Colloid Definition - Chemistry Glossary

Fluorescent colloid mixtures
These tubes contain colloidal mixtures displaying luminescence.

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By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on September 04, 2019

A colloid is a type of homogeneous mixture in which the dispersed particles do not settle out. The insoluble particles in the mixture are microscopic, with particle sizes between 1 and 1000 nanometers. The mixture may be termed a colloid or a colloidal suspension. The phrase "colloidal solution" is incorrect. Sometimes the term "colloid" only refers to the particles in the mixture and not the entire suspension.

Colloids may be translucent due to the Tyndall effect, where light is scattered by particles in the mixture.

Examples of Colloids

Colloids may be gases, liquids, or solids. Examples of familiar colloids include butter, milk, smoke, fog, ink, and paint. Cytoplasm is another example of a colloid.

Source

  • Levine, Ira N. (2001). Physical Chemistry (5th ed.). Boston: McGraw-Hill. p. 955. ISBN 978-0-07-231808-1.
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Helmenstine, Anne Marie, Ph.D. "Colloid Definition - Chemistry Glossary." ThoughtCo, Aug. 28, 2020, thoughtco.com/definition-of-colloid-chemistry-glossary-605840. Helmenstine, Anne Marie, Ph.D. (2020, August 28). Colloid Definition - Chemistry Glossary. Retrieved from https://www.thoughtco.com/definition-of-colloid-chemistry-glossary-605840 Helmenstine, Anne Marie, Ph.D. "Colloid Definition - Chemistry Glossary." ThoughtCo. https://www.thoughtco.com/definition-of-colloid-chemistry-glossary-605840 (accessed June 8, 2023).