JSCS Vol 66, No. 4
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J.Serb.Chem.Soc.
66(4)213–236(2001)
UDC 536.77:621.929
JSCS–2849
Review
R E V I E W
Mixing
rules for excess free energy models
BOJAN D. DJORDJEVIC, MIRJANA LJ. KIJEVCANIN, JADRANKA P. ORLOVIC* and SLOBODAN P. SERBANOVIC
Faculty of Technology and
Metallurgy, University of Belgrade, YU-11120, Karnegijeva 4 and
*”Duga” - Paints and Varnishes Industry, Viline vode 6, YU-11000
Belgrade, Yugoslavia
(Received 30 December
2000)
1. Introduction
2. Huron-Vidal mixing rule (HV)
3. MHV1, MHV2 mixing rules
4. Wong-Sandler mixing rule
5. LCVM mixing rule (WS)
6. Huron-Vidal-Orbey-Sandler mixing rule (HVOS)
7. Predictive CEOS/GE models. PSRK model
8. Twu et al. mixing rules
9. VLE calculation in polymer solutions using
EOS/GE models
10. Summary
Keywords: cubic equation of state, mixing
rule, vapour-liquid equilibria, excess molar properties, correlation,
prediction.
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J.Serb.Chem.Soc. 66(4)237–241(2001)
UDC 539.2
JSCS–2850
Original scientific paper
On molecular graphs and digraphs of annulenes and their spectra
IVAN GUTMAN and PETER J. PLATH*
Faculty of Science, University of
Kragujevac, P.O. Box 60, YU-34000 Kragujevac, Yugoslavia and
*Institute of Applied and Physical Chemistry, University of Bremen,
P.O. Box 330440, D-28334 Bremen, Germany
(Received 25 December
2000)
Amolecular graph, consisting of undirected
edges, can be represented as a sum of two digraphs, consisting of oppositely
oriented directed edges. In the case of annulenes, the eigenvalue spectrum of
the molecular graph is equal to the sum of the eigenvalue spectra of the
respective two molecular digraphs.
Keywords: molecular graph, molecular digraph,
annulene, spectrum (of graph).
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J.Serb.Chem.Soc.
66(4)243–247(2001)
UDC 547.2
JSCS–2851
Original scientific paper
Narumi-Katayama index of phenylenes
ZELJKO TOMOVIC and IVAN GUTMAN
Faculty of Science, University of Kragujevac, P.O. Box 60, YU-34000 Kragujevac, Yugoslavia
(Received 22 December
2000)
The Narumi-Katayama topological indes S of a
hydrocarbon is the product of vertex degrees of the respective molecular graph.
If PH is a phenylene and HS is its hexagonal squeeze, then the respective
Narumi-Katayama indices are related as S(PH) = 9h–1 S(HS), where h
is the number of hexagons of PH and HS, or as S(PH) = S(HS)b , where a = 0.078 and b = 1.613.
Keywords: Narumi-Katayama topological index,
phenylenes, hexagonal squeeze, benzenoid hydrocarbons.
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J.Serb.Chem.Soc.
66(4)249–258(2001)
UDC 536.5/546.46
JSCS–2852
Original scientific paper
The improvement of the detection power of a U-shaped DC plasma
MIRJANA TRIPKOVIC, IVANKA HOLCLAJTNER-ANTUNOVIC*, MOMIR MARINKOVIC** and DRAGAN MARKOVIC
Institute of Physics, P.O. Box 57,
YU-11000 Belgrade,
*Faculty of Physical Chemistry, University of Belgrade, P.O. Box
157, YU-11000 Belgrade and
**Vinca Institute of Nuclear Sciences, P.O. Box 522, YU-11001
Belgrade, Yugoslavia
(Received 8 December
2000)
Optimization of the operating parameters of
U-shpaed DC arc plasma and spectrometer parameters has been undertaken to
explore the possibilities of improving its detection power. It is demonstrated,
with a U-shaped arc as an example, that the limits of detection, in addition to
well-defined parameters as described by Boumans and Winge, depend on the signal
integration time. It is shown that with increasing integration time, the limits
of detection are decreased within some limits and that the precision and
concentration sensitivity are improved as well. A mathematical expression for
the dependence of the detection limit on the integration time is presented. To
increase the reliability of the measurement of the mentioned parameters, the
working conditions were optimized for the following analytes: Ag, Al, Au, Cr,
Fe, Mn, Ni, Pb, Pd, Pt, and V. The obtained limits of detection are comparable
or better than those obtained by ICP for the elements studied. Itwas estimed
that the possibility exists for their further improvement up to 10 times.
Keywords: optical emission spectrometry,
signal integration time, detection limits, precision, DC plasma.
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J.Serb.Chem.Soc.
