Direct complexometric determination of magnesium in the presence of uranium, iron and aluminium

Conditions for the direct complexometric determination of magnesium in the presence of uranium, iron and aluminium are described. The method is based on the masking of uranium by hydroxylamine, and of iron and aluminium by triethanolamine. Methylthymol Blue is used as indicator for the EDTA titration of magnesium at pH 10.     

Preparation of iron,aluminium, calcium,magnesium, and zinc humates for environmental applications

A few non-conventional humate sorbents, i.e. iron humate (FeH), aluminium humate (AlH), calcium humate (CaH), magnesium humate (MgH), and zinc humate (ZnH), were prepared from a commercial product Fortehum L/K (Humatex, Bílina, Czech Republic). The metal content in humates was determined by X-ray fluorescence analysis, the organic elements (C, H, N, and S) were analysed by an Elementar Vario III and the functional groups were determined by classical methods using KBr pellets and diffuse reflection infrared spectroscopy (DRIFTS). FeH, AlH, and ZnH were tested as sorbents for the removal of inorganic or organic pollutants (metals, inorganic ions, dyes, and chlorophenols) from waste water. Sorption properties decreased in order: ZnH, AlH, FeH. CaH and MgH are partly soluble and therefore they are not usable as sorbents. However, their ion-exchange abilities for heavy metals are excellent which makes them usable for phytoremediation and bioremediation.     

Chelatometric determination of calcium and magnesium in iron ores, slags, anorthosite, limestone, copper-nickel-lead-zinc ores and divers materials

Chelatometric methods for the determination of calcium and magnesium in iron ores, slags, anorthosite, copper-nickel-lead-zinc ores and various other materials are described. Potential interfering elements are masked with triethanolamine and potassium cyanide. In one aliquot calcium is titrated at pH > 12, with calcein and thymolphthalein mixed indicator and in another aliquot calcium and magnesium are titrated in ammonia buffer, with o-cresolphthalein complexone screened with Naphthol Green B as indicator. The results compare favourably with certified values for reference materials of diverse nature.     

An investigation of a flameless atomic-absorption method for determination of aluminium, calcium, iron and magnesium in sewage sludge

The methods currently used for the determination of aluminium, calcium, iron and magnesium in sewage sludge are time-consuming. A rapid flameless atomic-absorption procedure, utilizing homogenization of diluted samples as the only pretreatment, has been compared with wet and dry analytical methods followed by flame atomic-absorption analysis, in a statistically designed experiment. Low-sensitivity (secondary absorption) lines have been used for the flameless analysis. The flameless atomic-absorption method described is better than all the other methods tested, with the exception of the nitric-perchloric-hydrofluoric acid digestion procedure. The time saved is substantial and the method could be used advantageously for routine analysis.     

Masking of manganese in relation to stepwise complexometric determination of calcium, magnesium and manganese

A critical study has been made of the masking of manganese with potassium cyanide in alkaline medium for complexometric titration of calcium and magnesium. It has been found that there is incomplete oxidation to manganese(III) unless the solution is aged for a sufficient period or air is bubbled through the solution at 35 ± 5° for 10 min. The manganese(III) complex can be reduced with ascorbic acid for titration with EDTA. Procedures are given for stepwise titration of magnesium, manganese and calcium in silicate materials. Mixed indicators are used, to improve the end-points.     

Stepwise complexometric determination of aluminium, titanium and iron concentrations in silica sand and allied materials

Background  

This study aimed at measuring the quantities of Al, Ti and Fe in silica sand and allied materials employing a complexometric method in the same analyte and a stepwise indirect titration with EDTA. The method involves the complexation of Al, Ti and Fe with excess EDTA and the selective de-complexation of TiO-EDTA and Al-EDTA complexes with tartaric acid and NaF respectively. In addition to its simplicity, rapidity and accuracy, the proposed method does not require the use of a separation technique or any sophisticated instrumentation.     

Quantitative separation of beryllium from magnesium,calcium, aluminium,iron and other elements by cation-exchange chromatography in nitric acid-methanol

Beryllium is separated from Mg, Ca, Mn(II), Fe(III), Al, Co(II). Zn. U(VI), La and Gd by elution with 2.0 M nitric acid in 70 % methanol from a column of AG50W-X8 sulphonated polystyrene cation exchanger, while the other elements are retained quantitatively. Sr, Ba, Sc, Y, the other lanthanides, Zr, Hf, Th, Ga, In, Cd and Ni(II) should also be separated according to their distribution coefficients or elution behaviour. Separations are sharp and recoveries quantitative from millimolar amounts down to 10 μg of beryllium. The separation of Ti(IV) and Cu(II) from beryllium is not satisfactory and requires rather large columns. Bi(III), Pb(II), Hg(II) and the alkali metals are eluted together with beryllium, but can be separated by other methods. Typical elution curves and results for the quantitative separation of binary synthetic mixtures are presented.     

