K<Subscript>2</Subscript>SO<Subscript>4</Subscript>-K<Subscript>2</Subscript>HPO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O phase diagram in the region of heterogeneous supercritical fluids

Our experimental study of phase equilibria in the K₂SO₄-K₂HPO₄-H₂O system at temperatures up to 500°C and pressures up to 100 MPa was directed to determine the sequence of phase transformations that generate heterogeneous supercritical fluids whose existence region propagates from the K₂SO₄-K₂HPO₄-H₂O subsystem into the ternary system. We found that supercritical fluids become heterogeneous as a result of addition of K₂HPO₄ starting with l ₁-l ₂ critical phenomena in saturated solutions, with the attendant amalgamation of the stable immiscibility region that propagates from the K₂HPO₄-H₂O system and the metastable liquid-liquid phase separation that originates from the K₂SO₄-H₂O system. Our experimental results and the topological analysis of phase equilibria in the vicinity of the critical point of water gave us the full scenario of the phase behavior of the title ternary system in the region of the subcritical and supercritical parameters of state.     

Lysine-containing calcium hydroxylapatite: Synthesis and physicochemical characterization

The CaCl₂-(NH₄)₂HPO₄-NH₂(CH₂)₄NH₂CHCOOH-NH₃-H₂O system at 25°C is studied using Tananaev’s solubility (residual concentrations) method and pH measurements. Lysine-containing calcium hydroxylapatite Ca₁₀(PO₄)₆(OH)_1.9[NH₂(CH₂)₄NH₂CHCOO]_0.1 · 6H₂O is identified using chemical analysis, thermogravimetry, powder X-ray diffraction, and IR spectroscopy.     

Synthesis and physicochemical characteristics of calcium hydroxyapatite/multiwall carbon nanotubes/collagen nanocomposites

Calcium hydroxyapatite/multiwall carbon nanotubes/collagen nanocomposites were synthesized and subjected to physicochemical analysis. The system CaCl₂-(NH₄)₂HPO₄-multiwall carbon nanotubes-NH₃-H₂O-collagen was investigated at 25°C by the solubility method (Tananaev’s residual concentration method) and by pH measurements. Chemical, X-ray powder diffraction, and thermogravimetric analyses and IR spectroscopy showed that, in the system CaCl₂-(NH₄)₂HPO₄-multiwall carbon nanotubes-NH₃-H₂O-collagen under chosen synthesis conditions, nanocomposites comprising nanocrystalline calcium hydroxyapatite (NCHA), multiwall carbon nanotubes (CNT), and collagen form with the composition Ca₁₀(PO₄)₆(OH)₂ · xCNT · yH₂O · z collagen, where x = 1–5; y = 5.5–7.7, and z = 3, 5, and 10 wt %. The obtained nanocomposites are the products of the coprecipitation of CNT, collagen, and NCHA, which forms in the system by the interaction of CaCl₂ and (NH₄)₂HPO₄.     

Effect of Impurities on Thermal Decomposition Kinetics of Mineral Fertilizers Based on (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>HPO<Subscript>4</Subscript> in Self-Generated Atmosphere

The effect of impurities on the thermal decomposition kinetics of mineral fertilizers based on (NH₄)₂HPO₄ in self-generated atmosphere was studied by the methods of thermogravimetry and differential thermal analysis. Results are presented of isothermal measurements made in the temperature range 100–110°C. An analysis of the experimental data made it possible to suggest reaction models of the decomposition and to reveal a dependence of the activation energy on the degree of decomposition. A strong deviation of the temperature dependence of rate constants from the Arrhenius law was observed. Conclusions were made on the basis of the study about the influence exerted by impurities on the thermal decomposition of mineral fertilizers based on (NH₄)₂HPO₄ in the self-generated atmosphere and reasons for the deviation from the Arrhenius law.     

On precipitation effects of aluminum,lanthanum, iron (III), and thorium phosphates

Summary Typical precipitation curves of various metal phosphates have been obtained using the turbidimetric technique. The following systems have been investigated: Al(NO₃)₃-K₃PO₄, Al(NO₃)₃-KH₂PO₄, Al(NO₃)₃NaH₂PO₄, FeCl₃-K₃PO₄, FeCl₃-(NH₄)₂HPO₄, FeCl₃K₂HPO₄, FeCl₃-KH₂PO₄, FeCl₃-NaH₂PO₄, La(NO₃)₃K₃PO₄,La(NO₃)₃-K₂HPO₄,La(NO₃)₃-KH₂PO₄,La(NO₃)₃NaH₂PO₄ and Th(NO₃)₄-K₂HPO₄. Typical precipitation curves indicated concentration ranges of phosphate precipitation and of complex solubility.

