Chemical Properties: Hydrated lime is a white, powdery substance that is sparingly soluble in water. Its chemical formula is Ca(OH)2. When mixed with water, it forms a clear, colorless solution known as lime water, which is weakly alkaline.
Production: Hydrated lime is produced by adding water to quicklime or calcium oxide, causing it to undergo an exothermic reaction and form calcium hydroxide. This process is called slaking.
Alkalinity: Hydrated lime is a weak base, and its aqueous solution is alkaline. It has a pH value ranging from 12 to 12.5 in water.
Solubility: While hydrated lime is sparingly soluble in water, it readily reacts with water to form a saturated solution of calcium hydroxide. This solution is commonly referred to as lime water.
Chemical Reactivity: Hydrated lime is reactive with acids, and it undergoes neutralization reactions when combined with acidic substances.
Absorption of Carbon Dioxide: Hydrated lime has the ability to absorb carbon dioxide (CO2) from the atmosphere, converting back to calcium carbonate (CaCO3). This process is known as carbonation or carbonation curing.
Industrial Applications:
- Water Treatment: Hydrated lime is used in water treatment processes for pH adjustment, coagulation, and precipitation of impurities. It can help in the removal of metals, phosphates, and sulfates from water.
- Construction: It is used in the construction industry for soil stabilization, particularly in road construction and building foundations. Hydrated lime can improve the plasticity and workability of soil, reduce its plasticity index, and enhance its load-bearing capacity.
- Environmental Remediation: Hydrated lime is used in environmental remediation projects for soil and groundwater treatment, such as neutralizing acidic soil or wastewater.
- Chemical Manufacturing: It is used as a raw material in the production of various chemicals, including calcium stearate, calcium hypochlorite, and calcium aluminate.
- Food Industry: Hydrated lime is used in food processing as a pH regulator and firming agent, particularly in the production of pickles, canned fruits, and vegetables.
- Sugar Refining: It is utilized in sugar refining processes for the purification and clarification of sugar juices.
- Paper and Pulp Industry: Hydrated lime is used in the paper and pulp industry for bleaching, pH adjustment, and waste treatment processes.
- Flue Gas Desulfurization (FGD): Hydrated lime is used in FGD systems to remove sulfur dioxide (SO2) from flue gases emitted by power plants and industrial facilities.
Safety Considerations:
- While hydrated lime is less caustic and less reactive than quicklime, it can still cause irritation or burns upon contact with skin, eyes, or mucous membranes. Proper handling procedures and personal protective equipment should be used when working with hydrated lime.
- Inhalation of hydrated lime dust can irritate the respiratory tract. Dust control measures and proper ventilation should be employed in areas where hydrated lime is handled or processed.
- Spills should be promptly cleaned up using appropriate neutralizing agents and procedures.
| Items | Specifications |
| Chemical Formula | Ca(OH)₂ |
| Appearance | White, powdery solid |
| Solubility | Sparingly soluble in water |
| Density | ~2.21 g/cm³ |
| Melting Point | Decomposes at high temperature |
| pH | Alkaline, pH ~ 12-13 |
| Odor | Odorless |
| Hazard Class | Irritant, Avoid Inhalation and Eye Contact |
| Common Uses | Water treatment, pH adjustment in |
| industrial processes, soil stabilization, |
| construction, and in manufacturing various |
| chemicals, such as calcium stearate and |
| calcium hypochlorite |
| Safety Precautions | Wear protective clothing, gloves, and goggles. |
| Avoid inhalation of dust. |
| Storage | Store in a dry, well-ventilated area away from |
| incompatible substances. Keep containers tightly |
| closed. |
| Reactivity | Reacts with acids to produce water and calcium |
| salts. Can cause irritation upon contact with |
| skin and eyes. |
| Environmental | Generally not considered hazardous to the |
| Impact | environment if handled and disposed of properly. |
| Avoid contamination of water sources. |
ECHEMI Editorial Reference
C18-21 Alkane is a mixture of alkanes with 18 to 21 carbons in the alkyl chain.
Distillates (petroleum), hydrotreated middle is a complex combination of hydrocarbons obtained by treating a petroleum fraction with hydrogen in the presence of a catalyst. It consists of hydrocarbons having carbon numbers predominantly in the range of C11 through C25 and boiling in the range of approximately 205.degree.C to 400.degree.C (401.degree.F to 752.degree.F).
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