| Author (s): |
IONESCU, Lavinel G.
|
| Title: |
ANTONIO DE ULLOA, DISCOVERER OF PLATINUM |
| Abstract: |
Don Antonio de Ulloa, a member of a distinguished Spanish family, was born in 1716 and died in 1795. He studied physics and mathematics and was a member of many scientific societies, including the Academy of Sciences of Paris and the Royal Society of London. He traveled widely in Europe and the Americas and occupied many important positions, including those of Frigate Captain, Commander of the Royal Squadron of the Spanish Armada, Goverment of Huancavelica -Peru, Louisiana, and Florida. In l735, while a member of a scientific expedition sent by the Spanish and French governments to South America to measure a degree of meridian in Quito, close to the equator, he discovered platinum in the mines of Lavadero or wash gold in the district of Choco.
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| Keywords: |
Don Antonio de Ulloa.
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| Year: |
1998
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| Initial page: |
1
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| Final page: |
6
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.4_1998_2.pdf |
|
|
| Author (s): |
Jorge Nozaki; Edivaldo Egea Garcia; Joji Suguita
|
| Title: |
ADSORPTION OF GASEOUS SUBSTANCES ON CHEMICAL AND ELECTROLYTIC MANGANESE DIOXIDE |
| Abstract: |
The adsorption of mercury, arsine, hydrocyanic acid, and hydrogen sulfide on amorphous chemical manganese dioxide (CMD) and electrolytic manganese dioxide (EMD) has been investigated. Variables such as agitation time, pH, temperature, mass of adsorbent, and concentration of adsorbate were studied. The adsorption process obeys a Freundlich type isotherm over the concentration range investigated. Wads of Lujfa cylindrica Roem were used as substrate for CMD production. For gaseous substances, this amorphous material showed better sorption capacity than EMD.
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| Keywords: |
manganese dioxide, pollutants, adsorption, isotherms .
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| Year: |
1998
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| Initial page: |
7
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| Final page: |
15
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.10_1998_2.pdf |
|
|
| Author (s): |
Maria NEGOIU; Tudor ROSU; Liliana STOICESCU; Viorel CARCU; Mihai CONTINEANU
|
| Title: |
SOME COMPLEXES OF COPPER(II) WITH N,N-DISUBSTITUTED DITHIOOXAMIDES DERIVED FROM α-AMINOACIDS AND α-AMINOACID ESTERS |
| Abstract: |
The binuclear copper(II) complexes Cu2(L-4H)(H2O)2 (L = N,N -bis (carboxymethyl) dithiooxamide -GlyDTO and N,N-bis(1-carboxyethyl) dithiooxamide -AlaDTO) and Cu2(L-2H)Cl2 (L =methyl or ethyl ester of L) were synthesized. The structure of the complexes were studied employing IR, electronic and ESR spectroscopy and conductivity measurements. The IR data indicate that the ligands act as bistridentates, with N, S, 0 -coordination to the copper(II) ion.
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| Keywords: |
ethanedithioamides, copper(II) complexes, ESR spectroscopy, square planar complexes. .
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| Year: |
1998
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| Initial page: |
17
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| Final page: |
25
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.19_1998_2.pdf |
|
|
| Author (s): |
Eurica, M. Nogami; Gracinda, M. Dalmeida and Jorge Nozaki
|
| Title: |
DIFFERENTIAL PULSE POLAROGRAPHIC DETERMINATION OF ARSENIC IN BITUMINOUS COAL |
| Abstract: |
Differential pulse polarography was employed for the determination of arsenic in bituminous coal from Figueiras, Parana, Brazil. The dried coal sample was crushed to -100 mesh, ashed, and treated with reducing reagents in acidic media. The arsine generated was collected and selectively oxidized to Al +3 using an absorbing solution of 0.1 mol.L -1 [tris(hydroxymethyl) aminomethane] ( TRIS) and 0. 002 mol.L -1 silver nitrate. A solution of TRIS and hydrochloric acid, pH -1, was used as supporting electrolyte for differential pulse polarographic determination of Al+3 in the concentration range 0.05 -0.60 μglmL. The average arsenic concentration found was 69.0 ± 2.6 mg.kg -1 and was in agreement with the spectrophotometric method using silver-diethyldithiocarbamate-pyridine.
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| Keywords: |
arsenic, bituminous coal, differential pulse polarography, spectrophotometry..
