Definition

Noun: 1. An insoluble white powder: A chemical compound that is the calcium salt of stearic acid and palmitic acid. It is a common component of soap scum and is used industrially as a release agent, lubricant, and plastic stabilizer. 2. A component of soap scum: The substance formed as a precipitate when soap (sodium or potassium stearate) reacts with calcium ions present in hard water.

Usage Examples

• The formation of calcium stearate is why soap doesn't lather well in hard water.
• Calcium stearate is added to some plastics and concrete mixes to act as a lubricant and water repellent.
• The white ring in your bathtub is often composed of calcium stearate.

Advanced Usage

• In industrial contexts: The term is used precisely to refer to the specific compound (Ca(C₁₈H₃₅O₂)₂) employed in manufacturing. For example: "The formula uses calcium stearate as a flow agent to prevent the powder from caking."
• In chemistry and domestic contexts: It is used to describe the insoluble product of a metathesis reaction between soluble soap and calcium salts. For example: "The scum is calcium stearate, resulting from the reaction of sodium stearate with calcium bicarbonate."

Variants and Related Words

• Calcium soap: A more general term that can refer to calcium stearate or similar salts of fatty acids.
• Stearic acid: The fatty acid from which calcium stearate is derived.
• Metal stearate: A broader class of compounds including magnesium stearate or zinc stearate, which have similar applications.

Synonyms

• Calcium octadecanoate (IUPAC name)
• Soap scum (in the specific context of domestic hard water residue)

Related Phrases/Idioms

• "Hard water scum": This phrase often implicitly refers to the precipitate containing calcium stearate.
• "Soap reacts with hard water": This common description of a domestic phenomenon typically has the formation of calcium stearate as its chemical result.

Noun

1. an insoluble calcium salt of stearic acid and palmitic acid; it is formed when soap is mixed with water that contains calcium ions and is the scum produced in regions of hard water