Nobutaka Yoshikuni

Aqueous two-phase extraction of nickel dimethylglyoximato complex and its application to spectrophotometric determination of nickel in stainless steel.

A polyethylene glycol (PEG)-based aqueous two-phase system has been established for the extraction of Ni-dimethylglyoximato complex. Appropriate amounts of PEG solution and solid (NH(4))(2)SO(4) were added to the Ni-dimethylglyoximato complex which had been formed in the presence of sodium tartrate and K(2)S(2)O(8) at pH 12 in a separatory funnel and shaken vigorously for about 1min. The mixture was allowed to stand for 10min and then the absorbance of the extracted complex in the upper PEG-rich phase was measured at 470nm. Beers law was obeyed over the range of 0.26-2.1ppm Ni. The proposed extraction method has been applied to the determination of Ni in steel. A steel sample was decomposed with an appropriate acid mixture. An aliquot of the sample solution was taken, treated with H(3)PO(4) and most of the iron and copper were removed by hydroxide precipitation using solid BaCO(3) to control the pH of the sample solution in advance of the extraction of Ni. The analytical results obtained for Ni in steel certified reference material JSS 650-10 (The Japan Iron and Steel Federation), BCS 323 (Bureau of Analysed Samples Ltd.) and NIST SRM 361 and 362 (National Institute of Standards and Technology) were in good agreement with certified values.

Adsorption behaviour of a number of metals on weakly basic ion-exchangers in methanol-hydrochloric acid mixtures

Many metals are not strongly adsorbed on DEAE-cellulose from aqueous hydrochloric acid media. However, some metals can be adsorbed on DEAE-cellulose from methanol-hydrochloric acid media. Distribution coefficients of Zn, Cd, Hg(II) and Bi(III), which show pronounced adsorption, are presented as functions of the methanol and the acid concentrations. Differences in the distribution coefficient between the four metals and a considerable number of other metals are large enough to permit good separations on columns. Among the platinum group metals, Pd(II), Ir(IV) and Pt(IV) are adsorbed from the mixed solvents and may be separated from large quantities of base metals such as Fe(III), Co(II), Ni and Cu(II).

Anion-exchange separation of Te(IV) from Te(VI), Se(IV) and Se(VI) on deae-cellulose in mixed hydrochloric-acetic acid media.

Te(IV) can be separated from Te(VI), Se(IV) and Se(VI) by adsorption of Te(IV) on a DEAE-cellulose column from a mixed 1M hydrochloric acid-acetic acid solution (1:9, v/v). This allows a selective separation of Te (IV) from the other three species in widely different mole ratios.

Ion-exchange separation and spectrophotometric determination of traces of gold

SummaryA combined ion-exchange — spectrophotometric method has been developed for the separation and determination of traces of Au(III) in seven metal ions: Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Se(IV) and Cd(II). Au(III) is adsorbed selectively on a DEAE column from dilute chloride solution, while other metal ions pass through the column. Au(III) is recovered by elution with 1M hydrochloric acid. Traces of Au(III) in the effluent are determined by a new spectrophotometric method, which is based on the formation and extraction of Au(III) — azide — methylene blue complex. Separations of traces of Au(III) from 1000-fold of Pd(II) and Pt(IV) and 10000-fold of Hg(II) are also effected on a DEAE column in mixed methanol 1M hydrochloric acid medium (8 ∶ 2). While Pd(II), Pt(IV) and Hg(II) are retained on the column, Au(III) adsorbs very weakly, so that the separations can be accomplished easily.ZusammenfassungEine mit Ionenaustausch kombinierte spektrophotometrische Methode zur Trennung und Bestimmung von Goldspuren neben sieben verschiedenen Metallionen wurde ausgearbeitet, nämlich neben Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Se(IV) und Cd(II). Das Gold wird an einer Säule aus Diäthylaminoäthylzellulose (DEAE) aus verdünnter Chloridlösung adsorbiert, wobei die anderen Metalle die Säule passieren. Durch Elution mit 1-m Salzsäure wird das Gold wieder gewonnen. Goldspuren im Effluenten werden mit Azid und Methylenblau komplex gebunden und so spektrophotometriert. Von der 1000fachen Menge Pd(II) und Pt(IV) sowie der 100000fachen Menge Hg(II) können Goldspuren auch aus Methanol + 1-m Salzsäure (1∶2) mit einer DEAE-Säule abgetrennt werden. Während Pd(II), Pt(IV) und Hg(II) an der Säule festgehalten werden, wird Au(III) nur sehr schwach adsorbiert, so daß die Trennung leicht gelingt.

