Bleach: Difference between revisions

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High levels of absorbable [[organic halide]]s (AOX) can be found during reaction of sodium hypochlorite and soils, including [[carbon tetrachloride]], [[trihalomethanes]] (THM, such as [[chloroform]]), and [[trihaloacetic acid]] (THAA, in this case [[trichloroacetic acid]]). Most AOX go into the sewer with wash water.
 
High levels of absorbable [[organic halide]]s (AOX) can be found during reaction of sodium hypochlorite and soils, including [[carbon tetrachloride]], [[trihalomethanes]] (THM, such as [[chloroform]]), and [[trihaloacetic acid]] (THAA, in this case [[trichloroacetic acid]]). Most AOX go into the sewer with wash water.
   
===Chemical interactions===
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NICK AND DUSTIN WERE HERE
[[Hypochlorite]] and [[chlorine]] are in [[chemical equilibrium|equilibrium]] in water; the position of the equilibrium is pH dependent and low pH (acidic) favors chlorine,<ref name="c&w">{{cite book |last=Cotton |first=F.A |authorlink= |coauthors=G. Wilkinson |title=Advanced Inorganic Chemistry |year=1972 |publisher=John Wiley and Sons Inc |location= |isbn=0-471-17560-9 }}</ref>
 
 
Cl<sub>2</sub> + H<sub>2</sub>O <math>\rightleftharpoons</math> H<sup>+</sup> + Cl<sup>-</sup> + HClO
 
 
[[Chlorine]] is a respiratory [[Irritant (biology)|irritant]] that attacks [[mucous membrane]]s and [[burn (injury)|burns]] the skin. As little as 3.53 [[parts per million|ppm]] can be detected as an odor, and 1000 [[parts per million|ppm]] is likely to be fatal after a few deep breaths. Exposure to chlorine has been limited to 0.5 [[parts per million|ppm]] (8-hour time-weighted average—38 hour week) by [[Occupational Safety and Health Administration|OSHA]] in the U.S.<ref>{{cite web|url=http://www.osha.gov/SLTC/healthguidelines/chlorine and peroxide/recognition.html| title=OSHA -- Chlorine| work=OSHA| year=2007| accessdate=2007-08-26|author=Occupational Safety & Health Administration}}</ref>
 
 
Sodium hypochlorite and [[ammonia]] react to form a number of products, depending on the temperature, concentration, and how they are mixed.<ref>{{Cite journal | last =Rizk-Ouaini | first =Rosette | author-link = | last2 =Ferriol, Michel; Gazet, Josette; Saugier-Cohen Adad, Marie Therese | first2 = | author2-link = | title =Oxidation reaction of ammonia with sodium hypochlorite. Production and degradation reactions of chloramines. | journal =Bulletin de la Societe Chimique de France
 
| volume =4 | issue = | pages =512–21 | year =1986
 
| url = | doi = | id = | postscript =<!--None--> }}</ref> The main reaction is chlorination of ammonia, first giving [[chloramine]] (NH<sub>2</sub>Cl), then [[dichloramine]] (NHCl<sub>2</sub>) and finally [[nitrogen trichloride]] (NCl<sub>3</sub>). These materials are very irritating to the [[eye]]s and [[lung]]s and are toxic above certain concentrations.
 
 
NH<sub>3</sub> + NaOCl → NaOH + NH<sub>2</sub>Cl
 
 
NH<sub>2</sub>Cl + NaOCl → NaOH + NHCl<sub>2</sub>
 
 
NHCl<sub>2</sub> + NaOCl → NaOH + NCl<sub>3</sub>
 
 
Additional reactions produce [[hydrazine]], in a variation of the [[Olin Raschig process]].
 
