Hydrochloric acid, also known as muriatic acid, the water-based solution of hydrogen chloride, is a highly corrosive acid. It is used to make batteries and fireworks, make gelatin and process sugar, but it is also produced naturally in the stomach to aid digestion as gastric acid. You must dispose of hydrochloric acid as hazardous waste by taking all necessary safety precautions, but the exact method varies by state. Contact your local officials to find out the hydrochloric acid disposal rules in your area.

Your state may allow you to pour diluted hydrochloric acid down your sink. Ensure the room is ventilated by opening windows and doors. Cover all areas of your skin with suitable protective clothing, such as long sleeves, safety goggles, a mask and rubber or neoprene gloves. Carefully pour one-quarter to one-half-cup of the hydrochloric acid into 2 to 5 gallons of water. It's very important to always add the chemical to the water and not the water to the chemical. Pour the diluted solution down the sink, flushing with large amounts of water. Work slowly to avoid splashes.

Some states won't allow you to flush hydrochloric acid unless you neutralize it first. Neutralize hydrochloric acid with an alkali (base), such as sodium bicarbonate (baking soda). Wearing your protective garments and working in a ventilated area well away from children, pets, heat and metals, prepare a base mix. Mix 1 lb of baking soda with plenty of water. Slowly add the hydrochloric acid. The mixture will fizz. Add more baking soda until the fizzing stops. This means the hydrochloric acid is neutralized and can now be flushed down the sink with large quantities of water.

If your home is connected to a septic tank, don't flush hydrochloric acid down the sink even if it is diluted. The acid can ruin the bacterial process in the septic system and drain field. Never dispose of hydrochloric acids or any other acids or bases on the ground, in a storm drain or in a gutter, because they can contaminate groundwater, surface water and drinking water supplies. Don't dispose of hydrochloric acid in your trash because if it leaks it could cause injury to someone. If you are unsure about how to dispose of hydrochloric acid correctly, ask your local waste facility for advice. Some towns have professional disposal companies who will dispose of acids and bases for a fee. Your local pool company may also be willing to dispose of the acid, or your local waste management plant may take the acid to use.