Scielo RSS <![CDATA[Journal of the Chilean Chemical Society]]> http://www.scielo.cl/rss.php?pid=0717-970720080001&lang=es vol. 53 num. 1 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[<b>In memory of Dr. Jaime Retuert de la Torre</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100001&lng=es&nrm=iso&tlng=es <![CDATA[<b>METAL COMPOUNDS OF THE TCNX REDOX SYSTEMS -FROM ELECTRON TRANSFER TO SPIN DISTRIBUTION AND MAGNETISM</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100002&lng=es&nrm=iso&tlng=es The TCNX ligands, TCNE (tetracyanoethene), TCNQ (7,7,8,8-tetracyano-p-quinodimethane), and TCNB (1,2,4,5-tetracyanobenzene), are capable of bridging up to four metal centers in discrete molecular complexes or coordination polymers. In addition, the highly non-innocent TCNX ligands may exist in neutral n acceptor form, as stable monoanionic radicals, or as dianions, which has generated a unique coordination chemistry. Several such compounds, particular those involving the TCNX'" bridges, have found interest for molecular magnetism studies, organic conductor research, and in concepts of molecular computing. This contribution focuses on the chemical potential for new materials and on their physical characterization, especially with respect to the TCNX/metal electron transfer and to the spin distribution in paramagnetic states <![CDATA[<b>BINDING OF URANYL IONS BY WATER-INSOLUBLE POLYMERS CONTAINING MULTILIGAND GROUPS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100003&lng=es&nrm=iso&tlng=es The crosslinked resins poly(N-(3-dimethylamino)propylmethacrylamide) P(NDAPA), poly((3-dimethylamino)propylacrylate)P(DAPA), poly(4-acryloylmorpholine-co-acrylic acid) P(AMo-AA), poly(N-(3-dimethylamino)propylmethacrylamide-co-4-vinyl pyridine) P(NDAPA-VPy) and poly((3-dimethyl amino)propylacrylate-co-acrylic acid) P(DAPA-AA), poly(N-(3-dimethylamino)propylmethacrylamide-co-acrylic acid) P(NDAPA-AA) were obtained by radical polymerization. These resins were completely insoluble in water. The uptake metal ion properties were studied by batch equilibrium procedure for copper(II) and uranyl ions <![CDATA[<b>A NEW LINDQVIST-TYPE HEXAMOLYBDATE CLUSTER FUNCTIONALIZED WITH THE jt-DONOR LIGAND 4-BROMO-2,6-DIMETHYLPHENYLIMIDO</b>: <b>SPECTROSCOPIC, ELECTROCHEMICAL AND STRUCTURAL STUDIES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100004&lng=es&nrm=iso&tlng=es A new ionic organic-inorganic hybrid complex of formula («-Bu4N)2[Mo(¡0(18)(NR)]¹/2Me2CO, R = -C6H2-2,6-Me2-4-Br, (w-Bu4N)2[l]-i4Me2CO, has been prepared in acetonitrile by reacting tetrabutylammonium a-octamolybdate, («-Bu4N)4[0t-Mo8O26], with 2,6-dimethyl-4-bromoaniline hydrochloride, 2,6-Me2-4-Br-C6H2NH2HCl, using N,N'-dicyclohexylcarbodiimide, (C6H U)N=C=N(C6H11), as dehydrating agent. This complex, formulated as («-Bu4N)2[l]¹/2Me2CO, contains a C-Br group which can be functionahzed for constructing novel hybrid materials. The complex was fully characterized by IR, UV-Vis, 'H- and "C-NMR spectroscopies, and authenticated by single crystal X-ray diffraction analysis. The asymmetric unit contains two crystallographically independent anions, [l]²", differing by the orientation of the phenyl ring relative to the hexamolybdate skeleton, and one molecule of acetone. Both molecules differ in the angles Mo(l)-N(l)-C(l)= 172.2(6) and Mo(7)-N(2)-C(9)= 175.6(6)°. These angles, near to 180°, indicate the presence of a Mo=N triple bond <![CDATA[<b>NUCLEATION AND SELECTIVE GROWTH OFPOLYMORPHS OF CALCIUM CARBONATE ON ORGANIC-INORGANIC HYBRID FILMS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100005&lng=es&nrm=iso&tlng=es Inorganic/organic ternary hybrid films that are constituted of gelatin (G), poly(monomethyl itaconate) (PMMI) and silica (Si0(2)), are used as a solid matrix to study the crystalization of calcium carbonate (CaC0(3)). These films are transparent and stable in aqueous solutions due to the formation of interpenetrated networks. In these films it is possible to modulate the concentration of the different functional groups and the flexibility of the film structure by changing the composition. These changes in composition affected the morphology of the CaC0(3) crystals and the polymorph obtained on the films. Depending on the film compositions, fried-egg-like or spherical calcite particles