Spectrophotometric determination of osmium

Summary m-Amino benzoic acid in large excess reacts with tetra-, hexa- and octavalent osmium at theph range 4.5–6 to give a purple complex having absorption maximum at 500 nm. Beer's law is obeyed for 0.5 to 8 ppm of osmium(VI) and osmium(VIII) with optimum concentration range of 2 to 8 ppm of osmium(VI) and 3 to 8 ppm for osmium(VIII). The per cent relative error per 1% absolute photometric error is 2.8 for both osmium(VI) and osmium(VIII). Ions such as Pd²⁺, Rh³⁺, Ir⁴⁺, W⁶⁺, U⁶⁺, Co²⁺, Hg²⁺, Mg²⁺, Ca²⁺, Ba²⁺, Sr²⁺, Th⁴⁺ and Zr⁴⁺ do not interfere in the determination.Molar ratio method indicates that the reagent first reduces osmium (VIII) and osmium(VI) to osmium(IV), which then probably forms a 11 complex with the excess unoxidised reagent.Part III.: Anal. chim. Acta 22, 306 (1960); cf. Z. analyt. Chem. 177, 291 (1960).     

Oxidations with potassium permanganate in the presence of fluoride

Summary The titration of ferrous iron in presence of fluoride ions in acid medium gives fleeting end points and erroneous results. A method is deviced to overcome this difficulty by oxidising the ferrous with an excess of KMnO₄ in alkaline medium. After mixing the reactants the excess of KMnO₄ is reduced by an excess of Hg₂ ²⁺ ions in presence of H₂SO₄ and fluoride. The remaining mercurous is then titrated with standard KMnO₄ solution.Part III: Issa, I. M., and M. Hamdy: Z. analyt. Chem. 174, 418 (1960).     

Nicotinamidoxime as an analytical reagent

Summary Alkaline solutions of nicotinamidoxime containing traces of nickel(II) give a deep blue color on treatment with iodine. At a p_H of 10.5–11.5 in presence of an excess of the amidoxime the color develops almost instantaneously and is stable for at least 24 hrs. The system adheres to Beer's law in the range of 0.3–10 ppm of nickel, and the optimum range for measurement (1 cm cell) is 3–10 ppm of the metal. The color reaction is highly sensitive (spectrophotometric: 0.014 g Ni cm^–2 at 575 nm identification limit: 0.5 g Ni ml^–1; 12 · 10⁶).All the common anions are without any effect excepting CN^– and EDTA which interfere seriously. Interference of Pb²⁺, Bi³⁺, Al³⁺, Ti⁴⁺, Zr⁴⁺ and Th⁴⁺ can be masked by excess tartrate; while in the presence of Cu²⁺, Co²⁺, Zn²⁺, Mn²⁺ and Fe³⁺, the Ni²⁺ is first separated by the anion exchange method of Kraus and Moore ³ and then determined as usual.From the results of polarographic investigations it has been concluded that in alkaline medium nicotinamidoxime is first oxidized possibly to an azo type of compound which interacts with nickel(II) forming the deep blue color.Part II: K. K. Tripathi and D. Banarjea: Z. analyt. Chem. 168, 407 (1959).     

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).     

Organic azo-dyes in quantitative analysis

Summary Chrom Red Brown 5 RD has been found as a sensitive reagent for the spectrophotometric determination of thorium. Concentrations as low as 1 g thorium/1 ml can be easily determined at wave length 485 nm. Sulphate, chloride, ferric and zirconium ions badly interfere, while Li, Na, K, Ni, Co, Cu²+, Cd, Ca, Mg and Cr³⁺ do not. U⁶⁺ and Ce⁴⁺ are permissible as traces.Part II: Zaki, M. R., and K. Shakir: Z. analyt. Chem. 177, 196 (1960).     

The substitution kinetics of the aqua ligand by cyanide ions in [Ru(TPPS)(CO)(H2O)]4−

Summary The reaction between the title compound, ,,,-tetra(p-sulphonatophenyl)porphynatoaquacarbonylruthenate(II), [Ru(TPPS)(CO)(H₂O)]^4–, and CN^- revealed that only the aqua ligand is substituted even in the presence of a large excess of the nucleophile. The pK _a1 was spectrophotometrically determined as 13.4(5) (at 33.2 °C) and kinetically as 13.44(5) (at 33.6 °C). The rate of aqua substitution was determined as 89(4)m ^–1 s ^–1 at 35.1 °C and the activation enthalpy and entropy as 55.44(1) kJ mol^–1 and-27.90(4) J K^–1 mol^–1, respectively.     

