Liquid bleach

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Liquid bleach (sodium hypochlorite solution) packaged for household use. Clorox Bleach products.jpg
Liquid bleach (sodium hypochlorite solution) packaged for household use.

Liquid bleach, often called just bleach, is a common chemical household product that consists of a dilute solution of sodium hypochlorite (NaClO) and other secondary ingredients. It is a chlorine releasing bleaching agent widely used to whiten clothes and remove stains, as a disinfectant to kill germs, and for several other uses.

Contents

While the term has had this meaning for a long time, it may now be applied more generically to any liquid bleaching agent for laundry, irrespective of composition, such as peroxide-based bleaches.

History

Potassium hypochlorite (KClO) was synthesized by French scientist Berthollet in 1789, by reacting chlorine gas (Cl
2
) with a solution of potassium hydroxide (potash, KOH). He also discovered its cloth bleaching properties, and set out to commercialize it under the name of Eau de Javel ("water of Javel") after the borough of Paris where it was manufactured. It was the first product intended specifically for that application, and it shortened the process of bleaching newly made cloth from months to hours.

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, Ca(ClO)2) in 1799. [1]

Around 1820, Antoine Labarraque substituted the much cheaper precursor sodium hydroxide (soda lye, NaOH) for potash, thus producing Eau de Labarraque, basically the same "liquid bleach" (NaClO) still in use today. He also discovered its disinfectant properties, and was instrumental in spreading it worldwide for that purpose. [2] His work greatly improved medical practice, public health, the sanitary conditions in hospitals, slaughterhouses, and all industries dealing with animal products—decades before Pasteur and others established the germ theory of disease. [3] In particular, it led to the nearly universal practice of chlorination of tap water to prevent the spread of diseases like typhoid fever and cholera. [4] [5]

Composition

The active agent in liquid bleach is sodium hypochlorite, which gives the product a light greenish yellow tinge and its characteristic chlorine smell. [6]

Formulations for household use usually contain 8% or less of sodium hypochlorite by weight, although more concentrated solutions of up to 50% are available for industrial use. [7] Concentrated solutions present serious safety risks. Solid anhydrous sodium hypochlorite is unstable and decomposes explosively. A non-explosive hydrated solid is available for laboratory use, but must be kept refrigerated to avoid decomposition.

Liquid bleach usually contains also some sodium hydroxide (caustic soda or soda lye, NaOH), intended to keep the solution alkaline. Sodium chloride (table salt, NaCl) is often present too, and plays no role in the product's action. Sodium chloride and hydroxide are normal residues from the main production processes.

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Chlorine is a chemical element; it has symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity on the revised Pauling scale, behind only oxygen and fluorine.

<span class="mw-page-title-main">Sodium carbonate</span> Chemical compound

Sodium carbonate is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water. Historically, it was extracted from the ashes of plants grown in sodium-rich soils, and because the ashes of these sodium-rich plants were noticeably different from ashes of wood, sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process, as well as by carbonating sodium hydroxide which is made using the Chlor-alkali process.

<span class="mw-page-title-main">Sodium hypochlorite</span> Chemical compound (known in solution as bleach)

Sodium hypochlorite is an alkaline inorganic chemical compound with the formula NaOCl. It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. It is the sodium salt of hypochlorous acid, consisting of sodium cations and hypochlorite anions.

<span class="mw-page-title-main">Potassium hydroxide</span> Inorganic compound (KOH)

Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash.

<span class="mw-page-title-main">Potassium chlorate</span> Chemical compound

Potassium chlorate is a compound containing potassium, chlorine and oxygen, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. After sodium chlorate, it is the second most common chlorate in industrial use. It is a strong oxidizing agent and its most important application is in safety matches. In other applications it is mostly obsolete and has been replaced by safer alternatives in recent decades. It has been used

<span class="mw-page-title-main">Hypochlorite</span> Ion

In chemistry, hypochlorite, or chloroxide is an anion with the chemical formula ClO. It combines with a number of cations to form hypochlorite salts. Common examples include sodium hypochlorite and calcium hypochlorite. The Cl-O distance in ClO is 1.69 Å.

The chloralkali process is an industrial process for the electrolysis of sodium chloride (NaCl) solutions. It is the technology used to produce chlorine and sodium hydroxide, which are commodity chemicals required by industry. Thirty five million tons of chlorine were prepared by this process in 1987. The chlorine and sodium hydroxide produced in this process are widely used in the chemical industry.

