UW-Green Bay

Neutralization

If liquids meet all standards for the sanitary sewer except for pH, campus employees may neutralize the solution before pouring down the drain. Use proper equipment. Goggles, gloves, apron, and hood are required. Add neutralizing agent slowly, stirring constantly. If you are not familiar with neutralization techniques, do not attempt to neutralize solutions. Call the Hazardous Waste Manager for assistance. Report neutralization activities to the University Safety Manager for regulatory reporting. 

  • Acidic solutions ( pH <5)
  • Adjust the pH to 5-9 using a dilute solution (e.g. KOH, NaOH, NaHCO3). Use a pH meter, indicator solution, or pH paper to determine the pH.
  • Flush down the drain of a chemical sink with 20 volumes of cool water.
  • Basic solutions ( pH > 9)
  • Adjust pH to 5-9 using a dilute solution (e.g. HCl, H2SO4, HNO3 ). Use a pH meter, indicator solution, or pH paper to determine pH.
  • Flush down the drain of a chemical sink with 20 volumes of cool water.

Note: For highly concentrated acids, neutralization with a relatively dilute basic solution will take a very large volume of base and a long time. In this case, consider neutralization using a concentrated basic solution with plenty of ice for an ice bath, performed slowly, and carefully and with constant stirring. Monitor the temperature of the solution with a suitable thermometer to ensure that the solution doesn't get too hot. The same is true for neutralizing some concentrated bases.