Volumetric determination of calcium and magnesium with ethylenediaminetetraacetic acid in the presence of phosphate

The authors have developed a rapid and accurate volumetric method for the determination of small quantities of calcium and magnesium with EDTA in the presence of phosphate.     

Complexometric titration of calcium in the presence of larger amounts of magnesium

A simple and accurate titrimetric determination of calcium in the presence of larger amounts of magnesium is proposed. Calcium is extracted into a small volume of organic solvent as its glyoxal-bis(2-hydroxyanil) complex, and the calcium is titrated with EGTA. The end-point is sharp, and occurs when the red colour of the organic layer vanishes. This method has been successfully applied to the determination of calcium in sea-water with an error less than 0.1%.     

Rapid determination of magnesium and calcium hardness in water by ion chromatography

Magnesium(II) and calcium(II) in hard water are separated by ion chromatography and detected spectrophotometrically after a post-column reaction with arsenazo-I at pH 10. No sample dilution or pretreatment is needed, and the separation is complete in 3 min. Linear calibration plots are obtained in the 2–400 mg l^?1 range. Many actual water samples from a variety of geographical locations were analysed and the results were compared with those obtained by EDTA titration. The advantages of the chromatographic method over titration are summarized.     

Microdetermination of fluoride in the presence of phosphate by potentiometric titration

Summary A method for the microdetermination of fluoride in the presence of phosphate is described. Up to a 10-fold excess of phosphorus (as phosphate) can be tolerated. Phosphate is adsorbed on zinc oxide which is added in excess and need not be removed prior to titration of fluoride. Fluoride is determined potentiometrically with 0.02M lanthanum(III) at p_H 5 to 7. A fluoride ion specific electrode is used with an expanded-scale p_H meter to monitor the emf.

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Zusammenfassung Eine Mikrobestimmung von Fluorid in Gegenwart von Phosphat wurde beschrieben. Phosphat stört bis zu einer zehnfachen Phosphormenge nicht. Es wird an Zinkoxid adsorbiert, das man im Überschuß zusetzt und das vor der Fluoridtitration nicht entfernt werden muß. Fluorid wird potentiometrisch mit 0,02-m Lanthan(III) bei p_H 5 bis 7 bestimmt. Eine für Fluorid spezifische Elektrode mit einem p_H-Meter mit gedehnter Skala wird zur Messung verwendet.

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Work performed under the auspices of the U. S. Atomic Energy Commission.     

The determination of fluoride by titration with calcium chloride

A new method for the determination of fluoride ions is described. Precipitation is effected with an excess of standard calcium chloride and, after standing overnight, the unconsumed calcium ions are back-titrated with ethylenediamine tetra-acetic acid (EDTA) using Eriochrome Black T as indicator. Halides, sulphate, phosphate and arsenate do not interfere under the recommended conditions. The method is applicable over the range 5-65 mg of fluoride ion.     

High-precision determination of calcium in the presence of higher concentrations of magnesium by means of a computerized photometric titration : Application to sea water

A computerized photometric titration procedure for the determination of calcium in the presence of magnesium with zinc-zincon as indicator is described. The evaluation method is based on straight-line regression, the method yielding a relative precision of 0.00028 when applied to sea water samples in the salinity range 5–35?     

Successive chelatometric titration of calcium and magnesium

A simple procedure for the successive chelatometric titration of calcium and magnesium in natural waters, with 3',3'-bis(2-hydroxy-3-carboxy-naphthaleneazo)phenolphthalein as indicator, is described.     

EDTA titration of calcium and magnesium with a calcium-selective electrode

Direct semi-automatic and automatic derivative potentiometric EDTA procedures for the determination of calcium and/or magnesium with a calcium-selective electrode are described. Calcium is titrated in the presence of magnesium at pH 12.0 and the total calcium and magnesium is determined at pH 9.7. Calcium in the range 1-8 mg and magnesium in the range 0.7-5 mg are determined semi-automatically with average errors of about 0.2 and 0.3% respectively and automatically with average errors of 0.4 and 0.7%. Titration times vary from a few seconds to a few minutes.     

Data on the determination of calcium and phosphate in the presence of citric acid

The determination of calcium and phosphate is possible in the citrate extracts of the natural raw phosphates with complexometric-precipitate titration as usual, after oxidation of citric acid with sodium hypochlorite.The excess of sodium hypochlorite can be reduced by ammonia.     

Titrimetric determination of aluminium with ethylenediaminetetra-acetic acid in the presence of iron, copper, titanium, manganese, calcium, magnesium and phosphate

The authors have developed a rapid and accurate titrimetric method for the determination of 5–15 mg of aluminium with Complexone-III in the presence of iron, copper, titanium, manganese, calcium, magnesium and phosphate.     

