Potentiometric titration of plutonium

In the potentiometric titration of plutonium(III), it has been customary to take the equivalence point as the inflection point on a plot of potential vs. volume of titrant.¹ That the stoichiometric end point corresponds to the inflection point does not seem to have been theoretically demonstrated, however. The purpose of this letter is to suggest that these points may not correspond in the potentiometric titration of plutonium(III). Mound Laboratory is operated by Monsanto Research Corporation for USERDA under contract No. EY-76-C-04-0053.     

Potentiometric titration of lignosulfonic acids

The conditions of potentiometric titration of lignosulfonic acids allowing quantitative determination of strongly and weakly acidic functional groups in lignosulfonates were determined.     

Potentiometric titration of diprotic systems

 The approximate nature of Gran’s method of linearization of potentiometric titration curves applied to diprotic systems has been thoroughly investigated. A function involving pH and titrant volume V (which is linearly dependent on V and becomes zero at the first equivalent point of titration of a weak diprotic base with a strong monoprotic acid) has been critically examined and validated by means of widely extended simulated experiments. Accurate experimental confirmation of the theoretical expressions has been obtained by performing many real titrations of the primary standard Na₂CO₃ with HCl. This particular application, analytically significant itself, can be a prototype of analogous applications. Received: 25 March 1996/Revised: 15 November 1996/Accepted: 19 November 1996     

Titrations with extractive end-points: The permanganate titration

A method for titrations with KMnO₄ in coloured solutions is recommended, in which the permanganate ion is extracted as Ph₃MeAsMnO₄ at the end-point. The procedure is satisfactory for titrations with $\text{N}\text{10}$, $\text{N}\text{50}$ and $\text{N}\text{100}$ KmnO₄, and for the back-titration of KmnO₄, in the presence of coloured ions of molar concentrations up to 400 times that of the substance titrated. A stable permanganate, Ph₃MeAsMnO₄.$\text{case1}\text{2}$H₂O, has been isolated.     

Potentiometric titration of diprotic systems

 The approximate nature of Gran’s method of linearization of potentiometric titration curves applied to diprotic systems has been thoroughly investigated. A function involving pH and titrant volume V (which is linearly dependent on V and becomes zero at the first equivalent point of titration of a weak diprotic base with a strong monoprotic acid) has been critically examined and validated by means of widely extended simulated experiments. Accurate experimental confirmation of the theoretical expressions has been obtained by performing many real titrations of the primary standard Na₂CO₃ with HCl. This particular application, analytically significant itself, can be a prototype of analogous applications. Received: 25 March 1996/Revised: 15 November 1996/Accepted: 19 November 1996     

Potentiometric titration of tellurium with a fluoride-selective electrode

Tellurium, as tellurite, can be determined with a fluoride-selective electrode by means of an indirect procedure based on precipitation of tellurite with excess of lanthanum(III), followed by back-titration with standard fluoride. The end-point is located by using the Gran method, and the titrations are suitable for tellurite concentrations above 1 mM.     

Potentiometric titration of trace amounts of mercury with dithiooxamide

Titration with dithiooxamide in potassium hydrogenphthalate medium (pH 5–6) is suitable for the determination of mercury in concentrations above 0.05 ppm. The precision in the range 0.05–1.0 ppm Hg is ? 4%. Significant amounts of sulphate, nitrate, Zn²⁺, Cd²⁺ and Pb²⁺ and small amounts of Ni²⁺, Co²⁺ and Al³⁺ can be tolerated, but Fe³⁺, Cu²⁺ and Ag⁺ interfere.     

Potentiometric titration of gold in ores with potassium iodide

Summary A direct potentiometric titration method for the determination of gold in ores and alloys is described. It is based on the reduction of Au(III) with iodide ions yielding accurate and reproducible results. Detection limit and sensitivity were 0.06 and 0.032 mg/l Au, respectively. The linear response range was between 0.1 and 120 mg/l Au. The method can be used for the routine assay of gold in different kind of samples.     

Direct titration of mercury (i) with potassium permanganate

Mercurous solutions can bc successfully titrated with potassium permanganate in presence of 0.5–1N H₂SO₄ and 1–1.5% NaF at 35–50°C, Sharp end-points arc obtained when the maximum concentration of monovalent mercury after mixing with the other reagents is 0.005N. At higher concentrations the reaction is sluggish and, the end-points arc not sharp.     

