摘要: After comparing the sensitizing effect of various mixed surfactants on the chromophoric reaction of gallium （Ⅱ） with orthochlorophenylf luorone, it has been found that the mixed micelle of cetyltrimethylammonium bromide and Tween-80 is most suitable. In the presence of this mixed micelle, not only both the sensitivity and stability improve markedly, but also a wider pH range is tolerable for the colour-development. From the study on the optimum conditions for the formation of the coloured coordination compoundin the system of 《Ga （Ⅱ）——o-Chlorophenyl fluorone-catyltrimethylammo-nium bromide——Tween-80》 and its main characters, a spectrophotometricmethod, by which sensitivity and reproducibility are higher than those of ternary systems of gallium（Ⅱ） has been developed. When it is combined with the dual-wavelength method, the molar absorptivity can be improved to 2.33×10⁵ l·mol^-1·cm^-1,which is higher than that of most of other systems ever shown in the literatures; moreover the linear range is extended. From the determination of microamount of gallium in the copper minerals, the result is proved to be acceptable.