Determination of calcium and magnesium in magnesite by a complexometric method employing co-precipitation of calcium with strontium sulphate

In the classical gravimetric method calcium is precipitated as phosphate along with the magnesium and recovered by adding sulphuric acid and alcohol, then Ca²⁺ and Mg²⁺ are determined separately by the usual method [1]. In the proposed method calcium is co-precipitated with strontium sulphate and in the filtrate magnesium ions are determined by EDTA. Then calcium is calculated by difference after estimating combined Ca²⁺ and Mg²⁺ ions [2].     

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.     

A new indicator for the complexometric determination of calcium

Glyoxal bis-(2-hydroxy-anil) is proposed as a new indicator for the complexoemetric titration of calcium. The end-point is indicated by a sharp change from pink to yellow.     

Determination of traces of calcium, magnesium, iron and nickel in aluminium salts by atomic-absorption spectrophotometry with a microwave-excited source and hollow-cathode lamps

The determination of trace amounts of calcium and magnesium in solutions containing large concentrations of aluminium salts may be accomplished by co-precipitating their hydroxides on iron(III) hydroxide, dissolving the precipitate, and extracting the 8-hydroxyquinolates of calcium and magnesium into methyl isobutyl ketone at about pH 11. The extract may be sprayed into the airpropane flame of a simple unmodulated spectrophotometer and atomic-absorption measurements for calcium and magnesium made at 4227 and 2852 A respectively. The limits of determination correspond to 10 and 1 ppm of calcium and magnesium in solid alumina. Iron and nickel may be co-precipitated on hydrated manganese(IV) oxide and their 8-hydroxyquinolates extracted at pH 4.5. Measurements of atomic absorption for these elements at 2483 and 2320 A respectively yield limits of determination corresponding to 10 ppm in alumina. Hollow-cathode lamps may be used for calcium, magnesium and nickel, but a simple microwave-excited discharge tube gives much better sensitivity than a hollow-cathode lamp for iron.     

Gas-chromatographic analysis of carbides in aluminium and magnesium

Summary A quantitative gas-chromatographic method (molecular sieve column, FID) for the determination of Al₄C₃ in aluminium and magnesium has been developed. The effect of methane from external sources has been investigated and eliminated. Metallographic analysis of carbides in polished specimens were consistent with the gas-chromatographic measurements within a factor of 2. The discrepancy can be explained by the large uncertainties in light microscopy analysis of the small carbides. Analysis of commercial magnesium shows that the metal contains ca. 2–9 ppm of Al₄C₃. The concentration of carbides in aluminium from the electrolysis cell is in the range of 10–35 ppm and in the final product of ca. 2–12 ppm Al₄C₃. CaC₂ has been detected in a few magnesium and aluminium samples by means of gas-chromatography and microprobe analysis.

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Gas-chromatographische Analyse von Carbiden in Aluminium und Magnesium

Zusammenfassung Zur Bestimmung von Al₄C₃ in Aluminium und Magnesium wurde eine quantitative gas-chromatographische Methode (MolekularsiebSäule, FID) entwickelt. Der Einfluß von Methan aus äußeren Quellen, wurde untersucht und ausgeschaltet. Die metallographischen Untersuchungen von Carbiden an polierten Proben stimmten mit den Ergebnissen der gas-chromatographischen Messungen mit einem Faktor von 2 überein. Der Unterschied kann durch die großen Unsicherheiten bei der lichtmikroskopischen Analyse der kleinen Carbide erklärt werden. Die Analyse des technisch reinen Magnesiums zeigt, daß das Metall ca. 2–9 ppm Al₄C₃ enthält. Die Konzentration von Carbiden in elektrolytisch raffiniertem Aluminium liegt im Bereich 10–35 ppm und im Endprodukt bei ca. 2–12 ppm Al₄C₃. CaC₂ wurde in einigen Magnesium- und Aluminiumproben mit Hilfe von gas-chromatographischen und Mikrosondenuntersuchungen festgestellt.

     

A rapid method for the estimation of calcium and magnesium carbonates in limestones, dolomite and other calcareous materials

Summary Calcium and magnesium carbonates are determined in minerals by dissolving the sample in ammonium chloride solution and subsequent chelatometric titration. Iron and aluminium are dissolved, it any, in traces only.

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Zusammenfassung Calcium- und Magnesiumcarbonat werden in Mineralen bestimmt, indem man die Probe in Ammoniumchloridlösung auflöst und anschlie\end chelatometrisch titriert. Eisen und Aluminium werden nur in vernachlÄssigbaren Mengen gelöst.

