Talk:Phenolphthalein

Comments

This page is badly formatted in MSIE, and I have no idea how to correct the "colorless" bit in the box for MSIE and Opera. It works in Firefox, but the long vertical image causes problems there.. 218.102.71.159 10:47, 28 November 2005 (UTC)

There isn't any info about what pH the indicator returns back to clear in highly basic conditions (ie when the concentration of "Phenolphthalein(OH)3-" is highest). Any reason for this? — Preceding unsigned comment added by Leakeyjee (talk • contribs) 09:43, 9 April 2006 (UTC)

---

Not sure about the coding problems - it seems to show up fine in Opera 9b2 for me.

As for the pH of changing back to colorless - I did some experiments the other day and found that the maximum absorption (i.e. when the solution is the most pink) occurs around pH 12 or so. I didn't need any more accuracy than that, but at least it'll give you a starting point.

Hope this helps.

Zxian 18:29, 24 May 2006 (UTC)

---

The chart in the body of the article appears to say that phenolphthalein is only pink between pH 8.2 and pH 10.0. Isn't this misleading if the maximum absorption is above pH 10?

The chart directly contradicts the box in the upper right hand corner which says that phenolphthalein is pink above pH 10.0.

9 Feb 2007

Error!

Why is the melting point listed as higher than the boiling point? —The preceding unsigned comment was added by 74.64.65.118 (talk) 16:40, 18 February 2007 (UTC).

Structure for In

Does anyone know exactly what this is (i.e. the form present below pH 0) - as it leaves rather a hole in the article. 86.148.60.205 19:54, 2 March 2007 (UTC)

See below in Talk:Phenolphthalein#Forms. It is still a complicated matter. --Taweetham (talk) 05:15, 19 June 2020 (UTC)

Laxative Use

A quick note (this is not really article material): James Outlaw, PhD (a chemistry professor I know) tells me that there are two reasons for keeping the indicator (phenolphthalein) present all of their labs' pure ethanol. First, it is handy to have so you aren't required to add it later for any acid/base titration. However, the second reason is related to its medical uses. By adding the indicator to otherwise pure drinking alcohol, the ethanol is rendered undesirable to drink, as the phenolphthalein would cause severe diarrhea. Josh3580 14:31, 5 March 2007 (UTC)

Uses - Construction

I know phenolphthalein is used in construction materials testing (for roadways especially), to test for the presence of stabilizing agents in soils, such as lime, cement, or fly-ash, because it picks up the presence of Calcium ions or CaO, or something similar. However, i'm not familiar with the chemistry of it, can someone more knowledgeable add it to the 'uses' section in the article?Foij00 21:06, 11 May 2007 (UTC)

Response to Error!

Error! Why is the melting point listed as higher than the boiling point? —The preceding unsigned comment was added by 74.64.65.118 (talk) 16:40, 18 February 2007 (UTC).

Chemfinder has the same information listed, I'm guessing it just got copied from there.

The CRC lists the mp as 262.5 C and does not list a boiling point. I will try to fix this.

2003. CRC Handbook of Chemistry and Physics 84th Ed. Chemical Rubber Publishing Company, Boca Raton, FL

P.S. This page is a disaster.

— Preceding unsigned comment added by 71.206.215.35 (talk) 01:18, 17 October 2007 (UTC)

Pronunciation

What is the pronuncation for phenolphthalein? --139.103.73.75 23:23, 8 November 2007 (UTC)

• So far as I know, it's fee-NO-thay-leen. It is current Wikipedia policy to render pronunciation guides in unpronouncable IPA glyphs unfortunately. Msaunier (talk) 07:43, 4 August 2011 (UTC)

  IPA is very useful, compared to the pointlessly spelling it out like you have. Fauxnetics can be interpreted in all sorts of ways depending on your accent and it's useless for non-native English speakers as well. GamerAJ1025 (talk) 15:24, 19 January 2024 (UTC)

Well, you missed half of the word. Its fee-NOL-ft-uh-lay-een. --193.154.115.241 (talk) 03:57, 3 December 2017 (UTC)

pH

What is the pH of phenolphthalein? 72.67.175.145 (talk) 07:14, 13 December 2007 (UTC)

Contradictory

This article has contradictions. The orange in acid is contradictory to the text, or if not needs further explanation. —Preceding unsigned comment added by 80.176.155.189 (talk) 22:31, 2 January 2008 (UTC)

See below in Talk:Phenolphthalein#Forms. It is still a complicated matter. --Taweetham (talk) 05:17, 19 June 2020 (UTC)

Orange color in concentrated strong acid

I tried the following reactions: Phenolphthalein + concentrated sulfuric acid -> orange Phenolphthalein + concentrated hydrochloric acid -> pale yellow According to my chemistry teacher, the orange is due to phenolphthalein reacting with the sulfate (instead of the protons) and the pale yellow is the natural color of phenolphthalein. Andrey (talk) 01:58, 24 January 2008 (UTC)

Doubt it. It's just that conc. HCl is not as strong an acid as conc. H₂SO₄, and so cannot deprotonate phenolphthalein to its red form.

