Studies on the Complex Ions in Mineral Springs. I

Absorption Spectra of Mineral Springs

Abstract

Relationship between absorption spectrum and components of a hot-spring water was examined and following facts were revealed.
1) Absorptions appearing in the ultraviolet to visible region are chiefly due to the iron (III) complex ions (Fe³⁺-aquo, FeSO₄⁺, FeOH²⁺, etc.) or sulfur compounds (H₂S, S₂O₃^2-, etc.).
2) Marked variation in the absorption spectra is observed when acidic vitriol spring containing hydrogen sulfide is left in the air. At first, absorption due to H₂S appears in the shorter wave-length side at around 260 mμ, which diminishes as the spring water is left in the air, and an absorption of iron (III) complex ion appears in a wide range from ultraviolet to visible region as Fe²⁺ is oxidized to Fe³⁺.
3) The absorption with a maximum at 300 mμ appearing in the strongly acidic iron spring is due to FeSO₄⁺, and this absorption is overlapped by the absorption due to FeOH²⁺ in weakly acidic iron spring and by that due to FeCl²⁺ in iron springs containing chlorine ion. Absorption maxima of Fe³⁺-aquo, FeOH²⁺, and FeCl²⁺ appear respectively at around 240, 300, and 330-350 mμ, but they overlap the absorption of FeSO₄⁺, and are not clearly observed.