The determination of nickel with dimethylglyoxime in the presence of iron and cobalt

A method for the determination of nickel in the presence of both ferric iron and cobalt is presented. The nickel is precipitated directly with dimethylglyoxime, without the prior reduction of the iron. The interference of the iron and cobalt is eliminated by the addition of N,N-dihydroxyethylglycine, which chelates the iron and prevents the formation of the iron-cobalt-dimethylglyoxime contaminant.     

Determination of submilligram amounts of cobalt by ferricyanide titration with photometric end-point detection

The titrimetric determination of cobalt^II by oxidation with hexacyanoferrate(III) in ammoniacal solution, ordinarily carried out potentiometrically, can be extended to smaller amounts of cobalt by means of photometric end-point indication.     

The photometric titration of mercury with trien

A mercury(II) solution containing copper ion can be titrated photometrically at pH 4.7 with triethylenetetramine solution (trien) after the addition of iminodiacetic acid (IDA) ; IDA causes a reversal of the effective formation constants of Hg-trien and Cu-trien and permits the titration. Copper-trien which absorbs at 580 mμ serves as the indicator for the titration. Mercury can be determined in presence of many other metals with an accuracy of about 1%; the main interferences are iron-(III), nickel, bismuth and chloride ion.     

Direct photometric titration of tellurium

A direct photometric titration method has been developed for the determination of tellurium. Tellurium(IV) is titrated with potassium dichromate in 2-6M nitric acid (or 1-4M perchloric acid) at 380-430 nm (blue-violet filter). Selenium(IV) does not interfere.     

Determination of lanthanum by flame photometric titration

The flame emission of lanthanum at 560 mmu decreases linearly with phosphate concentration until a 1:1 molar ratio is reached, and then remains practically constant. Lanthanum can be titrated with phosphate, the equivalence point being detected from the change in emission intensity. Errors due to consumption of solution by the atomizer can be kept low by using short spraying times and low galvanometer damping. The average error is about -1% for 0.1M solutions and less than -5% for 0.01M. The method gives good results in the presence of titanium(III), zirconium, thorium and aluminium but cerium(III) and yttrium seriously interfere.     

Contributions to the basic problems of complexometry-XXI: determination of nickel in the presence of cobalt

A new method for the determination of nickel in the presence of cobalt, based on the masking of the cobalt with potassium cyanide and hydrogen peroxide, is proposed. The yellow, or orange-yellow, complex of cobalt(III) is formed, from which cobalt is not displaced upon the addition of silver nitrate. Tetracyanonickelate, however, reacts quantitatively with silver nitrate, and the displaced nickel can be determined directly with EDTA, using Murexide as indicator. Up to 30 mg of cobalt can be tolerated in the solution.     

Eriochrome black A as reagent for spectrophotometric microdetermination of cobalt in presence of nickel

Summary Eriochrome black A has been found to be a suitable reagent for the spectrophotometric determination of microgram quantities of cobalt in pure cobalt solutions and in the presence of nickel and some other cations by measuring the decrease in the absorbance of Eriochrome black A at p_H 10, caused by the presence of cobalt.Many foreign cations especially nickel were completely masked by EDTA. Amounts as low as about 0.9 to 3 g were determined with fair accuracy.     

Reactions of pyrrole-2,5-dicarbaldehyde with 2-aminodiphenylamine in the presence of nickel and cobalt trimethylacetates

The reactions of pyrrole-2,5-dicarbaldehyde (1) with 2-aminodiphenylamine (3) taken in a ratio of 1 : 2 in the presence of polinuclear nickel(ii) and cobalt(ii) trimethylacetate complexes were studied in MeCN. The reaction with Ni₉(HOOCCMe₃)₄(₄-OH)₃(₃-OH)₃(OOCCMe₃)₁₂ (2) afforded the mononuclear complex Ni(OOCCMe₃)₂[(PhHN)C₆H₄NHCHC₄H₂NCHNC₆H₄(NHPh)] (4) with a new ligand, which is the product of condensation of one molecule 1 with two molecules 3 and contains two NHPh groups. By contrast, the reaction with the polymeric complex [Co(OH) _n (OOCCMe₃)_2–n ] _x (5, n = 0.05—0.1) gave rise to the tetranuclear complex Co₄(₄-O)(-OOCCMe₃)₄L₂ (6), where L is, apparently, the product of further oxidation of Schiff"s base to the benzimidazole derivative. The structures of compounds 4 and 6 were established by X-ray diffraction analysis.     

A fast photometric titration for the standardization of dithizone solutions

A simple method is reported for standardizing 10^?5–10^?4 M dithizone solutions for titrimetric analysis. Dithizone in an anhydrous acetic acid/chloroform (4% v/v) medium is titrated with 2 × 10^?4 M mercury(II) acetate in the same medium. The titratioin takes only a few minutes. The accuracy (+0.2%) and precision (r.s.d. = 0.7%) achieved are similar to those obtained by the classical extractive titration with silver(I).     

Sorption of nickel and cobalt ions onto cobalt and nickel ferrites

The corrosion of the metal parts in the primary circuit of pressurized water reactors leads to the release of colloidal particles (NiFe(2)O(4), CoFe(2)O(4), NiO, Ni...) and ionic species (Co, Ni, Cr...). Particles can interact with ionic species in the primary medium, contributing to their transport and to their deposition onto surfaces outside the neutron flux generating radioactive contamination. Sorption and zetametry experiments at 25 °C were performed on the Ni(2+)/CoFe(2)O(4) and Co(2+)/NiFe(2)O(4) systems in order to determine the behaviour of corrosion products in the fluid of the primary circuit. Sorption appears as surface complexation starting from pH 6 and is followed by precipitation of hydroxide above pH 7.5. Complexation and solubility constants were obtained from the modelling of sorption curves. The two oxide systems present a very similar sorption behaviour, but some differences, due to their different isoelectric points, could be observed on zetametric measurements.     

The photometric determination of cobalt by extraction with b -nitroso-a-naphthol

An improved procedure has been described for the photometric determination of cobalt by extraction of the β-mtroso-α-naphthol complex with chloroform. This procedure can be applied in the presence of large amounts of foreign elements. Interfering elements are: gold, palladium, platinum and copper (above 25 mg).The method has been applied to the determination of cobalt in steels, non-ferrous alloys and nickel.     

The titration of nickel with edta at ph 2.8

A method for determining nickel using EDTA is described. A small excess of EDTA is added, the pH adjusted to 2.7–2.9 and the solution back-titrated with thorium nitrate, against ahzarin-S as indicator. Quantities of cobalt up to 10 mg do not interfere.In addition an approximate determination of the complex-forming constant of Th-EDTA is described, based on the decrease in extinction of an Ni-EDTA solution to which Th⁺⁴ has been addd.     

Determination of methylmercuric ions by photometric titration with dithizone

A rapid photometric titration titration technique, which makes it possible to determine methylmercuric ions with a sensitivity of 15mug, is described. The titration takes place in 80% aqueous ethanol, which is capable of dissolving the titrant, a chloroform solution of dithizone. It has thus been possible to avoid the difficulties arising from co-extraction phenomena that occur when the extractive titration procedures developed for mercury(II) are applied to the determination of methylmercuric ions. A formate buffer is used to keep the pH in the range 2.5-3.0. The attainable precision is considerably better than 1 %.     

Amperometric titration of cobalt and nickel with sodium diethyldithiocarbamate at zero applied voltage using rotating wire-platinum electrode

Analytical and Bioanalytical Chemistry -