The desalting treatments, using the compression and immersion method, were carried out on an old Greek and Roman stone made of limestone. The conductivity of the leached solution was measured, and the ions present in it were analysed by ion chromatography and titration with sulfate solution for HCO3¯. The conductivity of the solution leached by the compress method for stone significantly varies from place to place (1970µS/cm－1200µS/cm), which is divided into eleven portions for desalting. The conductivity of the solution leached by the immersion method decreased rapidly after the broken fragments of stone were immersed in it for 24h. The results of analysis for each ion showed that the leached solution contained Na+, Ca2+, K+, Mg2+, Cl¯, HCO3¯, and SO4 2 ¯ ions. This result suggests that these ions were extracted by nitrate, chloride, carbonate (hydrogencarbonate), and sulfate, which had precipitated in the stone. The analyses by X-ray diffractometer and SEM revealed the presence of both NaNO3 and NaCl as salts precipitated. It is noted that the presence of NaNO3 as a salt has been rarely reported in ancient cultural assets. As a result of desalting by the compression method for stone, the concentration of the leached solution in each portion was vastly different from that of the others, particularly in terms of Mg2+, SO4 2 ¯, and HCO3¯ ions. It may be possible that the amount of salt in each portion of stone was already uneven at excavation, and/or salts migrated from other portions in the process of desalting treatment. The ratios of SO4²¯/Cl¯ in the leached solution are significantly higher in the immersion method than in the compression method. It follows that sulfates, such as CaSO4, are not easily dissolved in the treatment process by the compress method. The immersion method, therefore, is necessary for the complete extraction of the salts precipitated.
