Sodium citrate
Overview
 
Trisodium citrate has the chemical formula of Na3C6H5O7. It is sometimes referred to simply as sodium citrate
Sodium citrate
Trisodium citrate has the chemical formula of Na3C6H5O7. It is sometimes referred to simply as sodium citrate, though sodium citrate can refer to any of the three sodium salts of citric acid. It possesses a saline, mildly tart flavor. For this reason, citrates of certain alkaline and alkaline earth...

, though sodium citrate can refer to any of the three sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 salts of citric acid
Citric acid
Citric acid is a weak organic acid. It is a natural preservative/conservative and is also used to add an acidic, or sour, taste to foods and soft drinks...

. It possesses a saline
Saline
Saline may refer to:* Salinity, the salt content of a solution** Saline water, water containing significant concentration of salts* Soil salinity, salt content of soil* Saline , a liquid with salt content to match the human body...

, mildly tart flavor. For this reason, citrates of certain alkaline
Alkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...

 and alkaline earth metal
Alkaline earth metal
The alkaline earth metals are a group in the periodic table. In the modern IUPAC nomenclature, the alkaline earth metals are called the group 2 elements. Previously, they were called the Group IIA elements . The alkaline earth metals contain beryllium , magnesium , calcium , strontium , barium and...

s (e.g. sodium and calcium citrates) are commonly known as "sour salt" (occasionally citric acid is erroneously termed sour salt).
Sodium citrate is chiefly used as a food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

 E331, usually for flavor
Flavor
Flavor or flavour is the sensory impression of a food or other substance, and is determined mainly by the chemical senses of taste and smell. The "trigeminal senses", which detect chemical irritants in the mouth and throat as well as temperature and texture, are also very important to the overall...

 or as a preservative
Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes....

.
Encyclopedia
Trisodium citrate has the chemical formula of Na3C6H5O7. It is sometimes referred to simply as sodium citrate
Sodium citrate
Trisodium citrate has the chemical formula of Na3C6H5O7. It is sometimes referred to simply as sodium citrate, though sodium citrate can refer to any of the three sodium salts of citric acid. It possesses a saline, mildly tart flavor. For this reason, citrates of certain alkaline and alkaline earth...

, though sodium citrate can refer to any of the three sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 salts of citric acid
Citric acid
Citric acid is a weak organic acid. It is a natural preservative/conservative and is also used to add an acidic, or sour, taste to foods and soft drinks...

. It possesses a saline
Saline
Saline may refer to:* Salinity, the salt content of a solution** Saline water, water containing significant concentration of salts* Soil salinity, salt content of soil* Saline , a liquid with salt content to match the human body...

, mildly tart flavor. For this reason, citrates of certain alkaline
Alkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...

 and alkaline earth metal
Alkaline earth metal
The alkaline earth metals are a group in the periodic table. In the modern IUPAC nomenclature, the alkaline earth metals are called the group 2 elements. Previously, they were called the Group IIA elements . The alkaline earth metals contain beryllium , magnesium , calcium , strontium , barium and...

s (e.g. sodium and calcium citrates) are commonly known as "sour salt" (occasionally citric acid is erroneously termed sour salt).

Food

Sodium citrate is chiefly used as a food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

 E331, usually for flavor
Flavor
Flavor or flavour is the sensory impression of a food or other substance, and is determined mainly by the chemical senses of taste and smell. The "trigeminal senses", which detect chemical irritants in the mouth and throat as well as temperature and texture, are also very important to the overall...

 or as a preservative
Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes....

. Sodium citrate is employed as a flavoring agent in certain varieties of club soda. Sodium citrate is common as an ingredient in Bratwurst
Bratwurst
A bratwurst is a sausage usually composed of veal, pork or beef. The plural in German is Bratwürste....

, lemon-lime and citrus soft drink
Soft drink
A soft drink is a non-alcoholic beverage that typically contains water , a sweetener, and a flavoring agent...

s, such as Ting
Ting (soft drink)
Ting is a carbonated beverage popular in the Caribbean. It is flavored with Jamaican grapefruit juice , and is both tart and sweet. Ting comes in a green glass bottle, or more rarely in a green and yellow can. Like Orangina, the beverage contains a small amount of sediment consisting of grapefruit...

