Tungsten chloride, anhydrous

Fused Salt Electrolysis. Only light RE metals (La to Nd) can be produced by molten salt electrolysis because these have a relatively low melting point compared to those of medium and heavy RE metals. Deposition of an alloy with another metal, Zn for example, is an alternative. The feed is a mixture of anhydrous RE chlorides and fluorides. The materials from which the electrolysis cell is constmcted are of great importance because of the high reactivity of the rare-earth metals. Molybdenum, tungsten, tantalum, or alternatively iron with ceramic or graphite linings are used as cmcible materials. Carbon is frequently used as an anode material. 

Undoubtedly, the best method for the production of pure anhydrous lanthanide trihalides involves direct reaction of the elements. However, suitable reaction vessels, of molybdenum, tungsten, or tantalum, have to be employed silica containers result in oxohalides (27). Trichlorides have been produced by reacting metal with chlorine (28), methyl chloride (28), or hydrogen chloride (28-31). Of the tribromides, only that of scandium has been prepared by direct reaction with bromine (32). The triiodides have been prepared by reacting the metal with iodine (27, 29, 31, 33-41) or with ammonium iodide (42). 

Praesodymium metal can be obtained from its anhydrous halides by reduction with calcium. The metal also may be prepared by electrolysis of fused praesodymium chloride at elevated temperatures (about 1,000°C). Alternatively, an eutectic mixture of praesodymium chloride, potassium chloride, and sodium chloride may be electrolyzed. In such electrolysis graphite is the anode and tungsten the cathode. 

Tungsten Hexafluoride, WFg, is obtained by the action of anhydrous hydrogen fluoride upon tungsten hexaehloride in platinum vessels, or by the interaction of antimony peiitafluoride with the hexa-chloride. It is a solid at low temjreratures just above 0° C. it sublimes to a heavy gas which fumes in moist air it reacts with water with production of tungstic acid. It attacks both glass and mercury by alkalies it is decomposed, and with alkali fluorides it forms double salts. 

An ethereal solution of a Grignard reagent reacts readily with CO in the presence of anhydrous chromium(III) chloride (Job, 1927). One of the products is the ether-soluble Cr(CO)g. If the CrClg is replaced by MoClg orWClg the hexacarbonyl of molybdenum or tungsten is formed. 

Chromium forms a cyclopentadienyl compound similar to ferrocene (p. 499). Cyclopentadienyl sodium reacts with anhydrous chromium (I I) chloride in tetrahydrofuran to give red (C5H5)2Cr. By oxidising this, compounds containing the (C5H5)2Cr+ ion are easily obtained (Cotton and Wilkinson, 1954). When cyclopentadiene mixed with molybdenum or tungsten carbonyl is passed through a tube heated to 300 the dicyclopentadienyl hexacarbonyl is formed (Wilkinson, 1954) ... 

Beryllium Sulphide.—Wohler (1828 2) supposed he had made a sulphide by heating the metal with sulphur, but Fremy (1853 1) states that it was the only sulphide he could not produce by I>assing the vapor of carbon disulphide over the hot oxide. De-bray (1855 i) and Nilson and Pettersson (1873 3) state that beryllium and sulphur do not combine when heated together. Berzelius (1826 2) supposed he produced a double sulphide of bci yllium and tungsten, but his results lack confirmation. Lebeau (1899 ii) at last made the sulphide by heating the anhydrous chloride and iodide with. sulphur or with hydrc en sulphide. Also by the action of sulphim vapor on the carbide at a high temperature, lire. sulphide is a white solid, immediately decomposed by water. No other details are given nor further study of this compound been made. 

Anhydrous chromium(II) chloride, synthesis 40 Tungsten (VI) chloride, synthesb 44... 

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