Обучение по природни науки и върхови технологии

2019/4, стр. 475 - 484

CONSTRUCTION OF JOB’S PLOT IN CASE OF HIGH SPECTRAL OVERLAP BETWEEN THEREACTANTSANDTHECOMPLEX:APPLICATION OF MULTIWAVELENGTH LINEAR REGRESSION ANALYSIS USING THE CU-EDTA SYSTEM

Agha Arslan Wasim
E-mail: arslan.wasim@uok.edu.pk
Department of Chemistry
University of Karachi
75270 Karachi Pakistan
Muhammad Nasiruddin Khan
E-mail: nasiruk@uok.edu.pk
Department of Chemistry
University of Karachi
75270 Karachi Pakistan
Muhammad Farooq Wahab
E-mail: farooq.w@gmail.com
Department of Chemistry and Biochemistry
University of Texas at Arlington
Arlington TX USA
Saba Fazal-ur-Rehman
E-mail: saba@uok.edu.pk
Department of Chemistry
University of Karachi
75270 Karachi Pakistan

Резюме: Job’s method is extensively used to determine the stoichiometry of complex ions both in the field of education and research. However, the shape of the Job’s plot generally does not match to what is shown in the textbooks due to simultaneous absorption by other species involved in the equilibria. The conventional correction method deals the problem by assuming that no reaction would have occurred among the reactants and thus uses their formal concentrations for the correction of empirical data. The assumption is contradictory as, in solution equilibria, formal concentrations differ substantially from the respective equilibrium concentrations. Alternatively, multiwavelength linear regression analysis is used to determine the equilibrium concentrations of reactants in the system. The two correction methods, when applied on Cu-EDTA system, showed a significant difference between them. The comparative study is designed to evaluate the correction methods. Moreover, Microsoft Excel \({ }^{\text {® }}\) was incorporated to transform tedious correction into quick and interesting processing of data.

Ключови думи: job plot; continuous variation; absorbance correction; stoichiometry

Introduction

The importance of complexation equilibria in chemical education and research cannot be overemphasized. The experimental determination of complex ion stoichiometry by UV-Vis spectrophotometry is a popular experiment in chemistry throughout the world. The method of continuous variation, the Job’s method, has been extensively used in the determination of complex ions stoichiometry. A diverse range of systems have been studied by using this method. Most common systems are the inorganic complexes (Carmody, 1964; Hill & MacCarthy, 1986) dyes-surfactant associates (Karukstis et al., 1998), and the protein-protein complexes (Ingham, 1975). Besides determining stoichiometry, this method has also been used to study the mechanism of chelation process (Huang et al., 2003). Most of the experiments related to Job’s plot are used to determine the stoichiometry of the complex ions. For the study of a general complexation reaction between a metal (M) and a ligand (L)

\[ m M+n L \rightleftharpoons M_{m} L_{n} \]

A series of solutions is prepared using equimolar solution of M and L such that the sum of formal concentrations of M and L is kept constant whereas the L to M ratio is varied systematically within the series. In principle, any physical property which is directly related to complex ion concentration can be used to construct the Job’s plot (Gil & Oliveria, 1990). The most commonly used technique is UV-Vis spectrophotometry of the complex ion using the Beer’s law. The plot of absorbance against the volume fraction of M or L results in a Job’s plot. It may either possess maxima or minima at a volume fraction which is used to determine the stoichiometry of complex ion.

A problem arises in the construction of the Job’s plot when reactants absorbs at the selected wavelength which is normally the wavelength for complex. The nice inverted V shape is disturbed which might also affect the obtained results. There are methods reported for the correction of such spectral interference, but they deal the problem using formal concentrations of the reactants to estimate their absorbance contribution and correction. This contradicts the concept of solution equilibria. A better approach would be to use the equilibrium concentrations of species for the absorbance corrections. In this study Cu-EDTA complexation equilibria was selected to illustrate the concept of absorbance correction using equilibrium concentrations rather than their formal concentrations. This system showed significant spectral overlap, the unbound copper ion \(\left(\mathrm{Cu}^{2+}\right)\) absorbs at essentially all the wavelengths that can be used to study the complex, i.e., there is a significant spectral overlap between \(\mathrm{Cu}^{2+}\) and Cu-EDTA as shown in Fig. 1. The unbound ethylenediaminetetraacetic acid does not absorb light at the wavelengths selected for the analysis. The difference between the conventional and the proposed method of absorbance correction was elaborated when both methods were processed on the experimental data obtained for this system. The comparison revealed that there is a significant difference between the two correction methods. Moreover, the propagation of error to the conditional formation constant emphasized the use of equilibrium concentrations for the correction of measured absorbance.

Figure 1. Visible spectra of \(\mathrm{Cu}^{2+}\) ion (0.02 M ) and Cu-EDTA Complex (0.01 M) showing significant spectral overlap for the two species

Materials and methods

Equipment

Shimadzu 1601 UV-Vis spectrophotometer was used to measure the absorbance values of the series of solution in glass cells, 1cm pathlength. The data acquisition was carried out using the software UVPC39 installed in the computer interfaced with the spectrophotometer. The data was copied to MS excel spread sheet for further calculations. pH of the solution was measured using Hanna instruments pH 211 equipped with a combined glass electrode.

Chemicals

All chemicals used in this experiment were general laboratory grade reagents, mostly available in an undergraduate laboratory. Copper (II) sulfate-pentahydrate (Avonchem), disodium salt of ethylenediaminetetra-acetic acid (\(\mathrm{Na}_{2}\) EDTA. Dihydrate) (Avonchem), sodium Acetate (BDH), Acetic acid (Avonchem), HCl (Fluka) and \(\mathrm{KCl}(\mathrm{BDH})\) and distilled water were used to prepare the series.

Experimental procedure

0.1 M stock solutions of \(\mathrm{Cu}^{2+}\) and \(\mathrm{Na}_{2}\) EDTA were prepared using the respective salts and distilled water, no acid or base was added at the stage of stock preparation. The stock solutions were standardized using reported methods (Christian, 2004; Mendham, 2000). A series of eleven solutions was prepared in which Cu to EDTA stock volume ratio \(\left(\mathrm{V}_{\mathrm{Cu}}: \mathrm{V}_{\text {EDTA }}\right)\) varied from 0:10 to 10:0. The sum of the stock volumes was fixed to 10.0 mL and the final volume of each solution was made up to 50.0 ml in a volumetric flask using pH 4.7 buffer. The standard solution of Cu-EDTA complex \((0.01 \mathrm{M})\) was prepared by using the stock solutions of \(\mathrm{Cu}^{2+}\) and EDTA. The concentration of \(\mathrm{Cu}^{2+}\) ions was 0.01 M and concentration of EDTA was nine times the \(\mathrm{Cu}^{2+}\) concentration, whereas, the pH was maintained at 4.7 using respective buffer solution. pH 4.7 buffer was prepared by dissolving equal volumes of 0.2 M acetic acid and 0.2 M sodium acetate solution and the pH was finally adjusted to the labeled value by using the HCl or sodium hydroxide solution. Each solution was scanned in a UV/Vis spectrophotometer from 500 and 1000 nm. The wavelength interval for scanning was 5nm and the respective buffer was used as blank.