Determination of calcium,magnesium, and phosphate in the presence of iron and each other

Excess EDTA and MgSO₄ solution is added to a mildly acidic solution of the sample containing calcium, magnesium, iron, and phosphate ions. Addition of NH₄OH to this solution results in the precipitation of MgNH₄PO₄·6H₂O and various iron compounds. Calcium ions and a portion of the magnesium ions stay in the solution as the respective EDTA chelates. The mixture is adjusted to a known volume and filtered. The EDTA content of the filtrate with the exception of the EDTA tied up as calcium-EDTA chelate, is titrated with standard CaCl₂ solution at pH 12.5–13.0 in the presence of hydroxy naphthol blue indicator. The calcium content of the sample can be calculated from the result of this titration.     

自动电位滴定法快速测定钾盐中的钾含量

钾含量的测量常用火焰光度法和四苯硼钾重量法。火焰光度法适用于微量分析 ,对较高含量钾的测定误差较大 ,四苯硼钾重量法的测定准确度高 ,但操作繁琐 ,测定周期长 ,易出错。本文采用四苯硼钠溶液电位滴定法 ,测定高、中含量组分钾 ,测定周期短 ,所用试剂少 ,且不受样品中水不溶物的干扰 ,选择性好 ,测定的准确度和精密度均在 0 .2 %以下 ,适用于钾盐、卤水、复合肥和钾肥中钾的测定。1　实验部分1 .1　仪器和药品ZD 2型自动电位滴定仪 (上海雷磁仪器厂 ) ,PK 1型钾离子选择电极 ,2 1 7型饱和甘汞电极 (双盐桥 )。四苯硼钠标准液 :0 .1mol…     

Spectrophotometric titration of calcium and magnesium with complexon-III and metal-specific indicators

The equivalence points of the Ca and Mg titrations with complexon-III, using metal-specific indicators, can be determined more accurately by the spectrophotometric than by the visual method. In comparison with the spectrophotometric method in the ultraviolet⁷, where no indicator is required, the end point can be determined more sharply from our titration curve.The accuracy is of the order of 0.5% ; the repeatibility is even more favourable.     

Determination of iron in the presence of large amounts of phosphate by titration with disodium dihydrogen ethylenediaminetetraacetate

Ferric iron, even in the presence of comparatively large amounts of phosphate, can be determined by titrating with the disodium salt of ethylenediaminetetraacetic acid (Versenate, Complexone III), using ammonium thiocyanate as indicator and extracting the red ferric thiocyanate into amyl alcohol, provided the pH is controlled at 2.0—2.4 at the end-point. The method has been successfully used for the determination of iron in phosphate-containing deposits from steam boilers.     

Elimination of anionic interference in flame photometric determination of calcium in the presence of phosphate and sulphate

Studies on the interference of phosphate and sulphate in the flame emission of calcium as calcium chloride have shown that there is a fall of intensity corresponding initially to the quantity of the interfering anion, the emission intensity reaching a constant value at a certain ratio of PO₄^-3 or SO₄^-2 to Ca⁺².On addition of appropriate quantities of lanthanum (or iron) to the sample, the intensity of the calcium emission lines is restored to the value it had when the interfering anions were absent.It is postulated that lanthanum replaces calcium in a phosphate- or sulphate-containing compound, that without lanthanum does not form calcium ions even at high temperature.     

Micropprocessor-controlled determination of fluoride in the presence of magnesium and calcium in sea water and blood plasma by a fluoride-selective electrode with standard additions

An automated standard additions method with an ion-selective electrode is used to determine free fluoride in plasma, urine and sea water; the amounts of pH buffer and sequestering agent are minimal. The presence of uncomplexed metal ions was allowed for in the data treatment using modified Nernst and Gran functions. After fusion with sodium hydroxide, non-volatile fluoride was determined in the plasma and urine of pediatric patients who had undergone methoxyflurane anaesthesia. Fluoride concentrations of 0.002–210 mg l^?1 were measured, generally to a precision of ±5%. The procedures reported are unusual in that complexing metal ions in the samples were not completely removed by sequestration, and that there are relatively large volume changes during the analyses of small samples. The calculation method described allows for both these features.     

Rapid visual compleximetric titration of calcium in natural waters

Visual compleximetric methods for the titration of calcium in the presence of magnesium have been based either on masking the magnesium or using an indirect indicator procedure, e.g., the system Zn-EGTA-Zincon. In the proposed method these two approaches are combined. Zn-EGTA complex is added to the mixture and the zinc liberated in the calcium replacement reaction is titrated with EGTA after the magnesium has been masked with fluoride ion.