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铁能与EDTA生成稳定的络合物。铁的络合滴定,目前大部分只限于碳酸盐及硅酸盐。铁矿石中高含量铁的分析,由于操作中还存在一定的困难,实际应用的并不多。本文试验用铜-PAN做为定铁间接指示剂结果满意。(一)试剂1.EDTA标准溶液(0.025M)。称9.3克乙二胺四醋酸二钠(A、R)溶于水并稀释至1升。2.硫酸铜标准溶液(0.025M)。精称分析纯硫酸铜(CuSO_4·5H_2O)6.242克溶于水(如溶液混浊可加入2-3滴硫酸使溶液澄清),并稀释至1升。EDTA标定,取配制的EDTA溶液20毫升,加pH=5醋酸-醋酸铵缓冲液(1升含250克醋酸铵及25毫升冰醋酸)10毫升,稀释体积约200毫升,加热煮沸,加0.1%PAN8～9滴,立即用硫酸铜标准液滴定至红紫色。(也可用标样标定)。
Iron can form stable complexes with EDTA. Iron complex titration, most of the current limited to carbonate and silicate. Iron ore in the analysis of high iron content, due to the operation there are still some difficulties, not many practical applications. This paper experiments with copper-PAN as a direct indicator of iron fixed results. (A) Reagents 1.EDTA standard solution (0.025M). Weigh 9.3 g of disodium ethylenediaminetetraacetate (A, R) dissolved in water and diluted to 1 liter. 2. Copper sulfate standard solution (0.025M). Accurately analyze 6.242 g of pure copper sulphate (CuSO 4 · 5H 2 O) dissolved in water (add 2-3 drops of sulfuric acid to clarify the solution if cloudy) and dilute to 1 liter. EDTA calibration, take the preparation of EDTA solution 20 ml, add pH = 5 acetic acid - ammonium acetate buffer (1 liter containing 250 grams of ammonium acetate and 25 ml of glacial acetic acid) 10 ml, diluted volume of about 200 ml, heated to boiling, plus 0.1% PAN8 ~ 9 drops, immediately with copper sulfate standard solution to magenta. (Also standard calibration).