Stability of the solid

Anhydrous sodium hypochlorite can be prepared but, like many hypochlorites, it is highly unstable and decomposes explosively on heating or friction.The decomposition is accelerated by carbon dioxide at Earth’s atmospheric levels – around 4 parts per ten thousand.It is a white solid with the orthorhombic crystal structure.

Sodium hypochlorite can also be obtained as a crystalline pentahydrate NaOCl·5H₂O, which is not explosive and is much more stable than the anhydrous compound.The formula is sometimes given in its hydrous crystalline form as 2NaOCl·10H₂OThe Cl–O bond length in the pentahydrate is 1.686 Å The transparent, light greenish-yellow, orthorhombic crystals contain 44% NaOCl by weight and melt at 25–27 °C. The compound decomposes rapidly at room temperature, so it must be kept under refrigeration. At lower temperatures, however, it is quite stable: reportedly only 1% decomposition after 360 days at 7 °C .

A 1966 US patent claims that stable solid sodium hypochlorite dihydrate NaOCl·2H₂O can be obtained by carefully excluding chloride ions (Cl⁻), which are present in the output of common manufacturing processes and are said to catalyze the decomposition of hypochlorite into chlorate (ClO−3) and chloride. In one test, the dihydrate was claimed to show only 6% decomposition after 13.5 months of storage at −25 °C. The patent also claims that the dihydrate can be reduced to the anhydrous form by vacuum drying at about 50 °C, yielding a solid that showed no decomposition after 64 hours at −25 °C.

Equilibria and stability of solutions

At typical ambient temperatures, sodium hypochlorite is more stable in dilute solutions that contain solvated Na⁺ and OCl⁻ ions. The density of the solution is 1.093 g/mL at 5% concentration,and 1.21 g/mL at 14%, 20 °C.Stoichiometri solutions are fairly alkaline, with pH 11 or higher since the hypochlorite ion is a weak base:

OCl⁻ + H₂O ⇌ HOCl + OH⁻

The following species and equilibria are present in NaOCl/NaCl solutions.

HOCl(aq) ⇌ H⁺ + OCl⁻

HOCl(aq) + Cl⁻ + H⁺ ⇌ Cl₂(aq) + H₂O

Cl₂(aq) + Cl⁻ ⇌ Cl−3

Cl₂(aq) ⇌ Cl₂(g)

The second equilibrium equation above will be shifted to the right if the chlorine Cl₂ is allowed to escape as gas. The ratios of Cl₂, HOCl, and OCl⁻ in solution are also pH dependent. At pH below 2, the majority of the chlorine in the solution is in the form of dissolved elemental Cl₂. At pH greater than 7.4, the majority is in the form of hypochlorite ClO⁻.The equilibrium can be shifted by adding acids (such as hydrochloric acid) or bases (such as sodium hydroxide to the solution:

ClO⁻(aq) + 2 HCl(aq) → Cl₂(g) + H₂O + Cl⁻(aq)

Cl₂(g) + 2 OH⁻ → ClO⁻(aq) + Cl⁻(aq) + H₂O(aq)

At a pH of about 4, such as obtained by the addition of strong acids like hydrochloric acid, the amount of undissociated (nonionized) HOCl is highest. The reaction can be written as:

⁻OCl + H⁺ ⇌ HOCl

Sodium hypochlorite solutions combined with acid evolve chlorine gas, particularly strongly at pH < 2, by the reactions:

HOCl(aq) + Cl⁻ + H⁺ ⇌ Cl₂(aq) + H₂O

Cl₂(aq) ⇌ Cl₂(g)

At pH > 8, the chlorine is practically all in the form of hypochlorite anions (OCl⁻). The solutions are fairly stable at pH 11–12. Even so, one report claims that a conventional 13.6% NaOCl reagent solution lost 17% of its strength after being stored for 360 days at 7 °C.For this reason, in some applications one may use more stable chlorine-releasing compounds, such as calcium hypochlorite Ca(ClO)₂ or trichloroisocyanuric acid (CNClO)₃.

Anhydrous sodium hypochlorite is soluble in methanol, and solutions are stable.

Decomposition to chlorate or oxygen

In solution, under certain conditions, the hypochlorite anion may also disproportionate (autoxidize) to chloride and chlorate .

3 ClO⁻ + H⁺ → HClO₃ + 2 Cl⁻

Signal word Danger
Hazard statements H314 Causes severe skin burns and eye damage.
H400 Very toxic to aquatic life.
Precautionary statements P260 Do not breathe vapour/ spray.
P273 Avoid release to the environment.
P280 Wear protective gloves/ protective clothing/ eye protection/ face protection.
P303+P361+P353 IF ON SKIN (or hair): Take off immediately all contaminated clothing.
Rinse skin with water or shower.
P310 Immediately call a POISON CENTER/ doctor.
P501 Dispose of contents/ container in accordance with national regulations.
P390 Absorb spillage to prevent material damage.
P403+P233 Store in a well-ventilated place. Keep container tightly closed.
Supplemental label
information
EUH031 Contact with acids liberates toxic gas.
Contains sodium hypochlorite, solution … % Cl active.

