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Encyclopedia > Citric acid
Citric acid
IUPAC name 2-hydroxypropane-1,2,3-tricarboxylic acid
Other names 3-hydroxypentanedioic acid-3-carboxylic acid

Hydrogen citrate Image File history File links This is a lossless scalable vector image. ... Image File history File links Size of this preview: 800 × 462 pixelsFull resolution (1100 × 635 pixel, file size: 148 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Citric acid ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ...

CAS number 77-92-9
Molecular formula C6H8O7
Molar mass 192.123 g/mol
Appearance crystalline white solid
Density 1.665 g/cm³
Melting point

153 °C CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... The simplified molecular input line entry specification or SMILES is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings. ... A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... For other uses, see Density (disambiguation). ... The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ...

Boiling point

decomposes at 175 °C Italic text This article is about the boiling point of liquids. ...

Solubility in water 133 g/100 ml (20°C)
Acidity (pKa) pKa1=3.15
Main hazards skin and eye irritant
Flash point  ?°C
Related Compounds
Related compounds sodium citrate, calcium citrate
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Citric acid is a weak organic acid found in citrus fruits. It is a natural preservative and is also used to add an acidic (sour) taste to foods and soft drinks. In biochemistry, it is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of almost all living things. It also serves as an environmentally benign cleaning agent and acts as an antioxidant. Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... The acid dissociation constant (Ka), also known as the acidity constant or the acid-ionization constant, is a specific equilibrium constant for the reaction of an acid with its conjugate base in aqueous solution [1]. // When an acid dissolves in water, it partly dissociates forming hydronium ions and its conjugate... The examples and perspective in this article or section may not represent a worldwide view. ... For other uses, see Flash point (disambiguation). ... Sodium citrate is the sodium salt of citric acid with the chemical formula of Na3C6H5O7. ... Calcium citrate is the calcium salt of citric acid. ... The plimsoll symbol as used in shipping In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals exactly). ... Organic chemistry is a specific discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting primarily of carbon and hydrogen, which may contain any number of other elements, including nitrogen, oxygen, halogens as well... For other uses, see Acid (disambiguation). ... Species & major hybrids Species Citrus maxima - Pomelo Citrus medica - Citron Citrus reticulata - Mandarin & Tangerine Major hybrids Citrus x aurantifolia - Lime Citrus x aurantium - Bitter Orange Citrus x bergamia - Bergamot Citrus x hystrix - Kaffir Lime Citrus x ichangensis - Ichang Lemon Citrus x limon - Lemon Citrus x limonia - Rangpur Citrus x paradisi... This article does not cite any references or sources. ... A soft drink is a drink that contains no alcohol. ... Biochemistry (from Greek: , bios, life and Egyptian kēme, earth[1]) is the study of the chemical processes in living organisms. ... Overview of the citric acid cycle The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle, after Hans Adolf Krebs who identified the cycle) is a series of chemical reactions of central importance in all living cells that use oxygen as part... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ... Wiktionary has related dictionary definitions, such as: life, living Life is a multi-faceted concept that may refer to the ongoing process of which living things are a part or the period between fertilisation or mitosis and death. ... Space-filling model of the antioxidant metabolite glutathione. ...

Citric acid exists in a variety of fruits and vegetables, but it is most concentrated in lemons and limes, where it can comprise as much as 8% of the dry weight of the fruit. This article is about the fruit. ... Percentages are relative to US recommendations for adults. ...



At room temperature, citric acid is a white crystalline powder. It can exist either in an anhydrous (water-free) form, or as a monohydrate. The anhydrous form crystallizes from hot water, while the monohydrate forms when citric acid is crystallized from cold water. The monohydrate can be converted to the anhydrous form by heating it above 74 °C. Citric acid also dissolves in absolute (anhydrous) ethanol (76 parts of citric acid per 100 parts of ethanol) at 15 degrees Celsius. As a general term, a substance is said to be anhydrous if it contains no water. ... Hydrate is a term which means different things in inorganic chemistry and organic chemistry. ...

Chemically, citric acid shares the properties of other carboxylic acids. When heated above 175 °C, it decomposes through the loss of carbon dioxide and water. Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -C(=O)OH, usually written -COOH or -CO2H. [1] Carboxylic acids are Bronsted... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... H2O and HOH redirect here. ...

Lemons, grapefruits and other citrus fruit contain citric acid
Lemons, grapefruits and other citrus fruit contain citric acid

Image File history File links Download high-resolution version (1200x848, 313 KB) An edit of Image:Lemon. ... Image File history File links Download high-resolution version (1200x848, 313 KB) An edit of Image:Lemon. ...


