PRODUCTS

E224 (Potassium Metabisulfite)

Chemical Identifiers
Linear Formula K2S2O5
MDL Number: MFCD00167605
EC No.: 240-795-3
Pubchem CID: 28019
IUPAC Name: N/A
SMILES [K+].[K+].[O-]S(=O)S([O-])(=O)=O
InchI Identifier: InChI=1S/2K.H2O5S2/c;;1-6(2)7(3,4)5/h;;(H,1,2)(H,3,4,5)/q2*+1;/p-2
InchI Key: RWPGFSMJFRPDDP-UHFFFAOYSA-L

K2S2O5 = 222.33
Assay 95% min
SO2 content 28.8% min
Chloride (Cl) 0.1% max
Lead (Pb) 0.001% max
Iron (Fe) 0.001% max
Sodium (Na) 1% max

E224 (Potassium Metabisulfite) (K2S2O5), commonly abbreviated KMS, is a powdery, white, strongly sulfurous-smelling (burned match) chemical used in many food and beverage industries, as well as in breweries as an antioxidant.
When dissolved in water or beer, KMS releases free sulfite ions, and these are responsible for the antioxidative properties of the compound.
KMS is by far the most popular antioxidant used in the brewing industry.
Its popularity within some large breweries is because it is highly effective at preventing oxidation and because the added sulfites improve the naturally occurring sulfites produced by the yeast during fermentation.
KMS is also active in limiting growth of wild yeasts and bacteria in beer.
Free sulfite reacts very readily with and thus eliminates free oxygen in foods (including beer), but also with many intermediary chemicals compounds (most important, aldehydes and ketones) that can combine with free oxygen into the stale and papery-tasting compounds so undesirable in beer.
KMS is allowed by Food Health and Safety authorities in most countries around the world, but it is not permitted by Germany’s Reinheitsgebot.
KMS is rarely used by craft brewers anywhere, but it is common in mass-market beers in many countries.
In most countries the use of KMS is regulated by specific limits either to the total concentration of sulfites in beer or by maximum allowed dosing rates.
The reason for these limitations is that sulfites are known to provoke and worsen certain allergies in humans.
For example, in the United States, levels above 10 ppm will require the words “contains sulfites” to be printed on the label.

Potassium metabisulfite appears as a white granular or powdery solid with a sharp odor of sulfur dioxide.
Decomposes at 150 to 190°C. Density 2.3 g / cm3. Contact severely irritates skin, eyes, and mucous membranes.
Low toxicity.
Used as a food preservative and an antioxidant.

What is potassium metabisulfite?
Potassium metabisulfite, also known as the food additive E224 or potassium pyrosulfate, is a food preservative which preserves the natural colour of food and protect against bacteria.
The additive is produced from potassium hydroxide (KOH) or potassium carbonate (K2CO3), both potassium derivatives manufactured by Vynova.
KOH and K2CO3 find their origin in an electrochemical process involving potassium chloride (KCl), a salt that naturally occurs in the earth’s crust and is widely used in the feed and fertilizer industry.
While it is sometimes used interchangeably with sodium metabisulfite, potassium metabisulfite is usually preferred for different reasons.
Firstly, potassium occurs naturally in the human body, in nature and is key for growth and life. Secondly, the use of potassium metabisulfite in food products enables a strong reduction of their sodium content.
In addition, the substance is easily assimilated by the human body.

Uses
It is used as a food additive, also known as E224.
It is restricted in use and may cause allergic reactions in some sensitive persons.
As antifermentative in breweries and wineries.
Preservative for fruits and vegetables.
Bleaching straw.

Wine
Potassium metabisulfite is a common wine or must additive, in which it forms sulfur dioxide (SO2).
Sulfur dioxide is a disinfectant.
It also acts as a potent antioxidant, protecting both the color and delicate flavors of wine.

A high dose would be 3 grams of potassium metabisulfite per six-gallon bucket of must prior to fermentation; then 6 grams per six-gallon bucket at bottling.
Some countries regulate the SO2 content of wines.
Winemaking equipment is sanitized by spraying with a 1% SO2 solution.

Beer
Potassium metabisulfite is sometimes used in the brewing industry to inhibit the growth of wild bacteria and fungi.
This step is called 'stabilizing'.
It is also used to neutralize monochloramine from tap water.
It is used both by homebrewers and commercial brewers alike.
It is not used as much for brewing beer, because the wort is almost always boiled, which kills most microorganisms.

