A new spot test for cerium(IV)

Summary A new colour reaction for the detection of cerram(IV) which can be carried out both in a test tube and on a spot plate has been described. The test solution is treated with methylene blue in nitric acid solution (11) to form a rose-red colour. This simple procedure has an advantage over the existing tests in that it is applicable in the presence of oxidising agents like chromium(VI), vanadium(V), nitrate, perchlorate and of coloured ions like copper(II), cobalt(II), nickel(II), chromium(III), iron(III), vanadium(IV), uranium(VI).

---

Zusammenfassung Eine neue, sowohl in der Eprouvette wie auf der Tüpfelplatte ausführbare Farbreaktion zum Nachweis von Cer(IV) wurde angegeben. Die Probelösung wird mit salpetersaurer Methylenblaulösung behandelt und gibt eine rosarote Färbung. Die Reaktion hat gegenüber bekannten Tests den Vorteil, in Gegenwart von Oxydationsmitteln wie Cr(VI), V(V), NO₃ ^–, ClO₄ ^– bzw. in Anwesenheit gefärbter Ionen wie Cu(II), Co(II), Ni(II), Cr(III), Fe(III), V(IV) oder U(VI) anwendbar zu sein.

     

Spectrophotometric Determination of Vanadium in Complex Materials Using N-m-TMBHA and Thiocyanate

Abstract

Vanadium(V) reacts with N-m-Tolyl-p-methoxy benzohydroxamic acid to form 1:2 (metal to ligand) complex containing a basic V=O group and an acidic V-OH group, which forms addition compounds with thiocyanate to give a hyper and bathochromic effect in chloroform. On the basis of this bathochromic effect of thiocyanate a rapid, selective and sensitive method for the spectrophotometric determination of vanadium(V) has been developed. The blue coloured complex of vanadium(V) is extractable in chloroform having absorption maxima at 580nm and max 7100 ±50 1. mole^?1 cm^?1. The method is free from interferences of Mo(VI), W(VI), Zr(IV) and has been successfully applied for the analysis of steels and other complex materials.     

Spectrophotometric determination of vanadium in different oxidation states with pyrogallol

Determination of vanadium at low concentrations is easily performed with pyrogallol as a ligand which forms a bluish-violet complex with vanadium(III), (IV) or (V). The colour of the bluish-violet complex (lambda(max) = 580 nm) contrasts well with the colour of both pyrogallol and vanadium. The complexes are stable for several hours. Beer's law is obeyed over the range 0-14 mug/ml vanadium at pH 6. The apparent molar absorptivity at 580 nm is (7.75 +/- 0.25) x 10(3)1.mole(-1).cm(-1). The effects of diverse ions on the determination of vanadium have been fully studied. Only Mo(VI) and W(VI) interfere seriously. The method is selective, sensitive and can be applied to the determination of total vanadium in a variety of samples.     

Microanalysis with the aid of ion-exchange resins : Part XX1. Detection of nanogram amounts of titanium(IV) with tiron

A sensitive test for nanogram quantities of titanium(IV) is proposed. A resin spot test technique is applied to the colour reaction of titanium(IV) with tiron. The limit of identification is 26 ng of titanium(IV) (1:1.5·10⁶) after 50 min standing. Vanadium(V), chromium(VI), molybdenum(VI) and uranium(VI) interfered seriously. Iron(III) could be masked with EDTA, and iron(III) and titanium (IV) were detected simultaneously.     

Das rutin als anorganisch-analytisches reagens: Nachweis von vanadium(v) mit rutin

A simple, sensitive and highly specific test is presented for the detection of vanadium(V). The test is based on the colour reaction of vanadium(V) with rutin (quercetin-3-rutinosude) in the presence of the ammoniumperoxydisulfate in phosphoric acid.Sensitivity : 0.3 μg vanadium (V) in 1 ml solution.     

Disodium-1,8-dihydroxy-naphthalene-3,6-disulphonate (chromotropic salt) as a reagent in inorganic analysis

Summary The compound disodium-1,8-dihydroxy-naphthalene-3,6-disulphonate (sodium salt of chromotropic acid) is employed as a colorimetric reagent for titanium. It is also known to produce coloured complexes with chromium(VI), vanadium and uranium. In the present paper the formation of colour with forty metallic ions has been studied qualitatively, in neutral as well as in alkaline and acidic media. It has been found that the reagent yields coloured complexes with mercury(I), tin(IV), platinum(IV), gold(III), tellurium(VI), molybdenum(VI), iron(III), aluminium(III), chromium(III), and uranyl(II) besides those recorded above.The colour reactions are particularly sensitive to uranyl(II), iron(III), mercury(I), tin(IV), gold(III) und molybdenum(VI).     

