General Description
A yellowish white crystalline solid. Noncombustible but will accelerate the burning of combustible material. If large quantities are involved in a fire or if the combustible material is finely divided, an explosion may result. If contaminated by ammonium compounds, spontaneous decomposition can occur and the resulting heat may ignite surrounding combustible material. Prolonged exposure heat may result in an explosion. Toxic oxides of nitrogen are produced in fires involving this material. Used as a food preservative, and to make other chemicals.
Reactivity Profile
SODIUM NITRITE(7632-00-0) is an oxidizing agent. Mixtures with phosphorus, tin(II) chloride or other reducing agents may react explosively [Bretherick 1979 p. 108-109]. If contaminated by ammonium compounds, spontaneous decomposition can occur and resulting heat may ignite surrounding combustible material. Reacts with acids to form toxic nitrogen dioxide gas. Mixing with liquid ammonia forms dipotassium nitrite, which is very reactive and easily explosive [Mellor 2, Supp. 3:1566 1963]. Melting together wilh an ammonium salt leads to a violent explosion [Von Schwartz 1918 p. 299]. A mixture with potassium cyanide may cause an explosion. Noncombustible but accelerates the burning of all combustible material. If large quantities are involved in fire or if the combustible material is finely divided, an explosion may result. When a little ammonium sulfate is added to fused potassium nitrite, a vigorous reaction occurs attended by flame [Mellor 2:702. 1946-47].
Air & Water Reactions
Soluble in water.
Hazard
Dangerous fire and explosion risk when
heated to 537C (1000F) or in contact with reducing
materials; a strong oxidizing agent. Carcinogen in
test animals; its use in curing fish and meat products
is restricted to 100 ppm.
Health Hazard
Ingestion (or inhalation of excessive amounts of dust) causes rapid drop in blood pressure, persistent and throbbing headache, vertigo, palpitations, and visual disturbances; skin becomes flushed and sweaty, later cold and cyanotic; other symptoms include nausea, vomiting, diarrhea (sometimes), fainting, methemoglobinemia. Contact with eyes causes irritation.
Description
Sodium nitrite is similar in name and use to sodium nitrate.
Both are preservatives used in processed meats, such as salami,
hot dogs, and bacon. Sodium nitrite has been synthesized by
several chemical reactions that involve the reduction of
sodium nitrate. Industrial production of sodium nitrite is
primarily by the absorption of nitrogen oxides into aqueous
sodium carbonate or sodium hydroxide. Over the years,
sodium nitrite has raised some concerns about its safety in
foods, but it remains in use and there are indications that it
may actually be healthy. Sodium nitrite was developed during
the 1960s. In 1977, the US Department of Agriculture (USDA)
considered banning it but the USDA’s final ruling on the
additive came out in 1984, allowing its use. Studies in the
1990s indicated some adverse effects of sodium nitrite, for
instance the potential to cause childhood leukemia and brain cancers. In the late 1990s, the National Toxicity Program
(NTP) began a review of sodium nitrite and proposed listing
sodium nitrite as a developmental and reproductive toxicant,
but a report in 2000 by NTP proposed that sodium nitrite is
not a toxic substance and removed it from the list of developmental
and reproductive toxicants. It is now believed that it
can help with organ transplants and leg vascular problems,
while preventing heart attacks and sickle cell disease.
Definition
ChEBI: An inorganic sodium salt having nitrite as the counterion. Used as a food preservative and antidote to cyanide poisoning.
Definition
sodium nitrite: A yellow hygroscopiccrystalline compound, NaNO2,soluble in water, slightly soluble inether and in ethanol; rhombohedral;r.d. 2.17; m.p. 271°C; decomposesabove 320°C. It is formed by the thermal decomposition of sodium nitrateand is used in the preparation of nitrousacid (reaction with cold dilutehydrochloric acid). Sodium nitrite isused in organic diazotization and asa corrosion inhibitor.
Production Methods
Sodium nitrite, yellowish-white solid, soluble, formed (1) by reaction of nitric oxide plus nitrogen dioxide and sodium carbonate or hydroxide, and then evaporating, (2) by heating sodium nitrate and lead to a high temperature, and then extracting the soluble portion (lead monoxide insoluble) with H2O and evaporating. Used as an important reagent (diazotizing) in organic chemistry.
Flammability and Explosibility
Nonflammable
Environmental Fate
Routes and Pathways, and Relevant Physicochemical
Properties
Sodium nitrite is a strong oxidizing agent at high temperature
and also is a strong supporter of combustion. It is freely
soluble in water (very soluble in water (80%) at 20 °C), and
slightly soluble in ethanol (0.3%) and methanol (0.45%).
Partition coefficient in octanol–water and log Pow is equal to
-3.7. Vapor pressure is 9.9E-17 hPa (7.44E-17mmHg).
Sodium nitrite may explode on heating above 530 °C, is not
combustible but enhances combustion of other substances,
and gives irritating or toxic fumes (or gases) in a fire.
Furthermore, based on the estimated Henry’s law constant at
25 °C ＝2.06E-07 atm-m3 mol-1 for sodium nitrite, volatilization
from water and moist soil surface is not plausible.
Partition Behavior in Water, Sediment, and Soil
This substance dissociates immediately into sodium and nitrite
ions in water. Concentrations of nitrate in rainwater of up to
5mg l-1 have been observed in industrial areas.
Environmental Persistency
In the air, the vapor phase of norethisterone can be degraded by
reaction with photochemically produced hydroxyl radicals
with an estimated half-life of 1.1 h, while the particulate phase
can be removed by wet or dry deposition. Norethisterone is
likely susceptible to photolysis by sunlight because of posing
chromophores that absorb at wavelengths more than 290 nm.
Hydrolysis of norethisterone is not anticipated under environmental
condition because it lacks a functional group to
hydrolyze.
Indirect photo oxidation by hydroxy radicals (1500 000
molecules cm-3) is predicted to occur with a half-life estimated
at 82.3 days.
Purification Methods
Crystallise NaNO2 from hot water (0.7mL/g) by cooling to 0o, or from its own melt. Dry it over P2O5. (See KNO2.)
Toxicity evaluation
Nitrite in blood is highly reactive with hemoglobin and causes
methemoglobinemia. The oxygen-carrying capacity of methemoglobin
is much less than that of hemoglobin. Human is
more sensitive than rat in this respect. So, the primary acute
toxic effects of sodium nitrite in animals results from methemoglobinemia.
The secondary toxic effects of acute sodium
nitrite in animals result in vasodilatation, relaxation of
smooth muscle, and lowering of blood pressure. In humans,
sodium nitrite causes smooth muscle relaxation, methemoglobinemia,
and cyanosis. Also in humans, nitrosating agents
(e.g., nitrous acid and nitrous anhydride that produced from
nitrite under acidic gastric conditions) react with amines or
amides to form nitrosamines or nitrosamides, and the
induction of tumors in animals via endogenous synthesis of
N-nitroso compounds in the absence of inhibitors of nitrosation
such as vitamin C. Nitrosamines need to be activated
metabolically by cytochrome P450 enzymes to electrophilic
intermediates to exert a carcinogenic effect. Nitrosation of
primary amines produces electrophiles that alkylate nucleophilic
sites in DNA. Nitrosation of primary exocyclic amino
groups on DNA, followed by deamination, may lead directly
to mutations.
