海門温泉
Kaimon OnsenOperated by · 豊後高田市観光まちづくり株式会社
Sampled at wellhead
塩
Chloride
Classification
Sodium-Magnesium Chloride spring
A sodium-magnesium chloride spring labeled 'kyo-ensen' (strong-salt) on the certificate — at 24.45 g/kg total dissolved it approaches ocean salinity. Clear at the wellhead but with a forceful salty-bitter taste and a faint iron note; the lab sample yellows and turns slightly cloudy within hours. Neutral pH, hypertonic, with a generous 168.5 mg/kg of metasilicic acid — bathers leave with a thick mineral coating clinging to the skin.
pH
6.20
Neutral
Source temperature
40.8°C
Warm
Tonicity
24.45g/kg
Hypertonic
Free CO₂
489mg/kg
Typical
Free H₂S
0.01mg/kg
Low
- Color
- colorless and clear
- Taste
- strongly salty, moderately bitter
- Odor
- very faint metallic
Highlights
- Strong salt
- High silica
Analyzed Apr 17, 2023·大分県衛生環境研究センター·Cert no. 衛理研第242号の1