sodium hypochlorite#Production

Anhydrous sodium hypochlorite can be prepared but, like many hypochlorites, it is highly unstable and decomposes explosively on heating or friction.{{cite book |last=Urben |first=Peter |title=Bretherick's Handbook of Reactive Chemical Hazards |date=2006 |edition=7th |volume=1 |page=1433 |publisher=Elsevier |isbn=978-0-08-052340-8}} The decomposition is accelerated by carbon dioxide at Earth's atmospheric levels - around 4 parts per ten thousand.{{cite journal |last=Hamano |first=Arihiro |title=The formation and decomposition of sodium hypochlorite anhydrous salt and its pentahydrate |date=1997 |journal=Science and Technology of Energetic Materials |volume=58 |issue=4 |pages=152–155}} It is a white solid with the orthorhombic crystal structure.{{cite book |last=Yaws |first=Carl L. |title=The Yaws Handbook of Physical Properties for Hydrocarbons and Chemicals |date=2015 |edition=2nd |page=734 |publisher=Gulf Professional Publishing |isbn=978-0-12-801146-1}}

Sodium hypochlorite can also be obtained as a crystalline pentahydrate {{chem2|NaOCl*5H2O}}, which is not explosive and is much more stable than the anhydrous compound.{{cite journal |last=Applebey |first=Malcolm Percival |title=Sodium hypochlorite |date=1919 |journal=Journal of the Chemical Society, Transactions |volume=115 |issue=XCVI |pages=1106–1109 |doi=10.1039/CT9191501106 |url=https://zenodo.org/records/2513175}} The formula is sometimes given in its hydrous crystalline form as {{chem2|2NaOCl*10H2O}}.{{cite web |title=What is sodium hypochlorite used for? |last=Bell-Young |first=Lucy |date=29 September 2019 |website=Chemicals.co.uk |url=https://www.chemicals.co.uk/blog/what-is-sodium-hypochlorite-used-for |access-date=29 August 2023}} The Cl–O bond length in the pentahydrate is 1.686 Å. The transparent, light greenish-yellow, orthorhombic"{{cite web |title=Sodium Hypochlorite Pentahydrate, {{chem|NaOCl}}·5{{chem|H|2|O}} |work=MatWeb Material Property Data website |url=https://www.matweb.com/search/DataSheet.aspx?MatGUID=46d79c6b01804a3f89e237c8ddfcb67e |access-date=2018-07-12}}{{cite web |title=Sodium Hypochlorite |work=StudFiles |url=https://studfile.net/preview/409824/page:2/ |access-date=2018-06-14}} 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.{{cite journal |vauthors=Kirihara M, Okada T, Sugiyama Y, Akiyoshi M, Matsunaga T, Kimura Y |title=Sodium Hypochlorite Pentahydrate Crystals (NaOCl· 5H2O): A Convenient and Environmentally Benign Oxidant for Organic Synthesis. |journal=Organic Process Research & Development |date=December 2017 |volume=21 |issue=12 |pages=1925–37 |doi=10.1021/acs.oprd.7b00288 |doi-access=free}}{{cite journal |vauthors=Okada T, Asawa T, Sugiyama Y, Iwai T, Kirihara M, Kimura Y |title=Sodium hypochlorite pentahydrate (NaOCl·5H2O) crystals; An effective re-oxidant for TEMPO oxidation. |journal=Tetrahedron |date=June 2016 |volume=72 |issue=22 |pages=2818–27 |doi=10.1016/j.tet.2016.03.064}}

A 1966 US patent claims that stable solid sodium hypochlorite dihydrate {{chem2|NaOCl*2H2O}} can be obtained by carefully excluding chloride ions ({{chem2|Cl-}}), which are present in the output of common manufacturing processes and are said to catalyze the decomposition of hypochlorite into chlorate ({{chem2|ClO3-}}) 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.{{cite patent |inventor=Walsh RH, Dietz A |gdate=1966 |country=US |number=3498924 |title=Process for preparing stable sodium hypochlorites}}

At typical ambient temperatures, sodium hypochlorite is more stable in dilute solutions that contain solvated {{chem2|Na+}} and {{chem2|OCl-}} ions. The density of the solution is 1.093 g/mL at 5% concentration,{{cite web |title=Sodium hypochlorite |work=PubChem |publisher=U.S. National Library of Medicine |url=https://pubchem.ncbi.nlm.nih.gov/compound/sodium_hypochlorite}} and 1.21 g/mL at 14%, 20 °C.Environment Canada (1985): "Tech Info for Problem Spills: Sodium Hypochlorite (Draft)". Stoichiometric solutions are fairly alkaline, with pH 11 or higher since the hypochlorite ion is a weak base:

