Quantitative Determination of Sodium Metatungstate Speciation by 183W N.M.R. Spectroscopy

2000 ◽  
Vol 53 (12) ◽  
pp. 965 ◽  
Author(s):  
Bradley J. Smith ◽  
Vincent A. Patrick
Keyword(s):  
Aqueous Solution ◽  
Quantitative Determination ◽  
Direct Observation ◽  
Solubility Product ◽  
High Concentration ◽  
Kinetics Of ◽  
Paratungstate B

The speciation and equilibria of sodium metatungstate, Na6[H2W12O40], has been determined by a combination of 183W n.m.r. spectroscopy and gravimetry over the p[H] range 4.5–10.0. The use of n.m.r. spectroscopy allowed the direct observation of polytungstate anions in aqueous solution and high concentration (0.25 mol l–1). Sodium metatungstate, with the progressive addition of base, was found to decompose to paratungstate A, [W7O24]6–. Paratungstate A then slowly converted to paratungstate B, [H2W12O42]10–. The kinetics of equilibrium was found to be slow, requiring up to 8 months to stabilize. With the addition of further base paratungstate B decomposed to orthotungstate, WO42–. Logarithmic constants (logK) for these transformations were determined as 195, 20 and 118, respectively. The solubility product for sodium paratungstate B was determined to be 6.89 ( 0.80) 10–6.

Quantitative Determination of Aqueous Dodecatungstophosphoric Acid Speciation by NMR Spectroscopy

2004 ◽  
Vol 57 (3) ◽  
pp. 261 ◽  
Author(s):  
Bradley J. Smith ◽  
Vincent A. Patrick
Keyword(s):  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Quantitative Determination ◽  
Intermediate Species ◽  
High Concentration ◽  
Stable Intermediate ◽  
Ph Range

The speciation and equilibria during base decomposition of α-[PW12O40]3– have been determined using 31P and 183W NMR spectroscopy over the pH range 0.7–13.5. NMR spectroscopy was used to directly observe the polytungstate species in aqueous solution at high concentration (0.25 mol L–1) and follows the progressive decomposition of [PW12O40]3– to WO42– and PO43–. It was found unexpectedly in the pH range 1.2–2.3 that [PW12O40]3– did not decompose directly to [PW11O39]7– but first formed an equilibrium with [P2W18O62]6–, [P2W21O71]6–, and some new, stable, intermediate species before converting into α-[PW11O39]7–.

scholarly journals Leaching Titaniferous Magnetite Concentrate by Alkaline Aqueous Solution

2021 ◽  
Author(s):  
Ke Guo ◽  
Shaoyan Wang ◽  
Renfeng Song ◽  
Zhiqiang Zhang
Keyword(s):  
Aqueous Solution ◽  
Alkali Concentration ◽  
Water Usage ◽  
X Ray Diffraction ◽  
High Concentration ◽  
X Ray ◽  
Iron Concentrate ◽  
Titaniferous Magnetite ◽  
Magnetite Concentrate ◽  
Kinetics Of

AbstractLeaching titaniferous magnetite concentrate with alkali solution of high concentration under high temperature and high pressure was utilized to improve the grade of iron in iron concentrate and the grade of TiO2 in titanium tailings. The titaniferous magnetite concentrate in use contained 12.67% TiO2 and 54.01% Fe. The thermodynamics of the possible reactions and the kinetics of leaching process were analyzed. It was found that decomposing FeTiO3 with NaOH aqueous solution could be carried out spontaneously and the reaction rate was mainly controlled by internal diffusion. The effects of water usage, alkali concentration, reaction time, and temperature on the leaching procedure were inspected, and the products were characterized by X-ray diffraction, scanning electron microscope, and energy dispersive spectroscopy, respectively. After NaOH leaching and magnetic separation, the concentrate, with Fe purity of 65.98% and Fe recovery of 82.46%, and the tailings, with TiO2 purity of 32.09% and TiO2 recovery of 80.79%, were obtained, respectively.

Determination of Carbaryl Residues in Honey Bees

1965 ◽  
Vol 48 (4) ◽  
pp. 771-774
Author(s):  
D P Johnson ◽  
H A Stansbury
Keyword(s):  
Aqueous Solution ◽  
Acetic Acid ◽  
Quantitative Determination ◽  
Honey Bees ◽  
Methylene Chloride ◽  
Hydrolysis Product ◽  
Separate Analysis ◽  
Yellow Substance ◽  
Hydrolysis Of

Abstract A method has been developed for detecting residues of carbaryl (1-naphthyl methylcarbamate) as well as its hydrolysis product, 1-naphthol, in dead bees. The method is based on extraction of the bees with benzene, followed by a cleanup involving liquid partitioning and chromatography on Florisil. The quantitative determination involves hydrolysis of carbaryl to 1-naphthol and coupling of the latter with p-nitrobenzenediazonium fluoborate in acetic acid to form a yellow substance. For separate analysis, free 1-naphthol is separated from methylene chloride into a basic aqueous solution. The sensitivity of the method is about 0.1 ppm; recoveries averaged 85.6 ± 6.6% for 1- naphthol and 83.8 ± 2.7% for carbaryl.

