Vladimír Veselý

Synthetic inorganic ion exchangers-II Salts of heteropolyacids, insoluble ferrocyanides, synthetic aluminosilicates and miscellaneous exchangers.

A review of the developments during the period 1965-70 in use of heteropoly acid salts, ferrocyanides and synthetic zeolites as ion-exchangers.

Contributions to the basic problems of complexometry-XII: Successive determination of thorium, rare earths and some other elements

Abstract The successive determination of thorium and rare earths with diethylenetriaminepenta-acetic acid (DTPA) and triethylenetri-aminehexa-acetic acid (TTHA) is described. Such a determination cannot be carried out with the commonly used EDTA or diamino-cyclohexanetetraacetic acid (DCTA). By combined titrations with DTPA and TTHA it is possible to determine successively not only thorium and rare earths, but also some bivalent elements which might be present in the material to be analysed.

Contributions to the basic problems of complexometry-IX: The determination and masking of aluminium

Abstract It has been found that aluminium forms complexes with 1,2-diaminocyclohexane tetraacetic acid(CDTA)almost instantaneously, even at room temperature and m the presence of large excess of neutral salts. Contrary to general opinion, it is also possible to mask aluminium with ammonium fluoride at room temperature. If further determinations are being made with EDTA, a concentration of fluoride equivalent to the molar ratio 1:5 to 1:6 is sufficient for screening of aluminium. If the determinations are with CDTA it is necessary to add 30–50% excess of fluoride, corresponding to the molar ratio Al:F = 1:6. These findings has been utilised to develop a very simple and accurate method for the determination of aluminium and iron in their mixtures. Both determinations are based on the back-titration of an excess of EDTA with lead nitrate using Xylenol Orange as indicator. The further possibility of the determination of tervalent chromium, titanium and manganese in the presence of aluminium and iron has been discussed.

1-Hydroxy-ethylidene-1,1-diphosphonic acid as a titrimetric agent.

1-Hydroxy-ethylidene-1,1-diphosphonic acid (HEDPHA) has been proposed as a highly selective titrimetric reagent for thorium. In the presence of 1,2-diaminocyelohexanetetra-acetic acid (DCTA) a soluble binuclear ternary complex, Th(2)(DCTA)(2)(HEDPHA), is formed. The determination of thorium is carried out in a slightly acidic medium, buffered with urotropine, with 0.025M HEDPHA, and Xylenol Orange as indicator. DCTA masks all bivalent metals, rare earths, scandium, yttrium, bismuth, iron, gallium and indium. Only zirconium, titanium, aluminium and large amounts of thallium(III) interfere.

Contributions to the basic problems of complexometry—XV1: Determination of indium and gallium in the presence of each other without the use of a screening agent

Abstract The different complexation reaction of indium and gallium with TTHA (triethylenetetraminehexa-acetic acid) is utilised for the complexometric determination of these elements in mixtures. With EDTA and TTHA indium forms complexes of normal composition (1:1); gallium, however, forms a 2:1 complex with TTHA. To one aliquot of test solution an excess of EDTA is added, to another the same amount of TTHA. Both solutions, after adjustment of pH to 5–5.5, are titrated with zinc solution using Xylenol Orange as indicator. From the consumption of zinc solution in the two titrations the amounts of indium and gallium are easily calculated.

Contributions to the basic problems of complexometry—XIV: Determination of zirconium, thorium and titanium in the presence of each other

Abstract The complexometric determination of zirconium, thorium and titanium in their mixtures is described. These elements can be separated from many others by precipitation with sodium hydroxide in the presence of triethanolamine. It has been found that precipitated zirconium hydroxide has a polymeric structure, which is not destroyed by dissolving the hydroxide in nitric acid. This leads to low results for zirconium. The depolymerisation of the zirconium polymer in different acids has been thoroughly studied and conditions for the reliable complexometric determination of zirconium are described.

Separation of titanium from iron and aluminium

Abstract Titanium can be separated easily from iron and aluminium by precipitation with sodium hydroxide in the presence of triethanolamine. The precipitated titanium hydroxide is filtered on, dissolved in nitric acid, and determined complexometrically. Certain other elements are masked with EDTA. The proposed method is suitable for all types of material containing a considerable amount of titanium, such as Fe-Ti alloys, titanium ores or concentrates, or artificial titanates.

A note on successive complexometric determination of thorium and rare earths

An improved method for successive determination of thorium and rare earths is described. It is based on the EDTA titration of thorium at pH 2 (Xylenol Orange as indicator) followed by addition of acetylacetone-acetone mixture, adjustment of the pH to 5-5.5 with hexamine, and by further EDTA titration of rare earths with the same indicator.

Contributions to the basic problems of complexometry—XX: Determination of calcium and magnesium

A new method for the determination of magnesium in the presence of calcium is described. Calcium is masked with EGTA whilst magnesium is titrated with DCTA with Methylthymol Blue as the indicator. Calcium can be determined in the same solution by back-titration of the excess EGTA with calcium chloride solution. The usual masking agents for iron, aluminium and other heavy metals can be used.

Contributions to the basic problems of complexometry—XIX1: Determination of zinc and cadmium: β-mercaptopropionic acid as a masking reagent for cadmium

Abstract A new method for the successive determination of zinc and cadmium (in the presence of copper) is described. It is based on the masking of cadmium (copper) with β-mercaptopropionic acid (MPA) and followed by direct titration of zinc with triethylenetetraminehexa-acetic acid (TTHA). After the addition of DCTA cadmium is determined indirectly by back-titration with zinc nitrate solution. All titrations are carried out with Xylenol Orange as indicator in a slightly acid medium, where alkaline earth metals are without effect on the results.