复杂钴物料中钴的滴定分析          下载免费PDF全文

袁威  刘维理 《岩矿测试》2003,22(3):235-236

实验表明,钴试样经HCl分解后,在pH1～2时,通过硫氰酸铵-结晶紫-H2O浮选将Co2+与Ni2+、Mn2+、Fe3+、Al(Ⅲ)等元素分离,硫脲掩蔽Cu2+以消除干扰,用EDTA溶液络合滴定Co。方法用于钴试样中Co的分析,结果与铈量法相符,对于w(Co)为3%～35%的试样,4次测定的相对标准偏差<2%。  相似文献   

A Revised Analytical Method for HCO₃^- and CO₃^2-Determinations in Geothermal Waters: An Assessment of IAGC and IAEA Interlaboratory Comparisons     

Mahendra P. Verma 《Geostandards and Geoanalytical Research》2004,28(3):391-409

A statistical evaluation of the results of HCO₃^‐ determinations in geothermal waters during the interlaboratory comparison programmes of the International Association of Geochemistry and Cosmochemistry (IAGC) and International Atomic Energy Agency (IAEA) indicated that the analytical uncertainty increases with decreasing concentration of HCO_3‐ and was ? 25% for 50 μg ml^‐1 and ? 60% for 25 μg ml^‐1 of HCO₃^‐. The analytical method (Method 1) used by chemists and hydrologists works well for waters containing carbonic alkalinity, whereas Method 2 used by geochemists is conceptually incorrect. A stepwise comparison between the theoretical and experimental titration results for a given concentration Na₂CO₃ (0.0988 mol l^‐1) solution was performed to understand the limitations of the titration method for geothermal water analysis. Backward titration from the carbonic acid equivalence point (H₂CO₃EP) to the original pH after CO₂ removal, as had been practised earlier in the geothermal industry, in order to estimate the contribution of silicic and boric alkalinities to the total alkalinity, is incorrect because the amount of standard base (NaOH) added is equivalent to silicic and boric alkalinities plus some OH^‐ alkalinity. In a Na₂CO₃ solution, the added NaOH is equivalent to OH^‐ alkalinity only. Backward titration is only needed from the forward titration end point to the H₂CO₃EP in order to correct the total alkalinity for the excess of standard acid (HCl) added during the forward titration. In the case of a Na₂CO₃ solution, the H₂CO₃EP, after removal of CO₂ during the forward titration, is at pH = 7, not at pH = 4.5 (3.8) as has been considered in literature. Similarly, the liberation of CO₂ during titration occurs well before the point expected theoretically and it is less for shorter titration time. The revised procedure for the determination of carbonic species concentration is presented and illustrated for a water sample from Alchichica Lake, Puebla, Mexico.  相似文献   

Buffering Mechanisms in Acidic Mining Lakes – A Model-Based Analysis     

Oliver Totsche  Rosemarie Pöthig  Wilfried Uhlmann  Heike Büttcher  Christian E.W. Steinberg 《Aquatic Geochemistry》2003,9(4):343-359

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An Improved Procedure for the Determination of Ferrous Iron Mass Fraction in Silicate Rocks Using a Schlenk Line‐Based Digestion Apparatus to Exclude Oxygen          下载免费PDF全文

Dingshuai Xue  Hongyue Wang  Yanhong Liu  Liewen Xie  Ping Shen 《Geostandards and Geoanalytical Research》2017,41(3):411-425

Precise and accurate determination of ferrous iron mass fraction in silicate rocks and geological reference materials is still a significant challenge due to the labile nature of the analyte. Here, we report a modified and improved procedure for the determination of ferrous iron mass fraction, capable of yielding moderately accurate and highly precise results in a relatively shorter time than before. This modified technique requires a more convenient operational procedure than the classical method. A sample digestion apparatus was designed that included a Schlenk line to expel air in order to prevent oxidation. The advantages of this procedure over the classical procedure are shorter process flow, higher efficiency and absence of an additional redox indicator. The composition of the acid matrix used to dissolve the samples as well as the incubation temperature and time was investigated. Comparative data for twenty‐one reference materials are reported, with five of them reported for the first time by the Schlenk line procedure. A series of experiments were carried out to identify and minimise the main source of error. In addition, the possibility of eliminating the reducing substances before digestion, by pretreatment of the sample by cold 10% methanolic bromine, was also studied.  相似文献   

2-（5-氯-2-吡啶偶氮）-5-二乙基氨基酚作络合滴定指示剂测定锌     

李山  刘根起 《岩矿测试》2006,25(1):95-96

对2-（5-氯-2-吡啶偶氨）-5-二乙基氨基酚（5-Cl-DEPAP）作锌的络合滴定指示剂进行了实验。在pH5．5的HAc—NaAc介质中，以5-Cl-DEPAP作指示剂，EDTA标准溶液滴定锌，溶液颜色由紫红色变为亮黄色，终点变化敏锐，易于观察，锌量在0-25mg与EDTA消耗量成正比。方法用于化学试剂和铝合金中锌的测定，5次测定的RSD小于0．1％。结果表明，5-Cl-DEPAP符合络合滴定对指示剂的基本要求，扩大了该试剂的应用范围。  相似文献   

高浓硫酸盐溶液中氯离子汞量法的改进     

王波  冉广芬  朱广琴  薜园  李园 《盐湖研究》2014,(3):26-28

结合标准加入法,对高浓硫酸盐样品中低浓度氯离子测定的经典汞量法进行了改进。实验证实,改进后的汞量法能更好地用于高浓硫酸盐样品中低浓度的氯离子定量测定,具有终点颜色突变明显,测定结果准确可靠,实验操作十分简便,有利于节约实验时间和成本等优点。  相似文献   

金属矿中铜含量滴碘法快速测定     

吴剑雄 《福建地质》2012,31(1):95-99

通过调节pH值,加入氟化氢铵消除铁的干扰,用硫代硫酸钠滴定碘,淀粉溶液做指示剂等方法。探讨了快速滴碘法在金属矿中铜含量分析的应用,方法快速易掌握,结果准确。适用于金属矿中铜的测定。  相似文献