Preparation and Properties of Tellurium IV Oxide

Preparation and Properties of Tellurium(IV) Oxide. Tellurium compounds are poisonous Run experiments with tellurium in a fume cupboard Even negligible amounts of tellurium and its compounds getting into a human organism cause an odour of garlic that does not vanish for a long time. 

After completing work, thoroughly clean up your workplace and wash the ware with concentrated hydrochloric acid or aqua regia. Wash your hands with soap. Hand in the prepared substances and residues of tellurium preparations to the laboratory assistant. 

Put 3-5 g of powdered tellurium into a 0.5-litre beaker. Wet the tellurium with distilled water, pour 30-50 ml of concentrated hydrochloric acid into it, and add 10-30 ml of concentrated nitric acid in small portions. Heat the reaction mixture, covering the beaker with a watch glass. If the tellurium does not dissolve completely, dilute the reaction mixture up to one-third of its volume with water, and filter the solution through a fluted filter wetted with a 5% solution of hydrochloric acid. Add 100 ml of hot water (80 °C) to the filtrate while constantly stirring it. What is observed  

Neutralize the solution with ammonia up to a weakly acidic reaction (pH 3-4), using methyl red as an indicator. Test with the indicator as follows apply several drops of it onto filter paper placed on a glass plate, and in the course of neutralizing the solution being tested take a sample of it with a glass rod and transfer it onto the filter paper with the indicator. 

Filter off the precipitated substances (what is its composition ) on a Buchner funnel, rinse it with water to remove chloride ions. 

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