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Sodium hypochlorite

Sodium hypochlorite is a chemical compound with the formula NaOCl. Sodium hypochlorite solution, commonly known as bleach, is frequently used as a disinfectant or a bleaching agent.


Hypochlorite was first produced in 1789 by Claude Louis Berthollet in his laboratory on the quay Javel in Paris, France, by passing chlorine gas through a solution of sodium carbonate. The resulting liquid, known as "Eau de Javel" ("Javel water"), was a weak solution of sodium hypochlorite. However, this process was not very efficient and alternate production methods were sought. One such method involved the extraction of chlorinated lime (known as bleaching powder) with sodium carbonate to yield low levels of available chlorine. This method was commonly used to produce hypochlorite solutions for use as a hospital antiseptic which was sold under the trade names "Eusol" and "Dakin's solution".

Near the end of the nineteenth century, E. S. Smith patented a method of hypochlorite production involving hydrolysis of brine to produce caustic soda and chlorine gas which then mixed to form hypochlorite. Both electric power and brine solution were in cheap supply at this time, and various enterprising marketers took advantage of this situation to satisfy the market's demand for hypochlorite. Bottled solutions of hypochlorite were sold under numerous trade names; one such early brand produced by this method was called Parozone.

Today, an improved version of this method, known as the Hooker process, is the only large scale industrial method of sodium hypochlorite production. In this process sodium hypochlorite (NaOCl) and sodium chloride (NaCl) are formed when chlorine is passed into cold and dilute sodium hydroxide solution. It 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.

Cl2 + 2 NaOH → NaCl + NaOCl + H2O

Sodium hydroxide and chlorine are commercially produced by the chloralkali process, and there is no need to isolate them to prepare sodium hypochlorite.

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

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

Sodium hypochlorite can be also made by electrolyzing saturated sodium chloride solution and the product can be tested by dropping hydrochloric acid to determine if it is successfully synthesized.

Packaging and sale

Household bleach sold for use in laundering clothes is a 3-6% solution of sodium hypochlorite at the time of manufacture. Strength varies from one formulation to another and gradually decreases with long storage.

A 12% solution is widely [http://www.awwa.org/publications/AWWAJournalArticle.cfm?itemnumber=40152&showLogin=N] used in waterworks for the chlorination of water and a 15% solution is more commonly used for disinfection of waste water in treatment plants. High-test hypochlorite (HTH) is sold for chlorination of swimming pools and contains approximately 30% calcium hypochlorite. The crystalline salt is also sold for the same use; this salt usually contains less than 50% of calcium hypochlorite. However, the level of active chlorine may be much higher.

It can also be found on store shelves in Daily Sanitizing Sprays, as the sole active ingredient at 0.0095%.


Sodium hypochlorite reacts with metals gradually, such as zinc, to produce the metal oxide or hydroxide:

NaOCl + Zn → ZnO + NaCl

It reacts with hydrochloric acid to release chlorine gas:

NaOCl + 2 HCl → Cl2 + H2O + NaCl

It reacts with other acids, such as acetic acid, to release hypochlorous acid:


It decomposes when heated or evaporated to form sodium chlorate and sodium chloride:

3 NaOCl → NaClO3 + 2 NaCl

In reaction with hydrogen peroxide it gives off molecular oxygen:

NaOCl + H2O2→ H2O + NaCl + O2↑



In household form, sodium hypochlorite is used for removal of stains from laundry. It is particularly effective on cotton fiber, which stains easily but bleaches well. Usually 50 to 250 mL of bleach per load is recommended for a standard-size washer. The properties of household bleach that make it effective for removing stains also result in cumulative damage to organic fibers such as cotton, and the useful lifespan of these materials will be shortened with regular bleaching. The sodium hydroxide (NaOH) that is also found in household bleach (as noted later) causes fiber degradation as well. It is not volatile, and residual amounts of NaOH not rinsed out will continue slowly degrading organic fibers in the presence of humidity. For these reasons, if stains are localized, spot treatments should be considered whenever possible. With safety precautions, post-treatment with vinegar (or another weak acid) will neutralize the NaOH, and volatilize the chlorine from residual hypochlorite. Old t-shirts and cotton sheets that rip easily demonstrate the costs of laundering with household bleach. Hot water increases the activity of the bleach, owing to the increased kinetic energy of the molecules.


A weak solution of 1% household bleach in warm water is used to sanitize smooth surfaces prior to brewing of beer or wine. Surfaces must be rinsed to avoid imparting flavors to the brew; these chlorinated byproducts of sanitizing surfaces are also harmful.

