pH regulators

Chemical reagents that regulate pH

In chemical terms, pH regulators include acids, bases, mixtures and buffers, whose task is to precisely control the activity of H⁺ ions in solutions. Their action is based on the transformation of acid-base equilibrium, which in practice involves neutralising excess hydronium or hydroxyl ions through reactions with an acid or base, or by creating buffer systems that are based on the equilibrium of acid and base conjugates and minimise pH changes when an acid or base is added.

Neutralisation

The action of neutralising pH regulators is based on controlling the acid-base balance in aqueous systems by influencing the concentration and activity of hydrogen ions (H⁺) and hydroxyl ions (OH⁻). In the case of acidic regulators, the mechanism involves acid dissociation, leading to an increase in the concentration of H⁺ ions, which results in a decrease in the pH of the solution. Alkaline regulators, on the other hand, work by generating OH⁻ ions or binding H⁺ ions, causing an increase in pH.

Buffering

An important group of pH regulators are buffer systems, which consist of a conjugate pair: a weak acid and its conjugate base or a weak base and its conjugate acid. The buffering mechanism is based on the ability of the system to react with both excess H⁺ and OH⁻ ions, which limits pH changes when small amounts of acids or bases are added. The behaviour of a buffer system is described by the Henderson–Hasselbalch equation, which relates the pH value to the logarithm of the ratio of the concentrations of the dissociated and undissociated forms and to the value of the acid dissociation constant (pKₐ).

Stoichiometry and equilibrium

In practical industrial formulations, pH regulation mechanisms often also include neutralisation reactions, in which acids and bases react stoichiometrically, leading to the formation of salts and water. This process allows for quick and permanent adjustment of the desired pH, but does not ensure the system’s resistance to further pH changes, unlike buffer systems. Therefore, the choice of pH regulator depends not only on the target pH value, but also on the required stability of the reaction over time and resistance to external factors such as dilution, temperature or the presence of other reagents.

Examples of pH regulators and their applications

• Caustic soda (flakes) and NaOH solutions – a strong base used to increase pH, neutralise acids and maintain an alkaline environment.
• Hydrochloric acid – a strong acid used to lower pH and acidify systems.
• Diethylamine – a substance from the group of alcohol amines with an alkalising effect, used in specific chemical systems where alkalinity regulation must be compatible with other components.
• Tensamin EC/OS – mixtures of active substances that combine corrosion protection and pH stabilisation.
• Fertiliser lime – a mineral product that regulates the pH of soil and solutions, helping to maintain an alkaline pH.