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Chemistry

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.[2] The decomposition is accelerated by carbon dioxide at atmospheric levels.[3][8] It is a white solid with the orthorhombic crystal structure.[9]

Sodium hypochlorite can also be obtained as a crystalline pentahydrate NaOCl·5H
2
O
, which is not explosive and is much more stable than the anhydrous compound.[3][4] The formula is sometimes given as 2NaOCl·10H
2
O
.[citation needed] The transparent light greenish yellow orthorhombic[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.[5][12]

A 1966 US patent claims that stable solid sodium hypochlorite dihydrate NaOCl·2H
2
O
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.[13]

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] Stoichiometric solutions are fairly alkaline, with pH 11 or higher[5] since hypochlorous acid is a weak acid:

OCl
+ H
2
O
⇌ HOCl + OH

The following species and equilibria are present in solutions of NaOCl:[16]

HOCl (aq) ⇌ H+
+ OCl
HOCl (aq) + Cl
+ H+
Cl
2
(aq) + H
2
O
Cl
2
(aq) + Cl
Cl
3
Cl
2
(aq) ⇌ Cl
2
(g)

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
.[6] 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) → Cl
2
(g) + H
2
O
(aq) + Cl
(aq)
Cl
2
(g) + 2 OH
ClO
(aq) + Cl
(aq) + H
2
O
(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, particularl

Sodium hypochlorite is most often encountered as a pale greenish-yellow dilute solution referred to as liquid bleach, which is a household chemical widely used (since the 18th century) as a disinfectant or a bleaching agent.

In solution, the compound is unstable and easily decomposes, liberating chlorine which is the active principle of such products. Sodium hypochlorite is the oldest and still most important chlorine-based bleach.[6][7]

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.[8]

Anhydrous sodium hypochlorite can be prepared but, like many hypochlorites, it is highly unstable and decomposes explosively on heating or friction.[2] The decomposition is accelerated by carbon dioxide at atmospheric levels.[3][8] It is a white solid with the orthorhombic crystal structure.[9]

Sodium hypochlorite can also be obtained as a crystalline pentahydrate NaOCl·5H
2
O
, which is not explosive and is much more stable than the anhydrous compound.[3][4] The formula is sometimes given as 2NaOCl·10H
2
O
.[citation needed] The transparent light greenish yellow orthorhombic[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.[5][12]

A 1966 US patent claims that stable solid sodium hypochlorite dihydrate NaOCl·2H
2
O
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.[13]

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] Stoichiometric solutions are fairly alkaline, with pH 11 or higher[5] since hypochlorous acid is a weak acid:

OCl
+ Hcrystalline pentahydrate NaOCl·5H
2
O
, which is not explosive and is much more stable than the anhydrous compound.[3][4] The formula is sometimes given as 2NaOCl·10H
2
O
.[citation needed] The transparent light greenish yellow orthorhombic[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.[5][12]

A 1966 US patent claims that stable solid sodium hypochlorite dihydrate NaOCl·2H
2
O
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.[13]

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] Stoichiometric solutions are fairly alkaline, with pH 11 or higher[5] since hypochlorous acid is a weak acid:

OCl
+ HNaOCl:[16]

HOCl (aq) ⇌ H+
+ OCl
HOCl (aq) + Cl
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
.[6] 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) → Cl
2
(g) + H
2
O
(aq) + Cl
(aq)
Cl
2
(g) + 2 OH
ClO
(aq) + Cl
(aq) + H
2
O
(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
+ Hstrong 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+
Cl
2
(aq) + H
2
O
Cl
2
(aq) ⇌ Cl
2
(g)

At pH > 8, the chlorine is practically all in the form of hypochlorite anions (OClHOCl (aq) + Cl
+ H+
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]

Decomposition to chlorate or oxygen

In solution, under certain conditions, the hypochlorite anion may also disproportionate (autoxidize) to chloride and chlorate:[17]

3 ClO
+ H+
HClOmethanol, and solutions are stable.[citation needed]

In solution, under certain conditions, the hypochlorite anion may also disproportionate (autoxidize) to chloride and chlorate:[17]

3 ClO
+ HIn particular, this reaction occurs in sodium hypochlorite solutions at high temperatures, forming sodium chlorate and sodium chloride:[17][18]

3 NaOCl (aq) → 2 NaCl (aq) + NaClO
3
(aq)

This reaction is exploited in the industrial production of sodium chlorate.

