Kazuo Aomura

Spectrophotometric determination of copper with α, β, γ, δ-tetraphenylporphine trisulfonate

Water-soluble porphyrin, α, β, γ, δ-tetraphenylphorphine trisulfonate (TPPS, H2R), was found to be a very useful agent for both the direct spectrophotometric determination and the photometric titration of copper(II). The molar absorptivity of H4R2+ at 434 nm is 5.0·105 and the spectrophotometric sensitivity is 0.00013 μg Cu cm−2 for A=0.001. Beers law is followed in the range 0.006 μg–0.06 μg Cu ml−1. Among twenty-two elements examined, only zinc(II) seriously interfered. Acid dissociation constants and salt effects on the spectra of TPPS were evaluated.

The extraction-spectrophotometric determination of chromium(III) with 4-(2-pyridylazo)-resorcinol

Abstract The extraction-spectrophotometric determination of chromium(III) with 4-(2-pyridylazo)-resorcinol (PAR) is described. PAR(H 2 R) forms a 1:3 complex with chromium(III) in a boiling acetate buffer solution at pH 5. The complex forms an ion-association compound with tetradecyldimethylbenzylammonium ion (TDBA + ):Cr(R)(HR) 2 - -TDBA + which can be extracted into chloroform, the molar absorptivity being 4.7 ·10 4 at 540 nm. If EDTA is added as a masking agent after the Cr(HR) 3 has been formed, only iron, cobalt and nickel interfere seriously, and the method can be made specific for chromium by a preliminary extraction of these metals with cupferron. The sensitivity of the method is seven times higher than that of the diphenylcarbazide method.

Extraction equilibria for the 4-(2-Pyridylazo)-Resorcinol-Nickel(II)-Quaternary-Ammonium salt system

Abstract The extraction equilibria of nickel(II)-PAR complexes with tetradecyldimethylbenzylammonium chloride(Q+Cl−) are investigated. Two kinds of nickel complex are extracted by chloroform: Ni(HR)2,nQ+Cl−(0)(ϵ500 = 3.73·104l mol−1cm−1) at about pH 5 and 2Q+ NiR2-2(o)(ϵ500 = 8.08·104 l mol−1 cm−1) at above pH 8.5. The extraction constant for 2Q+ NiR2-2(o) was evaluated as [2Q+ NiR2-2]0/[NiR2-2] [Q+]2 = 1011.16 at μ = 0.1 (Na2SO4. Synergic extraction studies of the Ni(HR)2 species under slightly acidic conditions show that the species is Ni(HR)2(H2O)2in auqeous solution and is extracted into chloroform as the adduct Ni(HR)2(TBP)2 (ϵ535 = 3.57·104 l mol−1 cm−1. Based on the extraction behavior of these complexes, the structures of the Ni2+—PAR complexes are discussed.

Acid dissociation reaction of palladium-4-(2-pyridylazo)-resorcinol complexes

Abstract Palladium(II) formed four kinds of stable 1:1 chelates with 4-(2-pyridylazo)-esorcinol (PAR or H 2 R): below pH 4. a green chelate [Pd(H 2 R)H 2 O] 2+ e= 1.75·10 4 at 440 nm and e=8.63·10 3 at 580 nm); at pH 4–7 two kinds of red helate [Pd( HR)H 2 O] + (e= 2.68·10 4 at 515 nm) and [Pd(R)H 2 0] 0 (e=2.89·10 4 at 525 nm); and at pH 8–11 a red chelate [Pd(R)OH] - (e=3.25·10 4 at 520 nm). The acid dissociation constants of the chelates were estimated as K a1 =[Pd(HR)H 2 O + ] [H + ]/[Pd(H 2 R)H 2 O 2+ ]=10 -4.35±0.05 and K a2 =[Pd(R)H 2 O]· [[H + ]/[Pd(HR)H 2 O + ]=10- 5.38±0.05 in aqueous 50% dioxane solution at 25°, μ=0.1 (NaClO 4 ). At pH 6–11, the red palladium(II)-PAR chelates react with tetradecyldimethylbenzylammonium chloride to form an ion-association complex which is easily extracted into chloroform and has maximal absorbance at 540 nm with a molar absorptivity of 3.29·10 4 .