The discovery of citric acid has been credited to the 8th century alchemist Jabir Ibn Hayyan (Geber). Medieval scholars in Europe were aware of the acidic nature of lemon and lime juices; such knowledge is recorded in the 13th century encyclopedia Speculum Majus (The Great Mirror), compiled by Vincent of Beauvais. Citric acid was first isolated in 1784 by the Swedish chemist Carl Wilhelm Scheele, who crystallized it from lemon juice. Industrial-scale citric acid production began in 1860, based on the Italian citrus fruit industry. (7th century — 8th century — 9th century — other centuries) Events The Iberian peninsula is taken by Arab and Berber Muslims, thus ending the Visigothic rule, and starting almost 8 centuries of Muslim presence there. ... For other uses, see Alchemy (disambiguation). ... 15th century European portrait of Geber, Codici Ashburnhamiani 1166, Biblioteca Medicea Laurenziana, Florence Jabir Ibn Hayyan , full name Abu Musa Jabir Ibn Hayyan Al-Azdi (أبو موسى جابر بن حيان الأزدي), born c. ... Cyclopedia redirects here. ... The Dominican friar Vincent of Beauvais (ca 1190 - 1264?) wrote the main encyclopedia that was used in the middle ages. ... 1784 was a leap year starting on Thursday (see link for calendar). ... Carl Wilhelm Scheele Scheeles house with his pharmacy in Köping. ...

In 1893, C. Wehmer discovered that Penicillium mold could produce citric acid from sugar. However, microbial production of citric acid did not become industrially important until World War I disrupted Italian citrus exports. In 1917, the American food chemist James Currie discovered that certain strains of the mold Aspergillus niger could be efficient citric acid producers, and Pfizer began industrial-level production using this technique two years later. Species Penicillium bilaiae Penicillium camemberti Penicillium candida Penicillium claviforme Penicillium crustosum Penicillium glaucum Penicillium marneffei Penicillium notatum Penicillium purpurogenum Penicillium roqueforti Penicillium stoloniferum Penicillium viridicatum Penicillium verrucosum Penicillium commune Penicillium is a genus of ascomyceteous fungi that includes: Penicillium bilaiae, which is an agricultural inoculant. ... This article is about the fungi known as molds. ... This article is about sugar as food and as an important and widely traded commodity. ... “The Great War ” redirects here. ... 1917 (MCMXVII) was a common year starting on Monday of the Gregorian calendar (see link for calendar) or a common year starting on Tuesday of the 13-day slower Julian calendar (see: 1917 Julian calendar). ... ... Pfizer Incorporated (NYSE: PFE) is the worlds largest research-based pharmaceutical company[1].[1] The company is based in New York City. ...


In this production technique, which is still the major industrial route to citric acid used today, cultures of Aspergillus niger are fed on sucrose to produce citric acid. After the mold is filtered out of the resulting solution, citric acid is isolated by precipitating it with lime (calcium hydroxide) to yield calcium citrate salt, from which citric acid is regenerated by treatment with sulfuric acid. ... Flash point N/A Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Sucrose (common name: table sugar, also called saccharose) is a disaccharide (glucose + fructose) with the molecular formula C12H22O11. ... It has been suggested that Portlandite be merged into this article or section. ... R-phrases S-phrases , , , Flash point Non-flammable Related Compounds Related strong acids Selenic acid Hydrochloric acid Nitric acid Related compounds Hydrogen sulfide Sulfurous acid Peroxymonosulfuric acid Sulfur trioxide Oleum Supplementary data page Structure and properties n, εr, etc. ...

Krebs cycle

Main article: Citric acid cycle

Citric acid is one of a series of compounds involved in the physiological oxidation of fats, proteins, and carbohydrates to carbon dioxide and water. Overview of the citric acid cycle The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle, after Hans Adolf Krebs who identified the cycle) is a series of chemical reactions of central importance in all living cells that use oxygen as part... Look up chemical compound in Wiktionary, the free dictionary. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... The most fundamental reactions in chemistry are the redox processes. ... For other uses, see FAT. Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Lactose is a disaccharide found in milk. ...

This series of chemical reactions is central to nearly all metabolic reactions, and is the source of two-thirds of the food-derived energy in higher organisms. It was discovered by the Sir Hans Adolf Krebs. Krebs received the 1953 Nobel Prize in Physiology or Medicine for the discovery. The series of reactions is known by various names, including the citric acid cycle, the Krebs cycle, and the tricarboxylic acid cycle (or TCA cycle). Santorio Santorio (1561-1636) in his steelyard balance, from Ars de statica medecina, first published 1614 Metabolism (from μεταβολισμος(metavallo), the Greek word for change), in the most general sense, is the ingestion and breakdown of complex compounds, coupled... For other uses, see Chemical reaction (disambiguation). ... In biology and ecology, an organism (in Greek organon = instrument) is a living being. ... Sir Hans Adolf Krebs (August 25, 1900 – November 22, 1981) was a German, later British medical doctor and biochemist. ... Emil Adolf von Behring was the first person to receive the Nobel Prize in Physiology or Medicine, for his work on the treatment of diphtheria. ...


