subnatantadj.n.
/ˌsʌbˈneɪt(ə)nt/, U.S. /ˌsəbˈneɪtnt/ A. adj.† 1. Chiefly in the terminology of Erasmus Darwin: designating an animal that habitually swims or floats below the surface of the water. Obsolete. rare.
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1794 E. Darwin Zoonomia I. 500 As in the production of the butterfly with painted wings from the crawling caterpillar; or of the respiring frog from the subnatant tadpole.
1798 J. Brown Observ. Darwin's Zoonomia §xix. 465 The fish did not become a subnatant animal, by having received fins; as it must have been an inhabitant of the water, before it could have felt the want of them.
1807 in Spirit of Public Jrnls. (1808) 11 84 I swam with subnatant tadpoles, I frisked with volatile newts.
2. Chiefly Chemistry and Biochemistry. Of a liquid: lying beneath a floating layer of solids or a less dense liquid; (also, of a solid) forming a precipitate beneath a liquid (rare). Cf. supernatant adj. 1a.
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1843 M. H. Boye & F. Leaming tr. J. J. Berzelius Kidneys & Urine 84 If the distillation be interrupted before all the ether has been distilled, the ether will be found to be much more coloured than the subnatant water [Ger. das darunter stehende Wasser].
1895 A. M. Hart Diet in Sickness & Health 41 The cocoa nibs are slowly boiled or stewed for several hours, and the subnatant fluid is poured off.
1916 Chem. Abstr. 10 Aug. 2008 The subnatant acid layer of the butter.
1918 T. B. Robertson Physical Chem. Proteins i. iii. 63 Prepared by..removing the fluid from the subnatant crystals and keeping in a well-stoppered container.
1963 Arch. Biochem. & Biophysics 102 203/1 The mixture separated into a supernatant layer containing the organic solvent, a subnatant aqueous layer, and an intermediary semisolid interphase layer.
2010 L. K. Wang et al. Flotation Technol. viii. 273 The subnatant liquor is recycled to the head of the sewage treatment plant for further treatment with the incoming wastewater flow.
B. n.
Chiefly Chemistry and Biochemistry. A subnatant liquid.
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1951 Amer. City 66 15/3 Carbon dioxide is generated that lifts the sludge to the surface. The ‘subnatant’ then can be drawn off.
1981 Aquatic Bot. 11 188 After 30 min a major fraction of the algal cells (ca. 90%) were flocculated, leaving an almost clear subnatant.
2003 P. Walstra Physical Chem. Food xiii. 507 At a given moment all of the larger particles can be in the cream layer, whereas most of the smaller ones are still in the subnatant.
This entry has been updated (OED Third Edition, June 2012; most recently modified version published online March 2022).
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adj.n.1794