---

Zusammenfassung Typische F?llungskurven verschiedener Metallphosphate, die mittels Trübungsmessungen erhalten wurden, wurden graphisch dargestellt. Die folgenden Systeme wurden untersucht: Al(NO₃)₃-K₃PO₄,Al(NO₃)₃KH₂PO₄, Al(NO₃)₃-NaH₂PO₄, FeCl₃-K₃PO₄, FeCl₃(NH₄)₂HPO₄, FeCl₃-K₂HPO₄, FeCl₃-KH₂PO₄, FeCl₃NaH₂PO₄, La(NO₃)₃-K₃PO₄, La(NO₃)₃-K₂HPO₄, La(NO₃)₃-KH₂PO₄, La(NO₃)₃-NaH₂PO₄ und Th(NO₃)₄K₂HPO₄. Typische F?llungskurven zeigten Konzentrationsgebiete, in welchen die Metallphosphate gef?llt werden, sowie Konzentrationen, die zur Komplexbildung führten.

---

---

Supported in part by the U.S. Army Research Office, Contract No. DA-ORD-10.     

Solubility in the Na2Cr2O7-(NH4)2Cr2O7-K2Cr2O7-H2O system

Solubility in the Na₂Cr₂O₇-(NH₄)₂Cr₂O₇-K₂Cr₂O₇-H₂O four-component water-salt system at 25, 50, and 75°C was studied for the first time. Phase field boundaries for individual salts and potassium and ammonium dichromate solid solutions, monovariant lines, and invariant points were determined. Experimental data were used to optimize the looped isohydric process of potassium dichromate preparation involving additional salts.     

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

Abstract

Ammonium phoaphates belong among principal compounds of rnulticomponent liquid fertilizers and thus this study has been directed toward agrochernical application. The system NH₄H₂PO₄-(NH₄) ₂H₂PO₄- (NH₄)₂H₂P₂O_7- (NH₄)₃ H₂P₃O₁₀- (NH₄) ₃PO₄-(NH₄)₄) 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 results were discussed using a computer. The procedure used makes it possible to find a smoothing equation for each branch of the solubility diagram at issue. Simultaneously, a set of coefficienta Q related to the ideality of the respective solutions was found, From practical point of view, it can be seen from the results obtained that the highest concentrations of agrochemically effective components(nitrogen and phosphorus pentaoxide) are attained in saturated solutions containing triphosphate with a nutritional value of more than 50%.     

Reactions in the M(HCOO)2-CS(NH2)2-H2O (M = Mg, Mn, Cd) systems at 25°C

Complex formation in the M(HCOO)₂-CS(NH₂)₂-H₂O (M = Mg, Mn, Cd) systems at 25°C is studied using the isothermal solubility method. In the Cd(HCOO)₂-CS(NH₂)₂-H₂O system, a congruently dissolving compound Cd(HCOO)₂ · 2CS(NH₂)₂ is found and characterized by X-ray powder diffraction and IR spectroscopy. The Mg(HCOO)₂-CS(NH₂)₂-H₂O and Mn(HCOO)₂-CS(NH₂)₂-H₂O systems are eutonics at this temperature. Data on carbamide and thiocarbamide complexes of divalent metal formates are systematized.     

Liquid Fertilizers Based on Dolomite,Nitric Acid,and Ammonia

Solubility in the system Ca(NO₃)₂-Mg(NO₃)₂-NH₄NO₃-H₂O was studied by the visual-polythermic method. The crystallization curves and the chemical composition of the solid phase were determined. The chemical composition of solutions with crystallization temperature of 0°C was calculated. A technological scheme for production of liquid fertilizers containing nitrogen, calcium, and magnesium was proposed.     

热力学模型研究KNO3-K2SO4-H2O和KNO3-KCl-H2O体系溶解度

用Pitzer-Simonson-Clegg热力学模型(PSC模型),分别拟合KCl-H2O、K2SO4-H2O、KNO3-H2O体系以及KNO3-K2SO4-H2O和KNO3-KCl-H2O体系水活度和溶解度实验数据,得到二元参数和三元离子相互作用参数,并以此计算3个二元盐水体系溶解度相图,及2个三元盐水体系在不同温度下的溶解度,结果表明计算值与实验值一致。     

Extraction of humic acids and their fractions in poly(ethylene glycol)-based aqueous biphasic systems