     

Direct complexometric determination of aluminium in "alzinoy"

A simple and precise method for the complexometric determination of aluminium in "Alzinoy" (a binary alloy of aluminium and zinc) is described. After dissolution of the sample in hydrochloric acid, aluminium, zinc and any lead and iron are complexed with excess of EDTA. The excess of EDTA is titrated with lead solution, with Xylenol Orange as indicator. Ammonium fluoride is then added to decompose the Al-EDTA complex, and the EDTA liberated is titrated with lead solution. Four samples can be analysed in about 45 min.     

A comparative study of surface acidity in the amorphous, high surface area solids, aluminium fluoride, magnesium fluoride and magnesium fluoride containing iron(III) or aluminium(III) fluorides

The behaviour of the sol–gel prepared, amorphous solids, high surface area (HS) aluminium fluoride and magnesium fluoride in promoting room temperature dehydrochlorination of tert-butyl chloride (Bu^tCl), in their catalytic activity for the dismutation of chlorodifluoromethane and in the temperature programmed desorption of ammonia is similar, indicating that, unexpectedly, both solids exhibit significant surface Lewis acidity. Using a similar approach, it has been demonstrated that surface Lewis acidity in HS-MgF₂ is enhanced by the incorporation of amorphous iron(III) fluoride and probably also by amorphous aluminium(III) fluoride. A second, unexpected feature is the substantial retention of anhydrous hydrogen chloride by all the solids, which is observed by the use of chlorine-36 labelling, when they are exposed at room temperature either to Bu^tCl or to HCl directly. The detailed behaviour of H³⁶Cl towards HS-AlF₃ depends on the fluorinating agent, dichlorodifluoromethane or anhydrous hydrogen fluoride, which is used in the second stage of HS-AlF₃ synthesis. This observation and the pattern of the results obtained overall lead to the proposal that strongly adsorbed HCl behaves as an unconventional Lewis base towards these solids.     

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.     

Flow-injection analysis of silicate rocks for total iron and aluminium

A flow-injection method is described for the spectrophotometric determination of total iron and aluminium in silicate rocks. Rock samples are opened up by fusion with a mixture of lithium carbonate and boric acid, the melt is taken up in 1M hydrochloric acid and the resulting solution is used for the determination of both iron and aluminium. The flow system for the determination of iron needs no particular reagents, involving simply measurement of the absorbance of the chloro-complex of iron(III) at 335 nm. The system for aluminium consists of the reduction of iron(III) to iron(II), colour development with Xylenol Orange (XO), destruction of XO-chelates other than that of aluminium by addition of EDTA and subsequent measurement of the absorbance of the aluminium-XO complex at 506 nm. The systems permit semi-automatic, rapid analysis of silicate rocks for iron and aluminium. Results obtained for standard rocks were in good agreement with the recommended values. The precision ranged from 0.1 to 0.9% for iron and from 0.3 to 0.7% for aluminium.     

Fluorometric titration of calcium, magnesium and iron using calcein blue as indicator

Calcium, magnesium and iron can be determined by successive fluorometric titration without separation. Calcium is titrated directly with EGTA at a pH 13; magnesium is determined by a substitution reaction with copper-EDTA complex at a pH of about 11 ; and iron is titrated directly with EDTA in the presence of hydrogen peroxide at a pH of 10.5, after destroying its triethanolamine complex. Calcein Blue serves as an indicator in all of the titrations and as a fluorescent standard. The end-points are sharp and the accuracy is good for various proportions of the metal ions. The method is simple, reproducible and inexpensive. Standard solutions of ions, limestone, cement and serum samples have been analysed by the proposed method.     

Study of the protein-bound fraction of calcium,iron, magnesium and zinc in bovine milk

Two approaches were used to study the interaction of Ca, Fe, Mg and Zn with bovine milk proteins by inductively coupled plasma optical emission spectrometry (ICPOES). Selective separations in bovine milk samples were accomplished employing an acid protein precipitation using 100 g l⁻¹ trichloroacetic acid (TCA), and an enzymatic protein hydrolysis using 50 g l⁻¹ pepsin (PEP) solution, respectively. The results were compared with total mineral contents determined after microwave-assisted acid digestion. The results obtained by enzymatic and acid precipitation evidenced the different interaction forms of Ca, Fe, Mg and Zn in the system formed by milk components. Iron was not solubilized by the TCA treatment, but was recovered completely after the enzymatic treatment. Quantitative recoveries of Ca, Mg and Zn were obtained using both approaches, showing that these analytes were bound to milk compounds affected by either treatment. Calcium, Mg and Zn are mainly associated with colloidal calcium phosphate and Fe is bound to the backbone of the casein polypeptide chain, cleaved by pepsin enzyme. The proposed approaches could be used to assess the complexity of these chemical interactions.