Food additive

As a food additive, citric acid is used as a flavouring and preservative in food and beverages, especially soft drinks. It is denoted by E number E330. Citrate salts of various metals are used to deliver those minerals in a biologically available form in many dietary supplements. The buffering properties of citrates are used to control pH in household cleaners and pharmaceuticals. Flavouring (CwE) or flavoring (AmE) is a product which is added to food in order to change or augment its taste. ... The word drink is primarily a verb, meaning to ingest liquids, see Drinking. ... For the mathematical constant see: E (mathematical constant). ... This article is about metallic materials. ... A dietary supplement is intended to supply nutrients, (vitamins, minerals, fatty acids or amino acids) that are missing or not consumed in sufficient quantity in a persons diet. ... A buffering agent adjusts the pH of a solution. ... For other uses, see PH (disambiguation). ... Pharmacology (in Greek: pharmacon is drug, and logos is science) is the study of how chemical substances interfere with living systems. ...

Relation to MSG

Citric acid is often produced from corn rather than citrus fruits themselves. As a result the protein that is hydrolyzed remains on the product and potentially freeing glutamic acid from other protein present in the food.[1] Glutamic acid (Glu, E), is the protonated form of glutamate (the anion). ...

Water softening

Citric acid's ability to chelate metals makes it useful in soaps and laundry detergents. By chelating the metals in hard water, it lets these cleaners produce foam and work better without need for water softening. Similarly, citric acid is used to regenerate the ion exchange materials used in water softeners by stripping off the accumulated metal ions as citrate complexes. Chelation (from Greek χηλή, chelè, meaning claw; pronounced ) is the binding or complexation of a bi- or multidentate ligand. ... A collection of decorative soaps used for human hygiene purposes. ... Laundry detergents are just one of many possible uses for detergents Detergent is a compound, or a mixture of compounds, intended to assist cleaning. ... The hardness of the water results in a calcification Hard water is water that has a high mineral content (contrast with soft water), usually consisting of calcium (Ca2+) and magnesium (Mg2+) ions, and possibly including other dissolved metals, bicarbonates, and sulfates. ... Ion exchange is defined as an exchange of ions between two electrolytes. ... A water softener reduces calcium or magnesium concentration in hard water. ...


Citric acid is used in the biotechnology and pharmaceutical industry to passivate high purity process piping (in lieu of using nitric acid). Nitric acid is considered hazardous to dispose once used for this purpose, while citric acid is not. This page is a candidate to be copied to Wiktionary. ... The chemical compound nitric acid (HNO3), also known as aqua fortis and spirit of nitre, is an aqueous solution of hydrogen nitrate (anhydrous nitric acid). ...

Citric acid is the active ingredient in some bathroom and kitchen cleaning solutions. A solution with a 6% concentration of citric acid will remove hard water stains from glass without scrubbing.

Citric acid is commonly used as a buffer to increase the solubility of brown heroin. Single-use citric acid sachets have been used as an inducement to get heroin users to exchange their dirty needles for clean needles in an attempt to decrease the spread of AIDS and hepatitis[1]. Other acidifiers used for brown heroin are ascorbic acid, acetic acid, and lactic acid; in their absence, a drug user will often substitute lemon juice or vinegar. For other uses, see Heroin (disambiguation). ... For other uses, see AIDS (disambiguation). ... Hepatitis (plural hepatitides) implies injury to liver characterised by presence of inflammatory cells in the liver tissue. ... This article deals with the molecular aspects of ascorbic acid. ... R-phrases , S-phrases , , , Flash point 43 °C Related Compounds Related carboxylic; acids Formic acid; Propionic acid; Butyric acid Related compounds acetamide; ethyl acetate; acetyl chloride; acetic anhydride; acetonitrile; acetaldehyde; ethanol; thioacetic acid; acetylcholine; acetylcholinesterase Supplementary data page Structure and properties n, εr, etc. ... For the production of milk by mammals, see Lactation. ... Vinegar is sometimes infused with spices or herbs—as here, with oregano. ...

Citric acid is one of the chemicals required for the synthesis of HMTD, a highly heat-, friction-, and shock-sensitive explosive similar to acetone peroxide. Purchases of large quantities of citric acid may rouse suspicion of potential terrorist activity. HMTD or Hexamethylene Triperoxide Diamine is an explosive often used in improvised explosive devices. ... Acetone peroxide Ball-and-stick model of the acetone peroxide trimer (TATP) Acetone peroxide (triacetone triperoxide, peroxyacetone, TATP, TCAP) is an organic peroxide and a primary high explosive. ...

