在光度法测定稀土的研究中,以变色酸双偶氮衍生物作为显色剂在国内外已有许多报道。近来,三溴偶氮胂作为一种高灵敏度的新型显色剂亦可直接用于测定稀土总量。本文将此显色剂用于测定球墨铸铁及低合金钢中的稀土总量。灵敏度高,发色迅速,生成的络合物稳定,可测定含稀土总量0.001～0.x％的钢铁试样。本法简便快速且准确,可用于日常分析。 In the spectrophotometric determination of rare earths, chromogenic acid disazo derivatives as chromogenic agents have been reported at home and abroad. Recently, tribromoarsenazo as a high sensitivity of the new color reagent can also be used directly for the determination of the total amount of rare earth. This color reagent for the determination of ductile iron and low alloy steel in the total amount of rare earth. High sensitivity, rapid color development, the stability of the resulting complex can be determined with the total amount of rare earth 0.001 ~ 0.x% of the steel samples. This method is simple, fast and accurate and can be used for routine analysis.