What is the proper way to dispose of used hydrochloric acid (e.g. Sureklean 600)? My municipal waste station does take toxic waste periodically but I was wondering if it can be safely flushed down the toilet. It is very corrosive to metal and I know there is cast iron sewer pipe below the basement leaving the house to the street. Also, is it safe to flush it from the environmental standpoint?
HCl can be combined with baking soda to form salt water and CO2.
NaHCO3 + HCl = NaCl + H2O + CO2
NOTE this is exothermic and effervescent, mix slowly, adding the soda to the acid. In a wide-mouth container.