ABSTRACT

Volcanic gases from Nasudake volcano were analyzed for chlorine, bromine and iodine. It was found that low temperature gases with high chlorine content had lower Br/Cl and I/Cl ratios than did high temperature gases. To explain this finding, mixing processes of two kinds of gases are proposed. They are the original fumarolic gases of Nasudake volcano and the secondary fumarolic gases. The latter is assumed to be high in chlorine content and low in Br/Cl and I/Cl ratios. The experimental results on the distillation of a mixture of hydrochloric acid, hydrobromic acid and hydriodic acid solutions suggested that the hydrogen chloride in the secondary fumarolic gases may be supplied by distillation from the halogen compounds accumulated through the preceding fumarolic activity.