Precipitation of copper 8-hydroxyquinaldate from homogeneous solution

Copper can be precipitated quantitatively, over a wide range of pH, by 8-hydroxyquinaldine produced from the hydrolysis of 8-acetoxyquinaldine. The copper 8-hydroxyquinaldate can be weighed as either the monohydrate or the anhydrous dichelate. Differences in the appropriate pH conditions, between the PFHS and conventional precipitation methods, and between thorium and copper precipitations from homogeneous solution, are accounted for.     

Precipitation from mixed solvents—I aluminium 8-hydroxyquinolate

The precipitation of aluminium 8-hydroxyquinolate from a buffered acetone-water system has been effected by the volatilisation of the acetone. The use of this procedure results in a precipitate with physical characteristics superior to that obtained in the conventional manner and allows more efficient separation from interfering cations. Separations of 10-mg quantities of aluminium from an equal amount of cadmium as well as separations of 25-mg quantities of aluminium from at least 420 mg of magnesium and twice that amount of calcium can easily be accomplished. These results compare favourably with those obtained by hydrolysis of 8-acetoxyquinoline. A procedure is described for the quantitative determination of 2–10 mg of aluminium.     

Structures of the uranyl 8-hydroxyquinolates

An X-ray investigation of the two uranyl 8-hydroxy-quinolates UO(2).(C(9)H(6)NO)(2).C(9)H(6)NOH (dark red) and [UO(2).(C(9)H(6)NO)(2)](2).C(9)H(6)NOH (orange), has been carried out on the untreated compounds and after recrystallising them from chloroform. The unsolvated compound UO(2).(C(2)H(6)NO)(2) and the residue remaining after dissolving the orange compound in chloroform have also been examined. The investigation shows that the crystals obtained from the red and orange compounds, respectively, after dissolving in chloroform and recrystallising, are identical. The untreated red and orange compounds are different, the latter showing evidence of existing as a polymer, whereas the former is crystalline. On the basis of the results obtained, a structure for the orange compound is proposed.     

Thermogravimetry of some uranium 8-hydroxyquinolates

The thermogravimetric behaviour of UO₂(C₉H₆NO)₂.C₉H₆NOH and [UO₂(C₉H₆NO)₂]₂.C₉H₆NOH prepared by precipitation from homogeneous solution with 8-acetoxy-quinoline has been found to closely resemble that of UO₂(C₉H₆NO)₂.C₉H₆NOH prepared by direct precipitation of uranium^VI with 8-hydroxyquinoline.     

Precipitation of plutonium oxalate from homogeneous solutions

A method for the precipitation of plutonium(IV) oxalate from homogeneous solutions using diethyl oxalate is reported. The precipitate obtained is crystalline and easily filterable with yields in the range of 92–98% for precipitations involving a few mg to g quantities of plutonium. Decontamination factors for common impurities such as U(VI), Am(III) and Fe(III) were determined. TGA and chemical analysis of the compound indicate its composition as Pu(C₂O₄)₂·6H₂O. Data are obtained on the solubility of the oxalate in nitric acid and in mixtures of nitric acid and oxalic acid of varying concentrations. Green PuO₂ obtained by calcination of the oxalate has specifications within the recommended values for trace foreign substances such as chlorine, fluorine, carbon and nitrogen.     

Precipitation of silver chloride from homogeneous solution

Summary The rate of precipitation of silver chloride, produced by the hydrolysis of allyl chloride in aqueous silver nitrate solution and followed by conductance measurements (Part 1), is considered in terms of theHam and theFrisch andCollins theories of crystal growth. In the early stages the precipitation is controlled by an interface process and the rate constants are evaluated for the growth of particles in systems where the [Ag⁺]/[Cl^–] ratio varies over a wide range. In the later stages the growth rate is slower than predicted either by interface or diffusion controlled mechanisms. Particle charge is an important factor in determining both the growth kinetics and the nature of the final precipitate.

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Zusammenfassung Keimbildung und Kristallwachstum von AgClKristallen bei der Hydrolyse von Alkylchlorid in wässeriger Silbernitratlösung wurden im Zusammenhang mit den Theorien vonHam undFrisch undCollins behandelt. Im Anfangsstadium wird das Kristallwachstum durch einen Grenzflächenprozeß bestimmt. Die Geschwindigkeitskonstanten werden für einen weiten Bereich von [Ag⁺]/[Cl^–] diskutiert. In späteren Stadien wird die Wachstumsgeschwindigkeit kleiner als bei grenzflächenoder diffusionsbestimmten Vorgängen. Die Ladung der Partikel beeinflußt die Kinetik des Kristallwachstums und die Natur der Endprodukte.

