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The word "litmus" comes from an Old Norse word for "pulp".[1] About 1300 the Spanish physician Arnaldus de Villa Nova began using litmus to study acids and bases.[2][3] From the 16th century onwards, the blue dye was extracted from some lichens, especially in the Netherlands.
The main use of litmus is to test whether a solution is acidic or basic, as blue litmus paper turns red under acidic conditions, and red litmus paper turns blue under basic or alkaline conditions, with the color change occurring over the pH range 4.5–8.3 at 25 °C (77 °F). Neutral litmus paper is purple.[2] Wet litmus paper can also be used to test for water-soluble gases that affect acidity or basicity; the gas dissolves in the water and the resulting solution colors the litmus paper. For instance, ammonia gas, which is alkaline, turns red litmus paper blue. While all litmus paper acts as pH paper, the opposite is not true.
Litmus can also be prepared as an aqueous solution that functions similarly. Under acidic conditions, the solution is red, and under alkaline conditions, the solution is blue.
Chemical reactions other than acid–base can also cause a color change to litmus paper. For instance, chlorine gas turns blue litmus paper white; the litmus dye is bleached[4] because hypochlorite ions are present. This reaction is irreversible, so the litmus is not acting as an indicator in this situation.
Chemistry
The litmus mixture has the CAS number 1393-92-6 and contains 10 to around 15 different dyes. All of the chemical components of litmus are likely to be the same as those of the related mixture known as orcein, but in different proportions. In contrast with orcein, the principal constituent of litmus has an average molecular mass of 3300.[5] Acid-base indicators on litmus owe their properties to a 7-hydroxyphenoxazonechromophore.[6] Some fractions of litmus were given specific names including erythrolitmin (or erythrolein), azolitmin, spaniolitmin, leucoorcein, and leucazolitmin. Azolitmin shows nearly the same effect as litmus.[7]
A recipe to make litmus out of the lichens, as outlined on a UC Santa Barbara website says:[8]
Details are difficult to find because the processes were kept secret. This summary of a modern manufacturing procedure is from The vanishing lichens, D H S Richardson, London, 1975. The lichens (preferably Lecanora tartarea and Roccella tinctoria) are ground in a solution of sodium carbonate and ammonia. Stir the lichens from time to time and the color changes from red to purple and finally blue after about four weeks. The lichens are then dried and powdered. At this stage the lichens contain partly litmus and partly orceinpigments. The orcein is removed by extraction with alcohol, leaving the pure blue litmus. It is marketed as blue lumps, masses, or tablets, after mixing with colorless compounds such as chalk and gypsum. Litmus paper is paper impregnated with this substance.
Mechanism
Red litmus contains a weak diprotic acid. When it is exposed to a basic compound, the hydrogen ions react with the added base. The conjugate base formed from the litmus acid has a blue color, so the wet red litmus paper turns blue in alkaline solution.
^ Surber, Christian; Humbert, Philippe; Abels, Christoph; Maibach, Howard (2018). "The Acid Mantle: A Myth or an Essential Part of Skin Health?". In Surber, Christian; Abels, Christoph; Maibach, Howard (eds.). pH of the Skin: Issues and Challenges. Current Problems in Dermatology, ISSN 1421-5721, Volume 54. Basel: Karger Medical and Scientific Publishers. p. 3. ISBN9783318063851. Retrieved 30 August 2022. In the early 14th century, the Spanish scholar, Arnaldus de Villa Nova (1235–1311), began to use litmus for studying acids and bases. This compound, extracted from a lichen, had been used as a dye since at least the time of the Vikings, but he was the first person known to use it as a test of acidity.
^O'Leary, Donal (2000). . The Chemical Elements. Archived from the original on 2008-12-21.
^Beecken, H.; E-M. Gottschalk; U. v Gizycki; H. Krämer; D. Maassen; H-G. Matthies; H. Musso; C. Rathjen; Ul. Zdhorszky (2003). "Orcein and Litmus". Biotechnic & Histochemistry. 78 (6): 289–302. doi:10.1080/10520290410001671362. PMID 15473576. S2CID 41944320.
^H. Musso, C. Rathjen (1959). "Orcein dyes. X. Light absorption and chromophore of litmus". Chem. Ber. 92 (3): 751–3. doi:10.1002/cber.19590920331.