General information Get medical attention if any discomfort continues. Show this Safety Data Sheet to the medical
personnel. Chemical burns must be treated by a physician.
Inhalation Move affected person to fresh air and keep warm and at rest in a position comfortable for
breathing. Maintain an open airway. Loosen tight clothing such as collar, tie or belt. Rinse
nose and mouth with water. Never give anything by mouth to an unconscious person. Get
medical attention if symptoms are severe or persist.
Ingestion Rinse mouth thoroughly with water. Give a few small glasses of water or milk to drink. Stop if
the affected person feels sick as vomiting may be dangerous. Get medical attention.

Skin contact It is important to remove the substance from the skin immediately. Rinse immediately with
plenty of water. Continue to rinse for at least 15 minutes and get medical attention. Chemical
burns must be treated by a physician.
Eye contact Rinse immediately with plenty of water. Do not rub eye. Remove any contact lenses and open
eyelids wide apart. Continue to rinse for at least 15 minutes and get medical attention.
Protection of first aiders It may be dangerous for first aid personnel to carry out mouth-to-mouth resuscitation.
4.2. Most important symptoms and effects, both acute and delayed
General information The severity of the symptoms described will vary dependent on the concentration and the
length of exposure.
Inhalation A single exposure may cause the following adverse effects: Corrosive to the respiratory tract.
Symptoms following overexposure may include the following: Severe irritation of nose and
throat.
Ingestion May cause chemical burns in mouth, oesophagus and stomach. Symptoms following
overexposure may include the following: Severe stomach pain. Nausea, vomiting.
Skin contact Causes severe burns. Symptoms following overexposure may include the following: Pain or
irritation. Redness. Blistering may occur.
Eye contact Causes serious eye damage. Symptoms following overexposure may include the following:

Pain. Profuse watering of the eyes. Redness.

Sodium hypochlorite is a chemical compound with the formula NaOCl or NaClO, comprising a sodium cation (Na+) and a hypochlorite anion (OCl−or ClO−). It may also be viewed as the sodium salt of hypochlorous acid. The anhydrous compound is unstable and may decompose explosively.[2][3] It can be crystallized as a pentahydrate NaOCl·5H2O, a pale greenish-yellow solid which is not explosive and is stable if kept refrigerated.

5.1. Extinguishing media
Suitable extinguishing media The product is not flammable. Extinguish with alcohol-resistant foam, carbon dioxide, dry
powder or water fog. Use fire-extinguishing media suitable for the surrounding fire.
Unsuitable extinguishing
media
Do not use water jet as an extinguisher, as this will spread the fire.
5.2. Special hazards arising from the substance or mixture
Specific hazards Containers can burst violently or explode when heated, due to excessive pressure build-up.
Severe corrosive hazard. Water used for fire extinguishing, which has been in contact with the
product, may be corrosive.
Hazardous combustion
products
Thermal decomposition or combustion products may include the following substances: Very
toxic or corrosive gases or vapours.
5.3. Advice for firefighters
Protective actions during
firefighting
Avoid breathing fire gases or vapours. Evacuate area. Keep upwind to avoid inhalation of
gases, vapours, fumes and smoke. Cool containers exposed to heat with water spray and
remove them from the fire area if it can be done without risk. Cool containers exposed to
flames with water until well after the fire is out. If a leak or spill has not ignited, use water
spray to disperse vapours and protect men stopping the leak. Avoid discharge to the aquatic
environment. Control run-off water by containing and keeping it out of sewers and
watercourses. If risk of water pollution occurs, notify appropriate authorities.
Special protective equipment
for firefighters
Regular protection may not be safe. Wear chemical protective suit. Wear positive-pressure

self-contained breathing apparatus (SCBA) and appropriate protective clothing. Firefighter’s
clothing conforming to European standard EN469 (including helmets, protective boots and
gloves) will provide a basic level of protection for chemical incidents.

Methods for cleaning up Wear protective clothing as described in Section 8 of this safety data sheet. Clear up spills
immediately and dispose of waste safely. This product is corrosive. If the product is soluble in
water, dilute the spillage with water and mop it up. Alternatively, or if it is not water-soluble,
absorb the spillage with an inert, dry material and place it in a suitable waste disposal
container. The contaminated absorbent may pose the same hazard as the spilled material.
Label the containers containing waste and contaminated materials and remove from the area
as soon as possible. Flush contaminated area with plenty of water. Wash thoroughly after
dealing with a spillage. Dangerous for the environment. Do not empty into drains. For waste
disposal.

