Serb. Chem. Soc. 62(8)
619-622 (1997)
UDC 547.21:581.19
JSCS-2428
Original
scientific paper
The alkanes from some plants of Micromeria genus
RADOSAV PALIC, NOVICA RISTIC*, NEBOJSA SIMIC, DUSANKA KITIC**
and RADOMIR KAPETANOVIC*
Department of Chemistry, Faculty of Science University of Niš,
Cirila i Metodia 2, YU-18000 Niš,
*Department of Chemistry, Faculty of
Science, University of Priština, YU-38000 Priština and
**Faculty of Occupational Safety and
Health, University of Niš, Carnojevica 14, YU-18000 Niš, Yugoslavia
(Received
27 January 1997)
Hydrocarbon fractions of hexane extracts of
Micromeria thymifolia (Scop.) Fritsch and Micromeria albanica
(Griseb. ex. K. Maly) Šilic were investigated. Non-branched, saturated,
aliphatic hydrocarbons (C17 to C34) were identified by GLC with triacontane and dotriacontane
being the prevailing compounds. It was also observed that the relation between
hydrocarbons with even and odd number of C-atoms was about 7:1.
Key
words: Micromeria thymifolia, Micromeria albanica, hydrocarbons.
J. Serb. Chem. Soc. 62 (8) 623-629 (1997)
UDC
664.2:678.073:66.063.72
JSCS-2429
Original
scientific paper
Preparation of thermoplastic starch
SLOBODAN JOVANOVIC, KATARINA JEREMIC, RENATA JOVANOVIC*, JASNA
DJONLAGIC and BRANKO DUNJIC
Faculty of Technology and Metallurgy, University of Belgrade,
Karnegijeva 4, P.O. Box 494 YU-11000 Belgrade,
*Vinca Institute of Nuclear Sciences,
Laboratory GAMA, P.O.Box 522, YU-11001 Belgrade, Yugoslavia
(Received
5 February, revised 29 April 1997)
Native starch and WX-starch, i.e.,
native starch enriched with amylopectin, were mixed with plasticizers and
thermomechanically treated in a twin screw mixer in order to obtain
thermoplastic starch. Ethylene glycol, propane triol (glycerine) or poly(ethy-
lene glycol) with a molar mass less than 1000 g/mol were used as plasticizers.
Transformation to thermoplastic starch was only successful when glycerine or
ethylene glycol were used as the plasticizers, the temperature of the
thermomechanical treatment being dependent on the plasticizer and starch used.
Rheological properties of the obtained thermoplastic starch were determined
using a mechanical spectrometer. As a result of these measurements, the complex
viscosity (h*), shear modulus of stored (G') and of lost energy (G'') were
obtained as a function of frequency at constant temperature. The measurements
were performed at three temperatures: 140, 170 and 210°C. The results obtained
showed that the thermoplastic starch behaved like a typical thermoplastic
polymer.
Key
words: thermoplastic starch, preparation, rheological properties.
J. Serb. Chem. Soc. 62(8) 631-634 (1997)
UDC
622.71/546.98/:546.11/66.021.3.081)
JSCS-2430
Original
scientific paper
Hydriding and dehydriding of palladium-doped charcoal
MILENKO V. SUSIC
Serbian Academy of Sciences and Arts, Belgrade, and Faculty of
Physical Chemistry, University of Belgrade, P.O.Box 137, YU-11001 Belgrade,
Yugoslavia
(Received
20 March 1997)
The hydrogen absorption capability of wood
charcoal doped with 0.0049% of palladium was examined by differential scanning
calorimetry. Hydriding and subsequent dehydriding (oxidation) indicate that the
absorbent, due to the spill-over effect, absorbs substantial quantities of
hydrogen at atmospheric pressure.
Key
words: charcoal, palladized charcoal, hydriding.
J. Serb. Chem. Soc. 62(8) 635-641 (1997)
UDC 546.65:536.421.3
JSCS-2431
Original
scientific paper
The melting temperature and atomization energy of f2-7 lanthanides from the viewpoint
of the configurational model of solids
A. M. MARICIC, V. M. MINIC, M. V. NIKOLIC, S. M. RADIC and M. M.
RISTIC
Joint Laboratory for Advanced Materials of the Serbian Academy
of Sciences and Art, Knez Mihailova 35, Belgrade, Yugoslavia
(Received
26 March 1997)
In this paper the dependence of the melting
temperature and the atomization energy on the electronic structure of
lanthanides in the series Ce --> Eu was studied. It is shown that the
configurational model of solids enables the establishment of relations which
define these dependencies.