Potentiometric titration of molybdenum(V) with ferric alum

Summary The potentiometric titration of molybdenum(V) with ferric alum has now been investigated. The results show that the potentiometric titration of molybdenum(V) is possible at 98–100 C in a carbon dioxide or other inert gas atmosphere in a medium which is 0.5 to 1.0 N in hydrochloric acid. At higher concentrations of hydrochloric acid, there is no steep jump in potential at the end point. In titrations carried out in 0.5 N hydrochloric acid, the potential jump is about 50 mv per 0.1 ml of 0.05 M ferric alum; when the hydrochloric acid concentration is increased to 1.0 N, the potential jump is about 30 mv per 0.1 ml of 0.05 molar ferric alum solution; in titrations with decinormal solutions of the reactants in 0.5 N hydrochloric acid, the potential jump at end point is about 90 mv per 0.1 ml of iron (III) solutionOne of us, Dr. M. Suryanarayana, desires to thank the Ministry of Education Govt. of India for the award of research scholarship.     

Rapid and selective spectrophotometric determination of manganese in steels and alloys using resacetophenone oxime

A sensitive spectrophotometric method is developed for the determination of manganese in aqueous medium. The metal ion forms a yellowish brown coloured complex with resacetophenone oxime (RPO) in ammonium chloride and ammonium hydroxide buffer of pH 10.5. The 1:1 complex shows maximum absorbance at 380 nm with a Beer's law range of 0.09-1.7 ppm. The molar absorptivity and the Sandell sensitivity are found as 2.5 x 10(4) l.mole(-1).cm(-1) and 0.002 mug/cm(2), respectively. The stability constant of the complex calculated by Job's method is 7.5 x 10(5). The interfering effects of various cations and anions are studied. The present method is applied to the determination of manganese in some steel and alloy samples.     

Potentiometric titration of metal ions in ethanol

The potentiometric titrations of Zn2+, Cu2+ and 12 Ln3+ metal ions were obtained in ethanol to determine the titration constants (defined as the at which the [-OEt]/[Mx+]t ratios are 0.5, 1.5, and 2.5) and in two cases (La3+ and Zn2+) a complete speciation diagram. Several simple monobasic acids and aminium ions were also titrated to test the validity of experimental titration measurements and to establish new constants in this medium that will be useful for the preparation of buffers and standard solutions. The dependence of the titration constants on the concentration and type of metal ion and specific counterion effects is discussed. In selected cases, the titration profiles were analyzed using a commercially available fitting program to obtain information about the species present in solution, including La3+ for which a dimer model is proposed. The fitting provides the microscopic values for deprotonation of one to four metal-bound ethanol molecules. Kinetics for the La3+-catalyzed ethanolysis of paraoxon as a function of are presented and analyzed in terms of La3+ speciation as determined by the analysis of potentiometric titration curves. The stability constants for the formation of Zn2+ and Cu2+ complexes with 1,5,9-triazacyclododecane as determined by potentiometric titration are presented.     

Potentiometric titration of hydrogen peroxide with an electropolished stainless steel electrode

The preparation and use of a stainless steel indicator electrode in the accurate potentiometric titration of aqueous hydrogen peroxide are described. The results agree excellently with those obtained by a standard colorimetric weight-titration procedure. The nature of the titration curves, potential changes and the factors affecting them are discussed. Rapid potentiometric titrations directly to the equivalence-point potential are possible, owing to the nature of the titration curve.     

Potentiometric and coulometric titration of 2-thiobarbituric acid

A new method for the determination of 2-thiobarbituric acid, using its reaction with iodine in an alkaline medium is presented. In the volumetric titration with potentiometric end-point detection, the determinability range is 10-400 micromol (1.4-58 mg). In coulometric titration using the biamperometric end-point detection, 0.1-20 micromol (1.4 x 10(-2)-2.9 mg) of 2-thiobarbituric acid was successfully determined.     

Synergistic extraction of cobalt(II) with resacetophenone oxime in the presence of heterocyclic nitrogen and organophosphorous compunds

Equilibrium distribution coefficients have been determined, for the extraction of cobalt(II) with resacetophenone oxime as a function of pH and reagent concentration at ambient temperature. RAPOX forms simple 12 chelate with cobalt(II). Synergistic extraction was observed with pyridine and its methyl derivatives and some organophosphorous compounds. From the extraction equilibrium data, the adduct formation constants of 12 chelate to adducting ligand adducts were evaluated.     

Determination of certain unsaturated hydrocarbons by titration with permanganate in non-aqueous medium

Ion-association complexes of permanganate with tetrabutylammonium can be dissolved in chloro- or bromobenzene and used for photometric titration of certain unsaturated hydrocarbons at 45-50 degrees . MnO(2) is precipitated and must be filtered off before the absorbance is measured.