Why alkalis are more caustic than acids

2. Examples of irritating and corrosive substances

2.1 Acids and alkalis (bases)

Examples of strong acids are sulfuric acid, hydrochloric acid, nitric acid, peracetic acid (PES) and formic acid. Hydrochloric acid is also known as hydrochloric acid.

Strong alkalis are z. B. caustic soda and potassium hydroxide. Caustic soda can be made by dissolving solid caustic soda (sodium hydroxide lumps) in water. Caustic solutions are also known as bases. Ammonia, which is gaseous at room temperature, dissolves in water and a strongly alkaline ammonia solution is created, which is also known as "ammonia spirit".

A pH value is often given for acids and alkalis. Acids have pH values ​​from 0 to 7, alkalis from 7 to 14 (Fig. 2). In the case of lyes or bases, one speaks of a basic or alkaline effect. Pure water is neutral and has a pH value of 7. Normal life processes only take place between pH values ​​4 and 9.

Fig. 2: pH values, their effects and examples

The main factors that determine the corrosive effect of acids or alkalis are their strength and the concentration of their aqueous solution. Even with high dilution, strong acids and alkalis can still cause irritation.


    Acids and alkalis are the effective components of many cleaners.

    Cleaning agent for fatty residues such as B. Grill cleaners or smoke resin removers contain caustic soda. Drain cleaners contain caustic soda.

    Acids such as B. Citric acid or acetic acid are used in the food sector to loosen deposits such as scale, milk stone or beer stone.

    "Battery acid" is about 38% sulfuric acid.

2.2 Other irritating and corrosive substances

For example, in BGN member companies:

  • Ozone and chlorine for water treatment in hotel swimming pools,
  • Hydrogen peroxide and peracetic acid (see also ASI 8.03 "Handling peracetic acid") for disinfection during cold aseptic filling,
  • Velcorin® (Trade name; component: "dimethyl dicarbonate") as a cold disinfectant (see also ASI 8.07 "Velcorin®")
  • Glutaraldehyde as an additive in detergents.

Products with so-called "active oxygen" contain hydrogen peroxide.

"Active chlorine" products are solutions that can release chlorine, e.g. B. Chlorine hypochlorite, which contains sodium hypochlorite.

Irritant and corrosive hazardous substances can act on the skin in solid, liquid or gaseous form. As gases, vapors or aerosols, they can also damage the airways.

Caustic soda (sodium hydroxide chips or granules), quicklime (calcium oxide), slaked lime (calcium hydroxide)

Sodium hydroxide, chlorine bleach (sodium hypochlorite), ammonia solutions ("ammonia"), sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, formic acid, hydrogen peroxide solutions, formalin (formaldehyde solutions), lime water (strongly alkaline calcium hydroxide solution or slurry)

Gases / vapors:
Peracetic acid (PES), ammonia, hydrogen chloride, ozone, hydrogen peroxide, formaldehyde