Food Grade Sodium Metabisulfite: A Down-to-Earth Look
Historical Development
Food grade sodium metabisulfite grew from the broader history of food preservation. Long before chemical names filled our pantry labels, people did what they could to keep food from spoiling. Drying, salting, and fermentation were routine. Once chemists discovered that sulfur dioxide could fight off molds and bacteria, the search for stable, manageable compounds led to sodium metabisulfite. By the early 20th century, it wasn’t just chemists who knew about it; bakers, brewers, and winemakers worked with this white, powdery substance. It managed food safety before reliable refrigeration, and even now, it helps food stay safe during transport and storage.
Product Overview
Sodium metabisulfite, or Na2S2O5, goes by several names—SMBS, disodium disulfite, and E223 in Europe. In its food grade form, it meets strict purity standards governing the content of heavy metals and other impurities. While it comes off as a humble powder, it’s key in more foods than most realize, from dried fruit to dough conditioners. The bite of some wines or the vivid orange in dried apricots often owes its presence to this compound. People working with it know that only carefully produced SMBS makes the cut for food safety, and that’s something real-world kitchens and warehouses respect. Technical paperwork might get ignored, but those purity sheet details matter when customers expect both safety and shelf life.
Physical & Chemical Properties
Those who have handled sodium metabisulfite know that it doesn’t take much to spot it. It’s a white or slightly yellowish crystalline powder with a distinct, pungent sulfur smell that drifts out of any open container. Some might say it tingles the nose, especially in large amounts. It dissolves fast in water, forming a sour solution. Left in the open, it breaks down, absorbing moisture and releasing sulfur dioxide—too much of that and sensitive folks start coughing or notice a headache. This reactivity drives its ability to preserve food since it’s this same property that neutralizes unwanted microbes and disables browning enzymes in fruit and vegetables. Chemically speaking, it’s made of two sodium ions and a disulfite anion, with a molecular weight just under 190 grams per mole.
Technical Specifications & Labeling
On a food label, sodium metabisulfite usually hides under its E number (E223 in Europe), which reflects serious regulation. Any supplier aiming for food grade certification has to provide paperwork showing low levels of arsenic, lead, mercury, and other nasties. Purity must often exceed 96% for sodium metabisulfite, with chloride and thiosulfate content kept under strict limits. Real-life audits mean random spot checks and close attention to lot numbers, expiration dates, and the country of manufacture. Food manufacturers also care about mesh size since that controls how much dissolves or mixes with other powders—nobody wants gritty bits in a syrup or jam.
Preparation Method
Production of food grade sodium metabisulfite follows a pretty straightforward wet chemical process. Industry workers bubble sulfur dioxide gas through a cold, saturated solution of sodium carbonate (or sometimes sodium hydroxide, depending on plant setup). This leads to the formation of sodium bisulfite and then drives the reaction toward sodium metabisulfite as temperatures drop and water’s presence is managed. Crystallization from these solutions, followed by filtration and careful drying, yields the final powder. This drying, even if it sounds simple, sets food grade apart from some technical grades, as any leftover solvents or dust can make food unsafe. Workers sometimes test batch samples for color, odor, and reactivity before signing off on the shipment.
Chemical Reactions & Modifications
One of sodium metabisulfite’s main jobs happens as it dissolves in water, breaking down to produce sulfur dioxide and sodium bisulfite. This reaction is crucial in wine and juice industries, where it acts as both an antioxidant and anti-microbial. The sulfur dioxide binds to aldehydes, ketones, and other compounds, slowing spoilage and color change. In practical terms, this compound helps bakers bleach flour, prevents dough from sticking, and keeps potatoes from turning a nasty shade of brown before cooking. Some research investigates blending sodium metabisulfite with ascorbic acid or other salts to reduce allergen risk in finished foods. It also plays a bit of a villain in regulatory debates over labeling and disclosures, given that trace levels can spark allergic reactions.
