Hydroxide complexes of lanthanides-IV ytterbium(III) in perchlorate medium

From the precipitation borderline in the pM'-pC(H) diagram, determined experimentally under CO(2)-free conditions, the stability constants of the mononuclear species of ytterbium hydroxide have been established. The values found are log *beta(1) = -7.7, log *beta(2) = -15.5, log *beta(3) = -23.2, log *beta(4) = -37.5, log *beta(5) = -51.9, log *beta(6) = -66.2 and log *K(S0) = 18.0. The data refer to fresh precipitates, prepared at room temperature (21.5 +/- 0.2 degrees ) in sodium perchlorate medium with an ionic strength of 1. The formation of polynuclear hydroxide complexes has been considered and rejected as unlikely to occur.     

Photometric complex-formation titrations of submicromole amounts of metals in the presence of an approximately equivalent amount of indicator

The photometric titration of the metal indicator complex MI with a ligand L is discussed. A tangent procedure is adopted for the determination of the end-point. From this procedure, in combination with an assumed maximum titration error, titration conditions have been derived. A procedure is introduced which, in conjunction with the derived titration conditions, permits the selection of a suitable titration medium by means of a diagram in which log K, log alpha and log chi are plotted vs. pH. The procedure is applied to determination of lead and zinc in the presence of citric acid, the medium used for their paper-electrophoretic separation. The use of citric acid introduces some limitations; it is shown that the method developed is generally applicable.     

Photometric complex-formation titration of submicromolar amounts of zirconium

Even in strongly acidic solution Zr(IV) forms polynuclear hydroxide complexes. In these compounds tetrameric units play a dominant role. When the Zr atoms in these units are interconnected through double OH-bridges (olated bonds) quantitative formation of Zr-EDTA is possible at room temperature. When the double OH-bridges are replaced by single oxygen-atom bridges (oxolated bonds) the units are less reactive. The oxolated tetramers are still capable of reacting quantitatively with EDTA if heated to about 100 degrees ; higher oxolated polymers are not. When these higher polymers are formed during the initial adjustment of conditions for a titration, large errors will be observed. By suitable treatment of the solutions oxolation can be restricted sufficiently to permit titrations with an error of less than 1%. Semi-Xylenol Orange has been found to be a suitable indicator for direct titrations; back-titrations are performed with Bi(3+), with PAR as indicator.     

An evaluation of the stability constants of the chloro-complexes of palladium(II)

Formulae have been derived for the stepwise stability constants of the four Pd(II)-Cl complexes, for perchlorate media at 25 degrees and ionic strengths from 0.05 to 2. The agreement with the most reliable literature data is better than 0.1 log units.     

Studies on photoinduced effects in pulse-electrodeposited Ag/Hg-1212/CdSe hetero-nanostructures

Metal/superconductor/semiconductor (Ag/Hg-1212/CdSe) hetero-nanostructures have been fabricated using pulse-electrodeposition technique and are characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy (SEM) studies. The junction capacitance of Ag/Hg-1212, Hg-1212/CdSe and Ag/Hg-1212/CdSe heterojunctions is measured in dark and under laser irradiation at room temperature. The nature of the junction formed and built-in-junction potentials were determined. The increase in carrier concentration across the junction due to photo-irradiation has been observed.     

Effect of laser irradiation of C-V characteristics of electrodeposited Ag/Tl-2223/CdSe hetero-nanostructures

One of the innovative technological directions for the high-temperature superconductors has been persued by fabricating the heteroepitaxial multilayer structures such as superconductor-semiconductor heterostructures. In the present investigation, metal/superconductor/semiconductor (Ag/Tl-2223/CdSe) hetero-nanostructures have successfully been fabricated using dc electrodeposition technique and were characterized by X-ray diffraction (XRD), full-width at half-maximum (FWHM) and scanning electron microscopy (SEM) studies. The measurement of junction capacitance as a function of biasing voltage was used for the estimation of junction built-in-potential (V _D) and to study the charge distribution in a heterojunction. The Mott-Schottky plots were measured for each junction in dark and under the photo-irradiation. The effect of laser irradiation on C-V characteristics of hetero-nanostructure has been studied.     

The decomposition and subsequent analysis of RhFe for iron

Rhodium alloyed with base metals can be decomposed by dry chlorination at 1000 degrees . The reaction product sublimes and can be freed from the insoluble rhodium trichloride by filtration after the apparatus has been washed out. The condensation of the excess of chlorine in a liquid-nitrogen trap was found very effective for the prevention of sample loss during decomposition stage.     

Solubility and protonation of EDTA, DCTA and DPTA in acidic perchlorate medium

From measurements of solubility as a function of pC(H), the protonation constants of EDTA, DCTA and DTPA for the first dissociation and addition steps have been determined. The following values were found: EDTA: log k(6) = -0.10 +/- 0.05, log k(5) = 1.45 +/- 0.02, log k(4) = 1.95 +/- 0.02 and log k(3) = 2.50 +/- 0.03; DCTA: log k(5) = 1.78 +/- 0.02, log k(4) = 2.30 +/- 0.02 and log k(3) = 3.50 +/- 0.03; DTPA: log k(7) = 0.75 +/- 0.03, log k(6)= 1.22 +/- 0.02 and log k(5) = 2.08 +/- 0.02. The experiments were done in acidic perchlorate medium (I = 1.0) at room temperature (21 degrees ).     

Semi-xylenol orange and its purification by high-pressure liquid chromatography

By Mannich condensation of o-Cresol Red, iminodiacetic acid and formaldehyde, Semi-Xylenol Orange (SXO) has been prepared in a 10-hr batch-procedure with a yield of about 30%. From the crude product SXO has been isolated by reversed-phase HPLC with perchloric acid-acetone mixtures as the mobile phase and C(18)-bonded silica as the stationary phase. The SXO fraction was freed from accompanying perchloric acid by a second separation on the same column, with water as eluent. After elution with acetone, the SXO was crystallized by evaporation.     

The stability constants of PdeDTA and its chloride complexes

From the position of the equilibrium Th + PdEDTA <--> Pd + ThEDTA, the stability constant of PdEDTA can be related to that for ThEDTA. If log k(ThEDTA) = 25.3 is taken as the most reliable value currently available, log k(pdEDTA) = 25.6 +/- 0.2 is found (NaClO(4) medium, 21 +/- 1 degrees ). Repetition of the experiments at different chloride concentrations gives an estimated log K = 5.3 +/- 0.1 for the equilibrium PdEDTA+Cl(-) <--> PdEDTACl(-). The stability constants of ThEDTA and PdEDTA are not very dependent on ionic strength in the range 0.1-1.0.