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].     

Semiautomatic indirect titration of alkaline-earth ions with catalytic endpoint indication

A semiautomatic spectrophotometric method of endpoint indication for indirect catalytic titrations of microamounts of alkaline-earth ions is described. The manganese(II)-catalyzed autoxidation of 1,4-dihydroxyphthalimide dithiosemicarbazone is used as indicator reaction. Calcium and magnesium (10–150 μg), strontium (20–250 μg), and barium (20–450 μg) can be determined by adding a known excess of EDTA to the sample solution and back-titrating the unconsumed inhibitor agent with standard manganese(II) solution. This catalytic method was applied to determine the total concentration in calcium and magnesium (total hardness) in natural waters and milk. The method is fast, accurate (1–3%), precise (0.2–0.8%, relative standard deviation), and specially useful for the determination of microamounts where metallochromic indicator are ineffective (for concentrations ranges below 10^?4M).     

Fast method for the determination of radiostrontium and plutonium isotopes in food samples

Rapid radioanalytical methods are important in the case of a radiological emergency and for the defence against nuclear hazards, especially for pure alpha and beta emitters like ^239/240Pu and ⁸⁹Sr/⁹⁰Sr. A new fast method was developed with an overall analysis time altogether around 11 h, for only strontium isotopes about 7 h. The method combines two extraction chromatography resins, DGA- and Sr-resin, to separate mainly strontium and plutonium. A broad variety of food samples with different fat, carbohydrate and protein contents were tested and successfully analysed. The yields obtained were typically around 95% and 70% for ⁹⁰Sr and ²⁴²Pu.

     

Radiochemical analysis of90Sr in milk,soil and plants by solvent extraction

A universal and fast method of⁹⁰Sr determination in environmental matrices (raw and dried milk, plants, soils) has been elaborated. Solvent extraction method of daughter⁹⁰Y by tributyl phosphate was used. The method of strontium determination is compatible with determination of other transuranic elements (americium, plutonium) and there is no need to check the chemical yield of strontium.     

Natural radioactivity in building materials utilized in the State of Kuwait

A simple radiochemical procedure is described for the determination of⁹⁰Sr in brines, which are very highly concentrated in sodium, calcium, potassium, magnesium, chloride and sulfate ions. The method is based on the different solubility of yttrium as compared to that of strontium, calcium and magnesium in ammonium chloride solutions, and utilizes Eichroms resin TRU·Spec for the purification of the yttrium fraction. The overall time required for the⁹⁰Sr analysis (excluding the counting time) is less than one day. Because the procedure involves only rather simple steps, it is well suited for routine analyses of large sample numbers.     

Estimation of 90Sr in reprocessed uranium oxide samples

Summary A method has been developed for the estimation of ⁹⁰Sr in reprocessed uranium oxide samples obtained from the Purex processing of natural uranium spent fuel discharged from the research reactor. The method employs a combination of precipitation and solvent extraction procedure to eliminate other beta-impurities prior to resorting to the estimation of ⁹⁰Sr by beta-counting. ¹⁰⁶Ru was eliminated by volatalizing with perchloric acid, uranium was removed by carrier precipitation with strontium as sulphate. The sulphate precipitate was converted to carbonate and dissolved in nitric acid. ²³⁴Th and ²³⁴Pa were eliminated by synergistic solvent extraction using tri-n-butyl phosphate and thenoyl trifluoroacetone extractant mixture in xylene. An iron scavenging step was included to remove any residual impurities. Finally, strontium is precipitated as SrC₂O₄^. H₂O. The separated ⁹⁰Sr activity was followed to check the equilibrium growth of ⁹⁰Y.     

A miniaturised isotachophoresis method for magnesium determination

The use of malonic acid as a complexing agent has enabled a new method to be devised to allow the determination of magnesium to be made using miniaturised isotachophoresis. Using a leading electrolyte of 10 mmol L⁻¹ caesium hydroxide and 2 mmol L⁻¹ malonic acid at pH 5.1 gave the method a high specificity towards magnesium. Investigations using a poly(methyl methacrylate) chip device with an integrated conductivity detector showed that no interference from calcium, strontium, barium and sodium should occur. The method was found to be linear over the range of magnesium concentrations from 0.625 to 75 mg L⁻¹ and the limit of detection was calculated to be 0.45 mg L⁻¹. Separations were demonstrated with water samples but the procedure should also be applicable to more complex sample matrices such as inorganic explosive residues, blood or urine.     

