Takao Yotsuyanagi

Spectrophotometric determination of iron(II) with 1,10-phenanthroline in the presence of large amounts of iron(III)

A study was made to establish proper conditions for the selective determination of Fe(II) by the 1,10-phenanthroline method in the presence of large amounts of Fe(III). It was shown that fe(III) is effectively masked by fluoride. The pH of the solution to be masked should be below 2.5 in order to prevent acceleration by the fluoride of aerial oxidation of Fe(II).

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 .

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.

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.

The solvent extraction of aliphatic sulfides with copper(ii) and mercury(ii) solutions

Abstract A basic study of the extraction of aliphatic sulfides with copper(II), zinc(II) or mercury (II) is described. The stoichiometry of the extraction was established from the extraction equilibrium and by Jobs method, to be : An investigation of the effect of the anionic ligand, L-, on the extraction showed that the efficiency (D) and rate (ḱ) of the extraction and the stability of the sulfide complexes of copper (II) depended remarkably on the anion used. The effectiveness decreased in the order Similar effects were not observed for mercury(II) or zinc(II). The copper(II)- bromide system is useful for extraction of aliphatic sulfides.