GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
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Volume 3, Issue 4
Displaying 1-3 of 3 articles from this issue
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  • A possible process for the fluctuation of halogen abundances in fumarolic gases
    Fumihiro Honda
    1970 Volume 3 Issue 4 Pages 187-200
    Published: 1970
    Released on J-STAGE: April 08, 2008
    DOIhttps://doi.org/10.2343/geochemj.3.187
    JOURNAL FREE ACCESS
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    Volcanic gases from Nasudake volcano were analyzed for chlorine, bromine and iodine. It was found that low temperature gases with high chlorine content had lower Br/Cl and I/Cl ratios than did high temperature gases. To explain this finding, mixing processes of two kinds of gases are proposed. They are the original fumarolic gases of Nasudake volcano and the secondary fumarolic gases. The latter is assumed to be high in chlorine content and low in Br/Cl and I/Cl ratios. The experimental results on the distillation of a mixture of hydrochloric acid, hydrobromic acid and hydriodic acid solutions suggested that the hydrogen chloride in the secondary fumarolic gases may be supplied by distillation from the halogen compounds accumulated through the preceding fumarolic activity.
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  • Geochemical study of iodine in volcanic gases. II. Behavior of iodine in volcanic gases.
    Fumihiro Honda
    1970 Volume 3 Issue 4 Pages 201-211
    Published: 1970
    Released on J-STAGE: April 08, 2008
    DOIhttps://doi.org/10.2343/geochemj.3.201
    JOURNAL FREE ACCESS
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    The predominant chemical species of iodine in volcanic gases is suggested to be hydrogen iodide by thermodynamical calculations on the reactions, 2HI + 1/2 O2 = H2O + I2, 2HI = H2 + I2 and SO2 + 6HI = H2S + 3I2 + 2H2O. Thermodynamical calculations were also made to explain the difference in I/Cl ratio between volcanic halide sublimates and the fumarolic gases from which the sublimates were formed. It is suggested that the partial pressure of hydrogen iodide in volcanic gases is not enough to form sodium iodide through fumarolic alteration of wall rocks, while that of hydrogen chloride is enough to form sodium chloride. Another possible factor controlling iodine content of volcanic halide sublimates is air oxidation of iodide to free iodine gas under fumarolic conditions near outlets of fumaroles.
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  • Influence of CO2 on silica in solution
    Ghansityam D. Sharma
    1970 Volume 3 Issue 4 Pages 213-223
    Published: 1970
    Released on J-STAGE: April 08, 2008
    DOIhttps://doi.org/10.2343/geochemj.3.213
    JOURNAL FREE ACCESS
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    Laboratory experiments show that H4SiO4 (monomeric silica) up to 80ppm in seawater is stable under all CO2 pressures from 0 to 17.2 × 103 kg/m2. CaCO3, AlCl3·6H2O, MgCl2, and standard clays, when added individually, did not remove silica from solutions containing silica from 50 to 80ppm under these CO2 pressures. Addition of CaCO3 and AlCl3·6H2O together, however, removed silica from solution in inverse proportion to the CO2 pressure. CO2 serves to inhibit the removal of silica from solution containing CaCO3 and aluminum chloride. The CaCO3 functions as a buffer to maintain the acid to neutral pH. The final reaction appears to follow: 2H4SiO4 + Al3++ 2CaCO3 + H2O = AISi2O5(OH)·4H2O + 2Ca2+ + HCO3- + CO2. In an open system, where CO2 can escape to the atmosphere, the removal of silica from solution is controlled by the available AlCl3·6H2O and CaCO3. Electron microscopy and infrared analyses confirm that the principal precipitates were clayey sediments and trace amounts of sepiolite. This suggests an intimate interrelationship between the geochemical cycles of carbon dioxide, calcium carbonate, aluminum, and silica in nature.
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