Hydrochloric acid solution, a clear colorless liquid, is a solution of hydrogen chloride gas dissolved in water. It is a strong inorganic acid.

Hydrochloric acid solution (HCl solution) is mainly used to adjust the pH in cell culture medium.[1]
It can also be used:

• In the extraction of elderberry anthocyanins by endothelial cells.[2]
• To convert iron(III) perchlorate to Fe(III) ions which can then form a complex with acetohydroxamic acid (FeAHA).[3]

The hydrochloric acid solution has been used:

• to acidify the surface water sample and to prevent interference from carbonate concentrations up to 10 mg L-1 with organic carbon detector (OCD) detection
• to adjust the pH of complete transfection media for transfection with chitosan/pDNA nanoparticle complexes
• to prepare artificial tear solution (ATS) to incorporate the fluorescently tagged cholesteryl ester

Hydrochloric acid (HCl) is commonly used in research and large-scale applications. Its large-scale applications include the refinement of ore to produce tin and tantalum, the cleaning of metal products, and the hydrolysis of starch and proteins in the production of food products. HCl is also used in chemical synthesis. It can also be used in hydrolyzing samples for chromatographic analysis, such as in matairesinol, in flax seed, glycopeptides, κ-carrageenan derived oligosaccharides, and syn- and anti-1,3-diols. HCl is also used as a bleaching agent to neutralize alkaline agents in the food, textile, metal, and rubber industries.