Preparation and Properties of Selenium IV Oxide

Preparation and Properties of Selenium(IV) Oxide. Selenium compounds are very poisonous Hand in the prepared substances and residues of selenium preparations to the laboratory assistant. Run all experiments with selenium in a fume cupboard After work, thoroughly wash the ware and your hands. 

Assemble an apparatus as shown in Fig. 75. Pour 50-100 ml of a concentrated nitric acid solution into 250-ml three-neck flask 1, 

Weigh 0.2-0.5 g of selenium and put it into refractory tube 4 sealed at one end (about 30 cm in length and 4 cm in diameter). 

Lower several pieces of copper shavings into three-neck flask 1, and carefully switch on water-jet pump 8. When the entire apparatus is filled with nitrogen oxides, heat the part of the tube where the selenium is with the flame of a gas burner. First heat carefully, and then more strongly. What occurs  

As copper dissolves in the nitric acid, add new portions of copper shavings to it. When the entire selenium is oxidized, disconnect the flask with nitric acid, and suck a stream of dry air through the apparatus. Extract the prepared selenium(IV) oxide from the tube, put it into a weighing bottle, and weigh it. Determine the yield in per cent. Write the equations of the reactions. Test the properties of selenium(lV) oxide (see p. 116). Hand in the preparation to your instructor. 

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