Synonyms & Product Names
Look through warehouse bins or food ingredient invoices, and you might see several names printed for sodium metabisulfite. Alongside Na2S2O5, it could be “sodium pyrosulfite,” or just “sulfite powder.” European labels often say “E223”; in the United States, “sodium metabisulfite (food grade)” appears in accordance with the FDA’s food additive regulations (21 CFR 182.3766). Slight wording changes sometimes trip up procurement teams—so anyone ordering for a major food manufacturer learns to check the fine print for purity and country-of-origin claims instead of trusting only the cover sheet.
Safety & Operational Standards
Safe use of sodium metabisulfite in the food industry means controlling worker exposure and keeping tight control on ingredient dosing. It’s classified as a hazardous substance for storage and handling, so most plants set up exhaust systems and protective equipment—gloves, goggles, and good ventilation matter when scooping the powder for a production run. Some brands include stabilizers to cut down dust, but this only works up to a point. OSHA limits for airborne sulfur dioxide push companies to keep handling areas away from open production rooms. Better training for workers saves trouble in the long run, as overexposure can provoke skin, eye, and lung irritation. In food, strict legal limits (usually below 50–150 mg/kg depending on the product and region) reduce allergy risk. Restaurants and companies have to announce “contains sulfites” on menus and packaged foods, with clear language to protect sulfite-sensitive folks. Good Manufacturing Practices guide storage in dry, cool spaces, away from acids and moisture that could cause breakdown and release harmful gases in storage rooms.
Application Area
Anyone working with food knows sodium metabisulfite touches many sectors, including winemaking, dried fruits, jams, seafood, and even processed potatoes. In winemaking, a dash of this chemical steadies the fermentation process, guarding against rogue bacteria and helping the wine keep its taste and bouquet. Fishermen and seafood processors sometimes add a sprinkle to shrimp and lobster to keep them looking fresh by holding back the rusty black spots triggered by enzymes after harvest. In dried fruits, the sharp white powder locks in color and staves off spoilage. People preparing pre-peeled potatoes or shredded coconut often rely on sodium metabisulfite to dodge unsightly browning. Even breweries, bakers, and syrup producers look to this additive for flavor stability and long shelf life.
Research & Development
Ongoing research explores alternatives to conventional chemical preservatives, but sodium metabisulfite persists in part because it works so predictably. Labs worldwide examine how to limit its use without losing food safety or shelf life. Some teams investigate encapsulation or micro-dosing strategies, looking for ways to maintain benefits with much smaller quantities. Others target refining production to squeeze out impurities that could spark heavy metal contamination. In the world of allergen management, researchers study how “bound” versus “free” sulfites affect sensitive individuals and whether new testing can catch problematic residues not flagged under current protocols. Further out, green chemistry advocates work to redesign manufacturing, aiming to recycle byproducts and reduce energy input.
Toxicity Research
Toxicologists agree that, though sodium metabisulfite has kept food safe for decades, some people react poorly to even small amounts. Sulfite-sensitive individuals might break out in hives, have asthma attacks, or experience digestive issues. Because of this, most food regulations force disclosure for anything containing more than 10 ppm (parts per million) sulfite. High exposures, even brief, can irritate breathing passages in workers handling this chemical without protection, making workplace monitoring crucial. Studies across the world have looked for links to longer-term health effects; so far, evidence hasn’t shown clear risks for the general population when using approved doses. Still, research calls for continued caution, especially for people with asthma or who take certain medications that might make them more susceptible. Young children and the elderly often enter at higher risk, so nursing homes, schools, and hospitals use even stricter controls.
Future Prospects
Future directions center on reducing sodium metabisulfite reliance while guarding the benefits it brings to global food systems. Consumer demand for “clean label” products pushes manufacturers to balance shelf life with fewer chemical-sounding ingredients. Some producers run trials with alternatives such as ascorbic acid, plant extracts, or even high-pressure treatments, but cost and effectiveness don’t always match up. Innovations in packaging—films that limit oxygen, new storage designs—also play into the conversation. There’s a steady push for digital tracking from factory to final sale, making it easier to audit and recall affected batches when issues arise. As climate shifts and supply chains stretch further, stable, reliable preservation remains valued, but industry momentum leans into a future where sodium metabisulfite is used precisely, transparently, and only where its benefits can’t be replaced by safer or simpler options.
