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In this paper, the ionization constants (pKa) of some nitrogen-containing organic bases (monoethanolamine, diethanolamine and triethanolamine) in water-ethanol, water-acetone and water-acetonitrile solutions at various concentrations of organic solvent in the studied systems have been determined by the potentiometric titration method. It was found that the values of pKa of monoethanolamine, diethanolamine and triethanolamine in aqueous-organic solutions naturally decreases with increasing concentration of organic solvent in the system. It was shown that their nature and the physico-chemical properties of the medium are significantly influenced by the nature and degree of change in the electron donor ability of the studied nitrogen-containing organic bases. It should be noted that for the studied nitrogen-containing organic bases (monoethanolamine, diethanolamine and triethanolamine), when passing from an aqueous medium to an organic one (ethanol or acetone or acetonitrile), the pKa values naturally decrease with an increase in the content of the organic solvent in the system. In general, in the transition from an aqueous medium to an organic one (ethanol or acetone or acetonitrile), a change in pKa can reach 1.73 units. It was established that the dependence of the values of pKa of nitrogen-containing organic bases which were determinate via potentiometric titration method on the inverse of the dielectric constant of water-ethanol and water-acetone or water-acetonitrile solutions tends to be linear, consistent with Izmailov’s theory. Thus, we can conclude that the change in the ratio of the mixed solvent components and, as a result, in general, dielectric permeability of the medium does not lead to a significant change in the solvation characteristics of the studied nitrogen-containing organic bases.

In the current study, the peculiarities of the complexation of Hafnium(IV) with 6,7-dihyroxy‑4-carboxyl‑2-phenylbenzopyrylium salts (CDC) in binary systems and in the presence of cationic surfactants (Surf) were studied. The CDC was synthesized by condensation of pyrogallol A with benzoylpyruvic acid in an acetic acid medium in the presence of perchloric acid. To obtain KDC bromide and chloride, the synthesis was carried out in the presence of bromide acid or by sparging of dry hydrogen chloride, respectively. Using classical spectrophotometric methods of molar ratios and Bent-French, it was found that at pH 2.5 in binary system one complex with stoichiometry Hf(IV): CDC1:2 was formed. Molar absorptivity coefficient was calculated for Hf(IV) complex with CDC and it was equal 3,9⸱104. It was shown that in the presence of cetylpyridinium chloride or cetyltrimetrylammonium bromide complexes with a molar ratio of Hf(IV): CDC: Surf = 1:2:2 were formed. It is noted that the complexes were formed within 10–15 minutes, and the absorbance of the solutions remains constant for at least 2 hours. It was established that the nature of the anion, which is part of the reagent, does not significantly affect the characteristics of the analytical form. It is shown that in the presence of cationic surfactants, the optimal pH of complex formation shifts to a more acidic region. In addition, the introduction of cationic surfactants leads to a batachromic shift of the absorption band by 10–15 nm and an increase in the molar absorptivity to 5.8⸱104 and 6.4⸱104 when cetylpyridinium chloride or cetyltrimetrylammonium bromide were used respectively. It is noted that the found analytical forms can be used as a basis for the development of combined spectroscopic methods for determining trace amounts of Hafnium(IV).

The basic results are given for a development of three-component HTSC SQUID-magnetometers. The sensitivity of the RF SQUID-based sensor pumped at 24 MHz was found to be 2×10−28 J/Hz (2×10−13 T/Hz1/2). The cryogenic module consists of a fiberglas cryostat 8.6 1 in volume allowing a continuous operation for 30 days. The interferometers used demonstrated stable characteristics for 1 year. With the pumping frequency of 360 MHz the SQUID was sensitive to 3×10−29 J/Hz for frequencies higher than 700 Hz.