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Volume 19, Issue 3  (2010)

Education: Theory & Practice:
A. Tafrova-Grigorova
Bulgarian School Chemical Education: The State of the Art, What Then? (Results from International and National Studies)

Full text: PDF (376 K)

163
Curriculum Matters:
R. Tomova, K. Tzatchev, L. Boyanova
Biolements: Functions, Deficiency, and Food Sources

Full text: PDF (307 K)

189
Teaching Efficiency:
M. Zamfirov, T. Popov, S. Saeva
Science Teaching for Special Needs Students

Full text: PDF (309 K)

214
Teaching Chemical Experiment:
V.M. Petrusevski, M. Bukleski, M. Stojanovska
Reaction of Aluminium with Diluted Nitric Acid Containing Dissolved Sodium Chloride: On the Nature of the Gaseous Products

Full text: PDF (113 K)

233
Archives:
B.V. Toshev
Can You Solve These Problems (1893)?

Full text: PDF (90 K)

239
Chemistry & History of Chemistry: An Online Supplement:
Z. Kostova, E. Vladimirova
Development of Environmental Literacy by Interactive Didactic Strategies

Full text: PDF (163 K)

E50
Man Singh, R.K. Kale
Comparative Study of Surface Tensions of Air-Aqueous Lauryl Alcohol and of Benzene-Water Interfaces with 1:1 Salts

Full text: PDF (63 K)

E71
A. Semnani, A.R. Firooz, H.R. Pouretedal, M.H. Keshavarz, M. Oftadeh
Complex Formation between Some Thiacrown Ethers and 1,3,5-Trithiane with Bromine in Gas Phase and Carbon Tetrachloride Solution

Full text: PDF (104 K)

E80
N. Nema, N. Singh, A. Pandey
The Supramicellar Solutions of Polymeric Surfactant (PEG 400) for the Determination of Poorly Soluble Antifungal Drug

Full text: PDF (89 K)

E93
 

Khimiya, Volume 19, Issue 3(2010)

Khimiya. 19, 163- (2010) Author(s): A. Tafrova-Grigorova:

Abstract.?he main features of international monitoring studies such as TIMSS (Trends in International Mathematics and Science Study) and PISA (Programme for International Student Assessment) are outlined in comparative way in this paper. Results of these studies along with some national studies on the students achievements in Chemistry and Environmental Protection school subject are discussed. Reports of competent educational researchers and institutions are taken also into consideration in the identification of the factors that affect the actual state of Bulgarian school science education. According to the account of these studies the quality of Bulgarian science education in school drops signally during the past years. Bulgarian students lack competences such as the ability to process and present data, to solve unknown problems, as well as metacognitive skills to think scientifically and to present a problem in scientific terms, to formulate scientific hypotheses. The necessity to improve science instruction in school is obvious, and several indispensable prerequisites to do it have been suggested. Among the major determinants of the quality of school science education are: attracting and retaining of good teachers, enforcing of the school discipline, monitoring the status of schools, external student assessment and school evaluation by uniform standards, greater school autonomy, and special observation of the low achievement schools.

Keywords: science education, international studies, external assessment, TIMSS, PISA, quality of education, student achievements

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Khimiya. 19, 189- (2010) Author(s): R. Tomova, K. Tzatchev, L. Boyanova:

Abstract.Most of the chemical elements, taught in the high-school course Chemistry and Environmental Protection, are biogeneous elements. However, there is a lack of knowledge about their biological functions, the reasons for deficiency in the human organism and its consequences, and also about the food sources of these elements. The reason for this is the lack of the topic Biogeneous elements in the educational programs, which can summarize and systematize the acquired knowledge. Pupils should receive proper information, guaranteeing them a minimum of medical culture an important element of the erudition of the modern man. In the present article questions are discussed, concerning the reasons for insufficiency of biogeneous elements and different groups of foods and drinks containing them. In order to have a good feeding culture and to be in good health, pupils need to receive knowledge about such topics. Such information is not only useful but it is capable of provoking interest in the subject.

Keywords: chemistry education, bioelements, foods rich in micronutrients

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Khimiya. 19, 214- (2010) Author(s): M. Zamfirov, T. Popov, S. Saeva:

Abstract.This article discusses the issues of teaching of science for pupils with special needs. Two teaching programmes are described in details. The efficacy of using such educational tools was proved for deaf students.

Keywords: special needs students, science for deaf students, teaching

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Khimiya. 19, 233- (2010) Author(s): V.M. Petrusevski, M. Bukleski, M. Stojanovska:

Abstract.Metallic aluminium was found not to react with either concentrated or diluted nitric acid. Providing the diluted acid contains dissolved sodium chloride and traces of copper(II) cations, a vigorous reaction occurs. The product is basically nitrous oxide (possibly containing some elemental hydrogen and nitrogen gases), and was identified by its IR spectrum.

