Mon compte

connexion

inscription

   Publicité ▼


 » 
allemand anglais arabe bulgare chinois coréen croate danois espagnol espéranto estonien finnois français grec hébreu hindi hongrois islandais indonésien italien japonais letton lituanien malgache néerlandais norvégien persan polonais portugais roumain russe serbe slovaque slovène suédois tchèque thai turc vietnamien
allemand anglais arabe bulgare chinois coréen croate danois espagnol espéranto estonien finnois français grec hébreu hindi hongrois islandais indonésien italien japonais letton lituanien malgache néerlandais norvégien persan polonais portugais roumain russe serbe slovaque slovène suédois tchèque thai turc vietnamien

définition - sodium hypochlorite

sodium hypochlorite (n.)

1.an unstable salt (NaOCl) used as a bleaching agent and disinfectant

Sodium Hypochlorite (n.)

1.(MeSH)It is used as an oxidizing and bleaching agent and as a disinfectant. (From Grant&Hackh's Chemical Dictionary, 5th ed)

   Publicité ▼

définition (complément)

voir la définition de Wikipedia

synonymes - sodium hypochlorite

Sodium Hypochlorite (n.) (MeSH)

Antiformin  (MeSH), Clorox  (MeSH), Sodium Hypochlorite (Solution)  (MeSH)

sodium hypochlorite (n.)

bleach

   Publicité ▼

dictionnaire analogique



Wikipedia

Sodium hypochlorite

                   
Sodium hypochlorite
Identifiers
CAS number 7681-52-9 YesY
PubChem 23665760
ChemSpider 22756 YesY
UNII DY38VHM5OD YesY
EC number 231-668-3
UN number 1791
KEGG D01711 YesY
RTECS number NH3486300
ATC code D08AX07
Jmol-3D images Image 1
Properties
Molecular formula NaOCl
Molar mass 74.442 g/mol
Appearance greenish-yellow solid
Odor disagreeable and sweetish
Density 1.11 g/cm3
Melting point

18 °C, 291 K, 64 °F (pentahydrate)

Boiling point

101 °C, 374 K, 214 °F (decomp.)

Solubility in water 29.3 g/100mL (0 °C)
Acidity (pKa) >7
Hazards
MSDS ICSC 1119 (solution, >10% active chlorine)
ICSC 0482 (solution, <10% active chlorine)
EU Index 017-011-00-1
EU classification Corrosive (C)
Dangerous for the environment (N)
R-phrases R31, R34, R50
S-phrases (S1/2), S28, S45, S50, S61
NFPA 704
NFPA 704.svg
0
2
1
OX
Related compounds
Other anions Sodium chloride
Sodium chlorite
Sodium chlorate
Sodium perchlorate
Other cations Lithium hypochlorite
Calcium hypochlorite
Related compounds Hypochlorous acid
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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

Contents

  Production

Sodium 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 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".

Near the end of the nineteenth century, E. S. Smith patented a method of sodium hypochlorite production involving electrolysis of brine to produce sodium hydroxide and chlorine gas, which then mixed to form sodium hypochlorite.[1] This is known as the chloralkali process. Both electric power and brine solution were in cheap supply at the time, and various enterprising marketers took advantage of the situation to satisfy the market's demand for sodium hypochlorite. Bottled solutions of sodium hypochlorite were sold under numerous trade names.

Today, an improved version of this method, known as the Hooker process, is the only large scale industrial method of sodium hypochlorite production. In the process, 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.

Cl2 + 2 NaOH → NaCl + NaClO + H2O

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.

  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 used in waterworks for the chlorination of water, and a 15% solution is more commonly[2] used for disinfection of waste water in treatment plants. Sodium hypochlorite can also be used for point-of-use disinfection of drinking water.[3]

Milder solutions (50 ppm to 1.5%) are found in disinfecting sprays and wipes used on hard surfaces.[4][5]

  Reactions

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

NaClO + Zn → ZnO + NaCl

It reacts with hydrochloric acid to release chlorine gas:

NaClO + 2 HCl → Cl2 + H2O + NaCl

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

NaClO + CH3COOH → HClO + CH3COONa

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

3 NaClO → NaClO3 + 2 NaCl

In reaction with hydrogen peroxide it gives off molecular oxygen:

NaClO + H2O2 → H2O + NaCl + O2

When dissolved in a solution of water, it will slowly decompose, releasing chlorine, oxygen, and sodium hydroxide.

