Quantitative measurement of the concentration of sodium carbonate in the system of Na2CO3–H2O by Raman spectroscopy

Na2CO3 concentrations in three Na2CO3–H2O systems(1.5 mol·L− 1, 2.0 mol·L− 1, and 2.5 mol·L− 1) were studied by in situ Laser Raman scattering spectra in a moissanite anvil cell in order to develop a procedure to quantify the concentration of carbonate ion in fluid inclusion in bulk minerals. The relative concentration was obtained by the ratio of the Raman intensity of carbonate ion to that of water. The result shows that there is significant correlation between the ratios of Raman intensity and the concentrations, and the CO32− concentration in Na2CO3–H2O aqueous solution can be determined by the Raman intensity according to the equation c(Na2CO3) = 426RS / (87.3RS + 1). RS = S(Na2CO3) / S(H2O). Comparing with previous methods, it is a rapid and reliable one for determining the concentration of the sodium carbonate solution in Na2CO3–H2O systems and in micro samples, such as those in fluid inclusions and in diamond anvil cells.