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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A method for determining ~ 0.001% or more of tantalum in ores and mill products is described. After fusion of the sample with sodium carbonate, the cooled melt is dissolved in dilute sulphuric-hydrofluoric acid mixture and tantalum is separated from niobium and other matrix elements by methyl isobutyl ketone extraction of its fluoride from 1M hydrofluoric acid-0.5M sulphuric acid. The extract is washed with a hydrofluoric-sulphuric acid solution of the same composition to remove co-extracted niobium, and tantalum is stripped with dilute hydrogen peroxide. This solution is acidified with sulphuric and hydrofluoric acids and evaporated to dryness, and the residue is dissolved in oxalic-hydrofluoric acid solution. Tantalum is ultimately determined spectrophotometrically after extraction of the blue hexafluorotantalate-Brilliant Green ion-association complex into benzene from a 0.05M sulphuric acid-0.5M hydrofluoric acid-0.2M oxalic acid medium. The apparent molar absorptivity of the complex is 1.19 x 10(4) l.mole(-1).mm(-1) at 640 nm, the wavelength of maximum absorption. Common ions, including iron, aluminium, manganese, zirconium, titanium, molybdenum, tungsten, vanadium, tin, arsenic and antimony, do not interfere. Results obtained by this method are compared with those obtained by an X-ray fluorescence method.
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PMID:Spectrophotometric determination of tantalum in ores and mill products with brilliant green after separation by methyl isobutyl ketone extraction of tantalum fluoride. 1896 5

A highly sensitive method for the spectrophotometric determination of titanium with phenylfluorone (PF) in the presence of Triton X-305 and emulsifier OP has been developed. In acid medium (pH 1.4-2.2) Ti(IV) forms red-violet complexes with PF, Triton X-305 and OP. The complex exhibits maximum absorption at 540 nm. The molar absorptivity is 1.63 x 10(5) 1.mole(-1).cm(-1). The Ti:PF ratio in the complex is 1:2. Beer's law is obeyed in the titanium concentration range 0-0.2 microg/ml in the final solution. Fluoride and EDTA interfere. The method has been used for the rapid direct determination of microamounts of Ti(IV) in soils and cereals with satisfactory results.
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PMID:Study of the titanium-phenylfluorone complex formed in the presence of Triton X-305 and emulsifier OP. 1896 88

A very sensitive, selective and simple method for extraction and spectrophotometric determination of titanium(IV) with an alpha-hydroxy acid has been developed. p-Chloromandelic acid reacts with titanium in weakly acidic aqueous solution at room temperature to form a complex anion extractable into chlorobenzene with Malachite Green as counter-ion. Titanium is determined indirectly by measuring the absorbance of Malachite Green in the extract at 630 nm. The calibration graph is linear for titanium(IV) over the range 0.25-7.5muM (0.05-1.44 mug); the apparent molar absorptivity is 1.31 x 10(5) l.mole(-1).cm(-1). The method has been successfully applied to the determination of titanium in mild steels.
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PMID:Extraction and spectrophotometric determination of titanium(IV) with malachite green and p-chloromandelic acid, with application to mild steels. 1896 46

The synthesis, spectroscopic characteristics and analytical applications of 1,2-cyclo-hexanedione bis-benzoylhydrazone are reported. The reaction of this new compound with titanium(IV) has been studied spectrophotomelrically. An orange 1:2 metal/ligand complex (lambda(max)= 477 nm, = 1.05 x 10(4) l.mole(-1).cm(-1)) is formed at pH 1.75-3.0 in 3:2 v v ethanol-water medium. The method is simple and selective and has been satisfactorily applied to the determination of titanium in bauxite, Portland cement, amphibolites and granites.
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PMID:Synthesis and characterization of 1,2-cyclohexanedione bis-benzoyl-hydrazone and its application to the determination of ti in minerals and rocks. 1896 68

The characteristics of the mixed-ligand titanium(IV)-fluoride-alizarin complex, including the optimum conditions of formation and extraction into methyl isobutyl ketone, are described. A simple and sensitive procedure for spectrophotometric determination of titanium has been developed. At pH 9.5-10.3 titanium reacts with alizarin in the presence of fluoride to form a red-violet complex that is completely extractable into methyl isobutyl ketone, and has its absorption maximum at 513 nm. The molar absorptivity at 513 nm is 7.0 x 10(4)l.mole(-1).cm(-1). Beer's law is obeyed up to 22 mug of titanium in 30 ml of solution. The method has been used for the determination of titanium in an oxide mixture and aluminium alloy samples.
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PMID:Extraction and spectrophotometric determination of titanium(IV) with alizarin and fluoride. 1896 46