Other uses
Potassium metabisulfite is sometimes added to lemon juice as a preservative.
Potassium metabisulfite is used in the textile industry for dyeing and cotton printing.
Potassium metabisulfite is sometimes used to precipitate gold from solution in aqua regia (as an alternative to sodium sulfite).
It is a component of certain photographic developers and solutions used in photographic fixing.
It is used as a bleaching agent in the production of coconut cream.
It is used in some pickles as a preservative.
It is used in tint etching iron-based metal samples for microstructural analysis.
It is used in Aam papad as a preservative.

Safety
Potassium metabisulfite can irritate skin, eyes, and respiratory tract.

Potassium metabisulfite is a food preservative, which preserves the natural color of food and protects food against bacteria.
Winemakers also use potassium metabisulphite to preserve bottled wines.
The manufacturing industry uses potassium metabisulphite as a dye and printing agent, in gold processing and in photography for developing.

E224 (Potassium Metabisulfite)
Potassium metabisulfite is a white crystalline powder that has a strong sulfur odor.
Additionally, potassium metabisulfite is a disulfite and has a melting point of 374 degrees Fahrenheit.
Some potential dangers associated with exposure to this substance include severe burning and damage to your eyes, irritation and reddening of your skin and difficulty breathing.
If exposed to the raw, unprocessed form of potassium metabisulfite, you should immediately seek medical attention.
Flush your eyes with water for 15 minutes and use water to remove any of the substance from your skin.

Wine
The winemaking industry uses potassium metabisulfite as an additive during the bottling process.
When they add potassium metabisulfite to the wine, a sulfur dioxide gas forms, which destroys microorganisms in the wine and prevents molds and bacteria from growing inside the wine bottle.
Additionally, potassium metabisulphite is a strong antioxidant that protects the color and flavors of the wine.
Without the use of potassium metabisulfite, wines would develop a stronger taste over time as the wine ages in the bottle.
One quarter teaspoon of potassium metabisulphite can treat approximately five gallons of wine.

Other Uses
In the food industry, manufacturers use potassium metabisulphite to preserve the taste of dehydrated foods and to make these foods more palatable.
Potassium metabisulphite cannot preserve certain kinds of foods, including raw fruits, vegetables and meats.
However, the substance can preserve fruits as part of the canning or dehydration process.

Caution
Potassium metabisulphite is an allergen for some individuals.
If you have allergies to other food preservatives, you may also have or develop an allergy to potassium metabisulphite.
If you experience difficulty breathing, swelling of your extremities, difficulty swallowing or a rash or welts on your skin after consuming potassium metabisulphite, you should immediately stop consuming all products that contain this substance and seek medical attention.

MAIN USES
Reducing and sulfonating agent
This product is used as a sulfonating agent and a reducing agent in chemical process with significant applications for surfactants and polymerization.
It is a white granular product that is readily soluble in water.

Component in developing baths and stabilizing agent for fixers
This product is used as an essential component of developer baths (preserves developing agents from rapid oxidation) and fixers (stabilizes the thiosulfate ion) in the photographic industry.
It is a white granular product that is readily soluble in water.

Food additive and preservative
This product is used as an additive, preservative, antioxidant and anti-microbic agent in the food anf beverage industries.
It is a white granular product that is readily soluble in water.

Description
E224 (Potassium Metabisulfite), (often referred to as "SO2", "sulfites" "meta", or "meta-bi") has several uses in winemaking.
At the crush, sulfites are generally used to help control the spoilage bacteria and indigenous yeast that may already be present both on the fruit and in the winery (i.e. on the picking bins, processing equipment, tanks, tubing, etc).
the amount generally used is enough to inhibit most of the unwanted organisms but not enough to hinder a cultured yeast, which has a higher tolerance to sulfites than most of the indigenous organisms do.
This inhibition effectively "wipes the slate clean" for the cultured yeast to step in and rapidly colonize the must so that it can effectively dominate the subsequent fermentation.
In addition, sulfites also help to inhibit the enzymatic browning of both musts and finished wines so that all of their delicate complexities can be preserved.
Later, during storage and in the bottle, sulfites at the proper levels will further protect a wine by continuing to inhibit spoilage organisms, as well as by scavenging oxygen.
Note that the exact amount needed to effectively do the job is determined by the pH of the wine.
In addition, it's important to keep in mind that free SO2 levels fall faster in wood cooperage than in glass or stainless, so if you are using a barrel you will most likely need to manage sulfite levels more closely.

