The chemical formula of
citric acid
is
C
6
H
8
O
7
. It is a weak organic acid. Citric acid is an intermediate in the acid cycle, occurring in the metabolism of all aerobic organisms. There are many metabolites produced by Aspergillus species, citric acid being one of them. It is a carboxylic acid naturally found in various fruits and vegetables, including oranges, tomatoes, and lemons.
The chemical name and structure of citric acid remain the same in both forms. It is useful in the food, beverage, and consumer goods industries. The first isolation of this organic acid was made in 1784 by Carl Wilhelm Scheele. It is a try basic acid, odourless, crystalline solid, and sour.
Citric Acid Formula
It also adds an acidic (sour) taste to foods and soft drinks. Citric acid may be a natural preservative. All aerobic organisms produce intermediates within the acid cycle as part of their metabolism. It is one of a series of compounds involved in oxidizing fats, proteins, and carbohydrates.
Molecular Formula = C
6
H
8
O
7
IUPAC name = 2-hydroxypropane -1, 2, 3-tricarboxylic acid
The Simplified molecular-input line-entry system (SMILES) = OC(=O)CC(O)(CC(O)=O)C(O)=O
Citrate is widely used as an acidifier, flavouring agent, and chelating agent. The citrate ion can also be the product of acid, salts, esters, or the polyatomic anion found in solution. For example, trisodium citrate is a salt and triethyl citrate is an ester. In the formula, citrate ion is C6H5O3−7 or C3H5O(COO)3−3.
Chemical Characteristics
The isolation of citrate occurs through its crystallization from lemon juice. It exists in both an anhydrous and monohydrate form, with the former being obtained from hot water and the latter from cold water. It dissolves easily in absolute ethanol but decomposes when carbon dioxide is lost. The citrate ion has a tendency to form complexes with metallic cations, which are highly stable due to the chelate effect. This effect is evident even with alkali metal cations. The formation of a chelate complex involving all three carboxylate groups results in 7-8 membered rings. This leads to deprotonation of the hydroxyl group, ultimately forming a more stable 5-membered ring as seen in substances like ammonium ferric citrate (NH4)5Fe(C6H4O7)2·2H2O.
Preparation of Citric Acid
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Use a pH strip to test the lemon juice. It should be around two or three on the pH scale.
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Test the solution again after adding a drop of sodium hydroxide 10% strength.
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Transfer the solution to another flask using a coffee filter. Check the new flask for solid particles.
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Add 28 g of calcium chloride to 70 ML of distilled water.
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In Step 5, combine the solutions in one beaker and heat them.
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Using a filter, extract the calcium citrate. Mix the calcium citrate with heavily diluted sulphuric acid.
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Filter the citric acid solution before storing it in a beaker.
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Heat the solution on medium heat to evaporate the water.
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Let the citric acid cool in a bowl after filtering it out.
Also Check –
Vapor Pressure Formula
Uses of Citric Acid
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Preservative and flavouring agent.
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Citric acid is used to make candies due to its sour taste in soft drinks and food.
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As part of the hard water treatment process.
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In the industrial area, it is also used to manufacture soap, detergent, electroplating, and leather tanning.
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Pharmaceutical industry preservative for storing blood.
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When used in cosmetics, citric acid removes dead skin, reduces wrinkles, and improves skin tone.
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A variety of beauty care products are available, including nail cleaners, face chemicals, shampoos, cleanser, and body washes.
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Some ice companies use it as an emulsifier to prevent fat globules from forming.
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Citric acid is used to remove limescale from the evaporator and boilers.
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Crystallization of sucrose in caramel.
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As soil and climatic conditions change, citrus acid levels in vegetables and fruits also change. Citrus acid tastes sweet and sour, whereas succinic acid tastes salty - bitter.
Also Check –
Theoretical Yield Formula
Citric Acid Characteristics
By using lemon juice, citric acid can be isolated by crystallization. It is either monohydrate or anhydrous. Monohydrate can be formed from cold water, while anhydrous can be formed from hot water. When dissolved in absolute ethanol, it decomposes and releases carbon dioxide.
The metallic cations form complexes with citrate ion, and the chelate effect occurs. Chelate complexes can be formed even with alkali metal cations. When chelate rings are formed with all three carboxylate groups, 7 and 8 members of chelate rings are formed. As a result, deprotonation of a hydroxyl group and formation of a more stable five-membered ring, (NH4)5Fe(C6H4O7)2.2H2O
The molecular weight/molar mass of citric acid is 192.124 gmole, and its density is 1.66 gcm3. The density of citric acid is important because it determines how much can be mixed in any particular substance. Its boiling temperature is 310°C and its melting temperature is 153°C.
Also Check –
Empirical Formula
Citric Acid Benefits
Due to its metallic salts, it can be used as a sequestering agent in industrial processes as well as as an anticoagulant blood preservative. It forms complexes with copper, iron, magnesium, calcium, and manganese. Because of its antioxidant properties in fats and oils, it reduces metal-catalyzed oxidation by chelating traces of metals such as iron.
A process to remove sulphur dioxide from flue gases is developed, in which citric acid is used as a scrubber. It forms a complexion that reacts with H2S to produce elemental sulphur-regenerating citrate. Plasticizers and plastic films contain citric acid esters such as triethyl, butyl and acetal tributyl esters, while monostearyl citrate is used in oils and fats as an antioxidant instead of citric acid.
