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Bleach

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This article is about the chemical. For other uses, see Bleach (disambiguation).

Bleach is the generic name for any chemical product that is used industrially or domestically to remove color from (i.e. to whiten) fabric or fiber (in a process called bleaching) or to disinfect after cleaning. It often refers specifically to a dilute solution of sodium hypochlorite, also called "liquid bleach".

Clorox brand bleach

Many bleaches have broad-spectrum bactericidal properties, making them useful for disinfecting and sterilizing. They are used in swimming pool sanitation to control bacteria, viruses, and algae and in many places where sterile conditions are required. They are also used in many industrial processes, notably in the bleaching of wood pulp. Bleaches also have other minor uses, like removing mildew, killing weeds, and increasing the longevity of cut flowers.[1]

Bleaches work by reacting with many colored organic compounds, such as natural pigments, and turning them into colorless ones. While most bleaches are oxidizing agents (chemicals that can remove electrons from other molecules), some are reducing agents (that donate electrons).

Chlorine, a powerful oxidizer, is the active agent in many household bleaches. Since pure chlorine is a toxic corrosive gas, these products usually contain hypochlorite, which releases chlorine. "Bleaching powder" usually refers to a formulation containing calcium hypochlorite.[citation needed]

Oxidizing bleaching agents that do not contain chlorine are usually based on peroxides, such as hydrogen peroxide, sodium percarbonate, and sodium perborate. These bleaches are called "non-chlorine bleach", "oxygen bleach", or "color-safe bleach".[2]

Reducing bleaches have niche uses, such as sulfur dioxide, which is used to bleach wool, either as gas or from solutions of sodium dithionite,[3] and sodium borohydride.

Bleaches generally react with many other organic substances besides the intended colored pigments, so they can weaken or damage natural materials like fibers, cloth, and leather, and intentionally applied dyes, such as the indigo of denim. For the same reason, ingestion of the products, breathing of the fumes, or contact with skin or eyes can cause bodily harm and damage health.

History

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Early method of bleaching cotton and linen goods on lawns, using a combination of exposure to direct sunlight and the application of water

The earliest form of bleaching involved spreading fabrics and cloth out in a bleachfield to be whitened by the action of the Sun and water.[4][5] In the 17th century, there was a significant cloth bleaching industry in Western Europe, using alternating alkaline baths (generally lye) and acid baths (such as lactic acid from sour milk, and later diluted sulfuric acid). The whole process lasted up to six months.[4]

Chlorine-based bleaches, which shortened that process from months to hours, were invented in Europe in the late 18th century. Swedish chemist Carl Wilhelm Scheele discovered chlorine in 1774,[4] and in 1785 Savoyard scientist Claude Berthollet recognized that it could be used to bleach fabrics.[4] Berthollet also discovered sodium hypochlorite, which became the first commercial bleach, named Eau de Javel ("Javel water") after the borough of Javel, near Paris, where it was produced.

Scottish chemist and industrialist Charles Tennant proposed in 1798 a solution of calcium hypochlorite as an alternative for Javel water, and patented bleaching powder (solid calcium hypochlorite) in 1799.[4][6] Around 1820, French chemist Antoine Germain Labarraque discovered the disinfecting and deodorizing ability of hypochlorites and was instrumental in popularizing their use for such purpose.[7] His work greatly improved medical practice, public health, and the sanitary conditions in hospitals, slaughterhouses, and all industries dealing with animal products.[8]

Louis Jacques Thénard first produced hydrogen peroxide in 1818 by reacting barium peroxide with nitric acid.[9] Hydrogen peroxide was first used for bleaching in 1882, but did not become commercially important until after 1930.[10] Sodium perborate as a laundry bleach has been used in Europe since the early twentieth century, and became popular in North America in the 1980s.[11]

Mechanism of action

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Whitening

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Colors of natural organic materials typically arise from organic pigments, such as beta carotene. 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. This is the mechanism of bleaches based on chlorine but also of oxygen-anions which react through the initial nucleophilic attack.[12]
  • 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. This is the mechanism of bleaches based on sulfur dioxide.[13]

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 a white and typically very faded blue.[14]

Antimicrobial efficacy

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The broad-spectrum effectiveness of most bleaches is due to their general chemical reactivity against organic compounds, rather than the selective inhibitory or toxic actions of antibiotics. They irreversibly denature or destroy many proteins, including all prions, making them extremely versatile disinfectants.

