Volcanic gases from several active volcanoes in Japan have been analyzed for iodine and chlorine: Showashinzan (I=0.025–0.20 mg.I/kg.H2O, Cl=238–1830 mg.Cl/kg.H2O), Iwatesan (I=0.053–0.19, Cl=2720–3360), Issaikyoyama (I=0.030–0.087, Cl=104–213), Nasudake (I=0.16–3.9, Cl=188–9460), Yakedake (I=0.58–0.93, Cl=1250–1730), Kuju-Ioyama (I=0.13–1.3, Cl=266–8000), Kirishima-Ioyama (I=0.036–0.84, Cl=200–4200), and Miharayama (I=0.45–1.5, Cl=1640–2180). Each volcano has a characteristic I/Cl ratio. Analyses have also been made of hot-spring waters from the environs of Nasudake, Kuju-Ioyama, and Kirishima-Ioyama. It is indicated that the hot-spring waters are similar in I/Cl ratio to the volcanic gases from the same area.

Geochemical study Behavior of of iodine iodine in in volcanic gases. II. volcanic gases.

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 com pounds accumulated through the preceding fumarolic activity.

A siliceous sublimate, collected from an active fumarole of Kuju Volcano, was analyzed for major constituents.The water soluble fraction of the sublimate contains large quantities of halogen acids and silicon, and the insoluble fraction consists of hydrated silica with a trace amount of native sulfur. In order to as certain the presence of gaseous silicon compounds in fumarolic gases, condensate samples were collected from high temperature fumaroles of Kuja and Nasudake Volcanoes with a silica-free sampling device. The silicon and fluorine contents of fumarolic gases range from 1 to 52 mg Si/kg H20 and 1 to 320 mg F/kg 1120, res pectively.Silicon is transported probably as fluoride in fumarolic gases, and the sublimate is formed by hydrolysis of silicon fluoride when the gas temperature falls to the boiling point of water.