Trisodium citrate

Trisodium citrate has the molecular formula 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, and is a mild alkali.

Sodium citrate

Names
Preferred IUPAC name Trisodium 2-hydroxypropane-1,2,3-tricarboxylate
Other names Sodium citrate Trisodium citrate Citrosodine Trisodium salt E331
Identifiers
CAS Number	68-04-2 Y 6132-04-3 (dihydrate) Y 6858-44-2 (pentahydrate) Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL1355 Y
ChemSpider	5989 Y
ECHA InfoCard	100.000.614
E number	E331iii (antioxidants, ...)
PubChem CID	6224
RTECS number	GE8300000
UNII	RS7A450LGA Y B22547B95K (dihydrate) Y
CompTox Dashboard (EPA)	DTXSID2026363
InChI InChI=1S/C6H8O7.3Na/c7-3(8)1-6(13,5(11)12)2-4(9)10;;;/h13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);;;/q;3*+1/p-3 N Key: HRXKRNGNAMMEHJ-UHFFFAOYSA-K N InChI=1/C6H8O7.3Na/c7-3(8)1-6(13,5(11)12)2-4(9)10;;;/h13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);;;/q;3*+1/p-3 Key: HRXKRNGNAMMEHJ-DFZHHIFOAL
SMILES C(C(=O)[O-])C(CC(=O)[O-])(C(=O)[O-])O.[Na+].[Na+].[Na+]
Properties
Chemical formula	Na3C6H5O7
Molar mass	258.06 g/mol (anhydrous), 294.10 g/mol (dihydrate)
Appearance	White crystalline powder
Density	1.7 g/cm3
Melting point	> 300 °C (572 °F; 573 K) (hydrates lose water ca. 150 °C)
Boiling point	Decomposes
Solubility in water	Anhydrous form:57 g/100 g H2O (25 °C) [1] Pentahydrate form: 92 g/100 g H2O (25 °C)[2]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	Irritant
NFPA 704 (fire diamond)	1 0 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1548 mg/kg (intraperitoneal, rat)[3]
Safety data sheet (SDS)	External MSDS
Related compounds
Related compounds	Monosodium citrate Disodium citrate Calcium citrate Citric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Uses

Foods

Sodium citrate is chiefly used as a food additive, usually for flavor or as a preservative. Its E number is E331. Sodium citrate is employed as a flavoring agent in certain varieties of club soda. It is common as an ingredient in bratwurst, and is also used in commercial ready-to-drink beverages and drink mixes, contributing a tart flavor. It is found in gelatin mix, ice cream, yogurt, jams, sweets, milk powder, processed cheeses, carbonated beverages, wine, and butter chicken,^[4] amongst others. Because the elements in Na₃C₆H₅O₇ spell "Na C H O", "Nacho Cheese" is a convenient mnemonic for trisodium citrate's chemical formula. ^[5]

Sodium citrate can be used as an emulsifying stabilizer when making cheese. It allows the cheese to melt without becoming greasy by stopping the fats from separating.

Buffering

Speciation diagram for a 10-millimolar solution of citric acid. The violet curve corresponds to the trisodium citrate.

As a conjugate base of a weak acid, citrate can perform as a buffering agent or acidity regulator, resisting changes in pH. It is used to control acidity in some substances, such as gelatin desserts. It can be found in the milk minicontainers used with coffee machines. The compound is the product of antacids, such as Alka-Seltzer, when they are dissolved in water.^{[citation needed]} The pH range of a solution of 5 g/100 ml water at 25 °C is 7.5 to 9.0. It is added to many commercially packaged dairy products to control the pH impact of the gastrointestinal system of humans^{[citation needed]}, mainly in processed products such as cheese and yogurt, although it also has beneficial effects on the physical gel microstructure.^[6]

Chemistry

Sodium citrate is a component in Benedict's qualitative solution, often used in organic analysis to detect the presence of reducing sugars such as glucose.

Medicine

In 1914, the Belgian doctor Albert Hustin and the Argentine physician and researcher Luis Agote successfully used sodium citrate as an anticoagulant in blood transfusions, with Richard Lewisohn determining its correct concentration in 1915. It continues to be used in blood-collection tubes and for the preservation of blood in blood banks. The citrate ion chelates calcium ions in the blood by forming calcium citrate complexes, disrupting the blood clotting mechanism. Recently, trisodium citrate has also been used as a locking agent in vascath and haemodialysis lines instead of heparin due to its lower risk of systemic anticoagulation.^[7]

In 2003, Ööpik et al. showed the use of sodium citrate (0.5 g/kg body weight) improved running performance over 5 km by 30 seconds.^[8]

Sodium citrate is used to relieve discomfort in urinary-tract infections, such as cystitis, to reduce the acidosis seen in distal renal tubular acidosis, and can also be used as an osmotic laxative. It is a major component of the WHO oral rehydration solution.

It is used as an antacid, especially prior to anaesthesia, for caesarian section procedures to reduce the risks associated with the aspiration of gastric contents.

Boiler descaling

Sodium citrate is a particularly effective agent for removal of carbonate scale from boilers without removing them from operation^[9] and for cleaning automobile radiators.^[10]

See also

• Monosodium citrate
• Disodium citrate
• Citric acid

References

1. "Sodium citrate | 68-04-2". Retrieved 14 December 2023.
2. "CRC Handbook of Chemistry and Physics". Retrieved 22 November 2013.
3. Chambers, Michael. "ChemIDplus - 68-04-2 - HRXKRNGNAMMEHJ-UHFFFAOYSA-K - Sodium citrate anhydrous - Similar structures search, synonyms, formulas, resource links, and other chemical information". chem.nlm.nih.gov.
4. "Permitted Emulsifying Salt (E331)". 5 March 2018.
5. "Make a Perfectly Creamy Cheese Sauce Without Resorting to Velveeta". Christopher Kimball’s Milk Street. Retrieved 2024-09-20.
6. Ozcan-Yilsay, T; Lee, W.-J. (2007). "Effect of Trisodium Citrate on Rheological and Physical Properties and Microstructure of Yogurt". Journal of Dairy Science. 90 (4): 1644–1652. doi:10.3168/jds.2006-538. PMID 17369204.
7. "Locking Solutions for Hemodialysis Catheters" (PDF).
8. V. Ööpik; I. Saaremets; L. Medijainen; K. Karelson; T. Janson; S. Timpmann (2003). "Effects of sodium citrate ingestion before exercise on endurance performance in well trained college runners". British Journal of Sports Medicine. 37 (6): 485–489. doi:10.1136/bjsm.37.6.485. PMC 1724692. PMID 14665584.
9. U.S. patent 3,095,862
10. "MSDS" (PDF).