The most common form of Metabisulfite is as a powder which is fixed with potassium or sodium.
1/4 tsp of E224 (Potassium Metabisulfite) adds 50ppm to 5 gallons of must.
Old Metabisulfite loses potency with time and should be replaced every year to assure that you are getting correct levels.
You can use old Metabisulfite to make solutions for sanitizing equipment.

Potassium metabisulfite in wine
In wine making, potassium metabisulfite acts as an antioxidant, removing all the oxygen suspended in the wine, which slows down aging. Natural cork closures enable micro-oxygenation by allowing tiny amounts of oxygen back into the wine so flavours can reach their potential.
In addition to preventing flavours from deteriorating, potassium metabisulfite made from Vynova potassium hydroxide (KOH) or potassium carbonate (K2CO3), preserves the colour of the wine, preventing white wines from turning golden brown or red wines from turning orange and then brown.

How much potassium metabisulfite do you need?
It can be complicated to work out how much potassium metabisulfite to add to your wine.
On the one hand, it needs to be enough to inhibit most of the unwanted bacteria, while on the other hand the amount shouldn’t hinder the cultured yeast needed for fermentation.
Plus, some countries have restrictions on how much sulphur dioxide (SO2) wines are allowed to contain, which further complicates calculations.
Furthermore, you should only add a small amount to start as it is not easy to remove potassium metabisulfite after it has been added. In fact, if you add too much, there is no chemical way to solve this issue, the only remedy is to give it time to dissipate.

Other uses of potassium metabisulfite
Potassium metabisulfite made from Vynova potassium derivatives has many uses across the food, textile, metal and film industries.
Some of these uses include:
Preserving lemon juice and pickles;
Preserving fruits as part of the canning or dehydration process;
Preserving the taste of dehydrated foods to make them more palatable;
Bleaching agent in coconut cream;
Stabilising in the brewing industry to inhibit the growth of wild bacteria and fungi;
Neutralising monochloramine from tap water;
Dyeing and printing for textiles;
Precipitating gold from solution in aqua regia (as an alternative to sodium sulfite);
Developing solutions for photographs.

POTASSIUM METABISULFITE Properties
Melting point:190°C
Density 2.34 g/cm3
vapor density 2.3 (vs air)
storage temp. Store at +5°C to +30°C.
solubility H2O: 0.1 M at 20 °C, clear, colorless
form Powder/Solid
color White to slightly yellow
Specific Gravity2.3
OdorOdorless
PH2.5-4.5 (25℃, 0.1M in H2O)
PH Range3-4.5 at 22.2 g/l at 25 °C
Water Solubility Soluble in water.
Insoluble in ethanol.
λmax267nm(H2O)(lit.)
Sensitive Air Sensitive
Decomposition 150°C
Merck 14,7645

Chemical and Physical Properties
Property Name    Property Value
Molecular Weight    222.33
Hydrogen Bond Donor Count    0
Hydrogen Bond Acceptor Count    6
Rotatable Bond Count    0
Exact Mass    221.8461284
Monoisotopic Mass    221.8461284
Topological Polar Surface Area    125 Å²
Heavy Atom Count    9
Formal Charge    0
Complexity    136
Isotope Atom Count    0
Defined Atom Stereocenter Count    0
Undefined Atom Stereocenter Count    0
Defined Bond Stereocenter Count    0
Undefined Bond Stereocenter Count    0
Covalently-Bonded Unit Count    3
Compound Is Canonicalized    Yes

Product Description
Uses
Potassium Metabisulphite (AKA sulphite) is a white crystalline powder which mixes with water to form a sanitizing solution.
It is the most widely used sanitizer in home-winemaking.
Sulfites have been utilized in winemaking for hundreds of years.
Sulphites also act as a preservative to prevent oxidation in wine.

Directions:
For Sulphite additions in wine:
Dissolve 3 grams (1/2 tsp) per 23 L of wine to give 50 ppm. Dissolve in a small amount of cold water.
Stir into wine thoroughly.
Seal tightly when not in use.