Intermediates and carbonaceous deposits in the hydrogenolysis of ethane on a NiAi2O3 catalyst

Hydrogenolysis of ethane and hydrogenation of ethylene were performed on a fresh and carburized NiAl2O3 catalyst. It was deduced that any type of carbon deposits on NiAl2O3 could retard the hydrogenolysis of C2H6 provided they were stable under the reaction conditions, while such carbonaceous deposits did not retard the hydrogenation of C2H4. The action of the carbon deposits was quite analogous to that of inert components such as Cu in the CuNi alloy in the two reactions. The results suggested that the rate determining step might be the CC bond cleavage of highly dehydrogenated precursor species which subsequently yielded highly reactive CH2 species with H2.

Surface acidity of solid acids. Ultraviolet spectroscopic investigation of adsorbed pyridine

The ultraviolet spectra of adsorbed pyridine has been studied on several acidic solids (SiO2, η-Al2O3, NaX). The adsorbed pyridine had the π-π∗ band slightly shifted to longer wavelength from that of pyridine vapor. The bands of protonated pyridine and those of hydrogen bonded pyridine showed characteristic vibrational structure with a peak maximum at 256 nm. Pyridine coordinated on η-alumina gave a broad band at 258 nm. In the case of NaX zeolite, three kinds of adsorbed species were found. The adsorbed states are discussed.

Ion exchange scheme for silver exchange for sodium in the synthetic zeolite Linde 4A

Abstract For the Ag+ ion-exchanged form of the synthetic zeolite Linde 4A a logical correlation has been found between the X-ray diffraction patterns and the sorptive property; this implies that the Ag+ ion probably has a site selectivity different from that known for the K+ ion.

Spectrophotometric Studies on the equilibria of vanadium(V)-4-(2-Pyridylazo)-resorcinol-polyaminopolycarboxylate systems

Abstract The complexation equilibria in the VO+2-PAR-polyaminopolycarboxylate-(EDTA and CDTA) systems were studied spectrophotometrically in order to establish the action of CDTA in the spectrophotometric determination of vanadium(V) with PAR. Analysis of absorbance-pH curve and ligand exchange equilibria yielded the following values of the constants; KVO2HR=lO17.16, KHVO2HR=10-3.95, KVO2R=1018.81, KVO2EDTA=1017.38 and KVO2CDTA=1016.59 at 20°C and ionic strength 0.1 (KCl). Based on these constants, the selective masking behavior of CDTA for the VO+2-PAR system can be quantitatively explained.

Theoretical study of the site selectivity of Ag+ ion in dehydrated zeolite A

Theoretical interpretation is given for the site selectivity of the Ag+ ion in dehydrated zeolite A. Zeolite A was divided into two structures, ionic and covalent. The cation-lattice interaction energies — electrostatic, polarization, dispersion, repulsion and charge transfer stabilization energies — were calculated for Ag+ at the four-, six-, and eight-membered oxygen ring sites in a simplified model of zeolite A structure. As a result, the site selectivity determined for Ag+ is that the Ag+ ions prefer the six-membered oxygen ring sites in (Ag, Na)-A and (Ag, Ca)-A. These results are in good agreement with those obtained experimentally. This theoretical method will have considerable use in determination and understanding of cation sites and adsorptive characteristics of zeolite A.

Theoretical study of the site selectivity of zeolitic cations. Part 5 Site selectivities of transition metal ions in fully dehydrated zeolite A

A theoretical interpretation is given for the site selectivities of Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+, and Hg2+ ions in fully dehydrated zeolite A. This zeolite was first envisioned as being either completely ionic or completely covalent in character. This cation-lattice interaction energies, consisting of electrostatic, polarization, dispersion, repulsion, crystal field, and charge transfer stabilization terms, were then calculated for cations occupying the six- and eight-membered oxygen ring sites in a simplified model of this zeolite structure. Finally, the completely ionic and completely covalent models were integrated to give realistic values for the cation-lattice interaction energies. The results of these calculations show that the first five incoming divalent cations prefer the six-membered oxygen ring sites whereas the sixth prefers an eight-membered site.