2011 – International Year of Chemistry
History of the Union of Bulgarian Chemists. III. The First Ten Years (1925-1934)- Selected Documents
Резюме. This article provides information on the annual conferences of the
Union of Bulgarian chemists in the first ten years of Union’s existence – 1925 – 1934. All presented documents were published in the Union’s journal „Chemistry and Industry“.
Keywords: Union of Bulgarian Chemists, history, annual congresses
N. NaydenovВлезте в системата, за да прочетете пълната статия
44th National Conference of the Bulgarian Teachers in Chemistry
B.V. ToshevВлезте в системата, за да прочетете пълната статия
Avoiding Misunderstandings in School Teaching by Acquainting with Historical Texts: Mass Action Law
Резюме. There have always been incorrect or imprecise concepts and claims in school chemistry textbooks. The analysis of errors and misconceptions in the academic literature is important because what is being taught wrong in the early stages of training in chemistry, not subject to change or reassessment in the late stages of education or professional practice. A typical example is the presentation of the basic kinetic equation – concentration dependence of the rate of chemical reaction, as the law of mass action. This is a mistake because the law of mass action is a law of chemical thermodynamics, while the concentration dependence of the rate of chemical reaction is the basic postulate of chemical kinetics. This article reproduces the original derivation of the law of mass action, as has been presented in a book (1903) by Harry Clary Jones. This approach to the chemical equilibrium has advantages commented in details in the present paper.
Keywords: chemical equilibrium, misunderstandings in chemistry, mass action law, Harry Clary Jones, Gutenberg teaching method
B.V. Toshev, Z. PetevaВлезте в системата, за да прочетете пълната статия
Theory as a Component of Biology and Chemistry Curricula in Secondary School
Резюме. Theories are essential part of scientific knowledge and curriculum in natural sciences (e.g., physics, chemistry, biology). They represent highly summarized and coherent knowledge with broad scope for application. Investigating character of theories defines ways of transformation in learning. Typically, cognitive essence of theory could be part of education in sciences. Under these considerations main topics of the article are as follows: (a) Analysis of the essence of theory as philosophical category and specific cognitive construct; (b) The presence of theory as component of Biology and Chemistry curricula; (c) Some technological aspects of learning theories in Biology and Chemistry in secondary school.
Keywords: education theory, knowledge, curriculum, problems
N. Tzanova, N. RaychevaВлезте в системата, за да прочетете пълната статия
2011 – International Year of Chemistry
Резюме. The development of the concepts for ï¿½Green Chemistryï¿½ and the main principles of this new field are reviewed. Examples of the application of these principles in different areas of chemistry are included. The frequently used alternative solvents (green solvents ï¿½ water, PEG, glycerol, perfluorinated solvents, supercritical and ionic liquids) in preparative organic chemistry are described in details. The present and the future developments of green chemistry in education and organic chemical technology are considered.
Keywords: green chemistry, principles of green chemistry, green solvents, teaching & learning
T. Deligeorgiev, N. Gadjev, A. Vasilev, S. Kaloyanova, N. Lesev, A. AlexievВлезте в системата, за да прочетете пълната статия
Chemistry & History of Chemistry: An Online Supplement
Alkylation of Aniline with Ethanol Over Nanocrystalline ZnFe2-xAlxO4 (x= 0, 0.25, 0.50, 0.75 and 1) Ferrite System
Резюме. N-alkylation of aniline with ethanol has been studied in vapour phase
in a fixed bed reactor over ZnFe2-x AlxO4 (X= 0, 0.25, 0.50, 0.75 and 1). N-ethylaniline(NEA) and N, N-diethyl anilines (NNDEA) were found to be major products. It was observed that systems possessing high ‘x’ values are highly selective for N-ethylaniline.Reaction parameters were optimized over ZnFeAlO4 catalyst. A maximum yield of 74 % of N-ethyl aniline with selectivity of 98% and 1.5 % of N, N-diethylaniline with selectivity of 2 % was obtained over ZnFeAlO4 catalyst at a temperature of 523K, ethanol to aniline molar ratio 6 and weight hour space velocity of 0.17 h-1. Catalyst characterization has been made by XRD, IR, Mössbauer spectroscopy, ammonia desorption and BET surface area measurements. All catalysts show their characteristic M-O stretching bands around 700 and 500 cm-1 associated with tetrahedral and octahedral sites respectively. All catalysts were found to show weak, medium and strong acidic sites corresponding to ammonia desorption in different temperature ranges 423 523,523-623 and 623-723 K. Mössbauer measurement suggests formation of homogenous solid solution in all the samples and increase in acidity of the samples with increasing incorporation of aluminum. A tentative mechanism for production of N Ethyl anilines has been proposed.
Keywords: aluminium ferrite, ferrospinels, ethylation of aniline, N-ethylaniline
R. Dwivedi, R. Dixit, S. Saxena, S. BhadauraВлезте в системата, за да прочетете пълната статия