were observed on the films. Films of a specific composition induced the nucleation of vaterite, the less stable polymorph of calcium carbonate <![CDATA[<b>PREPARATION OF NANOCOMPOSITES BY IN SITU POLIMERIZATION</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100006&lng=es&nrm=iso&tlng=es Polyethylene nanocomposites were obtained by in situ polymerization using both montmorillonite (natural clay) and montmorillonite organically modified with octadecylamine (O-Clo). In this proposed methodology the clays were added directly in the reactor together with the catalytic system (metallocene catalyst and methylaluminoxane) and ethylene. The nanocomposites were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM), and by tensile stress-strain tests. It was found that the catalytic activity increased around 20% when natural clay was used compared with the standard polymer. But when modified clay was used the catalytic activity did not show important changes. On the other hand, XRD and TEM showed that the clays are in a disordered state and well dispersed in the polyethylene matrix. Finally, the nanocomposites showed an increase of about 30% in Young's modulus compared with the standard polymer <![CDATA[<b>ESSENTIAL OIL COMPOSITION OF <i>ARISTOLOCHIA CHILENSIS </i>A HOST PLANT OF <i>BATTUS POLYDAMAS</i></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100007&lng=es&nrm=iso&tlng=es In this communication we report the essential oil composition of Aristolochia chilensis Bridges ex Lindl. fresh leaves. This species is one of the larval food-plants of Battus polydamas Boisd., the only butterfly of the family Papihonidae (Lepidoptera) occurring in Chile. In order to determine possible chemical similarities among several of its host species distributed throughout the continent, we compared these results with data obtained from literature on the composition of other representative Aristolochia species occurring in Argentina, Paraguay, and Brazil. Instead of the expected, it was found that the essential oil of each species considered in this work exhibits a particular characteristic profile <![CDATA[<b>CRYSTAL STRUCTURE OF A NEW BISMUTH PERRHENATE Bi(Re0<sub>4</sub>)<sub>3</sub>H<sub>2</sub>0</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100008&lng=es&nrm=iso&tlng=es Monoaquatris(tetraoxorhenate (VII)) bismuth(III), Bi(Re0(4))3(H(2)0) was prepared by reaction of (BiO)2C0(3)/Bi2(C0(3))3 with concentrated HRe0(4) at room temperature. The pale yellow compound crystallize triclinic in the space group PI;, (No. 2); with two formula units per unit cell (a = 746.0(1) pm, b = 111. 1(2) pm, c = 990.5(2) pm, a = 100.99(3)°, p = 99.88(3)°, y = 100.17(3)° ). The main feature of the crystal structure is a distorted bicapped trigonal prism of Bi[(Re0(4))3;2 (Re0(4))2/2 (Re0(4))2/2 (H(2)0)], which are connected each other through [ReOJ-tetrahedra to form a three-dimensional network. In the titled compound, the cation Bi3+ is eightfold coordinated which agree with the tendency observed in other compounds of the family <![CDATA[<b>EFFECT OF CROSSLINKED CHITOSAN AS A CONSTRAINED VOLUME ON THE <i>IN VITRO </i>CALCIUM CARBONATE CRYSTALLIZATION</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100009&lng=es&nrm=iso&tlng=es The present work deals with the effect of the constrained volume given by crosslinked chitosan (CHI) as a sphere on the in vitro CaC0(3) crystallization. Crosslinked CHI was obtained with formaldehyde (FA), glutaraldehyde (GA), epichlorhydrine (EPCH) and poly (propylene glycol) diglycidyl ether (PPDGE) as crosslinking agents. Determination of swelling percentage (%) of the crosslinked CHI spheres was carried out in TRIS buffer at pH 9. Spheres of high molecular weight were prepared using drops of CHI solution on NaOH. In vitro CaC0(3) crystallization using gas-diffusion method was done. In addition, a synthetically sulphonated containing polymethylsiloxane (S-PMS) was used as modifying additive on the CaC0(3) crystals growth in a confined space of CHI. The degree of the crosslinking altered the diffusion of C0(2) gas through the CHI spheres during the CaC0(3) crystallization resulting in different and specific crystals morphologies <![CDATA[<b>ROLE OF THE LINKING OF METALLIC CENTERS TO MACROMOLECULAR AND OLIGOMERIC SYSTEMS IN THE PYROLYTIC PRODUCTS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100010&lng=es&nrm=iso&tlng=es Pyrolysis of the mixtures: [NP(0(2)C12H8)]n // AuCl(PPh2) system (I) [NP(O2C12H8)]0 8[NP(OC6H4CH2CN.