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Sodium Hypochlorite

chlorine solution bleaching gas

Sodium hypochlorite (NaOCl) is a chemical compound consisting of sodium, oxygen, and chlorine that has been used for centuries for bleaching and disinfecting. Today, sodium hypochlorite (commonly called chorine bleach) is mass produced by the chlorination of soda ash and is employed in many household products, including laundry bleaches, hard surface cleaners, mold and mildew removers, and drain cleaners.

Sodium hypochlorite is the salt formed by a negatively charged hypochlorite ion (OCl-) and a positively charged sodium ion (Na+). Pure hypochlorite is highly reactive and unstable; therefore, it is usually supplied as a dilute aqueous solution. In solution, hypochlorite eventually decomposes to yield a variety of byproducts including oxygen, chlorine gas, and salt. One of these byproducts, hypochlorous acid, is a powerful oxidizing agent (meaning it can accept electrons from other materials) that lends hypochlorite excellent bleaching and disinfecting abilities. The term "available chlorine" is often used to describe the concentration of hypochlorous acid in solution (which provides a measure of the solution's oxidative ability).

Due to its reactive nature, hypochlorite is particularly sensitive to the presence of trace metals such as copper, nickel, iron, chromium, cobalt and manganese that catalyze its decomposition. In fact, it is so reactive that it will aggressively attack many materials, including rubber, most types of fabrics, and certain plastics. Therefore, care must be taken in handling and storing hypochlorite solutions; all vessels should be glass, PVC plastic, porcelain, or glazed earthenware.

Hypochlorite was first produced in 1789 in Javelle, France, by passing chlorine gas through a solution of sodium carbonate. The resulting liquid, known as "Eau de Javelle" or "Javelle 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 mix 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.

Over the last few hundred years, one of the primary uses for sodium hypochlorite has been for the bleaching of fabrics, particularly cotton. Virgin cotton fibers are not pure white and must be processed to remove their natural coloration. Cotton bleaching has been practiced since the time of ancient the Egyptians who exposed fabric to sunlight to cause whitening. Even as late as the end of the eighteenth century, the British textile industry would bleach linen fabric by soaking it in sour milk for at least 48 hours, then exposing it to sunlight by laying out miles of treated fabrics on specially designated grasslands. In the 1800s, C. Berthellot attempted to take advantage of chlorine's bleaching ability, but, because it is a gas in its natural state, the chlorine was difficult to control. Subsequently, a process was developed to deliver chlorine as a dry powder by treating calcium carbonate with chlorine gas. However, this method of bleaching was far from ideal since it resulted in damage to the fabric wherever the concentrated hypochlorite powder came into contact with the fibers. Industrial fabric bleaching was vastly improved with the development of commercial bottled solutions of hypochlorite (also called chlorine bleach). Sodium hypochlorite gained widespread use not only as for industrial fabric treatment but also as a home laundry bleach. It is still sold today as a 5% solution in water.

Another important use for hypochlorite is as a sanitizer or disinfectant. Both of these uses rely on the hypochlorite's ability to destroy microorganisms. The same oxidative mechanism responsible for hypochlorite's bleaching ability also makes it an effective germicide. Although this mechanism was not understood at the time, hypochlorite (in the form of bleaching powder) was used as early as 1800 to counteract bad odors associated with disease. In fact, it has been said that no single element has played so important a role in combating disease over the last century as chlorine in its various forms. It should also be noted that hypochlorite is corrosive at high concentrations and was only used on the skin at very dilute levels. Its disinfectant properties have also been utilized for the sanitization of food processing equipment, particularly milking utensils used in the dairy industry. One marked advantage of hypochlorite for these applications is the fact that it, in addition to working quickly, rapidly breaks down to innocuous compounds. For this reason it is also useful in chlorination of sewage effluents and swimming pool water. Today, its primary uses are in lavatory bowl deodorizers and sanitizers.

New and improved ways to use hypochlorite are still being developed. In recent years, a number of improved bleach-containing products have been brought to market as chemists have learned to combine sodium hypochlorite with cleaning agents, thickeners and fragrance compounds to create efficacious products with improved aesthetic properties. For example, hypochlorite-based hard surface cleaners for kitchen counter tops, mold and mildew removers for showers and baths, and drain cleaners for kitchen and bathroom sinks are now commercially available.

See also Antisepsis.


Resources

Books

Chalmers, Louis. Household and Industrial Chemical Specialties. Vol. 1. Chemical Publishing Co. Inc., 1978.

Schwarcz, Leonard. Sanitary Chemicals. New York: Mac Nair-Dorland Co., 1953.


Randy Schueller

KEY TERMS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Available chlorine

—A measure of the oxidative potential of a chlorine containing solution.

Bleaching powder

—A dry bleach made by treating calcium carbonate with chlorine gas.

Chlorine

—A chemical element whose strong oxidizing abilities make it useful as a disinfectant and deodorizer.

Dakin's solution

—An aqueous solution of hypochlorite (approximately 0.5%) in water used as a hospital antiseptic.

