Fritz Feigl 1891–1971

Colour reactions of the fungicide 2,6-dichloro-4-nitroaniline are discussed. An analytical method for the determination of its residues on the surface and within the tissues of lettuce and fruit and in soil is described in detail. Work carried out to demonstrate the validity of the method is summarised and discussed.



The analysis is based on reduction to 2,6-dichloro-p-phenylenediamine, followed by oxidation, in the presence of aniline, to a blue indamine dye.

Colorimetric determination of 2,6‐dichloro‐4‐nitroaniline in plants and soil

When Bandrowski's base and azo dyes containing a p-phenylenediamine or a p-nitroaniline structure are fused with a dry mixture of sodium formate and sodium hydroxide at 210–230°C. p-phenylenediamine is formed by reductive cleavage. Under these conditions the diamine sublimes and the vapour reacts with an acetic-acid solution of aniline and alkali-metal persulphate to yield the indamine dye Phenylene Blue. This procedure may be conducted by the technique of spot test analysis and serves to detect such dyes. The detection limits are in the range 5–10 μg., as has been verified by testing thirteen pertinent compounds.

C. Costa Neto

Papers

Detection of Dyes possessing a p-Phenylenediamine or a p-Nitroaniline Structure by means of Spot Tests