:{{chem2|OCl- + H2O ⇌ HOCl + OH-}}

The following species and equilibria are present in NaOCl/NaCl solutions:{{cite journal |vauthors=Wang L, Bassiri M, Najafi R, Najafi K, Yang J, Khosrovi B, Hwong W, Barati E, Belisle B, Celeri C, Robson MC |display-authors=6 |title=Hypochlorous acid as a potential wound care agent: part I. Stabilized hypochlorous acid: a component of the inorganic armamentarium of innate immunity |journal=Journal of Burns and Wounds |volume=6 |pages=e5 |date=April 2007 |pmid=17492050 |pmc=1853323}}

:{{chem2|HOCl(aq) ⇌ H+ + OCl-}}

:{{chem2|HOCl(aq) + Cl- + H+ ⇌ Cl2(aq) + H2O}}

:{{chem2|Cl2(aq) + Cl- ⇌ Cl3-}}

:{{chem2|Cl2(aq) ⇌ Cl2(g)}}

The second equilibrium equation above will be shifted to the right if the chlorine {{chem2|Cl2}} is allowed to escape as gas. The ratios of {{chem2|Cl2}}, HOCl, and {{chem2|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 {{chem2|Cl2}}. At pH greater than 7.4, the majority is in the form of hypochlorite {{chem2|ClO-}}. The equilibrium can be shifted by adding acids (such as hydrochloric acid) or bases (such as sodium hydroxide) to the solution:

:{{chem2|ClO-(aq) + 2 HCl(aq) → Cl2(g) + H2O + Cl-(aq)}}

:{{chem2|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:

:{{chem2|-OCl + H+ ⇌ HOCl}}

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

:{{chem2|HOCl(aq) + Cl- + H+ ⇌ Cl2(aq) + H2O}}

:{{chem2|Cl2(aq) ⇌ Cl2(g)}}

At pH > 8, the chlorine is practically all in the form of hypochlorite anions ({{chem2|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 {{chem2|Ca(ClO)2}} or trichloroisocyanuric acid {{chem2|(CNClO)3}}.{{citation needed|date=November 2023}}

Anhydrous sodium hypochlorite is soluble in methanol, and solutions are stable.{{citation needed|date=June 2018}}

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

:{{chem2|3 ClO- + H+ → HClO3 + 2 Cl-}}

In particular, this reaction occurs in sodium hypochlorite solutions at high temperatures, forming sodium chlorate and sodium chloride:{{cite journal |vauthors=Sandin S, Karlsson RK, Cornell A |title=Catalyzed and uncatalyzed decomposition of hypochlorite in dilute solutions. |journal=Industrial & Engineering Chemistry Research |date=April 2015 |volume=54 |issue=15 |pages=3767–74 |doi=10.1021/ie504890a}}{{cite journal |last1=Hamano |first1=Arihiro |last2=Ikeda |first2=Akie |title=The pH effect on the photodecomposition of sodium hypochlorite solution |date=1995 |journal=Science and Technology of Energetic Materials |volume=56 |issue=2 |pages=59–63}}

:{{chem2|3 NaOCl(aq) → 2 NaCl(aq) + NaClO3(aq)}}

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

An alternative decomposition of hypochlorite produces oxygen instead:

:{{chem2|2 OCl- → 2 Cl- + O2}}

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

:{{chem2|2 NaOCl(aq) → 2 NaCl(aq) + O2(g)}}

These two decomposition reactions of {{chem2|NaOCl}} solutions are maximized at pH around 6. For example, at 80 °C, with {{chem2|NaOCl}} and {{chem2|NaCl}} concentrations of 80 mM, over the pH range 5−10.5, both reactions have rate proportional to $[\backslash ce\{HOCl\}]^2\; [\backslash ce\{OCl-\}]$, decomposition is fastest at pH 6.5, and chlorate is produced with ~95% efficiency. Above pH 11, both reactions have rate proportional to $[\backslash ce\{OCl-\}]^2$, decomposition is much slower, and chlorate is produced with ~90% efficiency.{{cite journal |last1=Adam |first1=Luke C. |last2=Gordon |first2=Gilbert |title=Hypochlorite Ion Decomposition: Effects of Temperature, Ionic Strength, and Chloride Ion |journal=Inorganic Chemistry |date=20 February 1999 |volume=38 |issue=6 |pages=1299–1304 |doi=10.1021/ic980020q|pmid=11670917 }} This decomposition is affected by light and metal ion catalysts such as copper, nickel, cobalt, and iridium.{{cite journal |last1=Ayres |first1=Gilbert H. |last2=Booth |first2=Max H. |title=Catalytic Decomposition of Hypochlorite Solution by Iridium Compounds. I. The pH-Time Relationship. |date=1955 |journal=Journal of the American Chemical Society |volume=77 |issue=4 |pages=825–827 |doi=10.1021/ja01609a001|bibcode=1955JAChS..77..825A }} Catalysts like sodium dichromate {{chem2|Na2Cr2O7}} and sodium molybdate {{chem2|Na2MoO4}} may be added industrially to reduce the oxygen pathway, but a report claims that only the latter is effective.{{failed verification|date=October 2024}}

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 ({{chem2|I2}}) with a standard solution of sodium thiosulfate or phenylarsine oxide, using starch as indicator, until the blue color disappears.

