Definition

1. Noun:
   • A light-sensitive coating used in photography: An emulsion is a mixture applied to photographic paper or film. It contains tiny light-sensitive crystals (typically silver halides like silver bromide) suspended in a gelatin layer. When exposed to light, these crystals undergo a chemical change, forming a latent image that can be developed into a visible photograph.
   • A type of colloid in chemistry: In chemistry, an emulsion is a specific kind of colloid where both the dispersed phase and the dispersion medium are liquids. Typically, this involves two liquids that do not normally mix, such as oil and water, with one being broken into tiny droplets and suspended in the other. A stabilizing agent (an emulsifier) is often needed to prevent the liquids from separating.

Examples of Usage

• Noun:
  • The photographic emulsion on this film is very fine-grained, allowing for high-resolution images.
  • Mayonnaise is a common example of a food emulsion, where oil is dispersed in water (from vinegar and egg yolk).
  • The chemist created a stable oil-in-water emulsion for the new cosmetic formula.

Advanced Usage

• "To break an emulsion": This phrase describes when an emulsion separates back into its original, unmixed liquid components. This can happen due to age, temperature changes, or chemical interference.
  • Adding too much salt caused the salad dressing emulsion to break.
• "Emulsion paint": A common type of paint where pigment particles are suspended in a water-based polymer emulsion. It dries to form a coating.
  • We used a white emulsion paint for the bedroom walls.

Variants and Related Words

• Emulsify (verb): To make an emulsion by mixing two immiscible liquids.
  • Use a blender to emulsify the oil and vinegar for the vinaigrette.
• Emulsifier (noun): A substance that stabilizes an emulsion, such as lecithin in egg yolks.
  • Lecithin is a natural emulsifier used in many processed foods.
• Emulsive (adjective): Having the properties of or relating to an emulsion.

Synonyms

• Dispersion: A more general term for a mixture where particles are distributed throughout a medium.
• Colloid: A broader scientific category for mixtures where one substance is evenly dispersed in another (includes emulsions, foams, gels).
• Mixture: A general term for combining two or more substances without chemical bonding.

Related Phrases

• "Water-in-oil emulsion": An emulsion where water droplets are dispersed in a continuous oil phase. Butter is an example.
  • This cold cream is a water-in-oil emulsion.
• "Oil-in-water emulsion": An emulsion where oil droplets are dispersed in a continuous water phase. Milk is an example.
  • Most lotions are oil-in-water emulsions.

Related Idioms

(Note: There are no common idioms directly centered on the word "emulsion." It is primarily a technical term used in science, photography, and cooking.)

Noun

1. a light-sensitive coating on paper or film; consists of fine grains of silver bromide suspended in a gelatin
2. (chemistry) a colloid in which both phases are liquids
   • an oil-in-water emulsion