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| Year: |
1998
|
| Initial page: |
27
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| Final page: |
32
|
| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.28_1998_2.pdf |
|
|
| Author (s): |
Anca Nicolae; Daniela Gavriliu; Ovidiu Maior; Constantin Draghici
|
| Title: |
PHENOXATHIIN CHEMISTRY SYNTHESIS BASED ON 2-ω-BROMOACETYLPHENOXATHIIN |
| Abstract: |
Starting from 2-ω-bromoacetylphenoxathiin and using the Kornblum reaction, the corresponding glyoxal 2 was synthesized. This was used for the syntheses of the monoxime 3, dioxime 4, and quinoxalinyl 5 derivatives. By treatment with thiourea 4-(2-phenoxathiinyl)-2-aminothiazole hydrobromide 7 was obtained. Some new ammonium and phosphonium salts was also prepared. Chemical and spectral data supporting the structure of the newly synthesized compounds are also presented.
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| Keywords: |
Phenoxathiin, ammonium salts, thiazole, glyoxime. .
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| Year: |
1998
|
| Initial page: |
33
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| Final page: |
45
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| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.34_1998_2.pdf |
|
|
| Author (s): |
Anca Nicolae; Daniela Gavriliu; Ovidiu Maior
|
| Title: |
PHENOXATHIIN CHEMISTRY. NEW CARBONYL COMPOUNDS AND DERIVATIVES |
| Abstract: |
Starting with 2-acetylphenoxathiin , 2-ω-bromoacetylphenoxathiinyl-10, 10-dioxide 2 was obtained. By means of the Kornblum reaction the corresponding glyoxal 4 was synthesized. From compound 2, the aminothiazole 3 and the 1,4-diketone 7 were also obtained. By the reaction of 2-ω-bromoacetylphenoxathiin 8 and sodium acetylacetonate "one-pot" synthesis of 1,4-diketone 9 was performed. Compound 9 was converted to pyrrolophenoxathiin 11 and 1,4-diketone 7. Starting with the brominated derivative 8 the aminoketones 12 and 13 were obtained. The new compounds were characterized by spectral methods CH-and 13C-NMR, IR, MS).
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| Keywords: |
Phenoxathiin, 1,4-Diketones, Oximes, a-Bromo-ketones.
|
| Year: |
1998
|
| Initial page: |
47
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| Final page: |
57
|
| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.47_1998_2.pdf |
|
|
| Author (s): |
Petre Ionita; Marcela Rovinaru; Ovidiu Maior
|
| Title: |
THE PREPARATION AND SOME REACTION OF 2,2-DIPHENYL-1-(3,6-DINITR0-4-COUMARINYL) HYDRAZYL FREE RADICAL |
| Abstract: |
The new persistent 2,2-diphenyl-1-(3,6-dinitro-4-coumarinyl)hydrazyl free radical 4 was obtained by potassium permanganate or lead dioxide oxidation of the corresponding 2,2-diphenyl-1-(3,6-dinitro-4-coumarinyl)hydrazine 3; hydrazine 3 reacts with nitrous acid to give successively the 2-(p-nitrophenyl)-2-phenyl-1-(3,6-dinitro-4-coumarinyl) hydrazine 6 and 2,2-(p-nitrophenyl)-1-(3,6-dinitro-4-coumarinyl) hydrazine 7. Compound 6 results also from free radical 4 and sodium nitrite in the presence of 15-C-5 crown ether. The structure of new compounds was confirmed by means of TLC, UV-Vis, 1H-NMR, IR, and for the free radicals by the EPR spectra.
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| Keywords: |
Free Radicals, Nitro-Coumarins, Diphenylhydrazines, Crown ethers..
|
| Year: |
1998
|
| Initial page: |
59
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| Final page: |
66
|
| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.58_1998_2.pdf |
|
|
| Author (s): |
Lavinel G. Ionescu; Sonia M. Hickel Probst; Elizabeth F. de Souza
|
| Title: |
FORMATION OF MICELLES OF CETYL TRIMETHYLAMMONIUM BROMIDE IN WATER-GLYCEROL SOLUTIONS |
| Abstract: |
The micellization of cetyltrimethylammonium bromide (CTAB) in glycerol and aqueous solutions of glycerol was studied by means of surface tensiometry. The critical micellar concentration (CMC) was determined at 25 °C and 40 Δ C, and thermodynamic parameters such as the free energy of micellization ΔG°mis, enthalpy ΔH and entropy ΔS of micellization were also measured At 40 °C, CTAB forms micelles in pure glycerol and in the entire range of water-glycerol solutions. For 25 °C, the CMC ranged from 9.2 x 10·4 Min pure water to 8.5 x 10·3M for solutions containing 90% glycerol by volume. The corresponding values obtained/or ΔG° were -4.14 and -2.82 kcal/mole; for ΔH° were -1.03 kcal/mole and -3.73 kcal/mole and for ΔS° were + 10.43 and -3.10 e. u. Addition of glycerol decreases the spontaneity of micelles formation of CTAB in water.