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 μm for water solutions, 140.05 μm for the solid dihydrate {{chem2|NaOCl*2H2O}}, and 139.08 μm for the anhydrous mixed salt {{chem2|Na2(OCl)(OH)}}.

Oxidation of starch by sodium hypochlorite, which adds carbonyl and carboxyl groups, is relevant to the production of modified starch products.ASC – PT Asahimas Chemical (2009): "[https://www.asc.co.id/index.php/en/products/product/sodium-hypochloride Sodium hypochlorite]". Online product description. Accessed on 2018-06-14.

In the presence of a phase-transfer catalyst, alcohols are oxidized to the corresponding carbonyl compound (aldehyde or ketone).{{cite journal |vauthors=Mirafzal GA, Lozeva AM |title=Phase transfer catalyzed oxidation of alcohols with sodium hypochlorite |year=1998 |journal=Tetrahedron Letters |volume=39 |issue=40 |pages=7263–7266 |doi=10.1016/S0040-4039(98)01584-6}} Sodium hypochlorite can also oxidize organic sulfides to sulfoxides or sulfones; disulfides or thiols to sulfonyl halides; and imines to oxaziridines. It can also de-aromatize phenols.

Heterogeneous reactions of sodium hypochlorite and metals such as zinc proceed slowly to give the metal oxide or hydroxide:{{citation needed|date=November 2023}}

:NaOCl + Zn → ZnO + NaCl

Homogeneous reactions with metal coordination complexes proceed somewhat faster. This has been exploited in the Jacobsen epoxidation.{{citation needed|date=November 2023}}

If not properly stored in airtight containers, sodium hypochlorite reacts with carbon dioxide to form sodium carbonate:

:{{chem2|2 NaOCl + CO2 + H2O → Na2CO3 + 2 HOCl}}

Sodium hypochlorite reacts with most nitrogen compounds to form volatile monochloramine, dichloramines, and nitrogen trichloride:

:{{chem2|NH3 + NaOCl → NH2Cl + NaOH}}

:{{chem2|NH2Cl + NaOCl → NHCl2 + NaOH}}

:{{chem2|NHCl2 + NaOCl → NCl3 + NaOH}}

Sodium 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.{{cite book |title=Standard Methods For the Examination of Water and Wastewater |edition=21 |editor-last1=Eaton |editor-first1=Andrew D. |editor-last2=Greenberg |editor-first2=Arnold E. |editor-last3=Rice |editor-first3=Eugene W. |editor-last4=Clesceri |editor-first4=Lenore S. |editor-last5=Franson |editor-first5=Mary Ann H. |year=2005 |publisher=American Public Health Association |isbn=978-0-87553-047-5 |id=Method 9060a. Also available on CD-ROM and [https://www.standardmethods.org/ online] by subscription}}

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).{{cite book |last1=Vogt |first1=Helmut |last2=Balej |first2=Jan |last3=Bennett |first3=John E. |last4=Wintzer |first4=Peter |last5=Sheikh |first5=Saeed Akhbar |last6=Gallone |first6=Patrizio |chapter=Chlorine Oxides and Chlorine Oxygen Acids |title=Ullmann's Encyclopedia of Industrial Chemistry |edition=7th |publisher=Wiley |year=2007 |page=2 |title-link=Ullmann's Encyclopedia of Industrial Chemistry}}{{cite web |title=Sodium hypochlorite as a disinfectant |publisher=Lenntech.com |url=https://www.lenntech.com/processes/disinfection/chemical/disinfectants-sodium-hypochlorite.htm |access-date=2011-08-07}}

:{{chem2|Cl2(g) + 2 NaOH(aq) → NaCl(aq) + NaClO(aq) + H2O}}

Hence, chlorine is simultaneously reduced and oxidized; this process is known as disproportionation.{{citation needed|date=November 2023}}

The process is also used to prepare the pentahydrate {{chem2|NaOCl*5H2O}} 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.

