In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid.

Bicarbonate serves a crucial biochemical role in the physiological pH buffering system. [] - October 2006. "Clinical correlates of pH levels: bicarbonate as a buffer."]

Chemical properties

The bicarbonate ion (hydrogen carbonate) is an anion with the empirical formula HCO3 and a molecular mass of 61.01 daltons; it consists of one central carbon atom surrounded by three oxygen atoms in a trigonal planar arrangement, with a hydrogen atom attached to one of the oxygens. The bicarbonate ion carries a negative one formal charge and is the conjugate base of carbonic acid, H2CO3; it is the conjugate acid of CO32−, the carbonate ion as shown by these equilibrium reactions.

CO32− +2 H2O ⇋ HCO3 + H2O + OH ⇋ H2CO3 +2 OH

H2CO3 +2 H2O ⇋ HCO3 + H3O+ + H2O ⇋ CO32− +2 H3O+

A bicarbonate salt forms when a positively charged ion attaches to the negatively charged oxygen atoms of the ion, forming an ionic compound. Many bicarbonates are soluble in water at standard temperature and pressure, particularly sodium bicarbonate and magnesium bicarbonate; both of these substances contribute to total dissolved solids, a common parameter for assessing water quality.

Biochemical role

Bicarbonate is an alkaline, and a vital component of the pH buffering system of the body (maintaining acid-base homeostasis). 86%-90% of CO2 in the body is converted into carbonic acid (H2CO3), which can quickly turn into bicarbonate (HCO3).

With carbonic acid as the central intermediate species, bicarbonate, in conjunction with water, hydrogen ions, and carbon dioxide forms this buffering system which is maintained at the volatile equilibrium required to provide prompt resistance to drastic pH changes in both the acidic and basic directions. This is especially important for protecting tissues of the central nervous system, where pH changes too far outside of the normal range in either direction could prove disastrous. (See acidosis, or alkalosis.)

Bicarbonate also acts to regulate pH in the small intestine. It is released from the pancreas in response to the hormone secretin to neutralize the acid chyme entering the duodenum from the stomach [ Berne & Levy, Principles of Physiology ]

Other uses

The most common salt of the bicarbonate ion is sodium bicarbonate, NaHCO3, which is used as baking soda. When exposed to an acid such as acetic acid (vinegar), sodium bicarbonate releases carbon dioxide. This is used as a leavening agent in baking.

The flow of bicarbonate ions from rocks weathered by the carbonic acid in rainwater is an important part of the carbon cycle.

Bicarbonate also serves in the digestive system. It raises the internal pH of the stomach, after highly acidic digestive juices have finished in their digestion of food. Ammonium bicarbonate is used in digestive biscuit manufacture.


In diagnostic medicine, the blood value of bicarbonate is one of several indicators of the state of acid-base physiology in the body.

The parameter "Standard bicarbonate concentration" (SBCe) is the bicarbonate concentration in the blood at a CO2 of 5.33kPa, full oxygen saturation and 37 degrees Celsius. [ [ Acid Base Balance (page 3)] ]

Bicarbonate compounds

* Sodium bicarbonate
* Potassium bicarbonate
* Calcium bicarbonate
* Ammonium bicarbonate


ee also

* Carbon dioxide
* Carbonic acid
* Carbonate
* Carbonic anhydrase
* Hard water
* Arterial blood gas

External links


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Look at other dictionaries:

  • bicarbonate — [ bikarbɔnat ] n. m. • 1825; de bi et carbonate ♦ Chim. Carbonate acide. ⇒ carbonate, sel. Cour. Bicarbonate de soude (de sodium),employé contre les maux d estomac. Adj. BICARBONATÉ, ÉE , 1861 . ● bicarbonate nom masculin Nom courant des… …   Encyclopédie Universelle

  • bicarbonaté — bicarbonate [ bikarbɔnat ] n. m. • 1825; de bi et carbonate ♦ Chim. Carbonate acide. ⇒ carbonate, sel. Cour. Bicarbonate de soude (de sodium),employé contre les maux d estomac. Adj. BICARBONATÉ, ÉE , 1861 . ● bicarbonate …   Encyclopédie Universelle

  • bicarbonate — ► NOUN 1) Chemistry a salt containing the anion HCO3 . 2) (also bicarbonate of soda) sodium bicarbonate …   English terms dictionary

  • Bicarbonate — Bi*car bon*ate, n. [Pref. bi + carbonate.] (Chem.) A carbonate in which but half the hydrogen of the acid is replaced by a positive element or radical, thus making the proportion of the acid to the positive or basic portion twice what it is in… …   The Collaborative International Dictionary of English

  • bicarbonate — (n.) 1819, from BI (Cf. bi ) + CARBONATE (Cf. carbonate) …   Etymology dictionary

  • bicarbonate — [bī kär′bən it, bī kär′bənāt΄] n. an acid salt of carbonic acid containing the monovalent, negative radical HCO3 …   English World dictionary

  • Bicarbonate — Le bicarbonate, ou hydrogénocarbonate, est un ion polyatomique dont la formule chimique est HCO3 . Le bicarbonate est nommé de par le caractère double de ses propriétés, il est à la fois acide et base appartenant à deux couples acido… …   Wikipédia en Français

  • Bicarbonate — In medicine, bicarbonate usually refers to bicarbonate of soda (sodium bicarbonate, baking soda) white powder that is common ingredient in antacids. Also, the bicarbonate level is an indirect measure of the acidity of the blood that is determined …   Medical dictionary

  • bicarbonate — noun a) the univalent anion HCO; any salt of carbonic acid in which only one of the hydrogen atoms has been replaced b) sodium bicarbonate used as a mild antacid; bicarbonate of soda …   Wiktionary

  • bicarbonate — [bʌɪ kα:bəneɪt, nət] noun 1》 Chemistry a salt containing the anion HCO3 . 2》 (also bicarbonate of soda) sodium bicarbonate …   English new terms dictionary

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