US Government regulations (21 CFR Part 178) 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

Sodium superoxide

Sodium superoxide is the inorganic compound with the formulaNaO2. This yellow-orange solid is a salt of the superoxide anion. It is an intermediate in the oxidation of sodium by oxygen.

NaO2 is prepared by treating sodium peroxide with oxygen at high pressures:

Na2O2 + O2→ 2 NaO2

It can also be prepared by careful oxygenation of a solution of sodium in ammonia:

Na + O2→ NaO2

The product is paramagnetic, as expected for a salt of the O2−anion. It hydrolyses readily to give a mixture of sodium hydroxide and hydrogen peroxide, oxygen may also be evolved.. It crystallizes in the NaCl motif.

Hypochlorous acid

Hypochlorous acid is a weak acid with the chemical formula HClO. In the swimming pool industry, hypochlorous acid is referred to as HOCl. It forms when chlorine dissolves in water. It cannot be isolated in pure form due to rapid equilibration with its precursor (see below). HClO is an oxidizer, and in its sodium form Sodium hypochlorite, NaClO, or its calcium form Calcium hypochlorite, is used as a bleach, a deodorant, and a disinfectant.


In organic synthesis, HCIO converts alkenes to chlorohydrins.

In biology, hypochlorous acid is generated in activated neutrophils by myeloperoxidase-mediated peroxidation of chloride ions, and contributes to the destruction of bacteria.

In water treatment, hypochlorous acid is the active sanitizer in hypochlorite-based products (e.g. used in swimming pools).

In food service and water distribution, specialized equipment to generate weak solutions of HOCl from water and salt is sometimes used to generate adequate quantities of safe (unstable) disinfectant to treat food preparation surfaces and water supplies.

Formation, stablity and reactions

Addition of chlorine to water gives both hydrochloric acid (HCl) and hypochlorous acid:

Cl2 + H2O HClO + HCl

When acids are added to aqueous salts of hypochlorous acid (such as sodium hypochlorite in commercial bleach solution) this reaction is driven to the left, and chlorine gas is evolved. Thus, the formation of stable hypochlorite bleaches is facilitated by dissolving chlorine gas into basic water solutions, such as sodium hydroxide.

The acid can also be prepared by dissolving dichlorine monoxide in water; under standard aqueous conditions anhydrous Hypochlorous acid is impossible to prepare due to the readily reversible equilibrium between it and its anhydride:

2HOCl Cl2O + H2O K(0°C) =3.55x10-3dm3mol-1

The presence of light or transition metal oxides of copper, nickel or cobalt accelerates the exothermic decomposition into hydrochloric acid and oxygen:

2Cl2 + 2H2O → 4HCl + O2

Chemical reactions

In aqueous solution, hypochlorous acid partially dissociates into the anion hypochlorite OCl−:

HClO OCl− + H+

Salts of hypochlorous acid are called hypochlorites. One of the best-known hypochlorites is NaClO, the active ingredient in bleach.

HClO is a stronger oxidant than chlorine under standard conditions.

2HClO(aq) + 2 + 2 Cl2(g) + 2 E=+1.63V

HClO reacts with HCl to form chlorine gas:

HClO + HCl → H2O + Cl2

Reactivity of HClO with biomolecules

Hypochlorous acid reacts with a wide variety of biomolecules including DNA, RNA, fatty acid groups, cholesterol and proteins.

Reaction with protein sulfhydryl groups

Knox et al. first noted that HClO is a sulfhydryl inhibitor that, in sufficient quantity, could completely inactivate proteins containing sulfhydryl groups. This is because HClO oxidises sulfhydryl groups, leading to the formation of disulfide bonds that can result in crosslinking of proteins. The HClO mechanism of sulfhydryl oxidation is similar to that of chloramine, and may only be bacteriostatic, because, once the residual chlorine is dissipated, some sulfhydryl function can be restored. One sulfhydryl-containing amino acid can scavenge up to four molecules of HOCl. Consistent with this, it has been proposed that sulfhydryl groups of sulfur-containing amino acids can be oxidized a total of three times by three HClO molecules, with the fourth reacting with the α-amino group. The first reaction yields sulfenic acid (R-SOH) then sulfinic acid (R-SO2H) and finally R-SO3H. Each of those intermediates can also condense with another sulfhydryl group, causing cross-linking and aggregation of proteins. Sulfinic acid and R-SO3H derivatives are produced only at high molar excesses of HClO, and disulfides are formed primarily at bacteriocidal levels. Disulfide bonds can also be oxidized by HClO to sulfinic acid. Because the oxidation of sulfhydryls and disulfides evolves hydrochloric acid, this process results in the depletion HClO.