The Role of Sodium Metabisulfite in Food
Walk into the back room of any real bakery or a commercial kitchen, and you’ll find all sorts of curious powders. Sodium metabisulfite sits near the top of the list, thanks to its importance in preserving food. Years back, working at a neighborhood produce stand, I saw just how often this white granular powder appeared when fruit shipments came in, especially grapes or dried apricots that needed to look fresh for days out on the shelves. The use case is straightforward: sodium metabisulfite holds back spoilage and keeps food looking good and tasting right, especially during long trips from field to store.
How It Helps Preserve Food
Food manufacturers and small shops alike count on sodium metabisulfite to stop unwanted browning and spoilage in fruits and vegetables. Nobody wants to pay for a dried apple that tastes like cardboard or turns brown before lunchtime. Sulfites block the enzymes responsible for discoloration and fight off certain bacteria, meaning products last longer and waste gets cut down. Research out of food safety groups shows that treated dried fruit maintains color and palatability far better.
Bread and Dough Processing
Bread makers favor sodium metabisulfite for another reason: it softens and strengthens dough. Bakers add just enough to break down gluten bonds without turning the final loaf chewy or tough. This trick makes large-scale production of soft, packaged bread possible. As a former kitchen manager, I noticed that skipping it often meant uneven results from batch to batch, especially when humidity changed. Some Asian noodles owe their signature chewiness and stretch to a touch of the same compound in the dough mix. Labs have measured significant improvements in workability and texture for both bakery and noodle applications.
Winemaking and Beverage Uses
Winemakers swear by sodium metabisulfite. In the old days in rural areas, friends who made small-batch wine explained that adding it suppresses wild yeast and bacteria, letting their chosen yeasts do a cleaner job during fermentation. At bottling, it acts as a powerful antioxidant so that homemade wine, cider, or juice can hit the table six months later still tasting fresh. Commercial wineries go one step further with closely monitored doses, tying every addition to chemical analysis. The science backs up this approach, as sulfite levels directly affect flavor, shelf life, and safety.
Safety and Sensitivity
Despite widespread use, sodium metabisulfite isn’t without its controversies. Some people, especially those with asthma or certain allergies, react badly to sulfites in food. In the eighties, regulations stepped in to require labels on products containing more than a trace. Today, shoppers can spot “contains sulfites” on bags of dried fruit, wine bottles, or even some frozen seafood. The facts show that, for most people, these levels are safe; regulatory agencies around the world set strict limits and continually review health data. In kitchens I’ve run, staff wore gloves and worked in well-ventilated prep areas to avoid direct contact or inhalation of the powder.
How to Reduce Reliance on Additives
People now push for fewer additives in their food, and that includes sodium metabisulfite. Shoppers look for unsulfured fruit or natural fermentation processes, turning to refrigeration, quick-freezing, or vacuum-packing as other ways to keep food quality up. Producers invest in cold chain logistics or test alternative natural preservatives. Over the years, I’ve seen folks pay a bit more for food made with fewer chemicals—proof that the way forward won’t be about total elimination, just smarter and safer handling paired with clear information for buyers.
What Is Food Grade Sodium Metabisulfite?
Food grade sodium metabisulfite looks like a white, powdery substance. You’ll find it in packaged foods, dried fruits, and even some wines. Food processors turn to it because it works really well as a preservative, stopping bacteria or mold before they start causing trouble. It even helps keep foods looking fresh longer, especially things like shrimp or potato products that turn brown after peeling. In my time working in a local market, I’ve seen plenty of canned and dried foods that rely on some preservative to stretch their shelf life, and sodium metabisulfite is a regular face in this lineup.
What Scientists and Regulators Say
The big question people bring up is about safety. Authorities like the U.S. Food and Drug Administration, the European Food Safety Authority, and regulators in Canada have all reviewed its use. They say that when used in the right amounts set by law, sodium metabisulfite doesn’t threaten healthy people. Maximum limits exist: in the United States, manufacturers are allowed no more than 3,000 parts per million in dried fruit and lower amounts in things like wine or shrimp. Labels must list it if the concentration goes above 10 parts per million. This helps shoppers with sensitivities or allergies steer clear.