Result and discussion

It is generally considered that the unbound reactants present in the series do not absorb at the selected wavelength. Unfortunately, the nice \(\Lambda\) shape is generally not seen for the Job’s plot when there are multiple absorbing species involved in the equilibria. In case of spectral overlap of reactants and the complex, the measured absorbance would be the accumulated absorbance of all species present in the system. Such a plot can still be used for determining the stoichiometry; however, the students can be left wondering as to why their plot does not match the idealized shapes in the textbook. In this case concept of absorbance correction by a blank becomes ambiguous because we do not know the exact concentration of absorbing species besides the complex. Thus, the absorbance of unbound reactants must be dealt in another way. We observed same behavior when we incorporated Job’s plot experiment using copper EDTA in our analytical chemistry laboratory course. This led us to think about the concept of correcting absorbance in case of severe spectral overlap of components in the mixture.

The general texts discussing this method use the following equation for the correction of absorbance (Harris, 1999; Hill & MacCarthy, 1986; Hogfeldt, 1979):

(1) \[ A_{\text {corr }}=A_{\text {meas }}-\left(\epsilon_{M} C_{M}+\epsilon_{L} C_{L}\right) b \]

where, \(A_{\text {corr }}\) is the corrected absorbance used to construct the jobs plot, \(A_{\text {meas }}\) is the measured absorbance. The respective molar absorptivity of metal and ligand, at the \(\lambda_{\text {max }}\) of complex are represented by \(\epsilon_{M}\) and \(\epsilon_{L}\), respectively. The pathlength of the cell is b, whereas, \(C_{M}\) and \(C_{L}\) are the formal concentrations of the metal and ligand in a solution of the series respectively. The correction method assumes that no reaction would have occurred between the reactants (Gil & Oliveria, 1990; Hill & MacCarthy, 1986); therefore, the formal concentrations of reactants can be used in Eq. (1). This assumption is highly oversimplified. It ignores the formation of complex which can result in a significant difference between the equilibrium concentrations of the unbound reactants and their respective formal concentrations. Therefore, one can easily interpret that this assumption would result in underestimation of the corrected absorbance for complex ion. Moreover, the use of such corrected absorbance to evaluate conditional formation constant will lead to the propagation of error in the resulting values. We have designed an experiment that helps the students to understand the concepts of simultaneous analysis, multiwavelength linear regression and a relatively better way to correct background absorbance where simple blank corrections are inadequate.

Instead of using formal concentrations, this study suggests a correction method which relies on determining the equilibrium concentrations of unbound reactants which are then used in Eq. (1) to determine the corrected absorbance. The equilibrium concentrations are determined using Multiwavelength Linear Regression Analysis, a reported method, for the simultaneous analysis of a mixture using spectrophotometry (Blanco et al., 1989). This method is based on Eq. (2):

(2) \[ \tfrac{A_{m i x}}{A_{M s t d}}=\tfrac{C_{1}}{C_{M s t d}}+\left(\tfrac{A_{M L s t d}}{A_{M s t d}}\right) \tfrac{C_{2}}{C_{M L s t d}} \]

where, \(A_{\text {mix }} A_{\text {mix }}\) is the absorbance of the solution containing a mixture of complex ion and the unbound reactant. \(A_{M s t d}\) and \(C_{M s t d}\) are the absorbance and concentration of standard solution of the interfering reactant, respectively. \(A_{M L \text { std }}\) and \(C_{M L s t d}\) are the respective absorbance and concentration of standard solution of complex ion. \(C_{1}\) and \(C_{2}\) are the equilibrium concentrations of unbound interfering reactant and complex ion in the mixture respectively.

The absorbance of each solution of a series prepared to construct Job’s method is scanned for a range of wavelengths. The standard solution of complex ion and unbound reactant are also scanned for the same wavelengths. The resulting data is then used to construct \(\tfrac{A_{\text {mix }}}{A_{M \text { std }}}\) vs. \(\tfrac{A_{M L \text { std }}}{A_{M \text { std }}}\) plot which should be a linear curve for each solution.

Table 1. Selected data of Absorbance ratio for the series and standard solutions. Volume fraction of \(\mathrm{Cu}^{2+}\) increases from 0 to 1 from solution 1 to XI respectively

λ(nm) 1*Absorbance Ratio2IIIIIIIVVVIVIIVIIIIXXXI10001.12180.00450.23300.45230.66790.92591.16571.24811.25641.18081.12711.00009701.06900.00790.22160.41750.63250.85341.06511.16041.13811.09531.04871.00008701.49270.00500.32900.61360.88611.13601.35111.41361.34861.24281.15011.00007702.67350.00500.63301.15101.59201.92452.23702.24501.98101.71501.40651.00007303.53130.00630.84591.51172.07522.55022.86612.82942.47132.03731.60141.00006705.86420.01371.42662.53913.53094.21954.83954.68593.88483.06042.13171.000057011.90160.18033.00005.18037.31158.67219.60669.55747.77055.95083.80331.0000

* Absorbance ratios for Cu-EDTA complex and \(\mathrm{Cu}^{2+}\) standard solutions at various wavelengths

** Absorbance ratios of a mixture and \(\mathrm{Cu}^{2+}\) standard solution at various wavelengths

The absorbance ratio plots for the series are shown in Fig. 2. The slope and intercept of each curve were determined which were then used to determine the concentrations \(C_{1}\) and \(C_{2}\) for each solution. The correlation coefficients for the dependent \(\left(\tfrac{A_{\text {mix }}}{A_{M s t d}}\right)\) and independent \(\left(\tfrac{A_{M L s t d}}{A_{M s t d}}\right)\) variables were determined using CORREL formula. The values were ranging from 0.9989 to 0.9997. The best values of correlation coefficients were found when the data from \(560-1000 \mathrm{~nm}\) was used for the calculations. Most of the calculations were performed using Microsoft excel. The slope and intercept from the absorbance ratio data was calculated using LINEST formula and the graphs were also plotted using the spreadsheets as shown in Fig. 4.

The molar absorptivity of \(\mathrm{Cu}^{2+}\left(\epsilon_{\mathrm{Cu}^{2+}}\right)\) was determined using the concentration and absorbance of the standard solution for \(\mathrm{Cu}^{2+}\) ions at the \(\lambda_{\text {max }}\) of complex (730 \(\mathrm{nm})\). Table 1 summarizes the experimental data. The absorbance contribution by the unbound \(\mathrm{Cu}^{2+}\) ion was corrected using Eq. (3); the modified form of Eq. (1).

Figure 2. Plots of absorbance ratio for the series. From I to \(\mathrm{XI}, \mathrm{V}_{\mathrm{Cu}}: \mathrm{V}_{\text {EDTA }}\) changes from 0:10to 10:0 respectively

Figure 3. Jobs plot of Cu-EDTA system for the measured absorbance, the MLRA absorbance correction and conventional absorbance correction

(3) \[ A_{\text {corr }}^{\prime}=A_{m}-\epsilon_{\mathrm{Cu}^{2}+b} C_{1} \]

The corrected absorbance from Eq. (3) was then used to construct the Job’ For comparison both correction methods were applied on the same data set and the absorbance data obtained from the two correction methods are shown in Table 2. The conventional correction method was studied at the \(\lambda_{\text {max }}\) of the complex.

Figure 4. Screen shot of spreadsheet used to perform the required calculations

Table 2. Comparison of absorbance values determined using the correction methods

Formal Conc. (M) Volume fractionCu2+*%ΔAcorr000.0010.00100.0020.10.118070.1339-11.80.0040.20.207640.2393-13.20.0060.30.281010.3285-14.40.0080.40.340380.3943-13.70.010.50.374550.4282-12.50.0120.60.352920.4069-13.3
0.0140.70.280390.3234-13.30.0160.80.195860.2287-14.40.0180.90.111030.1308-15.10.021.0000

The Job’s plots from the uncorrected data, the conventionally corrected and alternate methods are shown in Fig. 3. The corrected absorbance at the two extremes of the series were found quite similar for the two correction methods, but the difference was significant, ranging from 10 to \(15 \%\), for the rest of the series. An important educational aspect of method of continuous variation is the determination of equilibrium constant for the system under study. The equilibrium calculations rely on the absorbance values obtained from the plot. If the absorbance corrections are based on formal concentrations it would propagate huge error, shown in Table 2, and the analysis would yield erroneous values of equilibrium constant.

