EDTA滴定法测定萤石中氟化钙含量的方法改进

建立了EDTA滴定法测定矿石中氟化钙的方法。引入了钙乙酸为溶解试样的溶剂,溶解样品中的碳酸钙,同时,通过同离子效应减少氟化钙的溶解度。实验中探究了钙离子的浓度与氟化钙溶解度的关系,通过对比实验确定选择了含钙乙酸的最佳浓度(10g/L)。同时,对实验中的其他条件也进行了相应的探究与优化,确定最佳实验条件为:最小称样量为0.5g,洗涤沉淀用水量为50mL左右,第二次过滤时的洗涤次数为8～10次,滴定时加入氢氧化钾的量为20mL。方法的精密度(0.10%)和准确度(0.08%)皆能满足实验要求。     

EDTA滴定法测定萤石中氟化钙含量的方法改进

建立了EDTA滴定法测定矿石中氟化钙的方法。引入了钙乙酸为溶解试样的溶剂,溶解样品中的碳酸钙,同时,通过同离子效应减少氟化钙的溶解度。实验中探究了钙离子的浓度与氟化钙溶解度的关系,通过对比实验确定选择了含钙乙酸的最佳浓度(10g/L)。同时,对实验中的其他条件也进行了相应的探究与优化,确定最佳实验条件为:最小称样量为0.5g,洗涤沉淀用水量为50mL左右,第二次过滤时的洗涤次数为8～10次,滴定时加入氢氧化钾的量为20mL。方法的精密度(0.10%)和准确度(0.08%)皆能满足实验要求。     

Determination of fluoride ions by titration with aluminum chloride to a preset potential

A procedure is proposed for determining fluoride ions based on titration with an aluminum chloride solution to a fixed potential. The procedure allows for the significant reduction of the determination error for fluoride ions due to the error of measuring the potential in comparison with direct potentiometry. The applicability of the procedure is confirmed by the results of determining fluoride ions in mixtures modeling the composition of Poles’e fluorinated cooking salt.     

电感耦合等离子体原子发射光谱(ICP-AES)法与EDTA滴定法联用测定含白云岩矿石中氟化钙

氟化钙的测定目前较多采用的是GB/T5195.1-2017和DZG93-05两种方法,前者测定范围≥60%,后者测定范围>3%。两种方法各有优缺点,然而却都无法满足矿石中含有白云岩时的测定。近年来,青海省地勘局大力探寻萤石矿,各矿区矿石组成、矿床类型各不相同,且氟化钙品位高低不一,尤其是青海省海西州喀雅克登矿区中常见萤石矿与白云岩共存,直接采用国家标准方法,测定结果偏高,行业标准方法的精密度和准确度也很难达到要求。本文对方法进行优化,准确称量样品0.2000g至50mL的锥形瓶中,加入10mL含钙冰乙酸(1+9),瓶口放置φ40mm的短颈漏斗,在控温电热板上100℃加热40min,取下过滤,残渣放回原锥形瓶,加入20mL混合酸,瓶口放置漏斗,于控温电热板上150℃微沸30min,将溶液转移至100mL比色管中,摇匀,澄清。在Ca 317.933 nm处,使用电感耦合等离子体原子发射光谱法(ICP-AES)测定氟化钙。根据ICP-AES的测定结果,将氟化钙质量分数大于15%的样品用EDTA滴定法再次测定。按照实验方法测定喀雅克登矿区实际样品,两种方法测定结果的相对标准偏差(RSD,n=11)分别为1.86%和0.77%,加标回收率为97.9%～102.2%,可满足含白云岩矿石中氟化钙的准确测定。     

Determination of fluoride by two-phase titration with triphenyltinchloride and X-ray fluorescence spectrometric end-point determination

Summary Fluoride can be precisely and accurately determined in the presence of Al(III) by the two-phase titration with triphenyltinchloride and X-ray fluorescence spectrometric end-point determination. The end-point X_eq is calculated from the coefficients of the two regression linesY (X) andY (X) obtained for two-phase mixtures with an excess of Sn and F, respectively. The relative standard deviation of the equivalence point determination is better than 0.5%, if the total concentrationY=[Sn]_ot of tin in the organic phase (1-octanol) is determined for mixtures well mixed over night at 25° C. Either the volume or the mass ratio of the aqueous fluoride and organic tin solutions may be used as the independent variable (X=V _F/V _Sn orm _F/m _Sn). F^– must be released by complexation of Al(III) with cyclohexane-diamino-tetraacetate. The correlation between the releasing power of ligands and the quality of end-point determinations and also the role of chloride, present in the aqueous phase, are discussed in detail. The solubilities of the product Ph₃SnF and the titrating substance Ph₃SnCl are 1.67·10^–4 M and 0.1497M, respectively, in pure 1-octanol at 25° C. The solubility of Ph₃SnF in the aqueous phase mostly used was 1.7·10^–5 M at 25· C.

