Talk:Bromothymol blue

Untitled

Place bromothymol blue in a jar with a plant. Bromothymol blue is then "exposed" to carbon dioxide (exhale into jar). Bromothymol Blue is now yellow color. During photosynthesis, the plant takes in carbon dioxide and gives out oxygen. will bromothhymol blue turn blue again

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I'm not so sure that stomach contents will be blue; the pH of the stomach should make them yellow, surely? Brythain 01:53, 11 May 2007 (UTC)

Ingestion

"Ingesting BTB will color urine brightly blue for a day and will also color stomach content similarly. "

I've removed the above sentence from the article for two reasns. First, the claim is unsourced. Second, putting something like this into an article without warnings regarding health effects (toxic/carconigen) is a terrible idea. What if someone decides to test this? Besides, the information isn't necessary or even relevant to the rest of the article.--Bfesser 02:49, 18 June 2007 (UTC)

Redirects

Searching "Bromothymol" or "Bromthymol" should redirect here. 71.121.232.132 (talk) 03:16, 23 June 2008 (UTC)

Now done as requested. Walkerma (talk) 05:53, 26 January 2009 (UTC)

The Same?

I understand that BTB measures your pH level. My point will be this -- why have so many different of these papers that virtually do the same thing? If you think about all the different variations of BTB (there are so many i cant list them all) you come to think," why are we as scientists wasting our time on this?" Thank you for your interest, i hope you see the light as well.

Goodbye fellow scientist and i hope you will invest your time in something greater than acidity levels.

74.78.145.176 (talk) 18:29, 1 October 2009 (UTC)Dr. Samgoria

Needs Restructuring

Almost the entire article is in the introduction. Also the table on the right is too wide. BenPlotke (talk) 14:09, 18 May 2012 (UTC)

Accepted pKa of bromothymol blue

It seems as though I have entered into an intentioned editing battle over the pKa of bromothymol blue. I changed the pKa value from 7.10 to 7.0 since the CRC of Handbook of Chemistry and Physics - 86th ed. (2005-2006) lists the pKa as 7.0. An unregistered user keeps changing the value back to 7.10. In the most recent edit, the source for the pKa is given as the Sigma-Aldrich catalog. I object to this reference for several reasons.

• Supply catalogs are generally not recognized as repositories of accurate/precise physical and/or chemical data, whereas the CRC Handbook is a widely-used and highly-respected source of reference data.
• The Sigma-Aldrich catalog lists the pKa value of 7.10 as approximate. (The quoted description from the online catalog is: Bromothymol Blue (BTB) is a pH indicator (pKa approx. 7.1) that is used as a biological slide vital stain to define cell walls or nuclei under the microscope.) At the very least, using a value of 7.10 in this article clearly over-states the precision of the catalog value.
• The Sigma-Aldrich catalog does not provide transparent referencing to experimental data, which the CRC Handbook does provide.

Unless a better reference for the pKa of bromothymol blue is given, the CRC value should be used. Furthermore, any changes to the pKa value should be first be discussed on the talk page to achieve consensus among active editors. JCMPC (talk) 21:14, 23 November 2014 (UTC)

The pKa is listed as 7.1 in a source already cited in the cite, also published by the CRC press. See: Sabnis, R. W.; Handbook of Acid-Base Indicators, CRC Press: Boca Raton, 2007; p54.

Hope this doesn't rock any boats but I do see 7.1 cited more often then 7.0 as well. 104.48.252.245 (talk) 01:50, 21 January 2015 (UTC)

I have no problems using a different value as long as it is cited from a proper source. I didn't like that the Sigma-Aldrich catalog was being used before. The question now is what to do with conflicting information. How many significant figures does the reference report? It will be a while before my library has a copy available for me to check it. JCMPC (talk) 21:24, 9 March 2015 (UTC)

The 2008 version of Sabnis' "Handbook" lists the pKa as "7.0, 7.1". JCMPC (talk) 12:33, 6 April 2015 (UTC)

References

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So...Bromothymol blue is diprotic?

Please forgive me if this was obvious in the article, but I noticed that the equilibrium shown (which is not mass balanced) has bromothymol blue undergoing exchange of 2 equivalents of acid. In solution is the sultone the dominant acid form, or is the first pKa much more acidic and at low concentration of acid the dominant equilibrium form (that is observed as the yellow form) the quinoidal-phenol? — Preceding unsigned comment added by 75.128.12.178 (talk) 05:04, 30 January 2017 (UTC)

I noticed the same thing. I believe the structure diagram with 7.1 listed as the pKa is in error. The transition at this pH only involves a single proton, and the correct diagram would be this one I found on a (unfortunately not verifiable) source on the web: https://media.cheggcdn.com/study/9e0/9e086aa6-e6c7-4ed2-898e-ed360d72af63/image.png The second proton is not lost until very low pH. --Kent G. Budge (talk) 00:28, 31 March 2020 (UTC)

All Phthalein dyes may have the same issue. This was discussed at length in Talk:Phenolphthalein. --Taweetham (talk) 13:53, 27 March 2022 (UTC)

According to doi:10.1021/ed1007102, a single proton exchange is enough to change to the colour blue. I can change to structure to add one proton. Roger Burger (talk) 07:00, 7 February 2023 (UTC)

Synthesis?

How is this stuff made? Pthalic acid and 4-bromothymol? Riventree (talk) 13:31, 29 April 2019 (UTC)

I've added a synthesis route from a chemical supply company data sheet. It would be nice to have a more complete description with better verifiability, of course, but at least it's something. --Kent G. Budge (talk) 15:44, 4 April 2020 (UTC)

Is there really a pink/red phase?

I can't find any mention of it in the literature Riventree (talk) 13:32, 29 April 2019 (UTC)

@Riventree: See Talk:Phenolphthalein#Forms. Possibly, the pink/red color is not a result of acid-base reaction. --Taweetham (talk) 10:37, 27 March 2022 (UTC)

The user is banned indefinitely so we cannot ask him/her for reference(s0 on the edit. My suspicion is that the sulfate group may turn into something else under concentrated HCl. (This is the opposite of what may happen in the phenolpthalein case.) I will revert now. --Taweetham (talk) 10:40, 27 March 2022 (UTC)