Phenolate complexes of iron(III) in dimethylsulphoxide solution

Summary The formation of complexes between Fe³⁺ and 2,4-dinitrophenol, 4-nitrophenol and 4-methylphenol is studied in dimethylsulphoxide solution. The reaction proceeds almost to completion and the occurrence, in solution, of complexes with higher stoichiometry than 11 is reported for the first time. The following stability constants are determined (25 °C, 0.1 M KClO₄): Fe^III-2,4-dinitrophenolate ₁=1.8×10³, ₂=4.4×10⁵; Fe^III-4-nitrophenolate ₁=1.10×10⁷, ₂=2.5×10¹² ₃=3.9×10¹⁶; Fe^III-4-methylphenolate =1.7×10¹².The binding of a phenolate ligand to iron(III) strongly decreases its affinity for other phenolate ligands. The superior -donor, 4-methylphenolate (OC₆H₄Me)^–, only forms a 11 complex, Fe(OC₆H₄Me)²⁺. The e.s.r. spectrum of this species clearly prove it is a true iron(III) complex and does not contain iron(II), in opposition to recent claims. However, the complex Fe(OC₆H₄Me)²⁺ easily undergoes a ligand-to-metal electron transference. Addition of an excess of 1,10 phenanthroline yields the iron(II) complex [Fe(o-phen)₃]²⁺ instantaneously.     

Stability constants of iron(III) borate complexes

The ultraviolet absorbance data from experiments conducted at constant pH and total iron concentration but variable B(OH)₃ concentration were used to determined the stability constants of FeB(OH) ₄ ²⁺ and Fe[B(OH)_{4 2} ⁺ at 25°C and an ionic strength of 0.68. The estimates obtained were *₁ = 1.0 ± 0.2 × 10^–2 and *₂ = 2 ± 1 × 10^–5, respectively (uncertainties are two times the standard error of the estimates). A calculation of the extent of iron(III) borate formation in ocean water at pH 8.2 shows that iron(III) borates are not a significantly large component of iron(III) speciation in seawater.     

Complexes of metallochromic substances. II

Summary The optimum conditions for complex formation between La³⁺, arsenazo I, and monoarsenazo III were found. The composition, the formation and stability constants of the complexes formed were ascertained. Comparison of the complexing properties of monoarsenazo III and arsenazo III showed the high importance of every arseno-group in the molecule of the reagent.

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Zusammenfassung Die optimalen Bedingungen für die Komplexbildung zwischen La³⁺, Arsenazo I und Monoarsenazo III wurden ausgearbeitet. Es wurden die Zusammensetzung sowie die Bildungs- und Stabilitätskonstanten der gebildeten Komplexe bestimmt. Ein Vergleich der komplexbildenden Eigenschaften des Monoarsenazo III und Arsenazo III zeigte die große Bedeutung jeder Arsonogruppe im Molekül des Reagens.

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See alsoBudínský, B.: Z. analyt. Chem.206, 262 (1964).

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The author wishes to thank Miss L.Krumlová for technical assistance at this work.     

Extraktiv-photometrische Eisenbestimmung als Tris-(Dibenzylsulfoxid) Eisen(III)-rhodanid

Zusammenfassung Die Extraktion des Eisens aus 0,5-n salzsaurer Lösung, die 3% Kaliumrhodanid enthält, in 8%ige Lösung von Dibenzylsulfoxid in Methylenchlorid ermöglicht bei 500 nm die extraktiv-photometrische Bestimmung von 5 bis 100g Fe³⁺ als [Fe(CNS)₃(OS{CH₂C₆H₅}₂)₃]. Es werden neben Bi³⁺, Cr³⁺, Mg²⁺, Zn²⁺ Spezifitäten Fe³⁺: Fremdion = 110⁴, neben Al³⁺, Ca²⁺, Cd²⁺, Co²⁺, Hg²⁺, Mn²⁺, Ni²⁺, VO²⁺, Zr⁴⁺ solche von 110⁵ und darüber erreicht. An verschiedenartigen Beispielen wird die Anwendbarkeit des Verfahrens ausgewiesen.

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Extractive-photometric iron determination as tris(dibenzylsulfoxide) iron(III)-thiocyanate

Summary The extraction of iron from 0.5N hydrochloric acid solution, that contains 3% potassium thiocyanate, into 8% solution of dibenzylsulfoxide in methylene chloride makes possible the extractive-photometric determination at 500 nm of 5–100g of Fe³⁺ as [Fe(CNS)₃(OS{CH₂C₆H₅}₂)₃]. Specifities for Fe³⁺: foreign ion = 110⁴ are attained in the presence of Bi³⁺, Mg²⁺, Zn²⁺, and specificities of 110⁵ and above have been reached in the presence of Al³⁺, Ca²⁺, Cd²⁺, Co²⁺, Hg²⁺, Mn²⁺, Ni²⁺, VO²⁺, Zr⁴⁺. The applicability of the procedure has been demonstrated on various specimens.