66(4)259–271(2001)
UDC 543.844: :546.76
JSCS–2853
Original scientific paper
Inverse gas chromatography of chromia. Part I. Zero surface coverage
A. E. ONJIA, S. K. MILONJIC and LJ. V. RAJAKOVIC*
The Vinca Institute of Nuclear
Sciences, P.O. Box 522, YU-11001 Belgrade and
*Faculty of Technology and Metallurgy, P.O. Box 494, YU-11001
Belgrade, Yugoslavia
(Received 24 November
2000)
The surface properties of the solid obtained
from colloidal chromiawere investigated by inverse gas chromatography (IGC), at
zero surface coverage conditions. The solid samples I dried at 423 K and II
heated at 1073 K in the amorphous and crystalline form, respectively, were
studied in the temperature range 383–423 K. The dispersive components of the
surface free energies, enthalpies, entropies, and the acid/base constants for
the solidswere calculated from the IGC measurements and compared with the data
for a commercially available chromia (III). Significantly lower enthalpies and
entropies were obtained for cyclohexane on solid II and chloroform, highly
polar organic, on solid I. The dispersive contributions to the surface energy
of solid II and III were similar, but much greater in the case of solid I. All
the sorbents had a basic character, with the KD/KAA ratio decreasing in the order I > II >
III. The retention and resolution in the separation of a vapour mixture of C5–C8n-alkanes on the three substrates were different.Arapid
separationwas observed on solid II and an enhanced retention on solid I.
Generally, the heated chromia (II) exhibited diminished adsorption capacity,
and enhanced homogeneity of the surface.
Keywords: inverse gas chromatography,
chromia, adsorption, thermodynamics.
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J.Serb.Chem.Soc. 66(4)273–280(2001)
UDC 661.86: :541.124
JSCS–2854
Original scientific paper
The kinetics of the partial dehydration of gibbsite to activated alumina in a reactor for pneumatic transport
LJILJANA ROZIC, TATJANA NOVAKOVIC, NADEZDA JOVANOVIC, ANA TERLECKI-BARICEVIC and ZELJKO GRBAVCiC*
ICTM - Department of Catalysis and
Chemical Engineering, P.O. Box 815, Njegoseva 12, Belgrade and
*Faculty of Technology and Metallurgy, University of Belgrade,
Karnegijeva 4, Belgrade, Yugoslavia
(Received 11 July 2000,
revised 12 January 2001)
The dehidration kinetics of gibbsite to
activated alumina was investigated at four different temperatures between 883 K
and 943 K in a reactor for pneumatic transport in the dilute two phase flow
regime. The first order kinetic behavior of this reactionwith respect to the
water content of the solid material was proved and an activation energy of 66.5
kJ/mol was calculated. The effect of residence time on the water content is
given and compared with theoretical calculations. The water content and other
characteristics of the products depend on two main parameters, one is the short
residence time and the other is the temperature of the dehydration of gibbsite.
The short residence time of the gibbsite particles in a reactor for pneumatic
transport prevents crystallization into new phases, as established from XRD
analysis data. Reactive amorphous alumina powder, with a specific surface area
of 250 m2/g, suitable as a precursor for catalyst
supports is obtained.
Keywords: gibbsite, dehydration kinetics,
pneumatic transport, activation energy.
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J.Serb.Chem.Soc.
66(4)281–287(2001)
UDC 661.993:66.094.54659
JSCS–2855
Original scientific paper
Carbon monoxide oxidation on a Au(111) surface modified by spontaneously deposited Ru
SVETLANA STRBAC, OLAF M. MAGNUSSEN* and ROLF-JÜRGEN BEHM*
ICTM - Institute of
Electrochemistry, P.O. Box 815, YU-11001 Belgrade, Yugoslavia and
*Abteilung für Oberflächenchemie und Katalyze, Univerzität Ulm,
D-89069 Ulm, Germany
(Received 25 December
2000)
The spontaneous deposition of Ru on Au(111) was
performed in 10-3 M RuCl3 + 0.5 M H2SO4 solution. The obtained surface was
characterized by STM under potential control in 0.5 M H2SO4 solution. The coverage of the Au(111) terraces
by deposited Ru was estimated by STM to be 0.02 ML. Step decoration could be
noticed in the STM images, which indicates that the steps, as lined defects,
are active sites for the nucleation of Ru monolayer islands, while the random
distribution of Ru nuclei, observed on the terraces indicates point defects as
active sites. The electrocatalytic activity of Au(111) surface modified by
spontaneously deposited Ru was studied towards CO oxidation. The significant
enhancement in the reaction rate compared to CO oxidation on a pure Au(111)
surface, indicated that the edges of the deposited Ru islands were the active
sites for the reaction.
Keywords: spontaneous deposition, Ru, Au(111),
CO oxidation, STM.
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Copyright & copy; SHD 2001.
Last
Updated May 29, 2001.
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