Bleach ou liquid bleach refers to a number of chemicals which remove color, whiten or disinfect, often by oxidation.
English name others: Chlorine bleach, Javel Water, Sodium hypochloride.

Potassium 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 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").
However, this process was not very efficient, and alternative 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 that was sold after World War I under the trade names "Eusol" and "Dakin's Solution".

Sodium hypochlorite is a chemical compound with the formula NaClO [Molar mass NaClO = 74.442 g/mol ].
It is composed of a sodium cation (Na+) and a hypochlorite anion (ClO-); it may also be viewed as the sodium salt of hypochlorous acid. When dissolved in water it is commonly known as bleach or liquid bleach, and is frequently used as a disinfectant or a bleaching agent.

greenish-yellow solid (pentahydrate)
chlorine-like and sweetish
1.11 g/cm3
Melting point
18 °C (64 °F; 291 K) pentahydrate
Boiling point
101 °C (214 °F; 374 K) (decomposes)
Solubility in water
29.3 g/100mL (0 °C)
Acidity (pKa)
> 7

Sodium hypochlorite (NaClO) 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 (see Noted, hereunder).

Cl2 + 2 NaOH >>> NaClO + NaCl + H2O

Hence, chlorine is simultaneously reduced and oxidized; this process is known as disproportionation.
Commercial solutions always contain significant amounts of sodium chloride (common salt) as the main by-product, as seen in the equation above.
The concentrations obtained, are 12.5 to 25% chlorine (in the latter case, partially precipitated NaCl and must be removed).

Parasitic reaction to slow as possible: NaClO 3 >>> NaClO 3 + 2 NaCl, that is to say, the formation of chlorates and chlorides NaClO3, this is made possible by maintaining the temperature of the environment as low as possible (do not exceed 40 ° C).

Reaction of calcium chloride on sodium carbonate:

(CaOCl2 + CaCl2) + 2 Na2CO3 >>> 2 NaClO + 2 NaCl + 2 CaCO3

(calcium carbonate CaCO3 precipitates)

The pure sodium hypochlorite in the form of solid crystals (hydrated in variable values) is of little interest due to the low stability of this substance. it is more stable in cold dilute solutions.

FRENCH SITUATION: production, about 245 million liters / year in public (which is twice the volume of household cleaners).
Every business day, using about 1 million of concentrated bleach cartons.
France is the second rank of European consumption by volume, behind Spain and ahead of Italy (about 220 million liters / year).
In addition, France is the 5th largest global consumption volume behind:

Title of chlorine (liquid bleach):
The French chlorometric degree ° Cl (definition still used primarily in French-speaking countries):
This is the oxidizing power of a liter of bleach at 20 ° C, expressed in liters of dry chlorine gas at 1 bar (1013 hPa) and at 0 ° C.
It corresponds to chlorine gas Cl2 used to make bleach.
Or at T = 20 °C, and P = 1 bar, 1 liter Cl2,3.17 g in weigh (44.7 mmol), thus

1°Cl = 3.17 g of active chlorine / liter.

(Reminder: 1 Cl = 3.32 g NaClO / liter [3.32 gL]).


Note: in some countries, Cl ° is defined as the number of liters of chlorine gas Cl2 (at 0 ° C and 760 mm Hg), contained in 1 liter of solution; So in this case ° Cl = 3.214 g active Cl2 / l.

Percent active chlorine.

Percent active chlorine is a unit of concentration used for hypochlorite-based bleaches. One gram of a 100% active chlorine bleach has the same bleaching power as one gram of chlorine. The term "active chlorine" is used because most commercial bleaches contain substantial amounts of chlorine in the form of chloride ions, which have no bleaching properties.
This definition as a bleach (Anglo-Saxon) was adopted at the European level in 1994. It reports the total amount of chlorine Cl2 used in the manufacture of bleach.
However, the% of active chlorine, for the same quality of bleach, depends on the density of the bleach which itself varies with the preparation method of the bleach.
Indeed, bleach dilution prepared by bleach at 100 ° Cl is less dense (a portion of ions Na + and Cl-was removed) a bleach prepared directly.
The chlorine term is - despite its widespread use in Europe - improper ...

Rather chemists employ the term "available chlorine".

Note also that an excess of ions HO-(5 to 12 g / l expressed as NaOH) is held in the NaClO solution in order to neutralize the influence of CO2 from the air. As a result, the pH of a concentrated bleach can be strongly basic (pH = 11.5)

It is therefore necessary to know the relationship between density and concentration to convert ° Cl%, which moreover may vary, depending on the raw materials used because there are two different materials:

The tables below, collect data for conversion between units, and allow you to perform calculations for dilute solutions.

active Cl2 (g/l)
NaClO (g/l)
NaClO (mmol/l)
1° =
NaClO (g/l)
active Cl2 (g/l)
NaClO (mmol/l)
1 =

Table (pdf, 53 KB, in French) to download (CSNEJ - 05/2010).

