1-Naphthol-5-Sulfonic acid / 5419-77-2 , L-acid best quality,lowest price 1-Naphthol-5-Sulfonic acid / 5419-77-2 , L-acid Our specification as following:Appearance :Grey or with slight red powderContent:60.0%minFe Content:100ppm maxSO2 Content:0.5% max Insoluble residue in water:0.25% max 1-Naphthol-5-Sulfonic acid / 5419-77-2 , L-acid