{Ru])2]015 NP(OC6H5)10C6H4CH2CN. [Ru] 0.05]n // 'BuSiMe2Cl system (II) and N3P3[NH(CH2)3Si(OEt)3]6// N3P3[OC6H4CH2CN. TiCp2Cl]6(PF6)6 system (III) were studied in air and at 800 °C, and their products characterized. Nanostructured Au foams; Ru0(2) and Ti(P0(3))3 islands deposited on SiP(2)0(7) / P(4)0(7) matrix respectively were obtained. System (I) affords similar results to the pyrolysis of the polyphosphazene having the AuCl(PPh2) coordinated to the polymeric chain which can be attributed to a probable coordination of the Au fragments to the polymer during the heating process. In the system (II) the no presence of metallic nanostructures containing Si was attributed to the absence of Si ultraestructures due to the no cross-linking of the precursor by volatilization of the silicon molecular compound. In the system (III) the ciclic trimer acts each one as template for the formation of mesostructured products remaining separated at the micro level <![CDATA[<b>STEROIDS FROM THE MARINE FUNGUS GEOTRICHUM SP</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100011&lng=es&nrm=iso&tlng=es Ergosterol 1, peroxyergosterol 2, ergosta-4,6,8(14), 22-tetraen-3-one 3 and 24-ethyl-cholesta-4-ene-3-one 4 were isolated from the cultures of a fungus Geotrichum sp. obtained from a marine sediment. It was established that no other sterols were present in the extract. Their structures were elucidated by spectroscopic methods <![CDATA[<b>THE STEREOSELECTIVE SYNTHESIS OF THE WERNER COMPLEX WITH SUBSTOICHIOMETRIC SUGARS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100012&lng=es&nrm=iso&tlng=es A tetranuclear complex of Co(III) with hydroxo bridges, so-called "Werner Complex", was synthesized in the presence of several sugars (1-8) with partial resolution of this complex. The sugars in 10 mol % with respect to Co(III) induce maximum resolution of the Werner complex <![CDATA[<b>A THEORETICAL STRUCTURE-AFFINITY RELATIONSHIP STUDY OF SOME CANNABINOID DERIVATIVES</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100013&lng=es&nrm=iso&tlng=es A ZINDO/1 quantum-chemical structure-affinity relationship study with the KPG model is presented for the in vitro interaction of a group of classical, indole-derived and aminoalkylindole-derived cannabinoids with CB and CB2 receptors. From this work the following conclusions are obtained. CB and CB2 CB2 receptor affinities are regulated by different mechanisms involving orbital and charge control. Nevertheless CB and CB2 classical ligands share three common features: a hydrogen bond to a lysine (for CB ) or serine (for CB), a fully aromatic ring and a branched carbon side chain. In the case of indole-derived and aminoalkylindole-derived cannabinoids orientation and alignment rules have been defined as a basis for the comparison of noncongeneric molecules. In this way it was possible to associate the location of molecular fragments of these systems with known molecular systems such as classical cannabinoids. For aminoalkyhndoles we have proposed the locus with which they bind to a second receptor site that is available to WIN-55212-2 but not to classical cannabinoids. On the basis of our results we propose a new molecule that should help to discriminate between the above two receptor sites <![CDATA[<b>CONFORMATIONAL PREFERENCE IN 4,6-DIMETHYL-l,3-THIOXANE</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100014&lng=es&nrm=iso&tlng=es Trans-4,6-dimethyl-l,3-thioxane shows two conformations as a result of the heterocyclic ring inversion. The I and II conformers interconversion process has been studied by means of ab initio methods. The thermodynamics of this reaction calculated at the MP2/6-311+G**// HF/6-31G" and B3LYP/6-311+G"// B3LYP/6-31G" levels yield AG° values of ca. -1.5 kcal/mol in the gas phase, implying that II is the most important species in the gas phase and that its relative concentration is ca. 93%. In solution of low and medium polarity solvents, PCM method predicts an 85% concentration for this species, consistent with an 83% estimated from 'H-NMR spectra. The experimental NMR properties ( 8 and 'J C_H ) have not