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通过对Fe~(3+)-EDTA和FeF_3在不同pH下表观稳定常数的计算,考虑在适当pH下多量氟盐有可能定量夺取Fe~(3+)-EDTA中的铁,在形成K_3FeF_6的同时,释放出相当铁量的EDTA。实验部分 (一)主要试剂 pH6 醋酸-醋酸钠缓冲溶液。氯化锌标准溶液:0.27％和0.37％,用高纯ZnO配制,以铝和铁标准液按分析手续标定。氟化钾溶液:40％和100％,分别取200和500克KF·2H_2O于塑料瓶中,加沸水至500毫升,摇匀。 (二)分析手续甲.铝(钛)铁连测:取试液25毫升(相当50毫克试样)于300毫升锥瓶中,加3％EDTA 6毫升(铁矿加8毫升),加0.1％二甲酚橙1滴,用NH_4OH(1+1)中和至紫色,以HCl(1+1)调至刚变黄色。煮沸3～5分钟,冷水冷却,加pH6缓冲液4毫升和1％二甲酚橙3滴。以0.27％锌标准液返滴至红色。加40％KF3毫升,煮沸3～5分钟,冷却。加1％
Based on the calculation of the apparent stability constants of Fe ~ (3 +) - EDTA and FeF_3 at different pHs, it is possible to quantitatively sequester the iron in Fe ~ (3 +) - EDTA at a large amount of fluoride salts at appropriate pH. After the formation of K_3FeF_6 At the same time, the release of a considerable amount of iron EDTA. Experimental part (A) The main reagent pH6 acetate - sodium acetate buffer solution. Zinc chloride standard solution: 0.27% and 0.37%, prepared with high-purity ZnO, aluminum and iron standard solution by analytical procedures calibration. Potassium fluoride solution: 40% and 100%, respectively 200 and 500 g KF · 2H_2O in plastic bottles, add boiling water to 500 ml, shake. (B) analysis procedures A. Aluminum (Titanium) iron with test: Take the test solution 25 ml (equivalent to 50 mg sample) 300 ml conical flask, add 3% EDTA 6 ml (iron ore plus 8 ml), add 0.1 One drop of% xylenol orange was neutralized to purple with NH4OH (1 + 1) and to just yellowish with HCl (1 + 1). Boil 3 to 5 minutes, cool with cold water, add 4 ml of pH6 buffer and 3 drops of 1% xylenol orange. To 0.27% zinc standard solution back to red. Add 40% KF 3 ml, boil 3 to 5 minutes, cool. plus 1%