下呂温泉
Gero Onsen湯
Simple
Sodium Chloride spring
High silica
Composition fingerprint0.4 g/kg dissolved · Hypotonic
Na⁺95
Cl⁻56
CO₃²⁻17
◀ CationsAnions ▶
- Sodium Na⁺
- salt's cation — pairs with chloride to make the water salty.
- Chloride Cl⁻
- table-salt anion — coats the skin and holds heat in.
Known good for
- Smooth skindry, rough skin
- Recoveryfatigue, stress
A lightly mineralized simple thermal spring: the Gero Onsen composition table lists just 374 mg/kg of dissolved solids, so the water is gentle and unassertive on the body. Chloride leads the anion side, but at such low absolute concentration it reads as softness rather than salt. What stands out instead is metasilicic acid at around 60 mg/kg — enough to leave the thin silica film that puts this water squarely in Japan's beauty-water family.