The possibility of extraction and fractionation of humic acid (HA) in the aqueous biphasic systems (ABS) was shown for the first time. The 10% PEG-10% (NH₄)₂SO₄-H₂O and 5% PEG-7.5% dextran (or dextran sulphate, sodium salt)-H₂O systems were used. HA originated from peat, soddy-podzolic soil and chernozem were studied. The distribution coefficients were measured for HA of different origin, size of the molecules, molecular weights (MW) of the polymers and pH of the system. The PEG-(NH₄)₂SO₄-H₂O system was found to be better for preconcentration and isolation of HA, whereas the PEG-dextran-H₂O system is preferable for HA fractionation. The extractability of HA in ABS increases with increasing the MW of HA molecules. Peat HA are extracted in ABS with higher distribution coefficients compared with chernozem and soddy-podzolic soil HA. It is consistent with higher hydrophobicity of peat HA revealed by hydrophobic interaction chromatography. ABS are promising for HA separation into fractions that differ in their hydrophobic/hydrophilic properties as well as for comparing HA of different origin by their relative hydrophobicity.     

ZrONO3)2-H3PO4-KF(HF)-H2O system at molar ratios of PO 43? /Zr = 0.5?1.6 as the basis for phase formation

The system ZrO(NO₃)₂-H₃PO₄-KF(HF)-H₂O was studied at ∼20°C along sections at molar ratios of PO₄³⁻ = 0.5, 1.0, and 1.6; KF: Zr = 1−5; and HF: Zr = 2−6. Phases in precipitates were identified by X-ray powder diffraction; IR spectroscopy; and crystal-optical, chemical, X-ray fluorescence and thermal analyses. The following crystalline phases were isolated: potassium fluorozirconates K₃ZrF₇, K₂ZrF₆, δ-KZrF₅, and KZrF₅ · H₂O; zirconium hydrophosphate Zr(HPO₄)₂ · 0.5H₂O; and potassium fluorophosphate zirconate K₃Zr₃F₃(HPO₄)₃(PO₄)₂. The following amorphous basic oxo(hydroxo)fluorohydrophosphate nitrates were isolated: K₄Zr₄O_2.5F₈(HPO₄)₂(NO₃)₃ · 6H₂O, K₂Zr₃O₃F₂(HPO₄)₂(NO₃)₂ · H₂O, and KZr₃O_1.5F₃(HPO₄)₂(NO₃)₃ · 2H₂O. Fields of solid phases were constructed, and the roles of anions and cations in the phase formation were considered.     

Structure and spectral characteristics of (NH4)2[Re2(HPO4)4 · 2H2O]

The compound (NH₄)₂[Re₂(HPO₄)₄ · 2H₂O] has been synthesized and characterized by electronic and vibrational spectroscopy. The molecular structure has been determined by X-ray diffraction (MoK _α radiation, λ = 0.71073 Å). The (NH₄)₂[Re₂(HPO₄)₄ · 2H₂O] coordination units form centrosymmetrical binuclear ordering with each metal atom being coordinated in a distorted octahedron incorporating one rhenium atom, one oxygen atom of the water molecule, and four phosphate oxygen atoms in the equatorial plane. The rhenium-rhenium bond length (2.2207 Å) corresponds to a quadruple bond between the atoms. The [Re₂(HPO₄)₄ · 2H₂O]^2- complex anions in the crystal are associated through strong hydrogen bonds formed by the phosphate O-H···O groups. The stability of dirhenium(III) tetra-μ-phosphates in aqueous solutions is considered.     

Synthesis and physicochemical study of nanocrystalline magnesium-containing calcium hydroxylapatites and chitosan

The interaction in the CaCl₂-MgCl₂-(NH₄)₂HPO₄-NH₃-H₂O and CaCl₂-MgCl₂-(NH₄)₂HPO₄-(C₆H₁₁NO₄) _n -NH₃-H₂O systems at 25°C has been investigated by the solubility (Tananaev’s residual concentration) method and by pH measurements. Magnesium-containing calcium hydroxylapatites with the general formula Mg _x Ca_{10 − x} (PO₄)₆(OH)₂ · nH₂O (x = 0.05, 0.1, 0.2, 0.3; n = 6–7.3) and magnesium- and chitosan-containing calcium hydroxylapatites with the general formula Mg _x Ca_{10 − x} (PO₄)₆(OH)₂ · y(C₆H₁₁NO₄) · nH₂O (x = 0.05, 0.1, 0.2, 0.3; y = 0.1, 0.3, 0.46; n = 6–8.3) have been isolated in the nanocrystalline state. The solids have been characterized by chemical and thermogravimetric analyses, X-ray diffraction, and IR spectroscopy.     