Who Faces Greater Risks?
For most people out there, the typical preservative level in store-bought foods won’t set off problems. There’s a big exception for anyone with asthma or sulfite sensitivity. Some people notice wheezing, hives, or other allergic reactions even at really low amounts. The FDA points to roughly one out of every 100 people with asthma who could react to sulfites. I’ve seen cases at a family gathering where a cousin, who never had issues before, suddenly broke out in hives after eating takeout that used a lot of preservatives. It left an impression: always check the packaging, especially if you have a known sensitivity.
Facts Behind the Fears
Misinformation about food chemicals spreads easily nowadays. Some folks read the word “sulfite” and get nervous, thinking it’s a harsh industrial chemical. In reality, the body breaks down small amounts without trouble. Scientific studies show that sodium metabisulfite clears from the body fairly quickly, mostly in urine. There’s no evidence linking food-grade use to long-term health damage in healthy adults. Overshooting the safe daily intake (which is higher than a person would get from a typical diet) is unlikely unless someone’s eating enormous amounts of preserved foods every day.
Balancing Safety and Food Security
Without preservatives like this, food spoilage would waste more groceries and wallets would feel it. Stretched budgets benefit from shelf-stable foods that remain safe long enough to use up, meaning less of what’s bought ends up in the trash. Sodium metabisulfite plays a quiet but important role in this, especially for dried fruit, seafood, and ready-made dishes.
A Smarter Approach
For anyone wanting to avoid it, learning to read ingredients lists helps. Choosing fresh or unprocessed foods cuts out most artificial additives. Those with asthma or allergies can take extra care. Policy makers and food producers could look for newer preservatives that don’t cause adverse reactions. Ongoing research around natural alternatives might one day make synthetic preservatives less common.
Choosing What’s Right for You
Personal experience and expert guidance both show that moderate amounts of food grade sodium metabisulfite won't harm most people. Staying informed, checking labels, and making choices based on your family’s needs make a bigger difference than worrying over every chemical name. Food safety rests on good practices, smart decisions, and honest information you can trust.
No Room for Carelessness with Food Ingredients
Food grade sodium metabisulfite isn’t some random powder you can toss onto any shelf and forget. Most people hear "preservative" and picture a product that never fails, yet that’s not the truth here. If you open a new drum or sack and scoop out of it daily, a little moisture in the air won’t just make the powder clump. It starts to lose the punch you paid for, and nobody wants surprise off-notes in fruit packs or a failed batch of wine. Shrugging off the small stuff, like where and how you stash this chemical, often comes back to haunt kitchens and factories alike.
Humidity and Air Mean Trouble
Sodium metabisulfite draws water from air—quickly. I once stored a bag in a humid storeroom for just a week in the summer, and it was a brick when I came back. Moisture doesn’t just turn powder into lumps. The chemical reacts with water, releases sulfur dioxide, and loses power. Once that happens, folks need to use more for the same effect. Nobody wants to slip into unsafe territory just to hit required preservation levels. It only takes a bit of carelessness to risk ruined batches or even food safety.
The Role of Containers
Many manufacturers sell high-grade polyethylene drum or multi-layer paper sacks with tight seals. You’ve got to seal those up immediately after scooping - rolling the top closed, double-tying, or closing the drum’s lock ring. It’s always tempting to leave a scoop sitting inside, waiting. That looks convenient until you realize it introduces more air and moisture every day. Some places keep silica gel packets with the drum or bag just as extra insurance. This isn’t overkill; it’s the type of habit that saves money and headaches long term. My own experience with small bakeries taught me: one careless open sack turned into days of cleaning and lost product.
Keep It Dry, Cool, and Dark
Sunlight speeds up chemical changes nobody wants in this powder. Store it in a shaded portion of your storeroom, away from any windows or direct lighting. If you leave it under bright fluorescents or forget it by a sunny doorway, expect trouble. Cooler temperatures slow down those unwanted reactions, too. Heat and humidity tag-team and ruin product faster than most people imagine. Walk into a storeroom after a wash-down, and you’ll smell the sulfur if humidity stayed up overnight. It’s an easy fix: use dehumidifiers or stick the container in a climate-controlled space if your climate swings fast. Warehouses sometimes use metal cabinets with locking doors to cut the risk of accidental spills or exposure to sunlight.
