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Low temperature synthesis and thermodynamic stability of fluorpyromorphite Pb5(PO4)3F at 5-65°C

Dziura A., Kwaśniak-Kominek M., Manecki M., Bajda T.

Geology, Geophysics and Environment

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2012

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Vol. 38, no. 4

465

EN

Fluorpyromorphite Pb5(PO4)3F belongs to the pyromorphite group of minerals which are isostructural with apatites. Their structure allows for variety of substitutions in both cationic and anionie positions. The purpose of this study is low temperature synthesis, mineralogical and thermodynamic characterization of fluorpyromorphite (FPY) and determination of its solubility product based on the results obtained from the dissolution experiment. FPY was synthesized by dropwise mixing of solutions containing Pb(NO3)2, K2HPO4 and NaF at 25°C. The only product of synthesis is FPY within the detection limits of X-ray diffraction. Calculated unit cell parameters are a = 9.1 ATI A, c = 7.3216 A. Homogeneous character of the precipitate was confirmed further with the use of scanning electron microscopy. Dissolution experiments were conducted in triplicates, open to the air, at 5, 25, 45°C and 65-C and at pH = 2.0. An aliquot of about 250 mg of FPY was placed in 250 mL of 0.05 M KNO3 with the pH adjusted using 0.1 M HNO3. Periodically taken samples were analyzed for [Pb] using atomic absorption spectrometry AAS as well as for [PO4] and [F] using colorimetry. Calculations of solubility products were performed with the aid of computer program PHREEQC with modified MINTEQ thermodynamic database. The activities of ionic species were calculated from measured concentrations of elements (assuming stoichiometric dissolution) with application of extended Debye-Huckel equation.

2

Calculations of reactivity of isomeric 1,5- , 1,6- and 4,6-diazaphenanthrenes

Deska M.

Prace Naukowe. Chemia i Ochrona Środowiska / Akademia im. Jana Długosza w Częstochowie

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2008

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Vol. 12

113-123

EN

Theoretical determination of the reactivity of isomeric 1,5-, 1,6- and 4,6-diazaphenanthrenes has been made by analysis of their thermodynamic stability as well as considering Fukui reactivity indices. Calculations have been performed by semiempirical AM1 method. Obtained results are compatible with experimental data.

PL

Teoretycznie oznaczono reaktywność izomerycznych 1,5-, 1,6- i 4,6-diazafenantrenów badając ich trwałość termodynamiczną, jak również stosując indeksy reaktywności Fukui. Obliczenia wykonano półempiryczną metodą AM1. Uzyskane wyniki są zgodne z wartościami doświadczalnymi.

3

Thermodynamic properties of cobalt orthosilicate

Kopyto M., Zabdyr L. A., Fitzner K.

Archives of Metallurgy

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2001

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Vol. 46, iss. 4

447-454

EN

The thermodynamic stability of the cobalt orthosilicate Co2SiO4 was determined in the temperature range 1070-1410 K, using electrochemical cells of the type: [formula]. Then, Gibbs energy change for the reaction of formation of the cobalt orthosilicate from the cobalt oxide and two silica modifications, namely quartz and amorphous, as well as Gibbs energy of SiO2(quartz) = > SiO2(amorphus) transition was obtained. The following expressions were derived: [formula]. Taking into account the literature data, the final form of the Gibbs energy change for the reaction of Co2SiO4 formation from cobalt oxide and quartz was suggested: [formula], which will be used for further phase equilibria considerations in the Co-O-Si system.

PL

Określono stabilność termodynamiczną ortokrzemianu kobaltu Co2SiO4, w zakresie temperatur 1070-1410 K, stosując ogniwa elektrochemiczne ze stałym elektrolitem o schemacie: [wzory]. Wyznaczono zmianę energii swobodnej Gibbsa reakcji tworzenia ortokrzemianu kobaltu Co2SiO4z tlenku kobaltu i z dwutlenku krzemu w dwóch postaciach: kwarcu i amorficznej oraz energię swobodną Gibbsa przemiany SiO2(kwarc) = > SiO2(amorficzny). Otrzymano następujące zależność: [wzory]. Na podstawie analizy dokładności uzyskanych wyników i wzięciu pod uwagę danych literaturowych z badań kalorymetrycznych zaproponowano ostatecznie następującą zależność energii swobodnej tworzenia ortokrzemianu kobaltu z tlenku kobaltu i kwarcu: [wzór]. Otrzymane dane posłużą do dalszych badań równowag fazowych w układzie Co-O-Si.