Another method involved the reaction of sodium carbonate ("washing soda") with chlorinated lime ("bleaching powder"), a mixture of calcium hypochlorite {{chem2|Ca(OCl)2}}, calcium chloride {{chem2|CaCl2}}, and calcium hydroxide {{chem2|Ca(OH)2}}:

:{{chem2|Na2CO3(aq) + Ca(OCl)2(aq) → CaCO3(s) + 2 NaOCl(aq)}}

:{{chem2|Na2CO3(aq) + CaCl2(aq) → CaCO3(s) + 2 NaCl(aq)}}

:{{chem2|Na2CO3(aq) + Ca(OH)2(s) → CaCO3(s) + 2 NaOH(aq)}}

This method was commonly used to produce hypochlorite solutions for use as a hospital antiseptic that was sold after World War I under the names "Eusol", an abbreviation for Edinburgh University Solution Of (chlorinated) Lime – a reference to the university's pathology department, where it was developed.{{cite encyclopedia |title=eusol |encyclopedia=Oxford English Dictionary |url=http://www.oxforddictionaries.com/definition/english/eusol |access-date=3 July 2014 |url-status=dead |archive-url=https://web.archive.org/web/20130831120343/http://oxforddictionaries.com/definition/english/eusol |archive-date=31 August 2013}}

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.{{cite web |title=Sodium Hypochlorite (Bleach) |last=May |first=Paul |publisher=University of Bristol |url=https://www.chm.bris.ac.uk/motm/bleach/bleachh.htm |access-date=13 December 2016 |url-status=live |archive-url=https://web.archive.org/web/20161213230407/http://www.chm.bris.ac.uk/motm/bleach/bleachh.htm |archive-date=13 December 2016}}{{cite web |title=How Products Are Made Volume 2 |date=May 2011 |url=http://www.madehow.com/Volume-2/Bleach.html}} The key reactions are:

:{{chem2|2 Cl− → Cl2 + 2 e−}} (at the anode)

:{{chem2|2 H2O + 2 e− → H2 + 2 -OH}} (at the cathode)

Both electric power and brine solutions 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.{{citation needed|date=November 2023}}

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 a 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.{{citation needed|date=September 2023}}

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 {{chem2|NaOCl*2H2O}} 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 filtration. 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.

The same principle was used in a 1993 patent to produce concentrated slurries of the pentahydrate {{chem2|NaClO*5H2O}}. 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.{{cite patent |inventor=Duncan BL, Ness RC |gdate=1991 |title=Process for the production of highly pure concentrated slurries of sodium hypochlorite |country=US |number=5194238}}

{{Main|Bleach}}

File:Eau-de-Javel-deutsch-1.jpg

Household bleach sold for use in laundering clothes is a 3–8% solution of sodium hypochlorite at the time of manufacture. Strength varies from one formulation to another and gradually decreases with long storage. Sodium hydroxide is usually added in small amounts to household bleach to slow down the decomposition of NaClO.

Domestic use patio blackspot remover products are ~10% solutions of sodium hypochlorite.

A 10–25% solution of sodium hypochlorite is, according to Univar's safety sheet, supplied with synonyms or trade names bleach, Hypo, Everchlor, Chloros, Hispec, Bridos, Bleacol, or Vo-redox 9110.{{cite web |title=SAFETY DATA SHEET Sodium Hypochlorite |date=9 August 2007 |publisher=Univar |url=https://www.hydrojet.ie/images/msds/sds_sodium_hypochlorite.pdf}}

A 12% solution is widely used in waterworks for the chlorination of water, and a 15% solution is more commonly{{cite book |title=Wastewater Engineering: Treatment, Disposal, & Reuse |publisher=Metcalf & Eddy, Inc |year=1991 |pages=497 |edition=3rd}} used for disinfection of wastewater in treatment plants. Sodium hypochlorite can also be used for point-of-use disinfection of drinking water,{{cite journal |title=Sodium hypochlorite dosage for household and emergency water treatment |journal=IWA Publishing |volume=16 |issue=1 |year=2018 |last=Lantagne |first=Daniele S. |url=https://iwaponline.com/jwh/article/16/1/112/37986/Sodium-hypochlorite-dosage-for-household-and}} taking 0.2–2 mg of sodium hypochlorite per liter of water.{{cite web |title=What is Chlorination? |date=27 November 2016 |url=https://www.safewater.org/fact-sheets-1/2017/1/23/what-is-chlorination}}

Dilute solutions (50 ppm to 1.5%) are found in disinfecting sprays and wipes used on hard surfaces.{{cite book |title=Elementary Food Science |last=Vieira |first=Ernest R. |publisher=Springer |year=1999 |isbn=978-0-8342-1657-0 |pages=381–382}}{{cite journal |vauthors=Wilhelm N, Kaufmann A, Blanton E, Lantagne D |title=Sodium hypochlorite dosage for household and emergency water treatment: updated recommendations |journal=Journal of Water and Health |volume=16 |issue=1 |pages=112–125 |date=February 2018 |pmid=29424725 |doi=10.2166/wh.2017.012 |doi-access=free |bibcode=2018JWH....16..112W |url=https://iwaponline.com/jwh/article/16/1/112/37986/Sodium-hypochlorite-dosage-for-household-and}}

Household bleach is, in general, a solution containing 3–8% sodium hypochlorite, by weight, and 0.01–0.05% sodium hydroxide; the sodium hydroxide is used to slow the decomposition of sodium hypochlorite into sodium chloride and sodium chlorate.Smith WT. (1994). Human and Environmental Safety of Hypochlorite. In: [https://books.google.com/books?id=Pbr2HJ1X_DkC Proceedings of the 3rd World Conference on Detergents: Global Perspectives], pp. 183–5.