4 NaClO + 2 H2O → 4 NaOH + 2 Cl2 + O2

  Uses

  Bleaching

Household bleach is, in general, a solution containing 4-6% sodium hypochlorite and 0.01-0.05% sodium hydroxide; the sodium hydroxide is used to delay the breakdown of sodium hypochlorite into sodium chloride and sodium chlorate.[6]

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.

  Disinfection

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; 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 (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 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. Even "scientific-grade", commercially produced disinfection solutions such as Virocidin-X usually have sodium hypochlorite as their sole active ingredient, though they also contain surfactants (to prevent beading) and fragrances (to conceal the bleach smell).[7]

  Water treatment

For shock chlorination of wells or water systems, a 3% solution of household bleach is used. For larger systems, sodium hypochlorite is more practical because lower rates can be used. The alkalinity of the sodium hypochlorite solution also causes the precipitation of minerals such as calcium carbonate, so that the shock chlorination is often accompanied by a clogging effect. The precipitate also preserves bacteria, making this practice somewhat less effective.

Sodium hypochlorite has been used for the disinfection of drinking water. A concentration equivalent to about 1 liter of household bleach per 4000 liters of water is used. The exact amount required depends on the water chemistry, temperature, contact time, and presence or absence of sediment. In large-scale applications, residual chlorine is measured to titrate the proper dosing rate. For emergency disinfection, the United States Environmental Protection Agency recommends the use of 2 drops of 4% to 6%[8] household bleach per litre of water. If the treated water does not smell of bleach, 2 more drops are to be added.

Many who would prefer to store drinking water on a long term basis for emergency use should consider following the same treatment protocol during the storage process (and not when the time comes to access the water); typically using the 'additional' treatment rate of approximately 15 drops per gallon of water (~1 spoon full per 7 gallons of water) unless the water is from a municipality and is known to be free of excessive contaminants and already contains a certain amount of sodium hypochlorite. Note that you should confirm that the water has a bleach scent after sitting for half an hour. Additionally, dumping the water and replacing it every 3~5 years is recommended. Washing out the food grade containers (usually made of polyethylene) during this time is encouraged by using warm soapy water or alternatively a solution of water with heavy concentration of bleach (10x 'additional' rate) followed by rinsing with clean water.

The use of chlorine-based disinfectants in domestic water, although widespread, has led to some controversy due to the formation of small quantities of harmful byproducts such as chloroform.

An alkaline solution (pH 11.0) of sodium hypochlorite is used to treat dilute (< 1 g/L) cyanide wastewater, e.g., rinsewater from an electroplating shop. In batch treatment operations, sodium hypochlorite has been used to treat more concentrated cyanide wastes, such as silver cyanide plating solutions. A well-mixed solution is fully treated when an excess of chlorine is detected.

  Endodontics

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%.[9]

  Oxidation

Household bleach, with a phase-transfer catalyst, has been reported to oxidize alcohols to the corresponding carbonyl compound.[10]

  Nerve Agent Neutralization

At the various nerve agent 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 PPE (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 PAS (Pollution Abatement System) to ensure that no nerve agent is released in furnace flue gas.

  Mechanism of disinfectant action

See Hypochlorous acid

  Safety

Sodium hypochlorite is a strong oxidizer. Oxidation reactions are corrosive, solutions burn skin and cause eye damage, in particular, 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).

Chlorination of drinking water can oxidize organic contaminants, producing trihalomethanes (also called haloforms), which are carcinogenic.

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. [11]

Sodium thiosulfate (thio) 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.

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. [12]

NH4OH + NaClO → NaOH + NH2Cl + H2O

Both chlorine gas and chloramine gas are toxic. Bleach can react violently with hydrogen peroxide and produce oxygen gas:[13]

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).