An alternative decomposition of hypochlorite produces oxygen instead:

2 OCl
→ 2 Cl
+ OOCl
→ 2 Cl

An alternative decomposition of hypochlorite produces oxygen instead:

In hot sodium hypochlorite solutions, this reaction competes with chlorate formation, yielding sodium chloride and oxygen gas:[17]

2 NaOCl (aq) → 2 NaCl (aq) + O
2
(g)

These two decomposition reactions of NaClO solutions are maximized at pH around 6. The chlorate-producing reaction predominates at pH above 6, while the oxygen one becomes significant below that. For example, at 80 °C, with NaOCl and NaCl concentrations of 80 mM, and pH 6–6.5, the chlorate is produced with ∼95% efficiency. The oxygen pathway predominates at pH 10.[17]

These two decomposition reactions of NaClO solutions are maximized at pH around 6. The chlorate-producing reaction predominates at pH above 6, while the oxygen one becomes significant below that. For example, at 80 °C, with NaOCl and NaCl concentrations of 80 mM, and pH 6–6.5, the chlorate is produced with ∼95% efficiency. The oxygen pathway predominates at pH 10.[17] This decomposition is affected by light[18] and metal ion catalysts such as copper, nickel, cobalt,[17] and iridium.[19] Catalysts like sodium dichromate Na
2
Cr
2
O
7
and sodium molybdate Na
2
MoO
4
may be added industrially to reduce the oxygen pathway, but a report claims that only the latter is effective.[17]

Titration

Titration of hypochlorite solutions is often done by adding a measured sample to an excess amo

Titration of hypochlorite solutions is often done by adding a measured sample to an excess amount of acidified solution of potassium iodide (KI) and then titrating the liberated iodine (I
2
) with a standard solution of sodium thiosulfate or phenyl arsine oxide, using starch as indicator, until the blue color disappears.[11]

According to one US patent, the stability of sodium hypochlorite content of solids or solutions can be determined by monitoring the infrared absorption due to the O–Cl bond. The characteristic wavelength is given as 140.25 infrared absorption due to the O–Cl bond. The characteristic wavelength is given as 140.25 μm for water solutions, 140.05 μm for the solid dihydrate NaOCl·2H
2
O
, and 139.08 μm for the anhydrous mixed salt Na
2
(OCl)(OH)
.[13]

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).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]

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 epoxidat

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

carbon dioxide to form sodium carbonate:

2 NaOCl + CO
2
+ Hmonochloramine, dichloramines, and nitrogen trichloride:

NH
3
+ NaOCl → NH
2
Cl
+ NaOH
NH
2
Cl
+ NaOCl → NHClSodium thiosulfate is an effective chlorine neutralizer. Rinsing with a 5 mg/L solution, followed by washing with soap and water, will remove chlorine odor from the hands.[22]

Production

Chlorination of soda

Potassium hypochlorite was first produced in 1789 by Claude Louis Berthollet in his laboratory on the Quai de Javel in Paris, France, by passing chlorine gas through a solution of potash lye. The resulting liquid, known as "Eau de Javel" ("Javel water"), was a weak solution of potassium hypochlorite. Antoine Labarraque replaced potash lye by the cheaper soda lye, thus obtaining sodium hypochlorite (Eau de Labarraque).[23][24]

Cl2 (g) + 2 NaOH (aq) → NaCl (aq) + NaClO (aq) + H2O (aq)

Hence, chlorine is simultaneously reduced and oxidized; this process is known as disproportionation.

