Selenous acid
Dihydrogenselenit (IUPAC)
White, hygroscopic crystals
Fixed
3.004 g · cm -3
Decomposes above 70 ° C
- Very soluble in water
- Well in ethanol
Risk
0.02 mg · m-3
11 mg · kg -1 ( LD50, mouse, i.v.)
Template: Infobox chemical / molecular formula search available
Selenious acid is a water-soluble crystalline solid with the molecular formula H2SeO3. It is a dibasic acid of selenium. Its salts are called Selenite. Selenious acid is toxic.
Production and representation
Selenious acid can be made from the reaction of selenium dioxide and water or nitric acid with selenium.
Chemical Properties
Selenious acid is highly soluble in water and is highly hygroscopic. Dissolved in water, it reacts strongly acidic ( pKa of the first protolysis: 2.62 and the second protolysis: 8.32 ).
It is a weaker acid than the sulfur dioxide, but, in contrast to this can be isolated as crystals. It shows practically no reducing properties. Of sulfur trioxide, hydrogen sulfide, hydrogen iodide and hydrazine it is reduced to red selenium.
Hydrogen peroxide, potassium permanganate or chlorine acid it is oxidized to selenium acid.
Use
Selenious acid is used as catalyst for the synthesis of 1,2 -dialdehyde.
In industry they are used for the color change of the metallic materials. Especially in the arms industry is a ' blueing ' procedure known to be stained with the steel surfaces. Similar methods used in the chemical industry for surface discoloration, such as copper. In the United States there are drug tests whose Schlüsselreagenz is selenious acid.
Biological Significance
Selenious acid as selenium many compounds toxic to the human body. Under German law, the water connection to the water hazard class 3 is characterized. The median lethal concentration for fish is 6.61 g · m- third There are signs of a possible carcinogenic effect of the compound. The biological limit value is 150 ug · l -1.
Safety
Selenious acid acts on the skin, respiratory tract and mucous membranes strong irritant. It is able to destroy living tissue in high concentrations ( corrosion ). Suspension with the compound over a prolonged period can cause serious physiological damage. Selenious acid is already in the smallest quantities of highly toxic. In intoxication with selenium compounds to be reckoned with permanent damage.