Magnesium Nitrite, Mg(NO₂)₂

Magnesium Nitrite is usually prepared by interaction between barium nitrite and magnesium sulphate, and has also been obtained by treating silver nitrite with magnesia or with magnesium chloride.

The trihydrate, Mg(NO₂)₂.3H₂O, crystallises in deliquescent leaflets which are yellowish or snow-white. It slowly decomposes in a stoppered bottle, and its solution decomposes, evolving nitric oxide when evaporated on the water-bath.

Careful concentration under diminished pressure, or under diminished pressure over sulphuric acid, results finally in the dihydrate. This has also been obtained by digesting magnesium sulphate and sodium nitrite with 94 per cent, alcohol and evaporating under reduced pressure. It occurs as a hard, efflorescent, white mass or as clear crystals, and is much more stable than the trihydrate. It does not usually dissolve to a clear solution, and may partially decompose on continued dehydration.