Hydrochloric acid

Strong mineral acid, an aqueous solution of hydrogen chloride, sold commercially as muriatic acid.

Characteristics

Strong acid, fully dissociated in water into chloride and hydrogen ions.
Highly corrosive to skin, eyes, mucous membranes and many metals.
Cited in irrigation literature among acids used to lower water pH and alkalinity.
Dissolves carbonates, releasing carbon dioxide.

Role in the preparation: Its role is chemical: lowering the pH or neutralizing the alkalinity (bicarbonates) of water or a solution.

Caution: Always add acid to water, never the reverse, wear nitrile gloves, goggles and a face shield, work with ventilation and store away from bases, bleach and metals.

Sources: UC Santa Barbara – Standard Operating Procedure: Hydrochloric Acid · UC Nursery and Floriculture Alliance – Soil and Water pH, Part 5

Documentary information: this is neither a recommendation for use nor a plant-protection or veterinary claim. Check your country's regulations before any use.