71.080.30 - Organic nitrogen compounds

This International Standard specifies a spectrometric method for the determination of the permanganate absorption number of caprolactam for industrial use. The permanganate absorption number is a measure of the oxidizable impurities in caprolactam, determined in a buffered neutral aqueous medium under fixed conditions. The method is applicable to purified caprolactam (and intermediates in the caprolactam purification process) with an alkalinity or acidity lower than 0,50 mmol/kg and a PAN value ...view more

The volatile bases are distilled in alkaline medium under specified conditions and collected in a known volume of a standard volumetric hydrochloric acid solution in the presence of an indicator. The excess of the acid is titrated with a standard volumetric sodium hydroxide solution.

The absorbance of a 50 % aqueous caprolactam solution is spectrometrically measured at a wavelength of 390 nm and an optical path length of 50 mm. The result is expressed in Hazen units by multiplying the absorbance measured by a constant factor equal to 150. This factor is derived from measurements of absorbance of diluted standard solutions of platinum-cobalt scale.

The spectrometric measurement of the absorbance of a 50 % caprolactam water solution is carried out at a wavelength of 290 nm. The absorbance, expressed in relation to an optical path length of 1 m, is given by a specified formula in which AO is the correction for the difference in absorbances of the cells; A1 is the absorbance of the test solution, and 1 is the optical path length, in centimetres, of the cell.