Sodium nitrite, NaN02, is a fire-hazardous, air-sensitive, yellowish-white powder that is soluble in water and decomposes at temperatures above 320°C (608 °F). Sodium nitrite is used as an intermediate for dyestuffs and for pickling of meat, in dyeing of textiles, in rustproofing, in medicine, and as a reagent in organic chemistry.
1. To produce nitrogen oxide gas oxidation, with sodium hydroxide or sodium carbonate solution absorption. Reduction of sodium nitrate with lead, heating, and melting sodium nitrate, adding a small amount of lead metal, stirring, and continuing to heat all the oxidation of lead. The resulting mass was partitioned into small pieces while cooling, and the resulting lead oxide was extracted several times with hot water. Carbon dioxide gas leads to the formation of lead carbonate precipitation, filtered, diluted with nitric acid, and accurate filtrate, evaporation, and concentration of precipitation of sodium nitrite crystals. After suction filtration, washed with ethanol and then dried, and then recrystallization derived.
2. With caustic soda solution or soda ash absorption of nitric acid or nitrate production in the exhaust contains a small amount of NO and NO2 of tail gas, tail gas NO / NO2 ratio to be adjusted to neutralization liquid NaNO2 and NaNO3 mass ratio of 8 or less, During the absorption process, the neutralization solution should avoid acidity to avoid corrosion of the equipment. When the relative density of the liquid is 1.24 ~ 1.25, soda ash content of 3 ~ 5g / L is sent to evaporate, at 132 ℃ when the absorption liquid evaporation concentration, and then cooled to 75 ℃, precipitation of sodium nitrite crystallization, Drying to obtain the product.
3. Nitric acid nitrate production of exhaust gas in the exclusion of nitric oxide nitrogen dioxide, with soda ash or caustic soda solution absorption in the neutralization solution, by evaporation, crystallization, and then use sodium nitrite and sodium nitrate in water Solubility and the separation of the two, that is finished.
4. 42.5g of sodium nitrate and 100g of metal lead in the porcelain (or iron) crucible in the melt stirring, cooling with 200mL hot water extraction, through the CO2 a few minutes to precipitate dissolved in water lead oxide, iron ions. The filtrate was acidified with dilute nitric acid and evaporated to dryness. Then add 200 ~ 250mL ethanol in the residue on the boil, filter the filtrate to remove a small amount of sodium nitrate, distillation of the filtrate to remove ethanol, and get a white powder, sodium nitrite about 20g. Purification: 100g sodium nitrite in 70 ~ 80 ℃ dissolved in 100mL water, add 1 ~ 2g pure sodium hydroxide to precipitate iron, cooling filtration, evaporation crystallization, the second recrystallization higher purity, yield 75g.
5. The absorption method. The ratio of nitric oxide to ammonia dioxide in the exhaust gas discharged from the production process of dilute nitric acid is adjusted so that the mass ratio of nitrite to sodium nitrate in the neutralization liquid is 8 or less. And then from the bottom of the exhaust gas from the absorption tower, soda solution from the top of the absorption tower absorbs nitrogen oxides in the gas to generate neutralization fluid. The relative density of the neutralization solution is 1.24 ~ 1.25, the sodium carbonate content of 3 ~ 5g / l, the evaporation concentration, cooling crystallization of 50 ~ 70 ° C precipitation of sodium nitrite crystals, and then by centrifugal separation, obtained sodium nitrite finished. The reaction formula is as follows. The mother liquor separated by centrifugation is used as a raw material for producing sodium nitrate.
6. 1 part of industrial sodium nitrite dissolved in 1.5 ~ 2.0 copies of 70 ~ 80 ℃ of pure water. Add solid reagent sodium hydroxide, adjust the PH value of 12, standing precipitation, and then filter. The filtrate was evaporated to a density of 1.45 and filtered. The filtrate was cooled to room temperature and precipitated sodium nitrite crystals were filtered through a Buchner funnel and stirred continuously, washed with a small amount of cold water, and then transferred to a mill mouth flask. The mother liquor can be re-evaporated to yield a large amount of sodium nitrite, but recrystallization is required.
7. Ethyl nitrate in sodium hydroxide solution by adding ethyl nitrite, placed two days, the following reaction: the volatile matter, the residue filtered out (sodium nitrite content as high as 91% to 96%) after recrystallization in water, available And the content of sodium nitrite is 95.5% to 99.8%.