Vanadium (V= 51.3). Although traces of this metallic element occur widely, and in many rocks and minerals, yet it is present to only a very small extent, and occurs in quantity in only a few rare compounds, chief of these being the mineral vanadinite, a vanadate of lead, and mottramite, a similar salt of lead and copper. Its existence was first indicated in 1801 by Del Rio, and thirty years later it was the subject of a careful research by Berzelius. The metal is obtained with difficulty, the best method being the reduction of the chloride by hydrogen. It is a silver-white metal, stable in air under ordinary temperatures. It possesses the most unique property of uniting readily with nitrogen when heated. The metal forms well-characterized chlorides and bromides, but the other salts have been only incompletely studied. The vanadium compounds may be recognized by the bright-green colour given to a borax bead when heated in a reducing flame.