What Is Calcium Hydroxide?
Calcium hydroxide, known as slaked lime, is a calcium hydroxide with various applications. Its aqueous solution, referred to as lime water, acts as a reagent to detect carbon dioxide.
Found naturally as portlandite, calcium hydroxide is produced industrially via the dry digestion method, involving the addition of water to calcium oxide, followed by digestion and evaporation of excess water.
Uses of Calcium Hydroxide
Primarily used as a coagulant in konjac, calcium hydroxide also adjusts pH levels in sugar and processed meats. In construction, it serves as a material for plaster and mortar. In leather manufacturing, its suspension, lime milk, treats hide surfaces. Additionally, it’s utilized in root canal treatments, as a neutralizer for waste gas and wastewater, and in agriculture to amend acidic soils and maintain sanitary conditions in livestock barns.
Properties of Calcium Hydroxide
This substance appears as a colorless crystal or white powder, soluble in glycerin but nearly insoluble in ethanol and ether. Its slight water solubility results in a strongly alkaline solution or suspension, though it is less soluble than alkali metal hydroxides, demonstrating weak basic action. The dissolution heat is exothermic, with solubility diminishing as temperature rises.
Despite being a strong base, calcium hydroxide is not considered a deleterious substance. It undergoes neutralization reactions with acids, such as the production of calcium chloride and water when reacting with hydrochloric acid.
Structure of Calcium Hydroxide
Calcium hydroxide forms an ionic crystal of hydroxide and calcium ions, creating hexagonal platelet crystals in water. Its formula is Ca(OH)2, with a molar mass of 74.0927 g/mol and a density of 2.211 g/cm3.
Other Information on Calcium Hydroxide
1. Reaction of Calcium Hydroxide
Blowing carbon dioxide into a saturated solution precipitates calcium carbonate, creating a cloudy white appearance. Excess carbon dioxide transforms calcium carbonate into soluble calcium bicarbonate, clearing the turbidity. Additionally, heating calcium hydroxide produces ammonia and decomposes at 580°C to calcium oxide. Chlorine absorption forms calcium hypochlorous acid.
2. Hazards of Calcium Hydroxide
Its aqueous solutions can harm mucous membranes and skin, posing severe risks to the eyes and potentially leading to blindness. Though neutralized by stomach acid, ingestion in large quantities can be harmful, affecting breathing, blood pressure, and organ function. Historically used in plague epidemics for its microorganism growth inhibition, safer calcium carbonate now replaces calcium hydroxide for creating white lines in schoolyards.