Chromotropes

Chromotropic acid (1,8-dihydroxy naphthalene- 3,6-disulfonic acid)[148-25-4... 

Certain dyes when appHed by the afterchrome method are oxidized prior to metal complex formation. Examples iaclude. Chromotrope EB [3567-69-9] (52) (Cl Acid Red 14 Cl 14720) (naphthionic acid — l-naphthol-4-sulfonic acid) ia which a hydroxyl group is iatroduced by oxidation at the... 

With azo dyes derived from 4,5-dihydroxy-2,7-naphthalenedisulfonic acid [148-25-4] (chromotropic acid) as the coupling component, metal complex formation occurs with the perihydroxy groups without oxidation. 

Monoarylazo and bis(arylazo) derivatives of chromotropic acid as photometric reagents. B. Bude-sinsky, Chelates Anal. Chem., 1969, 2,1-91 (178). 

Chloranils, which are formed from polychlorine phenols by heating briefly with cone, nitric acid, can be detected, without chlorine treatment, with TDM reagent, followed by heating (10 min 110°C) [3]. Phenols yield variously colored chromatogram zones (e.g. phenol mauve, chromotropic acid grey, 8-hydroxyquinoline light brown, 4-/ert-butyl-pyrocatechol red [1]). 

Part 23 Determination of formaldehyde and hexamethylenetetramine (HMTA) in food simulants In the case of HMTA, it is treated with acid and heated to release formaldehyde. Formaldehyde in simulant is determined colorimetrically by reaction with chromotropic add in the presence of sulfuric acid... 

Microsporidia (Gram-chromotrope) M. Avium complex + panel A ... 

Stradomskaya and Goncharova [99] have developed an extraction and colour development method for formic acid which should work in seawater. The sample is acidified to pH 2 and extracted with diethyl ether. After removal of the ether, the formic acid is reduced to formaldehyde and determined spectrophotometrically with chromotropic acid. A sensitivity of 1 ig/l with a normal range of 0.9 pg/1 is claimed. 

Equilibrium constants for some related complexes are given in Table XV (170). Chromotropic acid forms the most stable complexes, presumably with the formation of a strain-free 6-membered ring. 

Use of a higher temperature (280 °C) at the final stage results in more extensive hydrolysis, with the amino group also being replaced by a hydroxy group, leading to the formation of naphthalene-1,8-diol-3,6-disulphonic acid (chromotropic acid). 

Glycerol can be oxidized to formaldehyde by periodic acid and the formaldehyde measured spectrophotometrically at 570 nm after reaction with chromotropic acid, or fluorimetrically after the addition of diacetylacetone and ammonia. The chromotropic acid reagent consists of 8-dihydroxynaphthalene-3,6-disulphonic acid dissolved in 50% sulphuric acid. 

The impurities of H-acid (65), an intermediate for various synthetic dyes, include Koch s acid (66), omega acid (67), chromotropic acid (68) etc. They were determined by RP-HPLC-UVD at X 235 nm, using as mobile phase a 0.3 M aqueous solution of sodium sulfate184. 

Several color reactions were reported for heterocycbc nitramines RDX and HMX [43, 44, 53, 58]. These nitramines release formaldehyde when treated with concentrated sulfuric acid. Therefore, the use of 1,8-dihhydroxynaphthalene-3,6-disulfonic acid (chromotropic acid) in concentrated sulfuric acid — a known reagent for the detection of formaldehyde [4] — produced the expected violet-pink color. The reaction is hardly specific other compounds that release formaldehyde under similar conditions will react in the same way. 

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