Conclusion

Pedagogically this article is intended to solve a problem related to solution equilibria by integrating multiple concepts used in undergraduate chemistry education. Moreover, the application of Multiwavelength-Linear-Regression-Analysis for the absorbance correction of Job’s method came out as an alternate correction method which is reliable as compared to the conventional methods. This experiment practically shows the difference between formal and equilibrium concentrations and can also serve as an example to elaborate the concept in chemistry laboratory.

REFERENCES

Blanco, M., Iturriaga, H., Maspoch, S. & Tarin, P. (1989). A simple method for spectrophotometric determination of two-cmponents with overlapped spectra. J. Chem. Educ., 66, 178 – 180.

Carmody, W.R. (1964). Demonstrating Job’s method with colorimeter or spectrophotometer. J. Chem. Educ., 41, 615 – 616.

Christian, G.D. (2004). Analytical chemistry. Kundli: Wiley.

Gil, V.M.S. & Oliveria, N.C. (1990). On the use of the method of continuous variations. J. Chem. Educ., 67(6), 473 – 478.

Harris, D.C. (1999). Quantitative chemical analysis. New York: Freeman.

Hill, Z.D. & MacCarthy, P. (1986). Novel approach to Job’s method: an undergraduate experiment. J. Chem. Educ., 63, 162 – 167.

Hogfeldt, E. (1979). Graphic and computational methods in the evaluation of stability constants (pp. 100-102). In: Khlthoff, I.M. & Elving, P. J. (Eds.). Treatise on analytical chemistry. New York: John Wiley & Sons.

Huang, C.Y., Zhou, R., Yang, D.C.H. & Chock, P.B. (2003). Application of the continuous variation method to cooperative interactions: mechanism of Fe(II)–ferrozine chelation and conditions leading to anomalous binding ratios. Biophys. Chem., 100, 143 – 149.

Ingham, K.C. (1975). On the application of Job’s method of continuous variation to the stoichiometry of protein-ligand complexes. Anal. Biochem., 68, 660 – 663.

Karukstis, K.K., Savin, D.A., Loftus, C.T. & D’Angelo, N.D. (1998). Spectroscopic studies of the interaction of methyl orange with cationic alkyltrimethylammonium bromide surfactants. J. Colloid Interface Sci., 203, 157 – 163.

Mendham, J. (2000). Vogel’s textbook of quantitative chemical analysis: London: Pearson Education.

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Берна Сабит, Джемиле Дервиш, Мая Никова, Йорданка Енева

IN VITRO EVALUATION OF THE ANTIOXIDANT PROPERTIES OF OLIVE LEAF EXTRACTS – CAPSULES VERSUS POWDER

Hugo Saint-James, Gergana Bekova, Zhanina Guberkova, Nadya Hristova-Avakumova, Liliya Atanasova, Svobodan Alexandrov, Trayko Traykov, Vera Hadjimitova

2019 − THE INTERNATIONAL YEAR OF THE PERIODIC TABLE OF CHEMICAL ELEMENTS

Maria Atanassova, Radoslav Angelov, Dessislava Gerginova, Alexander Zahariev

ТЕХНОЛОГИЯ

Б. В. Тошев

Книжка 5
ЗЕЛЕНА ХИМИЯ В УЧИЛИЩНАТА ЛАБОРАТОРИЯ

Александрия Генджова, Мая Тавлинова-Кирилова, Александра Камушева

ON THE GENETIC TIES BETWEEN EUROPEAN NATIONS

Jordan Tabov, Nevena Sabeva-Koleva, Georgi Gachev

CAN BRING PEOPLE TOGETHER

Nadya Kantareva-Baruh

Книжка 4
CHEMOMETRIC ANALYSIS OF SCHOOL LIFE IN VARNA

Radka Tomova, Petinka Galcheva, Ivajlo Trajkov, Antoaneta Hineva, Stela Grigorova, Rumyana Slavova, 6Miglena Slavova

ЦИКЛИТЕ НА КРЕБС

Ивелин Кулев

Книжка 3
ПРИНЦИПИТЕ НА КАРИЕРНОТО РАЗВИТИЕ НА МЛАДИЯ УЧЕН

И. Панчева, М. Недялкова, С. Кирилова, П. Петков, В. Симеонов

UTILISATION OF THE STATIC EVANS METHOD TO MEASURE MAGNETIC SUSCEPTIBILITIES OF TRANSITION METAL ACETYLACETONATE COMPLEXES AS PART OF AN UNDERGRADUATE INORGANIC LABORATORY CLASS

Anton Dobzhenetskiy, Callum A. Gater, Alexander T. M. Wilcock, Stuart K. Langley, Rachel M. Brignall, David C. Williamson, Ryan E. Mewis

A TALE OF SEVEN SCIENTISTS

Savina Kirilova

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DEVELOPMENT OF A LESSON PLAN ON THE TEACHING OF MODULE “WATER CONDUCTIVITY”

A. Thysiadou, S. Christoforidis, P. Giannakoudakis

AMPEROMETRIC NITRIC OXIDE SENSOR BASED ON MWCNT CHROMIUM(III) OXIDE NANOCOMPOSITE

Arsim Maloku, Epir Qeriqi, Liridon S. Berisha, Ilir Mazreku, Tahir Arbneshi, Kurt Kalcher

THE EFFECT OF AGING TIME ON Mg/Al HYDROTALCITES STRUCTURES

Eddy Heraldy, Triyono, Sri Juari Santosa, Karna Wijaya, Shogo Shimazu

Книжка 1
A CONTENT ANALYSIS OF THE RESULTS FROM THE STATE MATRICULATION EXAMINATION IN MATHEMATICS

Elena Karashtranova, Nikolay Karashtranov, Vladimir Vladimirov

SOME CONCEPTS FROM PROBABILITY AND STATISTICS AND OPPORTUNITIES TO INTEGRATE THEM IN TEACHING NATURAL SCIENCES

Elena Karashtranova, Nikolay Karashtranov, Nadezhda Borisova, Dafina Kostadinova

45. МЕЖДУНАРОДНА ОЛИМПИАДА ПО ХИМИЯ

Донка Ташева, Пенка Василева

2018 година
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ЗДРАВЕ И ОКОЛНА СРЕДА

Кадрие Шукри, Светлана Великова, Едис Мехмед

РОБОТИКА ЗА НАЧИНАЕЩИ ЕНТУСИАСТИ

Даниела Узунова, Борис Велковски, Илко Симеонов, Владислав Шабански, Димитър Колев

DESIGN AND DOCKING STUDIES OF HIS-LEU ANALOGUES AS POTENTIOAL ACE INHIBITORS

Rumen Georgiev, , Tatyana Dzimbova, Atanas Chapkanov

ELECTROCHEMICAL IMPEDANCE STUDY OF BSCCO (2212) CUPRATE CERAMIC ADDITIVE TO THE ZINC ELECTRODE IN Ni-Zn BATTERIES

A. Vasev, P. Lilov, G. Ivanova, Y. Marinov, A. Stoyanova, V. Mikli, A. Stoyanova-Ivanova

CALIBRATION OF GC/MS METHOD FOR DETERMINATION OF PHTHALATES

N. Dineva, I. Givechev, D. Tanev, D. Danalev

SONOCHEMICAL SYNTHESIS OF 4-AMINOANTIPYRINE SCHIFF BASES A ND EVALUATION OF THEIR ANTIMICROBIAL, ANTI-TYROSINASE AND DPPH SCAVENGING ACTIVITIES