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.[6] For example, when household bleach and wastewater were mixed, 1-2% of the available chlorine was observed to form organic compounds.[6] As of 1994, not all the byproducts had been identified, but identified compounds include chloroform and carbon tetrachloride.[6] The estimated exposure to these chemicals from use is estimated to be within occupational exposure limits.[6]

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).[14] 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. While the authors suggested that using these cleaning products may significantly increase the cancer risk,[15] this conclusion appears to be hypothetical:


  • The highest level cited for concentration of carbon tetrachloride (seemingly of highest concern) is 459 micrograms per cubic meter, translating to 0.073 ppm (part per million), or 73 ppb (part per billion). The OSHA-allowable time-weighted average concentration over an eight-hour period is 10 ppm,[16] almost 140 times higher;
  • The OSHA highest allowable peak concentration (5-minute exposure for five minutes in a 4-hour period) is 200 ppm,[16] twice as high as the reported highest peak level (from the headspace of a bottle of a sample of bleach plus detergent).

Further studies of the use of these products and other possible exposure routes (i.e., dermal) may reveal other risks. Though the author further cited ozone depletion greenhouse effects for these gases, the very low amount of such gases, generated as prescribed, should minimize their contribution relative to other sources.


A study on housewives showed that exposure to common household cleaning products with sodium hypochlorite can cause Reactive Airway Dysfunction Syndrome (RADS). RADS contains "asthma-like symptoms" and its severity depends on exposure and environmental factors. The long term effects have not been recorded. Due to the onset of RADS, caution should be emphasized when using bleach and other chemicals. [17]


  References

  1. ^ "How Products Are Made Volume 2". may 2011. http://www.madehow.com/Volume-2/Bleach.html. 
  2. ^ Metcalf & Eddy, Inc (1991). Wastewater Engineering: Treatment, Disposal, & Reuse 3rd Edition; pg 497
  3. ^ Daniele S. Lantagne (2008). "Sodium hypochlorite dosage for household and emergency water treatment". E-Journal AWWA 100 (8). http://www.awwa.org/publications/AWWAJournalArticle.cfm?itemnumber=40152&showLogin=N. 
  4. ^ Ernest R. Vieira, Elementary Food Science, pp. 381-382, Springer, 1999 ISBN 0834216574.
  5. ^ Lynn R. Marotz, Health, Safety, and Nutrition for the Young Child, pp. 126-127, Cengage Learning, 2011 ISBN 1111298378.
  6. ^ a b c d e Smith WT. (1994). Human and Environmental Safety of Hypochlorite. In: Proceedings of the 3rd World Conference on Detergents: Global Perspectives, pp. 183-5.
  7. ^ http://www.kamscientific.com/
  8. ^ http://water.epa.gov/drink/emerprep/emergencydisinfection.cfm
  9. ^ Zehnder M et al. (2002). "Tissue dissolving capacity and antibacterial effect of buffered and unbuffered hypochlorite solutions". Oral Surg Oral Med Oral Pathol Oral Radio Endodon 94 (6): 756–62. DOI:10.1067/moe.2002.128961. PMID 12464903. 
  10. ^ G. A. Mirafzal and A. M. Lozeva (1998). "Phase transfer catalyzed oxidation of alcohols with sodium hypochlorite". Tetrahedron Letters 39 (40): 7263–7266. DOI:10.1016/S0040-4039(98)01584-6. 
  11. ^ http://web.ebscohost.com.lp.hscl.ufl.edu/ehost/pdfviewer/pdfviewer?sid=4f22085a-4990-46a5-801d-8a6b4687bc63%40sessionmgr11&vid=2&hid=14
  12. ^ http://web.ebscohost.com.lp.hscl.ufl.edu/ehost/pdfviewer/pdfviewer?sid=4f22085a-4990-46a5-801d-8a6b4687bc63%40sessionmgr11&vid=2&hid=14
  13. ^ "Hydrogen Peroxide + Bleach Explanation". http://library.thinkquest.org/3347/h2o2+bleach4.html. Retrieved 13 December 2008. 
  14. ^ Odabasi, M., “Halogenated Volatile Organic Compounds from the Use of Chlorine-Bleach- Containing Household Products”, Environmental Science & Technology 42, 1445-1451, (2008). Available at: http://pubs.acs.org/journals/esthag/
  15. ^ Odabasi, M., “Halogenated Volatile Organic Compounds from the Use of Chlorine-Bleach- Containing Household Products, Slide presentation (2008). Available at: http://www.slideworld.org/ViewSlides.aspx?URL=5092
  16. ^ a b http://www.osha.gov/dts/chemicalsampling/data/CH_225800.html
  17. ^ https://web.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=c1a81838-06a0-4325-a23b-bbde1db31e3e%40sessionmgr13&vid=5&hid=14