Structural Variances in the Homologous Series of Alkaline Earth Metallated Octamethylcyclotetrasilazandiides

The magnesium, calcium, and strontium metal derivatives of 2, 2, 4, 4, 6, 6, 8, 8‐octamethylcyclotetrasilazane (OMCTS) have been synthesized and structurally characterized by X‐ray diffraction studies. These are the first complexes of the homologous series of alkaline earth metalated OMCTS. Similar to the homologous series of the corresponding alkali metal complexes, the structural properties show remarkable tendencies in the series from magnesium to strontium. The magnesium dication causes the most pronounced deformation along the transannular N^‐···N^‐ vector of the [(c‐N‐SiMe₂‐NH‐SiMe₂‐)₂]^2‐ dianionic ring. The lengths of the Si‐N bonds are correlated to the bond types, so that shorter distances result when the bonds become more ionic. The difference between the long Si‐N(H) bonds and the short Si‐N^‐ bonds decreases gradually with the increasing mass of the alkaline earth metal dication.     

Reactor production of 32P for medical applications: an assessment of 32S(n,p)32P and 31P(n,γ)32P methods

The article describes a comparative study carried out on the reactor production of ³²P by two different processes, namely, ³²S(n,p)³²P and ³¹P(n,γ)³²P with a view to determine the merits and bottlenecks of each method and assess the usefulness of ³²P obtained from each of the processes. In a typical batch, 250 g of elemental sulfur when irradiated at a fast neutron flux of ~8 × 10¹¹ n cm^?2 s^?1 for 60 days, after chemical processing provided about 150 GBq(4.05Ci) of ³²P having specific activity of 200TBq(5500Ci)/mmole. On the other hand, irradiation of 0.35 g of red phosphorus at a fast neutron flux of ~7.5 × 10¹³ n cm^?2 s^?1 for a period of 60 days gave 75 GBq(2.02Ci) of ³²P of specific activity 7 GBq(190mCi)/mol^-1. While the specific activity of ³²P obtained from ³²S(n,p)³²P is superior to that obtained from the ^3lP(n,γ)³²P process, the requirement of elaborate target processing steps involving distillation and purification emerged as a deterrent that limits its widespread adaptability. Both the production routes offer ³²P of acceptable quality amenable for medical applications although their specific activity differs.     

Response of poly(vinyl chloride) electrodes based on the neutral carrier 1,4,7,10-tetraoxacyclododecane

Ion-selective electrodes based on the neutral carrier, 12-crown-4, in a poly(vinyl chloride) matrix were found to respond ideally, or almost ideally, to potassium, sodium, barium, strontium, magnesium, cobalt(II), nickel(II) and aluminum ions. The electrode showed good selectivity for Al³⁺ over Co²⁺ and Mg²⁺, and for Co²⁺ over Mg²⁺. Little selectivity was found for the other ions tested.     

Sorption of Strontium Ions on Potassium-Titanate Nanoparticles of Various Morphology Obtained under Hydrothermal Conditions

The results of the study of the interaction of an aqueous solution of strontium nitrate with potas-sium-titanate nanoparticles of different morphology obtained by the hydrothermal method are reported. Comparative analysis showed the advantage of nanotubes as sorbents over nanolayers and nanowires. As can be seen from the experiment conducted with nanotubes containing aluminum, an amount of strontium sorbed from the solution rises with increasing temperature: at 50°C the absorption by the tubular matrix was ≈ 0.76 × 10^?3 mol g^?1, and at 80°C that was ≈ 2.02 × 10^?3 mol g^?1. Nanotube samples doped with magnesium had the best sorption characteristics: After 5 h of keeping in a solution at 80°С, the content of strontium in them was ≈3.65 × 10^?3 mol g^?1. The results show the promise of using potassium titanate nanoparticles to extract strontium from aqueous solutions.

