Hydrochloric acid is hydrogen chloride dissolved in water. It has corrosive properties and is used as a chemical reagent or as muriatic acid (strong water). Caution is needed when handling it as it can cause burns on the skin and tissues that come into contact with the substance.
Contents
What is hydrochloric acid
Its chemical formula is HCl and it is known by various names such as muriatic acid, salt acid, or strong water, although its most common name, the one everyone knows, is hydrochloric acid.
In many places, it can be bought as muriatic acid. It has descaling properties and is used to remove lime from metals where water runs.
Uses (what it’s for)
- As an acid due to its low cost.
- It works as a product to eliminate lime.
- As a chemical agent to produce organic chlorides.
- To produce demineralized water.
- To make gelatin industrially. Hydrochloric acid is used to dissolve the bone mineral portion.
- To destroy rust on metals.
- In metabolism, naturally produced hydrochloric secretion aids in protein absorption from food.
- To clean pools.
- To lower the water’s pH.
Hydrochloric acid, known as muriatic acid or strong water, is an acid that goes by different names, as we’ve mentioned. It is very common in South America as muriatic acid, chloric acid, or marine acid.
But, regardless of the nomenclature used (HCl or hydrogen chloride), its formula is the same, that is, HCl, and it also maintains its same properties as outlined below.
For Pools
In chemical form, it is used to lower the pH of pool water, requiring the addition of 10 liters of hydrochloric acid per 20,000 liters of pool or pond water.
Generally, the use of hydrochloric acid for pools is indicated to maintain the water’s pH between 7.2 and 7.6, the range where chlorine acts and works to disinfect and purify stagnant water. Thus, it helps control the appearance of algae and other microorganisms that could make the bathwater unhealthy.
Properties of hydrochloric acid
It has a yellowish color, and its vapors irritate the mucous membranes and the respiratory tract, so proper protection is needed to avoid inhaling or touching it.
As it is a corrosive acid, it has applications both in industry and at home, providing different benefits depending on its use. To better understand what it’s for, here are the properties of hydrochloric acid:
- It irritates the respiratory tract.
- It causes skin burns.
- The gas it produces is heavier than air.
- It burns biological or organic tissues.
- It has corrosive properties on metals and acts by eliminating lime.
- It works as a reagent when dissociated in water.
- The pH of hydrochloric acid is less than 1 (it is highly acidic).
- It is non-flammable.
Since hydrochloric acid has a very low pH, it is very dangerous for people and cellular tissues. It acidifies intensely, and a simple contact with the skin can cause severe burns, which is why gloves, goggles, and a mask are always recommended for protection when handling it.
As it is a liquid, it can splash, which is why chemical protection is advisable.
Safety measures must always be followed, and the instructions provided in the safety data sheet of hydrochloric acid should be consulted when handling it.
Avoid contact with eyes and mucous membranes, and keep it away from children.
When conducting a chemistry experiment with hydrochloric acid and zinc to observe its reaction, always place the test tube away from us so that the produced vapors do not reach our nostrils. This could cause irritation and, in case of large inhalations, burns to the larynx, trachea, etc.
Just as it is harmful when in contact with skin and mucous membranes, it should not be ingested. Ingesting hydrochloric acid will cause severe burns and could be fatal even in small doses.
One of its properties is that it denatures proteins, destroying them and causing irreversible damage in many cases.
Furthermore, hydrochloric acid has the ability to lower the pH of pool water or any place where it is added, and can serve as a pH regulator. However, due to its danger, it should always be used with caution and by controlling the amounts added. Let’s remember that it is muriatic acid, a strong acid that destroys respiratory and gastrointestinal tissues when ingested.
Physical and Chemical Properties
- Color: colorless and sometimes light yellow.
- Density: 1190 (37% solution), 1160 (32% solution), 1120 (25% solution) kg/m3; 1.12 g/cm3.
- Molar mass: 36.46 g/mol.
- Melting point: 247 K or -26 ℃.
- Boiling point: 321 K or 48 ℃.
- Acidity or pKa: -6.2.
- Viscosity: 1.9.
- CAS number: 7647-01-0
Solubility
The solubility of hydrochloric acid is 8.23 g/l. It is soluble in water and in its commercial form, it can be purchased with a purity of 25 to 38%.
Sales in higher concentrations are much rarer as it tends to evaporate easily, making it impractical for use unless in controlled conditions.
At concentrations higher than 40%, this strong acid must be stored and handled with high safety measures, significantly increasing the final product’s cost.
Below are the physical and chemical properties related to its solubility:
- Solubility in water at 0 º C: 8.23 g/l.
- At 60 ºC: 561 g/l.
- Can also be dissolved in benzene alcohol and ether.
- It is insoluble in hydrocarbons.