What does your teacher suggest the sulfate is doing to cause the orange colour?

Ben (talk) 20:07, 24 January 2008 (UTC)

Maybe it's possible to redox iodine crystals in the presence of hydrogen to get concentrated hydroiodic acid. Then just mix HI powder, phenolphthalein, and a bit of water and see what happens, since K_a HI > K_a HCl. Andreyvul (talk) 18:53, 26 January 2008 (UTC)

A new reference doi:10.1021/ed060p239 was added today. It may help explain this issue. --Taweetham (talk) 01:42, 20 April 2020 (UTC)

Error concerning colour in acidic and alkaline solutions

I believe that the colour phenolphthalein turns in an acidic solution is COLOURLESS not orange and in a neutral solution a pink tinge and in alkaline pink. Is this correct? Several other websites back this up as does my chemistry teacher and a practical OCR chemistry paper. Please could someone infrom me if this is correct as i did not want to change the infomation on the page straight away. Many Thanks. —Preceding unsigned comment added by AdamJKB (talk • contribs) 11:48, 9 May 2008 (UTC)

Phenolphthalein does indeed turn orange in very strong acid solutions (hydronium > 10M). Have a chemistry teacher put some full strength sulfuric acid in a small beaker (do this in a fume hood), and add a few drops of the indicator. It will turn orange. — ★Parsa ☞ talk 21:53, 1 May 2013 (UTC)

ph

the ph of pkenolphthalein is between 8.2 to 10.0 —Preceding unsigned comment added by 59.93.240.6 (talk) 14:31, 14 August 2009 (UTC)

I'm assumming you mean phenolphthalein. Phenolphthalein is an indicator for pH. The color will transition from clear to fuchsia (magenta) over a range of about 8.0–9.6. In solutions with pH above about 10, the indicator will turn the solution magenta. In solutions below about 8 (which includes all acids and neutral solutions), the solution will remain clear. In full strength strong acids the color will change to orange. — ★Parsa ☞ talk 22:00, 1 May 2013 (UTC)

Synthesis

Can someone who knows plaese add a synthesis section? We usually have them, especially for rather important compounds such as this. Msaunier (talk) 07:45, 4 August 2011 (UTC)

There is now a synthesis section written by somebody. I believe concentrated sulphuric acid also can be used as catalyst. What about the yield? Will there be any product with one or both phenol bound in the ortho position? If not is it due to steric hindrance or is there another explanation?150.227.15.253 (talk) 16:03, 3 August 2017 (UTC)

Allergy

A section should be added that details phenolphthalein allergies and its manifestations.

72.82.166.184 (talk) 03:21, 2 February 2014 (UTC)

Contradiction

In the intro it says 'Phenolphthalein is insoluble in water and usually is dissolved in alcohols for use in experiments'. Then in the chembox we have the property 'Solubility in water : Soluble'. Which is correct? Plarstic (talk) 14:05, 10 February 2015 (UTC)

External links modified

Hello fellow Wikipedians,

I have just added archive links to one external link on Phenolphthalein. Please take a moment to review my edit. If necessary, add {{cbignore}} after the link to keep me from modifying it. Alternatively, you can add {{nobots|deny=InternetArchiveBot}} to keep me off the page altogether. I made the following changes:

• Added archive https://web.archive.org/20060925035727/http://www.iscid.org/encyclopedia/Universal_Indicator to http://www.iscid.org/encyclopedia/Universal_Indicator

When you have finished reviewing my changes, please set the checked parameter below to true to let others know.

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 18 January 2022).

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—^{cyberbot II}_{Talk to my owner:Online} 10:14, 5 January 2016 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Phenolphthalein/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

How can one have a pH of less than zero? A pH of zero (also physically impossible) would mean that the concentration of H+ ions is 100%. A pH of less than zero would mean the concentration of H+ ions is more than 100%.MarkDoc704 17:33, 25 July 2007 (UTC)

Last edited at 17:33, 25 July 2007 (UTC). Substituted at 02:49, 30 April 2016 (UTC)

pH isn't percent-acidity. The simple definition is pH=-log([H+], so pH=0 means [H+] is 1 M, an easy solution to make. Commercial hhydrochloric acid is about 12&mbsp;M and commercial sulfuric acid is about 18 M. There is a leveling or activity-coefficient effect to consider (see our pH article for details) but it's still easy to go beyond the "intro-level textbook definition" of 0–14. DMacks (talk) 11:37, 25 April 2020 (UTC)