Extraction-spectrophotometric determination of traces of palladium with azide and methylene blue

Abstract A sensitive extraction- spectrophotometric method is described for the determination of palladium(II). This is based on the formation of a palladium(II)-azide-methylene blue ternary complex, which is extracted in chloroform from the acetate buffered solution at pH 4.0–5.5. The color develops rapidly and is stable for at least 24 h. The complex system conforms to Beers law up to 15 μg of palladium(II) in the 10-ml chloroform extract at 653 nm. The apparent molar absorptivity is about 5.8 · 104. Few metals interfere in the presence of tartrate; gold(III), chromium(VI), molybdenum(VI), platinum group metals and rhenium(VII) interfere seriously. Sulfate and phosphate do not interfere even in excess.

Rapid dissolution of chromite with sulphuric acid-lithium sulphate mixture containing ceric sulphate, manganese dioxide or periodate, and spectrophotometric determination of chromium.

Cr(2)O(3) and chromite ore can be dissolved in H(2)SO(4)Li(2)SO(4)Ce(SO(4))(2) (20/10/1 v/w/w), H(2)SO(4)Li(2)SO(4)MnO(2) (20/10/1 v/w/w) and H(2)SO(4)Li(2)SO(4)KIO(4) (20/10/2 v/w/w) mixtures. The turbid solution produced can be clarified by treatment with H(2)O(2) or solvent extraction and the chromium determined spectrophotometrically at 614 nm.

Rapid decomposition and dissolution of silicate rocks by fusion with lithium tetraborate and lithium sulphate

Fusion with 1.0 g of Li(2)B(4)O(7)Li(2)SO(4) (2:1) mixture in a platinum crucible at 1000 degrees will decompose 0.1 g of silicate rock in less than 10-15 min, and the cooled fusion cake can be completely dissolved by 20 ml of 1.2M hydrochloric acid at 90-100 degrees in approximately 5 min.

Extraction-spectrophotometric determination of tungsten as tungsten blue

Abstract Tri-n-butyl phosphate (TBP) is used to extract tungsten(IV) from 0.5 M hydrochloric acid containing molybdenum(VI) and other metals. Tungsten(VI) in the TBP solution is reduced by tin(II) chloride and n-butyl acetate is used for dilution. The tungsten blue formed in the TBP/n-butyl acetate medium (1:1) is measured at 615 nm. The apparent molar absorptivity is about 1000 1 mol −1 cm −1 ; calibration graphs are linear in the range 0.1–1.5 mg of tungsten.

Anion-exchange behaviour of metals on deae-cellulose in hydrochloric acid-acetic acid media.

The anion-exchange behaviour of 35 metal ion species on a weakly basic cellulosic ion-exchanger (DEAE-cellulose) in mixed hydrochloric acid-acetic acid media has been investigated. The sorption of metal chloro-complexes on DEAE-cellulose is greatly enhanced with increasing concentration of acetic acid. Differences in sorbability of metals allow many useful analytical separations to be conducted on short columns, containing approximately 1 g of DEAE-cellulose(Cl(-)). Procedures for the chromatographic separations of two-, three-, four- and five-component mixtures are given.

Novel rapid decomposition and dissolution method for silicates using a mixed potassium metaborate/potassium carbonate flux.

A novel method for the rapid dissolution of fused silicates in mineral acid is described. Fusion with 2.5 g of a KBO(2)-K(2)CO(3) (3:2, w/w) mixture in a platinum crucible at 1000 degrees C will decompose 0.1 g of silicate samples such as basalt rock, glass sand and powdered glass in 10 min, and the cooled fusion cakes can be completely dissolved by 20 ml of 3 N mineral acids such as hydrochloric, nitric and sulfuric acids in less than 1 min at about 50 degrees C. Fusion with 5.0 g of a KBO(2)-K(2)CO(3) (3:2, w/w) mixture can completely decompose 0.1 g of chrome refractory in 20 min and the cooled melt can be dissolved by 80 ml of 3 N hydrochloric or sulfuric acids in less than 30 s.