Bleach - Wikipedia. Bleach is a chemical that whitens clothing. The bleaching process has been known for millennia. Chlorine is the basis for the most common bleaches: for example, the solution of sodium hypochlorite, which is so ubiquitous that most simply call it . Oxidizing bleaching agents that do not contain chlorine are usually based on peroxides such as hydrogen peroxide, sodium percarbonate and sodium perborate. While most bleaches are oxidizing agents, some are reducing agents such as sodium dithionite and sodium borohydride. Bleaches are used as household chemicals to whiten clothes and remove stains and as disinfectants, primarily in the bathroom and kitchen. Many bleaches have strong bactericidal properties, and are used for disinfecting and sterilizing and thus are used in swimming pool sanitation to control bacteria, viruses and algae and in any institution where sterile conditions are needed. They are also used in many industrial processes, notably in the bleaching of wood pulp. Bleach is also used for removing mildew, killing weeds and increasing the longevity of cut flowers. Scottish chemist and industrialist Charles Tennant first produced a solution of calcium hypochlorite, then solid calcium hypochlorite (bleaching powder). 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. A reducing bleach works by converting double bonds in the chromophore into single bonds. Several general types of chemical reactions can occur based on what happens when going from reactants to products. The more common types of chemical reactions are as. Common household goods, personal care products, and even food and water, are major sources of chemical exposure that can lead to an.
This eliminates the ability of the chromophore to absorb visible light. This is the mechanism of bleaches based on sulfur dioxide. Extended exposure often leads to massive discoloration usually reducing the colors to white and typically very faded blue spectrums. 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. The range of micro- organisms effectively killed by bleach (particularly sodium hypochlorite) is extensive, making it an extremely versatile disinfectant. The same study found that at low (micromolar) sodium hypochlorite levels, E. The concentration of chlorine- based bleaches is often expressed as percent active chlorine where one gram of a 1. These bleaches can react with other common household chemicals like vinegar or ammonia to produce toxic gases. Labels on sodium hypochlorite bleach warn about these interactions. Chemical interactions. Mixing a hypochlorite bleach with an acid can liberate chlorine gas. Hypochlorite and chlorine are in equilibrium in water; the position of the equilibrium is p. H dependent and low p. H (acidic) favors chlorine. As little as 3. 5. Exposure to chlorine has been limited to 0. OSHA in the U. S. These materials are very irritating to the eyes and lungs and are toxic above certain concentrations; nitrogen trichloride is also a very sensitive explosive. NH3 + Na. OCl . This is, in effect, an application of the non- common ion theory, or as discussed in Wikipedia under Solubility Equilibrium as the 'salt effect'. With respect to bleaching powder, which has been described as a compound salt of the form Ca(Cl. O)2. Ca. Cl. 2. Ca(OH)2. H2. O, the presence of Ca. Cl. 2 in very concentrated solutions can greatly increase the 'activity level' of weak acids. So, in this particular proposed application, H2. CO3 from CO2 and moisture on the bleaching powder, acts on the Ca. Cl. 2 to release some HCl which acts on the HCl. O releasing Chlorine: HCl. O + HCl . This solution of sodium hypochlorite, commonly referred to as simply . It is produced by passing chlorine gas through a dilute sodium hydroxide solution. It is usually a white powder. A purer, more stable form of calcium hypochlorite is called HTH or high test hypochlorite. Bleaching tablets contain calcium hypochlorite and other ingredients to prevent the tablets from crumbling. A supposedly more stable mixture of calcium hypochlorite and quicklime (calcium oxide) is known as . It is used as a disinfectant in water treatment, especially to make drinking water and in large public swimming pools. Chlorine was used extensively to bleach wood pulp, but this use has decreased significantly due to environmental concerns. Chlorine dioxide. Chlorine dioxide, Cl. O2, is an unstable gas and is used in situ or stored as dilute aqueous solutions. Despite these limitations it finds large- scale