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| Keywords: |
Micellization, Cetyltrimethylammonium Bromide (CTAB), Critical Micellar Concentration, Glycerol, Water-Glycerol Solutions.
|
| Year: |
1998
|
| Initial page: |
67
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| Final page: |
76
|
| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.66_1998_2.pdf |
|
|
| Author (s): |
Catalina Pisoschi; Virgil Darie; Mihai Serban
|
| Title: |
STUDY OF RENAL SORBITOLDEHYDROGENASE IN EXPERIMENTAL DIABETIC NEPHROPATHY |
| Abstract: |
The link between the polyol pathway and the ocular complications of diabetes mellitus is explained by the excessive storage of sorbitol and the release of osmotic stress. The renal complications could also be explained by the osmotic hypothesis, but the polyol pathway activity is reduced in this case. The study of sorbitol dehydrogenase (SDH) activity, one of the enzymes involved in the catabolism of glucose by this pathway in renal and hepatic homogenates from diabetic animals, shows a constant increase of the hepatic enzyme activity compared to that at the renal level. The different variation of the renal SDH activity can be explained by the effect of hyperglycemia on the active form of the enzyme and its inactivation by nonenzymatic glycosylation
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| Keywords: |
alloxan, polyol pathway, sorbitoldehydrogenase, aldose reductase, nonenzymatic glycosylation..
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| Year: |
1998
|
| Initial page: |
77
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| Final page: |
82
|
| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.76_1998_2.pdf |
|
|
| Author (s): |
Adina Dumitrascu; Mircea Constantinescu; Corneliu Oniscu; Dan Cascaval
|
| Title: |
SYNTHESIS STUDY OF NEW 2-SUBSTITUTED IMIDAZOLINES WITH POTENTIAL HYPOTENSIVE ACTIVITY |
| Abstract: |
A theoretical study based on molecular mechanics and semi-empirical calculations of the condensation mechanism of methyl p-amidosulphonyl phenoxyacetate with ethylene diamine is reported. Synthesis of 17 new imidazolines derived from sulphonamidated phenoxyacetic acids is also described.
|
| Keywords: |
2-substituted imidazoline, sulphonamidated phenoxyacetic acid derivatives, hypotensive imidazolines.
|
| Year: |
1998
|
| Initial page: |
83
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| Final page: |
90
|
| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.82_1998_2.pdf |
|
|
| Author (s): |
Anca EMANDI
|
| Title: |
Synthesis and Characterization of New Oxovanadium(IV) Coordination Compounds with Pyrazol-5-one Azo Derivatives |
| Abstract: |
A new series of oxovanadium(IV) chelates containing bi-and tridentate pyrazol-5-one azo derivatives ligands of the type (I) [VO(L)2] and (2) [VO(L)(H2O)] have been prepared and characterized by elementary analysis, IR, electronic spectra, conductance measurements, and molecular weights. The ligands coordinate through (O-N) donor system as monobasic and bidentate (HL) for the first type and through (0-N-O) donor system as dibasic and tridentate (H2L) for the second type of complexes. The molecular weights, the presence of the (V=O) stretching band around 950 cm -1, and the visible spectra suggest a monomeric penta-coordinated structure for these complexes.
|
| Keywords: |
oxovanadium(IV) eoordination eompounds, pyrazol-5-one, azo dye, UV, IR speetroseopie .
|
| Year: |
1998
|
| Initial page: |
91
|
| Final page: |
99
|
| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.90_1998_2.pdf |
|
|
| Author (s): |
Petre Ionita
|
| Title: |
THE REACTION BETWEEN 2,2-DIPHENYL-1-PICRYLHYDRAZYL FREE STABLE RADICAL AND N-BROMOSUCCINIMIDE |
| Abstract: |
The reactions of 2,2-diphenyl-1-picrylhydrazyl (DPPH) or 2,2-diphenyl-1-picrylhidrazine (DPPH-H) with N-bromosuccinimide (NBS) were studied. Two main compounds Br-DPPH and (Br)2 DPPH were obtained, by bromination of the starting material in para-phenyl position, and also a secondary product, N02 DPPH. It was shown that the reactions of NBS with DPPH include a substitution at the picryl group of PPH with liberation in situ of N02 (ipso-substitution of a nitro group with bromine) and subsequently N02 is scavenged by DPPH with the foundation of N02 DPPH.
|
| Keywords: |
DPPH, free radical, bromination, ipso-substitution, scavengers .
|
| Year: |
1998
|
| Initial page: |
101
|
| Final page: |
106
|
| Link: |
Acessar |
| DOI: |
10.48141/SBJCHEM.v6.n7.1998.99_1998_2.pdf |
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