Key
words: melting, atomization, lantanides, configurational model of solids.
J. Serb. Chem. Soc. 62(8) 643-647 (1997)
UDC 669.017.1/546.26'
27'' 28''' 72'''' 74'''''/:66.0.65
JSCS-2432
Original
scientific paper
Thermodynamics and kinetics of the crystallization process of Fe75Ni2Si8B13C2 amorphous alloys
A. M. MARICIC, M. V. ŠUŠIC and M. M. RISTIC
Joint Laboratory for Advanced Materials of the Serbian Academy
of Sciences and Arts, Knez Mihailova 35, YU-11000 Belgrade, Yugoslavia
(Received
26 March 1997)
In this paper the crystallization process
of the Fe75Ni2Si8B13C2 amorphous alloy has been investigated. The thermodynamic and kinetic
parameters of the process were determined, using the method of differential
scanning colorimetry. Measurements of the changes in the specific electric
resistivity with time under isothermal conditions indicated changes in the
electronic structure of the material.
Key
words: amorphous alloys, crystallization, differential scaning calorimetry,
electrical resistivity.
J. Serb. Chem. Soc. 62(8) 649-656 (1997)
UDC
546.42.431-549.75:541.4
JSCS-2433
Original
scientific paper
Studies of formation of strontium and barium phosphate compounds
by atomic absorption inhibition release titration
DIMITRIJE DJ. STOJANOVIC and VILIM J. VAJGAND*
Institute for the Application of Nuclear Energy (INEP) P.O.Box
46, YU-11081 Zemun and
*Faculty of Science, University of Belgrade
YU-11000 Belgrade, Yugoslavia
(Received
24 April 1996, revised 23 April 1997)
The method of atomic absorption inhibition
release titration (AAIRT) was used for the study of formation of strontium and
barium phosphate compounds. The principle of this method is the continual
titration of a solution of releasing element with a solution of the metal and a
refractory forming anion, with the simultaneous aspiration of the titrand into
an air-hydrogen flame. The clanges in the metal absorption are registered on
the recorder. In this work, magnesium was selected as the monitor metal because
of the sensitivity of its measurement. Thus, by titration of some solutions of
SrCl2 and BaCl2 with a solution of magnesium chloride and phosphoric acid,
curves having a characteristic shape are obtained. The mole ratios of
phosphate-to-alkaline earth elements (PO43-/Ae) at the successive
characteristic points on the titration curves are constant, while the
concentration of phosphate in the titrant is variable. On the basis of these
ratios, a possible mechanism for the formation of alkaline earth phosphate
compounds is presented.
Key
words: phosphate compounds, formation, strontium, barium, atomic absorption,
titration.
J. Serb. Chem. Soc. 62(8) 657-660 (1997)
UDC 546.732'
742''+547.855.1:541.4
JSCS-2434
Note
N O T E
catena-Poly[[2,2'-dipyridylamine)cobalt(II)]-µ-[1,2-benzenedicarboxylato(2-)]
-[(2,2'-dipyridylamine)nickel(II)]]
D. POLETI and LJ. KARANOVIC*
Department of General and Inorganic Chemistry, Faculty of
Technology and Metallurgy, P.O.Box 494, YU-11001 Belgrade and
*Laboratory of Crystallography, Faculty of
Mining and Geology, Djušina 7, YU-11000 Belgrade, Yugoslavia
(Received
24 February 1997)
The title compound is monoclinic, space
group P21/a, a = 1.0050(3), b = 2.3435(9), c =
0.67830(10) nm, ß = 99.50(3)°, V = 1.5756(8) nm3, Z = 2. The complex is
heteronuclear with a structure consisting of polymeric chains joined together
by van der Waals forces. The bridging ligand is the 1,2-benzenedicarboxylate
ion with each COO group chelately coordinated to the metal ions. The central ions
are in a strongly distored octahedral environment. The spectroscopic and
magnetic properties of the com- plex are described and discussed in view of its
structure.
Key
words: cobalt(II), nickel(II), heteronuclear complex, polymeric structure,
1,2-benzenedicarboxylate ion, 2,2'-dipyridylamine.
