[en] In the preceding papers on the complex equilibria between metal ions and aromatic o-hydroxycarboxylic acids, a report was presented on the equilibrium system of uranyl ions and 3-hydroxy-5,7-disulfo-2-naphthoic acid. The computer analysis showed that the data (obtained by means of emf titrations) were well explicable with two successive complexes. The present investigation was made to evaluate the formation of the U0₂²⁺ complexes of 3,5-disulfosalicyclic acid in 0.5 M NaCl0₄ solution at 25⁰C. In this case the computer analysis revealed the formation of more stable complexes: experimental details are given and discussed. (U.K.)

[en] Methods are presented for determination of molybdenum in plant tissue by flame and graphite-furnace atomic-absorption spectrometry and direct-current argon-plasma emission spectrometry. The samples are digested in HNO₃-H₂SO₄-HClO₄ mixture, and Mo is separation and concentrated by chelation and extraction. Three organic solvents (methyl isobutyl ketone,di-isobutyl ketone and isoamyl alcohol) and two ligands (8-hydroxyquinoline and toluene-3,4-dithiol) were studied. The procedures were tested on pine needle and birch leaf samples. (author)

[en] Complex formation equilibria of beryllium(II) with five aliphatic α-hydroxycarboxylic acids, viz. glycolic (HL), lactic (HL), 2-hydroxyisobutyric (HL), L(+)-tartaric (H₂L) and citric (H₃L) acids, were studied by means of potentiometric (glass electrode) titrations at 25 deg. C in an ionic medium of 0.5 M NaClO₄. The titrations were performed in a pH range in which precipitation did not occur. Glycolic and 2-hydroxyisobutyric acid complexation with beryllium(II) are described by the formation of three rather weak complexes, namely BeL⁺, BeL₂ and Be₃(OH)₃L²⁺. Lactic acid was not found to form BeL₂ species. The equilibrium model for tartaric acid constitutes of the three complexes mentioned above together with two deprotonated complexes Be(H_-1L)₂^4- and Be₃(OH)₃(H_-1L). Citric acid was found to form also protonated and binuclear species prior to the formation of hydrolyzed complexes. The p,q,r analysis gave the following set of complexes: BeL^-, BeL₂^4-, Be₂L₂'²'2-, Be₂H_-2L₂^4- and Be₂H_-3L₂⁵ stability constants for these complexes with their standard deviations are reported. (au) 23 refs

[en] Clodronate, disodium (dichloromethylene) diphosphonate tetrahydrate, belongs to a group of diphosphonates of the type P-C-P. Diphosphonates are a class of ligands that are chemically related to, and mimic the physiological behaviour of, pyrophosphates. Clodronate is a synthetic analogue of pyrophosphate, which, together with conventional cancer therapy, has been used successfully for the treatment of hypercalceamia related to osteolytic metastases and malignances. Clodronate has also yielded good results in the treatment of Paget's disease and primary hyperparathyroidism. In this paper a modified version of the procedure of Gallez has been introduced for the determination of clodronate. The method is based on the interference of diphosphonate with the formation of cation-morin (3,5,7,2',4'-pentahydroxyflavone) complexes in slightly acidic solution. The change of the absorbance of a thorium-morin complex was used as a measure of diphosphonate concentration. Interference caused by the major components of human urine has also been examined. (au)

[en] Complex formation equilibria in lanthanoid (III)-3-bromo-5-sulfosalicylate (H₂L^-) system has been studied by potentiometric titration over the pH range 2-9. The measurements were performed in 0.10 M NaClO₄ at 25 deg. C. The data indicate the formation of the species [Ln(HL)]⁺, [LnL], [LnL₂]^3-, [Ln(OH)L]^- and [Ln(OH)₂L]^2-. Enthalpy values were obtained for the [Ln(HL)]⁺ complexes by calorimetric titrations. The mode of complexation was studied by ¹³C NMR spectroscopy. The results are compared with data for complexation by various aromatic hydroxycarboxylic acids. (au) (22 refs.)

[en] The thermodynamic parameters, logβ, ΔH and ΔS for the formation of [Ln(H₂L)]²⁺ complexes between lanthanoid cations and 2,4-, 2,5-and 3,5-dihydroxybenzoate anions (H₂L^-) were determined by potentiometric and calorimetric titrations in aqueous solutions of 0.10 M (NaClO₄) ionic strength and at 25 C. The ΔH and ΔS values of complexation were positive and largely compensatory reflecting that the dehydration plays a major role in the overall complexation reaction. The ¹³C-NMR spectroscopic data indicate that, in all species, the metal ion coordinates mainly to the carboxyl oxygens. The increased stability of 2,4- and 2,5-dihydroxybenzoato complexes compared to that of the 3,5-dihydroxybenzoato and benzoato complexes can be attributed to the electronic effects of the o-hydroxyl groups. (orig.)