ABSTRACT
Prior to the eighteenth century, the principal ore of molybdenum, molybdenite, was confused with graphite and lead. Back then, lead referred to any black mineral that left a mark on paper. It was not until 1778 that the Swedish chemist Carl Wilhelm Scheele conrmed that molybdenite was not the element lead (known commonly as galena) or graphite. Scheele identied the new element as molybdenum, named after the ore in which it was found. Peter Jacob Hjelm successfully extracted and puried molybdenum from molybdenite in 1781. The biological signicance of molybdenum
13.1 Historical Background ........................................................................................................487 13.1.1 Determination of Molybdenum Essentiality .........................................................487 13.1.2 Roles of Molybdenum in Plant Physiology ............................................................488
