Pyrolysis of sodium nitrite

Sodium nitrite Molecular formula: NaNO2 Molecular weight: 69.00 Properties and uses: It belongs to the amine category; it is a white or slightly yellow rhombic crystal that is soluble in water and liquid ammonia, slightly soluble in methanol, ethanol, and ether. It has strong hygroscopic properties and is used as a mordant in fabric dyeing； Bleaching agents for silk and linen, metal heat treatment agents ； Steel corrosion inhibitor ； Antidotes for cyanide poisoning, laboratory analysis reagents, used as colorants, antimicrobials, and preservatives in meat product processing. Density is 2.168 g/cm3, melting point is 271°C, and it decomposes at 320°C. It is hygroscopic, soluble in water, its aqueous solution is stable, it exhibits basic properties, it can absorb oxygen from the air, and it forms sodium nitrate. Sodium nitrite is toxic, and there are rumors that it is a carcinogen; however, in reality sodium nitrite itself is not a carcinogen. What is carcinogenic is nitrosamine, which is formed from sodium nitrite under certain conditions. In the sodium nitrite molecule, the oxidation state of nitrogen is +3. It is an intermediate oxidation state that possesses both reducing and oxidizing properties; for example, in acidic solutions it can oxidize KI to elemental iodine. This reaction can be carried out quantitatively and can be used to determine nitrites. Sodium nitrite is widely used in the dye industry and organic synthesis, often in the production of azo dyes, nitrogen oxides, drugs, rust inhibitors, as well as in printing, bleaching, and meat curing. Due to its toxicity, care must be taken when using it. Sodium nitrite has high thermal stability and can be prepared by high-temperature thermal reduction: Pb (powder) + NaNO3 = PbO + NaNO2. The product PbO is insoluble in water; the mixture after the reaction is dissolved in hot water, filtered, and recrystallized to yield white crystalline sodium nitrite. 　　Oxidizing and reducing properties: The N in (NO2)- has a +3 oxidation state, so it possesses both oxidizing and reducing properties. 　　In acidic media: HNO2/NO = 0.99 V, it possesses strong oxidizing capacity. 　　2(NO2)- + 2I- + 4H+ == 2NO + I2 + 2H2O 　　2NO2- + 2H+ = NO + NO2 + H2O 　　It can react with both oxalic acid and acetic acid, which are quite weak acids. 　　Due to the presence of NO+ in the acid, it readily accepts electrons to form NO, thus making it easy to oxidize I-. This is the difference reaction between nitrous acid and dilute nitric acid. Acidic solutions of nitrates cannot oxidize I-, due to the aforementioned kinetic reasons. It also exhibits reducibility in the presence of strong oxidizing agents. 　　5(NO2)- + 2(MnO4)- + 6H+ ==== 5(NO3)- + (Mn)2+ + 3H2O. It tends to disproportionate in the absence of oxidizing agents and reducing agents. 　　Sodium nitrite is also used as a color enhancer in food, particularly in meat products. However, due to its carcinogenicity, excess levels are not allowed. Sodium nitrite: Pharmacologically, it can convert hemoglobin into methemoglobin; its mechanism of action in detoxifying cyanides is similar to that of methylene blue, but it is more effective than methylene blue. Suitable for the treatment of cyanide poisoning. 　　The conventional lethal dose is 3 g. Sodium nitrite is an important azotization reagent; the azotization reaction it undergoes with aromatic amines is one of the most commonly used reactions in the dye industry. It can also be used as a mordant, bleaching agent, metal treatment agent, and electroplating corrosion inhibitor. Additionally, it is used in the production of potassium nitrite and azo dyes. Under acidic conditions, it exhibits strong oxidizing properties and weak reducing properties. 　　Sodium nitrite is an industrial salt; although it resembles table salt, sodium chloride, it is toxic and not suitable for consumption. Sodium nitrite is highly toxic; ingestion of 0.2 to 0.5 grams can cause poisoning symptoms in humans, while consuming 3 grams at once may lead to death. Sodium nitrite poisoning is characterized by cyanosis, with symptoms and signs including headache, dizziness, fatigue, chest tightness, shortness of breath, palpitations, nausea, vomiting, abdominal pain, diarrhea, as well as cyanosis of the lips, nails, and the skin and mucous membranes throughout the body. In severe cases, convulsions and coma may occur, and the condition can even be life-threatening. 　　If cyanosis due to methemoglobin occurs, methylene blue can be used to reduce methemoglobin. 　　Ingesting sodium nitrite causes poisoning because the iron contained in hemoglobin in the human body is in the ferrous form; this iron can bind to oxygen and, through blood circulation, deliver oxygen to various parts of the body. When sodium nitrite is ingested, a chemical reaction occurs in the blood, causing hemoglobin to transform into hemoglobin with trivalent iron. Hemoglobin with trivalent iron cannot carry oxygen, thus causing hypoxic poisoning in the body. Furthermore, sodium nitrite is also a carcinogen. Therefore, ingesting sodium nitrite can cause serious harm to health. 　　To distinguish sodium nitrite from table salt, the sample can be placed in a sulfuric acid solution containing potassium iodide, and then starch can be added. If it appears blue, it proves that the sample is sodium nitrite. The iron contained in hemoglobin in the human body is ferrous; it can bind to oxygen and, through blood circulation, deliver oxygen to various parts of the body. When sodium nitrite is ingested, a chemical reaction occurs in the blood, causing hemoglobin to transform into hemoglobin with trivalent iron. Hemoglobin with trivalent iron cannot carry oxygen, thus causing hypoxic poisoning in the body. It is produced in accordance with the national standard GB1907 as a food additive, and should be added in amounts specified by GB2760. The maximum allowable amount in meat products is 0.15 g/kg, while the residual amount of sodium nitrite in canned foods must not exceed 0.05 g/kg ； Meat products must not exceed 0.03g/kg. 　　The standard set by the World Committee on Food Hygiene Sciences in 1992 for the safe intake of sodium nitrite in the human body is 0–0.1 mg/kg body weight ； Converted to nitrite, the standard is 0–4.2 mg per 60 kilograms of body weight; using and consuming it according to this standard will not cause harm to the human body. Sodium nitrite is toxic; excessive intake can cause toxic side effects by paralyzing the vasomotor center, the respiratory center, and the peripheral blood vessels, leading to the formation of methemoglobin. Acute poisoning is characterized by general weakness, headache, dizziness, nausea, vomiting, diarrhea, a feeling of pressure in the chest, and difficulty breathing ； On examination, significant cyanosis of the skin and mucous membranes was observed. In severe cases, blood pressure drops, leading to coma and death. 　　Additionally, sodium nitrite can also produce carcinogenic substances in the human body. Newly pickled kimchi also contains sodium nitrite (which is why it is best to consume kimchi 15 days after it has been pickled, as the level of nitrites in it gradually decreases).