---

Fluoridbestimmung durch Zweiphasentitration mit Triphenylzinnchlorid und röntgenfluoreszenz-spektrometrische Endpunktbestimmung

Zusammenfassung Fluorid kann in Gegenwart von Al(III) durch Zweiphasen-Titration mit Triphenylzinnchlorid und röntgenfluoreszenz-spektrometrische Endpunktbestimmung präzis und genau bestimmt werden. Der Endpunkt X_eq wird aus den Regressionskoeffizienten der beiden GeradenY (X) undY (X) berechnet, welche für einen überschuß von Sn bzw. F im Zweiphasensystem erhalten werden. Die relative Standardabweichung des Äquivalenzpunktes ist besser als 0,5%, falls die totale ZinnkonzentrationY=[Sn]_ot in der organischen Phase (1-Octanol) für Mischungen bestimmt wird, welche über Nacht bei 25° C intensiv gemischt werden. Als unabhängige VariableX kann entweder das Volumen-(X=V _F/V _Sn) oder das Massenverhältnis (X=m _F/m _Sn) der wässerigen Fluoridlösung und der organischen Zinnlösung benützt werden. F^– muß durch Komplexierung von Al(III) mit Cyklohexan-diamino-tetraacetat freigesetzt werden. Die Beziehung zwischen dem Komplexierungsvermögen der Liganden und der Qualität der Endpunktbestimmungen sowie die Rolle des in der wässerigen Phase anwesenden Chlorides werden ausführlich diskutiert. Die Löslichkeit des Produktes Ph₃SnF bzw. des Titrationsmittels PhsSnCl ist 1,67·10^–4 bzw. 0,1479M in reinem 1-Octanol bei 25° C. Die Löslichkeit von Ph₃SnF in der meistverwendeten wässerigen Phase beträgt 1,7·10^–5 M.

     

Oxygen determination in calcium fluoride by deuteron activation analysis

Oxygen at trace level in calcium fluoride was determined by instrumental deuteron activation analysis based on the ¹⁶O(d,n)¹⁷F reaction. The irradiations were performed with 2.5 MeV deuterons for 60 s at currents ranging from 300 to 500 nA. The results obtained for powders and single crystals were compared. Received: 25 October 1999 / Revised: 23 November 1999 / Accepted: 23 November 1999     

Oxygen determination in calcium fluoride by deuteron activation analysis

Oxygen at trace level in calcium fluoride was determined by instrumental deuteron activation analysis based on the 16O(d,n)17F reaction. The irradiations were performed with 2.5 MeV deuterons for 60 s at currents ranging from 300 to 500 nA. The results obtained for powders and single crystals were compared.     

Determination of fluoride with thorium nitrate by catalytic titration

Amperometry, constant-current potentiometry and spectrophotometry were used to follow the course of catalytic titrations of fluoride and silicofluoride with thorium nitrate. The hydrogen peroxide-iodide system was used as the indicator reaction. Titrations were performed in 50% ethanolic acetate buffer, pH 3.6. Amounts of 3.70-6.85 mg of ammonium fluoride, 5.53-10.79 mg of potassium fluoride and 4.34-8.41 mg of sodium silicofluoride were determined with a maximum average deviation of 0.9%. The results obtained are in good agreement with those of comparable methods.     

The potentiometric titration of fluoride without fluoride ion-selective electrodes

Graphite and platinum sensors were investigated as indicators in the potentiometric titration of fluoride vs lanthanum(III) and thorium(IV). In every case a partially nonaqueous medium yielded larger breaks than in aqueous solution, similar to the fluoride electrode. All the sensors yielded endpoint breaks which were smaller than those obtained with a fluoride ion-selective electrode. The largest breaks were obtained with the vitreous carbon, pyrolytic graphite, and platinum sensors. Conditioning in neutral permanganate solution significantly enhanced the breaks for all types of graphite, except vitreous carbon. The break obtained with the platinum electrode can be enhanced by application of a polarizing current of 2.0 μA in the reducing direction.     

