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Micri- (unit symbol mc-) is an archaic non-SI decimal metric prefix for 10−14.[1]

It was proposed as a prefix for the CGS-unit of energy, the erg. The micrierg was proposed in 1922 by William Draper Harkins as a unit of energy equating to 10−14 erg,[1][2][3][4][5][6] the equivalent to 10−21 joule, as a convenient unit to measure the surface energy of molecules[5] in surface chemistry.[7] It saw limited use. One electronvolt is about 160 micriergs. In 1991, the micrierg was officially designated the zeptojoule when the zepto- prefix for 10−21 was officially adopted.


  1. ^ a b Cardarelli, François (2003). Encyclopaedia of Scientific Units, Weights and Measures. Springer-Verlag London Ltd. ISBN 978-1-4471-1122-1.
  2. ^ Roberts, Lathrop Emerson; Harkins, William Draper; Clark, George Lindenberg (2013-07-01) [1922]. The Orientation of Molecules in Surfaces, Surface Energy, Adsorption, and Surface Catalysis. V. The Adhesional Work Between Organic Liquids and Water: Vaporization in Steps as Related to Surface Formation. University of Chicago Digital Preservation Collection. University of Chicago. Retrieved 2015-08-25.
  3. ^ Holmes, Harry N. (1925). Colloid Symposium Monograph - Papers Presented at the Second National Symposium on Colloid Chemistry, Northwestern University, June, 1924. Vol. 2. The Chemical Catalog Company, Inc. Retrieved 2015-02-15.
  4. ^ "Journal of the American Chemical Society - Issues for 1898-1901 include Review of American chemical research, v. 4-7; 1879-1937, the society's Proceedings". Journal of the American Chemical Society. American Chemical Society. 44: 665. 1922. ISSN 0002-7863. Retrieved 2015-02-15.
  5. ^ a b Jerrard, H. G.; McNeill, D. B. (2012-06-12) [1963]. A Dictionary of Scientific Units - Including dimensionless numbers and scales (5 ed.). Chapman and Hall Ltd., reprint: Springer Science & Business Media. ISBN 978-9400941113. Retrieved 2015-02-15.
  6. ^ Partington, James Riddick (2010-02-17) [1949]. An Advanced Treatise on Physical Chemistry: Fundamental principles. The properties of gases. Vol. 1. Longmans, Green. Retrieved 2015-08-25.
  7. ^ Cardarelli, François (1999) [1966]. Scientific unit conversion: A practical guide to metrication (2 ed.). Springer-Verlag London Limited. doi:10.1007/978-1-4471-0805-4. ISBN 978-1-85233-043-9. Retrieved 2015-08-25.