For Safety and Staff Training
Food safety officers and warehouse workers both play key roles. They need reminders and training. It isn’t enough to slap on a “Keep Dry” sticker. Clear instructions posted above the storage shelves in every language used by staff show that you really value quality. I’ve seen too many storerooms where nobody knows why a rule exists, and cutting corners costs plenty.
Proper storage is more than a checklist for compliance. Flavor, shelf life, safety, and cost all hinge on a simple decision: treat sodium metabisulfite right and keep it protected. It’s a straightforward step with a big payoff in any food operation.
The Role of Sodium Metabisulfite in Food
Sodium metabisulfite shows up in many areas of food processing because it keeps things fresh longer, holds off spoilage, and helps colors stay bright. Bakers use it to keep dough stretching just right. Potato processors turn to it so sliced potatoes don’t go brown before they hit the fryer. Anyone making dried fruits likely knows it stops the fruit from turning an unappealing shade and helps stop mold from gaining ground. Sulfites like this one have been essential in the industry, but too much brings trouble for some consumers, and food safety agencies keep a close eye on its use.
How Much to Use?
Serving up safe food starts with sticking to strict limits. The Food and Drug Administration (FDA) and European Food Safety Authority (EFSA) both land on a similar level: no more than 0.7 grams per kilogram of food (that’s 700 parts per million, or ppm). The Joint FAO/WHO Expert Committee on Food Additives, which includes scientists and health experts, pins their acceptable daily intake at 0.7 mg per kilogram of body weight each day. For a person weighing 70 kilos—about 154 pounds—that’s 49 mg a day at most from all food sources combined.
Bakers might use about 30–70 ppm in crusty bread to keep dough in good shape and get consistent texture. Winemakers often add around 100–200 ppm during fermentation to shield wine from wild microbes and oxidation, but table grapes and dried fruits sit closer to 50–100 ppm. Potato processors usually hover below that mark, as high amounts can affect taste. Regulatory agencies check that food labeled as “sulfite-free” contains less than 10 ppm.
Why Getting the Dosage Right Matters
Some folks are sensitive to sulfites. Asthma sufferers are particularly at risk, and even a little sulfite in a meal can cause trouble breathing, swelling, or worse. Most people handle low amounts, but a careless hand in the mixing room raises real health concerns. Consumers expect safety, and repeated fines or recalls cause damage most food businesses never recover from. Once you lose trust, it rarely comes back. From a personal viewpoint, I’d much rather see a food company stay conservative with its additives. My own family includes two people with asthma, and restaurant meals have sent us rushing for an inhaler more than once. The label often didn’t say a thing about sulfites, either.
Safer Practices and Alternatives
The best way to keep the public safe is by weighing every batch and double-checking every calculation. Software helps now, but even high-tech setups rely on careful workers and real training. Consider also the rise of alternative preservatives. Ascorbic acid gets similar results in some cases, although it costs more. Modified atmosphere packaging slows spoilage without needing preservatives at all. Many food processors look for ways to reduce sulfite levels and lower the risk to allergy-prone customers. That kind of thinking not only keeps people healthier but also lets brands market themselves honestly. The more transparency and responsibility in the process, the better for businesses and eaters alike.
Food Additives: Not Always as Harmless as They Seem
Supermarkets offer foods that last far longer on shelves thanks to additives. Sodium metabisulfite is one of those workhorses, used in dried fruit, wine, potatoes, and even some seafood. It shows up in the list of ingredients far more often than most people realize. Many trust these products without thinking much about what’s inside. Once you dig in, though, concerns about allergies and side effects become a bit harder to ignore.
