Both sodium benzoate and benzene are organic compounds composed primarily of carbon and hydrogen atoms. Despite a superficial similarity in their names, the two have nothing in common. Potassium benzoate is a preservative commonly used in food and cosmetics. Benzene is an industrial solvent and lab reagent. Its use as a gasoline additive was limited when its carcinogenic properties became known.
Potassium Benzoate Chemistry
Potassium benzoate is a relatively small molecule with a molecular weight of 160.21 g/mole. This colorless or white crystalline powder is a salt. It is easily soluble in water, where it dissociates, or breaks down, into potassium and benzoic acid. This dissociation occurs most readily when the pH is less than 4.5.
Uses and Safety
Food manufacturers use potassium benzoate to prevent the growth of mold, fungus and bacteria in the manufacture of soft drinks, juices, jellies syrups, cider, salad dressing and other foods. It is "generally recognized as safe" by the FDA. The World Health Organization reports that the acceptable daily intake of this food is 5 mg per kg. This means that a 130-pound woman could safely consume approximately 295 mg of potassium benzoate every day.
Benzene Chemistry
Benzene has six carbon atoms joined together in a ring. One hydrogen atom is bound to each carbon atom, for a total of six hydrogen atoms. This colorless liquid has a sickly sweet aroma. This gives rise to the use of the term "aromatic" to describe any benzene-like ring structure. The structure of this molecule was first elucidated by August Keluke in 1865. Benzene is used in the production of rubber, drugs, lubricants, dyes and explosives.
Benzene Dangers
Benzene is a true carcinogen that is associated with leukemia, kidney cancer and aplastic anemias. Unlike many other substances whose safety is measured in parts per million, benzene is so carcinogenic that the EPA sets the its safety limit in drinking water at 5 parts per billion. People who handle benzene in industrial settings should wear a respirator and gloves.
References
- "International Journal of Toxicology"; Final Report on the Safety Assessment of Benzyl Alcohol, Benzoic Acid, and Sodium Benzoate. B. Nair; 2001
- World Health Organization; IARC Monographs on the Evaluation of Carcinogenic Risks to Humans Overall Evaluations of Carcinogenicity; February 2008
- Web Publications; Benzene & Resonance; Edwin Thall
- Agency for Toxic Substances and Disease Registry; Toxic Substances Portal -- Benzene; March 2011
- Emerald Performance Materials: Potassium Benzoate
- American Cancer Society; Benzene; November 2010
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