Commercial products.
Until 1976, the bleach was stabilized and colored orange with sodium dichromate (about 20 g per 100 liters). Currently, the commercial bleach is a clear, yellow-green, with a characteristic smell called "chlorinated" and between 1.0 and 1.2 average density.

Solutions are marketed under two main forms:

The concentrated extract at 35 ° Cl is never used pure but diluted quart (250 ml + 750 ml concentrated bleach distilée of water). This results in a bleach grading 8.75 ° Cl about.
°Cl (F)
active Cl2 (%)
active Cl2 (g/l )
NaClO (g/L)
Density (*)
Bottles of bleach
± 1040
± 11
Extract concentrated bleach
± 1157
Extract concentrated bleach
± 1216

Bleach at 35°Cl diluted ¼
± 1040
± 11
Bleach at 48°Cl diluted ¼
± 1054
(* [g/L])
(Reminder: 1 Cl = 3.32 [3.32 g / L]).

Conservation: the concentrate is stable only three months after manufacture, the solution to 9 Cl keeps much better (6-12 months). It is therefore advisable to dilute a concentrated way expiration. The both of them will keep away from light and if possible at a temperature <25 ° C.
Note: dilution in a 1.5 liter bottle, gives a solution to 6 Cl (19 g of active chlorine per liter or 1.85%).

Also note:

Properties (equimolar solution of [NaClO + NaCl], at 50 ° Cl):

Other features: :

Oxidizing properties: it is more oxidizing than its pH is low, but even at pH 14 its oxidizing power remains high (E ° = 0.88 V).
It can oxidize many toxic compounds in "harmless" compounds, such as for example:

Its bleaching action in part, due to its ability to oxidize many organic compounds.

Disinfectant properties:
These are due to the bactericidal action of hypochlorous acid which diffuses through the cell wall of bacteria destroying membrane proteins.
Furthermore, HClO acts on the metabolism of bacterial synthesis. HClO, unloaded, is nearly 100 times more bactericidal than the hypochlorite ion.

In the case of virus attack by HClO would amidated bonds of proteins.

At the request of the National Union Chamber of Bleach (Chambre Syndicale Nationale de l'Eau de Javel, CSNEJ), the Pasteur Institute of Lille in 2008 an essay based on the European standard EN 14476 to determine the virucidal activity of the water bleach to 2.6% active chlorine on the Influenza A/H5N1 virus.
The results show that the bleach has virucidal activity on avian influenza A/H5N1.
Under the following conditions:

The effective concentration is 0.10% chlorine.
This corresponds to the bleach bottle of commerce 25 times diluted about.

Chemical properties.
When a sodium hypochlorite [Na+][ClO-] solution is injected in water in pH values (5.5 to 9) normally encountered water, all or part of the ion [ClO-] is transformed into hypochlorous acid HClO :

NaClO + CO2 + H2O >>> Na+ + HCO3¯ + HClO

Note therefore that 1 millimole hypochlorite "consumes" 1 meq CO2, and generates 1 meq alkalinity (TAC), which would increase the pH slightly (some water).

Chlorinated forms depending on pH:

Cl2 + H2O <<< >>> HClO + HCl, et HClO <<< >>> ClO- + H+

Thus, sodium hypochlorite has the same actions as the chlorine gas.

 Stability :

