In the classroom, phosphoric acid may be used to demonstrate the corrosive properties of acidic chemicals. Phosphoric acid is colourless and odourless, and is generally found as a solid or a thick, viscous liquid. It has a range of industrial and commercial applications, including metal rustproofing and fertiliser enrichment. Direct contact with the acid is dangerous, and can cause severe irritation of the skin and eyes. Though hazardous to the touch, phosphoric acid can be safely disposed of by dilution in water or natural absorption.
Don your rubber gloves and safety goggles prior to handling the phosphoric acid.
Turn on your sink's faucet and allow the stream the run. Dispose of diluted phosphoric acid by pouring it slowly into the stream. Allow the water to run for several minutes afterward to weaken and fully flush the acid.
Pour undiluted phosphoric acid into a large pitcher. Dilute the solution by filling the pitcher to the brim.
Empty the pitcher near the base of a citrus tree or around the perimeter of your garden. The diluted acid serves to enrich the soil and provide healthful phosphates to growing plants.
Fill a sealable plastic container halfway with dry sand or soil. Break up phosphoric acid solids and add them to the container.
Add water to the container and mix the sand with the solids until moist. Seal the container and dispose of it at your nearest sanitary landfill. Alternatively, the sand or soil may be spread near the base of a citrus tree or over your garden.
Check your city's hazardous waste disposal codes before pouring diluted phosphoric acid down your sink drain.
Never handle phosphoric acid in any form without rubber gloves or safety goggles. Do not allow children or pets near the open container of acid. If you recycle the acid by adding it to the soil, do not allow pets near the area for several days.