Vacuum-thermic extraction (VTE) of toxic and essential elements from rocks with subsequent AAS determination-II.

The method of vacuum-thermic extraction (VTE) of Pb, Zn, Cd, Bi, Tl, As and Sb from soils with subsequent AAS determination of the elements as described previously [1] was adapted to the analysis of rocks. The design of the quartz extractor was improved and appropriate working conditions for a precise and accurate determination were developed. The method was applied to the analysis of various rock types.

Spectrographic determination of impurities in ultrapure tungsten and tungsten oxide.

The effects of an external magnetic field and of the diameter of the anode on the spectroscopic line intensity of the impurity elements in ultrapure tungsten and tungsten oxide have been studied. The results obtained are used for the development of a more sensitive method for the determination of these impurities (Mn, Pb, Fe, Ni, Al, Mo, V, Cu, Cr).

Separation of tellurium(IV) by solvent extraction methods.

A critical review is given of the contemporary state and the perspectives for development of solvent extraction methods for the separation of tellurium(IV). The literature (150 references) is covered up to the end of 1973.

Improved specific separation of selenium by solvent extraction with saturated monoketones.

Acetophenone is the most suitable ketone for extraction of selenium into chloroform. Methods are given for determination of selenium in copper concentrates and metallic tellurium.

Determination of copper, cadmium, lead and bismuth in phosphoric acid solutions by atomic-absorption spectrometry after extraction with diethylammonium diethyldithiocarbamate and butyl acetate.

The possibility of applying diethylammonium diethyldithiocarbamate and butyl acetate for the extraction of copper, cadmium, lead and bismuth from molar solutions of orthophosphoric acid, and from solutions containing up to 55% pyrophosphoric acid and 20% tripolyphosphoric acid has been investigated. Some characteristics of the various diethylammonium diethyldithiocarbamate-butyl acetate-phosphoric acid systems are described. Suitable conditions have been found for flame atomic-absorption spectrometric determination of the ions extracted. This extraction/AAS approach has been used to determine copper, cadmium, lead and bismuth in some iron-, aluminium- and tin-containing samples dissolved in concentrated orthophosphoric acid. The same approach is used for determining 10(-5)-10(-6)% copper, cadmium and lead in orthophosphoric acid and in alkali-metal mono and dihydrogen phosphates.

Study of liquid-liquid extraction of perrhenate with cyclohexanone in different media.

A study has been made of the extraction of ReO(4)(-) from the following media: nitric, hydrochloric, sulphuric and phosphoric acids, and sodium nitrate, chloride, sulphate, carbonate and hydroxide solutions. The extraction curves were obtained and hydration and solvation numbers determined. It is concluded that in acidic medium the extraction follows a hydratosolvate mechanism; in neutral and alkaline medium only a solvate mechanism is observed. Similar investigations were carried out with molybdenum(VI). The separation of rhenium and molybdenum is discussed.

Gas-chromatographic determination of selenium as an organo-selenium compound with acetophenone.

A gas-chromatographic method with electron-capture detection is presented for the determination of selenium after reaction with acetophenone to obtain an organo-selenium compound. This compound is extracted into benzene and chromatographed on an alumina column. The relative standard deviation for the average value (5 mug) is +/-6% (n = 8, P = 95%). The method has been applied to the determination of selenium in metals, alloys, ores and biological samples.

Composition of phosphoric acid solutions obtained when orthophosphoric acid is used as solvent for iron-containing samples by heating: The influence of nitric acid, sulphuric acid and iron(III).

The dissolution of an iron-containing substance in orthophosphoric acid either alone or mixed with nitric acid or nitric acid-sulphuric acid mixture at 270-280 degrees has been examined, to determine the composition of the solutions which are used for analytical determinations. The possibility of condensation of H(3)PO(4) and formation of polyphosphoric acids during the dissolution has been proved. Solutions which may contain pyrophosphoric acid, tripolyphosphoric acid and tetrapolyphosphoric acid have been obtained. The exact composition of these solutions depends on the initial H(3)PO(4) concentration, the heating time, and, in some cases, the presence of nitric acid and sulphuric acid. It is assumed that the nitric and sulphuric acid affect the loss of water and therefore the thermal dehydration of the orthophosphoric acid during the dissolution. No qualitative changes in the phosphoric acid composition have been observed in the presence of Fe(III). Formation of Fe(III) polyphosphates is assumed.

A new catalytic reaction of rhenium and its analytical application.

Small amounts of perrhenate in fairly concentrated sulphuric acid media and in the presence of tin(II) chloride are found to catalyse the acid hydrolysis of alpha-furildioxime, with production of a new absorption peak at 320 nm, due to the di-alpha-furildiketone produced. The catalytically active species is a sulphate complex of rhenium(IV). The catalytic action of rhenium is promoted by citric acid. Rhenium can be determined in the range 0.0005-0.5 mug/ml. Interferences are eliminated by a preliminary extraction. The method has been applied to the determination of rhenium in copper concentrates of low rhenium content, copper ores and rocks. On the basis of the inhibitory effect of molybdenum the reaction can be used for determination of this element as well.

Photometrische ceriambestimmung in gusseisen and legierten stählen mit hilfe von tetron.