     

Zur ma?analytischen Mikrobestimmung von Eisen (III) mit Hilfe von Variaminblau als Redoxindicator

Zusammenfassung Die chelatometrische Bestimmung von 27–550 g Eisen(III)-ionen in 10–20 ml Lösung mit 0,01 m ÄDTE-Lösung gegen den Redoxindicator Variaminblau wird beschrieben. Die Einstellung des pH-Wertes 2–4 der stark sauren Ausgangslösung erfolgt mit Hilfe von 1 n Natriumhydrogencarbonatlösung, wodurch bei Zimmertemperatur eine schnelle Titration durchgeführt werden kann.

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Summary A procedure is described for the chelatometric determination of 27 to 550 g of iron(III) ions in 10–20 ml of solution with 0.01 M EDTA solution using variamine blue as indicator. A rapid titration at room temperature can be achieved, if 1 N NaHCO₃ solution is used for the adjustment of pH 2–4 in the strongly acidic sample solution.

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Dem Direktor des Institutes für Anorganische Chemie, Herrn Prof. Dr. H. Holzapfel, sei für die Möglichkeit zur Durchführung der Arbeit und die gewährte Unterstützung herzlich gedankt.     

Bestimmung einiger pharmazeutischer Wirksubstanzen mit phenolischen Hydroxylgruppen als Eisen(III)-Verbindungen

Zusammenfassung Die Anwendung der Elatographie zur Identifizierung und halbquantitativen Bestimmung organischer, mit Eisen(III)-chlorid farbige Komplexe bildender Substanzen wird beschrieben.

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Summary The elatographic technique is used for the identification and half-quantitative determination of organic substances, which produce coloured complexes with iron(III)-chloride.

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I. Mitteilung: Becker, A. ¹; II. Mitteilung: Becker, A., u. F. Ehinger ².     

Stereochemie von Metallocenen, 20. Mitt.: Die Ermittlung der optischen Reinheit der Methylferrocen-α-carbonsäure (40. Mitt. über Ferrocenderivate)

Zusammenfassung Die optische Reinheit der Methylferrocen--carbonsäure (1) wurde mit Hilfe zweier Methoden ermittelt. Die Isotopenverdünnung unter Verwendung von (²H₁-Methyl)ferrocen--carbonsäure sowie ein Verfahren, das auf der Auswertung der Intensitätsverhältnisse diastereotoper Protonen in denNMR-Spektren der -Phenäthylamide von1 (verschiedener Drehung) beruht, lieferten übereinstimmende Ergebnisse: [] _d für optisch reines1 beträgt 55,6±1,0° bzw. 54±3°. Der durch Racematspaltung von1 gefundene Wert beträgt 51,5±0,8° (bzw. 53±2°)³. Damit sind die Drehungen aller 90, mit1 bereits früher chemisch korrelierten Ferrocenderivate, wenn überhaupt, nur geringfügig zu korrigieren.

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The optical purity of methylferrocene--carboxylic acid (1) was determined by two methods: isotope dilution, employing (²H₁-methyl)ferrocene--carboxylic acid, and a procedure based on the evaluation of the relative intensities of diastereotopic protons in theNMR-spectra of the -phenethylamides of1 having different rotations. By both methods corresponding results were obtained: optically pure1 has an []d of 55.6±1.0° and 54±3°, resp. The value for1 as found by optical resolution is 51.5±0.8° and 53±2°, resp.³. Hence, the rotations of all 90 ferrocene derivatives previously correlated with1 by unambiguous chemical methods have—if at all—to be corrected only slightly.

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Mit 2 Abbildungen

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19. Mitt.:H. Falk undG. Haller, Mh. Chem.99, 1103 (1968).

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39. Mitt.:K. Schlögl undHeidelore Soukup, Mh. Chem.99, 927 (1968).     

Application of ternary complexes in pharmaceutical analysis

Summary The formation of a ternary complex of iron(III) with isoniazid-2-hydroxybenzaldehyde hydrazone(INSH) in a cetyltrimethylammonium bromide(CTAB) micellar medium, leads to a simple, sensitive and accurate spectrophotometric microdetermination of the iron(III), either in pure aqueous solutions or, particularly, in various anti-anaemic formulations. The apparent molar absorptivity of this complex and Sandell's sensitivity at 386 nm were 2.08×10⁴ lmol^–1 cm^–1 and 2.68 ngcm^–2, respectively. The calibration graph which was traced according to the regression line equation, A=3.70×10^–1 C+1.09×10^–3 (r=1.0000; n=28), was rectilinear for 100 ppb to 3.0 ppm of iron(III). The accuracy and the precision of the method could be considered as very satisfactory, since the mean CV% was 0.202 in the range 0.5–3.0 g of iron(III) per ml. The results obtained for iron(III) by the new method and by the o-phenanthroline method, were compared statistically by means of the Student t-test and the variance ratio F-test; no significant difference was found.Parts I and II see [6] and [7]     

