摘 要:本实验通过将水泥与氯化铵混匀，用浓盐酸及浓硝酸溶样，制取水泥试液。以六次甲基四胺-铜试剂-过硫酸铵作为分离剂，加入分离剂前，滴加适量的NH3H2O和HCl。用甲基橙颜色变化来确定沉淀pH，同时把Fe、Al、Mn、Ti、Cr、Cu等离子分离除去。分别以GBHA（乙二醛缩双邻氨基酚）、铬黑T为钙镁的指示剂，在pH=12.6的氢氧化钠-硼砂和pH=10的氨水-氯化铵缓冲条件下，EDTA容量法连续滴定，由于Fe3+、Al3+、Cu2+、Ni2+等离子封闭铬黑T，故在滴定镁时残留的痕量金属离子用三乙醇胺掩蔽，另外该方法移取待测溶液后加入抗坏血酸稳定pH，经本方法脱铁铝钛除锰的滴定终点易观察，得到了满意的滴定效果，适合多种金属离子存在的试液中钙镁的测定。
该法氧化钙的质量分数为59.30%，RSD为0.04%，氧化镁的质量分数为2.75%，RSD为1.08%，将分离剂改为尿素、氨水沉淀分离后，在相同条件下，同样用EDTA滴定，三种方法的测定结果为：氧化钙的质量分数分别为57.07%、58.78%，RSD分别为0.13%、0.06%；氧化镁的质量分数分别为3.09%、2.97%，RSD分别为1.29%、1.37%。将滴定结果分析对比发现：三种方法中本法的滴定突变明显，六次甲基四胺、铜试剂联合沉淀法分离操作，可以让测定的干扰元素少，所测得的结果更接近标准值。
关键词:六次甲基四胺；铜试剂；过硫酸铵；沉淀；对比
ABSTRACT:This experiment passed to mixing cement and ammonium chloride,dissolved samples with strong hydrochloric acid and strong nitric acid,maked cement test solution.Hexamethylene Tetramine and DDTC and (NH4)2S2O8 was as separating agent,before joined separating agent,afterwards dropwise added an appropriate amount of NH3H2O and HCl.Determine the precipitation pH with methyl red color changes,at the same time,Al,Fe,Mn,Ti,Cu ecs was separated and removed.To GBHA or Chromium Black T as the indicator of calcium and magnesium.In pH=12.60 NaOH–borax and pH=10 NH3H2O-NH4Cl buffer conditions,EDTA capacity method continuously titrated the liquor.Because Fe3+,Al3+,Cu2+,Ni2+ esc closed Chromium Black T,so when titrated the magnesium,the residual trace metal ions sheltered by triethanolamine .In addition,after removed liquor in this method,joined ascorbic acid to steadying pH.Iron and aluminum and titanium and manganese took off by this method,titration end was easily observed,the titration effect satisfied.It suitabled for the determination of calcium magnesium when various metal ions exists in the test solution.
By using the methods,quality score of the CaO was 59.30%.RSD was 0.04%.Quality score of the MgO was 2.75%,RSD was 1.08%.Taked the precipitator instead Carbamide or NH3H2O,after precipitation and separated.Under the same conditions,also with EDTA titration,determination result.Quality score of CaO was respectively 57.07%,58.78%.RSD was respectively 0.13%,0.06%.Quality score of MgO was respectively 3.09%,2.97%.RSD was respectively 1.29%,1.37%.Analysed and contrasting the titration results,in three methods,titration mutations of the method was more obvious,separated operation by Hexamethylene Tetramine and DDTC joint precipitation,couled let the determination of the interference element less.The measured results more close to standard values.
Key words:Hexamethylene Tetramine;DDTC;(NH4)2S2O8;precipitate;comparison
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