Density and Characteristics
Its density varies with concentration, and its characteristics such as molarity and density of hydrochloric acid can be seen below:
| Conc. (m/m) c : kg HCl/kg | Conc. (m/v) c : kg HCl/m3 | Density ρ : kg/l | Molarity M | pH | Viscosity η : mPa·s | Specific heat s (kJ/(kg·K)) | Vapor pressure PHCl : Pa | Boiling point b.p. | Melting point m.p. |
| 10% | 104.80 | 1.048 | 2.87 M | -0.5 | 1.16 | 3.47 | 0.527 | 103 °C | -18 °C |
| 20% | 219.60 | 1.098 | 6.02 M | -0.8 | 1.37 | 2.99 | 27.3 | 108 °C | -59 °C |
| 30% | 344.70 | 1.149 | 9.45 M | -1.0 | 1.70 | 2.60 | 1,410 | 90 °C | -52 °C |
| 32% | 370.88 | 1.159 | 10.17 M | -1.0 | 1.80 | 2.55 | 3,130 | 84 °C | -43 °C |
| 34% | 397.46 | 1.169 | 10.90 M | -1.0 | 1.90 | 2.50 | 6,733 | 71 °C | -36 °C |
| 36% | 424.44 | 1.179 | 11.64 M | -1.1 | 1.99 | 2.46 | 14,100 | 61 °C | -30 °C |
| 38% | 451.82 | 1.189 | 12.39 M | -1.1 | 2.10 | 2.43 | 28,000 | 48 °C | -26 °C |
Formula
In an aqueous solution, its formulation occurs when hydrogen chloride, a monoprotic acid, releases an H+ ion (a proton).
When this chemical reaction occurs, the ion binds to a water molecule, resulting in H3O+, that is, an oxonium ion.
Another ion that appears is chloride. This is why it is possible to produce chloride salts.
The formula of hydrochloric acid is HCl and is considered a strong acid as it dissociates completely in water.
Burns from Hydrochloric Acid
As mentioned, it has corrosive properties. It serves to break down soft, organic tissues as well as metals and plastics. Its toxicity is high, and it is generally sold in commercial solutions more suitable for domestic and industrial use.
Pure hydrochloric acid has a high density, so it must always be handled with gloves to avoid hydrochloric acid burns on the skin and mucous membranes.
To prevent damage, strict safety standards must be followed in the workplace, paying attention to the instructions and its safety data sheet. The longer the exposure time, the greater the corrosive damage.
Chemical burns are more serious than thermal burns because they continue to act after the initial exposure to the substance. They cause more severe damage to the exposed tissues, and the consequences are long-term. A hydrochloric acid burn destroys proteins and biological activity, distorts the pH, making recovery difficult even after deactivation.
Hydrochloric Acid Secretion in the Stomach
Although it is a widely used chemical, it also has a natural presence in the human body. The secretion of hydrochloric acid in the stomach occurs along with other chemical substances to aid in the digestion of food.
When we eat or even when we smell food, the synthesis of hydrochloric acid begins in the body along with histamine and pepsinogen. A small amount of all these substances is released into the stomach.
The organic synthesis occurs when the food ingested moves through the digestive tract. At this moment, the distension causes the vagus nerve to react, increasing the demand for gastric juices to process the food properly. Here, we can say that the secretion of hydrochloric acid occurs in the body.
Hydrochloric acid has a very low pH, and to prevent it from lowering further in the body, the presence of polypeptides and proteins is necessary to slow the drop in pH. Once the ingested proteins are gone, the secretion of hydrochloric acid and gastrin decreases because they are no longer needed.
The uses and function of hydrochloric acid in metabolism serve as a natural chemical that denatures proteins. This allows for the breakdown of food to metabolize and absorb the nutrients it contains.
However, for its synthesis to occur, Niacin which serves as Vitamin B3 is needed.
Excess Secretion in the Stomach
If not neutralized after digestion, there can be an excess of hydrochloric acid in the stomach. Although it has always been indicated that excessive secretion causes stomach acidity, recent medical reviews and research challenge this statement.
Excess hydrochloric acid does not cause acidity, but stomach acidity occurs due to a lack of acids or gastric juices. Several publications mention this, such as Xavi Verdeguer, who discusses heartburn, or this one by Lumberts on hypochlorhydria, which is the same, and you can see it here.
In any case, if symptoms of heartburn or acidity are frequent, it is always advisable to consult with a family doctor to verify whether it is a deficiency or an excess of secretion.
Commercial Names
- Muriatic acid.
- Strong water.
- Muriatic acid (America).
- Marine acid.
- Salt acid.
Where can I buy muriatic acid?
You can get it at any hardware store or tlapalería in Mexico.