been reported since I and II separation could not be achieved. The results obtained for two long range "J2ax6e and 6J2e Je coupling constants of ca. 0.5 Hz are in good agreement with 0.41 Hz, calculated in the present work. The calculated chemical shifts for the C2 and C5 protons show that 8Heq < 8Hax implying that some anomalous effects are operating, though the 8 seems to be moderately insensitive C-H bond distances changes. The spin-spin coupling constants are much more sensitive to changes occurring in the ring. Thus, normal and reverse Perlin effects for 'J are predicted for C2 -H and C5-H are operating, respectively. The cC5 - Heq -> (7*C - S interaction would be the responsible for the very small elongation of the C5 - Heq over the C5 - Hax bond distances <![CDATA[<b>A MODEL FOR CALCULATING THE DENSITY OF AQUEOUS MULTICOMPONENT ELECTROLYTE SOLUTIONS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100015&lng=es&nrm=iso&tlng=es A method is presented for calculating the densities of simple and multicomponent aqueous saline solutions. A total of 38 parameters were obtained for anions and cations which allowed predicting their density in aqueous solution. The proposed method is based on the model of Hórsak and Slama¹ applicable to simple 1:1 aqueous electrolyte solutions which in the present study was extended to multicomponent systems and for any type of salt. Seventeen aqueous systems containing 2, 3, and 4 salts were studied, obtaining excellent results when compared with the experimental values. The total relative mean standard deviation obtained was 0.08 %. The proposed method used adjustable parameters, which are obtained beginning from experimental data from systems containing a single salt. Two parameters are required for each ion present in the aqueous solution <![CDATA[<b>DEGRADATION OF ACRYLIC ACID-GRAFTED CELLULOSE IN AQUEOUS MEDIUM WITH RADICAL INITIATORS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100016&lng=es&nrm=iso&tlng=es The chemical modification of cellulose by grafting reaction with Acrylic Acid (AA) considering different reaction factors was investigated. Natural polymers such as Santa Fe Cellulose, Microcrystalline Cellulose (Avicell) and Secondary Pulp were studied as substrates. pH effect; Ce (IV), Mn(VII) and Fenton as initiators; time and temperature polymerization were investigated. Grafting reachs a maximum, 90 % graft, at pH 7. A medium to weak C=0 band at 1715 cm"¹ for carboxylic group in FTIR spectroscopy is presented. Santa Fe and Avicel cellulose grafted whith AA at 17 hours are degraded. Secondary pulp with Fenton at 50-60 and 70 °C at 17 hours are degraded too. The degradation of polymers at long reaction times at 17 hours and 70°C were analized by FTIR spectroscopy and electronic microscopy analysis (SEM). <![CDATA[<b>CHARACTERIZATION OF MFI ZEOLITE MEMBRANES BY MEANS OF PERMEABILITY DETERMINATION OF NEAR CRITICAL AND SUPERCRITICAL C0<sub>2</sub></b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100017&lng=es&nrm=iso&tlng=es Zeolites are inorganic materials with intrinsic microporous properties. Basically they are aluminasilicates constituted from a three dimensional network of Si0(4) and A10(4) tetrahedra. This type of materials may have very interesting applications like adsorbents or molecular sieves. In this study, mass transfer properties of supported MFI zeolite membranes at high pressure are established using a new experimental methodology. The aim of this study was the analysis of the mass transfer of a compressed carbon dioxide through microporous zeolite membranes in order to characterize its structural parameters, identifying mass transfer mechanisms under high pressure conditions. This type of materials can be used like molecular sieves, since they present a crystalline structure with interstitial micropores of a mean pore diameter of 0.55 nm. For this purpose, we studied the mass transfer of high pressure C0(2) through microporous MFI zeolite membranes using a new experimental methodology in order to determine the permeance of carbon dioxide using an original apparatus operating in transient state. Carbon dioxide is used in experiments taking into account several applications reported in the literature coupling recovery or separation of this compound from gaseous solutions with