Sulfites: Sneaky Trouble for Some People
This compound belongs to the group called sulfites. Sulfites show up on allergen warnings because they trigger problems for a chunk of the population. Most people never notice any reaction and keep munching away. For some, especially those with asthma, sulfites can kick off symptoms ranging from mild itchiness to life-threatening breathing trouble. That hit home for me as a food service worker years ago. Watching a coworker react to dried apricots was a wake-up call; he wheezed and struggled to catch his breath after a handful. He knew about his asthma but never checked the label for sulfites.
The FDA recognizes sulfites as allergens. Current food labeling rules in the US require manufacturers to list sulfites on packages if they are present above 10 parts per million. Food writers and dietitians warn that anyone who knows they suffer from sulfite sensitivity has to keep alert. Accidentally eating sulfite-laden foods can ruin a meal or become much more severe.
Side Effects: Sometimes Subtle, Sometimes Serious
Sodium metabisulfite sometimes brings side effects that catch consumers off guard. Some people notice symptoms even if they don’t have allergies. These can include headaches, hives, gastrointestinal discomfort, or occasionally low blood pressure. My own experience walking through vineyards during grape harvest hammered that point home. The whiff of sulfur from freshly treated barrels left me with a headache and some mild nausea, even though I don’t react in a dangerous way.
Children seem a bit more likely to get flushed, or develop rashes after eating foods high in sulfites. Doctors sometimes diagnose migraines traced back to this preservative. For most people, these effects fade quickly once the additive leaves their system. People who already deal with asthma, eczema, or hay fever notice more trouble than others.
Safe Use and Handling Solutions
Everyone wants to enjoy processed foods without fear. For those sensitive to sodium metabisulfite, label reading can make a huge difference. Many stores now offer sulfite-free raisins, wines, and snacks for this very reason. If you find out you have a sulfite allergy, sharing information with friends, teachers, and restaurants can help avoid surprise reactions.
Regulators keep pushing for clearer packaging. Groups like the Asthma and Allergy Foundation of America advocate for education campaigns so people can learn to recognize sulfite-laced foods. More food producers are switching to alternatives like ascorbic acid, though these substitutes change the taste and texture of products.
If sulfites regularly cause headaches or stomach upset, a medical checkup can reveal exactly which food ingredients to watch. Living with allergies doesn’t mean skipping your favorite foods forever. Asking questions, reading labels, and supporting clear food safety rules will always help keep those with sensitivities healthier—and a lot happier at the dinner table.
| Names | |
| Preferred IUPAC name | sodium metabisulfite |
| Other names |
Sodium pyrosulfite
Disodium metabisulfite Sodium disulfite Pyrosulfurous acid, disodium salt |
| Pronunciation | /ˈsəʊdiəm ˌmɛtəˈbɪsəlfaɪt/ |
| Preferred IUPAC name | sodium pyrosulfite |
| Other names |
Sodium pyrosulfite
Disodium disulfite SMBS E223 Metabisulphite Disodium metabisulfite |
| Pronunciation | /ˈsəʊdiəm ˌmɛt.əˈbʌɪsəlfaɪt/ |
| Identifiers | |
| CAS Number | 7681-57-4 |
| Beilstein Reference | 3554986 |
| ChEBI | CHEBI:38101 |
| ChEMBL | CHEMBL1359 |
| ChemSpider | 5410857 |
| DrugBank | DB14527 |
| ECHA InfoCard | '03b2eaf7-18a6-4dc6-a78b-74e8fa6c7790' |