<span class="mw-page-title-main">Sodium chlorate</span> Chemical compound

Sodium chlorate is an inorganic compound with the chemical formula NaClO3. It is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 300 °C to release oxygen and leaves sodium chloride. Several hundred million tons are produced annually, mainly for applications in bleaching pulp to produce high brightness paper.

Calcium hypochlorite is an inorganic compound with chemical formula Ca(ClO)2, also written as Ca(OCl)2. It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow decomposition in moist air. This compound is relatively stable as a solid and solution and has greater available chlorine than sodium hypochlorite. "Pure" samples have 99.2% active chlorine. Given common industrial purity, an active chlorine content of 65-70% is typical. It is the main active ingredient of commercial products called bleaching powder, used for water treatment and as a bleaching agent.

<span class="mw-page-title-main">Sodium dichloroisocyanurate</span> Chemical compound

Sodium dichloroisocyanurate is a chemical compound widely used as a cleansing agent and disinfectant. It is a colorless, water-soluble solid, produced as a result of reaction of cyanuric acid with chlorine. The dihydrate is also known as is the potassium salt.

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Calcium chlorate is the calcium salt of chloric acid, with the chemical formula Ca(ClO3)2. Like other chlorates, it is a strong oxidizer.

<span class="mw-page-title-main">Bleach</span> Chemicals used to whiten or disinfect

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

<span class="mw-page-title-main">Cleaning agent</span> Substance used to remove dirt or other contaminants

Cleaning agents or hard-surface cleaners are substances used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing offensive odor, and avoiding the spread of dirt and contaminants to oneself and others. Some cleaning agents can kill bacteria and clean at the same time. Others, called degreasers, contain organic solvents to help dissolve oils and fats.

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<span class="mw-page-title-main">Antoine Germain Labarraque</span> French chemist and pharmacist

Antoine Germain Labarraque was a French chemist and pharmacist, notable for formulating and finding important uses for "Eau de Labarraque" or "Labarraque's solution", a solution of sodium hypochlorite widely used as a disinfectant and deodoriser.

<span class="mw-page-title-main">Water chlorination</span> Chorination of water

Water chlorination is the process of adding chlorine or chlorine compounds such as sodium hypochlorite to water. This method is used to kill bacteria, viruses and other microbes in water. In particular, chlorination is used to prevent the spread of waterborne diseases such as cholera, dysentery, and typhoid.

Potassium hypochlorite is a chemical compound with the chemical formula KOCl, also written as KClO. It is the potassium salt of hypochlorous acid. It consists of potassium cations and hypochlorite anions. It is used in variable concentrations, often diluted in water solution. Its aqueous solutions are colorless liquids that have a strong chlorine smell. It is used as a biocide and disinfectant.

<span class="mw-page-title-main">Chlorine-releasing compounds</span>

Chlorine-releasing compounds, also known as chlorine base compounds, is jargon to describe certain chlorine-containing substances that are used as disinfectants and bleaches. They include the following chemicals: sodium hypochlorite, chloramine, halazone, and sodium dichloroisocyanurate. They are widely used to disinfect water and medical equipment, and surface areas as well as bleaching materials such as cloth. The presence of organic matter can make them less effective as disinfectants. They come as a liquid solution, or as a powder that is mixed with water before use.

References

  1. Chisholm, Hugh, ed. (1911). "Tennant, Charles"  . Encyclopædia Britannica . Vol. 26 (11th ed.). Cambridge University Press.
  2. Scott, James, transl. (1828). On the disinfecting properties of Labarraque's preparations of chlorine Published by S. Highley.
  3. Labarraque, Antoine-Germain, Nouvelle biographie générale , volume 28 (1859), columns 323-324.
  4. Reece, R.J. (1907). "Report on the Epidemic of Enteric Fever in the City of Lincoln, 1904-5." In Thirty-Fifth Annual Report of the Local Government Board, 1905-6: Supplement Containing the Report of the Medical Officer for 1905-6. Published by the Local Government Board, London.
  5. Alexander, Martin; Bloom, Barry R.; Hopwood, David A.; Hull, Roger; Iglewski, Barbara H.; Laskin, Allen I.; Oliver, Stephen G.; Schaechter, Moselio; Summers, William C. (2000). Encyclopedia of Microbiology, Four-Volume Set (2 ed.). Academic Press. ISBN   9780080548487. Archived from the original on 2017-01-18.
  6. "What is sodium hypochlorite? | Environmental Working Group". www.ewg.org. 2023-11-21. Retrieved 2024-04-23.
  7. "Sodium hypochlorite: general information" (PDF). GOV.UK. April 23, 2024.