Rhenium oxychloride

When the system is free from oxygen, all portions of the tube are flamed to drive out moisture. If any water remains, it will react with rhenium pentachloride to form oxychlorides. When the tube is dry, the nitrogen is cut off, and chlorine introduced. Commercial chlorine that has been dried by sulfuric acid C has been found satisfactory. 

If a pure product is desired, the tube is sealed off at the first constriction after all of the pentachloride has been decomposed. The product is shaken into bulb D, the tube inclined at an angle of 45°, and the chloride sublimed under reduced pressure at a temperature of 450°C. An asbestos shield placed at the point where the tube enters the furnace will assure condensation of trichloride just beyond the edge of the furnace. The product is sublimed twice, allowed to cool to room temperature, and the tube broken just above and below the point where the trichloride has formed. The dark-red crystalline mass may be powdered, transferred to a weighing bottle, and stored in a desiccator without fear of decomposition. Exposure to direct sunlight should be avoided because of the formation of oxychlorides under such conditions. The yield is usually about 60 to 65 per cent based upon the quantity of rhenium used. In one experiment, 38 g. of twice resublimed rhenium trichloride was prepared with a yield of 68 per cent. 

Perrhenate is also leached with water from a sample melted with Na2C03 or NaOH. Rhenium heptoxide, Rc207, is volatile and can be separated by distillation at 260-280°C from a concentrated sulphuric acid medium [1,17,18]. It may be accompanied by As(III), Hg, Se, and to a lesser degree by Sb, Te and Mo. In the presence of hydrochloric acid, rhenium distils as the oxychloride at a lower temperature, but As, Ge, Hg, Sn, Se, Mo, Te, and T1 are wholly or partly co-distilled. In view of the partial co-distillation of Mo, Re cannot be directly determined in the distillate. In the distillation of Re, carbon dioxide or air is used as the carrier gas. 

Chemical identification is a desirable method for detection of a new element Chemical identification of the elements immediately beyond hahnium (element 105) should be possible, but rapid chemical reactions will be required. Chemical properties can be predicted with the help of the periodic table shown in Fig. 24.1, which indicates that elements 106,107, 108, etc., should be chemical homologs, respectively, of tungsten (W), rhenium (Re), osmium (Os), etc. The utilization of volatility properties perhaps offers the best possibility for very rapid chemical identification. The hexafluoride and hexacarbonyl of element 106 (eka-tungsten) should be quite volatile and the hexachloride, pentachloride, and oxychlorides... 

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