Talk:Potassium hydroxide

Melting Point

A wider search of the net shows some variety of figures for the melting point of KOH. ONe manufacturer quotes 360C, and another source quotes 380C. The Wikipedia article quotes 406C.

Anyone any ideas which is correct, or where there is an authoritative source. — Preceding unsigned comment added by 213.2.19.220 (talk) 14:27, 2005 January 9 (UTC)

Na+ and K+ are very similar chemically speaking, so perhaps the tendancy not to clump is in contrast to divalent ions like Ca++. --[1]

— Preceding unsigned comment added by 128.173.184.212 (talk) 20:34, 2006 February 21 (UTC)

You may want to try the Handbook of Chemistry and Physics.

— Preceding unsigned comment added by 141.151.173.45 (talk) 11:20, 2005 October 12 (UTC)

The physical constants have been updated with their "CRC Handbook of Chemistry and Physics 2006" values

— Preceding unsigned comment added by Bkessler (talk • contribs) 17:47, 2006 March 24 (UTC)

the melting point is indead 380 degrees. this is taken for the as chenistry revision guide and for exan pruposes this has to be correct

— Preceding unsigned comment added by 86.150.208.65 (talk) 09:50, 2007 April 6 (UTC)

You have wonderful faith in the people who set exams (of whom I am one)! One problem with the measurement of the melting point of KOH is that it is pretty much never anhydrous: there is always some water associated with it, even as a melt. The more water, the lower the melting point (as for almost all mixtures). The melting point may also vary with the rate of heating and other experimental parameters. The only reason that a melting point is quoted at all is to show that KOH melts before it dehydrates to K₂O. Physchim62 (talk) 10:14, 6 April 2007 (UTC)

The melting point of anhydrous KOH is above 400 C. The value of 360 C comes from a study in 1910 by Hevesy which was taken using KOH contaminated with water (which lowers the melting point substantially).

A summary of published experimentally measured melting points for "pure" KOH:

360.0 Hevesy 1910 [1]

379.9 Dai et al. 2023. [2]

380.0 Scarpa 1915. [3]

401.0 Cohen-Adad & Michaud 1956. [4]

402.0 Reshetnikov & Perfil’Eva 1968. [5]

403.6 Michaud 1961. [6]

404.1 Reshetnikov & Vilitus 1959. [7]

404.0 Rollet, Cohen-Adad, & Choucroun 1959. [8]

404.0 Rollet & Cohen-Adad 1964. [9]

404.0 Reshetnikov & Unzhakov 1953. [10]

404.0 Unzhakov 1952. [11]

404.2 Reshetnikov & Unzhakov 1953. [10]

405.1 Morachevskii & Berdichevskii. 1968. [12]

405.0 Michaud 1968. [13]

405.4 Michaud 1967. [14]

409.5 Otto & Seward. 1964. [15]

410.0 Seward & Martin 1949. [16]

I believe that the Seward numbers are the most likely to have correctly identified the melting point of anhydrous KOH based on a reading of all these papers. The lowering of the melting point below 410 is caused by the presence of water in the powder. I have updated the article with reference to Otto & Seward. 1964. [15] accordingly.

Hevesy, Dai, and Scarpa [1-3] are not correct results and deviate strongly from other results which prioritized dehydrating their KOH.

REFERENCES

[1] Hevesy, G. von Über Alkalihydroxyde. L: Die Zweistoffsysteme Natriumhydroxyd—Kaliumhydroxyd, Kaliumhydroxyd—Rubidiumhydroxyd und Rubidiumhydroxyd—Natriumhydroxyd. Zeitschrift für Physikalische Chemie 1910, 73U, 667, doi: https://doi.org/10.1515/zpch-1910-7336.

[2] Dai, S.; Liu, L.; He, H.; Yang, B.; Wu, D.; Zhao, Y.; Niu, D. Highly-efficient molten NaOH-KOH for organochlorine destruction: Performance and mechanism. Environ. Res. 2023, 217, 114815, doi: https://doi.org/10.1016/j.envres.2022.114815.

[3] Scarpa, G. Analisi termica delle miscele degli idrati alcalini coi corrispondenti alogenuri. I. Composti di potassio. Atti Accad. Lincei 1915, 24, 738.

[4] Cohen-Adad, R.; Michaud, M. Les équilibres liquide-solide du système binaire eau-potasse. C. R. Acad. Sci. Paris 1956, 242, 2569.

[5] Reshetnikov, N.A.; Perfil’eva, O.G. Phase transformations in the Ki, Li || CO3, OH ternary recipricol system. Russ. J. Inorg. Chem. 1968, 13.

