Molybdenum is a chemical element in the periodic table. Its symbol is Mo and its atomic number 42. Metal is lustrous, silvery, and fairly soft when pure. Usually obtained as gray powder. Used in alloys, electrodes, catalysts, and as the sulfide, lubricants.
Diagnostic tests: On charcoal molybdenum sulfide gives near the assay a copper-red stain in oxidizing flame and white oxide further away. On plaster, mixed with KI, gives a deep ultramarine blue color after heating with the flame. Bead tests using sodium phosphate (Na3PO4) gives a yellowish green color (hot) and nearly colorless (cold), the reducing flame color is a fine green. Molybdates (MoO42-) are tested by adding powdered sample to a dry test tube with a scrap of paper, adding a few drops of water and an equal amount of concentrated H2SO4. The mixture is carefully heated until the acid fumes. Cool or slowly add water and the solution will assume a deep blue color. If the molybdenum is in the form of the oxide or the sulfide then a yellowish green flame test may be diagnostic.