applications for the bleaching of wood pulp, fats and oils, cellulose, flour, textiles, beeswax, skin, and in a number of other industries. It can be prepared by oxidizing sodium chlorite with chlorine. Na. Cl. O2 + Cl. 2 . Peroxides are compounds that contain an oxygen- oxygen single bond, O- O. This is a fairly weak bond so reactions of peroxides often involve breaking this bond, giving very reactive oxygen species. Most peroxide bleaches are adducts of hydrogen peroxide. They contain hydrogen peroxide, HOOH in combination with another material like sodium carbonate or urea. An exception is sodium perborate, which has a cyclic structure containing two O- O single bonds. All peroxide- based bleaches release hydrogen peroxide when dissolved in water. Peroxide bleaches are often used with catalysts and activators, e. Hydrogen peroxide. Hydrogen peroxide is produced in very large amounts by several different processes. Its action as an oxidizer is why it is made and used in such large quantities. It is used by itself as a bleaching agent, for example to bleach wood pulp, hair and so on, or to prepare other bleaching agents like the perborates, percarbonates, peracids, etc. Sodium percarbonate. Sodium percarbonate is produced industrially by reaction of sodium carbonate and hydrogen peroxide, followed by crystallization. Also, dry sodium carbonate may be treated directly with concentrated hydrogen peroxide solution. Na. 2CO3 + 3. H2. O2. It is generally considered to be an eco- friendly cleaning agent. Sodium perborate. Sodium perborate, Na. H4. B2. O8, is made by reacting borax with sodium hydroxide to give sodium metaborate (Na. BO2) which is then reacted with hydrogen peroxide to give hydrated sodium perborate. When dissolved in water it forms some hydrogen peroxide, but also perborate anion (B(OOH)(OH)3. It is a white crystalline powder with a weak sulfurous odor. It can be obtained by reacting sodium bisulfite with zinc. Na. HSO3 + Zn . Disappearance of hypochlorite is practically immediate in the natural aquatic environment, reaching in a short time concentration as low as 1. In addition, it was found that while volatile chlorine species may be relevant in some indoor scenarios, they have negligible impact in open environmental conditions. Further, the role of hypochlorite pollution is assumed as negligible in soils. Industrial bleaching agents can also 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. The study showed that indoor air concentrations significantly increase (8–5. 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. The OSHA- allowable time- weighted average concentration over an eight- hour period is 1. When disinfecting most surfaces, 1 part liquid household bleach to 1. Stronger or weaker solutions may be more appropriate to meet specific goals, such as destroying resistant viruses or sanitizing surfaces that will not be in contact with food. See references for more information. The solution is corrosive, and needs to be thoroughly removed afterwards, so the bleach disinfection is sometimes followed by an ethanol disinfection. Cambridge University Press. March 2. 01. 0. The Cotton Industry. Shire Publications Ltd. ISBN 0- 8. 52. 63- 5. L. Annales de chimie et de physique. Thesis, University of Twente, the Netherlands ISBN9. Retrieved 8 May 2. Surfactants and Detergents. Retrieved 8 May 2. Science Toys. Retrieved 2. How Things Work Home Page. Retrieved 2. 01. 2- 0. Ilbert; P. C. F. 1. PMC 2. 60. 60. 91 . PMID 1. 90. 13. 27. Retrieved 2. 00. 8- 1. The Journal of Biological Chemistry. PMID 1. 76. 15. 0. Proceedings of the National Academy of Sciences of the United States of America. PMC 3. 19. 02. 1 . PMID 6. 26. 44. 34. Wilkinson (1. 97. Advanced Inorganic Chemistry. John Wiley and Sons Inc. ISBN 0- 4. 71- 1. Retrieved 2. 00. 7- 0. Production and degradation reactions of chloramines. Bulletin de la Societe Chimique de France. ISBN 3- 5. 27- 3. Lenntech. com. Retrieved 2. E.; Wintzer, P.; Sheikh, S. A.; Gallone, P.; Vasudevan, S.; Pelin, K. Ullmann's Encyclopedia of Industrial Chemistry. World Health Organization. Retrieved 2. 7 May 2. E.; Wintzer, P.; Sheikh, S. A.; Gallone, P.; Vasudevan, S.; Pelin, K. Ullmann's Encyclopedia of Industrial Chemistry. Wang (1. 99. 6). International Pulp Bleaching Conference. Retrieved 2. 01. 2- 0. Retrieved 2. 01. 2- 0. Ozone Information. Organic building blocks of the chemical industry. John Wiley and Sons. ISBN 0- 4. 71- 8.
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