Sodium hypochlorite has destaining properties. Among other applications, it can be used to remove mold stains, dental stains caused by fluorosis,{{cite journal |vauthors=Cárdenas Flores A, Flores Reyes H, Gordillo Moscoso A, Castanedo Cázares JP, Pozos Guillén A |title=Clinical efficacy of 5% sodium hypochlorite for removal of stains caused by dental fluorosis |journal=The Journal of Clinical Pediatric Dentistry |volume=33 |issue=3 |pages=187–91 |year=2009 |pmid=19476089 |doi=10.17796/jcpd.33.3.c6282t1054584157 |doi-broken-date=3 December 2024 |url=https://www.jocpd.com/articles/10.17796/jcpd.33.3.c6282t1054584157|url-access=subscription }} 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. It is also used in sodium hypochlorite washes.

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.

{{See also|Hypochlorous acid}}

Sodium hypochlorite in solution exhibits broad-spectrum anti-microbial activity and is widely used in healthcare facilities in a variety of settings.{{cite web |title=Guideline for Disinfection and Sterilization in Healthcare Facilities |vauthors=Rutala WA, Weber DJ |date=15 February 2017 |website=cdc.gov |orig-year=2008 |url=https://www.cdc.gov/infection-control/media/pdfs/guideline-disinfection-h.pdf |access-date=2024-10-30}} 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).{{cite web |title=For General Healthcare Settings in West Africa: How to Prepare and Use Chlorine Solutions |department=Ebola Hemorrhagic Fever |website=Centers for Disease Control and Prevention |url=https://www.cdc.gov/vhf/ebola/hcp/mixing-chlorine-solutions.html |access-date=2016-04-27}} It may be made by diluting household bleach as appropriate (normally 1 part bleach to 9 parts water).{{cite web |title=How to Make Strong (0.5%) Chlorine Solution from Liquid Bleach |website=Centers for Disease Control and Prevention |url=https://www.cdc.gov/vhf/ebola/pdf/cleaning-handwashing-5percent-liquid-bleach.pdf}} Such solutions have been demonstrated to inactivate both C. difficile and HPV.{{cite journal |vauthors=Meyers J, Ryndock E, Conway MJ, Meyers C, Robison R |title=Susceptibility of high-risk human papillomavirus type 16 to clinical disinfectants |journal=The Journal of Antimicrobial Chemotherapy |volume=69 |issue=6 |pages=1546–50 |date=June 2014 |pmid=24500190 |doi=10.1093/jac/dku006 |pmc=4019329}} "Weak chlorine solution" is a 0.05% solution of hypochlorite used for washing hands, but is normally prepared with calcium hypochlorite granules.

"Dakin's Solution" is a disinfectant solution containing a low concentration of sodium hypochlorite and some boric acid or sodium bicarbonate to stabilize the pH. It is effective with NaOCl concentrations as low as 0.025%.{{cite journal |vauthors=Heggers JP, Sazy JA, Stenberg BD, Strock LL, McCauley RL, Herndon DN, Robson MC |title=Bactericidal and wound-healing properties of sodium hypochlorite solutions: the 1991 Lindberg Award |journal=The Journal of Burn Care & Rehabilitation |volume=12 |issue=5 |pages=420–4 |date=1991 |pmid=1752875 |doi=10.1097/00004630-199109000-00005}}

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).21 CFR Part 178 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 before brewing 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 afterward, 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.{{cite web |title=Toilet Cleaners: Learn About Chemicals Around Your House: Pesticides: US EPA |date=9 May 2012 |publisher=United States Environmental Protection Agency |url=http://www.epa.gov/kidshometour/products/tbclean.htm}} 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.{{cite web |title=Benefits and Safety Aspects of Hypochlorite Formulated in Domestic Products |publisher=AISE – International Association for Soaps, Detergents and Maintenance Products |date=March 1997 |url=https://aise.eu/app/uploads/2023/03/AISE_hypo_intr_scientific.pdf |url-status=live |access-date=2024-10-30 |archive-url=https://web.archive.org/web/20140330021617/http://aise.eu/www-old/PDF/intr_scientific.pdf |archive-date=30 March 2014 |quote=This Support Dossier deals with information on the environmental and human safety evaluation of hypochlorite, and on its benefits as a disinfecting, deodorising, and stain removing agent.}}

Sodium hypochlorite solutions have been used to treat dilute cyanide wastewater, such as electroplating wastes. In batch treatment operations, sodium hypochlorite has been used to treat more concentrated cyanide wastes, such as silver cyanide plating solutions. Toxic cyanide is oxidized to cyanate {{chem2|OCN−}}) that is not toxic, idealized as follows:

:{{chem2|CN− + −OCl → OCN− + Cl−}}

Sodium hypochlorite is commonly used as a biocide in industrial applications to control slime and bacteria formation in water systems used at power plants, pulp and paper mills, etc., in solutions typically of 10–15% by weight.

