at. no. 42, at. wt. 95.95, metal, row 6, col. 7B, val. 3-4-6, orbits 2-8-18-13-1

{Merck Index - © 1952 by Merck & Co., Inc.}

Molybdenum. Mo; at. wt. 95.95; at. no. 42; valence 3-4-6. Discovered in 1778 by Scheele; isolated in 1782 by Hjelm. Its most important ores are molybdenite, MoS2, and wulfenite, PbMoO4. Methods of preparation: Pokorny, et al., cited in Gmelins Handbuch der anorg. Chemie 53, 21 (1935).

Dark-gray or black powder with metallic luster or coherent mass of silver-white color; body-centered cubic structure. m. 2622°:

Worthing, Phys. Rev. [2] 25, 846 (1925); b. about 4510°: Zwikker, Physica 7, 74 (1927); d. 10.2. Fairly stable at ordinary temperature; oxidized to the trioxide at a red heat; slowly oxidized by steam. Not attacked by water, by dilute acids or by concentrated hydrochloric acid. Practically insoluble in alkal. hydroxides or fused alkalies. Soluble in nitric acid, in hot concentrated sulfuric acid, in fused potassium chlorate or nitrate. Attacked by fluorine at ordinary temperature, by chlorine or bromine at a red heat.

Use: In the form of ferromolybdenum for manufacturing special steels for tools, boiler plate, rifle barrels, propeller shafts; for manufacturing high-speed tool steels; electrical contacts, spark plugs, X-ray tubes, filaments, screens and grids for radio tubes.

Commercially available.

{Mineral Deficiencies in Plants}

The role of molybdenum has not been determined. It has been shown to be essential to the nodule organism of legumes and appears to be concerned in nitrogen changes in plant tissues, e.g. nitrate reduction.

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