The work of detecting trivalent antimony with the aid of 4,5-dihydroxyAuorescein (gallein), as proposed by Wang Kuei, has been extended to quantitative determination.The substance formed is insoluble in many organic solvants and is only slightly soluble in water.When 0.3 ml of 0.5% sulfonated castor oil is added to the water solution, it becomes stable even at 40°.