Fluorescein has a OH group and a COOH group. If a solvent containing NaOH is added it can deprotonate those group creating a more soluble salt. ex. O-Na+ and COO-Na+ These salts are soluble. Solution Fluorescein has a OH group and a COOH group. If a solvent containing NaOH is added it can deprotonate those group creating a more soluble salt. ex. O-Na+ and COO-Na+ These salts are soluble..