Extraction of iridium 1-nitroso-2-naphtholate

The extraction of iridium 1-nitroso-2-naphtholate was studied as a function of the heating time of the iridium solution with an acetone solution of the reagent, and as function of thepH and the reagent concentration. It was found that iridium is practically completely extracted by dichloroethane atpH 4.8–5.5. The obtained results are compared with extraction data of iridium compounds with other chelating agents.     

Effect of cobalt(III) 1-nitroso-2-naphtholate on free-radical polymerization to vinyl monomers

It has been shown that, at 70°C, cobalt(III) 1-nitroso-2-naphtholate inhibits the free-radical polymerization of styrene, methyl methacrylate, butyl methacrylate, and butyl acrylate. The induction period linearly increases with complex concentration. The polymerization of styrene (120°C) carried out in the presence of cobalt(III) 1-nitroso-2-naphtholate shows typical features of pseudoliving polymerization, namely, linear ln[M]₀/[M]-time and molecular mass-conversion plots. When the monomers are allowed to stand with a complex (7 × 10^?3 mol/l) and an initiator (5 × 10^?3 mol/l) for 1 day at 20°C, the ESR signal corresponding to the nitroxide radical appears. In the course of polymerization, the signal disappears, indicating the consecutive transformation of the cobalt(III) 1-nitroso-2-naphtholate radical into the macronitroxide adduct. Polystyrene samples isolated at various conversions initiate the secondary polymerization of styrene and its block copolymerization with methyl methacrylate.     

The precipitation of bismuth basic acetate from homogeneous solution

Precipitation from homogeneous solution by urea hydrolysis has been used to investigate the conditions affecting the precipitation of bismuth basic acetate. Evidence has been found that indicates that acetate complexes may be formed. The method has been tested for the determination of bismuth, but is not suitable if lead is present.     

On homogeneous nucleation in barium sulphate precipitation from homogeneous solution

Unsuccessful attempts to induce homogeneous nucleation of barium sulphate by a PFHS technique in which potential hetero-nuclei are removed by a preliminary precipitation are described. In all instances, only heterogeneous nucleation was observed.     

Gravimetric analysis of tantalocolumbites by precipitation from homogeneous solution

An analysis of complex tantalocolumbites has been carried out by precipitation from homogeneous solutions. A homogeneous precipitation of tungsten, titanium, tantalum and niobium by thermal decomposition of the soluble peroxytungstates, described in previous papers, is used. Corrections for incomplete precipitation and coprecipitation phenomena are applied on the basis of the experimentally found values. Silicon and tin are separated by volatilisation as fluoride and iodide, respectively. Iron is extracted by means of isopropyl ether and the rare earth metals are precipitated homogeneously from an oxalate solution. Manganese is precipitated as the ammonium phosphate. The results are in good agreement with an independent method, the standard deviations being within 1 % for the major constituents.     

Optical and chromaticity characteristics of cobalt 1-nitroso-2-naphthol-3,6-disulfonates

The optimum conditions of the complexation of cobalt with nitroso-R salt in the presence of and without ascorbic acid were found. Molar coefficients of chromaticity functions of the complexes were calculated, and it was demonstrated that cobalt(II) and cobalt(III) complexes can be distinguished only with the use of chromaticity functions, whereas their optical characteristics are nearly the same. For practical purposes, it is better to introduce ascorbic acid and to obtain the kinetically inert complex of cobalt(III) with nitroso-R salt.     

Kinetics of the precipitation of palladium dimethylglyoximate from homogeneous solution

The kinetics of formation of palladium dimethylglyoximate in the post-nucleation and pre-nucleation stages, and the effect of palladium on the reaction of biacetyl and hydroxylamine, have been studied.     

Interaction of cobalt(II) chloride with 2-nitroso-1-naphthol in a 96:4 benzene-ethanol solution

The cobalt(II) chloride-2-nitroso-1-naphthol system has been studied spectrophotometrically in a 96:4 (v v ) benzene-ethanol solution. Two species have been found, the M:L complexation ratios of which are 1:1 and 1:2. The concentration quotients of the formation equilibria are K(1) = 1.2 x 10(3) and K(2) = 1.4 x 10(4) respectively. The first step of the reaction is accompanied by a configurational change from a tetrahedral to an octahedral structure.     

Multiple nucleation in the precipitation of nickel dimethylglyoximate from homogeneous solution

Spectrophotometric measurements of undissociated nickel dimethylglyoximate molecules in solution and electron-microscope observations of the precipitated particles have confirmed and extended previous information on the nucleation of nickel dimethylglyoximate precipitated from homogeneous solution. Supersaturated concentrations several hundred times the equilibrium solubility may persist for as long as 2 hr. Nucleation occurs not all at one initial time but rather in multiple "bursts" spread out over several hours.     

