Seven new solid complexes have been obtained: Hg(II), Fe(II), Ca(II) and Mg(II) complexes with 2,4D and Hg(II), Fe(II) and Ca(II) complexes with 2,4DP as well as previously described Cu(II), Zn(II), Cd(II), Pb(II), Mn(II), Co(II) and Ni(II) complexes with both ligands. The composition of ML2·nH2O complexes, where n = 0–6, was established by chemical analysis methods. Their water solubility has been determined and X-ray, IR and thermal analyses have been carried out. It has been found out that the most sparingly soluble mercury, lead, copper and cadmium compounds precipitate also from a solution of a herbicide which contains 2,4-dichlorophenoxyacetic acid (2,4D) as an active substance. The analysis of powder diffraction patterns of the complexes under study shows that they are crystalline, but have different structures. Their IR spectra have been interpreted in relation to the structural data available. It has been found out that metals are coordinated by the carboxylate groups of the ligands. The IR analysis does not allow to establish precisely the mode of coordination of the metals with the carboxylate groups. The thermal decomposition of all the compounds proceeds in a similar way. In the case of the hydrated complexes first the 1–3 step dehydration process takes place. The decomposition of the anhydrous compounds is a two step process with a complicated course. Total mass losses for the mercury, lead and cadmium complexes are close to 100%, thus in the process of thermal decomposition the metals form volatile compounds.

dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) are active substances in many weed-killer agents commonly used for the protection of crops. The literature data accom- panied by our former studies showed that in weak-acid and neutral environments these compounds react with bivalent metal ions and form complexes of limited solubility in water. It was assumed that the formation of the complexes can also occur between metals present in soil and herbicides used for plant spraying, which can reduce the uptake of the metals by the above-ground parts of the plants. Our studies concerned copper, zinc and manganese determination in wheat cultured using the pot method under laboratory conditions. Cultures were treated after sprouting with either 2,4-D or MCPA. The content of copper, manganese and zinc was deter- mined in the wheat straw. In comparison with the content in plants untreated with herbicides, the respective values were lower by ~50% for Mn, 20% for Cu and 13% for Zn.

New solid complexes of a herbicide known as dicamba (3,6-dichloro-2-methoxybenzoic acid) with Pb(II), Cd(II), Cu(II) and Hg(II) of the general formula M(dicamba) 2 ·xH 2 O (M=metal, x=0-2) and Zn 2 (OH)(dicamba) 3 ·2H 2 O have been prepared and studied. The complexes have different crystal structures. The carboxylate groups in the lead, cadmium and copper complexes are bidentate, chelating, symmetrical, in Hg(dicamba) 2 ·2H 2 O - unidentate, and in the zinc salt - bidentate, bridging, symmetrical. The anhydrous compounds decompose in three stages, except for the lead salt whose decomposition proceeds in four stages. The main gaseous decomposition products are CO 2 , CH 3 OH, HCl and H 2 O. Trace amounts of compounds containing an aromatic ring were also detected. The final solid decomposition products are oxychlorides of metals and CuO.

New solid heavy metal complexes with 4-chloro-2-methylphenoxyacetic acid (MCPA) of the general formulae: Pb(MCPA)2·H2O and Cd(MCPA)2·2H2O have been prepared. Diffractometric, IR spectroscopic and thermal analyses of these complexes and the previously described Cu(MCPA)2 have been performed. The complexes have different structures, a low level of crystallinity and exhibit a tendency to form polymers. An attempt has been made to explain the mode of the ligand molecule coordination on the basis of the position of the bands of the characteristic νasym and νsym vibrations of the carboxylate group. The course of the TG, DTG and DTA curves indicates that the compounds decompose in two (the copper salt) or three stages. The decomposition of the cadmium complex is preceded by dehydration. The basic gaseous products of decomposition are H2O and CO2. HCOOH, HOCH2COOH, HCl and trace amounts of compounds containing an aromatic ring were also detected. The final solid decomposition product is a metal oxide.

The principle of the new dual wavelength beta-correction spectrophotometric method, recommended by its author, H.W. Gao in cases of high reagent blank absorbance, has been discussed. Doubts have been expressed about alpha-correction which occurs in the formulae and the method of its determination. The method has been used to examine spectrophotometric methods of determination of Mg(II) with eriochrome black T, Ca(II) with murexide, Al(III) with eriochrome cyanine R, Cu(II) and Co(III) with pyridylazoresorcinol. The purpose of the examination was to compare the results of determinations obtained by classical spectrophotometric method and beta-correction method. It has been confirmed that the application of beta-correction alone increases the sensitivity and improves the precision and the accuracy of the methods in which reagent blank absorbance is high. It has been demonstrated that it is impossible to determine the correct alpha-correction value, and the application of the correction determined according to the recommendations of the author of the method may lead to serious errors in the results.