inorganic molecular sieves. Values of flux (mol m"² s"¹) and permeance (mol m"² s"¹ Pa"¹) have been obtained experimentally. This new experimental device allows estimating permeance values between 3.59,10"' and 7.51,10"' mol m"² s"¹ Pa"¹) when the values of feed pressure are ranged between 3 and 14 MPa and the temperature varies between 25 and 100°C. These values are coherent with the microscopic nature of pores, showing that the zeolite layer deposed on the macroporous support was synthesized without macroporous defaults. An activated diffusion through the micropores might be identified in the gas phase, but under supercritical conditions (P > P , T > T) an irreversible modification of transport properties was observed. This behavior was explained by a limited mechanical resistance of the membrane at high pressure conditions. In supercritical conditions, mass transfer could be controlled by a combination of diffusion through mesoscopic and microscopic porosity <![CDATA[<b>EPICUTICULAR COMPONENTS FROM PSEUDOGNAPHALIUM ROBUSTUM (ASTERACEAE)</b>: <b>CHEMOSYSTEMATIC CONSIDERATIONS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100018&lng=es&nrm=iso&tlng=es Surface compounds were obtained by a methylene chloride extraction of fresh aerial parts of Pseudognaphalium robustum. The methylene chloride extract was fractionated by CC and the fractions were analyzed by GC-MS. Since flavonoids and terpenes are present only in small amounts in the epicuticular exúdate of P. robustum, 80% of the surface compounds actually correspond to a complex mixture of saturated fatty acid esters, unsaturated fatty acid esters, alcohols, aldehydes, fatty acids, alkenes, triglycerides and monoglycerides. A minor hydrocarbon fraction of n-alkanes from C23 to C37 was also identified. On the contrary, in P. vira vira, P. cheiranthifolium, and P. heterotrichium, the epicuticular extracts contain from 70% to 80% of a mixture of diterpenoids and n-alkanes. These results show a remarkable distance between P. robustum and other species of the genus, which share the same ecosystem, when the whole pool of epicuticular compounds is taken into account. Also, these considerable differences in chemical composition are in agreement with authors that consider Pseudognaphalium as a heterogeneous taxonomic group <![CDATA[<b>SYNTHESIS AND DETERMINATION OF THE PROPERTIES OF THE BIFUNCTIONAL BETA ZEOLITE CATALYSTS FOR N-HEPTANE HYDROISOMERIZATION</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100019&lng=es&nrm=iso&tlng=es In this study, two types of beta zeolites with different Si/Al ratios (11.7 and 24.5) were synthesized hydrothermally using tetraethylammonium hydroxide (TEAOH) as the template. Different amounts of Platinum (0.2%, 0.5% and 1.2%) were loaded on the protonated form of zeolite by incipient wet impregnation method with hexachloroplatinic acid in 0.2N Cl" progressive ion solutions. Catalytic reactions were carried out at atmospheric pressure in a fixed bed reactor with vertical placing and downward flow at three different temperatures, various WHS V (weight hourly space velocity) and n-H2/n-HC (molar hydrogen / hydrocarbon) ratio (230, 250, 280 °C, 1.64, 2.48, 3.28 hr¹ and 6, 10, 14 respectively). Increasing the Si/Al ratio from 11.7 to 24.5 promoted the selectivity and yield. It was found that optimum platinum content depends on the Si/Al ratio (zeolite acidity) present in the zeolite catalyst. The monobranched to dibranched isomers ratio were correlated with a linear function of n-heptane conversion. Such a correlation was found to be valid for various Si/Al ratios, metal content, processing temperature and pressure, WHSV and hydrogen to hydrocarbon ratio. This observation may indicate that in isomerization reactions, the mono-branched isomers are first produced but subsequently transformed into multi-branched isomers <![CDATA[<b>SEPARATION AND DETERMINATION OF SIX METAL CATIONS BY CAPILLARY ZONE ELECTROPHORESIS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100020&lng=es&nrm=iso&tlng=es A rapid, simple and reliable method was devised for separation and determination of six metal cations, based on the capillary zone electrophoresis. The results showed that the complete separation of K+,Cu2+, Zn2+, Mn2+, Pb2+and Cd2+canbe achieved within 5 min. Anew electrolyte