Water-soluble materials formed by the reaction between a volcanic rock and HCI and/or SO2 gases

Experiments on the reaction of a volcanic rock, dacite with HCI and /or SO2 gases have been carried out at room temperature to 800℃ for understanding of the condition of the formation of water-soluble materials on volcanic ash. HCI reacted with the dacite mainly at low temperatures (≤200℃), whereas SO2 did at high temperatures (≥400℃). It was also found that CI/SO4 ratios of water-soluble materials were very high at low temperatures, but decreased rapidly with increasing temperature. In the experiments using a mixture of HCI and SO2, the cation composition at 600℃ and 800℃ was revealed to be significantly different from that at lower temperatures, suggesting the change in the reaction process with temperature.