Chromotropic acid
Description
White crystalline material used as an analytical reagent for the detection of aldehydes. A solution of chromotropic acid dissolved in concentrated acid sulfuric acid will turn purple in the presence of aldehydes. A test using chromotropic acid in a closed enviornment to detect the offgassing of volatile aldehydes was recommended in 1994 by Zhang, Thickett, and Greene.
Synonyms and Related Terms
chromotropic acid test; 4,5-dihydroxy-2,7-napthalenedisulfonic acid; 1,8-dihydroxynaphthalene-3,6-disulfonic acid
Other Properties
Soluble in water.
The fluorescence of chromotropic acid changes with pH (colorless below 3.5, and fluorescent blue above 4.5).
| Composition | C10H8O8S2 |
|---|---|
| CAS | 129-96-4 (Anhydrous) |
| Molecular Weight | mol. wt. = 320.29 |
Hazards and Safety
Mallinckrodt Baker: MSDS
Additional Information
J.Zhang, D.Thickett, L.Greene, "Two Tests for the Detection of Volatile Organic Acids and Formaldehyde" JAIC 33(1), 1994, p. 47-53.
Authority
- The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 2298
- CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: The fluorescence of chromotropic acid changes with pH. It is colorless below pH=3.5 and above 4.5, it fluoresces blue.