Potassium Bisulfate

OVERVIEW

Potassium bisulfate (poe-TAS-ee-yum BYE-sul-fate) is an odorless white crystalline solid that begins to decompose at its melting point. It is deliquescent, meaning that has such a strong tendency to absorb moisture from the air that it becomes wet and dissolves in the water it has absorbed.

HOW IT IS MADE

Potassium bisulfate is typically made by heating potassium sulfate (K₂SO₄) with sulfuric acid. The acid provides the hydrogen needed to convert the salt (K₂SO₄) to the corresponding acid salt (KHSO₄).

KEY FACTS

OTHER NAMES:

Potassium hydrogen sulfate; potassium acid sulfate

FORMULA:

KHSO₄

ELEMENTS:

Potassium, hydrogen, sulfur, oxygen

COMPOUND TYPE:

Acid salt (inorganic)

STATE:

Solid

MOLECULAR WEIGHT:

136.17 g/mol

MELTING POINT:

about 200°C (about 400°F); decomposes

BOILING POINT:

Not applicable

SOLUBILITY:

Soluble in water; decomposes in alcohol Potassium Bisulfate

COMMON USES AND POTENTIAL HAZARDS

Potassium bisulfate is used as a food additive. The compound is listed on the U.S. Food and Drug Administration's list of Generally Regarded as Safe (GRAS) list. The list contains chemicals thought to be safe for human consumption even though they have not been tested. Potassium bisulfate is used in foods as a preservative because it interferes with the growth of insects, bacteria, and fungi that cause foods to spoil. It is also used as a leavening agent in cake mixes. One of its most important uses is in the wine industry, where it is used to convert certain compounds that occur naturally in grapes into potassium bitartrate. Potassium bisulfate is also used as a flux, in the analysis of ores and silica compounds, in the manufacture of fertilizers, and in the preparation of methyl and ethyl acetate.

Potassium bisulfate is a strong irritant to human tissue. If spilled on the skin, inhaled, or ingested, it can burn tissue causing skin rashes, sore nasal passages, irritation of the throat, and damage to the eyes. Burns of the mouth and stomach may also occur. These hazards are of concern primarily to people who work directly with the compound and do not pose a threat as a food additive.

Words to Know

DELIQUESCENT

having a strong tendency to absorb moisture from the air, so that it becomes wet and dissolves in the water it has absorbed.

FLUX

a material that lowers the melting point of another substance or mixture of substances or that is used in cleaning a metal.

FOR FURTHER INFORMATION

"Agency Response Letter: GRAS Notice No. GRN 000060." U.S. Food and Drug Administration. http://www.cfsan.fda.gov/∼rdb/opa-g060.html (accessed on November 1, 2005).

"Safety (MSDS) data for potassium bisulfate." Physical and Theoretical Chemistry Laboratory, University of Oxford. http://ptcl.chem.ox.ac.uk/MSDS/PO/potassium_bisulfate.html (accessed on November 1, 2005).