Ultraviolet Spectroscopic Determination of Five Lanthanide Elements without Prior Separation

1993 ◽  
Vol 47 (6) ◽  
pp. 764-772 ◽  
Author(s):  
Irvin M. Citron ◽  
Patrick M. Hanlon ◽  
Stephen Arthur
Keyword(s):  
Aqueous Solution ◽  
Quantitative Determination ◽  
Heavy Metal Ions ◽  
Lanthanide Ions ◽  
Ion Concentrations ◽  
Statistical Reliability ◽  
Modified Method ◽  
Lanthanide Elements ◽  
The Individual

This investigation has resulted in an analytical method for the quantitative determination of total lanthanide concentration in aqueous solution by absorbance at 240 nm in the ultraviolet followed by quantitative determination of individual lanthanide ion concentrations by the use of concentration-responsive absorption peaks in the 190–235 nm region. The 240-nm peak is present and is proportional to concentration regardless of the ligand employed to complex the lanthanides (including H2O). The individual lanthanide/ligand peaks in the 190–235 nm region were selected on the basis of their separation from one another, their linearity of absorbance vs. concentration, and their statistical reliability based on replicate sample analyses. Lanthanides involved in this investigation were La+3, Nd+3, Eu+3, Ho+3, and Yb+3. Ligands ultimately selected for complexation were citrate for La+3, Nd+3, and Ho+3, and DTPA for Eu+3, Ho+3, and Yb+3. When large amounts of heavy metal ions were present, a modified method was developed with citrate as the only complexing ligand for all five lanthanides. The method here developed permits the analyses of lanthanide ions in aqueous solution without prior separation and involves the use of comparatively inexpensive instrumentation (UV absorption spectrophotometer).

Enhancement of carboxylic acid degradation with sulfate radical generated by persulfate activation

2010 ◽  
Vol 61 (5) ◽  
pp. 1221-1226 ◽  
Author(s):  
J. Criquet ◽  
P. Nebout ◽  
N. Karpel Vel Leitner
Keyword(s):  
Aqueous Solution ◽  
Citric Acid ◽  
Carboxylic Acids ◽  
Sulfate Radical ◽  
Acid Degradation ◽  
Competitive Reactions ◽  
Radical Production ◽  
Persulfate Activation ◽  
Kinetics Of

The aim of this work was to investigate the generation of sulfate radical for the removal of two carboxylic acids in aqueous solution: acetic and citric acids. From photochemical and radiolytic processes, kinetics of the degradation of these two carboxylic acids was studied as a function of the pH of the solution. It was shown that the maximum of acetic acid degradation occurred at pH 5. Above this pH, competitive reactions with the carbon mineralized inhibit the reaction of with the solute. In the case of citric acid, pH has only a little effect on the kinetic of citric acid degradation. The determination of mineralization yields shows several differences depending on carboxylic acids and pH. The degradation of both carboxylic acids was also studied in the radiolysis process whether with or without persulfate addition. A comparison of the processes of sulfate radical production is presented.

Quantitative determination of thiourea in aqueous solution in the presence of sulphur dioxide by Raman spectroscopy

The Analyst ◽  
1986 ◽  
Vol 111 (5) ◽  
pp. 539 ◽  
Author(s):  
Heather J. Bowley ◽  
Elizabeth A. Crathorne ◽  
Donald L. Gerrard
Keyword(s):  
Aqueous Solution ◽  
Raman Spectroscopy ◽  
Quantitative Determination ◽  
Sulphur Dioxide

Perchlorate in Sea Water

1961 ◽  
Vol 41 (1) ◽  
pp. 175-186 ◽  
Author(s):  
R. Greenhalgh ◽  
J. P. Riley
Keyword(s):  
Aqueous Solution ◽  
Quantitative Determination ◽  
Water Sample ◽  
Coefficient Of Variation ◽  
Sea Water ◽  
Absorption Spectrophotometry ◽  
Infra Red ◽  
Tetraphenylarsonium Chloride

The use of tetraphenylarsonium chloride for the detection and determination of perchlorate in sea water has been investigated. An aqueous solution of this reagent gives a visible precipitate of tetraphenylarsonium perchlorate with sea water containing 5 μg ClO4-/ml. within 10 min. For the quantitative determination of traces of perchlorate, potassium perrhenate is added to the water sample, and the tetraphenylarsonium perrhenate, which is precipitated by addition of the reagent, co-precipitates tetraphenylarsonium perchlorate. Perchlorate is determined in the mixed precipitate by infra-red absorption spectrophotometry. Using 100 ml. of sea water, a sensitivity of 0·03 μg ClO4-/ml. can be attained, with a coefficient of variation of ca. 10%. No interference is caused by the ions normally present in sea water.

Gravimetric Determination of Ethoxylated Mono- and Diglycerides in Bread

1981 ◽  
Vol 64 (6) ◽  
pp. 1462-1464
Author(s):  
James F Lawrence ◽  
Jagannath R Iyengar ◽  
Harry B S Conacher
Keyword(s):  
Aqueous Solution ◽  
Fatty Acids ◽  
Quantitative Determination ◽  
Petroleum Ether ◽  
Gravimetric Method ◽  
Phosphomolybdic Acid ◽  
Barium Ions ◽  
Gravimetric Determination ◽  
Ether Extraction

Abstract A gravimetric method is described for the quantitative determination of ethoxylated mono- and diglycerides (EMGs) in bread at levels as low 0.42% (dry sample). The air-dried pulverized samples are Soxhlet-extracted 22 h with an azeotropic mixture of n-propanol-water. The contents are evaporated to dryness, and then treated with 5% HCl in methanol to trans-esterify the fatty acids present which are then removed by petroleum ether extraction. The EMGs are subsequently precipitated from aqueous solution with phosphomolybdic acid in the presence of barium ions. The precipitate is weighed and compared with known amounts of standard carried through the same procedure.

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