Maya Chochkova, Boyka Stoykova, Iva Romanova, Petranka Petrova, Iva Tsvetkova, Hristo Najdenski, Lubomira Nikolaeva- Glomb, Nadya Nikolova, Galya Ivanova, Atanas Chapkanov, Tsenka Milkova, Martin Štícha, Ivan Nemec

ELECTROSYNTHESIS OF CADMIUM SELENIDE NANOPARTICLES WITH SIMULTANEOUS EXTRACTION INTO P-XYLENE

S. S. Fomanyuk, V. O. Smilyk, G. Y. Kolbasov, I. A. Rusetskyi, T. A. Mirnaya

БИОЛОГИЧЕН АСПЕКТ НА РЕКАНАЛИЗАЦИЯ С ВЕНОЗНА ТРОМБОЛИЗА

Мариела Филипова, Даниела Попова, Стоян Везенков

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ИМОБИЛИЗИРАНЕНАФРУКТОЗИЛТРАНСФЕРАЗА ВЪРХУКОМПОЗИТНИФИЛМИОТПОЛИМЛЕЧНА КИСЕЛИНА, КСАНТАН И ХИТОЗАН

Илия Илиев, Тонка Василева, Веселин Биволарски, Ася Виранева, Иван Бодуров, Мария Марудова, Теменужка Йовчева

ELECTRICAL IMPEDANCE SPECTROSCOPY OF GRAPHENE-E7 LIQUID-CRYSTAL NANOCOMPOSITE

Todor Vlakhov, Yordan Marinov, Georgi. Hadjichristov, Alexander Petrov

ON THE POSSIBILITY TO ANALYZE AMBIENT NOISERECORDED BYAMOBILEDEVICETHROUGH THE H/V SPECTRAL RATIO TECHNIQUE

Dragomir Gospodinov, Delko Zlatanski, Boyko Ranguelov, Alexander Kandilarov

RHEOLOGICAL PROPERTIES OF BATTER FOR GLUTEN FREE BREAD

G. Zsivanovits, D. Iserliyska, M. Momchilova, M. Marudova

ПОЛУЧАВАНЕ НА ПОЛИЕЛЕКТРОЛИТНИ КОМПЛЕКСИ ОТ ХИТОЗАН И КАЗЕИН

Антоанета Маринова, Теменужка Йовчева, Ася Виранева, Иван Бодуров, Мария Марудова

CHEMILUMINESCENT AND PHOTOMETRIC DETERMINATION OF THE ANTIOXIDANT ACTIVITY OF COCOON EXTRACTS

Y. Evtimova, V. Mihailova, L. A. Atanasova, N. G. Hristova-Avakumova, M. V. Panayotov, V. A. Hadjimitova

ИЗСЛЕДОВАТЕЛСКИ ПРАКТИКУМ

Ивелина Димитрова, Гошо Гоев, Савина Георгиева, Цвета Цанова, Любомира Иванова, Борислав Георгиев

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PARAMETRIC INTERACTION OF OPTICAL PULSES IN NONLINEAR ISOTROPIC MEDIUM

A. Dakova, V. Slavchev, D. Dakova, L. Kovachev

ДЕЙСТВИЕ НА ГАМА-ЛЪЧИТЕ ВЪРХУ ДЕЗОКСИРИБОНУКЛЕИНОВАТА КИСЕЛИНА

Мирела Вачева, Хари Стефанов, Йоана Гвоздейкова, Йорданка Енева

RADIATION PROTECTION

Natasha Ivanova, Bistra Manusheva

СРАВНИТЕЛЕН АНАЛИЗ НА СЪДЪРЖАЩИТЕ СЕ ЕСТЕСТВЕНИ РАДИОНУКЛИДИ В НЕВЕН И ЛАЙКА

Сияна Димова, Цветелина Стефанова, Йорданка Енева, Нина Архангелова

СТАБИЛНОСТ НА ЕМУЛСИИ ОТ ТИПА МАСЛО/ ВОДА С КОНЮГИРАНА ЛИНОЛОВА КИСЕЛИНА

И. Милкова-Томова, Д. Бухалова, К. Николова, И. Алексиева, И. Минчев, Г. Рунтолев

THE EFFECT OF EXTRA VIRGIN OLIVE OIL ON THE HUMAN BODY AND QUALITY CONTROL BY USING OPTICAL METHODS

Carsten Tottmann, Valentin Hedderich, Poli Radusheva, Krastena Nikolova

ИНФРАЧЕРВЕНА ТЕРМОГРАФИЯ ЗА ДИАГНОСТИКА НА ФОКАЛНА ИНФЕКЦИЯ

Рая Грозданова-Узунова, Тодор Узунов, Пепа Узунова

ЕКСПЕРИМЕНТЪТ ПО ПРИЛОЖНА ФИЗИКА И НЕГОВАТА РОЛЯ ПРИ УСВОЯВАНЕТО НА ПРАКТИКО-ПРИЛОЖНИТЕ ЗНАНИЯ ОТ КУРСАНТИТЕ И СТУДЕНТИТЕ

Николай Тодоров Долчинков, Бонка Енчева Караиванова-Долчинкова, Nikolay Dolchinkov, Bonka Karaivanova-Dolchinkova

ЕЛЕКТРИЧНИ СВОЙСТВА НА КОМПОЗИТНИ ФИЛМИ ОТ ПОЛИМЛЕЧНА КИСЕЛИНА

Ася Виранева, Иван Бодуров, Теменужка Йовчева

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PHYSICS IS AN EVER YOUNG SCIENCE

Temenuzhka Yovcheva

ТРИ ИДЕИ ЗА ЕФЕКТИВНО ОБУЧЕНИЕ

Гергана Карафезиева

МАГИЯТА НА ТВОРЧЕСТВОТО КАТО ПЪТ НА ЕСТЕСТВЕНО УЧЕНЕ В УЧЕБНИЯ ПРОЦЕС

Гергана Добрева, Жаклин Жекова, Михаела Чонос

ОБУЧЕНИЕ ПО ПРИРОДНИ НАУКИ ЧРЕЗ МИСЛОВНИ КАРТИ

Виолета Стоянова, Павлина Георгиева

ИГРА НА ДОМИНО В ЧАС ПО ФИЗИКА

Росица Кичукова, Ценка Маринова

ТЪМНАТА МАТЕРИЯ В КЛАСНАТА СТАЯ

Симона Стоянова, Анета Маринова

ПРОБЛЕМИ ПРИ ОБУЧЕНИЕТО ПО ФИЗИКА ВЪВ ВВМУ „Н. Й. ВАПЦАРОВ“

А. Христова, Г. Вангелов, И. Ташев, М. Димидов

ИЗГРАЖДАНЕ НА СИСТЕМА ОТ УЧЕБНИ ИНТЕРНЕТ РЕСУРСИ ПО ФИЗИКА И ОЦЕНКА НА ДИДАКТИЧЕСКАТА ИМ СТОЙНОСТ

Желязка Райкова, Георги Вулджев, Наталия Монева, Нели Комсалова, Айше Наби

ИНОВАЦИИ В БОРБАТА С ТУМОРНИ ОБРАЗУВАНИЯ – ЛЕЧЕНИЕ ЧРЕЗ БРАХИТЕРАПИЯ

Георги Върбанов, Радостин Михайлов, Деница Симеонова, Йорданка Енева

NATURAL RADIONUCLIDES IN DRINKING WATER

Natasha Ivanova, Bistra Manusheva

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АДАПТИРАНЕ НА ОБРАЗОВАНИЕТО ДНЕС ЗА УТРЕШНИЯ ДЕН

И. Панчева, М. Недялкова, П. Петков, Х. Александров, В. Симеонов

INTEGRATED ENGINEERING EDUCATION: THE ROLE OF ANALYSIS OF STUDENTS’ NEEDS

Veselina Kolarski, Dancho Danalev, Senia Terzieva

Книжка 1
ZAGREB CONNECTION INDICES OF \(\mathrm{TiO}_{2}\) NANOTUBES

Sohaib Khalid, Johan Kok, Akbar Ali, Mohsin Bashir

SYNTHESIS OF NEW 3-[(CHROMEN-3-YL) ETHYLIDENEAMINO] -PHENYL] -THIAZOLIDIN-4ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Naser Troni, Hamit Ismaili, Malesore Pllana, Musaj Pacarizi, Veprim Thaçi, Gjyle Mulliqi-Osmani

