Miroslav Ebert

Untersuchung von Eisen(III)-phosphiten im Hinblick auf die Wasserstoffbindungen

Iron(III) phosphites, vic. Fe2(HPO3)3·9 H2O, FeH3P2O6·3 H2O, FeH6P3O9·H2O and Fe4H33P15O45·6 H2O were studied by means of powder X-ray, thermographic, IR and UV spectroscopy methods and by measurement of magnetic susceptibility. From the results obtained, and from analogy with phosphites studied earlier, the following structural model can be proposed: in the compounds studied, every iron atom is surrounded by six oxygen atoms of the water molecules and phosphite or, polyorthophosphite anions which form a weak ligand field of approximately octahedral symmetry. In Fe2(HPO3)3·9 H2O, symmetry of the anion is decreased from the point group C3v to the Cs group. This anion is characterised by two bonding distances between phosphorus and oxygen atoms,rPO=1,46 Å andrPO2=1,50 Å, the respective force constants beingKPO=8.7 mdyn/Å andKPO2=7.1 mdyn/Å. Three types of hydrogen bonds occur in the crystal lattices of the compounds studied. The weakest bond (bond lengthr=2.86–2.88 Å, bond energyE=4.6–5.0 kcal/bond) is formed between molecules of hydrate water, its energy approaching that of the hydrogen bond in liquid water. The stronger hydrogen bond (r=2.67–2.70 Å,E=5.7 to 8.0 kcal/bond) is found between water molecules and phosphite or polyorthophosphite anions. The strongest hydrogen bond (r=2.55–2.64 Å) is formed by polyorthophosphite anions, linking hydroxyl groups to oxygen atoms bound to different phosphorus atoms.

Untersuchung von Eisen(II)phosphiten im Hinblick auf die Ausbildung von Wasserstoffbindungen

Ferrous phosphites FeHPO3·3 H2O, FeH2P2O5, FeH4P2O6·1/2 H2O and FeH10P4O12·4 H2O were studied using X-ray powder patterns, thermography, electron reflectance spectroscopy, magnetic susceptibility measurements andRaman and infrared molecular spectra. The results obtained indicate that all the phosphites studied contain an approximately octahedral coordination sphere consisting of oxygen atoms, which produces a weak crystal field around the iron atom. Phosphite FeHPO3·3 H2O contains an HPO32− anion with the symmetry decreased from point groupC3v toCs. Ferrous diphosphite FeH2P2O5 contains a non-linear P−O−P bond with a valence angle of 159°. The hydrogen bonds between the water molecule and the HPO32− anion indicate a positive hydratation of the phosphite anion. Medium-strong or strong hydrogen bonds, 258–270 pm long, correspond to mutual interactions of the anions in the crystal lattice of hydrogenphosphites. Hydrogen bonding in hydrogenphosphites causes a decrease in theDq values.

The influence of the degree of organization of saturated solutions on the shape of the solubility isotherm

Abstract Special features of solubility isotherms of salt hydrates have been observed, from which the evidence of strong organization of saturated solutions of hydrates may be deduced. Often observed low contents of the non saturating component in the eutonic solution limiting the crystallization branch of hydrated salts is put into connection with this result. The composition of the respective eutonic solutions exhibits a correlation with the hydration entropy of the ions present in the ternary saturated solution.

A Study of Ammonium Mono-, Di- and Triphosphate Heterogeneous Systems in View of their Use as Liquid Fertilizers

Abstract Ammonium phosphates belong among principal compounds of multicomponent liquid fertilizers and thus this study has been directed toward agrochemical application. For this reason, in the system of NH+ 4, H+ PO3 4, P2O4 7, P3O5- 10 - H2O, the subsystem, NH4H2PO4 - (NH4)2H2P2O7 - (NH4)3H2P3O10[sbnd](NH4)3PO4 - (NH4)4P2O7 - (NH4)5P3O10 - H2O, was studied in which the pH of saturated solutions varies from 5 to 8. The solubility was studied in the partial pseudoternary systems. The experimental temperatures were selected immediately above the corresponding cryohydratic points, from 0 to -8°C. The sum of the results obtained can be schematically represented as a set of the curves of simultaneous crystallization of two solids on the mantle of a trigonal prism which represents the salt composition of the studied system.

Calculation of the solubility curves in ternary salt systems with compound formation

Abstract A new method for the calculation of solubility curves in solubility diagrams of ternary salt systems with compound formation is described. The method is based on the assumption that every physico-chemical process (the formation of a solid phase, formation of complex species in solution) in a given system is characterized by an interaction constant value. The relative magnitudes of these constants determine the type and shape of the diagram. The derivation does not include any empirical or adjustable parameters. The work also contains an explanation for the incongruent solubility of compounds with salt character. The conclusion contains extensive comparison of experimental data with the theoretical results.