Citric acid can be added to ice cream to keep fat globules separate, and can be added to recipes in place of fresh lemon juice as well. Citric acid is used along with sodium bicarbonate in a wide range of effervescent formulae, both for ingestion (e.g., powders and tablets) and for personal care (e.g., bath salts, bath bombs, and cleaning of grease). Flash point Non-flammable. ... Effervesence from soda. ... The name bath salts is applied to a range of soluble solid products designed to be added to a bath, either to improve cleaning, provide a medical improvement, or to improve the experience of bathing. ... A bath bomb, sometimes called a bath fizzie is a scented ball which, when placed in a full bathtub, bubbles and fizzes, scenting and colouring the bath water. ... Petro redirects here. ...

When applied to hair, citric acid opens up the outer layer, also known as the cuticle. While the cuticle is open, it allows for a deeper penetration into the hair shaft. It can be used in shampoo to wash out wax and coloring from the hair. It is notably used in the product "Sun-in" for bleaching, but is generally not recommended due to the amount of damage it causes. For the 1968 stage production, see Hair (musical), for the 1979 film, see Hair (film). ... Shampoo is a common hair care product used for the removal of oils, dirt, skin particles, dandruff, environmental pollutants and other contaminant particles that gradually build up in hair. ...

Citric acid is also used as a stop bath in photography. The developer is normally alkaline, so a mild acid will neutralize it, increasing the effectiveness of the stop bath when compared to plain water.[2] Stop bath is the second of three chemical baths usually used in processing traditional black-and-white photographic films, plates, and paper. ... Photography [fәtɑgrәfi:],[foʊtɑgrәfi:] is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or electronic sensor. ...


Citric acid is recognized as safe for use in food by all major national and international food regulatory agencies. It is naturally present in almost all forms of life, and excess citric acid is readily metabolized and eliminated from the body.

Interestingly, despite its ubiquity in the body, intolerance to citric acid in the diet is known to exist. Little information is available as the condition appears to be rare, but like other types of food intolerance it is often described as a "pseudo-allergic" reaction. // Food intolerance or food sensitivity is a negative reaction to a food that may or may not be related to the immune system or to food poisoning. ...

Contact with dry citric acid or with concentrated solutions can result in skin and eye irritation, so protective clothing should be worn when handling these materials.

Excessive consumption is capable of eroding the tooth enamel. Tooth enamel is the hardest and most highly mineralized substance of the body , and with dentin, cementum, and dental pulp is one of the four major parts of the tooth. ...

Close contact to the eyes can cause a slight burning sensation, and may cause loss of sight.

Cancer claims

There have been erroneous reports that E330 is a major cause of cancer. It is thought that this has been brought about by misunderstanding and confusion over the word Krebs. In this case, it refers to Sir Hans Adolf Krebs, discoverer of the Krebs cycle, and not the German word for cancer. Citric acid is not known to be harmful to the body when taken alone. Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ... Sir Hans Adolf Krebs (August 25, 1900 – November 22, 1981) was a German, later British medical doctor and biochemist. ...

See also

Citric acid intolerance is a rare type of food intolerance in which the body is unable to digest citric acid. ...


  1. ^ Garden, J., Roberts, K., Taylor, A., and Robinson, D. (2003). "Evaluation of the Provision of Single Use Citric Acid Sachets to Injecting Drug Users" (pdf). Scottish Center for Infection and Environmental Health.
  2. ^ http://www.silverprint.co.uk/chem4.html

External links

  Results from FactBites:
Stellar Solutions - Citric Acid Passivation (979 words)
The CitriSurf™ citric acid cleaning and passivation process is based on a new technology using safe and environmentally friendly citric acid to remove the free iron from the surface of stainless steel and chromium enrich the surface.
In addition, citric acid does not pose the environmental hazards that are present with nitric and other mineral acids.
Citric acid is the natural organic acid produced in oranges and other citric fruits, and is Generally Regarded As Safe (GRAS) for use in food products.
Citric acid - Wikipedia, the free encyclopedia (1066 words)
Citric acid exists in a variety of fruits and vegetables, but it is most concentrated in lemons and limes, where it can comprise as much as 8% of the dry weight of the fruit.
In the United Kingdom, citric acid is commonly used as a buffer to increase the solubility of brown heroin.
Citric acid is one of the chemicals required for the synthesis of HMTD; a highly heat, friction, and shock sensitive explosive similar to Acetone peroxide (also known as "Mother of Satan").
  More results at FactBites »



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