Lucia Odochian

Thermal analysis of some complexes LH[Cr(NCS)4L2].xH2O (L=NH3 or organic base)

Data obtained by thermal analysis of K3[Cr(NCS)6].4H2O and some derivatives, LH[Cr(NCS)4L2].xH2O, where L=NH3 or an organic base, are reported. The TG, DTG and DTA curves show common behaviour (SCN− ligand decomposition) as well as specific behaviour for each complex due to the base L, which complicates the thermal decomposition of the complexes. Some weak bases with low boiling points are easily eliminated, which determines the common thermal behaviour of the complexes.A general mechanism of thermal decomposition is advanced involving dehydration and decomposition processes for both LH+ and [Cr(NCS)4L2]−. The apparent activation energies of different processes confirm the thermal decomposition mechanisms of the complexes under study.ZusammenfassungDie thermische Analyse von K3[Cr(NCS)6].4H2O und einigen Derivaten der allgemeinen Formel LH[Cr(NCS)4L2].xH2O (L=NH3 oder eine organische Base) betreffende Daten werden angegeben. Die TG-, DTG- und DTA-Kurven zeigen sowohl gemeinsame Charakteristika (Zersetzung des Liganden SCN−) als auch für jeden Komplex spezifische, durch die Base L bedingte Züge, die die thermische Zersetzung der Komplexe komplizieren. Einige schwache Basen mit niedrigen Siedepunkten werden leicht eliminiert, was ein gleiches thermisches Verhalten dieser Komplexe zur Folge hat. Ein allgemeiner Mechanismus der thermischen Zersetzung wird angegeben, der die Dehydratisierung und die Zersetzungsprozesse sowohl für LH+ als auch für [Cr(NCS)4L2]− in sich einschließt. Die scheinbaren Aktivierungsenergien der verschiedenen Prozesse sind mit dem Mechanismus der thermischen Zersetzung der Untersuchten Komplexe im Einklang.РезюмеПроведен термически й анализ соединения K3[Cr(NCS)6].4H2O и некоторых его производных типа LH[Cr(NCS)4L2].xН2О, где L=NH3 или какое-либо органичес кое основание. ТГ, ДТГ и ДТА-кривые пок азали как общее, так и специфическое повед ение каждого комплек са, обусловленное харак тером лиганда и услож няющего термическое разложе ние комплексов. Некоторые слабоосно вные лиганды с низкой точкой кипения легко выделя ются, что и определяет общее тер мическое поведение к омплексов. Выдвинут общий механ изм термического разложения, включая п роцесс дегидратации и разложения обоих LH+ и [Cr(NCS)4L2]−. Кажущиеся энергии ак тивации различных пр оцессов подтверждают механи зм термического разложения исследов анных комплексов.

Problem solving - an interactive active method for teaching the thermokinetic concept

Abstract The paper describes a strategy that uses problem solving to teach the thermokinetic concept, based on student’s previously established proficiency in thermochemistry and kinetics. Chemistry teachers often use this method because it ensures easy achievement of both formative and informative science skills. This teaching strategy is tailored for students that prove special intellectual resources, Olympiad participants and to those who find chemistry a potential professional route

Study on the thermal behavior of casein in air

Abstract The present paper is focused on the study of the thermal behavior of casein, the main protein in milk, by applying the TG-FTIR technique and calorimetric measurements. The research is of a great interest due to the large application areas of casein in cosmetic, food and pharmaceutical industries. The analysis of the thermal behavior by the TG-DTG-DTA methods allwos the finding of the temperature range where the casein is thermally stable and the caseincontaining cosmetics, food and pharmaceutical products proper for using. The identification of the gaseous species released allwos the TG-FTIR coupled technique to give useful information on the possible environmental impact when the casein-containing products are used at temperatures above the casein initial degradation temperature. The combustion heat of casein estimated by means of the Berthelot calorimeter made evident this value to be close to those of the most important and used fuels which would recommend the waste casein-containing products to be used as fuels.