NaHSeO3

NaHSeO3, also known as sodium hydrogen selenite or monosodium selenite, is an inorganic salt consisting of the sodium cation (Na+) and the hydrogen selenite anion (HSeO3−). The compound forms a white, crystalline solid that dissolves readily in water, giving solutions that are mildly acidic because the HSeO3− ion is amphiprotic. In aqueous solution, the pH of moderate-concentration solutions is typically around 5.

Preparation and occurrence: NaHSeO3 can be prepared by neutralizing selenous acid (H2SeO3) with sodium hydroxide: H2SeO3 + NaOH → NaHSeO3 + H2O. It may also be generated by partial neutralization of sodium selenite (Na2SeO3) under controlled conditions.

Reactions: In solution, the hydrogen selenite anion can be oxidized to selenate (SeO4^2−) with suitable oxidants. It can be reduced by strong reducing agents to elemental selenium or to selenide species. Thermal or chemical conditions can lead to decomposition or transformation to related selenium oxides.

Applications: NaHSeO3 is used as a source of the selenite ion in inorganic synthesis and analytical chemistry, providing access to selenium-containing intermediates and reagents. It serves as a precursor to other selenium compounds.

Safety: Sodium hydrogen selenite is toxic and should be handled with care to avoid ingestion, inhalation, or skin contact. It can pose hazards to aquatic organisms. Appropriate personal protective equipment and disposal procedures for hazardous chemicals should be followed.