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Organic Carbon Determination by the Walkley-Black and Dry Combustion Methods in SurfaceSoils and Andept Profiles from Costa Rica
(1979-01)
The efficiency of oxidation of organic C by the Walkley-Black method was studied by comparing with determinations using dry combustion equipment and gravimetric determination for the evolved CO2. Fifty surface soils (0-30 ...
Fate of buturon-14C in soil during seven seasons of exposure under outdoor conditions
(1984-03)
Buturon (ring 14C) was applied to wheat and soil in two successive years (3 kg/ha each year) at outdoor conditions. Residual radioactive substances in the upper soil layer (0-10-cm depth) were measured 1.5, 2.5, 3.5, 6.0, ...
Reacciones del 2,2´-Tio-benzimidazol con Sulfato de Dimetilo
(1979)
Se efectuó la reacción del 2,2´-tiobis-benzimidazol con el sulfato de dimetilo por pasos. Se comprobó la formación de: 1,1´-dimetil-2,2´-tiobis-benzimidazol (2) y del diperclorato del 1,1´,3,3´-tetrametil-2,2´-tiobisbenz ...
Paraquat Behavior in Costa Rican Soils and Residues in Coffee
(1990)
The paraquat deactivation capacities of soils, from 20 coffee plantations, generally ranged from 100 to 500 mg of paraquat/kg of soil. Even when paraquat had been applied up to twice per year (1.2 kg ha-1 year) for 20 ...
Residuos, sorción y desorción del herbicida paraquat en suelos tropicales
(1987-11-24)
Se analizaron por espectrofotometría residuos del herbicida Paraquat en muestras de suelos tropicales de Costa Rica dedicados al cultivo del café y donde el Paraquat es aplicado desde hace alrededor de 20 años, una o dos ...
Reactive Intermediates in the Photolysis of Furan, Thiophene and Pyrrole: The Dewar and the Ring Contraction forms
(1985-07-14)
Five-member aromatic heterocycles have been known to undergo scrambling of the ring atoms upon photolysis. These reactions are characterized by their selectivity and several mechanisms have been proposed involving the ...
Studies of methamidophos-C-14 in Costa Rican vegetables and soils
(1984)
In order to see the effect of time lapse between the last application of methamidophos and harvesting insecticide was applied on lettuce plants (6,84 μCi in one experiment and 4,03 μCi in the other experiment). Analysis ...
La estructura de la Diacetonafenantrenoquinona
(1971)
The substance, diacetonephenanthrenequinone, long believed to have structure I or II, is found to have structure IV according to modern spectroscopic methods and chemical behavior.
Constituents of Fevillea cordifolia: New Norcucurbitacin and Cucurbitacin Glycosides
(1993)
The seeds of Fevillea cordifolta have yielded 11 new fevicordin-type 29- norcucurbitacins 3-13, and two new cucurbitacin glycosides 14 and 15, which were isolated along with previous reported fevicordin A [2] and its ...
Análisis de residuos de plomo en repollo de Costa Rica
(1984)
Lead residues analysis in cabbage. Cabbage and soil samples from the main cabbage growing areas of Costa Rica were analyzed for lead residues. Lead residues result from the use of lead arseniate as an insecticide and ...