Hydrazine sulphate as reagent for titrimetric determination of vanadium(V) and chromium(VI)

Conditions have been developed for the direct titration of vanadium(V) and chromium(VI) with hydrazine sulphate, barium diphenylaminesulphonate being used as indicator and osmium tetroxide as catalyst.     

Resacetophenone isonicotinic acid hydrazone as a reagent for the catalytic polarographic determination of nanogram quantities of vanadium(V)

The polarographic method proposed for 1–12 ng of vanadium(V) is based on the reduction of bromate, catalysed by the metal ion, with resacetophenone isonicotinic acid hydrazone at pH 5.0. Only iron interferes seriously.     

N-hydroxy-N,N'-diphenylcinnamamidine (HDPCA) as a new reagent for extractive separation and photometric determination of vanadium(V)

N-hydroxy-N,N′-diphenylcinnamamidine (HDPCA) forms a blue-violet coloured 1:2 complex (metal:ligand) with vanadium(V), which can be quantitatively extracted into chloroform from 1.0–9.5M acetic acid medium. Based on this colour reaction, a sensitive and highly selective method for the spectrophotometric determination of microgram quantities of vanadium(V) has been developed. The complex shows maximum absorption at 570 nm and obeys Beer's law in the vanadium concentration range 0.6–12.5 μg/ml. The method has been applied to alloy steels.     

N-p-chlorophenylcinnamohydroxamic acid: A new reagent for the microgram determination of vanadium(V)

A new reagent, N-p-chlorophenylcinnamohydroxamic acid, for the rapid solvent extraction and spectrophotometric determination of microgram quantities of vanadium(V) is reported. Vanadium(V) is extracted from a chloroform solution of the reagent, N-p-chloro-phenylcinnamohydroxamic acid, with 4–8 M HCl. The bluish violet extract has maximum absorbance at 545 nm. The extract obeys Beer's law at 545 nm, and the sensitivity of the reagent is 0.008 μg V/ml. The complex is stable for several days. The effects of acidity, reagent concentrations, and diverse ions are discussed.     

Spectrophotometric determination of vanadium as V(III) oxinate

Vanadium(V) is rapidly reduced by dithionite to V(III) which is extracted as the oxinate into carbon tetrachloride. Vanadium is determined by measuring absorbance of the complex at lambda(max) = 420-425 nm with a sensitivity of 0.004 microg/cm(2) and Beer's law range of 0-7 microg/ml . Several mg of some important elements can be tolerated if they are masked. Molybdenum interferes seriously. The method has been applied to synthetic samples, rutile and ilmenite with satisfactory results. Using ordinary reagents and taking 10 min or less in series for a determination, the method has a sensitivity rarely exceeded by others with a much higher tolerance for other elements.     

Use of N-benzyl-2-naphthohydroxamic acid as a highly selective reagent for solvent extraction and spectrophotometric determination of vanadium(V)

N-Benzyl-2-naphthohydroxamic acid extracts vanadium(V) selectively and quantitatively into chloroform from 2-8.5M hydrochloric acid in the presence of Mo(VI), Zr(IV) and Ce(IV). The extraction takes place quickly and gives a stable reddish-violet extract which shows an absorption maximum at 505 nm with molar absorptivity of (5.34 +/- 0.05) x 10(3) 1.mole(-1).cm(-1). The optimum range for the determination is 2.2-7.4 ppm of vanadium(V) in the final solution. The method has been used for the determination of vanadium in steels.     

Use of the vanadium(V)-xylenol orange mixture as an improved reagent for the spectrophotometric determination of traces of hydrogen peroxide

The reaction in V(V)-xylenol orange (XO)-H₂O₂ system was studied by spectrometry. On the addition of hydrogen peroxide to the mixture of vanadium(V) and XO (V-XO reagent), the absorption peak of V(V)-XO complex (λ_max = 582 nm) decreased significantly. The decrease in the absorbance (denoted as ΔA) was proportional to the concentration of hydrogen peroxide. The constant values of ΔA were obtained under the condition of [XO]/[V(V)] = 0.5 ~ 1.2 and in the pH 3.5 ~ 4.5 region. Based on these results, the conditions for the use of the V-XO reagent in the colorimetric determination of hydrogen peroxide were examined in detail. The V-XO reagent was found to be useful for the trace analysis of hydrogen peroxide with high sensitivity, and the data were little affected by the presence of some inorganic and organic substances. The lower limit of the determination is about 1 × 10^?6M.     

