patented the process in the United States; British company Johnson Matthey later stated they had been using a similar process since 1837 and had already presented fused iridium at a number of World Fairs. The first use of an alloy of iridium with ruthenium in thermocouples was made by Otto Feussner in 1933. These allowed for the measurement of high temperatures in air up to 2,000 °C (3,630 °F).

In Munich, Germany in 1957 Rudolf Mössbauer, in what has been called one of the "landmark experiments in twentieth-century physics", discovered the resonant and recoil -free emission and absorption of gamma rays by atoms in a solid metal sample containing only Ir. This phenomenon, known as the Mössbauer effect resulted in the awarding of the Nobel Prize in Physics in 1961, at the age 32, just three years after he published his discovery.