system containing 15 mmol-L"¹ imidazole as a background absorbance reference and 8 mmol-L"¹ malonic acid, 2 mmol-L-1 18-crown-6 ether as the complexing agents, 10%methanol as anorganic modifier, by using acetic acid to adjust the pH=4.40 was developed. The applied voltage was 20 kV at 25 °C. Under the optimum conditions, 6 ions were separated and determined with the correlation coefficient of 0.9984-0.9993. The detection limits (S/N=3) from 0.05 (K+)to 0.75 (Zn^mg-L¹. The repeatability of migration times was less than 0.60% and of peak area ranged from 3.4 to 5.6% (n=6). The results were compared with AAS for analyzing the real samples of waste-water and snow water <![CDATA[<b>METAL CONTAMINATIONS IN FIVE FISH SPECIES FROM BLACK, MARMARA, AEGEAN AND MEDITERRANEAN SEAS, TURKEY</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100021&lng=es&nrm=iso&tlng=es The concentrations of cadmium, copper, chromium, copper, iron, manganese, nickel, zinc and lead in muscle and liver tissues of the fish samples collected from seven stations in the coastal waters of Turkey and were determined. Iron showed the highest levels in both tissues offish and all stations. Following Fe; Zn generally showed the second highest levels. Metal concentrations in edible parts offish species were 0.02-0.30 mg kg"' for cadmium, 0.04-0.26 mg kg"' for cobalt, 0.07-1.19 mgkg"' for chromium, 0.34-16.7 mgkg"' for copper, 18.5-72.3 mgkg"' for iron, 0.07-2.58 mgkg"' for manganese, 0.01-2.78 mgkg"'for nickel, 0.04-1.34 mg kg"' for lead, 3.36-42.6 mg kg"' for zinc respectively. In general, metal concentrations in livers were higher than those in muscles. Cadmium, chromium and lead concentrations in muscles offish from some stations were higher than permissible safety levels for human uses. <![CDATA[<b>STUDY OF THE EFFECT OF TEMPERATURE ON THE HARDNESS, GRAIN SIZE, AND YIELD IN ELECTRODEPOSITION OF CHROMIUM ON 1045 STEEL</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100022&lng=es&nrm=iso&tlng=es A study was made on the effect of temperature on the electrodeposition of hard chromium on 1045 steel within a range of 30° to 60°C, as shown by variations in reaction yield, surface hardness, and depositional grain size. Increase in temperature produced a decrease in faradic yield of the reaction of between 17% and 9%, an increase in hardness from 550 to 700 Brinelli, and a decrease in deposited chromium grain size from 278 to 32.4 urn. The most notable effect of temperature difference was observed between 30° and 40°C. Chrono-potentiometric and potentiodinamic linear sweep were measured at 30°C, 40°C and 50 °C in an attempt to explain this behavior. The results obtained suggested the formation of a compact film typical of a nucleation process in chromium electrodeposition. An increase in temperature affects the formation of this film, decreasing its thickness and distributing it in a more homogeneous manner over the steel, as shown by a decrease in the grain size of the chrome deposited <![CDATA[<b>EFFECT OF HUMIDITY IN ETHYL CELLULOSE (EC) THERMELECTRET</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100023&lng=es&nrm=iso&tlng=es The ethyl cellulose samples of thickness 30 urn were prepared using solution grown method. The samples were polarized by means of thermal polarization for preparation of thermoelectret. The charge storage stability and the transport of detrapped charges in the EC thermoelectre were investigated by surface potential decay and open-circuit thermally stimulated discharge current (TSDC) analysis. The mean penetration depth for EC at different environment humidity and polarizing temperature were calculated. The results indicated that the charge stability of EC was significantly affected by relative humidity <![CDATA[<b>IN VITRO SENSITIVITY OF <i>BOTRYTIS CINÉREA </i>TO RESINOUS EXUDATES OF <i>HELIOTROPIUM FILIFOLIUM</i>AND GERANYL DERIVATIVES COMPOUNDS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100024&lng=es&nrm=iso&tlng=es The activity of the extract ofHeliotropium filifolium, of the natural compounds obtained from its resinous exudates, filifolinol and fihfohnyl senecionate, and of the synthetic derivative of filifolinol, filifolinoic acid, on the mycehal growth of the phytopathogenic fungus Botrytis cinérea was analyzed in liquid and solid media. The