Usage precautions Read and follow manufacturer’s recommendations. Wear protective clothing as described in
Section 8 of this safety data sheet. Keep away from food, drink and animal feeding stuffs.
Handle all packages and containers carefully to minimise spills. Keep container tightly sealed
when not in use. Avoid the formation of mists. Avoid contact with acids. Contact with acids
liberates toxic gas. This product is corrosive. Immediate first aid is imperative. Avoid
discharge to the aquatic environment. Do not handle until all safety precautions have been
read and understood. Do not handle broken packages without protective equipment. Do not
reuse empty containers.
Advice on general
occupational hygiene
Wash promptly if skin becomes contaminated. Take off contaminated clothing. Wash
contaminated clothing before reuse.

Storage precautions Keep out of the reach of children. Keep away from food, drink and animal feeding stuffs. Keep
only in the original container. Keep container tightly closed, in a cool, well ventilated place.
Keep containers upright. Protect containers from damage.
Storage class Corrosive storage.
Shelf life 23 days

Sodium hypochlorite is most often encountered as a pale greenish-yellow dilute solution commonly known as liquid bleach or simply bleach, a household chemical widely used (since the 18th century) as a disinfectant or a bleaching agent. The compound in solution is unstable and easily decomposes, liberating chlorine, which is the active principle of such products. Indeed, sodium hypochlorite is the oldest and still most important chlorine-based bleach.

Its corrosive properties, common availability, and reaction products make it a significant safety risk. In particular, mixing liquid bleach with other cleaning products, such as acids or ammonia, may produce toxic fumes.

Stability of the solid

Anhydrous sodium hypochlorite can be prepared but, like many hypochlorites, it is highly unstable and decomposes explosively on heating or friction. The decomposition is accelerated by carbon dioxide at atmospheric levels.[3][8] It is a white solid with the orthorhombic crystal structure.

Sodium hypochlorite can also be obtained as a crystalline pentahydrate NaOCl·5H2O, which is not explosive and is much more stable than the anhydrous compound. The formula is sometimes given as 2NaOCl·10H2O.[citation needed] The transparent light greenish yellow orthorombic[10][11] crystals contain 44% NaOCl by weight and melt at 25–27 °C. The compound decomposes rapidly at room temperature, so it must be kept under refrigeration. At lower temperatures, however, it is quite stable: reportedly only 1% decomposition after 360 days at 7 °C.

A 1966 US patent claims that stable solid sodium hypochlorite dihydrate NaOCl·2H2O can be obtained by carefully excluding chloride ions (Cl−), which are present in the output of common manufacturing processes and are said to catalyze the decomposition of hypochlorite into chlorate (ClO−3) and chloride. In one test, the dihydrate was claimed to show only 6% decomposition after 13.5 months storage at −25 °C. The patent also claims that the dihydrate can be reduced to the anhydrous form by vacuum drying at about 50 °C, yielding a solid that showed no decomposition after 64 hours at −25 °C.

Equilibria and stability of solutions

At typical ambient temperatures, sodium hypochlorite is more stable in dilute solutions that contain solvated Na+ and OCl−ions. The density of the solution is 1.093 g/mL at 5% concentration,[14] and 1.21 g/mL at 14%, 20 °C.[15] Stoichometric solutions are fairly alkaline, with pH 11 or more[5] since hypochlorous acid is a weak acid:

OCl−+ H2O ⇌ HOCl + OH−

The following species and equilibria are present in solutions of NaOCl:

HOCl (aq) ⇌ H++ OCl−

HOCl (aq) + Cl−+ H+⇌ Cl2 (aq) + H2O
Cl2 (aq) + Cl−⇌ Cl−3
Cl2 (aq) ⇌ Cl2 (g)
The second equilibrium equation above will be shifted to the right if the chlorine Cl2 is allowed to escape as gas. The ratios of Cl2, HOCl, and OCl−in solution are also pH dependent. At pH below 2, the majority of the chlorine in the solution is in the form of dissolved elemental Cl2. At pH greater than 7.4, the majority is in the form of hypochlorite ClO−. The equilibrium can be shifted by adding acids (such as hydrochloric acid) or bases (such as sodium hydroxide) to the solution:
ClO−(aq) + 2 HCl (aq) → Cl2 (g) + H2O (aq) + Cl−(aq)
The second equilibrium equation above will be shifted to the right if the chlorine Cl
2 is allowed to escape as gas. The ratios of Cl
2, HOCl, and OCl− in solution are also pH dependent. At pH below 2, the majority of the chlorine in the solution is in the form of dissolved elemental Cl
2. At pH greater than 7.4, the majority is in the form of hypochlorite ClO−
. The equilibrium can be shifted by adding acids (such as hydrochloric acid) or bases (such as sodium hydroxide) to the solution:
ClO−(aq) + 2 HCl (aq) → Cl2 (g) + H2O (aq) + Cl−(aq)
Cl2 (g) + 2 OH−→ ClO−(aq) + Cl−(aq) + H2O (aq)