Hypochlorite bleaches in low concentration were also found to attack bacteria by interfering with heat shock proteins on their walls.[15] According to 2013 Home Hygiene and Health report,[16] using bleach, whether chlorine- or peroxide-based, significantly increases germicidal efficiency of laundry even at low temperatures (30-40 degrees Celsius), which makes it possible to eliminate viruses, bacteria, and fungi from a variety of clothing in a home setting.[17]

Types of bleaches

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Most industrial and household bleaches belong to three broad classes:

Chlorine-based bleaches

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Chlorine-based bleaches are found in many household "bleach" products, as well as in specialized products for hospitals, public health, water chlorination, and industrial processes.

The grade of chlorine-based bleaches is often expressed as percent active chlorine. One gram of 100% active chlorine bleach has the same bleaching power as one gram of elemental chlorine.

The most common chlorine-based bleaches are:

Other examples of chlorine-based bleaches, used mostly as disinfectants, are monochloramine, halazone, and sodium dichloroisocyanurate.[19][failed verification]

Peroxide-based bleaches

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Peroxide-based bleaches are characterized by the peroxide chemical group, namely two oxygen atoms connected by a single bond, (–O–O–). This bond is easily broken, giving rise to very reactive oxygen species, which are the active agents of this type of bleach.

The main products in this class are:

In the food industry, other oxidizing products like bromates are used as flour bleaching and maturing agents.

Reducing bleaches

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Sodium dithionite (also known as sodium hydrosulfite) is one of the most important reductive bleaching agents. It is a white crystalline powder with a weak sulfurous odor. It can be obtained by reacting sodium bisulfite with zinc

2 NaHSO3 + Zn → Na2S2O4 + Zn(OH)2

It is used as such in some industrial dyeing processes to eliminate excess dye, residual oxide, and unintended pigments and for bleaching wood pulp.

Reaction of sodium dithionite with formaldehyde produces Rongalite,

Na2S2O4 + 2 CH2O + H2O → NaHOCH2SO3 + NaHOCH2SO2

which is used in bleaching wood pulp, cotton, wool, leather and clay.[25]

Photographic bleach

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In Negative film processing, silver halide grains are associated with couplers which, on development, produce metallic silver and a colored image. The silver is 'bleached' to a soluble form in a solution of ferric EDTA, which is then dissolved in 'fix', a solution of sodium or ammonium thiosulfate. The procedure is the same for paper processing except that the EDTA and thiosulfate are mixed in 'bleachfix'.

In Reversal processing, residual silver in the emulsion after the first development is reduced to a soluble silver salt using a chemical bleach, most commonly EDTA. A conventional fixer then dissolves the reduced silver but leaves the unexposed silver halide intact. This unexposed halide is then exposed to light or chemically treated so that a second development produces a positive image. In color and chromogenic film, this also generates a dye image in proportion to the silver.

Photographic bleaches are also used in black-and-white photography to selectively reduce silver to reduce silver density in negatives or prints. In such cases, the bleach composition is typically an acid solution of potassium dichromate.

Environmental impact

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A Risk Assessment Report (RAR) conducted by the European Union on sodium hypochlorite conducted under Regulation EEC 793/93 concluded that this substance is safe for the environment in all its current, normal uses.[26] This is due to its high reactivity and instability. The disappearance of hypochlorite is practically immediate in the natural aquatic environment, reaching in a short time concentration as low as 10−22 μg/L or less in all emission scenarios. In addition, it was found that while volatile chlorine species may be relevant in some indoor scenarios, they have a negligible impact in open environmental conditions. Further, the role of hypochlorite pollution is assumed as negligible in soils.

Industrial bleaching agents can be sources of concern. For example, the use of elemental chlorine in the bleaching of wood pulp produces organochlorines and persistent organic pollutants, including dioxins. According to an industry group, the use of chlorine dioxide in these processes has reduced the dioxin generation to under-detectable levels.[27] However, the respiratory risk from chlorine and highly toxic chlorinated byproducts still exists.