Household bleach is, in general, a solution containing 3-8% sodium hypochlorite 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.
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 effectiveness of the bleach, owing to the increased reactivity of the molecules.
Stain removal.
Sodium hypochlorite has destaining properties.[11] Amongst other applications, it can be used to remove mold stains, dental stains caused by fluorosis,[12] and stains on crockery, especially those caused by the tannins in tea.
A weak solution of 2% 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; the chlorinated byproducts of sanitizing surfaces are also harmful. The mode of disinfectant action of sodium hypochlorite is similar to that of hypochlorous acid.
A 1-in-5 dilution of household bleach with water (1 part bleach to 4 parts water) is effective against many bacteria and some viruses, and is often the disinfectant of choice in cleaning surfaces in hospitals (primarily in the United States). The solution is corrosive and needs 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 thick so as not to drain quickly from vertical surfaces, such as the inside of a toilet bowl.
Sodium hypochlorite has deodorising properties.
Sodium hypochlorite is now used in endodontics during root canal treatments. It is the medicament of choice due to its efficacy against pathogenic organisms and pulp digestion. In previous times, Henry Drysdale Dakin's solution (0.5%) had been used. Its concentration for use in endodontics today varies from 0.5% to 5.25%. At low concentrations it will dissolve mainly necrotic tissue; whereas at higher concentrations tissue dissolution is better but it also dissolves vital tissue, a generally undesirable effect. It has been shown that clinical effectiveness does not increase conclusively for concentrations higher than 1%.
Nerve agent neutralization.
At the various nerve agent (chemical warfare nerve gas) destruction facilities throughout the United States, 50% sodium hypochlorite is used as a means of removing 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 nerve agent in the toxic areas. Lesser concentrations of sodium hypochlorite are used in similar fashion in the Pollution Abatement System to ensure that no nerve agent is released in furnace flue gas.
Reduction of skin damage.
Dilute bleach baths have been used for decades to treat moderate to severe eczema in humans,[15][16] 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 ageing 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-kB) is known to play a critical role in inflammation, ageing and response to radiation. The researchers found that if NF-kB 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.

Water treatment.
In drinking water systems, swimming pools, etc., sodium hypochlorite is widely used for chlorination. Hypochlorites are an alternative to chlorine gas, which is difficult to handle in many contexts. Also, accidents involving chlorine gas are more serious than accidents involving hypochlorites. Chlorination usually produces small quantities of harmful byproducts. Hypochlorites are very similar to chlorine gas in this regard.
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 (CNO-) that is not toxic, idealized as follows:

CN- + ClO- >>> CNO- + 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.

The following comparative table shows the characteristics of the bleach (or chlorine) and ozone :

Ozone (O3)

Specific mortality rate
bacteria: 20
virus: 1
amoebae: 0,05
duration : 45 min
bacteria : 500
virus : 5
amoebae : 0,5
duration : 4 min
Effect on NH3
very good action
no action
Removal of Fe2+, Fe3+, Mn2+
very good elimination
Reduction of taste
very efficient
Color reduction
Cost relative:

At lower concentrations lethal doses, bleach inhibits the growth of bacteria, thus protecting the drinking water during transportation by pipeline.

Sodium thiosulfate is an effective chlorine neutralizer. Rinsing with a 5 mg/L solution, followed by washing with soap and water, quickly removes chlorine odor from the hands.

Storage :

Note that sodium hypochlorite is preserved even better than the temperature is lower.

As a result of degassing of chlorine to avoid désamorçages metering pumps distribution vents are provided on the suction and discharge lines.
It can be delivered by carboys, containers or tankers.

Ecological Information: Do not allow to enter waters, waste water or soil!

Sodium hypochlorite is a strong oxidizer. Oxidation reactions are corrosive, solutions burn skin and cause eye damage, especially when used in concentrated forms. However, as recognized by the NFPA, 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).
Mixing bleach with some household cleaners can be hazardous. For example, mixing an acid cleaner with sodium hypochlorite bleach generates chlorine gas. Mixing with ammonia solutions (including urine) produces chloramines. Mixtures of other cleaning agents and or organic matter can result in a gaseous reaction that can cause acute lung injury.

NH4OH + NaClO >>> NaOH + NH2Cl + H2O

Both chlorine gas and chloramine gas are toxic. Bleach can react violently with hydrogen peroxide and produce oxygen gas:

H2O2(aq) + NaClO(aq) >>> NaCl(aq) + H2O(l) + O2(g)

It is estimated that there are about 3300 accidents needing hospital treatment caused by sodium hypochlorite solutions each year in British homes (RoSPA, 2002).

Household bleach and pool chlorinator solutions are typically stabilized by a significant concentration of lye (caustic soda, NaOH) as part of the manufacturing reaction. Skin contact will produce 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. Trichloramine, the gas that is in swimming pools can cause atopic asthma.

A recent European 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 authors suggested that using these cleaning products may significantly increase the cancer risk.

Chlorination of drinking water can oxidize organic contaminants, producing chloroform and other trihalomethanes, which are carcinogenic, and many hundreds of possible disinfection by-products, the vast majority of which are not monitored.

One major concern arising from sodium hypochlorite use is that it tends to form chlorinated organic compounds; this can occur during household storage and use as well 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. The estimated exposure to these chemicals from use is estimated to be within occupational exposure limits.

There are compounds containing hypochlorite ions in solid form.
It is primarily:

Sources (in part):
Chambre Syndicale Nationale de l'Eau de Javel (
CSNEJ, lien ), Société Française de Chimie.

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