Spectrophotometric analysis of water solutions of 1-(2-pyridylazo)-2-naphtol stabilized in the solution by means of cationic surfactants was carried out. Four quaternary ammonium salts (CTA, TTA, CDBA, zef) were used to solubilize the reagent. Molar excess of each surfactant in relation to PAN was 100, and in the case of-CTA it was changed within the range 25-125. In all analyzed solutions the concentrations of surfactants were higher than their cmc. The analyses were performed within pH range 1-13. Two successive protonation constants of the reagent and pH ranges at which the neutral form of PAN occurs in aqueous solution were determined on the basis of the analysis of the absorption spectra. A comparison with the literature data concerning water-organic solutions showed that cationic surfactants do not have serious influence on the second protonation constant, while they decrease, by two orders of magnitude, the value of the first protonation constant. As a result, dissociation of the reagent proceeds early as the solution alkalizes and the pH ranges at which the neutral form of PAN occurs are limited.

Four quaternary ammonium salts were used to solubilize metal complexes with PAN. Absorption spectra were obtained, the compositions of the solubilized complexes were determined, and pH ranges in which complexes were formed in the presence of surfactants were found. The minimum molar excess of surfactant, in relation to the metals, which ensured solubilization of the examined complexes was established. If was found out that the solubilizing power of surfactant depends primarily on the length of the hydrocarbon chain, and to a much smaller extent, on the hydrophilic group. The order of the four examined ammonium salts in the series of decreasing solubilizing power depends on whether the solubilizate is a neutral complex (CTA greater than or equal to CDBA > TTA greater than or equal to Zef) or a complex positively charged (CDBA > CTA > Zef > TTA). Conclusions were drawn about the possibilities of application of cationic surfactants in solubilization-spectrophotometric methods for determination of the metals with PAN.

The developed spectrophotometric method of determination of cobalt(III) is based on the fact that cationic surfactant - cetyltrimethylammonium bromide (CTA) solubilizes Co(III)-PAN complex which is insoluble in water. In the presence of CTA the molar ratio of cobalt to PAN is 1:2. The optimum conditions for determination of cobalt were found. The application of buffer solutions was studied. Beer's law is obeyed over the range 0.1-1.0 mug ml-1 of cobalt, epsilon = 2.17 x 10(4) 1 mol-1 cm-1 at 570 nm. The main advantages of this method are as follows: reletively high sensitivity, simple and time-saving procedure, good accuracy and precision and wide pH range for complex formation. The method was used to determine cobalt in vitamin B12.

Kinetic parameters of thermal decomposition of thiocyanatobismuthates(III) of formulae (NH4)3[Bi(SCN)6], (NH4)2M[Bi(SCN)6] (where M is Li, Na, K, Rb) and NH4Ca[Bi(SCN)6].5H2O have been determined. The thermal stabilities (expressed by initial decomposition temperature and activation energy of the first step of decomposition) of thiocyanatobismuthates(III) containing alkali metal and ammonium group are compared with those of alkali metals in the outer sphere.

Kinetic parameters of the thermal decomposition of double alkali metal thiocyanatobismuthates of general formula M2M'[Bi(SCN)6], where M' = Li, Na, K and M = K, Rb, Cs, and rM >rM', are determined. The reaction order and activation energy of three stages of the decomposition are determined, and the effect of the outer sphere cations on the thermal stability and activation energy of the first stage of decomposition is defined. The thermal stabilities of double thiocyanatobismuthates and double thiosulphatobismuthates are compared.

The present paper presents a calculation of the kinetic parameters (activation energy, order of reaction) for different stages of the decomposition of alkali metal thiosulphatobismuthates(III). Thermal stabilities and activation energies are compared for the compounds examined. The influence of the outer sphere cations is defined as referred to the thermal stability of single (M3[BiS2O3)3], where M=alkali metal ion with the exception of Li) and double (M2Na[Bi(S2O3)3], where M=K, Cs and K5Na[Bi(S2O3)3]2) thiosulphatobismuthates(III).