2017 година
Книжка 6
GEOECOLOGICAL ANALYSIS OF INDUSTRIAL CITIES: ON THE EXAMPLE OF AKTOBE AGGLOMERATION

Zharas Berdenov, Erbolat Mendibaev, Talgat Salihov, Kazhmurat Akhmedenov, Gulshat Ataeva

TECHNOGENESIS OF GEOECOLOGICAL SYSTEMS OF NORTHEN KAZAKHSTAN: PROGRESS, DEVELOPMENT AND EVOLUTION

Kulchichan Dzhanaleyeva, Gulnur Mazhitova, Altyn Zhanguzhina, Zharas Berdenov, Tursynkul Bazarbayeva, Emin Atasoy

Книжка 5
47-А НАЦИОНАЛНА КОНФЕРЕНЦИЯ НА УЧИТЕЛИТЕ ПО ХИМИЯ

В последните години тези традиционни за българското учителство конфе- ренции се организират от Българското дружество по химическо образование и история и философия на химията. То е асоцииран член на Съюза на химици- те в България, който пък е член на Европейската асоциация на химическите и

SYNTHESIS OF TiO 2-M (Cd, Co, Mn) AS A PHOTOCATALYST DEGRADATION OF METHYLENE BLUE DYE

Candra Purnawan, Sayekti Wahyuningsih, Dwita Nur Aisyah

EFFECT OF DIFFERENT CADMIUM CONCENTRATION ON SOME BIOCHEMICAL PARAMETERS IN ‘ISA BROWN’ HYBRID CHICKEN

Imer Haziri, Adem Rama, Fatgzim Latifi, Dorjana Beqiraj-Kalamishi, Ibrahim Mehmeti, Arben Haziri

PHYTOCHEMICAL AND <i>IN VITRO</i> ANTIOXIDANT STUDIES OF <i>PRIMULA VERIS</i> (L.) GROWING WILD IN KOSOVO

Ibrahim Rudhani, Florentina Raci, Hamide Ibrahimi, Arben Mehmeti, Ariana Kameri, Fatmir Faiku, Majlinda Daci, Sevdije Govori, Arben Haziri

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„СИМВОЛНИЯТ КАПИТАЛ“ НА БЪЛГАРСКОТО УЧИЛИЩЕ

Николай Цанков, Веска Гювийска

KINETICS OF PHOTO-ELECTRO-ASSISTED DEGRADATION OF REMAZOL RED 5B

Fitria Rahmawati, Tri Martini, Nina Iswati

ALLELOPATHIC AND IN VITRO ANTICANCER ACTIVITY OF STEVIA AND CHIA

Asya Dragoeva, Vanya Koleva, Zheni Stoyanova, Eli Zayova, Selime Ali

NOVEL HETEROARYLAMINO-CHROMEN-2-ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Naser Troni, Hamit Ismaili, Gjyle Mulliqi-Osmani, Veprim Thaçi

Книжка 3
OPTIMIZATION OF ENGINE OIL FORMULATION USING RESPONSE SURFACE METHODOLOGY AND GENETIC ALGORITHM: A COMPARATIVE STUDY

Behnaz Azmoon, Abolfazl Semnani, Ramin Jaberzadeh Ansari, Hamid Shakoori Langeroodi, Mahboube Shirani, Shima Ghanavati Nasab

CHEMOMETRICASSISTEDSPECTROPHOTOMETRIC ESTIMATION OF LANSOPRAZOLE AND DOMEPERIDONE IN BULK AND COMMERCIAL DOSAGE FORM

Farheen Sami, Shahnaz Majeed, Tengku Azlan Shah Tengku Mohammed, Noor Fatin Amalina Kamaruddin, Mohammad Zulhimi Atan, Syed Amir Javid Bukhari, Namra, Bushra Hasan, Mohammed Tahir Ansari

EVALUATION OF ANTIBACTERIAL ACTIVITY OF DIFFERENT SOLVENT EXTRACTS OF <i>TEUCRIUM CHAMAEDRYS</i> (L. ) GROWING WILD IN KOSOVO

Arben Haziri, Fatmir Faiku, Roze Berisha, Ibrahim Mehmeti, Sevdije Govori, Imer Haziri

Книжка 2
ПРИРОДОНАУЧНАТА ГРАМОТНОСТ НА УЧЕНИЦИТЕ В НАЧАЛОТО НА XXI ВЕК – В ТЪРСЕНЕ НА КОНЦЕПТУАЛНО ЕДИНСТВО

Теодора Коларова, Иса Хаджиали, Мимия Докова, Веселин Александров

COMPUTER SIMULATORS: APPLICATION FOR GRADUATES’ADAPTATION AT OIL AND GAS REFINERIES

Irena O. Dolganova, Igor M. Dolganov, Kseniya A. Vasyuchka

SYNTHESIS OF NEW [(3-NITRO-2-OXO-2H-CHROMEN4-YLAMINO) -PHENYL] -PHENYL-TRIAZOLIDIN-4-ONES AND THEIR ANTIBACTERIAL ACTIVITY

Ramiz Hoti, Hamit Ismaili, Idriz Vehapi, Naser Troni, Gjyle Mulliqi-Osmani, Veprim Thaçi

STABILITY OF RJ-5 FUEL

Lemi Türker, Serhat Variş

A STUDY OF BEGLIKTASH MEGALITHIC COMPLEX

Diana Kjurkchieva, Evgeni Stoykov, Sabin Ivanov, Borislav Borisov, Hristo Hristov, Pencho Kyurkchiev, Dimitar Vladev, Irina Ivanova

Книжка 1
2016 година
Книжка 6
THE EFFECT OF KOH AND KCL ADDITION TO THE DESTILATION OF ETHANOL-WATER MIXTURE

Khoirina Dwi Nugrahaningtyas, Fitria Rahmawati, Avrina Kumalasari

Книжка 5
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VOLTAMMERIC SENSOR FOR NITROPHENOLS BASED ON SCREEN-PRINTED ELECTRODE MODIFIED WITH REDUCED GRAPHENE OXIDE

Arsim Maloku, Liridon S. Berisha, Granit Jashari, Eduard Andoni, Tahir Arbneshi

Книжка 3
ИЗСЛЕДВАНЕ НА ПРОФЕСИОНАЛНО-ПЕДАГОГИЧЕСКАТА РЕФЛЕКСИЯ НА УЧИТЕЛЯ ПО БИОЛОГИЯ (ЧАСТ ВТОРА)

