Sodium selenite

Sodium selenite is the inorganic compound with the formula. This salt is a colourless solid. The pink coloured pentahydrate is the most common water-soluble selenium compound.

Synthesis and fundamental reactions

Sodium selenite usually is prepared by the reaction of selenium dioxide with sodium hydroxide:
The hydrate converts to the anhydrous salt upon heating to.
According to X-ray crystallography, both anhydrous and its pentahydrate feature pyramidal. The distances range from. Oxidation of this anion gives sodium selenate,.

Together with the related barium and zinc selenites, sodium selenite is mainly used in the manufacture of colorless glass. The pink color imparted by these selenites cancels out the green color imparted by iron impurities.
Because selenium is an essential element, sodium selenite is an ingredient in dietary supplements such as multi-vitamin/mineral products, but supplements that provide only selenium use L-selenomethionine or a selenium-enriched yeast.
The US Food and Drug Administration approved a selenium supplement to animal diets; the most common form is sodium selenite for pet foods. According to one article:
Sodium selenite has been proposed as an effective suicide agent.

Selenium is toxic in high concentrations. As sodium selenite, the chronic toxic dose for human beings was described as about of selenium per day. In 2000, the US Institute of Medicine set the adult Tolerable upper intake levels for selenium from all sources - food, drinking water and dietary supplements - at. The European Food Safety Authority reviewed the same safety question and set its UL at.