Sodium hypochlorite is the medicament of choice due to its efficacy against pathogenic organisms and pulp digestion in endodontic therapy. Its concentration for use varies from 0.5% to 5.25%. At low concentrations it dissolves mainly necrotic tissue; at higher concentrations, it also dissolves vital tissue and additional bacterial species. One study has shown that Enterococcus faecalis was still present in the dentin after 40 minutes of exposure of 1.3% and 2.5% sodium hypochlorite, whereas 40 minutes at a concentration of 5.25% was effective in E. faecalis removal.[https://www.aae.org/specialty/wp-content/uploads/sites/2/2017/07/rootcanalirrigantsdisinfectants.pdf Root Canal Irrigants and Disinfectants]. Endodontics: Colleagues for Excellence. Published for the Dental Professional Community by the American Association of Endodontists. Winter 2011. In addition to higher concentrations of sodium hypochlorite, longer time exposure and warming the solution (60 °C) also increases its effectiveness in removing soft tissue and bacteria within the root canal chamber. 2% is a common concentration as there is less risk of an iatrogenic hypochlorite incident.{{cite book |last1=Torabinejad |first1=Mahmoud |last2=Walton |first2=Richard |title=Endodontics |edition=4th |page=265 |publisher=W.B. Saunders Company |date=2008 |series=VitalBook}} A hypochlorite incident is an immediate reaction of severe pain, followed by edema, haematoma, and ecchymosis as a consequence of the solution escaping the confines of the tooth and entering the periapical space. This may be caused by binding or excessive pressure on the irrigant syringe, or it may occur if the tooth has an unusually large apical foramen.{{cite journal |vauthors=Hülsmann M, Hahn W |title=Complications during root canal irrigation--literature review and case reports |journal=International Endodontic Journal |volume=33 |issue=3 |pages=186–93 |date=May 2000 |pmid=11307434 |doi=10.1046/j.1365-2591.2000.00303.x |url=http://endoexperience.com/documents/Complicationsduringrootcanalirrigation_literaturereviewandcasereports.pdf}}

At the various nerve agent (chemical warfare nerve gas) destruction facilities throughout the United States, 0.5-2.5% sodium hypochlorite is used to remove all traces of nerve agent or blister agent from Personal Protection Equipment after an entry is made by personnel into toxic areas.{{cite web |title=Sodium hypochlorite - Medical Countermeasure Database |author= |date=16 November 2022 |website=chemm.hhs.gov |url=https://chemm.hhs.gov/countermeasure_sodium-hypochlorite.htm |access-date=28 August 2023}}

0.5-2.5% sodium hypochlorite is also used to neutralize any accidental releases of the nerve agent in the toxic areas.{{cite journal |last1=Gold |first1=Mark |last2=Bongiovanni |first2=Rodolfo |title=Hypochlorite solution as a decontaminant in sulfur mustard contaminated skin defects in the euthymic hairless guinea pig |date=1994 |journal=Vetarinary Medicine and Surgery Branch and Basic Assessment Branch, United States Army Medical Research |volume=17 |issue=4 |pages=499–527 |pmid=7821235 |doi=10.3109/01480549409014314 |url=https://apps.dtic.mil/sti/tr/pdf/ADP008792.pdf}}

Lesser concentrations of sodium hypochlorite are used similarly in the Pollution Abatement System to ensure that no nerve agent is released into the furnace flue gas.

Dilute bleach baths have been used for decades to treat moderate to severe eczema in humans,.{{cite web |title=Bleach baths using Milton Sterilising Fluid for recurrent infected atopic eczema |last1=Pett |first1=Karen |last2=Batta |first2=Kapila |last3=Vlachou |first3=Christina |last4=Nicholls |first4=Geoff |website=eczema.org |url=http://www.eczema.org/documents/81 |url-status=dead |archive-url=https://web.archive.org/web/20131212181656/http://www.eczema.org/documents/81 |archive-date=2013-12-12}} Still, it has not been clear why they work. One of the reasons why bleach helps is that eczema can frequently result in secondary infections, especially from bacteria like Staphylococcus aureus, which makes managing it difficult. Staphylococcus aureus infection is related to the pathogenesis of eczema and AD. Bleach baths are one method for lowering the risk of staph infections in people with eczema. The antibacterial and anti-inflammatory properties of sodium hypochlorite contribute to the reduction of harmful bacteria on the skin and the reduction of inflammation, respectively.{{cite web |title=Eczema Bleach Bath: A Step-by-Step Guide and Benefits |website=skinsuperclear.com |url=https://skinsuperclear.com/eczema-bleach-bath/ |access-date=13 March 2023}} 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.{{cite web |title=Inflammatory skin damage in mice blocked by bleach solution, study finds |publisher=Stanford School of Medicine |date=15 November 2013 |last=Conger |first=Krista |url=http://med.stanford.edu/ism/2013/november/bleach.html |url-status=dead |archive-url=https://web.archive.org/web/20131207172650/http://med.stanford.edu/ism/2013/november/bleach.html |archive-date=7 December 2013}}{{cite journal |vauthors=Leung TH, Zhang LF, Wang J, Ning S, Knox SJ, Kim SK |title=Topical hypochlorite ameliorates NF-κB-mediated skin diseases in mice |journal=The Journal of Clinical Investigation |volume=123 |issue=12 |pages=5361–70 |date=December 2013 |pmid=24231355 |doi=10.1172/JCI70895 |pmc=3859383}}

