Ensulizole Solubility and pH Behavior
Question
Is it correct that Ensulizole (Phenylbenzimidazole Sulfonic Acid) dissolves clearly at pH around 6.9, becomes cloudy/precipitates when the pH drops to approximately 4, and redissolves clearly when pH is adjusted back to 6.8-6.9 using Sodium Bicarbonate?
Answer
Ensulizole Dissolution
Your observation regarding the dissolution of Ensulizole (Phenylbenzimidazole Sulfonic Acid) is correct.
Ensulizole requires a pH above 6.8 to dissolve properly in water. When you added Ensulizole to your solution at pH 6.9, it likely caused the pH to drop. At the lower pH of around 4, Ensulizole precipitates out of the solution, making it cloudy and causing sediment.
When you adjusted the pH back up to 6.8-6.9 using Sodium Bicarbonate, you brought the solution back into the optimal pH range for Ensulizole dissolution. This allowed the precipitated Ensulizole to redissolve, resulting in a clear, colorless solution.
Therefore, the process you described is the correct way to handle Ensulizole to ensure it is fully dissolved and the solution is clear.