Magnetic field effect on fractionation of carbon isotopes in the reaction of Ca(OH)2 with air carbon dioxide

Abstract

213 The nuclear spin (magnetic) isotope effect was dis covered by A. L. Buchachenko and coworkers in 1976 [1]. In the first experiments, the isotope effect for sta ble carbon isotopes was studied in the photolysis of dibenzyl ketone, and further studies of the magnetic field effect on carbon isotope fractionation were car ried out using only organic substances [2]. In the present work, we revealed for the first time the magnetic field effect on the carbon isotope com position in the course of formation of an inorganic compound, calcite CaCO3. The experiments on studying the magnetic field effect on the carbon isotope fractionation during for mation of calcite were carried out by the following scheme. A natural calcium carbonate (limestone) and a reagent grade calcium carbonate were decom posed at 1000°C in an electric furnace to completely remove СО2 CaCO3 = CaO + CO2. The weight loss after the calcination was 42–43 wt %; the theoretical weight loss is 44 wt %. Calcium oxide obtained was mixed with water to form calcium hydroxide: CaO + H2O = Ca(OH)2. A thin layer of a water suspension of Са(ОН)2 was applied to a glass plate and kept in air for several weeks at room temperature, which resulted in the formation of calcium carbonate: Ca(OH)2 + CO2 = CaCO3. In all experiments, two plates with calcium hydroxide were used simultaneously. One of them was placed in the magnetic field, another, control one, was out of the field. The plates were disposed perpendicular to Earth’s magnetic field. The starting compounds had the following isotopic compositions (δ13C‰, PDB standard): –1.090 for the limestone, –42.805 for the reagent grade calcium car bonate, and from –7 to –10 for air carbon dioxide [3]. In the first run, the plate with Ca(OH)2 was placed in the field of a permanent magnet, which was located on the edge of the plate (Fig. 1). The isotopic compo sitions at different distances from the magnet were determined in 500 h. The δ13С values at distances equal to 0.5, 1, and 2 cm from the magnet were –22, ⎯26, and –27‰, respectively. The isotopic composi tion of Ca(OH)2 on the control plate was δ 13С = ⎯26.645‰, PDB. A similar result was obtained when Ca(OH)2 was applied to a steel plate not exposed to the magnetic field. In the second run, a glass plate with dimensions of 90 × 15 mm uniformly covered with Ca(OH)2 obtained PHYSICAL CHEMISTRY