[6] Michaud, M. Étude du système binaire eau-potasse dans la région des faibles teneurs en eau. C.R. Acad. Sc. C 1961, 253, 1947.

[7] Reshetnikov, N.A.; Vilutis, N.I. Ternary system of the hydroxides of lithium, sodium, and potassium. Russ. J. Inorg. Chem. 1959, 4, 123.

[8] Rollet, A.-P.; Cohen-Adad, R.; Choucroun, J. Préparation d’hydroxydes alcalins anhydres exempts de carbonates. J., Bull. Soc. Chim. France 1959, 1, 146.

[9] Rollet, A.-P.; Cohen-Adad, R. Les systèmes « eau-hydroxyde alkalin ». Review de Chimie minérale 1964, 1, 451.

[10] Reshetnikov, N.A.; Unzhakov, G.M. Thermographic investigation of binary systems of potassium and sodium hydroxides and potassium and lithium hydroxides. Iz.. Fiz.-Khim. Nauch.-Issled. Inst. Irkutsk. Gosudarst Univ 1953, 2, 5.

[11] Unzhakov, G.M. Reciprocal system of potassium and lithium hydroxides and chloride. Dokl. Akad. Nauk SSSR 1952, 87, 791.

[12] Morachevskii, A.G.; Berdichevskii, N.I. Equilibria involving alkali metals and their compounds. 4. Fusibility diagrams of a potassium, sodium hydroxide, chloride, ternary reciprocal system. Zh. Prikl. Khim. 1968, 41, 732.

[13] Michaud, M. Contribution á l’étude des hydroxydes de potassium et de baryum. Rev. Chim. Miner 1968, 5, 89.

[14] Michaud, M. Étude du systeme binaire potasse-lithine. C.R. Hebd. Seances Acad. Sci. C 1967, 264, 1939.

[15] Otto, H.W.; Seward, R.P. Phase equilibria in the potassium hydroxide-sodium hydroxide system. J. Chem. Eng. Data 1964, 9, 507, doi: https://doi.org/10.1021/je60023a009.

[16] Seward, R.P.; Martin, K.E. The melting point of potassium hydroxide. J. Am. Chem. Soc. 1949, 71, 3564, doi: https://doi.org/10.1021/ja01178a530.

147.210.61.171 (talk) 11:02, 21 September 2023 (UTC)

Uses

I'd like to see it mentioned that it is commonly used as a catalyst in the production of biodiesel from vegetable oil. —Preceding unsigned comment added by 213.100.137.147 (talk) 15:16, 17 October 2008 (UTC)

"Because of their softness and greater solubility, potassium soaps require less water to liquefy, and can thus contain more cleaning agent than liquefied sodium soaps." The use of liquefy and liquefied are surely incorrect. To liquefy something you need to melt it. "dissolve/dissolved" would surely be correct. — Preceding unsigned comment added by 81.109.92.2 (talk) 10:39, 28 January 2020 (UTC)

Solubility

The article's Properties/Solubility and dessicating properties section states "Approximately 121 g of KOH will dissolve in 100 mL of water at room temperature...," but Infobox/Properties/Solubility in water cites "110 g/100 mL (25 °C)". Does the article's statement need some elaboration or does the Infox data need to be updated? (I'm qualified on this subject only as a copy editor.) Gnostic804 (talk) 00:52, 24 October 2010 (UTC)

I think there is a typo. Pickering's 1893 article give the solubility as 112 g/100 mL. 147.210.61.171 (talk) 10:45, 3 October 2023 (UTC)

Additionally, 112/56=2 while 100/40=2.5 so how exactly is "...on a molar basis, KOH is slightly more soluble than NaOH" meant to make sense? Am I missing something? 35.20.122.61 (talk) 17:34, 25 June 2024 (UTC)

Solubility

The little chart doesn't mention solubility in water, yet the text does.Longinus876 (talk) 22:59, 20 December 2020 (UTC)

Lye as an alternative name for KOH?

I was always under the impression that lye was the common name for sodium hydroxide. I've never heard of KOH being referred to as lye.

Is it possible that this is an error? Or are NaOH and KOH BOTH referred to as lye? It seems unusual that two different chemicals would share the same name.

I'm not terribly familiar with the history and naming of NaOH and KOH. But, perhaps somebody more familiar can clear up this confusion.

Thanks in advance.

VoidHalo (talk) 17:09, 20 March 2024 (UTC)

I think it's called potash lye Pygos (talk) 12:42, 25 July 2024 (UTC)