Hydrochloric Acid 37% (Reag. USP) for analysis, ACS, ISO

Muriatic Acid

Assay (Acidim.): 36.5-38.0 %
Molecular Formula
Molar mass
36.46 g/mol

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Melting Point:
-25 °C
Boiling Point:
85 °C
1.19 kg/l
Miscible with water
Physical Description:
Product Code:
Product Name:
Hydrochloric Acid 37% (Reag. USP) for analysis, ACS, ISO
Quality Name:
for analysis, ACS, ISO
Assay (Acidim.): 36.5-38.0 %
Density 15/4: ≥ 1.19

Maximum limit of impurities
APHA colour: 10
Appearance: passes test
Residue on ignition (as SO4): 0.0005 %
Chlorine (Cl): 0.0001%
Ammonium (NH4): 0.0003%
Bromide (Br): 0.005%
Phosphate (PO4): 0.00005 %
Sulfate (SO4): 0.0001%
Sulfite: 0.0001%
Extractable organic substances: passes test
Heavy Metals (ICP-OES): 0.0001 %

Metals by ICP [in mg/Kg (ppm)]
Ag: 0.05
Al: 0.1
As: 0.01
Au: 0.1
B: 0.2
Ba: 0.05
Be: 0.02
Bi: 0.05
Ca: 0.5
Cd: 0.01
Co: 0.01
Cr: 0.02
Cu: 0.02
Fe: 0.2
Ga: 0.05
Ge: 0.02
Hg: 0.1
In: 0.05
K: 0.1
Li: 0.02
Mg: 0.1
Mn: 0.01
Mo: 0.01
Na: 0.5
Ni: 0.02
Pb: 0.02
Pt: 0.1
Sb: 0.01
Si: 0.1
Sn: 0.1
Sr: 0.02
Ti: 0.05
Tl: 0.02
V: 0.01
Zn: 0.1
Zr: 0.02
Hazard pictograms
  • GHS05 Hazard
  • GHS07 Hazard
Room Temperature.
Signal Word:
GHS Symbols:
H Phrases:
P Phrases:
Master Name:
Hydrochloric Acid 37%
Synonyms Long Text:
Muriatic Acid
Index Nr.:
Download TDS file for complete specifications


About Hydrochloric Acid
Hydrochloric acid is an aqueous solution of gaseous hydrogen chloride protolyzed in oxonium and chloride ions. It is a strong, inorganic acid and belongs to the mineral acids. Its salts are called chlorides, the best-known being sodium chloride (NaCl, table salt).

Indirectly, its use is already mentioned by Pliny, in the separation of gold and silver in mining, in that at high temperatures common salt and vitriol form hydrochloric acid, which forms a compound with the silver. Possibly Georgius Agricola mentions a similar process for the separation of silver in his De Re Metallica of 1556 (the recipe given would give hydrochloric acid if by salt is meant common salt). Pseudo-Geber (13th century) described a reaction of mercury after heating with common salt and alum or ferrous sulfate, forming fine white needles of mercuric chloride by reaction with hydrochloric acid. He and medieval alchemists were also familiar with aqua regia, which was produced by adding sal ammonia (ammonium chloride) or common salt to nitric acid. In the 15th century, hydrochloric acid and its use for softening bones and ivory for carving was mentioned, first in an anonymous Italian manuscript of the mid-15th century, located in the University of Bologna, then in a recipe by Caterina Sforza (1490). It was produced by both authors by heating common salt and vitriol and distillation.
In the first half of the 15th century, Basilius Valentinus obtained hydrochloric acid by reacting halite (rock salt) with iron vitriol. In 1597 Libavius mentions hydrochloric acid in his book Alchemia, but it was also mentioned by Giambattista della Porta (Magiae Naturalis 1558, 1589) as the best means for bleaching teeth. Its production on a large scale from table salt and sulfuric acid was achieved by Johann Rudolph Glauber in the 17th century. Lavoisier called hydrochloric acid acide muriatique (Latin muria 'brine'). Saline springs are still called muriatic springs today. In North America, hydrochloric acid is also called muriatic acid.

In nature, hydrochloric acid is found in volcanic gases and highly diluted in crater lakes. In free form, it occurs in the gastric juices of vertebrates (0.1 to 0.5 percent by mass). Almost inexhaustible are the deposits of salts of hydrochloric acid, as rock salt and dissolved in seawater.