J. Serb. Chem. Soc. 62(8) 661-675 (1997)
UDC
547.74/.75:541.18.04
JSCS-2435
Original
scientific paper
Electrochemical properties of polypyrrole in nonaqueous
solutions
OLIVERA PAVLOVIC, MILAN VOJNOVIC* and NEDELJKO KRSTAJIC*
Faculty of Technology, University of Novi Sad, B. Cara Lazara 1,
YU-21000 Novi Sad,
*Faculty of Technology and Metallurgy,
University of Belgrade, Karnegijeva 4, YU-11000 Belgrade, Yugoslavia
(Received
22 October 1996)
The electrochemical properties of
polypyrrole (pPy) films of various thickness, galvanostatically deposited on a
Pt anode, have been studied in solutions of LiClO4 (1.0 M) in propylene
carbonate (PC) by employing the cyclic voltammetric technique. The experimental
results have been interpreted on the basis of the model developed for
intercalation electrodes. The pPy films were found to have reproducible
behaviour. The charge transport through the polymer internal volume of the film
is a composite process of electron hopping in conjunction with counterion,
polymer chain and solvent motion, driven by the effective electrochemical
potential. The kinetics of oxidation (doping) and reduction (undoping)
reactions in the pPy films were found to be limited by ionic flow into the
polymer phase. Active mass utilization decreases with increasing the film thickness
and with increasing potential sweep rate, meaning that the electrochemical
conversion of the whole film becomes incomplete and only a fraction of the
polymer layer takes part in the doping-undoping process. The experimental
results proved to be useful to optimise a pPy electrode when utilizing it as
the cathode active material of a rechargeable lithium battery.
Key
words: polypyrrole electrodes, non-aqueous solutions, cyclic voltammetry.
J. Serb. Chem. Soc. 62(8) 677-681 (1997)
UDC
546.23:543.432/547.867/:546.215
JSCS-2436
Original
scientific paper
A kinetic method for the determination of selenium(IV) in
ethanol solution
GORDANA A. MILOVANOVIC, MIRA M. CAKAR* and RADIVOJ B.
PETRONIJEVIC**
Faculty of Chemistry, University of Belgrade, P.O. Box 158,
YU-11001 Belgrade,
*Faculty of Pharmacy, University of
Belgrade, YU-11001 Belgrade and
**Institute for Technology of Nuclear and
Other Mineral Raw Materials, Belgrade, Yugoslavia
(Received
27 March 1997)
A kinetic method for the determination of
selenium(IV) in ethanol solution is proposed. The method is based on the action
of selenium(IV) upon the oxidation of Nile Blue A by hydrogen peroxide in the
presence of phosphate buffer (pH 10.8). The reaction rate was followed
spectrophotometrically at 637.5 nm. It was established that the action of
selenium(IV) on the indicator reaction is maximal with a 0.25% ethanol
solution. The kinetic expression for the reaction in the presence and absence
of selenium(IV) are postulated. Optimal experimental conditions for the
determination of selenium(IV) were established and selenium(IV) was determined
in concentrations from 0.95×10-2 to 12.6×10-2 ng cm-3, with a relative standard deviation of 5.2%. A lower detection
limit (1.6×10-3 ng cm-3) and higher selectivity compared to the determination in
aqueous solution are obtained. The method was applied for the determination of
selenium(IV) in mineral water.
Key
words: Selenium(IV) kinetic determination; Nile Blue A oxidation in ethanol
solution; hydrogen peroxide.
J. Serb. Chem. Soc. 62(8) 683-686 (1997)
UDC
543.,544.2:665.761:661.183.7
JSCS-2437
Original scientific
paper
Application of the C18 column chromatography mobile phase polarity parameter PmN to
thin layer chromatography
TOMISLAV J. JANJIC, GORDANA VUCKOVIC and MILENKO B. CELAP
Faculty of Chemistry, Univresity of Belgrade, P.O.Box 158,
YU-11001 Belgrade, Yugoslavia
(Received
19 February 1997)
On the basis of literature data it was
established that the earlier described Bosch and co-workers model, developed on
C18 columns, which makes possible an estimation of the retention of substances
by means of only one substance parameter (p) and one mobile phase polarity
parameter (PmN), can be applied to
planar chromatography on thin layers paraffin-oil impregnated silica gel, but
not to thin layers of paraffin-oil impregnated aluminium oxide to cellulose
layers.