The determination of copper by complexometric titration with ethylenediaminetetraacetic acid

A method has been developed for the determination of cupric copper by complexometric titration with ethylen.ediaminetctraacetic acid. The titrations were followed potentiometrically, and were effected at pH 5–6 in the presence of an ammonium acetate buffer. Interfering metals such as ferric iron, aluminium, cadmium, zinc, manganese, nickel, cobalt and lead must be removed by a preliminary separation.     

Rapid determination of magnesium in the presence of calcium and phosphate by titration with cdta

A method is presented for the accurate determination of magnesium in phosphate rock and phosphoric acid down to 0.03% magnesium oxide in the presence of 0–70% phosphorus pentoxide by titration with cyclohexanediaminetetraacetic acid (CDTA). Interference from heavy metals for which inaccurate empirical corrections have previously been made in the combined magnesium and calcium titration are linearly and unequivocally determined and subtracted from the combined titration. Magnesium oxide is determined in less than 20 min after sample digestion for Ca: Mg ratios from 1:9 to 850:1.     

Gradient flow titration for the determination of fluoride ion in natural waters

The determination of fluoride ions in water samples was accomplished by using a gradient flow titration. A standard commercial combined electrode is used in a cell configuration that combines the gradient chamber and the electrode in a single unit. The methodology developed gives results with a relative standard deviation of about 3%. The average recoveries after spiking natural samples with fluoride are in the range 100–102%. The method was used successful in determining the fluoride concentration in water samples.     

Direct potentiometric titration of chloride and fluoride ions in reversed micelles of an ethoxylated surfactant

The possibility of the potentiometric titration of Cl^– and F^– ions directly in reversed micelles of the ethoxylated surfactant (Neonol APh₉-4) in n-decane is shown. The potential change of the indicator electrode (silver chloride and lanthanum fluoride) only depends on the ion concentration in the aqueous pseudophase of the reversed micelles and is independent of the aqueous phase concentration in n-decane in the region of concentrations from 4 to 0.2 vol %. The determination of the micelle size of Neonol APh₉-4 in the precipitation titration of Cl^– and F^– ions by photon correlation spectroscopy showed the formation of nanoparticles of AgCl and LaF₃ of dimensions limited by original micelle size (r_hd = 6 to 11 nm). The growth of AgCl and LaF₃ nanoparticles was studied at a shortage and excess of the titrant and in the point of equivalence. Received: 23 April 1999 / Revised: 15 July 1999 / Accepted: 19 July 1999     

Computer-controlled potentiometric determinations,illustrated by the determination of uranium,fluoride and chloride

Summary The computer system described is suitable for automation of many operations in a classical (wet) analytical laboratory. Programs and procedures are given for high-accuracy redox titrations (e. g. the determination of uranium) and for determination of F- and Cl-by means of ion-selective electrodes.

---

Zusammenfassung Ein Computersystem wurde beschrieben, das sich für die Automatisierung analytischer Verfahren eignet. Programm und Arbeitsweise für Redox-Titrationen höchster Präzision (z. B. die Bestimmung von Uran) und für Bestimmungen von Fluorid und Chlorid mittels ionen-selektiver Elektroden wurden angegeben.

---

---

Presented at the International Symposium on Microchemical Techniques 1977, Davos, May 1977.     

Direct potentiometric titration of chloride and fluoride ions in reversed micelles of an ethoxylated surfactant

The possibility of the potentiometric titration of Cl^– and F^– ions directly in reversed micelles of the ethoxylated surfactant (Neonol APh₉-4) in n-decane is shown. The potential change of the indicator electrode (silver chloride and lanthanum fluoride) only depends on the ion concentration in the aqueous pseudophase of the reversed micelles and is independent of the aqueous phase concentration in n-decane in the region of concentrations from 4 to 0.2 vol %. The determination of the micelle size of Neonol APh₉-4 in the precipitation titration of Cl^– and F^– ions by photon correlation spectroscopy showed the formation of nanoparticles of AgCl and LaF₃ of dimensions limited by original micelle size (r_hd = 6 to 11 nm). The growth of AgCl and LaF₃ nanoparticles was studied at a shortage and excess of the titrant and in the point of equivalence.