It is proposed that traces of cerium in cast iron and high-alloy steels can be determined by oxidising tetron (N,N'-tetramethyl-o-tolidine) with cerium(IV) to yield an intensely orange-yellow product with = 25,300. Cerium can be determined in the presence of a 200-fold excess of Mn, Ti, Cr, Ni, Co, W, Mo, V, etc. The cerium contents of some steels have been determined and the results statistically evaluated.

Gravimetric determination of rhenium as 2,4,6-triphenylpyrylium perrhenate.

A gravimetric method for determination of rhenium is based on formation of sparingly soluble 2,4,6-triphenylpyrylium perrhenate. The conditional solubility product in O.1N sulphuric acid medium was found to be (3.72 +/- 0.08) x 10(-9). The interference of foreign anions (simple or complex) is eliminated by preliminary extraction of perrhenate with acetone from strongly alkaline medium. The method is applied to the determination of rhenium in perrhenates and rhenium alloys.

Spectrophotometric determination of rhenium with dithio-oxamide in strongly alkaline medium.

The interaction between rhenium(VII) and dithio-oxamide in strongly alkaline medium in presence of tin(II) chloride as reluctant has been studied. A purple complex is obtained, with lambda(max) 526 nm and (max) = 4.0 x 10(3) l.mole(-1).cm(-1). The reaction has been applied to the determination of rhenium in tungsten-rhenium alloy after its anodic electrochemical dissolution in alkaline medium. A 1000-fold excess of molybdenum or tungsten does not interfere. A modification of the proposed method can be used as a spot-test for rapid control of rhenium content in industrial solutions.

Substituted ethan phosphonic acid esters as reagents for the separation of molybdenum from rhenium by solvent extraction.

New esters of the ethan phosphonic acids have been synthesized and their extraction properties studied with respect to Mo(VI), Re(VII), Fe(III),Au(III),Tl(III) and Sb(V). A possibility is shown for the analytical separation of molybdenum from rhenium (beta = 700). The state of these new extraction agents in carbon tetrachloride solution, and the mechanism of the extraction processes, have been investigated by means of infrared spectra.

Photometric and spectrochemical determination of gold in iron pyrites, copper and lead concentrates.

A photometric and a spectrochemical method have been developed for determining gold in iron pyrites, copper and lead concentrates. In both, the sample is dissolved and gold is extracted from 1M hydrochloric add solution with a mixture of ethyl methyl ketone and chloroform (1:1). Gold was determined photometrically with N,N'-tetramethyl-o-tolidine. Conditions have been found for satisfactorily sensitive and reproducible spectral determination of gold. For this purpose the effect of various collectors and buffers on the evaporation curves of gold has been studied, as well as excitation conditions, form of the electrodes, optimum slit-width, and photographic variables. The sensitivity and precision of both methods have been evaluated.

Analytical characterization of some pyrazolones and their copolymers with some vinyl compounds.

Some new pyrazolones have been synthesized and their copolymers with styrene, methylmethacrylate and methacrylic acid prepared. The pyrazolones and their styrene and methylmethacrylate copolymers are insoluble in water but form chelate complexes with some alkaline-earth and transition metal ions. The water-soluble methacrylic acid copolymers do not form complexes with these elements, however, probably because of hydrogen-bonding of the chelating groups to the methacrylic acid carboxyl groups. Special attention was paid to the complexation of Au(III), which was assumed to proceed mainly through the nitrogen atoms of the pyrazolone ring.

New chelating sorbents based on pyrazolone containing amines immobilized on styrene-divinylbenzene copolymer-I Synthesis and analytical characterization.

A series of new cheating sorbents has been prepared by modification of styrene-divinylbenzene copolymer with different pyrazolone-containing amines. The substances were characterized by elemental analysis and infared spectroscopy. The complexation ability of the sorbents towards alkali, alkaline-earth, transition and precious metals has been studied. The new sorbents may successfully be applied to the simultaneous preconcentration of alkaline-earth and transition elements in neutral medium and to the selective separation of precious metals in acidic medium.

Investigations of the hygroscopic properties of ammonium sulfate and mixed ammonium sulfate and glutaric acid micro droplets by means of optical levitation and Raman spectroscopy.

In the presented work an optical levitation technique performed by means of a focused laser beam, Mie and Raman spectroscopy have been utilized for measuring hygroscopic growth curves and composition of laboratory generated single ammonium sulfate (AS) and internally mixed ammonium sulfate-glutaric acid (GA) droplets in the micrometer range. The generated particles have been found to immediately supersaturate (above 45wt% for AS) at 297 K after capturing in the laser beam. Further increase of the relative humidity (RH) up to 85% does not dilute the droplets under the saturation point. A spontaneous hygroscopic growth takes place at 73.5-78% RH for pure AS. The particle grows with an average factor of 1.62 at the deliquescence relative humidity (DRH). Efflorescence of AS occurs at 43% RH with a corresponding concentration of more than 85wt%. Independent of the mixing ratios in ranges 25/75, 50/50, 75/25% AS/GA mixed particles don't exist as a metastable supersaturated solution droplets in the 35-85% RH range. Instead of growing with increasing relative humidity internally mixed particles build up a solid crystalline layer on the surface. This crystalline phase is not further influenced by ambient relative humidities.