"Spirits of Salts" is a commercial name for a strong, concentrated solution of hydrochloric acid (HCl), also known as muriatic acid, used as a powerful heavy-duty cleaner for unblocking drains and removing limescale and cement from various surfaces. It is highly corrosive and requires careful handling with appropriate personal protective equipment (PPE) like gloves and eye protection, and should not be used on sensitive surfaces or mixed with other chemicals. 
Uses
Unblocking drains:
It effectively dissolves blockages caused by grease, hair, soap scum, and organic materials in toilets and external pipes. 
Descaling:
Its primary function is to remove stubborn limescale and hard water deposits. 
Cleaning surfaces:
It can be used to clean bricks, concrete, and masonry by removing excess cement and other stains. 
Industrial applications:
It is used in industries like breweries, milk parlors, and abattoirs for cleaning and removing deposits. 
Safety Precautions
Corrosive:
Spirits of Salts causes severe skin and eye damage, so it's crucial to wear protective gloves (neoprene, latex, nitrile, or PVC), goggles, and other appropriate PPE. 
Ventilation:
It should be used outdoors or in well-ventilated areas to avoid inhaling harmful vapors. 
Do not mix:
Never mix Spirits of Salts with other cleaning products, especially not with caustic soda, as this can cause a dangerous and highly exothermic reaction. 
Rinsing:
Rinse any skin contact with water immediately. 
Age restriction:
Due to its hazardous nature, it is often an age-restricted product, with proof of ID required upon purchase. 
What to avoid
Metals:
Do not use Spirits of Salts on metals, as it will turn them black. 
Internal fixtures:
It is not suitable for internal household fixtures, including washbasins, baths, showers, and kitchen sinks, or for use with septic tanks.