| EC Number | 231-673-0 |
| Gmelin Reference | 72467 |
| KEGG | C19582 |
| MeSH | D017358 |
| PubChem CID | 24541 |
| RTECS number | UX8225000 |
| UNII | 6U8STK432W |
| UN number | UN 3077 |
| CAS Number | 7681-57-4 |
| Beilstein Reference | 13372 |
| ChEBI | CHEBI:62711 |
| ChEMBL | CHEMBL1359 |
| ChemSpider | 5793 |
| DrugBank | DB14526 |
| ECHA InfoCard | 03b870d7-b439-4a17-9c03-cfd7e22fcb2a |
| EC Number | 231-673-0 |
| Gmelin Reference | 774786 |
| KEGG | C01452 |
| MeSH | D014477 |
| PubChem CID | 24846 |
| RTECS number | VP2310000 |
| UNII | 6QJ6IOC928 |
| UN number | UN 3077 |
| Properties | |
| Chemical formula | Na2S2O5 |
| Molar mass | 222.33 g/mol |
| Appearance | White or slightly yellowish crystalline powder |
| Odor | Slight sulfur dioxide odor |
| Density | 1.48 g/cm³ |
| Solubility in water | Soluble in water |
| log P | -3.7 |
| Acidity (pKa) | pKa1 = 1.96, pKa2 = 7.2 |
| Basicity (pKb) | pKb: 6.6 |
| Magnetic susceptibility (χ) | Diamagnetic |
| Refractive index (nD) | 1.48 (at 20°C) |
| Dipole moment | 6.17 D |
| Chemical formula | Na2S2O5 |
| Molar mass | 190.10 g/mol |
| Appearance | White or slightly yellow crystalline powder |
| Odor | Slight sulfur odor |
| Density | 1.48 g/cm³ |
| Solubility in water | Very soluble in water |
| log P | -3.7 |
| Acidity (pKa) | 7.0 |
| Basicity (pKb) | 7.0 |
| Magnetic susceptibility (χ) | Diamagnetic |
| Refractive index (nD) | 1.45 (20°C) |
| Dipole moment | 0 D |
| Thermochemistry | |
| Std molar entropy (S⦵298) | 172 J·mol⁻¹·K⁻¹ |
| Std enthalpy of formation (ΔfH⦵298) | –941 kJ/mol |
| Std enthalpy of combustion (ΔcH⦵298) | -947 kJ/mol |
| Std molar entropy (S⦵298) | 125.5 J/(mol·K) |
| Std enthalpy of formation (ΔfH⦵298) | -944 kJ/mol |
| Pharmacology | |
| ATC code | V03AB18 |
| ATC code | V03AB17 |
| Hazards | |
| Main hazards | Harmful if swallowed, causes skin and serious eye irritation, may cause respiratory irritation. |
| GHS labelling | GHS07, GHS05 |
| Pictograms | GHS05,GHS07 |
| Signal word | Warning |
| Hazard statements | Hazard statements: Harmful if swallowed. Causes serious eye damage. May cause respiratory irritation. |
| Precautionary statements | P264, P270, P271, P301+P312, P330, P304+P340, P305+P351+P338, P312, P342+P311, P403+P233, P501 |
| NFPA 704 (fire diamond) | 1-1-1-W |
| Lethal dose or concentration | LD50 (oral, rat): 1132 mg/kg |
| LD50 (median dose) | LD50 (oral, rat): 1132 mg/kg |
| NIOSH | RWG4750000 |
| PEL (Permissible) | PEL: 5 mg/m³ |
| REL (Recommended) | 5 mg/m³ |
| IDLH (Immediate danger) | 530 mg/m³ |
| Main hazards | Harmful if swallowed, causes serious eye damage, may cause respiratory irritation. |
| GHS labelling | GHS07, Warning, H302, H319, P264, P270, P305+P351+P338, P337+P313 |
| Pictograms | GHS07,GHS09 |
| Signal word | Warning |
| Hazard statements | Hazard statements: Harmful if swallowed. Causes serious eye irritation. May cause respiratory irritation. |
| Precautionary statements | P264, P270, P271, P301+P330+P331, P304+P340, P305+P351+P338, P312, P342+P311, P403+P233, P501 |
| NFPA 704 (fire diamond) | 2-0-1 |
| Lethal dose or concentration | LD50 (oral, rat): 2,480 mg/kg |
| LD50 (median dose) | 1132 mg/kg (rat, oral) |
| NIOSH | WS5600000 |
| PEL (Permissible) | PEL: 5 mg/m³ (as SO₂) |
| REL (Recommended) | 5 mg/m³ |
| IDLH (Immediate danger) | Not established |
| Related compounds | |
| Related compounds |
Sodium bisulfite
Sodium sulfite Sodium thiosulfate Potassium metabisulfite Potassium bisulfite |
| Related compounds |
Sodium bisulfite
Sodium sulfite Potassium metabisulfite Sulfur dioxide Sodium thiosulfate |
