tithonicityn.
/ˌtɪθə(ʊ)ˈnɪsᵻti/, /ˌtʌɪθə(ʊ)ˈnɪsᵻti/, U.S. /ˌtɪθəˈnɪsᵻdi/, /ˌtaɪθəˈnɪsᵻdi/ Photography. Now historical.
In the terminology of John William Draper: the property by which solar radiation causes photochemical change, as in traditional photography. Cf. actinism n. 1, tithonic adj.
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the world > matter > physics > electromagnetic radiation > solar radiation > [noun] > property causing chemical change
tithonicity1842
actinism1845
tithonism1855
1842 J. W. Draper in London, Edinb., & Dublin Philos. Mag. 21 455 The proof of the physical independence of Tithonicity and Light.
1855 J. Scoffern in Orr's Circle Sci.: Elem. Chem. 93 The immediate mode of agency of the power—‘actinism’, ‘tithonicity’, ‘energia’, or whatever we may call it—is..unknown.
1912 Sci. Progress 6 662 Solar light was regarded as composed of at least three imponderable agencies—light, heat and tithonicity or the power to bring about chemical changes.
2005 Stud. Hist. & Philos. Sci. A 36 499 Draper's arguments for the independence of tithonicity from heat were quite brief, since few had ever suggested that they could be identical.
This entry has been updated (OED Third Edition, January 2018; most recently modified version published online March 2022).
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n.1842