Calcium hydroxide

Calcium hydroxide (CAS 1305-62-0), commercially known as slaked lime or hydrated lime, is a strong inorganic base. Also known as E526.

Where is Calcium hydroxide used?

• Food processing: pH regulator, firming agent and alkali source; nixtamalization of corn for tortilla production; firming of fruit and vegetable textures in pickling and canning
• Water treatment: pH adjustment, precipitation of heavy metals and softening of hard water through coagulation and flocculation
• Construction: mortars, plasters and soil stabilization
• Pulp and paper: causticizing, regenerating sodium hydroxide from green liquor in the kraft pulping cycle
• Agriculture: neutralization of acidic soils and raising of pH value.
• Desulfurisation of flue gases from thermal power plants or other industries emitting acid gases.
• Treatment of wastewater or various industrial wastes, for example to neutralise pH or precipitate heavy metals.
• Plant care: combatting of certain fungal diseases.

Good to know: Food and pharmaceutical grades are held to tighter specifications than construction or agricultural material.

Formulation notes

• Must be stored separately from strong acids.
• Reacts violently with acids.

Typical specification

• High-calcium hydrated lime refers to a product containing a maximum of 5% magnesium hydroxide.
• Also available as a slurry ready for use in industrial applications.
• Available as a powder in sacks or in bulk.

Regulatory status

• Classified as FDA GRAS under 21 CFR 184.1206.

Storage, packaging and handling

• Attacks many metals in the presence of water, producing flammable/explosive hydrogen gas.

Frequently asked questions about Calcium hydroxide

What is the role of calcium hydroxide in wastewater treatment?

It promotes phosphate precipitation in wastewater, preventing eutrophication.

How does calcium hydroxide affect freshwater pipes?

It is used in freshwater treatment to raise the pH of water so that pipes do not corrode where the base water is acidic, as it is self-regulating and does not raise the pH too much.

What purity do beverage manufacturers require?

Beverage manufacturers require high-purity calcium hydroxide with ≥95% purity.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.