Dilute sodium hypochlorite solutions (as in household bleach) are irritating to mainly the skin and respiratory tract. Short-term skin contact with household bleach may cause dryness of the skin.

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).

Sodium hypochlorite is a strong oxidizer. Oxidation reactions are corrosive. Solutions burn the skin and cause eye damage, especially when used in concentrated forms. As recognized by the NFPA, however, only solutions containing more than 40% sodium hypochlorite by weight are considered hazardous oxidizers. Solutions less than 40% are classified as a moderate oxidizing hazard (NFPA 430, 2000).

Household bleach and pool chlorinator solutions are typically stabilized by a significant concentration of lye (caustic soda, NaOH) as part of the manufacturing reaction. This additive will by itself cause caustic irritation or burns due to defatting and saponification of skin oils and destruction of tissue. The slippery feel of bleach on the skin is due to this process.

Contact of sodium hypochlorite solutions with metals may evolve flammable hydrogen gas. Containers may explode when heated due to the release of chlorine gas.(2013): "[https://www-group.slac.stanford.edu/esh/eshmanual/references/chemsafetyGuideSodiumHypochlorite.pdf Sodium Hypochlorite]" Stanford Linear Accelerator Laboratory Safe Handling Guideline, chapter 53, product 202. Accessed on 2018-06-12

Hypochlorite solutions are corrosive to common container materials such as stainless steel and aluminium. The few compatible metals include titanium (which however is not compatible with dry chlorine) and tantalum. Glass containers are safe. Some plastics and rubbers are affected too; safe choices include polyethylene (PE), high density polyethylene (HDPE, PE-HD), polypropylene (PP), some chlorinated and fluorinated polymers such as polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF); as well as ethylene propylene rubber, and Viton.

Containers must allow the venting of oxygen produced by decomposition over time, otherwise, they may burst.

Mixing bleach with some household cleaners can be hazardous.

Sodium hypochlorite solutions, such as liquid bleach, will release toxic chlorine gas when mixed with an acid, such as hydrochloric acid or vinegar.

A 2008 study indicated that sodium hypochlorite and organic chemicals (e.g., surfactants, fragrances) contained in several household cleaning products can react to generate chlorinated organic compounds.{{cite journal |vauthors=Odabasi M |title=Halogenated volatile organic compounds from the use of chlorine-bleach-containing household products |journal=Environmental Science & Technology |volume=42 |issue=5 |pages=1445–1451 |date=March 2008 |bibcode=2008EnST...42.1445O |pmid=18441786 |doi=10.1021/es702355u |url=https://coronanlm.com/pdf/TGEF_ToxicGases-fromBleach.pdf}} The study showed that indoor air concentrations significantly increase (8–52 times for chloroform and 1–1170 times for carbon tetrachloride, respectively, above baseline quantities in the household) during the use of bleach containing products.

In particular, mixing hypochlorite bleaches with amines (for example, cleaning products that contain or release ammonia, ammonium salts, urea, or related compounds and biological materials such as urine) produces chloramines.{{cite book |last1=Krieger |first1=Gary R. |last2=Sullivan |first2=John B. Jr. |title=Clinical environmental health and toxic exposures |date=2001 |publisher=Lippincott Williams & Wilkins |location=Philadelphia, Pa. |isbn=9780683080278 |page=968 |edition=2nd |url=https://books.google.com/books?id=PyUSgdZUGr4C&pg=PA968 |access-date=30 August 2016}} These gaseous products can cause acute lung injury. Chronic exposure, for example, from the air at swimming pools where chlorine is used as the disinfectant, can lead to the development of atopic asthma.{{cite journal |vauthors=Nickmilder M, Carbonnelle S, Bernard A |title=House cleaning with chlorine bleach and the risks of allergic and respiratory diseases in children |journal=Pediatric Allergy and Immunology |volume=18 |issue=1 |pages=27–35 |date=February 2007 |pmid=17295796 |doi=10.1111/j.1399-3038.2006.00487.x |s2cid=24606118}}

Bleach can react violently with hydrogen peroxide and produce oxygen gas:

:{{chem2|H2O2(aq) + NaOCl(aq) → NaCl(aq) + H2O + O2(g)}}

Explosive reactions or byproducts can also occur in industrial and laboratory settings when sodium hypochlorite is mixed with diverse organic compounds.

