A simple method for dissolution of tantalum pentoxide

A simple and reproducible procedure has been developed for the dissolution of tantalum pentoxide. The oxide is fused with potassium nitrate and potassium carbonate in the ratio of 2:5:5. The cooled melt is dissolved in concentrated sulphuric acid. If a tartaric acid solution is desired the sulphuric acid is evaporated and the residue dissolved in 20% tartaric acid solution.     

A critical review of the volumetric methods for the platinum metals

The published methods for the volumetric determination of the six platinum metals have been appraised. The lack of generally applicable and accurate methods is emphasized. No volumetric method has been recorded for the direct application to solutions of platinum metals, ores, concentrates or natural alloys, and only a few for determinations in synthetic alloys such as fire assay beads. Volumetric methods for the platinum metals are characterized by the absence of data concerning methods of dissolution.     

The Microchemistry of the platinum metals

Summary A method is outlined for the separation and determination of small amounts of osmium, iridium and platinum. Osmium and platinum are determined colorimetrically, and iridium is determined by titration. The procedure gives reproducible results, and provides a convenient method for the determination of each of the elements.

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Zusammenfassung Eine Methode zur Trennung und Bestimmung kleiner Mengen Osmium, Iridium und Platin wurde beschrieben. Osmium und Platin werden kolorimetrisch bestimmt, Iridium maßanalytisch. Das Verfahren gibt reproduzierbare Ergebnisse und eignet sich zur Bestimmung jedes der genannten Elemente.

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Résumé On recommande une méthode pour la séparation et le dosage de petites quantités d'osmium, d'iridium et de platine. On dose par colorimétrie l'osmium et le platine et par titrage l'iridium. Le procédé donne des résultats reproductibles et fournit une méthode appropriée pour le dosage de chacun des éléments.

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In honour of the 70th birthday ofFritz Feigl.     

Catalytic kinetic methods for the determination of platinum metals

A review is given of developments over the last two decades in the determination of platinum metals by catalytic kinetic methods.     

A critical evaluation of colorimetric methods for the determination of platinum metals. ii

This paper is the second review of quantitative colorimetric methods for the six platinum metals and covers the period from May, 1953 to March, 1957. Each method is evaluated from the point of view of the optimum concentration range, specified and practical applications to thr assay for platinum metals.     

A rapid and simple method for the determination of trace metals in hair samples by atomic absorption spectrometry

Acid digestion procedures are described for the dissolution of human head hair in routine determinations of cadmium, chromium, mercury, lead and zinc in the same sample solution by means of atomic absorption spectrometry. The techniques employed are atomization in a Massman graphite furnace or in an air—acetylene flame; the cold-vapor cell is used for mercury. The entire analytical procedure is tested with powdered homogenized head hair samples, previously analyzed by other analytical techniques. Comparison of the results demonstrates that the proposed technique is at least as precise and accurate as the other procedures used.     

Selective complexing agents for the trace enrichment of platinum metals

Summary N,N-Dialkyl-N-benzoylthioureas act as selective complexing agents for the enrichment of platinum metals even from strongly interfering matrices. In combination with chromatographic separation techniques of GFAAS as detection method metal determinations in the g- and ng/kg range are possible. A review of the investigations so far been carried out is given.     

Sulphur dioxide complexes of the platinum metals

Summary The structural, chemical and theoretical aspects of the coordination chemistry of sulphur dioxide complexes of the platinum metals have been reviewed. A detailed evaluation of the analogy between nitric oxide and sulphur dioxide ligands has been made, and it has been concluded that although the structural properties of complexes of these ligands are closely related, their oxidative-addition and oxidation reactions differ in many important respects.Reprints of this article are not available.     

A simple method for the purification of fluorine

A simple method for the purification of fluorine gas is described. With the exception of nitrogen and argon, all impurities usually present in commercial fluorine can be readily removed by 1) conversion of O₂ to non-volatile O⁺₂ salts, and 2) a 70 to 63°K trap-to-trap distillation.     

A new method of determining chlorine and bromine in compounds of the platinum group metals by the oxygen flask

A new manner of determining Cl and Br in organometallic derivatives of the platinum group metals by the oxygen flask method is described. No interference by the metallic elements is found if the sample is mixed before ignition with ammonium fluoride.     

A simple method for the alpha-oxygenation of aldehydes

A mild, efficient and general method for the chemospecific alpha-oxygenation of aldehydes is described. Treatment of a series of aldehydes with N-tert-butyl-O-benzoyl hydroxylamine hydrochloride gives the corresponding alpha-oxygenated carbonyl via a proposed pericyclic rearrangement process.     

Potassium thiocarbonate as a precipitant for platinum metals

Potassium thiocarbonate reagent is proposed for the gravimetric determination of ruthenium(III), rhodium(III), palladium(II) and platinum(IV) in a highly acidic medium (pH 0.5-0.7) under suitable conditions. Ni, Zn, Mn(II), Al, Fe(III), Ti(IV), Zr, Th, Ca, Ba, Sr and Mg do not interfere. The largest relative error is 0.7% and the average error 0.2%.     