The process is also used to prepare the pentahydrate NaOCl·5H

Potassium hypochlorite was first produced in 1789 by Claude Louis Berthollet in his laboratory on the Quai de Javel in Paris, France, by passing chlorine gas through a solution of potash lye. The resulting liquid, known as "Eau de Javel" ("Javel water"), was a weak solution of potassium hypochlorite. Antoine Labarraque replaced potash lye by the cheaper soda lye, thus obtaining sodium hypochlorite (Eau de Labarraque).[23][24]

Cl2 (g) + 2 NaOH (aq) → NaCl (aq) + NaClO (aq) + H2O (aq)

Hence, chlorine is simultaneously reduced and oxidized; this process is known as disproportionation.

The process is also used to prepare the pentahydrate NaOCl·5Hreduced and oxidized; this process is known as disproportionation.

The process is also used to prepare the pentahydrate NaOCl·5The process is also used to prepare the pentahydrate NaOCl·5H
2
O
for industrial and laboratory use. In a typical process, chlorine gas is added to a 45–48% NaOH solution. Some of the sodium chloride precipitates and is removed by filtration, and the pentahydrate is then obtained by cooling the filtrate to 12 °C .[5]

Another method involved by reaction of sodium carbonate ("washing soda") with chlorinated lime ("bleaching powder"), a mixture of calcium hypochlorite Ca(OCl)
2
, calcium chloride CaCl
2
, and calcium hydroxide Ca(OH)
2
:

Na
2
CO[25]

Electrolysis of brine

Near the end of the nineteenth century, E. S. Smith patented the chloralkali process: a method of producing sodium hypochlorite involving the electrolysis of brine to produce sodium hydroxide and chlorine gas, which then mixed to form sodium hypochlorite.[26][24][27] The key reactions are:

2 Cl → Cl2 + 2 e (at the anode)
2 H
2
O
+ 2 eH
2
+ 2 HO
(at the cathode)

Both electric power and brine solution were in cheap supply at the time, and various enterprising marketers took advantage of the situation to satisfy the market's demand for sodium hypochlorite. Bottled solutions of sodium hypochlorite were sold under numerous trade names.

Today, an improved version of this method, known as the Hooker process (named after Hooker Chemicals, acquired by Occidental Petroleum), is the only large-scale industrial method of sodium hypochlorite production. In the process, sodium hypochlorite (NaClO) and sodium chloride (NaCl) are formed when chlorine is passed into cold dilute sodium hydroxide solution. The chlorine is prepared industrially by electrolysis with minimal separation between the anode and the cathode. The solution must be kept below 40 °C (by cooling coils) to prevent the undesired formation of sodium chlorate.

Commercial solutions always contain significant amounts of sodium chloride (common salt) as the main by-product, as seen in the equation above.

From hypochlorous acid and soda

A 1966 patent describes

Near the end of the nineteenth century, E. S. Smith patented the chloralkali process: a method of producing sodium hypochlorite involving the electrolysis of brine to produce sodium hydroxide and chlorine gas, which then mixed to form sodium hypochlorite.[26][24][27] The key reactions are:

2 Cl → Cl2 + 2 e (at the anode)
2 HOccidental Petroleum), is the only large-scale industrial method of sodium hypochlorite production. In the process, sodium hypochlorite (NaClO) and sodium chloride (NaCl) are formed when chlorine is passed into cold dilute sodium hydroxide solution. The chlorine is prepared industrially by electrolysis with minimal separation between the anode and the cathode. The solution must be kept below 40 °C (by cooling coils) to prevent the undesired formation of sodium chlorate.

Commercial solutions always contain significant amounts of sodium chloride (common salt) as the main by-product, as seen in the equation above.

