The results of an exercise on electrochemistry for General Chemistry students are presented. The difficulty encountered by students in predicting the shift in the potential of the hydrogen electrode under non-standard conditions prompted a search in textbooks on how the subject is developed. Besides several instances of inconsistencies in defining the standard state, such as including the temperature in the definition, a number of incorrect depictions of the hydrogen electrode were discovered. Of the 28 General Chemistry books, 16 Physical Chemistry books and 24 Internet pages, 30, 20 and 46%, respectively, showed devices that would not work in practice.

In an attempt to improve the performance of organolanthanide catalysts we investigated the use of the industrially important cocatalyst methylaluminoxane (MAO) to activate organolanthanide compounds in olefin polymerization. The catalytic systems LnBrCp2(THF)2/MAO (Cp=cyclopentadienyl) and LnBrCp*2THF/MAO (Cp*= pentamethylcyclopentadienyl), Ln=Pr and Yb, were active in styrene polymerization but inactive in ethylene and propylene polymerization. These systems produced atactic polystyrene with conversions of up to 8.2% (PrBrCp*2THF, Al/Ln=200, T=80ºC, t=4 h) in toluene. In the absence of solvent, the conversion is 26.0% (1.5 h) and the molar mass of the atactic polystyrene is almost ten times higher (43 kg/mol).

A demonstractive experiment was proposed in order to verify students' habilities in recognizing the presence and nature of ions in solutions, before and after their passage through ion-exchange columns. The students have no previous contact with ion-exchange resins, so they must deduce how they work and explain the experimental facts. The performance of classes, at different stages of learning, is compared and discussed.

OBJETIVO: Avaliar o uso do laser de vapor de cobre no tratamento da endometriose cirurgicamente induzida em coelhas.MÉTODOS: 42 coelhas da raça New Zealand foram submetidas à indução experimental da endometriose, de acordo com técnica cirúrgica padronizada. Após 30 dias da indução, um grupo de 29 animais foi submetido ao tratamento pelo laser de vapor de cobre (LVC) em tempos que variaram de 2, 5, 15, 30 e 60 segundos e, outro grupo de 13 coelhas, serviu como controle, tendo-se realizado apenas a laparotomia, sem que fosse realizado algum tratamento. Após 15 dias da segunda laparotomia realizou-se avaliação histopatológica quanto à presença de endometriose, glândulas e estroma. RESULTADOS: O modelo experimental de indução da endometriose foi adequado, com 100% de eficácia. O tratamento com LVC mostrou-se eficiente, com destruição da doença em 31,00 % dos casos. Nas coelhas tratadas que ainda tinham a lesão, houve diminuição em 69,85 % na quantidade de glândulas. A destruição do estroma aconteceu em 41,38% dos casos, no grupo laser. CONCLUSÃO: Os resultados mostraram que o LVC é uma ferramenta adequada para o tratamento da endometriose, como o observado em coelhas.

OBJECTIVE: To evaluate the use of copper vapor laser in treatment of the surgically induced endometriosis in rabbits. METHODS: 42 New Zeland rabbits were submitted to the experimental induction of the endometriosis, in agreement with standardized surgical technique. After 30 days of the induction, a group of 29 animals was submitted to the treatment by copper vapor laser (CVL) in times that varied of 2, 5, 15, 30 and 60 seconds and, other group of 13 rabbits served as control without any treatment. After 15 days of the second laparotomy, histopatologic evaluations have done with relationship to the endometriosis presence, glands and estroma. RESULTS: The experimental model of endometriosis induction was adequated, with 100% of effectiveness. The treatment with LVC was shown efficient, with destruction of the disease in 31,00% of the cases. In the rabbits that still had the lesion, there was decrease in 69,85% of glands amount. The destruction of the stroma ocurred in 41,38% of the cases, in the group laser. CONCLUSION: The results showed that the CVL is a adequated tool for the endometriosis treatment as observed in rabbits.

In this work we report the synthesis of some organolanthanide compounds which were identified as LnCl2Cp(PzA)2, Ln = Nd, Sm, Eu and Tb, Cp = cyclopentadienyl and PzA = pirazinamide, by elemental analyses, complexometric titration with EDTA, thermal analyses and IR spectra. Thermal analysis and infrared spectra indicated that the coordination of the pyrazinamide to the lanthanide ions was made by the O atom of the carbonyl group and by one or both N atoms of the pyrazinamide ring. This class of compound showed catalytic activity of ca. 4.0 to 6.4 kgPE molLn-1 h-1 bar-1, in ethylene polymerization, using methylaluminoxane as cocatalyst. The resulting polyethylene presented low crystallinity (20%).

Aluminum metal and aluminum compounds have many applications in several branches of the industry and in our daily lives. The most important raw material for aluminum and its manufactured compounds is bauxite, a rock constituted mainly by aluminum hydroxides minerals. In this work, a didactic experiment aiming the preparation of alumina and potassium alum starting from bauxite is proposed for undergraduate students. Both compounds are of great commercial, scientific and historical interest. The experiment involves applications of important chemical principles such as acid-base and precipitation. Some chemical properties and uses of aluminum compounds are also illustrated.

A didactic experiment is proposed in order to identify inorganic phosphates in home laundry detergents by ascending paper chromatography. Chemical principles related with hard water are also investigated. The role of polyphosphates in detergent formulations is discussed and the softening of hard water by sodium tripolyphosphate is illustrated. Several chemical concepts, related to the daily experience of the students, can be explored in post-lab discussions.

In this work we present the synthesis and characterization of some organolanthanide compounds [LnCp2Cl.PPh3], Ln = La, Nd, Eu, Yb and Lu. The catalytic activity of these compounds has been verified in cyclohexene hydrogenation. Cyclohexane was identified by¹H NMR analysis in the reaction products.