  Bibliography

  • Jones, F.-L. (1972). "Chlorine poisoning from mixing household cleaners". J. Am. Med. Assoc. 222 (10): 1312. DOI:10.1001/jama.222.10.1312. 
  • Institut National de Recherche et de Sécurité. (2004). "Eaux et extraits de Javel. Hypochlorite de sodium en solution". Fiche toxicologique n° 157, Paris.

  External links

   
               

 

Toutes les traductions de sodium hypochlorite


Contenu de sensagent

  • définitions
  • synonymes
  • antonymes
  • encyclopédie

  • definition
  • synonym

   Publicité ▼

dictionnaire et traducteur pour sites web

Alexandria

Une fenêtre (pop-into) d'information (contenu principal de Sensagent) est invoquée un double-clic sur n'importe quel mot de votre page web. LA fenêtre fournit des explications et des traductions contextuelles, c'est-à-dire sans obliger votre visiteur à quitter votre page web !

Essayer ici, télécharger le code;

SensagentBox

Avec la boîte de recherches Sensagent, les visiteurs de votre site peuvent également accéder à une information de référence pertinente parmi plus de 5 millions de pages web indexées sur Sensagent.com. Vous pouvez Choisir la taille qui convient le mieux à votre site et adapter la charte graphique.

Solution commerce électronique

Augmenter le contenu de votre site

Ajouter de nouveaux contenus Add à votre site depuis Sensagent par XML.

Parcourir les produits et les annonces

Obtenir des informations en XML pour filtrer le meilleur contenu.

Indexer des images et définir des méta-données

Fixer la signification de chaque méta-donnée (multilingue).


Renseignements suite à un email de description de votre projet.

Jeux de lettres

Les jeux de lettre français sont :
○   Anagrammes
○   jokers, mots-croisés
○   Lettris
○   Boggle.

Lettris

Lettris est un jeu de lettres gravitationnelles proche de Tetris. Chaque lettre qui apparaît descend ; il faut placer les lettres de telle manière que des mots se forment (gauche, droit, haut et bas) et que de la place soit libérée.

boggle

Il s'agit en 3 minutes de trouver le plus grand nombre de mots possibles de trois lettres et plus dans une grille de 16 lettres. Il est aussi possible de jouer avec la grille de 25 cases. Les lettres doivent être adjacentes et les mots les plus longs sont les meilleurs. Participer au concours et enregistrer votre nom dans la liste de meilleurs joueurs ! Jouer

Dictionnaire de la langue française
Principales Références

La plupart des définitions du français sont proposées par SenseGates et comportent un approfondissement avec Littré et plusieurs auteurs techniques spécialisés.
Le dictionnaire des synonymes est surtout dérivé du dictionnaire intégral (TID).
L'encyclopédie française bénéficie de la licence Wikipedia (GNU).

Copyright

Les jeux de lettres anagramme, mot-croisé, joker, Lettris et Boggle sont proposés par Memodata.
Le service web Alexandria est motorisé par Memodata pour faciliter les recherches sur Ebay.
La SensagentBox est offerte par sensAgent.

Traduction

Changer la langue cible pour obtenir des traductions.
Astuce: parcourir les champs sémantiques du dictionnaire analogique en plusieurs langues pour mieux apprendre avec sensagent.

 

7824 visiteurs en ligne

calculé en 0,141s

Je voudrais signaler :
section :
une faute d'orthographe ou de grammaire
un contenu abusif (raciste, pornographique, diffamatoire)
une violation de copyright
une erreur
un manque
autre
merci de préciser :