Occidental Petroleum), is the only large-scale industrial method of sodium hypochlorite production. In the process, sodium hypochlorite (NaClO) and sodium chloride (NaCl) are formed when chlorine is passed into cold dilute sodium hydroxide solution. The chlorine is prepared industrially by electrolysis with minimal separation between the anode and the cathode. The solution must be kept below 40 °C (by cooling coils) to prevent the undesired formation of sodium chlorate.

Commercial solutions always contain significant amounts of sodium chloride (common salt) as the main by-product, as seen in the equation above.

A 1966 patent describes the production of solid stable dihydrate NaOCl·2H
2
O
by reacting a chloride-free solution of hypochlorous acid HClO (such as prepared from chlorine monoxide ClO and water), with a concentrated solution of sodium hydroxide. In a typical preparation, 255 mL of a solution with 118 g/L HClO is slowly added with stirring to a solution of 40 g of NaOH in water 0 °C. Some sodium chloride precipitates and is removed by fitration. The solution is vacuum evaporated at 40–50 °C and 1–2 mmHg until the dihydrate crystallizes out. The crystals are vacuum-dried to produce a free-flowing crystalline powder.[13]

The same principle was used in another 1991 patent to produce concentrated slurries of the pentahydrate NaClO·5Hslurries of the pentahydrate NaClO·5H
2
O
. Typically, a 35% solution (by weight) of HClO is combined with sodium hydroxide at about or below 25 °C. The resulting slurry contains about 35% NaClO, and are relatively stable due to the low concentration of chloride.[28]

Sodium hypochlorite can be easily produced for research purposes by reacting ozone with salt.

NaCl + O3 → NaClO + O2

This reaction happens at room temperature and can be helpful for oxidizing alcohols.

Packaging and sale

Sodium hypochlorite has destaining properties.[35] Among other applications, it can be used to remove mold stains, dental stains

Sodium hypochlorite has destaining properties.[35] Among other applications, it can be used to remove mold stains, dental stains caused by fluorosis,[36] and stains on crockery, especially those caused by the tannins in tea. It has also been used in laundry detergents and as a surface cleaner.

Its bleaching, cleaning, deodorizing and caustic effects are due to oxidation and hydrolysis (saponification). Organic dirt exposed

Its bleaching, cleaning, deodorizing and caustic effects are due to oxidation and hydrolysis (saponification). Organic dirt exposed to hypochlorite becomes water-soluble and non-volatile, which reduces its odor and facilitates its removal.

Sodium hypochlorite in solution exhibits broad spectrum anti-microbial activity and is widely used in healthcare facilities in a variety of settings.[37] It is usually diluted in water depending on its intended use. "Strong chlorine solution" is a 0.5% solution of hypochlorite (containing approximately 5000 ppm free chlorine) used for disinfecting areas contaminated with body fluids, including large blood spills (the area is first cleaned with detergent before being disinfected).[37][38] It may be made by diluting household bleach as appropriate (normally 1 part bleach to 9 parts water).[39] Such solutions have been demonstrated to inactivate both C. difficile[37] and HPV.[40] "Weak chlorine solution" is a 0.05% solution of hypochlorite used for washing hands, but is normally prepared with calcium hypochlorite granules.[38]

"Dakin's Solution" is a disinfectant solution containing low concentration of sodium hypochlorite and some boric acid or sodium bicarbonate to stabilize the pH. It has been found to be effective with NaOCl concentrations as low as 0.025%."Dakin's Solution" is a disinfectant solution containing low concentration of sodium hypochlorite and some boric acid or sodium bicarbonate to stabilize the pH. It has been found to be effective with NaOCl concentrations as low as 0.025%.[41]

US government regulations allow food processing equipment and food contact surfaces to be sanitized with solutions containing bleach, provided that the solution is allowed to drain adequately before contact with food, and that the solutions do not exceed 200 parts per million (ppm) available chlorine (for example, one tablespoon of typical household bleach containing 5.25% sodium hypochlorite, per gallon of water).[42] If higher concentrations are used, the surface must be rinsed with potable water after sanitizing.