 
NH<sub>3</sub> + NH<sub>2</sub>Cl + NaOH → N<sub>2</sub>H<sub>4</sub> + NaCl + H<sub>2</sub>O
 
 
The hydrazine generated can further react with the [[monochloramine]] in an [[exothermic]] reaction:<ref name="c&w"/>
 
 
2 NH<sub>2</sub>Cl + N<sub>2</sub>H<sub>4</sub> → 2 NH<sub>4</sub>Cl + N<sub>2</sub>
 
 
Industrial bleaching agents can also be sources of concern. For example, the use of elemental chlorine in the [[bleaching of wood pulp]] produces [[organochlorine]]s and [[persistent organic pollutant]]s, including [[Polychlorinated dibenzodioxins|dioxin]]s. According to an industry group, the use of [[chlorine dioxide]] in these processes has reduced the dioxin generation to under detectable levels.<ref>{{cite web |url=http://www.aet.org/epp/ecf_brochure.pdf |title=ECF: The Sustainable Technology |accessdate=2007-09-19 |last= |first= |coauthors= |date= |work= |publisher=Alliance for Environmental Technology}}</ref> However, respiratory risk from chlorine and highly toxic chlorinated byproducts still exists.
 
 
A recent European study indicated that sodium hypochlorite and organic chemicals (e.g., [[surfactant]]s, [[fragrance]]s) contained in several household cleaning products can react to generate chlorinated [[volatile organic compound]]s (VOCs).<ref>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/</ref> These chlorinated compounds are emitted during cleaning applications, some of which are toxic and probable human [[carcinogen]]s. 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,<ref>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</ref> 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 [[Occupational Safety and Health Administration|OSHA]]-allowable time-weighted average concentration over an eight-hour period is 10 ppm,<ref name="OSHA_CCl4">{{cite web|url=http://www.osha.gov/dts/chemicalsampling/data/CH_225800.html |title=Chemical Sampling Information: Carbon Tetrachloride |publisher=Osha.gov |date=2004-06-16 |accessdate=2009-12-04}}</ref> almost 140 times higher;
 
:* The [[Occupational Safety and Health Administration|OSHA]] highest allowable peak concentration (5 minute exposure for five minutes in a 4-hour period) is 200 ppm,<ref name="OSHA_CCl4"/> 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 effect]]s for these gases, the very low amount of such gases, generated as prescribed, should minimize their contribution relative to other sources.
 
   
 
== Dilution ==
 
== Dilution ==

Revision as of 09:11, 25 July 2010

Template:Two other uses

File:Clorox Bleach Bottle.jpg
Commercial sodium hypochlorite bleach.

A bleach is a chemical that removes colors or whitens, often via oxidation. Common chemical bleaches include household chlorine bleach, a solution of approximately 3–6% sodium hypochlorite (NaClO), and oxygen bleach, which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate, sodium percarbonate, sodium persulfate, tetrasodium pyrophosphate, or urea peroxide together with catalysts and activators, e.g., tetraacetylethylenediamine and/or sodium nonanoyloxybenzenesulfonate. Bleaching powder is calcium hypochlorite.

Many bleaches have strong bactericidal properties, and are used for disinfecting and sterilizing.

Other types of bleaches

Chlorine dioxide is used for the bleaching of wood pulp, fats and oils, cellulose, flour, textiles, beeswax, skin, and in a number of other industries.

In the food industry, some organic peroxides (benzoyl peroxide, etc.) and other agents (e.g., bromates) are used as flour bleaching and maturing agents.

Peracetic acid and ozone are used in the manufacture of paper products, especially newsprint and white Kraft paper.[1]

Two-part bleaches are utilized in the whitening of wood, especially oak.

Environmental impact

Bleach is highly toxic to fish and invertebrates. In confined spaces, fish will attempt to swim away from the source.

High levels of absorbable organic halides (AOX) can be found during reaction of sodium hypochlorite and soils, including carbon tetrachloride, trihalomethanes (THM, such as chloroform), and trihaloacetic acid (THAA, in this case trichloroacetic acid). Most AOX go into the sewer with wash water.