     

Estimation of sulfur in coal by fast neutron activation

A simple method is described for estimation of sulfur in coal using fast neutron activation of sulfur, i.e.³²S(n,p)³²P and subsequent measurement of³²P -activity (1.72 MeV) by a Geiger-Müller counter. Since the sulfur content of Indian coal ranges from 0.25 to 3%, simulated samples of coal containing sulfur in the range from 0.25 to 3% and common impurities like oxides of aluminium, calcium, iron and silicon have been used to establish the method.     

Rapid method for the determination of radiostrontium in milk

A radiochemical procedure comprising ion chromatography for preconcentration, oxalate precipitation for alkali/alkaline earth separation, strontium specific extraction chromatography with a crown ether for calcium/strontium separation, carbonate precipitation for counting on a low background proportional counter, provides a simple, rapid (48 h) and effective method for radiostrontium determination in emergency situation in milk. The separation scheme gives a strontium recovery rate of 62% and an empiric relative standard deviation of 11%. The detection limit for 500 ml milk and 3600-second counting time is 0.090 Bq^.l^-1.     

Complexometric estimation of ferric iron

Summary Ferric iron has been determined alone or in presence of barium chloride, calcium chloride, magnesium sulphate, mercuric chloride, manganese sulphate, strontium nitrate, chromic sulphate or zinc sulphate by titrating it with EDTA, using potassium thiocyanate-p-anisidine indicator. In these complexometric titrations, the quantitative results obtained by using potassium thiocyanate-p-anisidinie indicator are comparable with those obtained with Bindschedler's green indicator; and the metallic salts mentioned above do not interfere in the estimation of ferric iron by this method.     

Research on a pellet co-precipitation micro-filtration process for the treatment of liquid waste containing strontium

The chemical precipitation method for radioactive wastewater treatment has the advantages of being simple and cost-effective. However, difficulties with the solid–liquid separation and sludge concentration restrict the application of this method. In this paper, a pellet co-precipitation micro-filtration (PCM) process was studied for treating strontium-containing wastewater on a laboratory scale. The seed was prepared by CaCO₃ powders. Sr²⁺ and CO₃ ^2? were constantly crystallised on the seed surface, with Na₂CO₃ as the precipitating agent in the pellet reactor. The following membrane separator with the addition of FeCl₃ enhanced the treatment effect. The average strontium concentrations in the raw water and in the effluent were 12.0 and 0.0220 mg/L, respectively. The strontium decontamination factor (DF) increased with the operation time, with an average value of 577. The precipitate particles formed gradually grew larger, with good sedimentation properties. When the experiment was complete, the formed precipitate was separated easily from the liquid phase and directly discharged. The concentration factor (CF) was 1,958. In the PCM process, crystallisation was the main mechanism for strontium removal, with the influent strontium level playing an important role. Membrane pore blockage and cake layer formation could help to further intercept the strontium crystallites. Furthermore, ferric chloride coagulation in the membrane separator also contributed to strontium removal. The PCM process has potential for wider application in the removal of strontium from wastewater.     

Development of a method based on inductively coupled plasma-dynamic reaction cell-mass spectrometry for the simultaneous determination of phosphorus,calcium and strontium in bone and dental tissue

