Sodium bisulfate, also known as sodium hydrogen sulfate, is the sodium salt of the bisulfate anion, with the molecular formula NaHSO4. Sodium bisulfate is an acid salt formed by partial neutralization of sulfuric acid by an equivalent of sodium base, typically either in the form of sodium hydroxide (lye) or sodium chloride (table salt). It is a dry granular product that can be safely shipped and stored. The anhydrous form is hygroscopic. Solutions of sodium bisulfate are acidic, with a 1M solution having a pH of around 1.
Sodium hydrogen sulfate
Sodium acid sulfate
Bisulfate of soda
3D model (JSmol)
|E number||E514(ii) (acidity regulators, ...)|
CompTox Dashboard (EPA)
|Molar mass||120.06 g/mol (anhydrous)|
138.07 g/mol (monohydrate)
|Density||2.742 g/cm3 (anhydrous) |
1.8 g/cm3 (monohydrate)
|Melting point|| 58.5 °C (137.3 °F; 331.6 K) (monohydrate) |
315 °C (anhydrous)
|Boiling point||decomposes to Na2S2O7 (+ H2O) at 315 °C (599 °F; 588 K)|
|28.5 g/100 mL (25 °C) |
100 g/100 mL (100 °C)
|Solubility||Insoluble in ammonia|
|triclinic (anhydrous) |
|Safety data sheet||External MSDS|
|R-phrases (outdated)||R34 R37 R41|
|S-phrases (outdated)||S26 S36 S37 S39 S45|
|NFPA 704 (fire diamond)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
- NaCl + H2SO4 → HCl + NaHSO4
This step is highly exothermic. The liquid sodium bisulfate is sprayed and cooled so that it forms a solid bead. The hydrogen chloride gas is dissolved in water to produce hydrochloric acid as a useful coproduct of the reaction.
Although not of commercial interest, sodium bisulfate can be generated as a byproduct of the production of many other mineral acids via the reaction of their sodium salts with an excess of sulfuric acid:
- NaX + H2SO4 → NaHSO4 + HX ( X− = CN−, NO3−, ClO4−)
The acids HX produced have a lower boiling point than the reactants and are separated from the reaction mixture by distillation.
Hydrated sodium bisulfate dehydrates at 58 °C (136 °F) at which point it separates from the water molecule attached to it. Once cooled again, it is freshly hygroscopic. Heating sodium bisulfate to 280 °C (536 °F) produces sodium pyrosulfate, another colorless salt:
- 2 NaHSO4 → Na2S2O7 + H2O
Sodium bisulfate is used primarily to lower pH. For technical-grade applications, it is used in metal finishing, cleaning products, and to lower the pH of water for effective chlorination in swimming pools and hot tubs. Sodium bisulfate is also AAFCO approved as a general-use feed additive, including companion animal food. It is used as a urine acidifier to reduce urinary stones in cats.
In the textiles industry, it is sometimes applied to velvet cloth made with a silk backing and a pile of cellulose-based fiber (rayon, cotton, hemp, etc.) to create "burnout velvet": the sodium bisulfate, when applied to such a fabric and heated, causes the cellulose-based fibers to become brittle and flake away, leaving burned-out areas in the finished material, usually in attractive patterns.
Sodium bisulfate is the active ingredient in some granular poultry litter treatments used to control ammonia. Sodium bisulfate has also been shown to significantly reduce the concentration of Campylobacter and Salmonella in chicken houses.
Sodium bisulfate is used as a food additive to leaven cake mixes (make them rise) as well as being used in meat and poultry processing and most recently in browning prevention of fresh-cut produce. Sodium bisulfate is considered generally recognized as safe (GRAS) by the FDA. The food-grade product also meets the requirements set out in the Food Chemicals Codex. It is denoted by E number E514ii in the EU and is also approved for use in Australia, New Zealand, Canada, and Mexico. where it is listed as additive 514. Food grade sodium bisulfate is used in a variety of food products, including beverages, dressings, sauces, and fillings. It has many synonyms including bisulfate of soda, sodium acid sulfate, mono sodium hydrogen sulfate, sodium hydrogen sulfate, sodium hydrosulfate, and sulfuric acid sodium salt (1:1).
Sodium bisulfate is considered natural by the Grocery Manufacturers Association (GMA) since it is made from minerals. However, all commercially-available sodium bisulfate is produced from sulfuric acid synthesized from elemental sulfur via the contact process.
- The prefix "bi" in "bisulfate" comes from an outdated naming system and is based on the observation that there is two times as much sulfate (SO4) in sodium bisulfate (NaHSO4) and other bisulfates as in sodium sulfate (Na2SO4) and other sulfates.
- Helmold Plessen (2000). "Sodium Sulfates". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a24_355. ISBN 978-3527306732.
- John Toedt, Darrell Koza, Kathleen Van Cleef-Toedt Chemical Composition of Everyday Products p.147
- SANI-FLUSH® Powder (Discontinued), Reckitt Benckiser.
- Margo Singer (11 July 2007). Textile Surface Decoration: Silk and Velvet. University of Pennsylvania. p. 35. ISBN 978-0-8122-2000-1.
- Blake, John P. "Litter Treatment for Poultry" (PDF). aces.edu. Alabama Cooperative Extension System.
- "Campylobacter and Salmonella Populations Associated with Chickens Raised on Acidified Litter".
- "GRAS Notice 000003: Sodium bisulfate - FDA" (PDF). FDA.
- "Sodium Bisulfate - USDA" (PDF). USDA.
- "Australia New Zealand Food Standards Code - Standard 1.2.4 - Labelling of Ingredients". www.legislation.gov.au.
- "Wise Eating, Made Easy". Noshly.
- "GMA response to Natural Sodium Bisulfate" (PDF).
- "Water Acidification" (PDF).
- Ali, Hussein M.; El-Gizawy, Ahmed M.; El-Bassiouny, Rawia E. I.; Saleh, Mahmoud A. (2017-05-04). "Browning inhibition mechanisms by cysteine, ascorbic acid and citric acid, and identifying PPO-catechol-cysteine reaction products". Journal of Food Science and Technology. 52 (6): 3651–3659. doi:10.1007/s13197-014-1437-0. ISSN 0022-1155. PMC 4444905. PMID 26028748.