Calcium Hydroxide: A Versatile Alkaline Compound

Calcium hydroxide, commonly known as slaked lime, is a widely used inorganic compound recognized for its strong alkaline properties. It plays a crucial role in construction, water treatment, agriculture, and various chemical processes due to its reactivity and relative safety compared to other strong bases.

---

Chemical Identity

• Chemical Formula: Ca(OH)₂

• Molecular Weight: 74.09 g/mol

• CAS Number: 1305-62-0

• Common Names: Slaked lime, hydrated lime, caustic lime

• IUPAC Name: Calcium hydroxide

---

Physical and Chemical Properties

• Appearance: White powder or crystalline solid

• Solubility: Slightly soluble in water (forms limewater)

• pH of Aqueous Solution: ~12.4 (saturated solution)

• Melting Point: Decomposes at ~580°C (to CaO and H₂O)

• Odor: Odorless

• Stability: Stable under normal conditions but reacts with carbon dioxide in the air

When dissolved in water, calcium hydroxide forms a suspension known as limewater, which is often used as a test for carbon dioxide gas (forming a white precipitate of calcium carbonate upon reaction).

---

Production

Calcium hydroxide is typically produced by the hydration of calcium oxide (quicklime):

CaO + H₂O → Ca(OH)₂ + heat

This exothermic reaction is known as slaking and results in a fine, white powder with many practical uses.

---

Key Applications

1. Construction Industry

• Used in mortar, plaster, and whitewash

• Plays a key role in the setting of cement and concrete

• Helps improve the plasticity and workability of mixtures

2. Water and Wastewater Treatment

• Serves as a flocculant and pH adjuster in water purification

• Precipitates heavy metals and neutralizes acidic wastewater

3. Agriculture

• Acts as a soil amendment (agricultural lime) to reduce acidity

• Enhances nutrient availability and improves soil structure

4. Chemical Industry

• Intermediate in the production of other calcium compounds

• Used in the manufacture of sodium hydroxide via the causticizing process

5. Food Industry

• Permitted as a food additive (E526) for pH control

• Used in the preparation of corn tortillas (nixtamalization) and other food processing tasks

6. Environmental Uses

• Treats acid mine drainage

• Reduces sulfur dioxide emissions from flue gases in scrubbers

---

Safety and Handling

Calcium hydroxide is corrosive to skin and eyes in concentrated form but is generally considered safer than many other strong bases.

Hazards:

• Can cause skin irritation, eye damage, and respiratory issues upon prolonged exposure

• Dust may cause irritation to the respiratory tract

Precautions:

• Use protective gear: gloves, goggles, and dust mask

• Avoid inhaling dust or contact with skin and eyes

• Store in dry, well-ventilated areas in tightly sealed containers

---

Environmental Impact

Though not toxic in small amounts, calcium hydroxide can disrupt aquatic ecosystems if released in large quantities due to its high alkalinity. It reacts readily with atmospheric CO₂ to form calcium carbonate, which is environmentally benign.

---

Conclusion

Calcium hydroxide is a highly useful and accessible compound that bridges the worlds of construction, agriculture, industry, and environmental management. Its mild yet effective alkalinity, low cost, and broad versatility make it a staple in both traditional and modern applications. However, safe handling is essential to avoid irritation and maintain environmental stewardship.

Contact Us

Phone : +49 1512 4714765 ( Germany )
Phone : +1 (702) 381-3042 ( USA )
Email : [email protected]
Address : Cunostraße 56, 14193 Berlin. Germany
Address : 7373 Rowlett Park Dr, Tampa, FL 33610, United States.