Molecular Formula : K2S2O5
Molecular Weight : 222.31
Part A
Storage : Room Temperature
Shelf Life : 60 Months
HSN Code : 28322010
IMDG Identification :Not Regulated for Transport (Non-Haz)

Product Description
E224 (Potassium Metabisulfite) is a common additive used to preserve and stabilize wines, ciders, and occasionally beers.
When added to wine or must, it forms sulfur dioxide gas (SO2).
This prevents most wild microorganisms from growing and acts as a potent antioxidant, protecting both the color and delicate flavors of wine.
E224 (Potassium Metabisulfite) solutions are also used as sanitizing rinses for winemaking equipment.
Recommended Usage
Dosage varies when used to kill wild bacteria in must, halt fermentation, or preserve finished wines against oxidation.
The addition of 1/4 teaspoon of potassium metabisulfite to 5 gallons contributes approximately 50 ppm of free SO2.
To make a sanitizing rinse for equipment, dissolve 8 teaspoons of potassium metabisulfite into 1 gallon of water.
High concentrations of sulfur dioxide gas are irritating and toxic, so use in a well ventilated area.
After applying the solution to your equipment, the items must be rinsed with clean, cold water.

MSDS
Product Datasheet
Stock Check & Taxation Details
Enter Batch No. for COA

Specifications
Appearance (Colour)    White
Appearance (Form)    Crystalline powder
Solubility (Turbidity) 10% aq. solution    Clear
Solubility (Colour) 10% aq. solution    Colourless
Assay    min. 95%
Chloride (CI)    max. 0.1%

Physical Properties:
Appearance:    colorless crystalline powder (est)
Assay:    90.00 to 100.00
Food Chemicals Codex Listed:    No
Soluble in:
water, 1e+006 mg/L @ 25 °C (est)
Insoluble in:
alcohol

Description
Potassium metabisulphite is a popular antioxidant for preserving the quality of wine and obtaining a good quality end product with excellent organoleptic characteristics.
Offered by Polsinelli Enologia in 100g packs, potassium metabisulphite for wine can be dissolved in cold water and then added to the liquid to be stabilised by stirring.
The reaction of metabisulphite with the wine prevents the oxygen in the liquid from reacting with polyphenols, ethanol and aromatic molecules, thus preserving the characteristics of the wine.
Potassium metabisulphite in a 100g package is a white powder with a pungent odour.
Please refer to current legislation for the maximum amount of stabiliser that can be used in wine.

Characteristics of potassium metabisulphite for wine
Product for professional use
Pack of 100 grams
Potassium metabisulphite, also known as potassium pyrosulfite, is a white crystalline powder with a pungent sulfur odour.
The main use for the chemical is as an antioxidant or chemical sterilant.
It is a disulphite and is chemically very similar to sodium metabisulphite, with which it is sometimes used interchangeably.
Potassium metabisulphite is generally preferred out of the two as it does not contribute sodium to the diet.
potassium metabisulphite is a common wine or must additive, in which it forms sulfur dioxide gas (SO2).
This both prevents most wild microorganisms from growing, and it acts as a potent antioxidant, protecting both the colour and delicate flavours of wine.
The typical dosage is 1/4 tsp potassium metabisulphite per 5 gallons of must prior to fermentation; then 1/2 tsp per five-gallon bucket (150 ppm of SO2) at bottling.
Most commercial wineries do not add more than 30ppm at bottling.
Winemaking equipment is sanitized by spraying with a 1% SO2 solution
When dissolved in water this releases sulphur dioxide which has many important properties in wine and beer making:-
It has antiseptic qualities which will stun, if not kill, the bacteria and wild yeasts in or on fruit.
It has antioxidant qualities which help prevent the effects of oxidation in beer, cider or wine.
It destroys the enzyme that causes enzymatic browning in juice, similar to what happens to an apple if it is sliced and exposed to the air.
Without sulphite in some form much wine would be brown or amber in colour, smell oxidized (or have a sherry-like aroma), and would probably be ruined by bacterial spoilage.
Beer makers will also appreciate that sulphite also removes chlorine from water and therefore reduces the chance of beer being tainted with TCP flavours.

