No abstract available

[en] A potentiometric titration of 5 to 25 mg uranium is described. Sulphamic and phosphoric acid are added to the sample (volume 1 ml), U VI is reduced to U IV by Fe²⁺ and the excess of Fe²⁺ is oxidized by a mixture of nitric acid, sulphamic acid and ammonium molybdate; vanadyl sulphate is added to ensure a sharp end-point of the titration. The resultant U IV is titrated automatically with 0.02500N potassiumdichromate using a platinum indicator electrode. The automatic titration is performed both with a commercial titrator (Mettler) and with an R.C.N. titrator which waits after each addition until the equilibrium is reached. Using the Mettler titrator an accuracy of 0.05% relative was reached. The R.C.N. setpoint titrator gave results with an accuracy of 0.04% relative at the 20-mg U level. Each titration takes 5 to 7 min. (author)

[en] Geometric optimization techniques useful for studying chemical equilibrium traditionally rely upon principles of euclidean geometry, but such algorithms may also be based upon principles of a non-euclidean geometry. The sequential simplex method is adapted to the hyperbolic plane, and application of optimization to problems such as the potentiometric titration of plutonium is suggested

[en] A potentiometric study on the complex formation of Cu(II) and UO₂(II) with dimethyl diisoxazolone (RH) in (1:1) water-dioxan at a constant ionix strength (μ=0.5) at 31 +- 0.5deg, has been made. The successive formation constants K₁ and K₂ have been determined following Irving and Rossotti method. Log K₁ and log K₂ are computed by graphical methods and are found to be 1.72, 1.61; 1.61,1.23 for Cu(II) and UO₂(II) respectively. The acid dissociation constant ksup(*) of RH has also been determined in (1:1) water-dioxane as well as in (1:1) water-methanol are found to be pksup(*)=2.88 and 2.40 respectively. (author)

No abstract available

[en] The recent advances in the theory and practice of potentiometric, conductometric and optical sensors based on ionophores are critically reviewed. The role of the heterogeneity of the sensor/sample systems is emphasized, and it is shown that due to this heterogeneity such sensors respond to the analyte activities rather than to concentrations. The basics of the origin of the response of all three kinds of ionophore-based sensors are briefly described. The use of novel sensor materials, new preparation and application techniques of the sensors as well as advances in theoretical treatment of the sensor response are analyzed using literature sources published mainly from 2012 to 2014. The basic achievements made in the past are also addressed when necessary for better understanding of the trends in the field of ionophore-based sensors. The bibliography includes 295 references

[en] The original Macdonald and Savage amperometric method scaled down to milligram-sized plutonium samples was further modified. The electro-chemical process of each redox step and the end-point of the final titration were monitored potentiometrically. The method is designed to determine 4 mg of plutonium dissolved in nitric acid solution. It is suitable for the direct determination of plutonium in non-irradiated fuel with a uranium-to-plutonium ratio of up to 30. The precision and accuracy are ca. 0.05-0.1% (relative standard deviation). Although the procedure is very selective, the following species interfere: vanadyl(IV) and vanadate (almost quantitatively), neptunium (one electron exchange per mole), nitrites, fluorosilicates (milligram amounts yield a slight bias) and iodates. (author). 15 refs.; 8 figs.; 7 tabs

[en] After having determined the formation constants of anthranilic acid, the anthranilic acid-Be²⁺ - H₂O system (0.5 M NaClO₃ and t=25 deg C) has been studied. The complex BeA⁺ and the hydroxylated species Be₂(OH)A₂⁺, Be₃(OH)₃A²⁺, Be₃(OH)₃A₂⁺ have been identified

[en] Standard acidity constants, K_a^DMSO (HA), expressed as pK_a^DMSO (HA) values, and anionic homoconjugation constants, K^DMSO_AHA^-, (in the form of lg K^DMSO_AHA^- values) have been determined for 11 substituted phenol-phenolate systems a polar protophilic aprotic solvent, dimethyl sulfoxide (DMSO) with a potentiometric titration. A linear relationship has been determined between lg K^DMSO_AHA^- and pK_a^DMSO (HA). The tendency towards anionic homoconjugation in these systems increases with increasing pK_a^DMSO (HA) that is with declining phenol acidity. The pK_a^DMSO (HA) are correlated with both pK_a^W (HA) water and other polar non-aqeous solvents

[en] Complete text of publication follows. Current methods adopted by the petroleum industry for salinity determination in production water are environmentally impacting due to chemical residue generation. Potenciometric assay ASTMD 6470-99 as well as classical gravimetric methods are recommended for salinity determination in petroleum and its production water; however, high treatment and recovery cost residues are generated by these methods demanding. Clean oil production is a rather attractive approach which might result in more efficient processes whit less environmental damage and reduction on costs of production within this context, development of methods which contem plate high accuracy, low operational and environmental costs are in high demand. The purpose of this study is the determination of salinity in petroleum water formation through an environmental impact less method which is based on the linear combination of density and conductivity measurements. Density, gravimetric and conductometric analysis of 35 test samples of petroleum water formation from two different fields from Espirito Santo sedimentary basin located in Brazilian southeastern continental margin, collected in 2008 were determined. From these data a Partial Least Square (PLS) calibration model was built which showed satisfactory agreement between the classical method determination of salinity (gravimetry) and the linear combination of density and conductivity. In conclusion, method showed excellent results comparable to the classical and instrumental methods with additional advantages such as accurate results, low cost and mainly without generation of chemical residues inherent to the classical analytical process.