Muriatic acid and hydrochloric acid are chemically the same substance, composed of hydrogen chloride (HCl) dissolved in water. The primary distinction lies in their purity and concentration, as muriatic acid is a less refined, commercially available form. This difference impacts their typical applications and handling.
Understanding Hydrochloric Acid
Hydrochloric acid (HCl) is a strong mineral acid. In its pure form, it is a colorless liquid with a pungent odor. This highly corrosive compound fully dissociates in water, giving it a very low pH, typically below 1 in concentrated solutions.
Industrially, pure hydrochloric acid is a fundamental chemical. It is produced by dissolving hydrogen chloride gas in deionized water, yielding a high-quality product for various demanding applications.
The Nature of Muriatic Acid
Muriatic acid is a common, commercially available solution of hydrochloric acid. While chemically identical to HCl, it is typically less pure and often comes in lower concentrations than laboratory or industrial-grade HCl. This commercial grade often contains impurities such as iron, organic compounds, and traces of chlorine gas.
These impurities often give muriatic acid a yellowish tint, distinguishing it from the colorless appearance of purer hydrochloric acid. The presence of these substances can also contribute to a more distinct odor. Common concentrations for commercially available muriatic acid typically range from 15% to 31.45% HCl.
Practical Distinctions and Common Applications
The differences in purity and concentration lead to distinct practical uses. Pure, high-grade hydrochloric acid is used for applications requiring strict control over chemical reactions and minimal contamination. It is used extensively in chemical manufacturing for producing compounds like vinyl chloride, dichloroethane for PVC plastics, bisphenol A, and various pharmaceuticals. It also plays a significant role in regulating the pH of process water streams in industries and in the regeneration of ion exchange resins used for water purification.
Muriatic acid, while corrosive, is widely used for more general-purpose applications where its lower purity is not a hindrance. It is a common choice for household cleaning tasks such as removing rust, stains, and mold from surfaces, or for etching concrete to prepare it for sealing or painting. In swimming pools, it is frequently used to adjust and lower the pH level of the water. Furthermore, muriatic acid, often at around 18% concentration, is a primary agent in the pickling of steel, a process that removes rust and scale from metal surfaces before further processing.
Safe Handling Practices
Handling either muriatic acid or hydrochloric acid requires strict safety protocols due to their corrosive nature. Always wear appropriate personal protective equipment, including thick rubber gloves, safety glasses or goggles, a respirator to protect against fumes, and long-sleeved shirts and pants to cover exposed skin.
Proper ventilation is essential to prevent the inhalation of irritating vapors, so work outdoors or in a well-ventilated area. When diluting the acid, always add the acid slowly to water, never the other way around, to avoid a dangerous exothermic reaction that can cause splashing and heat generation.
Store these acids in tightly sealed, non-metal containers in a cool, dry, and well-ventilated area, away from incompatible materials like oxidizers, organic materials, and other metals. In case of spills or skin contact, immediately flush the affected area with large amounts of water and seek medical attention. Dispose of leftover acid at a hazardous waste facility, or neutralize small amounts with baking soda before disposal if permitted by local regulations.