Determinación espectrofotométrica e identificación de Cd(II) con piriliden-o-hidroxianilina

Se estudia el complejo que forma la 2-piriliden-o-hidroxianilina (R) con Cd(II) ,cuya estequiometria es 3:1 (R: Gd). Se propone un método para la determinación espectrofotométrica de Cd(II) entre 1 y 4 ppm y un procedimiento para la identificación de Cd(II) (D = 1: 1.500.000). En ambos se estudia la interferencia causada por numerosos iones.The stioichiometry of the complex originated by the 2-pyrilidene-ohydroxyaniline with the ion Cd(II) has been found 3: 1 (R: Cd). A new spectrophotometric method for the determination of ,cadmiun, between 1 and 4 ppm. as well as a qualitative procedure for testing Cd(II) (D = 1: 1.500.000) is des,cribed. In both of them the interference originated by foreing ions are investigate

Determinación espectrofotométrica de F – por decoloración del complejo Zr(IV)-2-Quinizarinsulfónico

Se propone un método para la determinación espectrofotomátrica de F- mediante la decoloración del complejo Zr(IV) 2Quinizarinsulfónico, en medio acuoso y en presencia de Alcohol pOlivinílico como estabilizador, en el intervalo de concentraciones comprendido entre O y 3,5 p. p. m., estableciéndose el error y la reproducibilidad del mismo, y estudiándose la interferencia producida por el anión S02-4.A method for the spectrophotometric determination of F- by means of the decolorizing of the Zr(IV) -2Quinizarin Sulphonic complex, in aequeous medium and in the presence of polyvinyl alcohol as a stabilizer in the concentrations range from 1 to 3,5 p. p. m., 1's proposed. At the same time the reproducibility and error o fthe method are established. The interference caused by the presence of the anion S04-2 are studied

Nonmagnetic γ″-FeN thin films epitaxially grown on Cu(001): Electronic structure and thermal stability

6 págs.; 7 figs. ; PACS number s : 73.20. r, 71.20. b, 71.15.Mb, 68.37.EfWe report on a theoretical and experimental study of the growth, electronic structure, and thermal stability of ultrathin films of nonmagnetic iron nitride. The films are grown by evaporation of Fe, in a flux of atomic N produced by a plasma source, onto a Cu(001) surface kept at 300 K and characterized by x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and x-ray diffraction. The compound formed is identified as γ″ -FeN (001) growing epitaxially on the substrate. Its electronic structure and thermal stability has been studied and compared with first-principles calculations. This nitride film transforms to magnetic γ′ -Fe4 N phase by annealing above 650 K, opening new perspectives for applications of these films in functional magnetic nanostructures. © 2008 The American Physical Society.This work was supported by the Spanish CICyT under Grants No. FIS 2007-61114, No. MAT2004-05865, No. NAN2004-08881-C02-01, and CONSOLIDER on Molecular Nanoscience, the Comunidad de Madrid under Grant No. S-0505/MAT-0194, and the EU under the PF6 “Structuring the European Research Area” program Contract No. RII3- CT-2004-506008.Peer Reviewe

Intrinsic surface band bending in Cu3 N (100) ultrathin films

8 págs.; 11 figs.; 1 tab. ; PACS number s : 68.55. a, 73.20.At, 61.10. iHighly homogeneous, ultrathin films of copper nitride (Cu3 N) have been grown on Fe(001) at room temperature using a Cu evaporator and a radio-frequency plasma source to obtain atomic nitrogen in a UHV environment. Cu3 N is a semiconductor with the valence band edge at -0.65±0.05 eV below the Fermi Level. The formation of copper nitride can be detected spectroscopically by the shape of the Cu LVV-Auger electron transition, which changes sensibly in shape and position compared to metallic Cu. Cu3 N grows epitaxially with the substrate forming flat disklike mosaic blocks, (001) oriented. Both x-ray core level photoelectron spectroscopy and ultraviolet photoelectron spectroscopy photoemission experiments have been used to study the electronic structure. A first-principles calculation has been performed and compared with the measured spectra. © 2007 The American Physical Society.C.N. acknowledges the Spanish Ministry of Science and Technology FP-2001-1310. This work had the financial support of grants from both MCyT NAN2004-08881- C02-01 and MAT2004-05865 and CM CAM 07N/0023/ 2002Peer Reviewe

Determinaciones espectrofotométrica y valoración fotométrica de Cu(II) con el ácido furfuriliminodiacético

