On a laboratory scale, the melt-phase reduction of alkali nitrates (preferably NaNO3 is used) with metallic lead is suitable for the production of nitrites:
NaNO3 + Pb ==> NaNO2 + PbO
One melts 1 mol (85 g) sodium nitrate in an iron crucible of approx. 15 cm diameter and 1 mole (207 g) of metallic lead (cut into small pieces) is added slowly with good agitation. After all the lead is added, the mixture is agitated for a further 30-45 minutes until all the lead is oxidized. Careful agitation is important for the achievement of a good yield. After cooling the reaction mixture, the solid cake left is cut up into smaller pieces and placed in a larger iron container. The formed sodium nitrite is extracted with 200ml of warm water, followed by two 75ml portions of water, and the insolubles is filtered off (Caution: Lead oxide is very poisonous!). To remove remaining lead from the aqueous solution, carbon dioxide is bubbled through for one minute (not longer!) and the insolubles again filtered off. After neutralization with dilute nitric acid, the solution is concentrated under vacuum. The first crop of crystals which precipitates consist largely of sodium nitrate. Now the solution is evaporated to dryness, and the still molten residue (consisting of sodium nitrite contaminated with some sodium nitrate) is washed briefly with ethanol. Care must be taken not to heat the sodium nitrite much higher than its melting point (271°C) as the compound decomposes at 320°C, with evolution of nitrogen oxides.
Could some german bee please check my translation carefully, as german is my third language.