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 the production of solid stable dihydrate 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 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. from ozone and salt 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 bleach packaged for household use, with 2.6% sodium hypochlorite 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. a 12% solution is widely used in waterworks for the chlorination of water, and a 15% solution is more commonly used for disinfection of waste water in treatment plants. sodium hypochlorite can also be used for point-of-use disinfection of drinking water, taking 0.2-2 mg of sodium hypochlorite per liter of water. dilute solutions (50 ppm to 1.5%) are found in disinfecting sprays and wipes used on hard surfaces. uses bleaching 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. cleaning sodium hypochlorite has destaining properties. among other applications, it can be used to remove mold stains, dental stains caused by fluorosis, 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. disinfection sodium hypochlorite in solution exhibits broad spectrum anti-microbial activity and is widely used in healthcare facilities in a variety of settings. 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). it may be made by diluting household bleach as appropriate (normally 1 part bleach to 9 parts water). such solutions have been demonstrated to inactivate both c. difficile and hpv. "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 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%. 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). 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. 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. deodorizing sodium hypochlorite has deodorizing properties, which go hand in hand with its cleaning properties. waste water treatment sodium hypochlorite solutions have been used to treat dilute cyanide waste water, 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 (ocn−) that is not toxic, idealized as follows: 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. endodontics 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. 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. 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. nerve agent neutralization at the various nerve agent (chemical warfare nerve gas) destruction facilities throughout the united states, 50% 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. 50% sodium hypochlorite is also used to neutralize any accidental releases of the nerve agent in the toxic areas. lesser concentrations of sodium hypochlorite are used in a similar fashion in the pollution abatement system to ensure that no nerve agent is released into the furnace flue gas. reduction of skin damage dilute bleach baths have been used for decades to treat moderate to severe eczema in humans, but 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. 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. safety 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 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 skin is due to this process. storage hazards contact of sodium hypochlorite solutions with metals may evolve flammable hydrogen gas. containers may explode when heated due to release of chlorine gas. 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 venting of oxygen produced by decomposition over time, otherwise they may burst. reactions with other common products 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 volatile organic compounds (vocs). these chlorinated compounds are emitted during cleaning applications, some of which are toxic and probable human carcinogens. 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. the increase in chlorinated volatile organic compound concentrations was the lowest for plain bleach and the highest for the products in the form of "thick liquid and gel." the significant increases observed in indoor air concentrations of several chlorinated vocs (especially carbon tetrachloride and chloroform) indicate that the bleach use may be a source that could be important in terms of inhalation exposure to these compounds. the