Key
words: Mobile phase polarity parameter PmN, thin layer chromatography, paraffin-oil impregnated silica
gel, 3,5-dinitrobenzoic acid esters.
J. Serb. Chem. Soc. 62(8) 687-693 (1997)
UDC
547.781/.785:543.423
JSCS-2438
Original
scientific paper
Determination of midazolam in pharmaceutical dosage forms by
second-order derivative ultraviolet spectrophotometry
LIDIJA B. PFENDT, GORDANA V. POPOVIC*, VIOLETA M. STEFANOVIC and
MIRJANA B. RAJIC
Faculty of Chemistry, University of Belgrade, P.O.Box 158,
Studentski trg 16, YU-11001 Belgrade and
*Faculty of Pharmacy, University of
Belgrade, Vojvode Stepe 450, YU-11000 Belgrade, Yugoslavia
(Received
13 February 1997)
A second-order derivative ultraviolet
spectroscopic method for the determination of midazolam in the presence of
maleic acid is described. The assays were carried out in borate buffer (pH 9.2)
at a wavelength of 222 nm, which corresponds to the position of the peak of 2D spectrum of midazolam
and to the intersection point of the 2D spectrum of maleic acid with the abscissa (zero-crossing
point). These conditions were chosen as optimum on the basis of the knowledge
of acid-base equilibria of midazolam and maleic acid and of investigations of
the absorption and 2D spectra of midazolam and maleic acid and their mixtures. A
calibration graph was obtained in the range of midazolam concentrations of
0.25-2.5×10-5 mol dm-3 with a correlation coefficient of 0.99996. The method is simple
and rapid, and was successfully applied to the determination of midazolam in
the presence of maleic acid in laboratory mixtures and in commercial tablets
containing midazolam in the maleate form.
Key
words: midazolam, derivative spectrophotometry, midazolam formulation.
J. Serb. Chem. Soc.62(8) 695-701 (1997)
UDC
546.817/546.226/:546.46/546.131/:66.061
JSCS-2439
Original
scientific paper
The kinetics of lead leaching from lead(II) sulphate in aqueous
magnesium chloride solutions
DRAGAN SINADINOVIC and ZELJKO KAMBEROVIC
Department of Nonferrous Metallurgy, Faculty of Technology and
Metallurgy, University of Belgrade, Karnegijeva 4, P.O.Box 494, YU-11001
Belgrade, Yugoslavia
(Received
27 February 1997)
The kinetics of lead leaching from lead(II)
sulphate in aqueous magnesium chloride solutions was studied. The lead leaching
rates were measured using an agitated vessel at atmospheric pressure. The
effects of the MgCl2 concentration, temperature, stirrer velocity and leaching time
on the leaching rate were examined. It was established that lead leaching by
magnesium chloride solutions is a diffusion and chemically controled reaction
(mixed kinetics).
Key
words: lead(II) sulphate, magnesium chloride, leaching kinetics.
J. Serb. Chem. Soc. 62(8) 703-709 (1997)
UDC
669.15-194.2:661.655:620.18
JSCS-2440
Original scientific
paper
The dependence of the boride layer thickness and the
microstructure of the boride layer with sub-boride zone on steel composition
Z. Z. ACIMOVIC-STOJADINOV, N. M. NOVOVIC-SIMOVIC and N. P.
VIDOJEVIC
Faculty of Technology and Metallurgy, Karnegijeva 4, P.O.Box
494, YU-11001 Belgrade, Yugoslavia
(Received
3 April 1997)
The influence of the carbon content of
steel (0.15, 0.45 and 1.0%) and the present alloying elements silicon and
chromium, on the thickness and morphology of the formed Fe2B boride layer as well
as on the microstructure of the transitional zone next to the boride layer
(sub-boride layer) were investigated. Boriding was performed using for boriding
granulate in the temperature interval 850 to 1050°C for 2 to 9 h. Besides
optical microscopy and quantitative metallography, microchemical analysis was
used in the investigations. The obtained results were analyzed with special
emphasis placed on the disagreement with existing ones. Regarding certain
issues, new observations were made and are discussed.
Key
words: carbon and low-alloyed steels, boride layer thickness and morphology,
microstructure of sub-boride layer, quantitative metallography and
microchemical analysis.