The colorimetric estimation of formaldehyde by means of the Hantzsch reaction

Abstract

The reagent soln. consists of ammonium acetate (2[image]), acetic acid (0.05[image]) and acetylacetone (0.02[image]). This is mixed with an equal vol. of soln. containing not more than 8 mg. of formaldehyde and after standing, the yellow color (due to diacetyldihydrolutidine, DDL) is estimated in a photoelectric colorimeter with deep-blue filter (absorption max. at 412 m[mu]). Reaction is 99% complete in 5 hrs. at 20[degree], 40 mins. at 37[degree], and 5 mins. at 58[degree]). The reaction can also be used for the detection of formaldehyde but it should be realized that the components of the reagent are volatile and that DDL crystals are strongly fluorescent under soft u.-v. Acetaldehyde in the same concn. gives about 1% interference. Acetone, chloral, fural and glucose do not interfere, amines interfere slightly and periodate, sulfate, strong oxidizing agents and daylight destroy DDL.