     

Precipitation of palladium dimethyl-glyoximate from homogeneous solution

Palladium can be quantitatively precipitated from homogeneous solution with dimethylglyoxime generated by the reaction between biacetyl and hydroxylamine. The chelate is precipitated as long yellow needles which are easy to filter and wash. The separation of palladium from platinum and nickel was investigated.     

Precipitation of nickel salicylaldoximate from homogeneous solution

The reaction between hydroxylamine and salicylaldehyde in the presence of nickel ions has been made the basis of the precipitation of nickel salicylaldoximate from homogeneous solution. Conditions for quantitative precipitation of nickel when present alone or with such metal ions as Fe(2+), Cr(3+), Al(3+), Zn(2+), Mn(2+) and Cd(2+) are described. The recommended procedure is shown to be useful in the analysis of a steel sample.     

Precipitation of bis(1,2-cyclohexanedionedioximato)palladium(II) from homogeneous solution

The reaction between hydroxylamine and cyclohexanedione in the presence of palladium ions has been made the basis of the precipitation of bis(1,2-cyclohexanedionedioximato)palladium(II) from homogeneous solution. The procedure provides a means of separating palladium from Cu(II), Co(II), Ni(II) and Pt(IV), and is a simple, rapid and accurate method for determining palladium.     

Precipitation of molybdenum alpha-benzoin oximate from homogeneous solution

Molybdenum alpha-benzoin oximate is precipitated from homogeneous solution by hydrolysis of ethyl monochloroacetate to decrease the pH of an originally alkaline solution containing molybdenum and the oxime. The method can be used for assay of molybdenum compounds and ferromolybdenum.     

Precipitation of zinc ammonium phosphate from homogeneous solution

Urea hydrolysis has been employed to raise the pH for homogeneous precipitation of zinc ammonium phosphate. From 30 to 100 mg of zinc can conveniently be determined by this technique (relative standard deviation 0.2% for 89 mg). The interference of nickel was minimized by using ammonium tartrate as masking agent, but copper could not be effectively masked with the same tartrate. Ammonium tartrate obtained from a different source was found to mask the copper more effectively. Investigations showed that the latter tartrate contained an appreciable amount of ammonium oxalate.     

Precipitation of manganese ammonium phosphate from homogeneous solution

Precipitation of manganese, zinc and cadmium ammonium phosphates from homogeneous solution by decomposition of metal EDTA complexes by boiling with hydrogen peroxide in presence of phosphate has been investigated. Precipitation of Cd is not quantitative, but of Mn is complete in 2 hr, and of Zn in 6 hr.     

Precipitation from homogeneous solution : Precipitation of molybdenum as sulfide with thioacetamide

The determination of molybdenum with thioacetamide by precipitation of molybdenum sulfide from homogeneous solution has been studied. The optimum acidity is about 0.75 N in perchloric acid and a two-fold excess of reagent suffices. Pressure flasks and large excesses of reagent are unnecessary. Heating for 60 min at boiling water -temperatures yields quantitative precipitation.     

Precipitation from homogeneous solution of cations released from ETDA complexes

The suitability of EDTA complexes for use in precipitation of certain cations from homogeneous solution under various experimental conditions can be predicted from a knowledge of the solubility product of the compound to be precipitated and the complex stability constant. A brief review of previous work in the field of masking effectiveness is given. An examination of factors influencing precipitation has been carried out. It is shown that a simple ratio can be used for predicting the likelihood of precipitation at various pH values and that more rigorous theoretical approaches are not necessarily more advantageous.     

Precipitation of nickel and palladium dimethylglyoximates from homogeneous solution

A comparison of the reaction mechanisms by which nickel or palladium dimethylglyoximate is precipitated from homogeneous solution by the reactions of biacetyl and hydroxylamine discloses many differences. Knowledge of the kinetics and mechanism of the reactions can be used to avoid formation of excess dimethylglyoxime, a limitation of the conventional methods of precipitation.     

Precipitation of calcium oxalate from homogeneous solution by cation release

Calcium oxalate can be precipitated from homogeneous solution by oxidation of the calcium/EDTA complex with hydrogen peroxide in boiling solution, in the presence of oxalate ion, at pH 6-8. The method gives large crystals and enables calcium to be determined in the presence of lead, which remains complexed.     

Precipitation of silver/palladium alloy platelets from homogeneous solutions

Dispersed silver/palladium (Ag/Pd) nanoplatelets were prepared by delivering in parallel solutions of mixed metal nitrates and L-ascorbic acid into a nitric acid solution containing Arabic gum. The shape and size of bimetallic nanoparticles varied with the silver/palladium weight ratio and the concentration of nitric acid. The optimum conditions for platelets formation were a palladium content of ~2.0 wt.% and nitric acid concentrations above 1.0 mol dm(-3). The data presented show that both parameters play a critical role in the nucleation and growth of AgPd particles. A mechanism explaining the formation of the bimetallic nanoplatelets is proposed.