H. Khalifa

Applications involving the iodide ion

Abstract A new method is given for the accurate micro- and semimicrodetermination of silver involving precipitation of silver as the sparingly soluble silver iodide and back titration of excess iodide with standard mercuric solution using the silver amalgam as indicator electrode. Amounts of silver ranging from 30 milligrams down to 6.5 micrograms were determined with fair accuracy. Binary mixtures with copper were successfully analyzed. Ternary mixtures have been analyzed by aid of the additional volumetric methods using potassium cyanide as masking agent. The minimum amount of silver was determined with fair accuracy and precision in presence of a cluster of cations of Cu(II), Ba, Ca, Sr, Zn, Co(II), Ni(II), Cr(III), Cd, In, and Mg amounting in total to 22 milligrams. The same amount was determined with requisite accuracy in presence of 56 milligrams of Cu(II).

Applications involving the iodide ion: II. Microdetermination of oxidizing agents use of potassium iodate and periodate as primary standards for mercury(II)

Abstract A new method is given for the accurate microdetermination of a variety of oxidizing agents, including permanganate, chromate, dichromate, iodate, periodate, bromate and cerium(IV), by adding the oxidant to a known excess of standard iodide solution properly acidified with sulfuric acid, followed by titrating excess iodide with mercury(II) potentiometrically using a silver amalgam as indicator electrode. The results are quite satisfactory and the end points are well defined with very sharp potential breaks. Permanganate, chromate, and dichromate were determined with fair accuracy and precision in presence of iron(III), copper(II) and arsenic(V). Further, it was found that the stoichiometry of the reaction between iodide and the above oxidants is still maintained even with very low concentrations. Another interesting and very sensitive method is investigated for the microdetermination of iodate and periodate involving reduction with sulfurous acid, prior to potentiometric titration of the resulting iodide as mentioned above. The results indicate that potassium iodate and periodate are excellent primary standards for mercury(II).

Potentiometric determination of titanium(III), tin(II), and some hydrazine derivatives

Abstract A new potentiometric method had been used for the accurate determination of titanium(III), tin(II), isoniazid, nicotinic acid hydrazide, semicarbazide, 1,5-diphenylcarbazide, and p -hydrazinobenzoic acid by using alcoholic iodine solution as oxidant. A mercury(II) solution was used as titrant for the iodide produced and silver amalgam as the indicator electrode. The potential breaks were sharp and the methods were highly accurate.

Applications involving the iodide ion: IV. Potentiometric micro- and semimicrodetermination of palladium analysis of mixtures

Abstract An excellent procedure for the quantitative determination of micro- and milligram amounts of palladium is given, in which it is precipitated as the insoluble diiodide and the excess of iodide is back titrated with mercury(II) using silver amalgam as the indicator electrode. All inert cations towards iodide do not interfere. Ferric iron and copper(II) are masked with citrate. The method is sensitive to a minimum of 1.65 ppm of palladium determined with a potential break of 140 mV/0.1 ml of 2.45 × 10 −4 M titrant. Binary and ternary mixtures are successfully analyzed by aid of the present method, masking agents, and additional volumetric procedures.

Some observations on the microdetermination of sulfite, sulfide, and thiosulfate by mercurimetric titration

Optimum conditions have been investigated for the mercurimetric titration of sulfite, sulfide, and thiosulfate by potentiometry via their reaction with mercury(II) using silver amalgam and SCE electrode combination. Possible schemes for these reactions were suggested. For microdetermination of these anions, the standard deviation, coefficient of variation, and percentage recovery were calculated indicating the high accuracy and reliability of the applied procedures. Significant correlation between the suggested procedures and the other standard methods was tested and confirmed by applying F and t tests.

Applications involving the iodide ion: III. Determination of iodide in presence of some complexing agents; analysis of binary and ternary mixtures of silver with some metal ions

Abstract The effect of some complexing agents on the potential end point breaks in titrations of iodide with mercury(II) is studied. Iodide and complex ions (EDTA and CDTA) are determined simultaneously. The slight errors involved, are attributed to the solvent action of EDTA or CDTA on the precipitated mercuric iodide. In almost all cases the end points indicating iodide are stoichiometric, though the corresponding inflections are smaller than those obtained in absence of complexing agents; the decrement is dependent on the concentration of the complexing agent. Trials to analyze simultaneously binary and ternary mixtures of silver plus a variety of cations, which form stable complexes with EDTA were successful. A correction procedure is adopted to minimize the observed errors.

Redox properties of cobalt(III) mixed ligand complexes. II. Redox titration of some organic and inorganic substances potentiometrically

Abstract A stable solution of (cobalt(III)(salen))2O2 was prepared under optimum conditions for its use for the potentiometric determination of xylenols, hydroquinone, sodium thiosulfate, and sodium metabisulfite, by iodide reduction of unreacted cobalt(III) complex and back titrating excess iodide with mercury(II) using silver amalgum and SCE combination. The possible schemes for the course of the redox reactions were suggested. The procedure was also evaluated in comparison with those mentioned in the literature.

The potentiometric microdetermination of aminophenols with iodate and periodate

Abstract Iodates and periodates were used for potentiometric microdetermination of o-, p-, and m-aminophenols, by iodide reduction of unreacted iodates or periodates and back-titrating excess iodide with mercury(II) using silver amalgam and SCE electrode combinations. Possible schemes for these reactions are suggested. The standard deviations ranging from 0.005 to 0.0161 indicate the high accuracy and reliability of the applied procedure.

Spectrophotometric determination of palladium using arsenazo I

Abstract A new simple rapid method for the spectrophotometric determination of palladium using arsenazo I is given. The optimum conditions favoring the formation of the complex are extensively investigated; the molecular structure was found to be 1:1. Beers law is obeyed for the ranges 1.0–10.6 or 0.64–6.39 ppm of Pd.

Applications, involving the iodide ion: VIII. Direct and indirect determination of mercury(I) and analysis of mixtures. Analysis of chromium(VI)-chromium (III) mixtures. Determination of hypochlorite

Abstract Mercury(I), down to 3 ppm, has been accurately determined by direct titration with iodide or by back-titrating excess of iodide with mercury (II) using silver amalgam as the indicator electrode. The direct method and additional volumetric ones were applied to the rapid analysis of various mixtures involving mercury(I) with fair accuracy and precision. Analysis of Cr(VI)-Cr(III) mixtures involved potentiometric back-titration of excess iodide and of excess EDTA separately with mercury(II). Back-titration of excess iodide was successfully applied to the determination of hypochlorite.