At a pH of about 4, such as obtained by the addition of strong acids like hydrochloric acid, the amount of undissociated (nonionized) HOCl is highest. The reaction can be written as:

ClO−+ H+⇌ HClO

Sodium hypochlorite solutions combined with acid evolve chlorine gas, particularly strongly at pH < 2, by the reactions:

HOCl (aq) + Cl−+ H+⇌ Cl2 (aq) + H2O
Cl2 (aq) ⇌ Cl2 (g)

At pH > 8, the chlorine is practically all in the form of hypochlorite anions (OCl−). The solutions are fairly stable at pH 11–12. Even so, one report claims that a conventional 13.6% NaOCl reagent solution lost 17% of its strength after being stored for 360 days at 7 °C.[5] For this reason, in some applications one may use more stable chlorine-releasing compounds, such as calcium hypochlorite Ca(ClO)2 or trichloroisocyanuric acid (CNClO)3.

Anhydrous sodium hypochlorite is soluble in methanol, and solutions are stable.[citation needed]

Oxidation of organic compounds

Oxidation of starch by sodium hypochlorite, that adds carbonyl and carboxyl groups, is relevant to the production of modified starch products.[20]

In the presence of a phase-transfer catalyst, alcohols are oxidized to the corresponding carbonyl compound (aldehyde or ketone).[21][5] Sodium hypochlorite can also oxidize organic sulfides to sulfoxides or sulfones, disulfides or thiols to sulfonyl chlorides or bromides, imines to oxaziridines.[5] It can also de-aromatize phenols.[5]

Oxidation of metals and complexes

Heterogeneous reactions of sodium hypochlorite and metals such as zinc proceed slowly to give the metal oxide or hydroxide:

NaOCl + Zn → ZnO + NaCl

Homogeneous reactions with metal coordination complexes proceed somewhat faster. This has been exploited in the Jacobsen epoxidation.

Sodium hypochlorite has a long history. Around 1785 the Frenchman Berthollet developed liquid bleaching agents based on sodium hypochlorite. The Javel company introduced this product and called it ‘liqueur de Javel’. At first, it was used to bleach cotton. Because of its specific characteristics it soon became a popular compound. Hypochlorite can remove stains from clothes at room temperature. In France, sodium hypochlorite is still known as ‘eau de Javel’.

What are the characteristics of sodium hypochlorite?

Sodium hypochlorite is a clear, slightly yellowish solution with a characteristic odor.
Sodium hypochlorite has a relative density of is 1,1 (5,5% watery solution).
As a bleaching agent for domestic use it usually contains 5% sodium hypochlorite (with a pH of around 11, it is irritating). If it is more concentrated, it contains a concentration 10-15% sodium hypochlorite (with a pH of around 13, it burns and is corrosive).?

Sodium hypochlorite is a clear, slightly yellowish solution with a characteristic odor.
Sodium hypochlorite has a relative density of is 1,1 (5,5% watery solution).
As a bleaching agent for domestic use it usually contains 5% sodium hypochlorite (with a pH of around 11, it is irritating). If it is more concentrated, it contains a concentration 10-15% sodium hypochlorite (with a pH of around 13, it burns and is corrosive).
Sodium hypochlorite is unstable. Chlorine evaporates at a rate of 0,75 gram active chlorine per day from the solution. Then heated sodium hypochlorite disintegrates. This also happens when sodium hypochlorite comes in contact with acids, sunlight, certain metals and poisonous and corrosive gasses, including chlorine gas. Sodium hypochlorite is a strong oxidator and reacts with flammable compounds and reductors. Sodium hypochlorite solution is a weak base that is inflammable.
These characteristics must be kept in mind during transport, storage and use of sodium hypochlorite.

What happens to the pH value when sodium hypochlorite is added to water?

Due to the presence of caustic soda in sodium hypo chlorite, the pH of the water is increased. When sodium hypo chlorite dissolves in water, two substances form, which play a role in for oxidation and disinfection. These are hypochlorous acid (HOCl) and the less active hypochlorite ion (OCl-). The pH of the water determines how much hypochlorous acid is formed. While sodium hypochlorite is used, hydrochloric acid (HCl) is used to lower the pH. Sulfuric acid (H2SO4) can be used as an alternative for acetic acid. Less harmful gasses are produced when sulfuric acid is used. Sulfuric acid is a strong acid that strongly reacts with bases and that is very corrosion.