Keywords: nitrous oxide, IR spectrum of, nitric acide, aluminium

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Khimiya. 19, E50- (2010) Author(s): Z. Kostova, E. Vladimirova:

Abstract.The purpose of this study was to find out the influence of interactive and on site teaching strategies on environmental literacy of students. Three kinds of interactive technologies were compared in the study. Some of the interactive techniques in them were similar; others differed between the experimental groups. Three main interactive technologies were compared: group work in the field and poster presentations, teem work on projects and power point presentations, demonstration and discussion on concept maps in the delivery of a lecture. The project work was the most effective and the presentation of concept maps was the least effective. Neither of them was used independently. They were accompanied by additional techniques, which enhanced their influence.

Keywords: environmental literacy, interactive teaching & learning, students ecological research, river ecosystem, environmental quality impact

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Khimiya. 19, E71- (2010) Author(s): Man Singh, R.K. Kale:

Abstract.Surface tensions (γ, mN/m) for 25 to 0.05 mmol/kg aqueous Lauryl Alcohol (LA) and interfacial tension (IFT, mN/m) of benzene and water interfaces with 1.0, 0.5 and 0.1 mol/kg KF, KCl, KBr and KI halide salts are reported. The LA decreased surface tension of water by 57% with micelle formation at 5 mmol/kg with 29 mN/m, denoted as critical micelle concentration (CMC) and critical micelle surface tension (CMST), respectively. The KCl, KBr, KF and KI increased surface tensions by 5.2%, 4.0%, 3.1% and 3.0% respectively and with 51% decrease from air-water to benzene-water interfaces. The KI, KF, KCl and KBr salts decreased IFT of air-water by 63%, 61%, 61% and 56% with stronger ion-water interaction than those of the water itself. A decrease in surface tension with benzene depicted interacting activity of π-conjugation. The 57% decrease in surface tension with LA inferred stronger adherence to, to air-water interface. High quality air was used for generating pressure gradient in Survismeter operation for surface tensions and IFT.

Keywords: Survismeter, lauryl alcohol, interface, surface tension, π-conjugation

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Khimiya. 19, E80- (2010) Author(s): A. Semnani, A.R. Firooz, H.R. Pouretedal, M.H. Keshavarz, M. Oftadeh:

Abstract.Complex formation between hexathia-18-crown-6 (HT18C6), tetrathia-12-crown-4 (TT14C4), trithia-9-crown-3 (TT9C3) and 1,3,5-trithiane (TT) as n-donors with bromine as sigma-acceptor has been followed spectrophotometrically in carbon tetrachloride solution at 25oC. In all cases, the formation of 1:1 charge transfer complexes through equilibrium pathway is confirmed. The formation constants and molar absorptivities of the resulting complexes were evaluated by fitting the absorbance-mole ratio data in MATLAB software. The obtained values indicate that the stabilities vary in the order: HT18C6 > TT9C3 > TT12C4 > TT. However the reverse trend is observed for the corresponding values. The results are interpreted based on the structural features of donors. The thermodynamic parameters (calculated by Gaussian 98) due to dipole-induced dipole interactions in gas phase indicate that the charge transfer forces do have the major contribution in the stability of molecular complexes. The conductance measurements show that the resulting complexes are totally nonionic. Solid complexes were isolated and the effect of complexation on absorption bands is discussed.

Keywords: charge transfer complexes, bromine, thiacrown ether, tetrachloride
carbon, spectrophotometry, Gaussian 98

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Khimiya. 19, E93- (2010) Author(s): N. Nema, N. Singh, A. Pandey:

Abstract.The purpose of present study is to investigate the effect of Polyethylene glycol (PEG) upon the solubility of antifungal drug Ketoconazole (KTCZ). KTCZ is water insoluble drug. For water insoluble drugs difficulties are usually encountered in selecting dissolution medium with a good discriminating power. In the present study, a dissolution medium based on solubility data is developed for KTCZ. The solubility of KTCZ in various fluids such as purified water (pH 6.4), cetyl trimethyl ammonium bromide (CTAB), sodium lauryl sulphate (SLS), Polyethylene glycol (PEG) and also in 0.1 M sulphuric acid containing SLS, CTAB, PEG (at their critical micellar concentrations (CMC) values) was determined. The solubility of KTCZ is increased by 2.51 fold in PEG + purified water system. The surprising increase in solubility of same drug by 7.29 fold is found in PEG + 0.1 M H2SO4 system. Polymeric surfactants (PEG 400) form nanoscopic core-shell structures above the critical micellar concentrations. The hydrophobic drugs while the hydrophobic part serve as reservoirs for hydrophobic drugs while the hydrophilic part serves as interface between the bulk aqueous phase and the hydrophobic domain. This unique architecture enables polymeric micelles to serve as nanoscopic depots or stabilizers for poorly water-soluble compounds. A new spectrophotometric method was also proposed for the determination of KTCZ in pure form and pharmaceutical formulation. This method is based on the redox-complexation reactions, which proceed in the ketoconazole, ammonium metavanadate and PEG system and form a red-brown colored complex with absorption maxima of V(V) at 375 nm. A linear calibration graph was obtained between 1.06 Microg/mL 21.25 Microg/mL of KTCZ. The results of analysis have been validated statistically and by recovery studies. The proposed method is simple, rapid, sensitive and economic.

Keywords: spectrophotometry, ketoconazole, formulations, validation, solubility, polymeric surfactant

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