The name molybdenum derives from the word used by the Greeks, molybdos, for galena and other lead ores. Until the middle of the 18th century, it was supposed that molybdite or molybdenite were identical to graphite, then known as "plumbago" or "black lead". In 1778, K. W. Scheele, in its "Treatise on Molybdena", showed that, unlike the graphite, the molybdenite formed a "peculiar" white earth when treated with nitric acid. He proved that it had acid properties and called it "acidum molybdenae", which means, molybdenic acid. He also considered that the molybdenite mineral was a molybdenum sulfite. Later, in 1782, P. J. Hjelm isolated the element, in the form of a metallic powder, by heating up molybdenic acid with charcoal. In 1893, German chemists obtained the metal with 96% degree of purity and, the following year; Henri Moissan reached 99,98% by reduction of the element in an electrical oven. The first register of an alloy made with molybdenum dates from 1894.