Modified anthracites as selective sorbents for platinum metals

Methods of preliminary modification were used to obtain activated carbons with low ash content (0.2%), developed π-conjugated electronic system, large surface area, and wide pore size distribution, from exclusively microporous carbons to those of mesoporous type. The adsorption of compounds of platinum-group metals on activated anthracite from single-component (as regards the platinum metal: Pd, Pt, or Rh) and multicomponent (Pd, Pt) solutions containing compounds of concomitant metals was studied.     

Generalized scheme of chemisorption,electrooxidation and electroreduction of simple organic compounds on platinum group metals

A generalized scheme of successive stages for chemisorption, electrooxidation and electroreduction of simple organic compounds from methane to CO₂ on platinum group metals has been developed on the basis of experimental data. The actual pathway of electrooxidation or electroreduction of an organic compound and the yield of the reaction products depend on the ratio between the rates of individual steps which, in their turn, are determined by various factors (potential, temperature, coverage of the surface with H_ads and OH_ads, with reacting and intermediate organic particles, as well as with foreign particles). The accumulation of chemisorbed compounds on the electrode surface depends on the relationship between the rates of their formation and subsequent transformation.     

A simple method for a determination

The a term is a primary parameter that is used to indicate the deviation of the epithermal neutron distribution in the k ₀-standardization method of neutron activation analysis, k ₀-NAA. The calculation of a using a mathematical procedure is a challenge for some researchers. The calculation of a by the "bare-triple monitor" method is possible using the dedicated commercial software KAYZERO^®/SOLCOI^®. However, when this software is not available in the laboratory it is possible to carry out the calculation of a applying a simple iterative linear regression using any spreadsheets. This approach is described in this paper. The experimental data used in the example were obtained by the irradiation of a set of suitable monitors in the NAA #1 irradiation channel of the HANARO research reactor (KAERI, Korea). The results obtained by this iterative linear regression method agree well with the results calculated by the validated mathematical method.     

Microseparation of platinum metals by electrophoresis

Summary An electrophoretic study of the platinum metals, as Pt²⁺, Pt⁴⁺, Os⁴⁺, Ir⁴⁺, Ru³⁺, Rh³⁺, Au³⁺ and Pd²⁺ reveals that quite a large number of electrolytes effectively separate microgram amounts of ternary and quaternary mixtures of the ions into distinct zones. The voltages are maintained at 100 and 200 V for a period of three hours. The sequences of separation are tabulated.

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Zusammenfassung Die elektrophoretische Untersuchung der Platinmetalle Pt²⁺, Pt⁴⁺, Os⁴⁺, Ir⁴⁺, Ru³⁺, Rh³⁺, Au³⁺ und Pd²⁺ ergab, daß zahlreiche Elektrolyte zur Auftrennung von Mikrogrammengen ternärer und quarternärer Mischungen dieser Ionen in scharfe Zonen geeignet sind. Die Spannung wurde dabei auf 100 bis 200 V für 3 Stunden gehalten. Die Reihenfolge der Trennung wurde in Tabellen angegeben.

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Résumé Une étude par électrophorèse des métaux de la mine du platine, tels que Pt²⁺, Pt⁴⁺, Os⁴⁺, Ir⁴⁺, Ru³⁺. Au³⁺ et Pd²⁺, montre qu'un grand nombre d'électrolytes sépare en zones nettement distinctes des ions en mélanges ternaires et quaternaires, en quantités micro. On maintient la tension à 100 et 200 V pendant 3 heures. On présente sous forme de tableaux l'ordre de la séparation.

     

Estimation of metals as sulphides : Estimation of platinum metals

1. It has been shown that all the platinum metals with the exception of osmium can be estimated as sulphide if the solution containing the metal is treated with a large excess of alkali sulphide followed by excess of acetic acid and ammonium acetate. The precipitate of the sulphide can be washed with water, alcohol and ether successively, dried in a vacuum desiccator, and weighed. 2. By the above procedure it is possible to complete the analysis for all the platinum metals within 3 hours, whereas the procedures described in the literature require much longer time —in many cases more than 24 hours. 3. The precipitates obtained by the older procedures were very sticky and difficult to filter. By carrying out the precipitation in the presence of acetic acid and ammonium acetate it has been possible to obtain the precipitate in an easily filterable form. 4. The above method not only provides a very convenient general method of estimating the platinum metals, but also throws interesting light on the formation of thiosalts and the precipitation of sulphides by their decomposition.     

A simple spectrophotometric method for the determination of minoxidil

A simple and sensitive method for the determination of minoxidil using 3-methyl-2-benzothiazolinone hydrazone (MBTH) and Fe(III) as the coloring agent is described. The method is sensitive to permit the determination of 0.5–4.5 μg ml⁻¹ of minoxidil at 500 nm. The accuracy and precision of the method were checked by high-performance liquid chromatography.