Phase equilibria in the neonol AF 9-10 – water system were studied using the visual-polythermal method. Value of lower critical dissolution temperature was determined (68°C). In order to assess the extraction capacity of system, the distribution of number of organic reagents was studied. It was found that increase in reagent hydrophilicity leads to decrease in its distribution coefficient. An extraction-spectrophotometric method for the determination of 1,2–2,4 mg/l nickel with 4-(2-pyridylazo) resorcinol (PAR) in the neonol AF 9-10 – water system has been proposed. It was found that ratio of nickel : PAR in the complex compound is 1: 2.