NICK AND DUSTIN WERE HERE

Dilution

Bleach is sold extremely concentrated and must be diluted to be used safely when disinfecting surfaces and when used to treat drinking water. When disinfecting most surfaces, 1 part bleach to 9 parts water is sufficient for sanitizing. In an emergency, drinking water can be treated: Ratio of bleach to water for purification: 2 drops of bleach per quart of water or 8 drops of bleach per gallon of water; 1/2 teaspoon bleach per five gallons of water. If water is cloudy, double the recommended dosages of bleach. Additional bleach will not kill more bacteria and can endanger health.[2]

Chemistry

The process of bleaching can be summarized in the following set of chemical reactions:

Cl2(aq) + H2O(l) H+(aq) + Cl-(aq) + HClO(aq)

The H+ ion of the hypochlorous acid then dissolves into solution, and so the final result is effectively:

Cl2(aq) + H2O(l) 2H+(aq) + Cl-(aq) + ClO-(aq)

Hypochlorite tends to decompose into chloride and a highly reactive form of oxygen:

2ClO- 2Cl- + O2

Mechanism of bleach action

Color in most dyes and pigments are produced by molecules, such as beta carotene, which contain chromophores. Chemical bleaches work in one of two ways:

  • An oxidizing bleach works by breaking the chemical bonds that make up the chromophore. This changes the molecule into a different substance that either does not contain a chromophore, or contains a chromophore that does not absorb visible light.
  • A reducing bleach works by converting double bonds in the chromophore into single bonds. This eliminates the ability of the chromophore to absorb visible light.[3]

Sunlight acts as a bleach through a process leading to similar results: high energy photons of light, often in the violet or ultraviolet range, can disrupt the bonds in the chromophore, rendering the resulting substance colorless. Extended exposure often leads to massive discoloration usually reducing the colors to white and typically very faded blue spectrums.[4]

Sodium hypochlorite's anti-bacterial mechanism works by causing proteins to aggregate.[5][6]

Antimicrobial efficacy

The broad-spectrum effectiveness of bleach, particularly sodium hypochlorite, owes to the nature of its chemical reactivity with microbes. Rather than acting in an inhibitory or toxic fashion in the manner of antibiotics, bleach quickly reacts with microbial cells to irreversibly denature and destroy many pathogens. Bleach, particularly sodium hypochlorite has been shown to react with a microbe's heat shock proteins, stimulating their role as intra-cellular chaperone and causing the bacteria to form into clumps (much like an egg that has been boiled) that will eventually die off. In some cases, bleach's base acidity compromises a bacterium's lipid membrane, a reaction similar to popping a balloon. The range of micro-organisms effectively killed by bleach (particularly sodium hypochlorite) is extensive, making it an extremely versatile disinfectant.

In response to infection, the human immune system will produce a strong oxidizer, hypochlorous acid, to kill bacterial invaders.

See also

References

  1. ^ "Ozo formulas". Ozone Information. 
  2. ^ "Guidelines for the Use of Sanitizers and Disinfectants in Child Care Facilities". Virginia Department of Health. Retrieved 2010-03-16. 
  3. ^ Field, Simon Q (2006). "Ingredients -- Bleach". Science Toys. Retrieved 2006-03-02. 
  4. ^ Bloomfield, Louis A (2006). "Sunlight". How Things Work Home Page. Retrieved 2006-03-02. 
  5. ^ Reuters (2008). "Mystery solved: How bleach kills germs". MSNBC.com. Retrieved 2008-11-13. 
  6. ^ Jakob, U. (14 November 2008). "Bleach Activates a Redox-Regulated Chaperone by Oxidative Protein Unfolding". Cell. Elsevier. 135 (4): 691–701. PMC 2606091Freely accessible. PMID 19013278. doi:10.1016/j.cell.2008.09.024. Retrieved 2008-11-19.  Unknown parameter |coauthors= ignored (|author= suggested) (help)

Further reading

  • Bodkins, Dr. Bailey. Bleach. Philadelphia: Virginia Printing Press, 1995.
  • Trotman, E.R. Textile Scouring and Bleaching. London: Charles Griffin & Co., 1968. ISBN 0852640676.

External links