What is Hydrochloric Acid?

Different test tubes with hydrochloric-acid inside. Blue, red and yellow liquid. Placed on a periodic table.

Hydrochloric acid (HCl) is a strong corrosive aqueous solution. Discovered in about 800 AD by alchemists, it is strong-smelling, colorless or slightly yellow inorganic acid with a pH range of 1−3 (very acidic).

How to make Hydrochloric Acid?

In the human body, the cells lining the stomach wall make hydrochloric acid by splitting a compound called sodium chloride into HCl and sodium bicarbonate.

Hydrochloric acid can be synthetically produced for industrial purposes by dissolving hydrogen chloride gas (usually a byproduct from other chemical production processes) in water.

Unless pressurized or cooled, the acid will turn into gas if there is less than 60% water present. It should be stored in a tightly closed appropriate container (polyvinyl chloride not metal!) in a well-ventilated, cool, dry area, away from oxidizing materials.

You can even make it yourself if you have a chemistry kit, by mixing salt with sulfuric acid within a closed system; this creates hydrogen chloride gas which then turns into HCl as it is bubbled through water.

What is the role of HCI in the human body?

Within the human body, hydrochloric acid is found in the stomach, where it makes up a large proportion of gastric acid, the body’s digestive fluid, which also contains potassium chloride and sodium chloride.

It is secreted by the parietal cells that line the stomach wall, which also produces mucus to protect the stomach wall from getting damaged by hydrochloric acid, given its corrosive nature.

The primary role of secreted HCl is for the digestion of food; it is particularly important for the digestion of protein as it aids protein unfolding, allowing the body to absorb important nutrients.

After food is eaten, the parietal cells also release bicarbonate into the bloodstream to maintain the plasma’s electrical balance, resulting in an ‘alkaline tide’ which increases the pH of the blood for a couple of hours.

Hydrochloric acid has a secondary role in the stomach of preventing infection from any bacteria or viruses that may be ingested with food.

Many pathogenic microorganisms cannot grow in an acidic environment, so they are killed within 15 minutes when the environment is pH 3.0 or less. Of course, there are some microorganisms that have adapted to be able to survive in these conditions, hence gastro infections occurring.

How does drinking alkaline water affect hydrochloric acid in the stomach?

Hydrochloric Acid found in the stomach has a PH of 2–4 and alkaline water has a pH of over 7.

Many people worry that drinking alkaline water will neutralize stomach acid, preventing its important function in digesting food and pathogens, resulting in digestive problems and infection.

However, what actually happens is that the cells lining the stomach wall react to the arrival of alkaline water by producing even more HCl to lower the pH of the stomach to its optimal level.

The stomach cells make HCl by splitting a compound called sodium chloride into two parts: HCl and sodium bicarbonate.

The HCl goes into the stomach and the sodium bicarbonate is released into the bloodstream where it is used by other parts of the body such as the liver and pancreas to regulate acidity.

So in fact, drinking alkaline water actually improved digestion by stimulating the body to produce more hydrochloric acid.
ph meter draft with a pointer to a green field. Semi-circle shows red, acidic for hydrochloric acid, to purple, alkaline.

What is hydrochloric acid used for?

is used as an industrial chemical with an incredibly wide range of applications. It is used in the following ways (concentrations vary):

  • As a food additive to enhance flavor and prevent spoilage (as an acidity regulator in sauces and vegetable juices)
  • For the production of gelatin (a gelling agent used in food, medicines, vitamin capsules and cosmetics)
  • In sugar processing
  • As a descaling agent (to remove limescale from metals that come into contact with hot water)
  • In plastic production, for example, the manufacture of polyvinyl chloride (used in windshields and pipes) and polyurethane foam (used in mattresses and insulation)
  • In the leather industry (used for tanning hides to make leather)
  • In the steel industry (removal of impurities from steel) for example for making bridges and cars
  • Production of fertilizer
  • Creation of dyes
  • Swimming pool sanitation
  • Production of batteries and fireworks
  • To produce other chemicals, for example, mixed with limestone it creates calcium chloride which is used for deicing roads, as an antimicrobial and as a food stabilizer

Is it dangerous?

Yes – it is a hazardous and corrosive acid that should not come into contact with other parts of the body as it can cause chemical burns on the skin, irreversible damage to mucous membranes (for example the mouth, nose, eyelids), blindness and even prove fatal.

Hydrogen chloride gas (also colorless or slightly yellow and pungent-smelling) forms HCl upon contact with body tissue; inhalation of these toxic fumes can cause choking, coughing, upper respiratory inflammation, pulmonary edema, and death.

In fact, there are known murder cases where victims were entirely dissolved in concentrated HCl, leaving no bones or teeth behind, although it can take a whole day.

HCl can also easily dissolve some metals such as magnesium and zinc and to a lesser extent, iron, and copper. Depending on the reaction, this can result in hazardous gases being produced.


Several test glasses of different sizes filled with hydrochloric acid.

Where to buy?

Hydrochloric Acid is widely available at varying percentage strengths online or from hardware stores. It is sometimes listed as ‘muriatic acid’ an alternative name for HCl meaning ‘pertaining to salt’.

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These information were not written by the American Food and Drug Administration, or any other official authority. This site and its products do not promise to diagnose and cure diseases, or protect you from them. Always consult your doctor when you are sick.