Separation and solvent extraction of vanadium and uranium with n-propyl 2,3,4-trihydroxybenzoate

A spectrophotometric method is described for the separation and determination of trace quantities of vanadium(IV) and (V) from uranium(VI). Vanadium is selectively separated from uranium by extraction at pH 6.5 into n-propyl 2,3,4-trihydroxybenzoate (PTB) dissolved in t-pentanol. Up to 120 microg of vanadium can be determined by measuring the absorbance of the blue complex in the organic phase at 585 nm. Uranium(VI) remains in the aqueous layer and can be determined spectrophotometrically by its reaction with PTB in aqueous acetone to produce a brown-red colour at pH 7.6-8.8. Solutions containing 25-275 microg of uranium absorb at 370-380 nm according to Beer's law. By modification, this procedure can be used for the determination of the two metals in native phosphate rocks. The effects of diverse ions on the determination of vanadium and uranium have also been examined.     

Simultaneous flow injection determination of iron(III) and vanadium(V) and of iron(III) and chromium(VI) based on redox reactions

A flow injection analysis (FIA) method is presented for the simultaneous determinations of iron(III)-vanadium(V) and of iron(III)-chromium(VI) using a single spectrophotometric detector. In the presence of 1,10-phenanthroline (phen), iron(III) is easily reduced by vanadium(IV) to iron(II), followed by the formation of a red iron(II)-phen complex (lambda(max) = 510 nm), which shows a positive FIA peak at 510 nm corresponding to the concentration of iron(III). On the other hand, in the presence of diphosphate the reductions of vanadium(V) and/or chromium(VI) with iron(II) occur easily because the presence of diphosphate causes an increase in the reducing power of iron(II). In this case iron(II) is consumed during the reaction and a negative FIA peak at 510 nm corresponding to the concentration of vanadium(V) and/or chromium(VI) is obtained. The proposed method makes it possible to obtain both positive (for iron(III)) and negative (for vanadium(V) or chromium(VI)) FIA peaks with a single injection.     

Tensammetric determination of microgram amounts of vanadium by catalytic oxidation of o-aminophenol

A tensammetric method is proposed for the determination of microgram amounts of vanadium, based on catalysis of the oxidation of o-aminophenol with sodium chlorate in acidic solution (pH 2.0). The oxidation product gives a very sensitive tensammetric wave; under optimum conditions, the wave-height is proportional to the concentration of va vanadium. From 0.2 to 3.0 mug of vanadium can be determined in a final volume of 50 ml. Mo(VI), W(VI), Mn(VII), Ce(IV) and large amounts of Al(III) and Fe(III) cause positive errors, and Hg(II) and thiosulphate negative errors. Interference from Fe(III), Al(III) and Cu(II) can be eliminated by solvent with oxine at about pH 8.0.     

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.     

Microanalysis with the aid of ion-exchange resins : Detection of nanogram amounts of iron(iii) with ferron

A new ultramicro method for detection of iron(III) is described. A colourless, strongly basic anion-exchangc resin of low cross-linkage in the chloride form is used to enhance the sensitivity of the colour reaction of iron(III) with ferron. The limit of identification of the new “qiresin spot test” is 4 ng of iron(III) (1 : 1·10⁷) after 10 to 20 min and 2 ng (l :2·107) after 50 min. The test is 50–100 times as sensitive as the usual spot test. Serious interferences were observed with cobalt(II), copper(II), chromiuin(VI), uranium(VI) and vanadium (V) ; the elimination of their interferences was also studied.     

Tropoloae as a specific reagent for the determination of vanadium(V)

The blue colour developed on interaction of vanadium(V) with tropolone m 5.5-7.0N acid can be extracted into chloroform. The complex has an absorption maximum at 590 nm. Colour development is instantaneous and the extracted species is stable for 72 hr. Beer's law is followed in the range 1.02-14.25 ppm of vanadium. The molar absorptivity is 4.63 x 10(3)l.mole(-1).cm(-1). Most anions do not interfere. Of the 37 cations examined, only Ti(III), Ru(III), Pt(IV), Ir(IV), Mn(II), Ta(V) and Ce(III) were found to interfere. The interference due to these cations has been removed by masking them with EDTA.     

Spectrophotometric determination of molybdenum(VI)

Molybdenum(IV) gives a red colour with ammonium thiocyanate in 5-8M hydrochloric acid medium, the Sandell sensitivity index being 0.018 ppm Mo(VI)/cm(2). Molybdenum(VI) in 4-7M hydrochloric acid medium forms a red complex with ethyl xanthate and ammonium thiocyanate and this can be extracted into acetophenone. Beer's law is obeyed over the range of 1.2-13.8 ppm, and the Sandell indices at 370 and 470 nm are 0.0016 and 0.0068 ppm/cm(2) respectively. The colour is stable for 40 hr. Most cations do not interfere.     

Extractive-spectrophotometric determination of molybdenum with 4-unsubstituted-5-pyrazolones

A fairly sensitive and selective method for rapid determination of tracer amounts of molybdenum(V) as mixed-ligand complexes with thiocyanate and 4-unsubstituted-5-pyrazolones is described. The red complexes are extractable into chloroform from 1-5M hydrochloric or perchloric acid or 1-3M sulphuric arid media. The molar absorptivities are in the range 1.72-2.15 x 10(4)l.mole(-1).cm(-1) at 455 nm (lambda(max)). The method has been applied to the estimation of molybdenum in various synthetic and alloy-steel samples. In presence of excess of the reagent, Cu(II), Co(II), Mn(II), Fe(II), Fe(III), Al(III), Cr(III), Cr(VI), Ti(III), Ti(IV), Zr(IV), Hf(IV), V(III), V(IV), V(V), Nb(V), Ta(V), W(VI) and U(VI) do not interfere.     

