Muriatic acid is an aqueous solution of hydrogen chloride gas (HCI). It is a highly corrosive acid. It is used commonly as a reactive chemical solution and is a strong acid that is completely solvent in aqueous solution.

At room temperature,muriatic acid gas is colorless to slightly yellow, corrosive, non-flammable, heavier than air, with highly irritating odor. When exposed to air, muriatic acid fumes form dense white. The muriatiuc acid may be released by volcanoes.

The muriatic acid has many uses, for example, to clean, treat and galvanize metal, leather tanning, and in refining and manufacturing for wide variety of products. The muriatic acid can be formed during the burning of many plastics. When it comes into contact with water it form hydrochloric acid. Both the muriatic acid and hydrochloric acid are corrosive.

The muriatic acidwas obtained for the first time by an alchemist called Geber, around the year 800, by mixing with common salt and sulfuric acid.

In the Middle Ages, muriatic acid was known among Europeans as alchemist's spirit of salt or acid salis.

In the seventeenth century, Johann Rudolf Glauber, from Karlstadt am Main, Germany, used salt (sodium chloride) and sulphuric acid to prepare sodium sulphate, which release hydrogen chloride gas. Joseph Priestley, Leeds, England prepared pure hydrogen chloride in 1772, and Humphry Davy Penzance showed that its chemical composition containing hydrogen and chlorine.

During the Industrial Revolution in Europe, demand for alkaline substances, such as soda (sodium carbonate) is needed by the new industrial process, it is developed by Frenchman Nicolas Leblanc by allowing large-scale production with low costs. In this process Leblanc, extract salt in soda by using sulfuric acid, limestone and coal, releasing muriatic acid as a waste product. Until 1863 it was released into the atmosphere as waste. Producers of soda then absorbed this gas in water, producing and muriatic acid on an industrial scale.

In the early twentieth century, the process invented by Leblanc was replaced by the Solvay process. The commercial interest led to the development of other processes of production, which are used to this day. Currently, most of muriatic acid is obtained by absorbing hydrogen chloride released by the industrial production.

The muriatic acid is irritating and corrosive to living tissue. Brief exposure in low levels produces irritation. Exposure to higher levels can cause breathing difficulties, narrowing of the bronchioles, blue color of the skin, accumulation of fluid in the lungs and even death. Exposure to even higher levels can cause swelling and spasms of the throat and suffocation. Some people may suffer an inflammatory response to muriatic acid. This condition is known as reactive airways damage syndrome , which is a type of asthma caused by irritating or corrosive substances.

The acid mixed with oxidizing agents, commonly used as the lavandina (sodium hypochlorite, NaCl) or potassium permanganate (KMnO4) to produce toxic chlorine gas.

Depending on the concentration of muriatic acid, it can cause irritation from mild to severe burns of the eyes and skin. Prolonged exposure to low levels can cause breathing problems, eye irritation and skin and discoloration of the teeth.

Despite these characteristics, gastric juices in the human stomach contains approximately 3% hydrochloric acid. It helps coagulate proteins and plays an important role as pepsin coenzyme in digestion. It also helps in the hydrolysis of polysaccharides present in food. It is secreted by the parietal cells. These contain an extensive network of secretion from where it is secreted muriatic acid towards the lumen of the stomach.

Various mechanisms prevent damage to the digestive tract epithelium by this acid:

• A thick layer covering the mucosal epithelium.
• Sodium bicarbonate in epithelial cells secreted by the pancreas and gastric.
• The structure of the epithelium.
• An adequate blood supply.
• Prostaglandins (with multiple purposes: stimulate mucous secretions and bicarbonate, maintain the integrity of the epithelial barrier, allowing adequate blood flow, stimulates the repair of the damaged mucous membranes).

If for some reason these mechanisms fail, heartburn or ulcers can occur. Drugs called proton pump inhibitors prevent the body produces too much acid in the stomach, while antacids can neutralize the acid.

It can also happen that there is insufficient quantity of hydrochloric acid in the stomach. This is known with pathological terms hypochlorhydria and aclorhidria. It can lead to gastroenteritis.

The hydrochloric acid on contact with certain metals can release hydrogen to form an volatile environment.