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新显色剂DBN-偶氮氯膦在pH 1～3的条件下,各稀土元素均可显色,最大吸收在640 nm附近,摩尔吸光系数为(6.75～12.1)×10~4升·摩尔~(-1)·厘米~(-1),可用于测定稀土总量。提高酸度,在0.5～4N盐酸介质中,钇组稀土基本上不显色,而铈组稀土的吸光度仍基本不变,可用于测定铈组稀土元素。在0.5N盐酸和适量草酸、磷酸存在时,一方面抑制了钇组稀土元素的显色,同时又消除了大量铁、镍、铬、铝、钼(Ⅵ)、铋、铜等元素的干扰,方法用于直接测定各种低合金钢和稀土球铁中的微量铈组稀土元素,获得满意结果。
The new chromogenic reagent DBN-chlorophosphonazo at pH 1 ~ 3 under the conditions of each rare earth element can be color, the maximum absorption at 640 nm near the molar extinction coefficient (6.75 ~ 12.1) × 10 ~ 4 liters · mole ~ (-1) cm ~ (-1), can be used to determine the total amount of rare earth. Raise the acidity, in the 0.5 ~ 4N hydrochloric acid medium, the rare earth yttrium group basically does not develop color, while the cerium group rare earth absorbance is still basically the same, can be used for the determination of cerium rare earth elements. In the presence of 0.5N hydrochloric acid and appropriate amount of oxalic acid and phosphoric acid, it inhibits the color development of rare earth elements in the yttrium group while eliminating the interference of a large amount of iron, nickel, chromium, aluminum, molybdenum (Ⅵ), bismuth and copper, The method was applied to the direct determination of trace cerium rare earth elements in various low alloy steels and rare earth ductile irons and obtained satisfactory results.