Johnson® Congo red-, Brilliant yellow-, Turmeric-, Phenolphthalein-, & Clayton yellow- Papers for Analysis of a Solution(Acidity or Alkalinity), pH Neutralization Point Test Paper 특정영역대의 pH 연화점(중하점) 측정지들 : 콩코레드, 브릴리안트옐로·강황지·페놀프탈레인·크레이톤옐로-중화점에서 변색됨