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  • 1
    Electronic Resource
    Electronic Resource
    Structure of lithium sodium yttrium silicate Na2LiYSi6O15 (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 38 (1982), S. 1405-1408 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740882006037
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  • 2
    Electronic Resource
    Electronic Resource
    Structure of the oxyapatite NaY9(SiO4)6O2 (1982)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 38 (1982), S. 1564-1566 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0567740882006396
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  • 3
    Electronic Resource
    Electronic Resource
    Long fallow periods: The key to sustenance of soil fertility? (1991)
    Springer
    Plant and soil 135 (1991), S. 297-302 
    Details
    ISSN: 1573-5036
    Keywords: fallow period ; soil nutrients ; traditional agriculture ; wetland rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Changes in N, P, K, Ca and Mg in soil and rice plants were investigated during a cropping season following a long fallow period in a system of traditional cultivation practised for several centuries, under a village tank irrigation system. Soil, N, P, K, Ca and Mg were not found to be deficient for rice production throughout the season. Flooding did not produce toxic levels of Fe and Na and soil pH remained at 6.4 during the season. The average grain yield (3.5 t/ha) without any addition of chemical fertilizer was almost the same as that from fields under major irrigation systems where fertilizer application (less than the recommended level) was common. The sustainability of soil fertility under the traditional system of rice cultivation appears to be dependent upon long fallow periods. The natural build-up of soil fertility during a three-year fallow was evidently adequate to support a good growth of the crop which produced a yield comparable to that obtained in chemically fertilized, more intensively cropped rice fields under major irrigation systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010920
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  • 4
    Electronic Resource
    Electronic Resource
    Reaction of chlorapatite, Ca5(PO4)3(Cl, F) with sodium carbonate and silica (1979)
    Springer
    Journal of materials science 14 (1979), S. 2797-2810 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The conversion of insoluble phosphorous minerals such as apatite, Ca5(PO4)3(F, OH, Cl), to phases containing phosphorous in soluble form is an essential step in the production of fertilizer grade phosphates. Developing countries lack the capital-intensive industrial base necessary to create a phosphate industry. We examine a process suitable for use in Sri Lanka which uses mainly indigenous raw materials. In this process, a chlorine-rich apatite is fused with Na2CO3 and SiO2 at 900° C and 1300° C for 1 to 2 h to yield a product having 〉90% available phosphorous. Data necessary for the technological evaluation of the process are presented. Phase equilibria in the lime-rich portions of the system CaO-Na2O-P2O5-SiO2 have been studied. The section Ca3(PO4)2-Ca2SiO4-CaNaPO4 is shown to be a ternary system, and phase relations on the 1100° and 1300° C isothermal sections are presented. A reconnaisance of the system CaO-Ca3(PO4)2-Ca2SiO4-CaNaPO4 has been made. These data, combined with studies of the kinetics of the reaction, point to regions of composition and reaction conditions favouring high yields of available phosphorous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611458
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  • 5
    Electronic Resource
    Electronic Resource
    Crystal chemistry and synthesis of Ternary Silicates and Germanates containing alkali (Na+, K+) and alkaline earth (Ca2+, Sr2+, Ba2+) cations (1975)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 411 (1975), S. 163-172 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Darstellung und Kristallchemie der ternären Silicate und Germanate mit Alkali (Na+, K+)- und Erdalkali (Ca2+, Sr2+, Ba2+)-KationenDie Darstellung von neuen ternären Silicat- und Germanat-Phasen mit großen Alkali- und Erdalkalikationen wird beschrieben. Sie wurden durch Festkörperreaktion von Mischungen der Carbonate bzw. Oxalate mit SiO2 bzw. GeO2 oder durch Schmelzen und anschließende Rekristallisation des Glases erhalten.Vertreter der kubischen M4+M2+X3O9-Familie sind Na4CaSi3O9 und die isostrukturellen Verbindungen K4CaGe3O9, K4SrGe3O9, K4CaSi3O9 und K4SrSi3O9. K4BaSi3O9 ist pseudokubisch; die Symmetrie des Na4SrSi3O9 ist unbekannt. Zur rhomboedrischen M8+M2+X10O25-Familie gehören K8CaSi10O25, K8SrSi10O25 und K8BaSi10O25.Na2CaGe2O6 und Na2SrGe2O6 sind isostrukturell, aber strukturell nicht mit Na2BaSi2O6 verwandt. Na2Ba2Ge2O7 und Na2Ba2Si2O7 sind strukturell ähnlich.
    Notes: The synthesis of new ternary silicate and germanate phases containing large alkali and alkaline-earth cations is described. They are made by solid-state reaction of mixtures of carbonates or oxalates with SiO2 or GeO2, or by fusion and subsequent recrystallization of the glass.Representatives of the cubic M4+M2+X3O9 family include Na4CaSi3O9 and the isostructural compounds K4CaGe3O9, K4SrGe3O9 and K4SrSi3O9. K4BaSi3O9 is pseudocubic: the symmetry of Na4SrSi3O9 is unknown. The rhombohedral M8+M2+X10O25 family includes K8CaSi10O25, K8SrSi10O25 and K8BaSi10O25.Na2CaGe2O6 and Na2SrGe2O6 are isostructural but both are structurally unrelated to Na2BaSi2O6. Na2Ba2Ge2O7 and Na2Ba2Si2O7 are structurally similar.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19754110211
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  • 6
    Electronic Resource
    Electronic Resource
    Studies on Clathrasils. X. The effect of “help gases” on the formation and stability of clathrasils (1987)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 546 (1987), S. 189-198 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Untersuchungen an Clathrasilen. X. Der Einfluß von Hilfsgasen auf die Bildung und Stabilität von ClathrasilenEs wurden Vertreter jeder der bisher bekannten Clathrasil-Familien unter Hydrothermalbedingungen aus wäßrigen Kieselsäure-Lösungen in Gegenwart ihrer charakteristischen Gastmoleküle und unter Ausschluß von Luft synthetisiert. Die kleinen Käfige im Tetraedergerüst dieser Produkte sind leer, während sie bei Synthesen in Anwesenheit von Luft mit Stickstoff gefüllt sind. Außer den Clathrasilen wurde Silica-ZSM-48 erhalten, wenn unter Luftausschluß Pyrrolidin als Gastmolekül verwendet wurde. Es zeigt sich, daß die kleinen Moleküle von „Hilfsgasen“ wie Stickstoff nur einen geringen Einfluß auf die Stabilisierung der Clathrasil-Gerüste haben. Dies steht im Gegensatz zur Bedeutung von „Hilfsgasen“ für die Stabilisierung einiger Clathrathydrate. Die Bildungsgeschwindigkeit von Clathrasilen bei Synthesen in Gegenwart und unter Ausschluß von Luft werden miteinander verglichen.
    Notes: Members of all known clathrasil families have been synthesized from aqueous silica solutions under hydrothermal conditions in the presence of their characteristic guest molecules and in the absence of atmospheric gases. The small cages of the products, otherwise filled with nitrogen, were found to be empty. In addition to clathrasils, silica-ZSM-48 was obtained as a reaction product in the absence of atmospheric gases and pyrrolidine as the guest. It appears that small “help gas” molecules such as nitrogen play only a minor role in the stability of clathrasil frameworks unlike in the case of some clathrate hydrates. A comparison of rates of formation of clathrasils synthesized in air and in the absence of “help gases” is also presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19875460321
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