Preparation and extraction
Hydrochloric acid is produced in the laboratory from concentrated sulfuric acid and common salt (hence the name):

NaCl + H2SO4 → NaHSO4 + HCl

The sulfuric acid displaces the hydrogen chloride from its salt. Since hydrogen chloride is gaseous, it is constantly withdrawn from the equilibrium, which is thus almost completely on the side of the products. The sodium hydrogen sulfate formed is an acid sulfuric acid salt. The resulting hydrogen chloride gas is then introduced into water:

HCl + H2O → H3O+ + Cl-

Hydrochloric acid with higher mass fractions of hydrogen chloride is also called fuming hydrochloric acid, because hydrogen chloride gas escapes and hydrochloric acid is formed again with the water from the atmospheric humidity, so that a white mist is formed above open vessels. In the chemical industry, high-purity hydrogen chloride is obtained by reacting hydrogen with chlorine:

H2 + Cl2 → 2 HCl

Here the hydrogen chloride is allowed to react with water, too. Technically pure hydrochloric acid is produced mainly as a by-product in the chlorination of organic compounds.
Hydrogen chloride gas dissolves very well in water: at 0 °C, 1 liter of water, provided it is still present as a liquid phase, dissolves 815 g or 507 liters of gas under heat generation. At 20 °C, one liter of saturated hydrochloric acid contains 720 g HCl. The concentration dependence of the density seems to be a simple mathematical relationship between the density of the solution and the percentage content of hydrogen chloride: The doubled decimal places correspond approximately to the concentration, e.g., a hydrochloric acid of density 1.10 g-cm-3 to an HCl content of 20 percent.

% = 200 * (Density – 1)

The melting and boiling behavior of hydrochloric acid depends strongly on its composition. In solid phase, four stoichiometric hydrates with defined melting points are formed. These are a monohydrate HCl * H2O with a melting point at -15 °C, a dihydrate HCl * 2 H2O with a melting point at -18 °C, a trihydrate HCl * 3 H2O with a melting point at -25 °C, and a hexahydrate HCl * 6 H2O with a melting point at -70 °C. In the phase diagram, corresponding eutectic melts are obtained for compositions between the stoichiometric hydrates. These are at -23 °C for a mixture of mono- and dihydrate with a mass fraction of hydrogen chloride of 57.3%, of di- and trihydrate with a mass fraction of 44.0% at -28 °C, of tri- and hexahydrate with a mass fraction of 26.6% at -73 °C, and of hexahydrate and ice with a mass fraction of 23.0% at -75 °C. In addition, a metastable eutectic is formed between trihydrate and ice with a mass fraction of 24.8% at -87 °C. Thus, in the concentration range from 0 to 25 %, a sharp decrease in melting point is observed. The vapor-liquid phase diagram between hydrogen chloride and water shows a negative azeotrope. The resulting azeotropic boiling point maximum is at 109 °C at normal pressure with a mass fraction of 20.2 %. During the evaporation of hydrochloric acid solutions with a concentration deviating from the azeotrope composition, the excess component is preferentially evaporated first, i.e., for hydrochloric acid with a mass fraction <20.2 %, concentration increases, and for hydrochloric acid with >20.2 %, concentration decreases until the constant boiling azeotrope composition is reached. The boiling curve in the phase diagram above the azeotrope composition correlates with the solubility curve of hydrogen chloride in water. At 25 °C, the mass fraction is 42%, which corresponds to "fuming" hydrochloric acid.
In water, hydrogen chloride dissociates completely; hydrochloric acid at 32% has a pH of -1. In moist air, hydrogen chloride gas forms a mist of fine droplets of hydrochloric acid. Diluted hydrochloric acid is a good electrical conductor.

When hydrochloric acid reacts with aqueous ammonia solution, a white smoke of ammonium chloride is formed.

HCl + NH3 → NH4Cl

Hydrochloric acid dissolves most metals with the exception of the precious metals and some others (for example, tantalum and germanium), forming chlorides and hydrogen, unless they are protected by passivation.