Hence the name

Its twice stated (in parentheses:"(hence the name)") that its name comes from the acidic conditions during the syntheses. I do not get that. What part in the name is hinting to acidic conditions? -ein?? why??? --193.154.115.241 (talk) 03:56, 3 December 2017 (UTC)

Feen-a-mint gum

Why does this article have a redirect from "Feen-A-Mint gum"? Shouldn't the product be mentioned somewhere in the article to justify a redirect? Eddie Blick (talk) 22:12, 14 December 2018 (UTC)

@Teblick: I added a detail mentioning it. DMacks (talk) 11:29, 25 April 2020 (UTC)

DMacks, Thanks! Eddie Blick (talk) 13:15, 25 April 2020 (UTC)

Forms

@DMacks: To get six forms, you will need Ph5 and Ph6 in doi:10.1021/ed060p239 which have sulfate group in the structure. I am wondering if this is appropriate in the context of a pH indicator. --Taweetham (talk) 10:39, 25 April 2020 (UTC)

Good point! If it's a color-change that is in response to pH and sulfate, it's not strictly as a pH indicator. I adjusted the sentence. However, There is still an unstated mono-anionic form. I'd wondered why we don't have HIn^– listed, which seems like an obvious intermediate in the H₂In → In^2– process. It is one of the structures in the animation later in the article. Apparently it is also colorless just like H₂In. And there is another colorless form that can exist in the same low-pH as the H₂In structure: hydrolysis of the lactone. And there is another colorless isomer of HIn^– in equilibrium with the given one. None of these represent useful additions to the color-change intervals of this table. See doi:10.1007/s10847-008-9419-3 and doi:10.1007/PL00013491 for structures. DMacks (talk) 11:14, 25 April 2020 (UTC)

Totally agree for the HIn^– point. I feel that the information as written is dodgy in several ways but so far I only find two papers to help patch some parts. Personally, I do not like the animation there but let start by fixing the reaction scheme and see if the animation is still valid. Let me summarize the state of the article and the two references you gave in the table below so that we are on the same page.--Taweetham (talk) 02:13, 26 April 2020 (UTC)

Structure in the article (and our discussion)	doi:10.1021/ed060p239 (1983) p240	doi:10.1007/s10847-008-9419-3 (2008) p218 scheme 1	doi:10.1007/PL00013491 (1998) p818 scheme 1
H3In+	Ph3
H2In	Ph1	LHS of (i)	1
H2In (H2O)			1' (5 O atoms)
HIn−		RHS of (i)	1'- (5 O atoms)
In2− (immediately after losing H+ but before rearrangement)		LHS of (ii)
In2−	Ph2	RHS of (ii)	1'2- (5 O atoms)
In(OH)3−	Ph4	(iii)

@DMacks: Your help would be greatly appreciate to resolve issues in this High-importance WikiProject Chemicals article.

1. Please see if the the table above correctly summarize the two additional references that you suggested in the context of the article.
2. In the first paragraph of the article, HIn is used rather than H₂In. Should we use H₂In? or add some notes that it is actually H₂In?
3. The number of oxygen atoms are not consistent across the three references we have. The abbreviation we have on the left is also not consistent within its own set. In(OH)³⁻ appears to be the pain point. Is it better to called it just In³⁻?
4. There is also a {{cn}} issue with regards to "slow fading" at high pH. If this is true, my suspicion is that it may be permanent decomposition/rearrangement rather than reversible acid-base equilibrium. References are not that easy to find.

--Taweetham (talk) 02:34, 26 April 2020 (UTC)

@DMacks: I revised to the article as my student and I found new references with pKas values of the dye and its sulfonated derivative. I leave the details for my students to fill later but made the structural changes myself.--Taweetham (talk) 07:11, 23 February 2022 (UTC)

Add IPA

This page should have an IPA transcription, because this word hard has a pronunciation that is very different from how it's spelled. I transcribed it here so no one else has to do it: /ˌfinəlˈθælin/. Sultan the Sultan (talk) 06:31, 21 April 2022 (UTC)

I agree. However it depends on accent. The British pronunciation is /ˌfinɒlˈθεɪlin/ or alternatively /ˌfinɒlˈfθεɪlin/. Some people say the /fi/ as /fε/, and some people say the /εɪ/ as /æ/ or /ɑ/. GamerAJ1025 (talk) 15:29, 19 January 2024 (UTC)

Americans will likely say /ˌfinɑlˈθεɪlin/ or /ˌfinɑlˈθeɪlin/ GamerAJ1025 (talk) 15:31, 19 January 2024 (UTC)