Separation and determination of tantalum and niobium by precipitation from homogeneous solution

An attempt to separate niobium and tantalum by precipitation from homogeneous solution by thermal decomposition of their peroxy complexes, in the presence of tannin and oxalate, has been only moderately successful. A more satisfactory separation of tantalum and niobium for ratios from 50:1 to 1:30 is obtained by extracting the bisulphate melt with ammonium oxalate before adding hydrogen peroxide, hydrochloric acid and tannin. For a tantalum/niobium ratio of 1:1 the niobium coprecipitation is reduced to 5 %. Furthermore, two alternative possibilities are presented: (1) a quantitative recovery of a tantalum precipitate at small oxalate and high tannin concentration, leaving 90% of the tantalum-free niobium in solution; (2) an 85 % recovery of niobium-free tantalum at high oxalate and small tannin concentration. A study of the coprecipitation process of niobium shows that the distribution coefficients follow a logarithmic pattern, true homogeneous mixed crystals being formed.     

Gravimetric determination of nickel with quinoxaline-2,3-dithiol by precipitation from homogeneous solution

The investigation of quinoxaline-2,3-dithiol as a gravimetric reagent for nickel is described. A derivative of the dithiol, S-2-(3-mercaptoquinoxalinyl)thiuronium chloride is used as a generating agent in a PFHS method because of its relative stability and solubility in aqueous ethanol. Nickel, 2.5–25.0 μg, can be precipitated at pH 2–3 as (C₈H₅N₂S₂)₂Ni. After filtration the precipitates are washed first with aqueous ethanol to remove traces of absorbed reagent and then with benzene to remove a small amount of decomposition product of the reagent, the characterization of which is described. The precipitates are stable and can be dried in air at 110–120°. Errors of less than 0.15 % are obtained in the analysis of solutions containing 25 mg of nickel. The selectivity of the reagent is discussed and some suggestions are made for masking the interference of other elements.     

Micellar colorimetric determination of iron, cobalt, nickel and copper using 1-nitroso-2-naphthol

1-Nitroso-2-naphthol, an excellent color-forming chelating agent, combines to Fe(III), Co(II), Ni(II), Cu(II) and so on to form slightly soluble complexes in aqueous solution. To determine these metal ions, a tedious and time consuming separation technique, such as liquid-liquid extraction, has often been performed. However, these metal-1-nitroso-2-naphthol complexes could be determined conveniently by ultraviolet-visible (UV-Vis) spectrophotometry in Tween 80 micellar medium that has polyoxyethylene groups. After conditions such as pH, the amount of 1-nitroso-2-naphthol and the stability were adjusted to their optimum values, the sensitivities of the metal ions in Tween 80 medium and in chloroform were compared. It was shown that the sensitivities of Fe(III) and Co(II) in Tween 80 medium were higher than in chloroform, but that of Cu(II) was lower. The interfering effects among analytes ions, Fe(III), Co(II), Ni(II) and Cu(II) were more serious than by other ions, but the interfering effects could be removed by adjusting pH or adding the masking agents such as NH(3) or oxalate. Detection limits of Fe(III), Co(II), Ni(II), and Cu(II) were 0.024, 0.016, 0.039 and 0.023 mug ml(-1), respectively, and the correlation coefficients of these calibration curves were above 0.996. Recovery yields of the metal ions in the mixed standard solution ranged from 96 to 103%, and their coefficients of variation were low ranging between 0.94 and 1.75%. Cu(II) in brass sample and the amount of Fe(III) in steel sample were also determined. This proposed technique is simple, convenient and speedy.     

Immobilized ligands on silica: Uptake of cobalt and other metals by 1-nitroso-2-naphthol

This paper deals with the preparation and properties of a material formed by 1-nitroso-2-naphthol chemically bound on silica. Its uptake ability towards Co(II), Hg(II), Cu(II), Pb(II), Cd(II), Zn(II) and Al(III) was investigated, as well as the conditions for the release of metals previously fixed.     

Basic aluminium succinate: An alumina precursor formed by precipitation from homogeneous solution

Precipitation from a homogeneous solution of aluminium nitrate by neutralisation using urea in presence of succinic acid leads to the formation of a well-defined alumina precursor, basic aluminium succinate, which on calcination yields microspheroidal γ-alumina with excellent free-flowing characteristics.     

Species in the cobalt(II) chloride-2-nitroso-1-naphthol system in benzene-ethanol mixtures

The cobalt(II) chloride-2-nitroso-1-naphthol system in mixtures of benzene and ethanol has been investigated spectrophotometrically. The complexation ratios of the species present have been determined and the values of the respective concentration quotients at equilibrium at 25 degrees have been calculated. These values seem to be dependent to only a small extent on the variation of the mixture composition; the most considerable aspect is the decrease of the complexation ratios with increasing benzene concentration.     

Application of urease for the precipitation of nickel dimethylglyoximate by urea from homogeneous solution

Urease can be used to decompose urea for the precipitation of nickel dimethylglyoximate from homogeneous solution. Optimum experimental conditions, and a procedure giving good separations from other ions, are described.     

Determination of nickel and copper by precipitation from homogeneous solution as their salicylaldimine complexes

A method has been developed for the gravimetric determination of copper and nickel as their salicylaldimine complexes, by precipitation from homogeneous solution. The complexes are crystalline precipitates which are very easy to filter off and wash. The accuracy of the determinations is higher than that of the conventional precipitation method.