A European study conducted in 2008 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).[28] 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 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,[28][29] this conclusion appears to be hypothetical:

  • The highest level cited for a 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 eight hours is 10 ppm,[30] almost 140 times higher;
  • The OSHA highest allowable peak concentration (5-minute exposure for five minutes in 4 hours) is 200 ppm,[30] twice as high as the reported highest peak level (from the headspace of a bottle of a sample of bleach plus detergent).

Disinfection

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Sodium hypochlorite solution, 3–6%, (common household bleach) is typically diluted for safe use when disinfecting surfaces and when used to treat drinking water.[31][32]

A weak solution of 2% household bleach in warm water is typical for sanitizing smooth surfaces before the brewing of beer or wine.[citation needed]

US government regulations (21 CFR 178 Subpart C) 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).

A 1-in-47 dilution of household bleach with water (1 part bleach to 47 parts water: e.g. one teaspoon of bleach in a cup of water, or 21 ml per litre, or ⁠1/3⁠ cup of bleach in a gallon of water) is effective against many bacteria and some viruses in homes.[33] 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).[34]

See hypochlorous acid for a discussion of the mechanism for disinfectant action.

An oral rinse with a 0.05% dilute solution of household bleach is shown to treat gingivitis.[35]

Color-safe bleach

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Color-safe bleach is a solution with hydrogen peroxide as the active ingredient (for stain removal) rather than sodium hypochlorite or chlorine.[36] It also has chemicals[which?] in it that help brighten colors.[37] Though hydrogen peroxide is used for sterilization purposes and water treatment, its ability to disinfect laundry is limited because the concentration of hydrogen peroxide in laundry products is lower than what is used in other applications.[37]

Health hazards

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The safety of bleaches depends on the compounds present, and their concentration.[38] Generally speaking, the ingestion of bleaches will cause damage to the esophagus and stomach, possibly leading to death. On contact with the skin or eyes, it causes irritation, drying, and potentially burns. Inhalation of bleach fumes can cause mild irritation of the upper airways.[38] Personal protective equipment should always be used when using bleach.

Bleach should never be mixed with vinegar or other acids, as this will create highly toxic chlorine gas, which can cause severe burns internally and externally.[39][40][41][42] Mixing bleach with ammonia similarly produces chloramine gas, which can burn the lungs.[39][40][42] Mixing bleach with rubbing alcohol or acetone makes chloroform,[43] while mixing with hydrogen peroxide results in an exothermic and potentially explosive chemical reaction that releases oxygen.[44]

False claims as a cure

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Main article: Miracle Mineral Supplement

Miracle Mineral Supplement (MMS), also promoted as "Master Mineral Solution" or "Chlorine Dioxide Solution" or CDS,[45] to evade restrictions by online retail platforms, is a bleach solution that has been fraudulently promoted as a cure-all since 2006.[46] Its main active ingredient is sodium chlorite, which is "activated" with citric acid to form chlorine dioxide. In an attempt to evade health regulations, its inventor, Jim Humble, a former Scientologist, founded the Genesis II Church of Health and Healing, which considers MMS as its sacrament.[47][48]

