Formaldehyde reaction with 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. 

Formaldehyde-chromotropic acid test Formic acid, H.COOH, is reduced to formaldehyde H.CHO by magnesium and hydrochloric acid. The formaldehyde is identified by its reaction with chromotropic acid (see Section III.24, reaction 9d) in strong sulphuric acid when a violet-pink colouration appears. Other aliphatic aldehydes do not give the violet colouration. 

A terminal 1,2-diol yields formaldehyde, whereas the carboxylic derivatives yield carbon dioxide. Several methods are available for detecting and determining these important products in reaction mixtures formaldehyde may be determined as a sparingly soluble methone, " by its highly spedlic color reaction with chromotropic acid, or polarographically conventional, manometric techniques are utilized for measurement of the carbon dioxide from carboxylic adds. 

Epoxy resins g acrylonitrile ive a positive reaction for phenol according to the Gibbs indophenol test (see Section 6.1.3) due to the presence of bisphe-nol. In contrast to the phenolic resins, however, the formaldehyde test with chromotropic acid (see Section 6.1.4) is negative. 

A reliable method for detecting Rongalite (and differentiating it from sodium hydrosulfite) is based on the detection of its formaldehyde component. This is easily accomplished by the color reaction with chromotropic acid. Details have been given elsewhere. ... 

An alcohol occasionally encountered in cases of poisoning. It is metabolized to formaldehyde and formic acid resulting in a metabolic acidosis. A number of other toxic effects can result including blindness. It can be estimated by gas-liquid chromatography or colorimetrically by oxidation to formaldehyde followed by its reaction with chromotropic acid. 

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... 

The colour produced by reaction with formaldehyde and sulphuric acid or with chromotropic acid and sulphuric acid [82,83] has been used as an identity test to differentiate various penicillins and cephalosporins. Neither... 

This method is based on a chemical reaction of chromotropic acid and free formaldehyde evaporated from the sample/standards. However, other aldehydes and ketones can also react with chromotropic acid giving colors that can interfere with the violet color. 

The formaldehyde formed in a periodate reaction is determined gravimet-rically with Dimedon, or colorimetrically with chromotropic acid, after the excess oxidant is destroyed with ethylene glycol, stannous chloride, sodium arsenite, or sodium bisulfite 221), The formic acid is generally titrated directly. Titration to pH 6.0 will measure all the formic acid present. Titration to higher alkalinities will usually measure any formic acid bound as an ester 222) but also other acidic products the end-point may be indefinite. Sucrose will give 80 to 90 % of the theoretical formic acid, and maltose and lactose similarly low values. Both formaldehyde and formic acid are attacked only extremely slowly by periodate, but light apparently accelerates an oxidation to carbon dioxide and water 223),... 

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. 

The concentration of formaldehyde in the chamber air is determined spectrophotometrically after sampling in bottles. Chromotropic acid (j or acetyl-acetone (i) were used as reagents Acetylacetone reacts more specific with formaldehyde but the reaction requires a higher temperature to be quantitive. 

Interesting calixarenes and calixarene-related compounds have been obtained in one-step reactions from 1-naphthol, from the naphthalenediol disulfonate 11, and from and the bis-phenols 13, 15, and 17. Although 2-naphthol reacts with formaldehyde to yield a simple bis-naphthol, 1-naphthol produces a mixture containing 9.6% of the symmetrical cxo-OH cyclic tetramer 10 accompanied by 5% and 16% of two other cyclic tetramers in which the naphthol residues are unsymmetrically placed in the cyclic array. When the disodium salt of 1,8-dihydroxy-3,6-naphthalenedisulfonic acid (chromotropic acid) (11) is treated with an aqueous solution of formaldehyde and the mixture is allowed either to stand at room temperature for a week or is refluxed 6 h, a high yield of the endo-OH cyclic tetramer 12 is formed. The ease with which this condensation occurs is surprising in view of the deactivating effect of the sulfonic acid groups... 

In the presenee of coneentrated sulfuric acid, chromotropic acid (1,8-dihydroxy-naphthalene-3,6-disulfonic acid) reacts with formaldehyde to give a red-violet hydroxy-diphenylmethane derivative, as shown in Eq. (2) (Eegriwe, 1937), which is soluble in acid. In the second step of the reaction, a violet quinoid oxidation product is formed with atmospheric oxygen. The concentrated sulfuric acid behaves as a catalyst for dehydration and oxidation. The absorption maximum at 580 nm is used for colorimetric detection. 

A color reaction of the methylenedioxy group is based on the well-known detection of formaldehyde (p. 215) with chromotropic and sulfuric acids (the mixture is heated over a boiling water bath for 30 min) (7, 8). 

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