Some vanadium(V) complexes as reagents for the photometric determination of alcohols

Vanadiuin(V) com: with an acidic hydroxy group attached to the metal form the crorrresponding.; with alcohols. These esters show a characteristic absorption at 445–480 that alcoholic hydroxy groups can be determined photometrically. The formation constant of the n-butanol esters of vanadium maltolate and 2-methyl-.S-hydroxyquinolinate Were determined in benzene or benzenechloroform (1:1). Simple methods are determined for the determination of alcohol in the concentration range 10^-1–10^-4M.     

Ethylisobutrazine hydrochloride as a selective and sensitive reagent for the spectrophotometric determination of vanadium(V) and its application to vanadium-bearing minerals and alloys

Ethylisobutrazine hydrochloride is proposed as a selective and sensitive reagent for the spectrophotometric determination of vanadium(V). It forms a red-colored species with vanadium(V) in 3.5–6.5 M phosphoric acid medium. An eight-fold molar excess of reagent is necessary for the full development of the color. The red species exhibits an absorption maximum at 518 nm with a molar absorptivity of 9.75 × 10³ liters mol⁻¹ cm⁻¹. Sandell's sensitivity is 5.2 ng cm⁻². Beer's law is obeyed over the range 0.1–6.2 ppm of vanadium(V) with an optimum concentration range of 0.4–6.0 ppm. The effects of acidity, time, temperature, order of addition of reagents, reagent concentration, and the interferences from various ions, are reported. The method has been used successfully for the determination of vanadium in ilmenite and vanadium steels that contain chromium, molybdenum, manganese, nickel, copper, tungsten, and titanium.     

Spectrophotometric determination of vanadium(V) as a mixed thiocyanate-4-pyridone complex

The spectrophotometric determination of vanadium(V) as a mixed thiocyanate-3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX) complex and as a mixed thiocyanate-3-hydroxy-2-methyl-1-(4-tolyl)-4-pyridone (HY) complex is described. The extracted complexes in chloroform have a maximum absorbance at 450 and 650 nm. The optimal conditions for the extraction and spectrophotometric determination of vanadium(V) are determined. The solutions of the V-SCN-HX and V-SCN-HY complexes in chloroform obey Beer's law in the range 1–10 ppm of vanadium, and are stable for at least 24 hr. The molar absorptivity of the method is 6.8 × 10³ liters mol^?1 cm^?1. The molar ratio V:SCN:HX (HY) of the extracted complex is 1:1:2.     

2-(5-Nitro-2-Pyridylazo)-5-(N-Propyl-N-Sulfopropylamino)Phenol as a new analytical reagent for flow-injection spectrophotometric determination of trace vanadium(V)

A flow injection method using 2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol-(Nitro-PAPS) as a new chromogenic reagent is presented for sensitive and rapid determination of vanadium. Nitro-PAPS reacts with vanadium(V) in weakly acidic medium to form a water soluble complex of molar absorptivity of 8.0 × 10⁴L mol^–1 cm^–1 at 592 nm (maximum absorption wavelength), which permits the straightforward application of a flow injection system to the sensitive determination of vanadium. Under the optimum conditions established, a linear calibration graph was obtained in the range 1–120 ng mL^–1. The relative standard deviation for 60 ng mL^–1 vanadium was 2.2% (n = 5) and the limit of detection was 1 ng mL^–1. The sample throughput is about 40 h^–1. Most inorganic and organic anions examined did not interfere even at concentrations of 3000–6000 times of vanadium. Interference from cobalt(II), copper(II) and nickel(II) at 200ng mL^–1 levels can be overcome by the addition of N-(dithio-carboxy)sarcosine. The recoveries for each 20 and 10 ng mL^–1 vanadium added to the river water were 98 and 97%, respectively.The authors express their thanks to Miss Miho Suzuki and Miss Hiroyo Yamada for their experimental assistance in part.     

2-(2-Thiazolylazo)-p-cresol as a spectrophotometric reagent for vanadium determination in the presence of ascorbic acid

The present work describes the use of 2-(2-thiazolylazo)-p-cresol (TAC) as a spectrophotometric reagent for vanadium determination. TAC reacts with vanadium(IV) in the presence of ascorbic acid, forming a red complex with absorption maximum at 525 nm. The following parameters were studied: complex stability, pH effect, amount of TAC, amount of acetate buffer, HEDTA effect, order of addition of reagents and Beer's law validity. TAC can be used for vanadium determination in the pH range 4.6–6.0, with molar absorptivity of 2.11 × 10⁴Lmole^–1 cm^–1 (at525nm). Beer's law is obeyed up to 2.0 g mL^–1. Many cation interferences can be easily eliminated by using HEDTA as a masking agent. Steel reference standards were used to test the proposed procedure and the accuracy and precision obtained were satisfactory.     

