Of all the metal refined today, 90% is iron. Patent databases contain hundreds of thousands of patents concerned with inventions around iron and its alloys. Iron chemical compounds have many uses. Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction used in welding (Mold For Thermite Welding And The Like (1925)), and purifying ores (Beneficiation Of Euxenite Ore (1971)).
Iron forms binary compounds with the halogens (Process for oxidizing iron halides to produce iron oxide and chlorine (1953)), and the chalcogens (Iron Chalcogenide Nanocomposite And Method For Preparing Same (2014)).
Ferrocene was the first organometallic sandwich compound and was discovered in the early 1950s. Soon after, patent applications for ferrocene derivatives started to be filed (Dialkyl and diacyl derivatives of ferrocene and processes for the preparation thereof (1956)).
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All patent information has been obtained from Espacenet (European Patent Office).