Надежда Райчева, Иса Хаджиали, Наташа Цанова, Виктория Нечева

EXISTING NATURE OF SCIENCE TEACHING OF A THAI IN-SERVICE BIOLOGY TEACHER

Wimol Sumranwanich, Sitthipon Art-in, Panee Maneechom, Chokchai Yuenyong

NUTRIENT COMPOSITION OF CUCURBITA MELO GROWING IN KOSOVO

Fatmir Faiku, Arben Haziri, Fatbardh Gashi, Naser Troni

Книжка 2
CONTEXT-BASED CHEMISTRY LAB WORK WITH THE USE OF COMPUTER-ASSISTED LEARNING SYSTEM

N. Y. Stozhko, A. V. Tchernysheva, E.M. Podshivalova, B.I. Bortnik

Книжка 1
ПО ПЪТЯ ON THE ROAD

Б. В. Тошев

INTERDISCIPLINARY PROJECT FOR ENHANCING STUDENTS’ INTEREST IN CHEMISTRY

Stela Georgieva, Petar Todorov, Zlatina Genova, Petia Peneva

2015 година
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COMPLEX SYSTEMS FOR DRUG TRANSPORT ACROSS CELL MEMBRANES

Nikoleta Ivanova, Yana Tsoneva, Nina Ilkova, Anela Ivanova

SURFACE FUNCTIONALIZATION OF SILICA SOL-GEL MICROPARTICLES WITH EUROPIUM COMPLEXES

Nina Danchova, Gulay Ahmed, Michael Bredol, Stoyan Gutzov

INTERFACIAL REORGANIZATION OF MOLECULAR ASSEMBLIES USED AS DRUG DELIVERY SYSTEMS

I. Panaiotov, Tz. Ivanova, K. Balashev, N. Grozev, I. Minkov, K. Mircheva

KINETICS OF THE OSMOTIC PROCESS AND THE POLARIZATION EFFECT

Boryan P. Radoev, Ivan L. Minkov, Emil D. Manev

WETTING BEHAVIOR OF A NATURAL AND A SYNTHETIC THERAPEUTIC PULMONARY SURFACTANTS

Lidia Alexandrova, Michail Nedyalkov, Dimo Platikanov

Книжка 5
TEACHER’S ACCEPTANCE OF STUDENTS WITH DISABILITY

Daniela Dimitrova-Radojchikj, Natasha Chichevska-Jovanova

APPLICATION OF LASER INDUCED BREAKDOWN SPECTROSCOPY AS NONDESDUCTRIVE AND SAFE ANALYSIS METHOD FOR COMPOSITE SOLID PROPELLANTS

Amir Hossein Farhadian, Masoud Kavosh Tehrani, Mohammad Hossein Keshavarz, Seyyed Mohamad Reza Darbany, Mehran Karimi, Amir Hossein Rezayi

THE EFFECT OF DIOCTYLPHTHALATE ON INITIAL PROPERTIES AND FIELD PERFORMANCE OF SOME SEMISYNTHETIC ENGINE OILS

Azadeh Ghasemizadeh, Abolfazl Semnani, Hamid Shakoori Langeroodi, Alireza Nezamzade Ejhieh

QUALITY ASSESSMENT OF RIVER’S WATER OF LUMBARDHI PEJA (KOSOVO)

Fatmir Faiku, Arben Haziri, Fatbardh Gashi, Naser Troni

Книжка 4
БЛАГОДАРЯ ВИ!

Александър Панайотов

ТЕМАТА ВЪГЛЕХИДРАТИ В ПРОГРАМИТЕ ПО ХИМИЯ И БИОЛОГИЯ

Радка Томова, Елена Бояджиева, Миглена Славова, Мариан Николов

BILINGUAL COURSE IN BIOTECHNOLOGY: INTERDISCIPLINARY MODEL1)

V. Kolarski, D. Marinkova, R. Raykova, D. Danalev, S. Terzieva

ХИМИЧНИЯТ ОПИТ – НАУКА И ЗАБАВА

Елица Чорбаджийска, Величка Димитрова, Магдалена Шекерлийска, Галина Бальова, Методийка Ангелова

ЕКОЛОГИЯТА В БЪЛГАРИЯ

Здравка Костова

Книжка 3
SYNTHESIS OF FLUORINATED HYDROXYCINNAMOYL DERIVATIVES OF ANTI-INFLUENZA DRUGS AND THEIR BIOLOGICAL ACTIVITY

Boyka Stoykova, Maya Chochkova, Galya Ivanova, Luchia Mukova, Nadya Nikolova, Lubomira Nikolaeva-Glomb, Pavel Vojtíšek, Tsenka Milkova, Martin Štícha, David Havlíček

SYNTHESIS AND ANTIVIRAL ACTIVITY OF SOME AMINO ACIDS DERIVATIVES OF INFLUENZA VIRUS DRUGS

Radoslav Chayrov, Vesela Veselinova, Vasilka Markova, Luchia Mukova, Angel Galabov, Ivanka Stankova

NEW DERIVATIVES OF OSELTAMIVIR WITH BILE ACIDS

Kiril Chuchkov, Silvia Nakova, Lucia Mukova, Angel Galabov, Ivanka Stankova

MONOHYDROXY FLAVONES. PART III: THE MULLIKEN ANALYSIS

Maria Vakarelska-Popovska, Zhivko Velkov

LEU-ARG ANALOGUES: SYNTHESIS, IR CHARACTERIZATION AND DOCKING STUDIES

Tatyana Dzimbova, Atanas Chapkanov, Tamara Pajpanova

LACTOBACILLUS PLANTARUM AC 11S AS A BIOCATALYST IN MICROBIAL ELECYTOLYSIS CELL

Elitsa Chorbadzhiyska, Yolina Hubenova, Sophia Yankova, Dragomir Yankov, Mario Mitov

STUDYING THE PROCESS OF DEPOSITION OF ANTIMONY WITH CALCIUM CARBONATE

K. B. Omarov, Z. B. Absat, S. K. Aldabergenova, A. B. Siyazova, N. J. Rakhimzhanova, Z. B. Sagindykova

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TEACHING CHEMISTRY AT TECHNICAL UNIVERSITY

Lilyana Nacheva-Skopalik, Milena Koleva

ФОРМИРАЩО ОЦЕНЯВАНЕ PEER INSTRUCTION С ПОМОЩТА НА PLICКERS ТЕХНОЛОГИЯТА

Ивелина Коцева, Мая Гайдарова, Галина Ненчева

VAPOR PRESSURES OF 1-BUTANOL OVER WIDE RANGE OF THEMPERATURES

Javid Safarov, Bahruz Ahmadov, Saleh Mirzayev, Astan Shahverdiyev, Egon Hassel

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РУМЕН ЛЮБОМИРОВ ДОЙЧЕВ (1938 – 1999)

Огнян Димитров, Здравка Костова

NAMING OF CHEMICAL ELEMENTS

Maria Atanassova

2014 година
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LUBRICATION PROPERTIES OF DIFFERENT PENTAERYTHRITOL-OLEIC ACID REACTION PRODUCTS

Abolfazl Semnani, Hamid Shakoori Langeroodi, Mahboube Shirani

ALLELOPATHIC AND CYTOTOXIC ACTIVITY OF ORIGANUM VULGARE SSP. VULGARE GROWING WILD IN BULGARIA

Asya Pencheva Dragoeva, Vanya Petrova Koleva, Zheni Dimitrova Nanova, Mariya Zhivkova Kaschieva, Irina Rumenova Yotova