Sulphur has been used in winemaking for many centuries.
In fact, from the Middle Ages until well into this century, barrels for storing wine were disinfected by burning a sulphur stick inside them.
Today more controllable methods are used, but the end result is the same; and despite concerns about the use of “sulphite”, it is unlikely that we will see the elimination of sulphur from winemaking anytime soon.
The reason is that no other method offers the range of desirable effects that sulphur provides, with its convenience of use, measurability, and low cost.
It is an antioxidant, preserving the fresh flavour of the wine and preventing browning.
It is a sterilant; and what is more interesting about this is that its effects are far more pronounced with wild yeasts and bacteria than it is with cultured wine yeasts, which have a fair tolerance for it.
In other words, it’s selective in its actions and favours the organisms that we wish to favour.
By inhibiting new budding of the yeast it enhances clearing of the wine.
Potassium Metabisulphite, especially for people making a reasonable quantity of wine is probably the most convenient and favoured form of sulphite.
Sodium Metabisulphite has fallen into disfavour, in part because it leaves Sodium in the wine, a concern for people with high blood pressure, but also because Potassium Metabisulphite assists in the deposition of Potassium Tartrate crystals, while the Sodium salt does not.
Campden tablets, pre-measured doses of Potassium Metabisulphite, have the convenience of being precise doses, but with the drawback of the bother of crushing them up before using them

E224 (Potassium Metabisulfite) Properties (Theoretical)
Compound Formula    K2S2O5
Molecular Weight    222.32
Appearance    White crystals or powder
Melting Point    N/A
Boiling Point    N/A
Density    2.3 g/cm3
Solubility in H2O    N/A
Exact Mass    221.846128
Monoisotopic Mass    221.846128
E224 (Potassium Metabisulfite) Health & Safety Information
Signal Word    Warning
Hazard Statements    H315-H319-H335
Hazard Codes    Xi
Risk Codes    31-36/37/38
Safety Statements    26-36
RTECS Number    N/A
Transport Information    TT4920000
WGK Germany    1
MSDS / SDS    Request MSDS / SDS
About E224 (Potassium Metabisulfite)
E224 (Potassium Metabisulfite) is generally immediately available in most volumes. High purity, submicron and nanopowder forms may be considered. American Elements produces to many standard grades when applicable, including Mil Spec (military grade); ACS, Reagent and Technical Grade; Food, Agricultural and Pharmaceutical Grade; Optical Grade, USP and EP/BP (European Pharmacopoeia/British Pharmacopoeia) and follows applicable ASTM testing standards. Typical and custom packaging is available. Additional technical, research and safety (MSDS) information is available as is a Reference Calculator for converting relevant units of measurement.

Description
Details
E224 (Potassium Metabisulfite) powder is a wine additive used to kill wild yeast and bacteria, and it acts as a potent antioxidant, protecting both the color and flavors of wine.
"Meta" is a workhorse anti-oxidant and source of sulfur dioxide that comes as close to being mandatory use as any additive in winemaking.

Benefits of Potassium metabisulphite:
Potassium metabisulphite is a white crystalline powder with a pungent sulphur odour.
It is an inhibitor of the polyphenol oxidase enzyme.

Wine:
The wine making industry uses potassium metabisulphite as an additive during the bottling process.
It destroys microorganisms in the wine and prevents molds and bacteria from growing inside the wine bottle.
Potassium metabisulphite is a strong antioxidant that protects the colour and flavours of the wine.
It Increases the stability and prolongs shelf life to wine and cider.
Beer:
Potassium metabisulphite is sometimes used in the Brewing industry to inhibit the growth of wild bacteria and fungi.
This is called ‘stabilizing’. It kills most microorganisms.
Disinfectant:
Potassium metabisulphite is also used to neutralize chloramine that has been added to tap water at the source as a disinfectant.
Food preservatives:
Potassium metabisulphite is commonly usedas a food preservative for dried foods like potato chips, raisins and apples, as well as fruit concentrate juices.

Sterilizing:
Bottles: Directions: In 1 gallon (4lt.) of water, add 2 teaspoons of potassium metabisulfite and 1 tablespoon of citric acid.
Use it as a rinse.
If you're rinsing bottles, just go from bottle to bottle.
Equipment: Add 8 teaspoons of E224 (Potassium Metabisulfite) to 1 gallon (4lt.) of water, and then rinse your equipment in this solution for about 5 minutes to sanitize, and let drip dry.
In stronger doses, potassium Metabisulfite works well to sanitize your equipment, with no negative consequences.
Food: Potassium metabisulfite is a food preservative, which preserves the natural color of food and protects food against bacteria.