A rapid spectrophotometric method for the determination of Pd in titanium alloys is proposed. It is based on the reaction of 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol with Pd(II) in a sulphuric acid medium in the presence of ethanol. Beer's law is obeyed up to 40 mug of Pd. The molar absorptivity is 4.5 x 10(4) 1.mole(-1).cm(-1). The standard deviation is 0.3 mug of Pd and the coefficient of variation varies from 0.8 to 3.3%. The elements ordinarily present in such alloys do not interfere. High selectivity is achieved by using fluoroboric acid as masking agent. Improvements in the method of sample decomposition also contribute to the rapidity of the method.
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PMID:Rapid spectrophotometric determination of palladium in titanium alloys with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol. 1896 35

N-m-Tolyl-n-phenylhydroxylamine is proposed for the spectrophotometric determination of titanium. The reagent forms a yellow chloroform-soluble complex with titanium in media with a hydrochloric acid concentration of at least 9M. The apparent molar absorptivity at 380 nm is 7.4 x 10(3) 1.mole(-1).cm(-1). The optimum final concentration range is 0-54 mug of titanium in 10 ml of chloroform. The complex contains the metal and reagent in 1:2 ratio. The proposed method has been successfully applied to the determination of titanium in coal, coal fly-ash, pond sediment and asphalt.
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PMID:Spectrophotometric determination of titanium with N-m-Tolyl-N-phenylhydroxylamine and its application to environmental samples. 1896 26

The formation and extraction of the ion-associates of the vanadium(V)-3,5-dinitrocatechol (DNC) anionic chelate complex with various basic dyes have been studied and a new sensitive extraction-spectrophotometric method for the determination of vanadium based on the system V(V)-DNC-Brilliant Green has been developed. Beer's law is obeyed up to a vanadium concentration of 0.3 mug/ml and the molar absorptivity is 1.7 x 1O(5) l.mole(-1). cm(-1) at 630 nm. The molar ratios of the components and the form of the vanadium(V) cation in the extracted compound have been determined, and the formula [VO(OH)(DNC)(2-)(2)][BG(+)](2) is proposed. Titanium, molybdenum, tungsten, EDTA and thiocyanate interfere seriously. The method becomes specific after a preliminary separation of vanadium by its extraction as the BPHA complex from H(2)SO(4)-HF medium, and is 40 times more sensitive than the spectrophotometric BPHA method. The proposed method has been applied to determination of traces of vanadium (about 10(-5)%) in alums.
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PMID:Extraction-spectrophotometric determination of vanadium with 3,5-dinitrocatechol and Brilliant Green. 1896 63

A method has been developed for the synergic extraction and spectrophotometric determination of Ti(IV) with N-hydroxy-NN'-diphenylbenzamidine and thiocyanate. The yellow ternary complex, extracted into chloroform from dilute sulphuric acid medium (pH = 1.5+/-0.1), has maximum absorbance at 390 nm (molar absorptivity 1.3 x 1O(4) 1.mole(-1). cm(-1)). The method is free from interference from a large number of foreign ions and is recommended for the determination of titanium in steel.
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PMID:Synergic extraction and spectrophotometric determination of titanium(IV). 1896 61

Titanium-based electrodes have been demonstrated to be useful for measuring free HF concentration in the range 0.01-0.07M at temperatures between 19 and 61 degrees C in acidic, complexed HF solutions, by measurement of the current density resulting when the electrode potential is approximately +0.6 V with respect to an inert electrode. The current density, i, is linearly related to the HF concentration when the solution is adequately stirred to remove diffusion effects at the electrode, and is independent of HNO(3) concentration up to 1.75M. The dependence on the absolute temperature is ln i = - A/T + B + C ln T, and the activation energy at an absolute temperature T(r) is R(A + T(r)C), where A,B and C are constants and R is the gas constant. For a Ti-2% Pd electrode, the activation energy for anodic dissolution is found to be 43.7 +/- 0.2 kJ/mole at 312 K. The equations relating the current density to HF concentration at different temperatures can be combined to give a single equation for [HF] as a function of both i and T.
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PMID:Metal electrodes for continuous amperometric measurement of free hydrofluoric acid in acidic solutions containing complexing ions. 1896 95


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