See also

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References

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  1. ^ "12 Smart Ways to Use Bleach - Reader's Digest". 9 March 2010.
  2. ^ "Oxygen Bleach Vs. Chlorine Bleach". Sciencing. Retrieved 16 April 2018.
  3. ^ Phillips, H. (2008). "The Bleaching of Wool with Sulphur Dioxide and with Solutions of Sulphites". Journal of the Society of Dyers and Colorists. 54 (11): 503–512. doi:10.1111/j.1478-4408.1938.tb01992.x.
  4. ^ a b c d e Chisholm, Hugh, ed. (1911). "Bleaching" . Encyclopædia Britannica (11th ed.). Cambridge University Press.
  5. ^ Aspin, Chris (1981). The Cotton Industry. Shire Publications. p. 24. ISBN 978-0-85263-545-2.
  6. ^ Chisholm 1911.
  7. ^ Scott, James, transl. (1828). On the disinfecting properties of Labarraque's preparations of chlorine Published by S. Highley.
  8. ^ Labarraque, Antoine-Germain, Nouvelle biographie générale, volume 28 (1859), columns 323-324.
  9. ^ L. J. Thénard (1818). "Observations sur des nouvelles combinaisons entre l'oxigène et divers acides". Annales de chimie et de physique. 2nd Series. 8: 306–312.
  10. ^ Tatjana Topalović (2007). Catalytic Bleaching of Cotton: Molecular and Macroscopic Aspects p 16. Thesis, University of Twente, the Netherlands. ISBN 978-90-365-2454-4. Retrieved 8 May 2012.
  11. ^ Milne, Neil (1998). "Oxygen bleaching systems in domestic laundry". Journal of Surfactants and Detergents. 1 (2): 253–261. doi:10.1007/s11743-998-0029-z. S2CID 59456079.
  12. ^ Mayer, Robert J.; Ofial, Armin R. (22 February 2018). "Nucleophilic Reactivities of Bleach Reagents". Organic Letters. 20 (10): 2816–2820. doi:10.1021/acs.orglett.8b00645. PMID 29741385.
  13. ^ Field, Simon Q (2006). "Ingredients – Bleach". Science Toys. Retrieved 2 March 2006.
  14. ^ Bloomfield, Louis A (2006). "Sunlight". How Things Work Home Page. Archived from the original on 11 May 2013. Retrieved 23 February 2012.
  15. ^ Jakob, U.; J. Winter; M. Ilbert; P.C.F. Graf; D. Özcelik (14 November 2008). "Bleach Activates A Redox-Regulated Chaperone by Oxidative Protein Unfolding". Cell. 135 (4): 691–701. doi:10.1016/j.cell.2008.09.024. PMC 2606091. PMID 19013278.
  16. ^ "| Home Hygiene & Health". www.ifh-homehygiene.org. 21 October 2013. Retrieved 12 December 2020.
  17. ^ Ploumanac'h. "Sanitize Laundry for Delicate Clothes". Ploumanac'h. Retrieved 12 December 2020.
  18. ^ Vogt, Helmut; Balej, Jan; Bennett, John E.; Wintzer, Peter; Sheikh, Saeed Akbar; Gallone, Patrizio; Vasudevan, Subramanyan; Pelin, Kalle (2010). "Chlorine Oxides and Chlorine Oxygen Acids". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a06_483.pub2. ISBN 978-3527306732. S2CID 96905077.
  19. ^ a b "WHO Model List of Essential Medicines (19th List)" (PDF). World Health Organization. April 2015. Archived (PDF) from the original on 13 December 2016. Retrieved 8 December 2016.
  20. ^ Douglass F. Taber. "Oxidizing agents: Sodium perborate". Retrieved 7 June 2012.
  21. ^ V. Namboodiri and A. Garg (2017): "Evaluation of Combined Peracetic acid and UV treatment for Disinfection of Secondary Wastewater Effluent". document EPA/600/R-17/172, National Risk Management Research Laboratory, U.S. Environmental Protection Agency,
  22. ^ (2004) "Benzoyl peroxide" FAO Publication FNP 52 Addendum 12.
  23. ^ "Ozo formulas". Ozone Information. Archived from the original on 15 July 2011. Retrieved 9 January 2009.
  24. ^ Pang, S.; Fiume, M. Z. (2001). "Final Report on the Safety Assessment of Ammonium, Potassium, and Sodium Persulfate". International Journal of Toxicology. 20 (3_suppl): 7–21. doi:10.1080/10915810152630710. PMID 11766134. S2CID 25763799.
  25. ^ Herman Harry Szmant (1989). Organic building blocks of the chemical industry. John Wiley and Sons. p. 113. ISBN 978-0-471-85545-3. OCLC 19122597.
  26. ^ European Union Risk Assessment Report. 2007. Sodium Hypochlorite (CAS No: 7681-52-9; EINECS No: 231-668-3): Final report, November 2007 (Final Approved Version); see Risk Assessment Report on Sodium Hypochlorite, Scientific Committee on Health and Environmental Risks, 12 March 2008.
