Taitiro Fujinaga

Chemical speciation of chromium in sea water: Part 2. Effects of Manganese Oxides and Reducible Organic Materials on the Redox Processes of Chromium

Abstract Experiments designed to clarify the role of manganese oxides in the oxidation process of Cr(III) to Cr(VI) in sea water are described. The theoretical redox equilibrium controlled only by dissolved oxygen is shown not to be always attained for the Cr(III)/ Cr(VI) system in practice. Some naturally occurring materials can reduce Cr(VI) under the conditions of natural sea water.

Chemical speciation of chromium in sea water: Part 1. Effect of Naturally Occurring Organic Materials on the Complex Formation of Chromium(III)

Abstract The effect of naturally occurring organic materials on the coprecipitation behaviour of trivalent chromium is studied to estimate the relative abundance of organic-bound chromium in sea water. Some amino acids and polyhydric organic acids can bind chromium(III) under the conditions prevalent in natural sea water. Some of the chromium(III) in sea water therefore probably occurs in organic species.

Chemical speciation of chromium in sea water: Part 3. The determination of chromium species

Abstract A method for the determination of chromium(III), chromium(VI) and organicallybound chromium in sea water is reported. It is confirmed that sea water contains about 9 × 10 -9 M dissolved chromium. This is shown to be divided as ca. 15% inorganic Cr(III), ca. 25% inorganic Cr(VI) and ca. 60% organically-bound chromium. It is suggested that the inconsistency of earlier results on the dominant chromium species and its concentration in sea water is largely due to the fact that organically bound chromium species were not considered.

Electrochemical studies of sulfonates in non-aqueous solvents: Part III. Trifluoromethanesulfonic acid as a strong acid in dipolar aprotic solvents and acetic acid

Abstract Dissociation of trifluoromethanesulfonic acid in non-aqueous solvents has been investigated mainly by conductometry and compared with that of p-toluenesulfonic, methanesulfonic, fluorosulfuric and perchloric acids. The solvents used are dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, n-butyronitrile, propylene carbonate, acetonitrile, nitromethane, methyl isobutyl ketone and acetic acid. Trifluoromethanesulfonic acid is completely dissociated in rather basic solvents such as dimethyl sulfoxide, dimethylacetamide and dimethylformamide, while it is associated to some extent in the other solvents, especially in methyl isobutyl ketone and acetic acid. The strength of trifluoromethanesulfonic acid is almost the same as that of perchloric acid in all the solvents. Dissociation constants of the other acids are also obtained.

Polarographic reduction of quinoline and its derivatives in non-aqueous solvents

The behaviour of quinoline in DMF solutions containing 0–90% water and the effects of phenol and perchloric acid, indicate the following mechanism for the polarographic reduction of quinoline (the reactions are arranged in order of half-wave potentials). In the presence of less than 20% of water: Wave (A1). RHA + e→RH (when phenol is added) Wave (A2). RH + eαRH− + HA→RH2 (when phenol is added) Wave (B). R + eαR− + H2O→RH + eαRH− Wave (C). R− + eαR2− + 2 H2O→RH2 In the presence of more than 20% of water : Wave (A). RH+ + eαRH + eαRH− + R→RRH− (when perchloric acid is added) Wave (B1). R + eαR− + H2O→RH + eαRH− + R→RRH−, Wave (B2). RRH− + 2 e→R2− + RH−→protonation In solutions containing more than 80% of water, it was observed that wave (B1) was depressed abnormally and the phenomenon is attributed to adsorption of an electroinactive substance on the electrode surface.

Ion-pair effects on the electroreduction of carbonyl compounds in N,-Dimethylformamide

Ion-pair formation effects on the electroreduction of 21 carbonyl compounds were studied systematically in N,N-dimethylformamide (DMF). The degree of the shift of half-wave potentials due to ion-pair formation was observed in the order of p-quinones ρ α -diketones<aromatic ketones<σ-quinones. The thermodunamic properties of several ion associates were evaluated and their structures were discussed, together with the results of the column electrolysis ESR method.

Solid-liquid separation after liquid-liquid extraction

A low-melting solid is used as organic solvent for liquid-liquid extraction at elevated temperatures followed by solidification and decantation of the aqueous phase.

Electron transfer reactions and the nature of the solvent effect on tris-toluene-3,4-dithiolates of rhenium, tungsten, molybdenum and technetium

Abstract The electron transfer reactions of the tris-toluene-3,4-dithiolates of Re, W, Mo and Tc with organic bases have been investigated by means of spectrophotometry and voltammetry. The resultant salts such as [Ph3PH+] [Re(tdt)3−], [o-phenH+] [Re(tdt)3−] were isolated. The so-called solvent effect which is observed on dissolving the complex in a polar solvent such as acetone and dimethylformamide was successfully interpreted in terms of redox reactions between the complex and the dissolved water or solvent.

Electrochemical studies of sulfonates in non-aqueous solvents: Part II. Polarographic reductions of some alkaline earth and transition metal ions with sulfonate supporting electrolyte in N,N-dimethylformamide and acetonitrile

Abstract The effect of p -toluenesulfonate and trifluoromethanesulfonate supporting electrolytes on the polarographic reduction of some alkaline earth and transition metal ions in N,N-dimethylformamide and acetonitrile has been investigated. Trifluoromethanesulfonate behaved similarly to perchlorate in dimethylformamide, while the half-wave potentials in p -toluenesulfonate supporting electrolyte shift to more negative potentials than those in perchlorate. in acetonitrile, the half-wave potentials shift to more negative potentials in trifluoromethanesulfonate than in perchlorate. The effect of the supporting electrolyte on the shift of the half-wave potential can be explained as the ion-pair formation between the divalent cation to be reduced and the supporting electrolyte anion.

Spectrophotometric determination of nickel after separation by adsorption of its α-furildioxime complex on naphthalene

A new method is proposed for collecting traces of nickel from aqueous solution by precipitation as the alpha-furildioxime complex and adsorption of this onto microcrystalline naphthalene. The precipitate is collected, dried, and dissolved in chloroform, and the nickel is determined spectrophotometrically at 438 nm. The linear calibration range is 2-35 mug/10 ml. The molar absorptivity is 1.6 x 10(4) l. mole(-1). cm(-1). The main advantage is that the nickel is collected quantitatively after only a few secondsshaking. The effect of varying pH, amount of reagent, naphthalene or buffer, shaking and standing time, and interferences have been investigated.