Synthesis and physicochemical characterization of carboxymethylcellulose-containing calcium hydroxylapatite

The CaCl₂-(NH₄)₂HPO₄-C₈H₁₁O₇Na-NH₃-H₂O system was studied at 25°C using the solubility method (Tananaev’s residual concentration method) and pH measurements. The solid phases isolated from the system were characterized using chemical analysis, X-ray powder diffraction, IR spectroscopy, and thermogravimetry. Nanocrystalline carboxymethylcellulose-containing calcium hydroxylapatites Ca₁₀(PO₄)₆(OH)₂ · xH₂O · yC₈H₁₁O₇Na with x = 6–12 and y = 0.1–0.5 were found as a result of the characterization.     

Breakdown of the Rule of “Linearity of Water Isoactivity Lines” in a System Containing Solid Solutions

Osmotic coefficients of water have been measured isopiestically for the entire region of homogeneous ternary solutions for the Rb₂SO₄- (NH₄)₂SO₄-H₂O system at 25°C. One might expect that water isoactivity lines should be straight since this system involves a continuous series of solid solutions. The related systems (K₂SO₄-Rb₂SO₄-H₂O and (K₂SO₄- (NH₄)₂ SO₄-H₂O) obey the linearity of water isoactivity lines rule. Contrary to expectations, the (Rb₂SO₄-(NH₄)₂-SO₄-H₂O appears to be the first water–salt system containing continuous solid solutions in which the mentioned rule is not obeyed.     

Hydroxyapatite-brushite mixtures: Synthesis and physicochemical characterization

Feasibility was studied whether mixtures containing up to 90 wt % type B hydroxyapatite (Ca/P ≈ 1.50) together with brushite could be synthesized by precipitation from the Ca(NO₃)₂-(NH₄)₂HPO₄-NH₄OH-H₂O system. The synthetic materials were characterized by a set of physicochemical methods. Their behavior was studied during heat treatment and dissolution in isotonic 0.9% NaCl solution.     

Potassium Iodide in Coloring of Polyvinyl Alcohol Film in Oxidizing Solution

Conversion of potassium iodide in polyvinyl alcohol film by its treatment in the (NH₄)₂S₂O₈- CuSO₄-KI-KCl-H₂SO₄-H₂O oxidizing solution, leading to coloring of the film with molecular iodine, was studied. The conversion mechanism was analyzed as influenced by each component of the oxidizing solution.     

Thermodynamics of aqueous solutions of poly ethylene glycol di-methyl ethers in the presence or absence of ammonium phosphate salts

Precise measurements of density and sound velocity at different temperatures ranging from 283.15 to 308.15 K for solutions of PEGDME250, PEGDME500 and PEGDME2000 in water and of PEGDME500 in aqueous solutions of 0.500 mol kg⁻¹ ammonium di-hydrogen phosphate ((NH₄)H₂PO₄) and di-ammonium hydrogen phosphate ((NH₄)₂HPO₄), binodal curves at temperature ranges 293.15-318.15 K for the aqueous PEGDME500 + (NH₄)₂HPO₄, PEGDME500 + (NH₄)₃PO₄, PEGDME2000 + (NH₄)H₂PO₄, PEGDME2000 + (NH₄)₂HPO₄, PEGDME2000 + (NH₄)₃PO₄ and PPG400 + (NH₄)₂HPO₄ two-phase systems, and liquid-liquid equilibrium data at temperature ranges 298.15-318.15 K for the aqueous PEGDME500 + (NH₄)₂HPO₄ and PEGDME2000 + (NH₄)₂HPO₄ two-phase systems have been taken. From the experimental density and sound velocity data, the apparent specific volume, excess specific volume, isentropic compressibility and isentropic compressibility deviation values have been determined and the effect of temperature, charge on the anion of electrolytes and molar mass of PEGDME on the volumetric and compressibility properties of the investigated polymer solutions as well as on the salting-out effect of PEGDMEs produced by ammonium phosphate salts has been studied.     

Na<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-K<Subscript>2</Subscript>MoO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O system at 25°C

Phase formation in the Na₂MoO₄-K₂MoO₄-H₂O system was studied at 25°C. Two incongruently saturating complex phases are formed in this system: Na₃K(MoO₄)₂ · 9H₂O and NaK₃(MoO₄)₂. The densities, refractive indices, and dynamic viscosities of saturated solutions of the system were determined; molar volume and ionic strength isotherms were calculated. A correlation relation was found between solubility and solution properties in the system. The indicated double salts were recovered and characterized using chemical analysis, powder X-ray diffraction, complex thermal analysis, and IR spectroscopy.