FIELD: analytical methods. SUBSTANCE: hexamethylenedimaleinamide sample solution in concentrated nitric acid is consecutively treated with 1:1 mixture of concentrated nitric and acetic acids at room temperature for 30 min and then with 20 +/- 2% sodium hydroxide solution followed by photometric analysis at 400 nm. Sensitivity of determination is 5 mcg/ml and linearity of calibration graph is fulfilled within a range of 50 to 80 mcg/ml. Determination is not hindered by substances incapable of forming salts of acid form, which are not absorbing at 400 nm. EFFECT: increased sensitivity and selectivity of determination. 2 tbl