Se determinan las estequiometrías de los complejos que forma el ácido furfuriliminodiacético con el ión CuII) , que resultan ser 1: 1 y 2: 1 (R: Cu). Se proponen nuevos métodos para la determinación conductométrica y espedrofotométrica de Cu(ID, así ,como un nuevo método para la valoración fotométrica de dicho ión. Métodos que son utilizables dentro de los intervalos 16 a 130 ppm, 4 . 10-3 a 8. 10-3 M, Y 35 Y 150 ppm., con err'Üres relativos sobre el valor medio del 0,5%, del 0,5% y del 0,7%, respectivamente.The stoichiometries of the comp.lexes 'Üriginated by the furfuryliminodiacetic acid with the ion Cu(II) have been found to be 1: 1 and 2: 1 (reagent: Cu). Three new analytical methods are proposed for conductimetric and photometric titration 'Üf Cu (ID and for spectrophotometríc determination of that ion. The methods are of applicability in the range of concentra tion 16-130 pp.m. 35-150 ppm. and 4 . 10-3 M; and the averag,e errors are 0,5%, 0,7% and 0,% respectívely

Espectros y reaccionabilidad frente a iones inorgánicos de los compuestos 2-piridilaldehido-2-quinolhidrazona, 2-piridilaldehido-2-quinolilhidracida y 6-metil-2-piridilaldehido-2-quinolilhidracida

Se obtienen dos nuevos reactivos 2-piridilaldehido-2-quinolilhidracida y 6-metil-2-piridilaldehido-2-quinolilhidracida, de los que se determina su punto de fusión, espectro i. r. y u. v. Se estudia la reaccíonabilidad de ambos, así como con la del 2-piridilaldehido-2-quinolilhidrazona

Determinación espectrofotométrica de V(V) mediante 2-piraldilaldehido-2-quinolilhidrazona

El vanadio reacciona con 2-piridilaldehido-2-quinolilhidrazona (PAQH) en medio hidroalcohólico, entre valores de pH aparentes comprendidos entre 3 y 5 (pD = 6'3) formando un complejo cuya estequiometria, determinada por métodos espectrofotométricos, es de 2: 1 (reactivo: catión); el complejo, de color rojo, es estable por lo menos durante 2 horas, presentando máxima absorción a los valores de pH comprendidos entre 4 y 5'2. Se establece un nuevo método para la determinación espectrofotométrica de V(V), con menor error dentro del intervalo comprendido entre 2 y 5 ppm. El coeficiente de extinción molar es de (10'0 ± 0'3). 103 y la constante de inestabilidad es de pK = 8'00 ± 0'04.Vanadium (V) reacts with the 2-pyridinealdehyde-2-quinolylhydrazone in hydroalcoholic mixtures at pH values between 3 and 5 (pD = 6'3), glving a complex which stoichlometry from spectrophotometric data has been establ1shed as 2: 1 (reag,ent: cation). This red coloured complex is stable 2 hours at least and its maximal absorption is shown between the pH values 4 and 5"2. The opti- caI den sities of the solutlons of that complex obey the Lambert-Beer law in the range of concentrations between 0'5 and 6 ppm. of vanadium. The molar absoptivity coefficient is (10'0 ± 0'3) . 103 and the unstability 'constant pK = 8'00 ± 0'04

Separaciones cromatográficas sobre papeles impregnados en ácido 5,5´-Metilendisalicílico

The chromatropraphic behaviour of 30 cations has been studied by using Whatman núm. 4 paper impregnated with 5,5'metylendisalycilic acid and four different developing líquids. Numerous analytical separations have been found to be possible on impregnated papers but impossible on paper without the impregnating reagent.Se estudia el comportamiento cromatográfico de 30 cationes sobre papeles Whatman núm. 4 impregnados en ácido 5,5'-metilendisalicílico en cuatro diferentes líquidos de desarrollo. Se establecen numerosas separaciones analíticas sobre papeles impregnados que no eran posibles en papeles sin impregnar

Estequiometría del complejo Carmín Boro

The nature of  the boron·carmine complex in solution is established· by three methods. These were the method of continuous variations by Job and modified by Vosburgh and Cooper, the mole ratio method proposed by Yoe and Jones, and the slope ratio method of Harvey and Manning and modified by Venkateswarlu and Raghava Rao. The results obtained by the three methods indicate that the empirical formula of  the boron complex is two atoms of boron to one molecule of the reagent

Monte Carlo determination of the phase diagram of the double-exchange model

We study the phase diagram of the double exchange model, with antiferromagnetic interactions, in a cubic lattice both at zero and finite temperature. There is a rich variety of magnetic phases, combined with regions where phase separation takes place. We identify phases, intrinsic to the cubic lattice, which are stable for realistic values of the interactions and dopings. Some of these phases break chiral symmetry, leading to unusual features