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Calcium hydroxide, known for its common names such as slaked lime or hydrated lime, appears as a white, odorless solid at room temperature. This compound holds a molecular formula of Ca(OH)2 and a molecular weight of 74.09 g/mol. Industry often relies on its particular properties which allow it to serve many purposes. The substance exists in several forms including powder, flakes, and even as a suspension in water. Its crystalline structure and specific gravity—about 2.24—highlight both its stability and practicality for transport and storage. Solid calcium hydroxide does not dissolve easily in water, and what does dissolve creates a solution known as limewater, recognized for its slight solubility and alkaline nature.
Calcium hydroxide forms a basic compound, producing a highly alkaline solution when introduced to water, with a pH around 12.4. The compound is sparingly soluble—about 1.73 grams dissolve in a liter of water at room temperature. Chemically, the structure sees each calcium ion surrounded by two hydroxide ions, arranged in line with its crystalline form. This contributes to the material’s firm texture when pure, whether it comes as powder, pearls, or flakes. Application exposure often means encountering a chalky, dense powder or rugged off-white lumps, depending on manufacturing or raw materials. Safe handling always calls for gloves and protective eyewear since the high pH can irritate or damage human tissue, especially sensitive skin and eyes.
With respect to formal specifications, calcium hydroxide adheres to a purity standard of 95% or higher for most industrial uses. The HS Code, for global trade, falls under 28259010—used for customs classification and shipping documentation. Material testing generally covers particle size, which frequently ranges from fine mesh powders to granulated or flaky forms. In construction, it finds use in mortar blends and soil stabilization and supports the production of other compounds, such as calcium stearate and bleaching powder. Water treatment plants employ it to balance pH and remove impurities, while the food industry looks for 'food-grade' certification where lime appears as E526—to adjust acidity or begin certain food-processing reactions. The key property here is reactivity with acids and carbon dioxide, which leads to precipitation or neutralization.
Safety always takes priority, since contact with calcium hydroxide can cause burns, irritation, or severe damage with extended exposure. Dust inhalation brings risks to lungs and airways, so workplaces stick to dust control measures and maintain strict air quality limits. As for hazardous characteristics, calcium hydroxide lacks combustibility and picks up little environmental harm compared to other chemicals. Its main hazard relates to water alkalinization or accidental spills—both manageable with common neutralization procedures. Regulatory agencies, including OSHA and the European Chemicals Agency, classify calcium hydroxide as hazardous, and require safety data sheets (SDS) outlining safe storage, handling, and disposal. Any workplace using it carefully manages personal protective equipment (PPE) and maintains wash stations for emergencies.
Limestone (calcium carbonate) provides the essential raw material for calcium hydroxide production. Factories heat limestone to produce quicklime (calcium oxide), which reacts with water in a process called slaking, yielding calcium hydroxide. Modern manufacturing controls temperature and hydration rates to guarantee consistent crystal size and product purity. Industrial users check that every batch meets standardized density, particle size, and purity levels. Common packaging options include watertight bags or steel drums, as safeguarding from humidity prevents clumping and loss of reactivity.
Calcium hydroxide does offer versatility in both liquid and solid formats. Builders often choose powder or flakes for onsite application, while laboratories prepare saturated lime solutions for titrations or material testing. Municipal water utilities keep stock in both bulk solid and slurry tanks, depending on scale of use and need for automation or manual handling. Pearls and pellets, less common, find use where measured reactivity ensures safe metering over time, such as in specialized reactors or controlled feed systems within closed pipelines. Proper ventilation and environmental controls remain necessary across all handling situations, reducing airborne dust and avoiding unwanted reactions with atmospheric CO2.
Personal encounters with calcium hydroxide usually involve construction dust, the fresh surface of a lime-plastered wall, or even the subtle taste adjustment in canned foods. Its value comes through in the range of use-cases: fields such as environmental engineering, construction, chemistry, and agriculture all see benefit. Better handling practices, modern material science, and improved PPE make both raw materials and finished products safer than in past decades. Looking to the future, investments in dust-free packaging, automated dispensing, and process monitoring continue reducing workplace risk and boosting product performance. The broad, dependable character of calcium hydroxide means the chemical shows up in both history’s oldest buildings and today’s most advanced industries.
West Ujimqin Banner, Xilingol League, Inner Mongolia, China
