How do I properly dispose of used acid/caustic containers?

The Safety Exchange Says: The first concern here is that no one reuses emptied hazardous materials containers for food or drinking water. When dispensing the last of the contents carefully rinse the container several times with water and utilize the rinsate in your cleaning process. Don’t forget to wear your PPE, as even dilute acid/caustic can cause chemical burns or severe eye injury.

Once adequately rinsed, render the containers unsuitable for reuse by defacing the labels and puncturing the container. At this point the container materials should be suitable for recycling. You can also check with your chemical supplier; they sometimes take back used containers.