extract of H'. filifolium, filifolinol, and filifolinoic acid reduced mycehal growth of this fungus. The effect of these compounds was dose-dependant. The compound fihfohnyl senecionate was inactive in all the tested conditions. The extract of H'. filifolium and filifolinol retarded the germination of conidia of the fungus <![CDATA[<b>DNA CLEAVAGE AND ANTIMICROBIAL ACTIVITY STUDIES ON TRANSITION METAL(II) COMPLEXES OF 4-AMINOANTIPYRINE DERIVATIVE</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100025&lng=es&nrm=iso&tlng=es Anew series of transition metal complexes of Cu(II), Ni(II), Co(II) and Zn(II) have been synthesized from the Schiff base (L) derived from 4-aminoantipyrine, salicylaldehyde and o-phenylenediamine. The structural features have been arrived from their elemental analyses, magnetic susceptibility, molar conductivity, FAB-mass, IR, UV-Vis., 'H NMR and ESR spectral studies. The data show that the complexes have composition of ML type. The UV-Vis., magnetic susceptibility and ESR spectral data of the complexes suggest a square-planar geometry around the central metal ion. The antimicrobial activities of the metal chelates against the bacteria Salmonella typhi, Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli and fungi Aspergillus niger, Aspergillus flavus and Rhizoctonia bataicola have been carried out. A comparative study of MIC values of the Schiff base and its metal complexes indicates that the metal complexes exhibit higher antibacterial activity than the free ligand. The nuclease activity of the above metal complexes shows only the copper complex cleaves DNA <![CDATA[<b>EFFECTS OF ESSENTIAL OILS FROM FIVE PLANT SPECIES AGAINST THE GRANARY WEEVILS <i>SITOPHILUS ZEAMAIS </i>AND <i>ACANTHOSCELIDES OBTECTUS </i>(COLEÓPTERA)</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100026&lng=es&nrm=iso&tlng=es Essential oils obtained from Gomortega keule, Laurelia sempervirens, Origanum vulgare, Eucalyptus globulus, and Thymus vulgaris were analyzed by gas chromatography and gas chromatography-mass spectrometry and evaluated for their toxicity against adults of Sitophilus zeamais (Motschulky) and Acanthoscelides obtectus (Say) (Coleóptera). Contact toxicity was assayed by impregnating filter paper discs with the oils. The amount of essential oils applied in each desiccator (4 1 capacity) was 4, 8, 16, or 32 ul, corresponding to 1, 2, 4, or 8 fj.1/1 air. The results showed significant differences between the tested dosages and exposure periods of the essential oils. Although desirable insecticidal activities against A obtectus were achieved with the essential oils of all five plants, the oils from G. keule and L. sempervirens were the most effective at 96 h. On the other hand, the essential oils of E. globulus and T. vulgaris were most effective against S. zeamais. In all plant species, higher doses or longer exposure periods were more effective against both insects. No mortality was observed in the control group (acetone only) of each species. Therefore, these results suggest that essential oils from the studied plants may be used against insect pests in grain storage <![CDATA[<b>HYDRATION AND ACETYLATION OF LIMONENE</b>: <b>SUPPORTED HETEROPOLYACIDS</b>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0717-97072008000100027&lng=es&nrm=iso&tlng=es The limonene hydration and acetylation in liquid phase catalyzed by phosphotungstic and phosphomolybdic acid bulk and supported on silica and titanium dioxide were studied. The reaction was performed in a batch reactor in acetic acid at 40°C, with magnetic stirring of the reaction mixture. Reaction products were analyzed by gaseous chromatography with FID detector using a capillary column for separation of products. The identification of compounds was made with pattern terpenes and by gaseous chromatography with mass spectrometry. All catalysts tested result to be active in the hydration and acetylation reaction of limonene. Catalysts based on phophotungstic acid (HPW) produce larger amount of hydration and acetylation products than phosphomolybdic acid (HPMo) catalyst. Hydration products increase faster than isomerization products when the reaction time is increased. The structure of heteropolyacids and the presence of acid sites Bronsted and Lewis were determined by FTIR