^E.T. Wolf: Vollständige Übersicht der Elementar-analytischen Untersuchungen organischer Substanzen, S.450-453, veröffentlicht 1846, Verlag E. Anton (Germany)
litmus, other, uses, disambiguation, this, article, includes, list, general, references, lacks, sufficient, corresponding, inline, citations, please, help, improve, this, article, introducing, more, precise, citations, january, 2022, learn, when, remove, this,. For other uses see Litmus disambiguation This article includes a list of general references but it lacks sufficient corresponding inline citations Please help to improve this article by introducing more precise citations January 2022 Learn how and when to remove this template message This article may be expanded with text translated from the corresponding article in German February 2021 Click show for important translation instructions Machine translation like DeepL or Google Translate is a useful starting point for translations but translators must revise errors as necessary and confirm that the translation is accurate rather than simply copy pasting machine translated text into the English Wikipedia Consider adding a topic to this template there are already 9 686 articles in the main category and specifying topic will aid in categorization Do not translate text that appears unreliable or low quality If possible verify the text with references provided in the foreign language article You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation A model attribution edit summary is Content in this edit is translated from the existing German Wikipedia article at de Lackmus see its history for attribution You should also add the template Translated de Lackmus to the talk page For more guidance see Wikipedia Translation Look up litmus in Wiktionary the free dictionary Litmus is a water soluble mixture of different dyes extracted from lichens It is often absorbed onto filter paper to produce one of the oldest forms of pH indicator used to test materials for acidity In an acidic medium blue litmus paper turns red while in a basic or alkaline medium red litmus paper turns blue Litmus powder Chemical structure of 7 hydroxyphenoxazone the chromophore of litmus components Contents 1 History 2 Natural sources 3 Uses 4 Chemistry 5 Mechanism 6 ReferencesHistory EditThe word litmus comes from an Old Norse word for pulp 1 About 1300 the Spanish physician Arnaldus de Villa Nova began using litmus to study acids and bases 2 3 From the 16th century onwards the blue dye was extracted from some lichens especially in the Netherlands Natural sources Edit Parmelia sulcata Litmus can be found in different species of lichens The dyes are extracted from such species as Roccella tinctoria South American Roccella fuciformis Angola and Madagascar Roccella pygmaea Algeria Roccella phycopsis Lecanora tartarea Norway Sweden Variolaria dealbata Ochrolechia parella Parmotrema tinctorum and Parmelia Currently the main sources are Roccella montagnei Mozambique and Dendrographa leucophoea California 2 Uses Edit Litmus paper after being used The main use of litmus is to test whether a solution is acidic or basic as blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions with the color change occurring over the pH range 4 5 8 3 at 25 C 77 F Neutral litmus paper is purple 2 Wet litmus paper can also be used to test for water soluble gases that affect acidity or basicity the gas dissolves in the water and the resulting solution colors the litmus paper For instance ammonia gas which is alkaline turns red litmus paper blue While all litmus paper acts as pH paper the opposite is not true Litmus can also be prepared as an aqueous solution that functions similarly Under acidic conditions the solution is red and under alkaline conditions the solution is blue Litmus pH indicator below pH 4 5 above pH 8 34 5 8 3Chemical reactions other than acid base can also cause a color change to litmus paper For instance chlorine gas turns blue litmus paper white the litmus dye is bleached 4 because hypochlorite ions are present This reaction is irreversible so the litmus is not acting as an indicator in this situation Chemistry EditThe litmus mixture has the CAS number 1393 92 6 and contains 10 to around 15 different dyes All of the chemical components of litmus are likely to be the same as those of the related mixture known as orcein but in different proportions In contrast with orcein the principal constituent of litmus has an average molecular mass of 3300 5 Acid base indicators on litmus owe their properties to a 7 hydroxyphenoxazone chromophore 6 Some fractions of litmus were given specific names including erythrolitmin or erythrolein azolitmin spaniolitmin leucoorcein and leucazolitmin Azolitmin shows nearly the same effect as litmus 7 A recipe to make litmus out of the lichens as outlined on a UC Santa Barbara website says 8 Details are difficult to find because the processes were kept secret This summary of a modern manufacturing procedure is from The vanishing lichens D H S Richardson London 1975 The lichens preferably Lecanora tartarea and Roccella tinctoria are ground in a solution of sodium carbonate and ammonia Stir the lichens from time to time and the color changes from red to purple and finally blue after about four weeks The lichens are then dried and powdered At this stage the lichens contain partly litmus and partly orcein pigments The orcein is removed by extraction with alcohol leaving the pure blue litmus It is marketed as blue lumps masses or tablets after mixing with colorless compounds such as chalk and gypsum Litmus paper is paper impregnated with this substance Mechanism EditRed litmus contains a weak diprotic acid When it is exposed to a basic compound the hydrogen ions react with the added base The conjugate base formed from the litmus acid has a blue color so the wet red litmus paper turns blue in alkaline solution References Edit Litmus 7 October 2021 a b c Neupert Manfred January 31 2013 Lackmus Rompp Lexikon Chemie in German Surber Christian Humbert Philippe Abels Christoph Maibach Howard 2018 The Acid Mantle A Myth or an Essential Part of Skin Health In Surber Christian Abels Christoph Maibach Howard eds pH of the Skin Issues and Challenges Current Problems in Dermatology ISSN 1421 5721 Volume 54 Basel Karger Medical and Scientific Publishers p 3 ISBN 9783318063851 Retrieved 30 August 2022 In the early 14th century the Spanish scholar Arnaldus de Villa Nova 1235 1311 began to use litmus for studying acids and bases This compound extracted from a lichen had been used as a dye since at least the time of the Vikings but he was the first person known to use it as a test of acidity O Leary Donal 2000 Chlorine The Chemical Elements Archived from the original on 2008 12 21 Beecken H E M Gottschalk U v Gizycki H Kramer D Maassen H G Matthies H Musso C Rathjen Ul Zdhorszky 2003 Orcein and Litmus Biotechnic amp Histochemistry 78 6 289 302 doi 10 1080 10520290410001671362 PMID 15473576 S2CID 41944320 H Musso C Rathjen 1959 Orcein dyes X Light absorption and chromophore of litmus Chem Ber 92 3 751 3 doi 10 1002 cber 19590920331 E T Wolf Vollstandige Ubersicht der Elementar analytischen Untersuchungen organischer Substanzen S 450 453 veroffentlicht 1846 Verlag E Anton Germany Students ask questions UCSB scientists answer them UCSB ScienceLine 2002 Retrieved from https en wikipedia org w index php title Litmus amp oldid 1133713432, wikipedia, wiki, book, books, library,
