総合湯（混合泉）（伊香保温泉）
Ikaho Onsen Sogo-yu (Blended Source)Operated by · ホテル松本楼
Mixed source
- Aches & jointsstiff shoulders
- Circulationtired legs
- Warmingcold sensitivity
The eighth-floor Kogane bath is fed by Sogo-yu, the pooled blend of the Ikaho wells. It is a calcium-sodium sulfate-bicarbonate-chloride spring, hypotonic and neutral: sulfate gives the water its quiet body, with bicarbonate softness and a salty edge layered over it. At 41.2 °C at the source and 1.36 g/kg of total constituents it is moderately mineralized, and it carries 7.23 mg/kg of dissolved iron(II). Metasilicic acid runs to 181 mg/kg — high enough to place it squarely in Japan's beauty-water family, leaving the kind of thin silica film that makes skin feel noticeably smoother. The posted usage notice records no dilution, no recirculating filtration and no disinfection; only gentle reheating to hold bathing temperature.
Analyzed May 30, 2017·（社）群馬県薬剤師会