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GENDER ISSUES OF UKRAINIAN HIGHER EDUCATION

Н.H.Petruchenia, M.I.Vorovka

МНОГОВАРИАЦИОННА СТАТИСТИЧЕСКА ОЦЕНКА НА DREEM – БЪЛГАРИЯ: ВЪЗПРИЕМАНЕ НА ОБРАЗОВАТЕЛНАТА СРЕДА ОТ СТУДЕНТИТЕ В МЕДИЦИНСКИЯ УНИВЕРСИТЕТ – СОФИЯ

Радка Томова, Павлина Гатева, Радка Хаджиолова, Зафер Сабит, Миглена Славова, Гергана Чергарова, Васил Симеонов

MUSSEL BIOADHESIVES: A TOP LESSON FROM NATURE

Saâd Moulay Université Saâd Dahlab de Blida, Algeria

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ЕЛЕКТРОННО ПОМАГАЛO „ОТ АТОМА ДО КОСМОСА“ ЗА УЧЕНИЦИ ОТ Х КЛАС

Силвия Боянова Професионална гимназия „Акад. Сергей П. Корольов“ – Дупница

ЕСЕТО КАТО ИНТЕГРАТИВЕН КОНСТРУКТ – НОРМАТИВЕН, ПРОЦЕСУАЛЕН И ОЦЕНЪЧНО-РЕЗУЛТАТИВЕН АСПЕКТ

Надежда Райчева, Иван Капурдов, Наташа Цанова, Иса Хаджиали, Снежана Томова

44<sup>-ТA</sup> МЕЖДУНАРОДНА ОЛИМПИАДА ПО ХИМИЯ

Донка Ташева, Пенка Василева

ДОЦ. Д.П.Н. АЛЕКСАНДЪР АТАНАСОВ ПАНАЙОТОВ

Наташа Цанова, Иса Хаджиали, Надежда Райчева

COMPUTER ASSISTED LEARNING SYSTEM FOR STUDYING ANALYTICAL CHEMISTRY

N. Y. Stozhko, A. V. Tchernysheva, L.I. Mironova

С РАКЕТНА ГРАНАТА КЪМ МЕСЕЦА: БОРБА С ЕДНА ЛЕДЕНА ЕПОХА В ГОДИНАТА 3000 СЛЕД ХРИСТА. 3.

С РАКЕТНА ГРАНАТА КЪМ МЕСЕЦА:, БОРБА С ЕДНА ЛЕДЕНА ЕПОХА, В ГОДИНАТА 000 СЛЕД ХРИСТА. .

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ВИСША МАТЕМАТИКА ЗА УЧИТЕЛИ, УЧЕНИЦИ И СТУДЕНТИ: ДИФЕРЕНЦИАЛНО СМЯТАНЕ

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

ВАСИЛ ХРИСТОВ БОЗАРОВ

Пенка Бозарова, Здравка Костова

ЖИВАТА ПРИРОДА

Б. В. Тошев

БИБЛИОГРАФИЯ НА СТАТИИ ЗА МИСКОНЦЕПЦИИТЕ В ОБУЧЕНИЕТО ПО ПРИРОДНИ НАУКИ ВЪВ ВСИЧКИ ОБРАЗОВАТЕЛНИ НИВА

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

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BOTYU ATANASSOV BOTEV

Zdravka Kostova, Margarita Topashka-Ancheva

CHRONOLOGY OF CHEMICAL ELEMENTS DISCOVERIES

Maria Atanassova, Radoslav Angelov

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КАК ДА МОТИВИРАМЕ УЧЕНИЦИТЕ OT VII КЛАС ДА УЧАТ

Маргарита Бозова, Петко Бозов

ОБРАЗОВАНИЕ ЗА ПРИРОДОНАУЧНА ГРАМОТНОСТ

Адриана Тафрова-Григорова

2013 година
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DIFFERENTIAL TEACHING IN SCHOOL SCIENCE EDUCATION: CONCEPTUAL PRINCIPLES

G. Yuzbasheva Kherson Academy of Continuing Education, Ukraine

АНАЛИЗ НА ПОСТИЖЕНИЯТА НА УЧЕНИЦИТЕ ОТ ШЕСТИ КЛАС ВЪРХУ РАЗДЕЛ „ВЕЩЕСТВА И ТЕХНИТЕ СВОЙСТВА“ ПО „ЧОВЕКЪТ И ПРИРОДАТА“

Иваничка Буровска, Стефан Цаковски Регионален инспекторат по образованието – Ловеч

HISTORY AND PHILOSOPHY OF SCIENCE: SOME RECENT PERIODICALS (2013)

Chemistry: Bulgarian Journal of Science Education

45. НАЦИОНАЛНА КОНФЕРЕНЦИЯ НА УЧИТЕЛИТЕ ПО ХИМИЯ

„Образователни стандарти и природонаучна грамотност“ – това е темата на състоялата се от 25 до 27 октомври 2013 г. в Габрово 45. Национална конфе- ренция на учителите по химия с международно участие, която по традиция се проведе комбинирано с Годишната конференция на Българското дружество за химическо образование и история и философия на химията. Изборът на темата е предизвикан от факта, че развиването на природонаучна грамотност е обща тенденция на реформите на учебните програми и главна

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ЗА ХИМИЯТА НА БИРАТА

Ивелин Кулев

МЕТЕОРИТЪТ ОТ БЕЛОГРАДЧИК

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

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RECASTING THE DERIVATION OF THE CLAPEYRON EQUATION INTO A CONCEPTUALLY SIMPLER FORM

Srihari Murthy Meenakshi Sundararajan Engineering College, India

CHEMICAL REACTIONS DO NOT ALWAYS MODERATE CHANGES IN CONCENTRATION OF AN ACTIVE COMPONENT

Joan J. Solaz-Portolés, Vicent Sanjosé Universitat de Valènciа, Spain

POLYMETALLIC COMPEXES: CV. SYNTHESIS, SPECTRAL, THERMOGRAVIMETRIC, XRD, MOLECULAR MODELLING AND POTENTIAL ANTIBACTERIAL PROPERTIES OF TETRAMERIC COMPLEXES OF Co(II), Ni(II), Cu(II), Zn(II), Cd(II) AND Hg(II) WITH OCTADENTATE AZODYE LIGANDS

Bipin B. Mahapatra, S. N. Dehury, A. K. Sarangi, S. N. Chaulia G. M. Autonomous College, India Covt. College of Engineering Kalahandi, India DAV Junior College, India

ПРОФЕСОР ЕЛЕНА КИРКОВА НАВЪРШИ 90 ГОДИНИ

CELEBRATING 90TH ANNIVERSARY OF PROFESSOR ELENA KIRKOVA

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SIMULATION OF THE FATTY ACID SYNTHASE COMPLEX MECHANISM OF ACTION

M.E.A. Mohammed, Ali Abeer, Fatima Elsamani, O.M. Elsheikh, Abdulrizak Hodow, O. Khamis Haji

FORMING OF CONTENT OF DIFFERENTIAL TEACHING OF CHEMISTRY IN SCHOOL EDUCATION OF UKRAINE

G. Yuzbasheva Kherson Academy of Continuing Education, Ukraine

ИЗСЛЕДВАНЕ НА РАДИКАЛ-УЛАВЯЩА СПОСОБНОСТ

Станислав Станимиров, Живко Велков

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COLORFUL EXPERIMENTS FOR STUDENTS: SYNTHESIS OF INDIGO AND DERIVATIVES

Vanessa BIANDA, Jos-Antonio CONSTENLA, Rolf HAUBRICHS, Pierre-Lonard ZAFFALON

OBSERVING CHANGE IN POTASSIUM ABUNDANCE IN A SOIL EROSION EXPERIMENT WITH FIELD INFRARED SPECTROSCOPY

Mila Ivanova Luleva, Harald van der Werff, Freek van der Meer, Victor Jetten

ЦАРСКАТА ПЕЩЕРА

Рафаил ПОПОВ

УЧИЛИЩНИ ЛАБОРАТОРИИ И ОБОРУДВАНЕ SCHOOL LABORATORIES AND EQUIPMENT

Учебни лаборатории Илюстрации от каталог на Franz Hugershoff, Лайциг, притежаван от бъдещия