Organic azo-dyes in quantitative analysis

Summary Chrom red brown 5RD was used as an indicator for complexometric titration of thorium. The change in the colour at the end-point was from wine-red to yellow. It is recommended that the thorium buffered aliquot should not contain less then 200 g thorium per 10 ml for a precise estimation. A range of p_H from 2.5 to 3.5 has been found satisfactory for such a titration. Ferri, ferro and zirconium ions interfere; they should be separated beforehand.Part I: Zaki, M. R., and K. Shakir: Z. analyt. Chem. 174, 274 (1960).     

Hitting Two Birds with One Stone: Crystal Containing Both Disproportionation Products of the Mixed-Valence Ruthenium(II,III) Carboxylate

The disproportionation of the mixed-valence diruthenium(II, III) trifluoroacetate, [Ru₂(O₂CCF₃)₅] (1), is reported. The overall conversion leads to the triruthenium(II, III, III) and diruthenium(II, II) species according to the scheme: 4 Ru₂ ⁵⁺ 2 Ru₃ ⁸⁺ + Ru₂ ⁴⁺. Both disproportionation products have been isolated and structurally characterized as they cocrystallize in a 2:1 ratio in the form of the acetone adducts to give the complex [Ru₃O(O₂CCF₃)₆·(OCMe₂)₃]₂ [Ru₂(O₂CCF₃)₄·(OCMe₂)₂] (2). Compound 2 conforms to the triclinic space group, P 1 (No. 2), with the parameters a = 9. 9238(5) Å, b = 12. 8388(7) Å, c = 20. 1188(10) Å, = 103. 1390(10)°, = 103. 1210(10)°, = 98. 1650(10)°, V = 2379. 8(2) ų, and Z = 1. The refinement of 747 parameters and 90 restraints resulted in the final R ₁ value of 0. 0454 and wR ₂ = 0. 0971 for 8003 reflections with I 2(I), and R ₁ value of 0. 0697 and wR ₂ = 0. 1071 for all 10, 755 data. The oxidized form is represented by a mixed-valence trinuclear ruthenium complex, [Ru₃O(O₂CCF₃)₆·(OCMe₂ )₃] (2a). This neutral complex possesses a ³-oxo-centered Ru₃O unit with peripheral ligands provided by bridging carboxylates and terminal acetone groups. The core dimensions of 2a indicate a valence-detrapped state in the range of temperatures 295–90 K. The central unit consists of a nearly equilateral triangular array with the Ru–O_(oxo) bond distances of 1. 909(3), 1. 905(3), and 1. 910(3) Å. The reduced form, [Ru₂(O₂CCF₃)₄·(OCMe₂)₂] (2b), is a typical tetrabridged diruthenium(II, II) carboxylate having coordinated acetone molecules at both axial sites. The Ru–Ru double bond in the paddlewheel unit is measured at 2. 2858(8) Å. The mechanistic aspects of the disproportionation and the core conversion in 1 as well as in similar metal trifluoroacetates are discussed.     

Twinned and Disordered Crystal Structure of Solvated Bis[Aqua(2.2.2-Cryptand)Calcium] Hexa(Isothiocyanato)Calcium

Twinned and disordered crystals of solvated bis[aqua(2.2.2-cryptand)calcium] hexa(isothiocyanato)calcium 2[Ca(2.2.2-Crypt)(H₂O)]²⁺ · [Ca(NCS)₆]^4– · Sol (I), where Sol is acetone and/or ethanol and may be water, were synthesized and studied by X-ray diffraction analysis. Structure I (space group P2₁/n, a = 11.841 Å, b = 21.787 Å, c = 12.377 Å, = 90.90°) was solved by the direct method and refined by the full-matrix least squares method in anisotropic approximation to R = 0.079 from 4168 independent reflections (CAD4 automated diffractometer, MoK ). In crystal form, complex I exists as the two aforesaid complex ions [I¹]²⁺ and [I²]^4– in the molar ratio 2 : 1 united through hydrogen bonds. Complex cation I¹ is of the guest–host type. Its Ca²⁺ cation is coordinated by all eight heteroatoms (6O + 2N) of the cryptand ligand and by the O atom of the water molecule; the coordination polyhedron of this Ca²⁺ cation (CN 9) is irregular. The Ca²⁺ cation of complex anion I² (in the crystallographic center of inversion) is coordinated by six N atoms of six neighboring SCN^– anionic ligands; the coordination polyhedron of this Ca²⁺ cation (CN 6) is a slightly distorted octahedron.