Selenium dioxide

• Selenium ( IV) oxide
• Selenigsäureanhydrid

White, hygroscopic needles

Fixed

3.95 g · cm -3 ( 15 ° C)

315 ° C

16 hPa ( 70 ° C)

Soluble in water ( 384 g · l -1 at 20 ° C)

Risk

0.05 mg · m-3

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Selenium dioxide ( SeO2 ) is a solid that sublimes from 315 ° C. It is formed for example by the combustion of elemental selenium (Se) with oxygen.

Other oxides of selenium are Selenmonoxid ( SeO ) and selenium trioxide ( SeO3 ).

Properties

Selenium dioxide forms shiny, white, sublimatable needles. When heated under pressure to an orange-yellow melt forms.

Selenium dioxide is highly soluble in water and acts hygroscopic. With water it forms are called (IV ) selenious acid ( H2SeO3 ), a medium strong acid, its salts or Selenite oxoselenates. This seems less reducing than the related sulfurous acid, in an acidic environment, however it is an oxidizing agent:

Similarly, selenium dioxide is readily soluble in alcohol and concentrated sulfuric acid.

With concentrated strong acids may be selenium dioxide hydrolysis selenium ( IV) compounds such as selenium oxychloride ( SeOCl2 ) form.

Production

Selenium (IV ) oxide is produced directly from the elements selenium and oxygen or through water. Withdrawal from selenious acid

Use

Selenium dioxide is used as the oxidizing agent in the synthesis of organic substances such as Riley - oxidation.

If severe forms of scales are available, selenium dioxide is used as an additive in shampoos.

Safety

Selenium dioxide as selenium and its compounds highly toxic. The MAK value (calculated on selenium ) is 0.1 mg / m³. His recording can be done through the intact skin. Required labor protection: dust mask, rubber gloves, suction and ventilation at the workplace.