Javelle water

—The first known production of hypochlorite which was made by passing chlorine gas through a solution of sodium carbonate.

Sodium hypochlorite

—A chemical compound consisting of sodium, oxygen and chlorine (NaOCL) which has been used for centuries for its bleaching and disinfectant properties.

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User Comments

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over 4 years ago

How is parazone prepared?

How can you have 5% parazone?

Thanks

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about 3 years ago

Dear Sir,



I have met a calculation question about titration for sodium hypochlorite.



The sample preparation: sampled 10 ml of sodium hypochlorite and dilute to 250 ml with water, then transfer 10 ml of the above solution and titrate wuth 0.1 M sodium thiosulphate VS.

the titration is consumed 12.4 ml of 0.1 M sodium thiosulphate VS, and the factor of 0.1 M sodium thiosulphate VS is 1.0043.

Density for sodium hypochlorite is 1.21



calculation as follows:



{12.4 x 1.0043 x 3.722 /((10/250)x10 x 1.21)x1000}x100 % = 9.56 %



Please make any necessary correction for the formula.



Thank!



Rola



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almost 6 years ago

Surprised at statement that hypochlorite 'rapidly breaks down into innocuous products.' Has it, then, no relation to dioxin formation? Why do so many recycled paper manufacturers go to the trouble of using a non-chlorine bleach? Is this a false selling point?

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over 2 years ago

how can I thickened bleach?what is method?

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over 2 years ago

Wanted to know exact titration method to Check Content of chlorine in Packaged water

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about 5 years ago

Is there a commercial product of dry or powdered SODIUM hypochlorite? I use regularly use calcium hypochlorite in drinking water disinfection systems in Africa but frieds tell me I can purchase powdered SODIUM hypochlorite. They tell me it dissolves much more competely in water than the powdered or granular calcium form of hypochlorite. They also tell me powdered sodium hypochlorite can can be carried safely in checked luggage on airplanes. Are my friends correct in that there is a dry formulation of socium hypochlorite?

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over 2 years ago

Sir I want to asked you that to mack solution of sodium hypo chloride for making foot dip & solution for washing the utensils in fishriese industry. So pleas tell me the actual recommended dose for for both in % and ppm both.
Regards
microbiologist.faizy@gmail.com

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over 2 years ago

Sir I want to asked you that to mack solution of sodium hypo chloride for making foot dip & solution for washing the utensils in fishriese industry. So pleas tell me the actual recommended dose for for both in % and ppm both.
Regards
microbiologist.faizy@gmail.com

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over 3 years ago

This was very helpful for doing my project!!!! Thanks!!

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about 1 year ago

we are need in chrome plating removing
with acid

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over 1 year ago

Does sodium Hypochlorite react with oxygen? If the hypochlorite is exposed to oxygen should the concentration increase or decrease. if the concentration increase, what could possibly what this happen.

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almost 2 years ago

To make NaOCl thick, manufacturer (of Domestos etc) uses fatty acids (reacts with another extraneous compound: NaOH, saponification)

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almost 2 years ago

hi..
can u tel me? how can i made sodium hypoclorite in low cost,and les of waste.

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almost 2 years ago

hi..
can u tel me? how can i made sodium hypoclorite in low cost,and les of waste.

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almost 2 years ago

hi..
can u tel me? how can i made sodium hypoclorite in low cost,and les of waste.

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almost 2 years ago

hi..
can u tel me? how can i made sodium hypoclorite in low cost,and les of waste.

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almost 2 years ago

hi..
can u tel me? how can i made sodium hypoclorite in low cost,and les of waste.

Vote down Vote up

almost 2 years ago

hi..
can u tel me? how can i made sodium hypoclorite in low cost,and les of waste.

Vote down Vote up

almost 2 years ago

hi..
can u tel me? how can i made sodium hypoclorite in low cost,and les of waste.

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almost 3 years ago

This article on hypochlorite provided me with comprehensive material for my research.
Presence of hypochlorite in biobased polymer acts as a nutrient & enhances the immunity system of crops against diseases.

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over 3 years ago

I think that chemistry is my favorite course and your job is great and I am amazed.

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over 3 years ago

I think that your job is really great
And I think that you should get some updated news

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over 3 years ago

Requierement of Sodium Hypocloride Powder

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almost 4 years ago

We use NaOCl as a disinfectant.We Alpine Fresh Water System Ltd produce and bottled pure drinking water.We use 5-gallon PC bottle for bottling before selling to customers.We use Sodium Hypochlorite to clean and disinfect returned PC bottles. We sold 1.00 million bottles of water in 2009.

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over 4 years ago

Sodium Hypochlorite is the answer to

C-DIFFICIL and BED SORES.

The hospitals wash their laundry using NaClO in HOT WATER - This is wrong.They should soak the laundry in COLD WATER. This will DISINFECT OF and CLEAN 90-% of the laundry.

Then continue their washing with only 1-HOT WATER-WASH with Na2CO3/

NaHCO3 and a Foaming agent and 2 or 3 COLD WATER rinses. The laundry is now clean