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CAS Number: 7631-99-4
Synonyms: E251, nitric acid sodium salt, Chile saltpeter, Peru saltpeter, soda niter, sodium saltpeter, cubic niter, nitratine (mineral form)
Physical Properties: White to colorless crystalline powder or granules (sometimes slightly grayish or yellowish if impure). Very soluble in water (approx. 88 g/100 mL at 20°C; 180 g/100 mL at 80°C). Slightly soluble in ethanol. Insoluble in concentrated nitric acid (passivates). Molecular weight 84.99 g/mol. Melting point 308°C (decomposes at ~380°C releasing oxygen and nitrogen oxides). Density 2.26 g/cm³. pH of 5% solution is 6.0–7.5 (neutral to slightly alkaline). Slightly hygroscopic (absorbs less moisture than sodium nitrite; does not deliquesce easily). Strong oxidizer when molten; supports combustion of organic matter; forms explosive mixtures with reducing agents.
Applications: Cured meat and fish (dry-cured hams such as Serrano, Prosciutto, Parma; country ham; dry sausages like salami, pepperoni, summer sausage; dry-cured bacon; corned beef; canned meats; some smoked fish). Brine for pickled meats. Cheese (surface-ripened cheeses such as Emmental, Gruyère, Gouda, Edam; some processed cheeses to prevent late blowing by Clostridium tyrobutyricum). Fertilizer (high-nitrogen, water-soluble fertilizer for crops including leafy greens, citrus, and tobacco). Industrial uses include heat transfer salt for molten salt storage (sodium nitrite + sodium nitrate + potassium nitrate eutectics), oxidizer in pyrotechnics (rocket propellants, explosives, fireworks), metal treatment (nitriding baths), glass manufacturing (oxidizing agent, decolorizer), laboratory reagent, oxygen source in denitrification studies for wastewater, corrosion inhibitor in cooling systems and oilfield operations.
Description:
Sodium nitrate (E251) is an inorganic nitrate salt that functions as a slow-release source of nitrite in food systems. Unlike nitrites (E249 and E250), nitrates themselves are relatively inert and have weak direct antimicrobial activity. However, nitrate-reducing bacteria such as Micrococcus, Staphylococcus carnosus, Kocuria varians, and Lactobacillus sakei, which are present in dry-cured meats and certain cheeses, reduce nitrate to nitrite via the enzyme nitrate reductase. The generated nitrite then provides the same cured color, flavor, and Clostridium botulinum inhibition as directly added nitrite. This indirect mechanism is why nitrates are used almost exclusively in long-ripened, fermented, or dry-cured products where aging exceeds three weeks, providing sufficient time and microbial activity for nitrate to nitrite conversion.
In products with short curing times or high-heat processing, such as hot dogs and commercial hams, sodium nitrate is ineffective, and nitrites (E249 and E250) must be used directly. In dry-cured hams like Parma ham, which is aged for 12 to 24 months, sodium nitrate is added early, and over weeks to months, bacteria gradually convert nitrate to nitrite, which then forms nitrosomyoglobin and inhibits pathogens. This slow release avoids the need for repeated nitrite additions and ensures that residual nitrite remains low at the time of consumption.
The acceptable daily intake for nitrate expressed as sodium nitrate established by JECFA is 0 to 3.7 milligrams per kilogram of body weight per day. Toxicologically, nitrates themselves have low acute toxicity, with an oral LD₅₀ in rats of approximately 3000 milligrams per kilogram. However, in the human body, about 5 to 10 percent of ingested nitrate is reduced to nitrite by oral bacteria on the tongue dorsum. The resulting nitrite can then react with amines to form N-nitrosamines in the acidic stomach. Additionally, high nitrate intake has been associated with methemoglobinemia in infants, particularly those under six months of age, a condition known as "blue baby syndrome," when nitrates contaminate drinking water or infant formula prepared with high-nitrate well water. This occurs because infant gastric pH is higher (less acidic), allowing bacteria to colonize the upper gastrointestinal tract excessively and convert more nitrate to nitrite, which then oxidizes fetal hemoglobin, which is more sensitive to oxidation, to methemoglobin. For this reason, the European Union limits nitrate in infant foods and drinking water to 50 milligrams per liter.
In adults, nitrate consumption from vegetables such as spinach, arugula, beets, lettuce, and celery is far higher than from cured meats. For example, one serving of spinach (100 grams) contains up to 2000 milligrams of nitrate, while a serving of dry-cured ham contains 10 to 50 milligrams of nitrate. Paradoxically, dietary nitrate from vegetables has been associated with cardiovascular benefits including improved blood flow and reduced blood pressure via conversion to nitric oxide (NO) through the enterosalivary nitrate-nitrite-NO pathway, which is the basis for beetroot juice supplementation in athletes. Therefore, nitrate's reputation as harmful is context-dependent: in infants or with reduced vitamin C intake, nitrate poses risks, while in adults with adequate antioxidants, nitrate may be beneficial.
In cheese manufacturing, sodium nitrate (E251) is added to milk for Emmental and Gouda to prevent "late blowing," a defect caused by Clostridium tyrobutyricum spores that survive pasteurization. The nitrate is reduced to nitrite by starter bacteria, inhibiting clostridia and preserving the cheese's characteristic closed texture. Without nitrate, late blowing causes large gas holes, off-flavors, and swelling of the cheese blocks. No alternative preserves the cheese as effectively while being compatible with traditional production. In industrial applications, sodium nitrate is a key component of molten salt mixtures such as "Solar Salt" (60 percent NaNO₃ and 40 percent KNO₃) used in concentrated solar thermal plants. The salt melts at 220°C and remains liquid up to 600°C, storing thermal energy for electricity generation after sunset. The global demand for sodium nitrate in industrial uses now exceeds its food use. However, in many countries including Japan, Australia, New Zealand, and the European Union, E251 is increasingly being replaced by potassium nitrate (E252) for some applications because potassium nitrate provides potassium, a beneficial nutrient, rather than sodium, aligning with health guidelines to lower sodium intake.
SAFETY INFORMATION ABOUT E251 – SODIUM NITRATE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