Mg + 2 HCl → MgCl2 + H2

It is very suitable for removing oxide layers on metals, since metal oxides react with hydrochloric acid to form chlorides and water:

CuO + 2 H2O → CuCl2 + H2O

Ammonium chloride can be obtained by neutralizing hydrochloric acid with aqueous ammonia solution:

NH3 + HCl → NH4Cl

A mixture of hydrochloric acid and nitric acid is called aqua regia because it is also capable of dissolving gold, the "king of metals." In addition to the oxidizing effect of the nitrosyl chloride and the nascent chlorine, the reduction of the effective gold ion concentration by complex formation also contributes to this:

Au3+ + 4 Cl- → AuCl4-

Hydrochloric acid is an important basic chemical with great significance in the chemical industry as an inorganic acid. It is used, for example, in the beneficiation of ores and rock phosphate. It is used to stimulate oil and gas wells, especially in carbonate deposits, but also in sandstone deposits. It is also used, for example, to remove calcium carbonate deposits from equipment and for cleaning after drilling with filter gravel pack and on boreholes themselves. In metalworking, it is used in pickling, etching, and brazing. In addition, diluted hydrochloric acid is used in construction to remove mortar residues from masonry - so-called acidizing. Tile layers use diluted hydrochloric acid to remove the lime film on tiles after grouting.
Hydrochloric acid is also an important reagent in chemical analysis. It is capable of separating a group of metals that form sparingly soluble chlorides from other metals by precipitation. These can then be further analyzed separately (see hydrochloric acid group). Alkalimetry is another field of application for hydrochloric acid.
As a food additive, hydrochloric acid bears the designation E 507.
In the pharmaceutical industry, hydrochloric acid is used to convert basic drugs that are poorly soluble or insoluble in water (examples: ciprofloxacin, citalopram, clenbuterol, clindamycin, dibenzepine) into more readily soluble hydrochlorides.
One of the most important uses of hydrochloric acid is in steel pickling to remove rust or iron oxide scale from iron or steel prior to subsequent processing, such as extrusion, rolling, electroplating, and other techniques.

Fe2O3 + Fe + 6 HCl → 3 FeCl2 + 3 H2O

In the steel pickling industry, hydrochloric acid regeneration processes such as the spray roaster or the fluidized bed HCl regeneration process have been developed to recover HCl from spent pickling liquid. The most common regeneration process is the pyrohydrolysis process:

4 FeCl2 + 4 H2O + O2 → HCl + 2 Fe2O3

By recovering the spent acid, a closed acid cycle is created. The iron(III) oxide by-product of the regeneration process is valuable and is used in a variety of secondary industries.
In normal acid-base reactions, hydrochloric acid can be used to produce numerous products that result in inorganic compounds. These include water treatment chemicals such as ferric chloride and polyaluminum chloride.

Fe2O3 + 6 HCl → 2 FeCl3 + 3 H2O

Iron(III) chloride and also polyaluminum chloride are used as flocculants in wastewater treatment, drinking water production and paper manufacturing.
Other inorganic compounds produced with hydrochloric acid include calcium chloride as road salt, nickel(II) chloride for electroplating, and zinc chloride for electroplating and battery manufacturing.

CaCO3 + 2 HCl → CaCl2 + CO2 + H2O

Biological significance
In humans and animals, hydrochloric acid is a component of gastric juice, where it causes, among other things, the denaturation of proteins, but also serves to kill microorganisms before entering the wider digestive system. It also creates the acidic environment in which the digestive enzyme pepsin is most effective.

Hydrochloric acid is detected firstly by its acidic character. In addition, the chloride anion is identified in a very diluted solution (if there is an excess of chloride ions, a soluble dichloroargentate complex is formed) by adding silver nitrate solution, whereby poorly soluble silver chloride precipitates:

HCl + AgNO3 → HNO3 + AgCl

If the resulting white precipitate dissolves in dilute ammonia water to form a complex, the evidence is that chloride ions were involved:

AgCl + 2 NH3 → [Ag(NH3)2]+ + Cl-

AgCl + HCl → [Ag(Cl2)]- + H+ (equilibrium)

When hydrochloric acid is heated with manganese dioxide (manganese dioxide), chlorine is formed:

4 HCl + MnO2 → Cl2 + MnCl2 + 2 H2O

The hydrochloric acid content of a solution is determined by titration with sodium hydroxide solution (acidimetry, dimensional analysis). Photometrically, this determination as well as that of chlorides can be carried out using the mercury salt of chloranilic acid. The content of hydrochloric acid in gastric juice is determined using Günzburg's reagent.