The UK's National Institute for Health and Care Excellence in October 2008 recommended that Dakin's solution should not be used in routine wound care.[https://www.nice.org.uk/savingsAndProductivityAndLocalPracticeResource?ci=http%3A%2F%2Fsearch.nice.org.uk%2Fusingguidance%2Fdonotdorecommendations%2Fdetail.jsp%3Faction%3Ddetails%26dndid%3D224 Do not use Eusol and gauze to manage surgical wounds that are healing by secondary intention, October 2008, NICE, London] {{webarchive|url=https://web.archive.org/web/20140714233942/https://www.nice.org.uk/savingsAndProductivityAndLocalPracticeResource?ci=http%3A%2F%2Fsearch.nice.org.uk%2Fusingguidance%2Fdonotdorecommendations%2Fdetail.jsp%3Faction%3Ddetails%26dndid%3D224 |date=14 July 2014}}.Accessed 3 July 2014.

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.ASC – PT Asahimas Chemical (2009): "[http://www.asc.co.id/uplimg/File/03%20zMSDS_NaClO_ASC%20R3.pdf Sodium hypochlorite 10%] {{Webarchive|url=https://web.archive.org/web/20180712174651/http://www.asc.co.id/uplimg/File/03%20zMSDS_NaClO_ASC%20R3.pdf |date=12 July 2018}}". Online Material Safety Data Sheet (MSDS). Accessed on 2018-06-14.

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 as during industrial use. For example, when household bleach and wastewater were mixed, 1–2% of the available chlorine was observed to form organic compounds. As of 1994, not all the byproducts had been identified, but identified compounds include chloroform and carbon tetrachloride.{{update inline|date=September 2022}} The exposure to these chemicals from use is estimated to be within occupational exposure limits.

• Calcium hypochlorite {{chem2|Ca(OCl)2}} ("bleaching powder")
• Potassium hypochlorite KOCl (the original "Javel water")
• Lithium hypochlorite LiOCl
• Milton sterilizing fluid
• Sodium hypochlorite washes
• Mixed oxidant

{{Reflist}}

{{Refbegin}}

• {{cite journal |vauthors=Jones FL |title=Chloride poisoning from mixing household cleaners |journal=JAMA |volume=222 |issue=10 |pages=1312 |date=December 1972 |pmid=4678160 |doi=10.1001/jama.222.10.1312}}
• {{cite journal |vauthors=Bonnard M, Brondeau MT, Falcy M, Jargot D, Miraval S, Protois J, Schneider O |journal=Fiche Toxicologique |volume=157 |title=Eaux et extraits de Javel Hypochlorite de sodium en solution}}

{{Refend}}

• [https://www.inchem.org/documents/icsc/icsc/eics0482.htm International Chemical Safety Card 0482] (solutions < 10% active Cl)
• [https://www.inchem.org/documents/icsc/icsc/eics1119.htm International Chemical Safety Card 1119] (solutions > 10% active Cl)
• [https://web.archive.org/web/20100428080243/http://www.inrs.fr/fichetox/ft157.html Institut national de recherche et de sécurité] (in French)
• [https://web.archive.org/web/20060112074931/http://www.hassandlass.org.uk/query/reports/2002data.pdf Home and Leisure Accident Statistics 2002] (UK RoSPA)
• [https://www.epa.gov/ground-water-and-drinking-water/emergency-disinfection-drinking-water Emergency Disinfection of Drinking Water] (United States Environmental Protection Agency)
• [https://web.archive.org/web/20051012231045/http://www-cie.iarc.fr/htdocs/monographs/vol52/01-water.htm Chlorinated Drinking Water] (IARC Monograph)
• [http://ntp.niehs.nih.gov/ntp/htdocs/LT_rpts/tr392.pdf NTP Study Report TR-392: Chlorinated & Chloraminated Water] (US NIH)
• [https://extension.okstate.edu/fact-sheets/guidelines-for-the-use-of-chlorine-bleach-as-a-sanitizer-in-food-processing-operations.html Guidelines for the Use of Chlorine Bleach as a Sanitizer in Food Processing Operations] (Oklahoma State University)

{{Antiseptics and disinfectants}}

{{Sodium compounds}}

{{Hypochlorites}}

Category:Antiseptics

Category:Bleaches

Category:Disinfectants

Category:Hypochlorites

Category:Oxidizing agents

Category:Sodium compounds

Category:Household chemicals