Reaction with protein amino groups

Hypochlorous acid reacts readily with amino acids that have amino group side-chains, with the chlorine from HClO displacing a hydrogen, resulting in an organic chloramine. Chlorinated amino acids rapidly decompose, but From Yahoo Answers

Question:What are the advantages and disadvantages of each for disinfecting minor skin abrasions etc.?

Answers:Bobcatt is correct. Sodium hypochlorite (i.e., Clorox or "bleach") is not intended for use on skin, even if it's heavily diluted with water. The reason your skin feels slippery when you spill chlorine bleach on it is that, simply put, it is destroying your skin cells. Hydrogen peroxide bubbles not because it's killing germs. It bubbles in response to contact with catalase, which is a substance in blood and cells. You can put peroxide on something like a cut-up vegetable and it fill foam, because that cut-up vegetable's cells are exposed. Hydrogen peroxide actually isn't a very effective antiseptic, and it shouldn't be used on puncture or deep wounds as it can destroy the tissues and, in certain extreme circumstances, get into the bloodstream and cause problems. The best wah to deal with a minor skin abrasion? Warm soap and water, then an antibiotic ointment and a bandage.

Question:I need to dissolve organic matter in soil and leave the clay, which I was told could be done with hydrogen peroxide. How does this work? Does the H2O2 release CO2 or H2 gas, and what exactly is reacted? This isn't necessary, but if someone could explain the reaction between sodium acetate and carbonates I would also appreciate it. I'd assume that the hydrogen from acetic acid would attack the carbonyl group of the carbonate ion, releasing CO2.

Answers:Hydrogen peroxide is an extremely strong oxidizing agent -- and probably will not attack the clays unlike some oxidizing mineral acids. You might speed up the process using UV -- a 450 W mercury vapor lamp seems to be the method of choice. The organic material is primarily composed of carbon-carbon bonded chains with hydrogen bonded to the carbons. In oxidation, the C-C and C-H bonds are broken and C-O and H-O bonds formed. It is the same reaction as combustion (burning) so the organic materials are freed as CO2 and H2O. Oxidation can be explosive if H2O2 is at high concentration and I expect that you will only be able to get a dilute solution in water. You will need a lot and the reaction is slower in dilute solutions. Consider humic acid which has the average formula C187H186O89N9S which is already oxygen rich. To oxidize that to 187CO2 + 93H2O + 9NO2 + SO2 requires 199O2 (extra to what is in the humic acid). That humic acid has a formula weight of 4012 g which would require 13.5 kg of pure H2O2. As an approximation, then, you will need three times (by mass) as much pure H2O2 as you have organic materials and you can buy 10% H2O2 solutions I think so you will need a lot more. Your second question has an internal contradiction. Acetic acid does react with carbonates and free up CO2 from the carbonate (not carbonyl) group so that the metal forms an acetate (replacing the hydrogen in the original acid), for example sodium acetate. But you ask what is the reaction between sodium acetate and carbonates. I assume that is a typo.

Question:Would sodium hydroxide just be added to the mixture to make the mixture more basic during this lab? and also, what would happen in my analysis if the methylene chloride wasn't thoroughly dry?

Answers:When the Alcohol loses the Hydrogen it forms a double bond with the carbon to make the Ketone, so that Carbon also needs to lose a Hydrogen. The Hypochlorite is an anion which keeps some Hydrogens protonized in the reaction, allowing the reaction to move forward. I don't fully comprehend the experiment based on what you wrote. Water would drive the reaction back, since it is a product.

Question:What kind of chemical reactions can I make with 3% Hydrogen Peroxide? I need to make chemical reactions with 3%hydrogen peroxide. What chemicals can i mix with it?

Answers:bvlgarifitch92, Two easy ones (do it with pipettes of the peroxide, since it's pretty reactive: Drip it on a potato; it should fizz due to the decomposition of the peroxide by catalase in the potato; Drip it into a solution of bleach (sodium hypochlorite); it should produce bubbles due to the reaction that produces oxygen gas. Drip it onto a new (shiny) penny; the penny should tarnish due to oxidation of the copper. A crowd favorite: the iodine clock (see link below) I'll try to think of more (hope this is a good start)!

From Youtube

30% Hydrogen Peroxide Decompositon :Decomposition of 30% Hydrogen Peroxide with Alconox and sodium iodide.

How To Make Chlorine Gas (By Reacting Sodium Hypochlorite/Hydrogen Chloride) :A demonstration of the reaction of Sodium Hypochlorite(Bleach) and Hydrogen Chloride(Toilet Cleaner). Bleach clearly says on the lable NOT to mix with any other cleaning products so DONT.