Benzoic acid

Happy Holidays!
December 21, 2020
Use me to make a holiday snow globe.
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Image of Benzoic acid

Benzoic acid, the simplest benzene-based carboxylic acid, has been known since the 16th century. One of its discoverers was the legendary clairvoyant Nostradamus. Its most common natural source is gum benzoin, a resin found in the bark of trees of the genus Styrax.

Most benzoic acid produced today is synthetic. Its first industrial synthesis was the hydrolysis of benzotrichloride to calcium benzoate, followed by acidification. This method has been completely displaced by the air oxidation of toluene, which avoids the problem of product contamination with chlorinated byproducts.

Many processed foods contain benzoic acid or one of its salts as a preservative. The acid inhibits the growth of bacteria, molds, and yeasts; it works best when the food has an acidic pH value. Benzoic acid also is often found in topical antifungal preparations.

Why is benzoic acid our December holiday molecule? It’s the white stuff predominantly used to mimic snowflakes in snow globes. For a holiday project, you might want to create your own snow globe by using the procedures developed by Steve Spangler Science or Science with Mrs. Pittenger. Benzoic acid is readily available from Amazon and other vendors.

Benzoic acid hazard information

Hazard class*Hazard statement
Skin corrosion/irritation, category 2H315—Causes skin irritation Chemical Safety Warning
Serious eye  damage/eye irritation, category 1H318—Causes serious eye damage Chemical Safety Warning
Specific target organ toxicity (lungs), repeated exposure, category 1H372—Causes damage to organs (lungs) through prolonged or repeated exposureChemical Safety Warning
Hazardous to the aquatic environment, acute hazard, category 3

H402—Harmful to aquatic life

*Globally Harmonized System of Classification and Labeling of Chemicals.  
Explanation of pictograms.

MOTW update: September 25, 2023

Benzoic acid1 is the simplest aromatic carboxylic acid and a commonly used preservative in foods and a snowflake mimic in holiday snow globes.

This past August, Yifan Meng, Richard N. Zare*, and Elumalai Gnanamani* at Stanford University (CA) and the Indian Institute of Technology Roorkee reported a catalyst-free method for producing phenol from benzoic acid. They electrosprayed ≈10-μm microdroplets of the acid dissolved in water into a chamber (e.g., a mass spectrometer port) to realize a calculated yield of ≈4.7%. The method has yet to be scaled up.

1. CAS Reg. No. 65-85-0.

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Benzoic acid fast facts

CAS Reg. No.65-85-0
Benzoic acid
Empirical formulaC7H6O2
Molar mass122.12 g/mol
AppearanceWhite crystals
Melting point122 ºC 
Water solubility3.4 g/L
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