, Chinotto, and some Ocean Spray
Ocean Spray
Ocean Spray may refer to:* Spray from the ocean* Ocean Spray , a group of fruit growers* Ocean Spray , by the Manic Street Preachers* Holodiscus discolor, a type of flowering shrub...

 juices, contributing to their tart tastes, and can also be found in such energy drinks as Rockstar
Rockstar (drink)
Rockstar is an energy drink created in 2001. With 14% of the US market in 2008, Rockstar is a leading energy drink brand. Rockstar is based in Las Vegas...

 and Red Bull
Red Bull
Red Bull is an energy drink sold by the Austrian Red Bull GmbH, created in 1987 by the Austrian entrepreneur Dietrich Mateschitz. In terms of market share, Red Bull is the most popular energy drink in the world, with 3 billion cans sold each year. Dietrich Mateschitz was inspired by an already...

.

Buffer

As a conjugate base of a weak acid, citrate can perform as a buffering agent
Buffering agent
A buffering agent is a weak acid or base used to maintain the acidity of a solution at a chosen value. The function of a buffering agent is to prevent a rapid change in pH when acids or bases are added to the solution. Buffering agents have variable properties—some are more soluble than others;...

 or acidity regulator
Acidity regulator
Acidity regulators, or pH control agents, are food additives added to change or maintain pH . They can be organic or mineral acids, bases, neutralizing agents, or buffering agents....

, resisting changes in pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

. Sodium citrate is used to control acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

ity in some substances, such as gelatin dessert
Gelatin dessert
Gelatin desserts are desserts made with sweetened and flavored gelatin. They can be made by combining plain gelatin with other ingredients or by using a premixed blend of gelatin with additives...

s. It can be found in the mini milk containers used with coffee machines. The compound is the product of antacids, such as Alka-Seltzer, when they are dissolved in water.

Medical uses

In 1914, the Belgian
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...

 doctor Albert Hustin
Albert Hustin
Albert Hustin was a Belgian medical doctor. He was the second to successfully practice non-direct blood transfusions with sodium citrate used as an anticoagulant. Luis Agote, from Argentina, was the first doctor to practice this kind of transfusion....

 and the Argentine
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 physician and researcher Luis Agote
Luis Agote
Luis Agote was an Argentine physician and researcher. He was one of the first to perform a non-direct blood transfusion using sodium citrate as an anticoagulant...

 successfully used sodium citrate as an anticoagulant
Anticoagulant
An anticoagulant is a substance that prevents coagulation of blood. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis...

 in blood transfusion
Blood transfusion
Blood transfusion is the process of receiving blood products into one's circulation intravenously. Transfusions are used in a variety of medical conditions to replace lost components of the blood...

s. It continues to be used today in blood collection tubes and for the preservation of blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 in blood bank
Blood bank
A blood bank is a cache or bank of blood or blood components, gathered as a result of blood donation, stored and preserved for later use in blood transfusion. The term "blood bank" typically refers to a division of a hospital laboratory where the storage of blood product occurs and where proper...

s. The citrate ion chelates
Chelation
Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....

 calcium ions in the blood by forming calcium citrate
Calcium citrate
Calcium citrate is the calcium salt of citric acid. It is commonly used as a food additive , usually as a preservative, but sometimes for flavor. In this sense, it is similar to sodium citrate. Calcium citrate is also used as a water softener because the citrate ions can chelate unwanted metal...

 complexes, disrupting the blood clotting mechanism.

In 2003, Oöpik, et al., showed the use of sodium citrate (0.5 grams per kg of body weight) improved running performance over 5 km by 30 seconds.

Sodium citrate is used to relieve discomfort in urinary tract infections, such as cystitis
Cystitis
Cystitis is a term that refers to urinary bladder inflammation that results from any one of a number of distinct syndromes. It is most commonly caused by a bacterial infection in which case it is referred to as a urinary tract infection.-Signs and symptoms:...

, to reduce the acidosis seen in distal renal tubular acidosis
Renal tubular acidosis
Renal tubular acidosis is a medical condition that involves an accumulation of acid in the body due to a failure of the kidneys to appropriately acidify the urine. When blood is filtered by the kidney, the filtrate passes through the tubules of the nephron, allowing for exchange of salts, acid...

, and can also be used as an osmotic laxative
Laxative
Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...

.

It is used as an antacid, especially prior to anaesthesia, for caesarian section procedures to reduce the risks
Mendelson's syndrome
Mendelson's syndrome is chemical pneumonitis caused by aspiration during anaesthesia, especially during pregnancy.-Presentation:Mendelson's syndrome is characterised by a bronchopulmonary reaction following aspiration of gastric contents during general anaesthesia due to abolition of the laryngeal...

associated with the aspiration of gastric contents.
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