Definition
Potassium stearate is the potassium salt of stearic acid, a long‑chain fatty acid. It is a metal soap commonly used as a surfactant, emulsifier, and lubricant in various industrial and consumer applications.
Overview
Potassium stearate appears as a white, waxy solid that is slightly soluble in water and more soluble in organic solvents such as ethanol and ether. The compound functions as an anionic surfactant, lowering surface tension in aqueous systems. It is employed in the manufacture of soaps, cosmetics, detergents, rubber processing, and as a release agent in pharmaceutical tablet formulation. Because of its fatty‑acid component, it also serves as an anticaking agent in powders and as a stabilizer in food‑grade applications.
Etymology / Origin
The name derives from its constituent parts: “potassium” indicating the K⁺ cation, and “stearate,” the anion formed from stearic acid (from the Greek stéar meaning “tallow”). The compound is synthesized by neutralizing stearic acid with potassium hydroxide or potassium carbonate.
Characteristics
- Chemical formula: C₁₈H₃₅KO₂
- Molar mass: ≈ 306.55 g·mol⁻¹
- Physical state: White, waxy solid at room temperature
- Solubility: Slightly soluble in water (~0.1 g L⁻¹ at 25 °C); readily soluble in organic solvents
- pH of aqueous solution: Basic, due to the presence of the potassium ion
- Melting point: Approximately 88–92 °C (depending on purity)
- Uses:
- Detergent and soap additive (as a surfactant)
- Emulsifier in cosmetics and personal‑care products
- Lubricant and release agent in rubber and plastics processing
- Anticaking agent in powdered foods and pharmaceuticals
- Stabilizer in lubricating greases and metalworking fluids
Related Topics
- Stearic acid: The parent fatty acid (C₁₈H₃₆O₂) from which potassium stearate is derived.
- Metal soaps: Salts of fatty acids with metal cations (e.g., calcium stearate, sodium stearate) used for similar functional purposes.
- Surfactants: Compounds that reduce surface tension, classified as anionic, cationic, nonionic, or amphoteric.
- Emulsifiers: Agents that stabilize mixtures of immiscible liquids, frequently employed in food and cosmetics.
- Detergents: Cleaning formulations that often contain anionic surfactants such as potassium stearate.
All information presented is based on established chemical literature and industrial usage data.