Abstract: Uranium(Ⅲ) solution is obtained electrolytically by reducing uranyl ion on mercury cathode. The effect of the addition of various aminopolycarboxylic acids (such as EDTA, DTPA, CyDTA and TTHA) and organic water-miscible solvents (such as CH3OH, C2H5OH and CH3COCH3) on the stability of ura-nium(Ⅲ) in air has been investigated.The absorption spectra of uranium(Ⅲ)and uranium(Ⅳ)in 1 mol/l and 9mol/l hydrochloric acid solutions are examined. The molar extinction coefficient of uranium(Ⅲ) is 167 1-mol-1·cm-1 in the HC1 concentration range 0. 5-4. 5mol/l and uranium (Ⅳ) practically does not interfere in the photometric determination of uranium(Ⅲ) at the wavelength of 521nm.