湯SimpleSodium Chloride spring
Gero Onsen — a sodium-led simple thermal water as documented on this wall panel. Mineralization is light (total dissolved solids 374.4 mg/kg, gas excluded), so the water reads gently on the body rather than heavily. The panel reproduced here covers only the ion table; spring temperature, pH and the formal classification are not visible in this crop, so the bath-side feel is best confirmed at the property itself.
Good for
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
Cationsshare of charge (mval%)
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺110mgP32 national95%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺4.3mgP16 national4%
- PotassiumK⁺1.9mgP22 national1.0%
- Magnesiummild; a laxative if you drink itMg²⁺0.10mgP11 national
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- FeTotalFe< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
Anionsshare of charge (mval%)
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻105mgP42 national56%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻26.0mgP79 national17%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻37.5mgP22 national12%
- Fluoridetrace; drinking limits applyF⁻10.1mgP92 national10%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻12.7mgP25 national5%
- Hydrogen sulfideHS⁻0.70mgP63 national0.4%
- NitrateNO₃⁻0.20mgP36 national0.1%
Non-dissociatedmeasured by mass
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃59.7mgP36 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂6.1mgP43 national
- Metaarsenious acidHAsO₂0.90mgP90 national
Dissolved gasesmeasured by mass
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂< —mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂SNDmg
Measured at the source
Tonicity
0.37g/kg
Hypotonic
Free CO₂
0.10mg/kg
Low