2012 година
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ADDRESING STUDENTS’ MISCONCEPTIONS CONCERNING CHEMICAL REACTIONS AND SYMBOLIC REPRESENTATIONS

Marina I. Stojanovska, Vladimir M. Petruševski, Bojan T. Šoptrajanov

АНАЛИЗ НА ПОСТИЖЕНИЯТА НА УЧЕНИЦИТЕ ОТ ПЕТИ КЛАС ВЪРХУ РАЗДЕЛ „ВЕЩЕСТВА И ТЕХНИТЕ СВОЙСТВА“ ПО ЧОВЕКЪТ И ПРИРОДАТА

Иваничка Буровска, Стефан Цаковски Регионален инспекторат по образованието – Ловеч

ЕКОТОКСИКОЛОГИЯ

Васил Симеонов

ПРОФ. МЕДОДИЙ ПОПОВ ЗА НАУКАТА И НАУЧНАТА ДЕЙНОСТ (1920 Г.)

Проф. Методий Попов (1881-1954) Госпожици и Господа студенти,

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КОНЦЕПТУАЛНА СХЕМА НА УЧИЛИЩНИЯ КУРС П О ХИМИЯ – МАКР О СКОПСКИ ПОДХОД

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

ROLE OF ULTRASONIC WAVES TO STUDY MOLECULAR INTERACTIONS IN AQUEOUS SOLUTION OF DICLOFENAC SODIUM

Sunanda S. Aswale, Shashikant R. Aswale, Aparna B. Dhote Lokmanya Tilak Mahavidyalaya, INDIA Nilkanthrao Shinde College, INDIA

SIMULTANEOUS ESTIMATION OF IBUPROFEN AND RANITIDINE HYDROCHLORIDE USING UV SPECTROPHOT O METRIC METHOD

Jadupati Malakar, Amit Kumar Nayak Bengal College of Pharmaceutical Sciences and Research, INDIA

GAPS AND OPPORTUNITIES IN THE USE OF REMOTE SENSING FOR SOIL EROSION ASSESSMENT

Mila Ivanova Luleva, Harald van der Werff, Freek van der Meer, Victor Jetten

РАДИОХИМИЯ И АРХЕОМЕТРИЯ: ПРО Ф. ДХН ИВЕЛИН КУЛЕВ RADIOCHEMISTRY AND ARCHEOMETRY: PROF. IVELIN KULEFF, DSc

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

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TEACHING THE CONSTITUTION OF MATTER

Małgorzata Nodzyńska, Jan Rajmund Paśko

СЪСИРВАЩА СИСТЕМА НА КРЪВТА

Маша Радославова, Ася Драгоева

CATALITIC VOLCANO

CATALITIC VOLCANO

43-ТА МЕЖДУНАРОДНА ОЛИМПИАДА ПО ХИМИЯ

Донка ТАШЕВА, Пенка ЦАНОВА

ЮБИЛЕЙ: ПРОФ. ДХН БОРИС ГЪЛЪБОВ JUBILEE: PROF. DR. BORIS GALABOV

Б. В. Тошев Българско дружество за химическо образование и история и философия на химията

ПЪРВИЯТ ПРАВИЛНИК ЗА УЧЕБНИЦИТЕ (1897 Г.)

Чл. 1. Съставянето и издаване на учебници се предоставя на частната инициа- тива. Забележка: На учителите – съставители на учебници се запрещава сами да разпродават своите учебници. Чл. 2. Министерството на народното просвещение може да определя премии по конкурс за съставяне на учебници за горните класове на гимназиите и специ- алните училища. Чл. 3. Никой учебник не може да бъде въведен в училищата, ако предварително не е прегледан и одобрен от Министерството на народното просвещение. Чл.

JOHN DEWEY: HOW WE THINK (1910)

John Dewey (1859 – 1952)

ИНФОРМАЦИЯ ЗА СПЕЦИАЛНОСТИТЕ В ОБЛАСТТА НА ПРИРОДНИТЕ НАУКИ В СОФИЙСКИЯ УНИВЕРСИТЕТ „СВ. КЛИМЕНТ ОХРИДСКИ“ БИОЛОГИЧЕСКИ ФАКУЛТЕТ

1. Биология Студентите от специалност Биология придобиват знания и практически умения в областта на биологическите науки, като акцентът е поставен на организмово равнище. Те се подготвят да изследват биологията на организмите на клетъчно- организмово, популационно и екосистемно ниво в научно-функционален и прило- жен аспект, с оглед на провеждане на научно-изследователска, научно-приложна, производствена и педагогическа дейност. Чрез широк набор избираеми и факул- тативни курсове студентите

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УЧИТЕЛИТЕ ПО ПРИРОДНИ НАУКИ – ЗА КОНСТРУКТИВИСТКАТА УЧЕБНА СРЕДА В БЪЛГАРСКОТО УЧИЛИЩЕ

Адриана Тафрова-Григорова, Милена Кирова, Елена Бояджиева

ПОВИШАВАНЕ ИНТЕРЕСА КЪМ ИСТОРИЯТА НА ХИМИЧНИТЕ ЗНАНИЯ И ПРАКТИКИ ПО БЪЛГАРСКИТЕ ЗЕМИ

Людмила Генкова, Свобода Бенева Българско дружество за химическо образование и история и философия на химията

НАЧАЛО НА ПРЕПОДАВАНЕТО НА УЧЕБЕН ПРЕДМЕТ ХИМИЯ В АПРИЛОВОТО УЧИЛИЩЕ В ГАБРОВО

Мария Николова Национална Априловска гимназия – Габрово

ПРИРОДОНАУЧНОТО ОБРАЗОВАНИЕ В БЪЛГАРИЯ – ФОТОАРХИВ

В един дълъг период от време гимназиалните учители по математика, физика, химия и естествена

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„МАГИЯТА НА ХИМИЯТА“ – ВЕЧЕР НА ХИМИЯТА В ЕЗИКОВА ГИМНАЗИЯ „АКАД. Л. СТОЯНОВ“ БЛАГОЕВГРАД

Стефка Михайлова Езикова гимназия „Акад. Людмил Стоянов“ – Благоевград

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Бурният развой на естествознанието във всичките му клонове през XIX –ия век предизвика дълбоки промени в мирогледа на културния свят, в техниката и в индустрията, в социалните отношения и в държавните интереси. Можем ли днес да си представим един философ, един държавен мъж, един обществен деец, един индустриалец, просто един културен човек, който би могъл да игнорира придобив- ките на природните науки през последния век. Какви ужасни катастрофи, какви социални сътресения би сполетяло съвре

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MURPHY’S LAW IN CHEMISTRY

Milan D. Stojković

42-рa МЕЖДУНАРОДНА ОЛИМПИАДА ПО ХИМИЯ

Донка Ташева, Пенка Цанова

СЕМЕЙНИ УЧЕНИЧЕСКИ ВЕЧЕРИНКИ

Семейството трябва да познава училишето и училишето трябва да познава семейството. Взаимното познанство се налага от обстоятелството, че те, макар и да са два различни по природата си фактори на възпитанието, преследват една и съща проста цел – младото поколение да бъде по-умно, по-нравствено, физически по-здраво и по-щастливо от старото – децата да бъдат по-щастливи от родителите