  27. ^ "ECF: The Sustainable Technology" (PDF). Alliance for Environmental Technology. Archived from the original (PDF) on 14 April 2008. Retrieved 19 September 2007.
  28. ^ a b Odabasi, Mustafa (March 2008). "Halogenated Volatile Organic Compounds from the Use of Chlorine-Bleach-Containing Household Products". Environmental Science & Technology. 42 (5): 1445–1451. Bibcode:2008EnST...42.1445O. doi:10.1021/es702355u. PMID 18441786.
  29. ^ Odabasi, Mustafa (2008). "Halogenated Volatile Organic Compounds from the Use of Chlorine-Bleach- Containing Household Products, Flash Slide presentation".[dead link]
  30. ^ a b "Chemical Sampling Information: Carbon Tetrachloride". OSHA. 16 June 2004. Archived from the original on 14 November 2009. Retrieved 4 December 2009.
  31. ^ Dvorak, Glenda (February 2005). "Disinfection" (PDF). Center for Food Security and Public Health. Ames, IA: Center for Food Security and Public Health, Iowa State University. p. 12. Archived from the original (PDF) on 19 June 2010. Retrieved 7 February 2011.
  32. ^ "Guidelines for the Use of Sanitizers and Disinfectants in Child Care Facilities". Virginia Department of Health. Archived from the original on 14 June 2010. Retrieved 16 March 2010.
  33. ^ "Everyday Steps and Extra Steps When Someone Is Sick". Center for Disease Control. 11 February 2020.
  34. ^ "Kam Scientific Inc". Kam Scientific Inc. Archived from the original on 9 May 2020. Retrieved 2 May 2020.
  35. ^ De Nardo, R.; Chiappe, V. N.; Gómez, M.; Romanelli, H.; Slots, J. R. (2012). "Effects of 0.05% sodium hypochlorite oral rinse on supragingival biofilm and gingival inflammation". International Dental Journal. 62 (4): 208–212. doi:10.1111/j.1875-595X.2011.00111.x. PMC 9374941. PMID 23017003.
  36. ^ "Dr Laundry - Clorox". 28 October 2015. Archived from the original on 9 June 2011.
  37. ^ a b "Clothes Stain Remover - Pretreat Spray | Clorox®". 27 June 2015.
  38. ^ a b Slaughter RJ, Watts M, Vale JA, Grieve JR, Schep LJ (2019), "The clinical toxicology of sodium hypochlorite", Clinical Toxicology, 57 (5): 303–311, doi:10.1080/15563650.2018.1543889, PMID 30689457, S2CID 59339240
  39. ^ a b "Dangers of Mixing Bleach with Cleaners". Washington State Department of Health. Retrieved 12 February 2020.
  40. ^ a b "Some Things Just Don't Mix: Poison Control Tips for Chemicals". Missouri Poison Center. 2 March 2018. Retrieved 12 February 2020.
  41. ^ "Lesson Learned - Accidental Mixing of Bleach and Acid". Regents of the University of California. Retrieved 12 February 2020.
  42. ^ a b Freedman, Lisa; Mcdonough, Lauren Smith (22 March 2019). "6 Cleaning Products You Should Never, Ever Mix". Good Housekeeping. Retrieved 12 February 2019.
  43. ^ "Dangerous Household Cleaning Combinations: WHAT NOT TO MIX". Georgia Department of Public Health. Retrieved 22 January 2024.
  44. ^ "Accidental mix of bleach and acid kills Buffalo Wild Wings employee". Chemical & Engineering News. 13 November 2019.
  45. ^ Loh, John Ming Ren; Shafi, Humaira (24 November 2014). "Kikuchi-Fujimoto disease presenting after consumption of 'Miracle Mineral Solution' (sodium chlorite)". BMJ Case Reports. 2014: bcr2014205832. doi:10.1136/bcr-2014-205832. ISSN 1757-790X. PMC 4244351. PMID 25422331.
  46. ^ Robbins, Martin (15 September 2010). "The man who encourages the sick and dying to drink industrial bleach". The Guardian. London. Retrieved 20 July 2020.
  47. ^ "FDA warns consumers about the dangerous and potentially life threatening side effects of Miracle Mineral Solution" (Press release). Food and Drug Administration. 12 August 2019. Archived from the original on 13 October 2023. Retrieved 16 January 2024.
  48. ^ Kuruvilla, Carol (22 May 2019). "New Jersey Pastor Has Been Passing Off Bleach As A 'Miracle Cure' In Uganda: Report". HuffPost. Retrieved 25 April 2020.

Further reading

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  • Bodkins, Bailey. Bleach. Philadelphia: Virginia Printing Press, 1995.[full citation needed]
  • Trotman, E. R. Textile Scouring and Bleaching. London: Charles Griffin & Co., 1968. ISBN 0-85264-067-6.
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