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    • Keywords


      Hydrothermal equilibria; lanthanide carbonates; basic carbonates; thulium

    • Abstract


      Isobaric phase equilibria in Er2O3−H2O−CO2 and Tm2O3−H2O−CO2 systems have been determined at 650 and 1300 bars and temperature range of 100–800°C. The equilibria depend on the mole fraction of CO2 in the coexisting fluid. The stable phases: Ln(OH)3, Ln2(CO3)33H2O, Ln(OH)CO3-orthorhombic, Ln2O2CO3-hexagonal, LnOOH and Ln2O3-cubic are common to both the systems. Additional phases observed in the thulium system are Tm2O(OH)2CO3 and Tm6(OH)4(CO3)7. Two other phases isolated are Tm6O2(OH)8(CO3)3 and Tm4(OH)6(CO3)3 which are stabilised only in the presence of alkali impurities. Stability field of Ln(OH)3 is limited to$$X_{CO_2 }< 0 \cdot 01$$.Tm(OH)CO3 does not stabilise at low$$X_{CO_2 } $$; therefore TmOOH coexists with all the phases other than Tm6(OH)4(CO3)7. When$$X_{CO_2 } = 1$$, the stable phases are Tm2O2CO3 and Tm2O3 in the order of increasing temperature. The normal carbonate, Tm2(CO3)3·8H2O has no stability at higher pressures.

    • Author Affiliations


      Iftiqhar Mohamed1 J A K Tareen1 T R N Kutty2

      1. Mineralogical Institute, University of Mysore, Manasa Gangotri, Mysore - 570 006, India
      2. Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore - 560 012, India
    • Dates

  • Journal of Chemical Sciences | News

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