The Ascorbic Acid Test Strip is used to detect Ascorbic Acid, or Vitamin C in graduations of 0, 0.01, 0.02, 0.05, & 0.1%. The Ascorbic Acid test strip is based on discoloration of blue red-ox indicator, depending on the concentration of ascorbic acid. Red-ox indicator is also sensitive to acidic compounds, and its blue color turns to purple in the presence of acids. Vial: 50 strips.