Alizarin blue as a specific reagent for the gravimetric determination of copper

A new method for the gravimetric determination of copper was developed, based on the specific precipitation of copper alizarin blue from highly acid solutions. The determination can be carried out in very dilute solutions up to an amount of 2 mg of Cu. Copper can also be determined in alkali cyanide solution after demasking with formaldehyde.     

Nitroso-R-salt as a reagent for the determination of palladium (II)

Summary A procedure for the determination of palladium with nitroso-R-salt is presented. The sensitivity is 0.068 g/cm².

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Zusammenfassung Es wird ein Verfahren von zur Bestimmung Palladium mit Nitroso-R-Salz beschrieben, dessen Empfindlichkeit 0,068 g/cm² beträgt.

     

p-Sulphobenzeneazo-4-(2,3-dihydroxy-5-chloropyridine) as a reagent for spectrophotometric determination of niobium(V)

Niobium reacts with p-sulphobenzeneazo-4-(2,3-dihydroxy-5-chloropyridine) to form an orange-red ML(2) complex having maximum absorbance at 485 nm in citric acid medium at pH 6.0 +/- 0.5. The reaction is slow at room temperature, but complete in 10 min at 60 degrees . The colour is stable for at least 16 hr. The system obeys Beer's law over the concentration range 0.5-8 mu/ml. The molar absorptivity is 5.26 x 10(3)l.mole(-1).cm(-1).     

Bromometric determination of vanadium (V) by hydrazine

A method for the quantitative determination of vanadium(V), based on the reduction of vanadium(V) by hydrazine, has been described. The reduction is carried out in high concentration of hydrochloric acid and the excess hydrazine back-titrated against standard potassium bromate, using the dead-stop end-point procedure. Hydrazine is preferentially oxidized by bromate in presence of vanadium(IV). Accurate results have been obtained over a wide range of vanadium(V) concentration.     

Cacotheline as a specific reagent for the detection of iron(II)

Summary Cacotheline gives a blue colour with iron (II) in the p_H range 5.2 to 7.8 in the presence of a suitable complexing agent like sodium oxalate or sodium citrate. The blue colour is not stable in air. It has now been shown that if the test is carried out in a Thunberg tube with the exclusion of air, the colour is quite stable at p_H 7.4 (McIlvaine buffer). This reaction affords a sensitive test for iron (II). In a test tube reaction, the limit of identification has been found to be 11 g in about 5 ml of solution. On a spot plate, the limit of identification has been found to be 0.5 g and the dilution limit 1100,000. On special Whatman spot filter paper No. 542, the identification limit has been found to be 0.3 g and the dilution limit 1166,000. The test can also be applied to iron (III) after reduction with sodium oxalate under a Philips' Repro lamp. Reducing agents like sodium sulphite, sodium thiosulphate, sodium hypophosphite, thiourea and ascorbic acid which reduce cacotheline to a pink coloured compound, just like iron (II) (in the presence of oxalate, etc.) in an acid medium, do not give the blue colour with cacotheline in the basic p_H range; Sb^III, As^III, U^III, U^IV, Cu^I, Cr^II, Ce^III, Sn^II, V^III, Ge^II, and Ti^III also do not give the blue colour with cacotheline under the conditions where iron (II) answers the test. The colour reaction now developed appears to be quite specific for iron (II).In conclusion, two of us, V. Narayana Rao and Mrs G. Somidevamma desire to thank the Ministry of Education, Government of India for the award of Research Scholarships.See also Z. analyt. Chem. 152, 346 (1956).     

Spectrophotometric determination of vanadium(IV) in the presence of vanadium(V) using Br-PADAP

In the present paper, a simple and sensitive method is proposed for vanadium(IV) determination in the presence of vanadium(V). This is based on the oxidation of vanadium(IV) present in the sample to vanadium(V) by addition of iron(III) cation, followed by a complexation reaction of iron(II) with the spectrophotometric reagent 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP). The iron(II) reacts with Br-PADAP immediately, forming a stable complex with a large molar absorptivity. The vanadium(IV) determination is possible, with a calibration sensitivity of 0.549 g ml^–1, for an analytical curve of 18.8 ng ml^–1 to 2.40 g ml^–1, molar absorptivity of 2.80 × 10⁴ 1 mole^–1 cm^–1 and a detection limit of 5.5 ng ml^–1. Selectivity was increased with the use of EDTA as a masking agent. The proposed method was applied for the vanadium(IV) determination in the presence of several amounts of vanadium(V). The results revealed that 200 g of vanadium(V) do not interfere with determination of 5.00 g of vanadium(IV). The precision and the accuracy obtained were satisfactory (R. S. D.<2%).