Hydrochloric acid is a corrosive, fuming, poisonous, highly acidic solution of hydrogen chloride (HCl). Sodium hydroxide is a caustic, strongly alkaline compound (NaOH) used in drain cleaners. If ingested, hydrochloric acid corrodes the mucous membranes, esophagus, and stomach causing dysphagia, nausea, circulatory failure and death. Sodium hydroxide, if ingested, will cause vomiting, prostration, and collapse. Why is it that if you mix these two substances in the right proportions before ingesting them you will not have any poisoning symptoms?
Hydrogen chloride combines with sodium hydroxide to form common salt (sodium chloride) and water.