A similar concentration of bleach in warm water is used to sanitize surfaces prior to brewing of beer or wine. Surfaces must be rinsed with sterilized (boiled) water to avoid imparting flavors to the brew; the chlorinated byproducts of sanitizing surfaces are also harmful. The mode of disinfectant action of sodium hypochlorite is similar to that of hypochlorous acid.

Solutions containing more than 500 ppm available chlorine are corrosive to some metals, alloys and many thermoplastics (such as acetal resin) and need to be thoroughly removed afterwards, so the bleach disinfection is sometimes followed by an ethanol disinfection. Liquids containing sodium hypochlorite as the main active component are also used for household cleaning and disinfection, for example toilet cleaners.[43] Some cleaners are formulated to be viscous so as not to drain quickly from vertical surfaces, such as the inside of a toilet bowl.

The undissociated (nonionized) hypochlorous acid is believed to react with and inactivate bacterial and viral enzymes.

Neutrophils of the human immune system produce small amounts of hypochlorite inside phagosomes, which digest bacteria and viruses.

Sodium hypochlorite has deodorizing properties, which go hand in hand with its cleaning properties.[35]

Waste water treatment

Dilute bleach baths have been used for decades to treat moderate to severe eczema in humans,[47][48] but it has not been clear why they work. According to work published by researchers at the Stanford University School of Medicine in November 2013, a very dilute (0.005%) solution of sodium hypochlorite in water was successful in treating skin damage with an inflammatory component caused by radiation therapy, excess sun exposure or aging in laboratory mice. Mice with radiation dermatitis given daily 30-minute baths in bleach solution experienced less severe skin damage and better healing and hair regrowth than animals bathed in water. A molecule called nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is known to play a critical role in inflammation, aging, and response to radiation. The researchers found that if NF-κB activity was bl

Dilute bleach baths have been used for decades to treat moderate to severe eczema in humans,[47][48] but it has not been clear why they work. According to work published by researchers at the Stanford University School of Medicine in November 2013, a very dilute (0.005%) solution of sodium hypochlorite in water was successful in treating skin damage with an inflammatory component caused by radiation therapy, excess sun exposure or aging in laboratory mice. Mice with radiation dermatitis given daily 30-minute baths in bleach solution experienced less severe skin damage and better healing and hair regrowth than animals bathed in water. A molecule called nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is known to play a critical role in inflammation, aging, and response to radiation. The researchers found that if NF-κB activity was blocked in elderly mice by bathing them in bleach solution, the animals' skin began to look younger, going from old and fragile to thicker, with increased cell proliferation. The effect diminished after the baths were stopped, indicating that regular exposure was necessary to maintain skin thickness.[47][49]

Safety

It is estimated that there are about 3,300 accident

It is estimated that there are about 3,300 accidents needing hospital treatment caused by sodium hypochlorite solutions each year in British homes (RoSPA, 2002).

Oxidation and corrosion

In spite of its

In spite of its strong biocidal action, sodium hypochlorite per se has limited environmental impact, since the hypochlorite ion rapidly degrades before it can be absorbed by living beings.[54]

However, one major concern arising from sodium hypochlorite use is that it tends to form persistent chlorinated organic compounds, including known carcinogens, that can be absorbed by organisms and enter the However, one major concern arising from sodium hypochlorite use is that it tends to form persistent chlorinated organic compounds, including known carcinogens, that can be absorbed by organisms and enter the food chain. These compounds may be formed during household storage and use as well during industrial use.[34] For example, when household bleach and wastewater were mixed, 1–2% of the available chlorine was observed to form organic compounds.[34] As of 1994, not all the byproducts had been identified, but identified compounds include chloroform and carbon tetrachloride.[34] The estimated exposure to these chemicals from use is estimated to be within occupational exposure limits.[34]