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1,3-Bis[(2-pyridyl)methyleneamino]thiourea (PMAT) and 1,3-bis[(2-pyridyl)methyleneamino]-guanidine (PMAG) have been prepared. They have been examined and characterized by infrared and ultraviolet spectroscopy. A spectrophotometric method has been used for determination of the protonation constants of the reagents. Finally, a spectrophotometric survey has been made of the reactions of various cations with PMAT and PMAG.

The synthesis and preliminary analytical assessment of di(2-pyridyl)-N,N-di[(8-quinolyl)-amino]methane is reported. It shows some potential as a reagent for iron(II).

The synthesis, characteristics, properties and reaction with metallic ions of four pyridine derivatives of 2-thiohydantoin have been studied. 5-(2-Pyridyl)methylene-2-thiohydantoin, 5-(6-methyl-2-pyridyl) methylene-2-thiohydantoin, 5-(di-2-pyridyl)methylene-2-thiohydantoin and 5-[1-(2-pyridyl)-1-methyl] methylene-2-thiohydantoin have been synthesized. The substances exhibit three pK values in aqueous solution and with Ag(I), Au(III), Cu(II), Pd(II) and Zn(II) form complexes with high molar absorptivities.

The Cu(II)-hydrazine-6-methylpicolinaldehyde system in solution is studied. The "in situ" reactions, based on the formation of a ligand by condensation of an amine and an aldehyde in the presence of the metal ion, and the consequent formation of the coloured Cu(I)-azine and Cu(l)-hydrazone complexes are reported. A new mode of homogeneous colour development, based on the exchange of groups in the ligand with the metal ion present, is also described. The results are compared with those obtained with the previously synthesized reagents.

The use of furfural thiosemicarbazone as a gravimetric reagent for palladium is described. The optimum analytical conditions for precipitation of the palladium complex and the effect of possible interferences have been investigated.

The synthesis and analytical properties of 3-hydroxypicolinaldehyde azine (3-OH-PAA), salicyladehyde azine and picolinaldehyde azine are described. 3-OH-PAA is isolated for the first time. The solubility, spectral characteristics, pK values and reactions with 36 cations were examined.

The analytical properties of picolinaldehyde thiosemicarbazone and selenosemicarbazone have been studied, in order to investigate the changes produced when the Se atom is substituted for the S atom. The ionization constants of both substances are very similar. The complexes of picolinaldehyde selenosemicarbazone with cations in aqueous solution are less stable, and the absorption spectra show bathochromic and hypochromic shifts. The introduction of the Se atom offers no advantages in the analytical application of these compounds.

Bipyridylglyoxal dithiosemicarbazone reacts with iron(II) or (III). The Fe(III) complex is yellow (lambda(max) 400 nm). Fe(II) forms a red-violet 1:2 complex at pH 2.5 (lambda(max) 550 nm) and a green-blue 1:1 complex at pH 5-10 (lambda(max) 590-610 nm). Both ferrous complexes can be oxidized to the ferric complex; this reaction is reversible. The quantitative application of the ferrous complex has been studied.