POTASSIUM NITRITE

CAS Number: 7758-09-0 (also 7758-09-0 for pure)
 Synonyms: E249; Nitrous acid potassium salt; Potasium nitrite (common misspelling); Kaliumnitrit (German); Nitrito de potasio (Spanish)
Physical Properties:
Appearance: White to slightly yellow deliquescent granules or crystalline powder.
Solubility: Very soluble in water (approx. 312 g/100 mL at 25°C); slightly soluble in ethanol; insoluble in diethyl ether.
Molecular weight: 85.10 g/mol.
Melting point: 441°C (decomposes above ~350°C to potassium oxide, nitrogen oxides, and oxygen).
Density: 1.915 g/cm³.
pH (5% solution): 7.0–9.0 (slightly alkaline due to hydrolysis to nitrous acid and KOH).
Oxidizing properties: Strong oxidizing agent (can accelerate combustion and cause fire in contact with reducing agents, organic matter).
Stability: Deliquescent (absorbs moisture from air); slowly oxidizes to potassium nitrate (KNO₃) in air; decomposes in acidic conditions releasing toxic NOx gases.
Applications:
Cured meat and fish products (E249): Bacon, ham (raw and cooked), corned beef, pastrami, hot dogs (frankfurters), sausages (salami, pepperoni, chorizo, bratwurst), bologna, luncheon meats, canned meats (Spam-type products), and cured fish.
Cheese: Some processed cheeses (very limited use, mostly replaced by nitrates).
Industrial (non-food): Corrosion inhibitor (in boilers, cooling water, oilfield brines), antidote for cyanide poisoning (generates methemoglobin to bind cyanide), laboratory reagent (diazo coupling reactions for nitrosamines synthesis and Griess test for nitrite detection), rubber vulcanization accelerator, heat transfer salt (mixed with sodium nitrite/nitrate for solar thermal plants).
Description:
 Potassium nitrite (E249) is an inorganic salt used as a food additive primarily for curing meat and fish. Along with sodium nitrite (E250), it serves three critical functions: (1) development of the characteristic pink-red color of cured meats (by reacting with myoglobin to form nitrosomyoglobin), (2) contribution to the distinctive cured flavor (via lipid oxidation products and spice interactions), and (3) inhibition of the outgrowth and toxin production of Clostridium botulinum (the causative agent of botulism) – arguably the most important safety function. The mechanism of color formation: nitrite in acidic meat environments (pH 5.5–6.0) forms nitrous acid (HNO₂), which decomposes to nitric oxide (NO). NO then binds to the heme iron of myoglobin (the oxygen-carrying protein in muscle), forming nitrosomyoglobin – a red, heat-stable pigment that remains pink after cooking (whereas uncured meat turns brown/gray due to metmyoglobin formation). The antimicrobial action against C. botulinum and other bacteria (Listeria monocytogenes, Staphylococcus aureus, Clostridium perfringens, Bacillus cereus) involves multiple mechanisms: (a) inhibition of iron-sulfur cluster enzymes required for energy metabolism, (b) disruption of membrane function, (c) reaction with thiol groups in proteins, and (d) generation of reactive nitrogen species (peroxynitrite, nitrogen dioxide) under acidic conditions. In the US, potassium nitrite is permitted up to 200 ppm (calculated as NaNO₂ equivalent) in cured meats when used with sodium ascorbate or erythorbate (which accelerate NO formation and inhibit nitrosamine formation). Potassium nitrite is often selected over sodium nitrite in low-sodium formulations because the potassium salt provides approximately 45% less sodium per gram of nitrite ion (since the counterion K⁺ replaces Na⁺). The main safety concern with nitrites is the formation of N-nitrosamines – potent carcinogens (IARC Group 2A: probably carcinogenic to humans). Nitrosamines form when nitrites react with secondary amines (from protein breakdown) under acidic conditions (e.g., in the stomach or during frying of bacon). To mitigate this risk, food manufacturers add antioxidants (ascorbic acid/vitamin C, sodium erythorbate, α-tocopherol/vitamin E) that scavenge nitrosating species and convert nitrite to NO more efficiently, leaving less residual nitrite to form nitrosamines. Additionally, modern curing uses "ingoing nitrite" levels carefully balanced; "outgoing nitrite" (residual) must be reduced by processing. The ADI for nitrite (expressed as sodium nitrite) is 0.07 mg/kg bw/day (very strict). Potassium nitrite is toxic in high doses: the oral LD₅₀ in rats is about 200 mg/kg, and accidental ingestion (e.g., mistaken for salt) causes methemoglobinemia – a condition where nitrite oxidizes ferrous (Fe²⁺) hemoglobin to ferric (Fe³⁺) methemoglobin, which cannot carry oxygen, leading to cyanosis, headache, dizziness, and death at high methemoglobin levels (>70%). Despite these risks, the use of nitrite in cured meats remains essential because botulism from unpreserved meat is far more dangerous (mortality 5-10% despite modern intensive care). No alternative preservative matches nitrite's ability to inhibit C. botulinum spores while providing color and flavor. Consumer demand for "nitrite-free" products often results in replacement by celery juice powder (naturally high in nitrates), which is converted to nitrites by starter bacteria – yielding chemically identical nitrite residues. Thus, "uncured" or "nitrate/nitrite-free" label claims often mislead consumers. Potassium nitrite (E249) and sodium nitrite (E250) are the only nitrite salts permitted for food use; others (e.g., calcium nitrite) are not approved. The food industry uses potassium nitrite less widely than sodium nitrite (E250) due to higher cost and similar functionality unless sodium reduction is a priority.

SAFETY INFORMATION ABOUT POTASSIUM POTASSIUM NITRITE

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