Editing Standard state (section)

== Typesetting ==
{{Contains special characters|Uncommon Unicode|section}}
At the time of development in the nineteenth century, the superscript [[Plimsoll symbol]] (<sup>⦵</sup>) was adopted to indicate the non-zero nature of the standard state.<ref>Prigogine, I. & Defay, R. (1954) ''Chemical thermodynamics'', p. xxiv</ref> [[IUPAC]] recommends in the 3rd edition of ''[[Quantities, Units and Symbols in Physical Chemistry]]'' a symbol which seems to be a degree sign (°) as a substitute for the plimsoll mark. In the very same publication the plimsoll mark appears to be constructed by combining a horizontal stroke with a degree sign.<ref>E.R. Cohen, T. Cvitas, J.G. Frey, B. Holmström, K. Kuchitsu, R. Marquardt, I. Mills, F. Pavese, M. Quack, J. Stohner, H.L. Strauss, M. Takami, and A.J. Thor, "Quantities, Units and Symbols in Physical Chemistry", IUPAC Green Book, 3rd Edition, 2nd Printing, IUPAC & RSC Publishing, Cambridge (2008), p. 60</ref> A range of similar symbols are used in the literature: a stroked lowercase letter O (<sup><s>o</s></sup>),<ref>IUPAC (1993) ''Quantities, units and symbols in physical chemistry'' (also known as ''The Green Book'') (2nd ed.), p. 51</ref> a superscript zero (<sup>0</sup>)<ref>Narayanan, K. V. (2001) ''A Textbook of Chemical Engineering Thermodynamics'' (8th printing, 2006), p. 63</ref> or a circle with a horizontal bar either where the bar extends beyond the boundaries of the circle ({{Unichar|29B5|Circle with horizontal bar|ulink=}}) or is enclosed by the circle, dividing the circle in half ({{Unichar|2296|Circled minus}}).<ref>{{cite web|url=https://www.unicode.org/charts/PDF/U2980.pdf| publisher=Unicode| title=Miscellaneous Mathematical Symbols-B|date=2013|access-date=2013-12-19}}</ref><ref name=Mills>Mills, I. M. (1989) "The choice of names and symbols for quantities in chemistry". ''Journal of Chemical Education'' (vol. 66, number 11, November 1989 p. 887–889) [Note that Mills refers to the symbol ⊖ (Unicode 2296 "Circled minus" as displayed in https://www.unicode.org/charts/PDF/U2980.pdf) as a plimsoll symbol although it lacks an extending bar in the printed article.]</ref> Compared to the plimsoll symbol used in 1800s text, the U+29B5 glyph is too large and its horizontal line does not sufficiently extend beyond the boundaries of the circle. It is easily confused with the Greek letter [[theta]] (uppercase Θ or {{not a typo|ϴ}}, lowercase θ). As of 2024, the character {{Unichar|1CEF0|Medium small white circle with horizontal bar}} has been proposed for Unicode.<ref>{{cite web |title=Proposed New Characters: The Pipeline |url=https://www.unicode.org/alloc/Pipeline.html |website=www.unicode.org |access-date=15 June 2024}}</ref> It is a regular-sized Unicode symbol meant to be used in superscripted form when denoting standard state, replacing U+29B5 for this purpose.<ref>{{cite web |last1=Soiffer |first1=Neil |last2=Sargent |first2=Murray |last3=Freytag |first3=Asmus |title=Proposal for Ten Chemical Symbols |url=https://www.unicode.org/L2/L2023/23193r2-ten-chemical-symbols.pdf |access-date=25 December 2023 |date=20 October 2023}}</ref><ref>{{cite web |title=Recommendations to UTC #177 November 2023 on Script Proposals |url=https://www.unicode.org/L2/L2023/23238r-script-adhoc-rept.pdf |access-date=25 December 2023 |date=1 November 2023}}</ref>

Ian M. Mills, who was involved in producing a revision of ''[[Quantities, Units and Symbols in Physical Chemistry]]'', suggested that a superscript zero (<math>^0</math>) is an equal alternative to indicate "standard state", though a degree symbol (°) is used in the same article.<ref name=Mills/> The degree symbol has come into widespread use in general, inorganic, and physical chemistry textbooks in recent years.<ref>{{cite book|last1=Flowers |first1=Paul |last2=Theopold |first2=Klaus |last3=Langley |first3=Richard |last4=Robinson |first4=William R. |last5=Frantz |first5=Don |last6=Hooker |first6=Paul |last7=Kaminski |first7=George |last8=Look |first8=Jennifer |last9=Martinez |first9=Carol |last10=Eklund |first10=Andrew |last11=Blaser |first11=Mark |last12=Sorensen |first12=Tom |last13=Soult |first13=Allison |last14=Milliken |first14=Troy |last15=Moravec |first15=Vicki |last16=Powell |first16=Jason |last17=El-Giar |first17=Emad |last18=Bott |first18=Simon |last19=Carpenetti |first19=Don |title=Chemistry 2e |chapter-url= https://openstax.org/books/chemistry-2e/pages/5-3-enthalpy#term235|chapter=5.3 Enthalpy |date=14 February 2019 |publisher=Open Stax |access-date=9 April 2022|quote=We will include a superscripted "o" in the enthalpy change symbol to designate standard state.}}</ref><ref>{{cite book |last1=Miessler |first1=Gary L. |last2=Fischer |first2=Paul J. |last3=Tarr |first3=Donald A. |title=Inorganic Chemistry |date=2014 |publisher=Pearson Education |location=New Jersey |edition=5th|page=438}}</ref><ref>{{cite book |last1=Chang |first1=Raymond | last2=Thoman | first2=John W. Jr. |title=Physical Chemistry for the Chemical Sciences |date=2014 |publisher=University Science Books |location=New York|page=101|quote=The symbol for a standard state is a 'circle' superscript}}</ref> When read out loud, the symbol is pronounced "naught".