[Colorimetric cleck of the working dilutions of disinfectants on an aldehyde and phenol basis (author's transl)].

The applicability of 2 colour reactions were tested for the monitoring of the working concentration of disinfectant solutions containing aldehyde or phenol. The red coloration of Schiff's acid solution (Schiff's reagent to aldehydes) can be used with limitations. The formation of a red dye by the reaction of phenols with 1-phenyl-2,3-dimethyl-4-amino-pyrazolone-(5) in the p-esence of alkali and potassium hexacyano-ferrate (III) is unequivocal and is not influenced by contaminations in the water. Evaluation is made in either case by comparison with standard dilutions of the respective commercially available preparation. The samplest procedure for this a visual colour comparison in test tubes with calibration spectrum. Pyrazolone dye can be analysed photometrically. Thus this colour reaction can be regarded as an analytic method of satisfactory accuracy. A frequent monitoring of the disinfectant concentrations by means of simple chemical procedures is expected to help limit the improper use of disinfectants and to check hospital infections.