苦湯(豊国館)
Nigayu (Hokokukan)Operated by · 株式会社 豊国館
酸
Acidic
+ 含硫黄泉 · Sulfate · Chloride
- Color
- colorless and clear
- Taste
- not recorded
- Odor
- hydrogen sulfide odor present
Hydrogen-Sodium Sulfate-Chloride spring
pH 2.2AcidicHot source · 75°CUltra-acidicSulfur-richHigh silica
Composition fingerprint1.2 g/kg dissolved · Hypotonic
H⁺38
Na⁺27
SO₄²⁻70
Cl⁻22
◀ CationsAnions ▶
- Hydrogen H⁺
- makes the water acidic — sharp and bactericidal.
- Sulfate SO₄²⁻
- "gypsum / Glauber's salt" — vessels and wound healing.
Known good for
- Skin conditionsatopic skin, eczema
- Circulationtired legs
- Aches & jointsstiff shoulders
- Sensitive-skin cautionbroken or dry skin
Hokokukan draws Nigayu — the certificate's name for it means "bitter water" — a naturally free-flowing source at Manza, classified as an acidic, sulfur-bearing sodium sulfate-chloride spring of the hydrogen sulfide type. The acidity is sharp enough to prickle on the skin, and the unmistakable rotten-egg note of H₂S rises straight off the water; it looks colorless and clear, yet carries a heavy load of free hydrogen sulfide. The source ranks among Japan's hottest natural springs, and a generous 158.7 mg/kg of metasilicic acid leaves the kind of thin silica film that makes skin feel noticeably smoother afterwards.
Sampled at wellhead·Analyzed Aug 16, 2024·一般財団法人 群馬県薬剤師会環境衛生試験センター
