RESUMO
The arid dissociation constants of 8-quinolineselenol, 8-quinolinol and 8-quinolinethiol in water-dioxan mixtures of varying solvent composition were determined potentiometrically or spectro-photometrically. The absorption spectra of 8-quinolineselenol in the same solvents were also obtained. The acid dissociation phenomena, stability towards oxidation and the absorption spectra of the reagents are discussed in connection with the existing forms. It is verified that 8-quinolineselenol exists as a zwitterion in water-dioxan mixtures of low or high dioxan content.
RESUMO
The synthesis of 8-selenoquinoline and its sodium salt has been improved by optimization of each process. The stability of the reagents in air and nitrogen has been examined and correlated with the drying method. Both 8-selenoquinoline and its sodium salt can exist as the monohydrate. It was found that the sodium salt of 8-selenoquinoline monohydrate is best as the weighing form of the reagent and that it can be kept stable under nitrogen in a vessel containing silica gel.
RESUMO
Photosensors (PS) and membrane photosensors (MPS), which can be immersed in the test solution and facilitate the measurement of concentration, have been developed by miniaturizing an optical system consisting of a light source and a photocell. For use in acid-base or complexometric titrations a poly(vinyl chloride) membrane containing an acid-base or metallochromic indicator can be applied as a coating to the photocell. Spectrophotometric determination of copper(II), and photometric acid-base and chelatometric titrations have been performed with the PS and MPS systems.
RESUMO
The effect of acidity on the precipitation of various bivalent metal 8-selenoquinoline and 8-mercaptoquinoline complexes has been systematically studied and compared. The metal ions were Zn(2+), Cd(2+), Pb(2+), Mn2+, Ni(2+), Cu(2+) and Co(2+). Most of the metal ions, except copper(II) and cobalt(II), precipitate as a. 1:2 complex, metal :ligand. However, in hydrochloric acid solution cadmium precipitates as CdR(2).2HCl and lead as PbR(2).2HCl or PbR.Cl. Copper(II) is reduced to copper(I) and precipitates as CuR.RH at pH above 2.0 and as CuR in strongly acidic solution. Cobalt(II) does not give a precipitate of composition but appears to precipitate as a mixture of CoR(2).RH and fixed CoR(2) or as other complexes. The reasons for the formation of the various types of precipitate are considered.
RESUMO
A new thiacrown compound in which the picrylamino group is introduced as the chromogenic group, 4'-picrylaminobenzo-l,4,8,11-tetrathiacyclopentadec-13-ene (4'-PicNHBz-TTCP), has been successfully synthesized and its characteristics as an extracting and spectrophotometric reagent have been examined. This compound (HL) forms ion-pair complexes (M(+)L(-)) with univalent class b metal ions (M(+)) such as silver and copper(I). The M(+)L(-) species can be extracted into 1,2-dichloroethane and spectrophotometrically determined. Not only class a and ab metals but also bivalent class b metals such as mercury(II) and palladium(II) are not extracted at all. As silver and copper(I) ions are effectively extracted at pH above 8.0, a suitable masking agent such as tartrate is used in order to prevent the formation of hydroxides of foreign metals, if necessary.