PHYSIOCHEMICAL PROPERTIES EP 001 (
K2S2O content [%]
Thiosulfate [%]
Iron [ppm]
Selenium [ppm]
Arsenic [ppm]
Lead [ppm]
Mercury [ppm]
Sodium [%]
Chlorides (in HCl) [g/kg] > 97,2

Functions:
1. Antioxidant - Reduces oxidation to prevent the formation of free radicals which may be harmful to health.
2. Preservative - Prevents and inhibits the growth of unwanted microorganisms which may be harmful
Potassium Metabisulphite is used as a food additive, also known as E224.
It is a common wine or must additive, in which it forms sulfur dioxide gas (SO2).
This both prevents most wild microorganisms from growing, and it acts as a potent antioxidant, protecting both the color and delicate flavors of wine.
Potassium metabisulfite is sometimes used in the brewing industry to inhibit the growth of wild bacteria and fungi.
This is called 'stabilizing'. It is also used to neutralize chloramine that has been added to tap water at the source as a disinfectant.
It is used both by homebrewers and commercial brewers alike.
It is not used as much for brewing beer, because the wort is almost always boiled, which kills most microorganisms.
It can also be added to strike water (the water used to mash the malted barley) in order to remove chloramines which can cause phenolic off flavors in beer.

Functions: Antioxidant, Preservative
Potassium metabisulfite, K2S2O5, also known as potassium pyrosulfite, is a white crystalline powder with a pungent sulfur odour.
The main use for the chemical is as an antioxidant or chemical sterilant.
It is a disulfite and is chemically very similar to sodium metabisulfite, with which it is sometimes used interchangeably.
Potassium metabisulfite is generally preferred out of the two as it does not contribute sodium to the diet.
Potassium metabisulfite has a monoclinic crystal structure which decomposes at 190 °C, yielding potassium sulfite and sulfur dioxide

Applications
It serves as a component of certain photographic developers and its solution is used in photographic fixing, in the textile industry for dyeing and cotton printing.
It is utilized to precipitate gold from solution in aqua regia.

Notes
Air sensitive.
Incompatible with oxidizing agents, acids, sodium nitrate and sodium nitrite.

Projects
Food and beverage preservative
Generate sulfur dioxide for use as a reducing agent
Reducing agent, used to precipitate gold from gold compounds
Bleach neutralization
Handling
Safety
Potassium metabisulfite may cause allergic reactions to people who are sensitive to sulfites.
It also gives off sulfur dioxide vapors, that are very irritating and unpleasant, as well as toxic.

Storage
Potassium metabisulfite must be kept out of hot or humid environments and away from water and acids while indoors.
Storing it in resealable bags, as it's generally sold, is a good choice.

Disposal
Potassium metabisulfite can be neutralized with bleach.

Depositor-Supplied Synonyms
POTASSIUM METABISULFITE
16731-55-8
Potassium disulfite
Potassium pyrosulfite
Dipotassium pyrosulfite
UNII-65OE787Q7W
Potassium metabisulfite [NF]
65OE787Q7W
Dipotassium disulfite
Potassium metabisulfite (NF)
Dipotassium disulphite
Dipotassium metabisulfite
CCRIS 1427
Potassium disulfite (K2S2O5)
HSDB 5062
Pyrosulfurous acid, dipotassium salt
EINECS 240-795-3
Kaliumpyrosulfit
ACMC-20ajuj
potassium metabisulphite
potassium meta-bisulfite
EC 240-795-3
Potassium disulfite, >=98%
E224 (Potassium Metabisulfite) (2:1)
CHEMBL2106901
DTXSID1021293
2K.O5S2
Potassium disulfite, AR, >=97%
Potassium disulfite, LR, >=95%
5222AF
MFCD00167605
AKOS015912829
Potassium disulfite, analytical standard
Potassium disulfite, USP, 51.8-57.6%
P2480
D05581
Potassium disulfite, BioUltra, >=97.0% (RT)
Q417881
J-010353
Potassium disulfite, Vetec(TM) reagent grade, 98%
Potassium disulfite, puriss. p.a., >=96% (iodometric), powder
Sulfite, potassium metabi-dipotassium oxidosulfanesulfonate oxide
Potassium disulfite, puriss.,