Rapid titrimetric methods for the determination of vanadium and molybdenum in mixtures

Summary A rapid and accurate method has been developed for the volumetric determination of molybdenum(VI) and vanadium(V) in mixtures, using cerium(IV) sulphate. In this procedure the sample solution is reduced in a mercury reductor (to give Mo^V and V^IV) and an aliquot of the reduced solution is titrated with Ce^IV solution using either ferroin, N-phenyl anthranilic acid, or barium diphenylamine sulphate as indicator. This titration gives the amount of molybdenum present, as V^IV does not interfere under the conditions applied. Another aliquot of the reduced solution is titrated with Ce^IV solution and rhodamine 6 G as indicator (observing the quenching of the fluorescence). This titration corresponds to the sum of molybdenum and vanadium. The vanadium content can be calculated by difference.

---

Zusammenfassung Zur schnellen und genauen volumetrischen Bestimmung von Molybdän(VI) und Vanadium(V) in Mischungen wird Cer(IV)-sulfat als Reagens verwendet. Die Probelösung wird im Quecksilberreduktor reduziert (wobei Mo^V und V^IV gebildet werden) und ein aliquoter Teil der reduzierten Lösung wird mit Ce^IV-Lösung titriert, wobei Ferroin, N-Phenylanthranilsäure oder Bariumdiphenylaminsulfonat als Indicator dient. Aus dieser Titration erhält man den Molybdängehalt, da V^IV unter den angewendeten Bedingungen nicht stört. Ein weiterer Teil der reduzierten Lösung wird mit Ce^IV-Lösung gegen Rhodamin 6 G titriert (Endpunkt durch Fluorescenzlöschung), woraus man die Summe Mo + V erhält. Der Vanadiumgehalt ergibt sich aus der Differenz.

     

Liquid-liquid extraction of niobium(V) in the presence of other metals with high molecular mass amines and ascorbic acid

A novel method is proposed for the solvent extraction of niobium(V). A 0.1M solution of Aliquat 336S in xylene quantitatively extracts microgram quantities of niobium(V) from 0.01M ascorbic acid at pH 3.5-6.5. Niobium from the organic phase is stripped with 0.5M nitric acid and determined spectrophotometrically in the aqueous phase as its complex with TAR. The method permits separation of niobium not only from tantalum(V) but also from vanadium(IV), titanium(IV), zirconium(IV), thorium(IV), chromium(III), molybdenum(VI), uranium(VI), iron(III), etc. Niobium from stainless steel was determined with a precision of 0.42%.     

Solvent extraction of metals with hydroxamic acids

Solvent extraction with hydroxamic acids has been investigated. with comparison of aliphatic and aromatic reagents for the extraction of iron, copper, cobalt and nickel. Caprylohydroxamic acid has been evaluated for use in extraction systems for titanium, vanadium, chromium, molybdenum and uranium, both in terms of acidity of aqueous phase and oxidation state of the metal. It has been established that caprylohydroxamic acid in 1-hexanol is a suitable extractant for the removal of titanium(IV), vanadium(V), chromium(VI), molybdenum(VI) and uranium(VI) from 6M hydrochloric acid.     

Determination of vanadium(V) and molybdenum(VI) by means of a Landolt reaction

The determination of vanadium(V) and molybdenum(VI) by a Landolt-type reaction with bromate, iodide and ascorbic acid is reported. For the determination of vanadium(V) the molybdenum(VI) is masked with citrate-citric acid buffer, which also controls the pH. Molybdenum(VI) is determined in the presence of thiourea as masking agent for vanadium(V).     

Catalytic end-point indication in redox titrations

The applicability of catalytic end-point indication to redox titrations is demonstrated by the determination of 3–30 μmol of ascorbic acid (in 22.5 ml of solution) with standard dichromate solution; the chromium(VI)-catalyzed oxidation of o-dianisidine with hydrogen peroxide serves as indicator reaction. Oxidizing substances, such as vanadium(V), thallium(III) or cerium(IV) can be determined by addition of excess of ascorbic acid and back-titration.     

分子内1,3-偶极环加成反应的研究II: 呋喃偶极体系的热及光化学反应

合成并研究了呋喃1,3-偶极C-2-呋喃-N-烯基硝酮(1)的热和光化学反应.1的热化学环加成反应具有区域选择性.生成氧氮杂二环辛烷类化合物.日光灯照明下加热还可得到双键迁移产物.1在波长>302nm下的光化反应产物是氧氮杂环丙烷,而在λ>270nm下除了还有重排产物N-戊烯基-2-呋喃甲酰胺,氧氮杂环丙烷不稳定,加热下通过1发生分子内环加成反应.