A method, based on the use of a quadrupole-based inductively coupled plasma-mass spectrometry instrument equipped with a quadrupole-based collision/reaction cell (dynamic reaction cell, DRC), was developed for the simultaneous determination of phosphorus, calcium and strontium in bone and dental (enamel and dentine) tissue. The use of NH₃, introduced at a gas flow rate of 0.8 mL min^− 1 in the dynamic reaction cell, combined with a rejection parameter q (RPq) setting of 0.65, allows interference-free determination of calcium via its low-abundant isotopes ⁴²Ca, ⁴³Ca and ⁴⁴Ca, and of strontium via its isotopes ⁸⁶Sr and ⁸⁸Sr that are freed from overlap due to the occurrence of ArCa⁺ and/or Ca₂⁺ ions. Also the determination of phosphorus (³¹P, mono-isotopic) was shown to be achievable using the same dynamic reaction cell operating conditions. The bone certified reference materials NIST SRM 1400 Bone Ash and NIST SRM 1486 Bone Meal were used for validation of the measurement protocol that was shown capable of providing accurate and reproducible results. Detection limits of P, Ca and Sr in dental tissue digests were established as 3 µg L^− 1 for P, 2 µg L^− 1 for Ca and 0.2 µg L^− 1 for Sr. This method can be used to simultaneously (i) evaluate the impact of diagenesis on the elemental and isotopic composition of buried skeletal tissue via its Ca/P ratio and (ii) determine its Sr concentration. The measurement protocol was demonstrated as fit-for-purpose by the analysis of a set of teeth of archaeological interest for their Ca/P ratio and Sr concentration.     

An ion-exchange scheme for the determination of the major cations in sea water

A cation-exchange scheme is described for the determination of the principal cations in sea water. The cations are adsorbed onto a column of Amberlite CG 120. Sodium and potassium are eluted together using 0.15 M ammonium chloride and determined gravimetrically as sulphates; potassium is then determined gravimetrically as potassium tetraphenylboron and sodium is determined by difference. Magnesium and calcium are eluted by means of 0.35 M ammonium chloride and 1 M ammonium acetylacetonate (pH 9.6) respectively, and titrated with EDTA. Finally, strontium is eluted with 2 M nitric acid and determined by flame photometry. Tests made using an artificial sea water showed that the method had coefficients of variation of 0.02, o.22, 0.04, 0.08 and 0.8% for sodium, potassium, magnesium, calcium and strontium respectively.     

Microdetermination of calcium and magnesium in a mixture

Summary A procedure is presented for the chemical separation and determination of mg quantities of calcium and magnesium, which is based on the selective carrying of calcium by ignited strontium sulphate leaving magnesium in the solution phase; the carried calcium is recovered by leaching with alcoholic sulphuric acid solution. Calcium and magnesium in the separated fractions are determined complexometrically using Eriochrome Black T as the indicator.

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Zusammenfassung Ein Verfahren zur chemischen Trennung und Bestimmung von mg-Mengen Calcium und Magnesium wird vorgeschlagen, wobei Ca selektiv mit geglühtem Strontiumsulfat abgetrennt wird, während Mg in Lösung bleibt. Ca wird mit alkoholischer Schwefelsäure eluiert. Beide Metalle werden getrennt gegen Eriochromschwarz T komplexometrisch titriert.

     

Ion activities and copper electrode reactions in magnesium sulphate solutions

Thermodynamic and kinetic studies have revealed conventional mean-ion and convenient single-ion activity coefficients for copper(II), magnesium and sulphate ions and standard exchange rates for either step of the liquid Cu(Hg)/Cu(II) electrode and of the solid Cu/Cu(II) electrode, all in 0.005 mol kg^?1 CuSO₄+0.005 mol kg^?1 H₂SO₄+(x?0.01) mol kg^?1MgSO₄ (for x=0.2 to 3) at 25°C. With increasing x, the sulphate activity coefficient steadily falls, the copper(II) and magnesium activity coefficients go through a minimum near x=1, and the standard rates fall. The kinetic changes with x reveal some information on double-layer and ligand effects.     

A new method for the determination of the 34S/32S ratio of water-soluble sulphur in soil

A new method for the determination of the ³⁴S/³²S ratio of water-extractable sulphate in soil is described. Soils are extracted directly with deionized water, which is evaporated down. The remaining residue is then rehydrated and transferred to tin cups containing an adsorbent and mixed with an oxygen donor (V₂O₅). Samples are then analysed using a continuous flow isotope ratio mass spectrometer. The new method requires around 10?g soil per determination, compared to much larger amounts (up to kilograms) of soil required for the previous methods. Sample preparation and subsequent analysis is quick and efficient. The method is demonstrated using a number of soils collected from around the world to provide a range of determined δ³⁴S values. The δ³⁴S values of water-extractable sulphur were broadly similar to those of the soil total sulphur.