Sodium hypochlorite

• Sodium hypochlorite
• Sodium hypochlorite solution
• Sodium Hypochlorite
• L' eau de Labarraque
• Eau de Javel
• Javelsche liquor

Yellowish substance with an unpleasant, sweet odor that is durable only in aqueous solution

Liquid

23 hPa (20 ° C)

Risk

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Sodium hypochlorite ( NaClO ) is the sodium salt of hypochlorous acid ( HClO, outdated and " hypochlorous acid "). It is a white powder which contains six moles of water of crystallization per mole of sodium hypochlorite in the normal case. The trivial name of the aqueous solution of sodium hypochlorite is Eau de Labarraque or Eau de Javel, where the term eau de Javel is not strictly correct, because this refers to a solution of potassium, possibly in a mixture with other salts such as potassium chloride. Commercially, however, no distinction is often made.

History

The name Eau de Labarraque goes back to the French chemist Antoine Germain Labarraque who sold in Paris sodium and calcium hypochlorite solutions from 1822 for disinfection purposes. The worldwide use as an antiseptic but sat down until the First World War, after the re- discovery by Henry Drysdale Dakin by (hence the name Dakin 's solution, in English ).

Extraction / representation

Sodium hypochlorite is produced by introducing chlorine gas or sodium hydroxide solution by the electrolysis of a sodium chloride solution.

This reaction causes significant technical problems. Since it is formally a hydrolysis of the chlorine acts according to

Followed by neutralization of the resulting hydrochloric acid and hypochlorous acid, is easily seen that the reaction enthalpies of these reactions lead to a strong warming, all hypochlorites are sensitive. Indeed the same chemical process is used to make chlorate, however, by reaction in the hot solution. For this reason, all technical hypochlorites contain varying, sometimes large amounts of chlorate. The reaction of hypochlorite with entstandenem in the manufacture of chlorine eventually leads to chlorate.

Use

The intended use is bleaching or disinfecting ( for example in swimming pools ). The use in swimming pools is problematic, as the amounts to be added must be sufficient to present the ammonia (or amines) to chlorinate on the stage of mono chloramine addition, since a sufficient disinfection is only ensured.

Sodium hypochlorite is also the main active ingredient of disinfecting and bleaching household cleaners. Also various mold cleaner or pipe cleaners contain this chemical. They are often advertised as " with active chlorine ".

Further sodium hypochlorite is used in dentistry. It is for example used in the treatment of bacterially infected tooth root canal in order to disinfect them.

A study by the Children's Memorial Hospital in Chicago suggests that the use of full baths with a very dilute solution (0.005 %) in patients with atopic eczema leads to a significant improvement of the complaint image.

Reaction in aqueous solution

In the aqueous state, the following equilibrium is established:

The solution reacts alkaline. Under alkaline conditions the hypochlorite anion reacts nucleophilic and discolored impurities. The result is hypochlorous acid ( HClO ), which is responsible as an oxidant for the bleaching and disinfecting effect:

Another effect resulting from the decay of hypochlorous acid to hydrochloric acid and reactive singlet oxygen, which also acts oxidizing:

Upon acidification the risk that toxic chlorine gas is generated, because the solubility of chlorine in water is low. To reduce this risk, the standard solutions contain mostly an alkaline buffer.

Safety

When dealing with sodium hypochlorite very careful. Risk of explosion from the reaction of sodium hypochlorite with a number of substances and groups of substances, including reducing agents, amines, formic acid, methanol, organic substances and some other substances. In addition, the mucous membranes resulting vapors by inhalation to draw strong.

Furthermore, sodium hypochlorite reacts with acids (eg, hydrochloric acid, nitric acid) and oxidizing agents (eg hydrogen peroxide, permanganate ) sometimes very violent evolution of heat and release of chlorine gas and / or nitrous gases.

Even by heating or sunlight may cause decomposition of the sodium hypochlorite, in which, inter alia, chlorine, hydrogen chloride, chlorine dioxide and oxygen is released. This is to take into consideration when storing the substance.