In a highly basic solution, phenolphthalein's slow change from pink to colorless as it is converted to its In(OH)3− form is used in chemistry classes for the study of reaction kinetics.

Phenolphthalein is often used as an indicator in acid–base titrations.

When acid is added in the solution it gives red color. [3] Under strongly acidic conditions, it exists in protonated form (HIn+), providing an orange coloration.


The nonionized phenolphthalein molecule is colorless, the protonated phenolphthalein ion is an orange, and the deprotonated phenolphthalein ion is fuschia. [8][9] Laxative products formerly containing phenolphalein have often been reformulated to have alternate active ingredients: Feen-a-Mint[10] switched to bisacodyl and Ex-Lax[11] was switched to a senna extract. Phenolphthalein is used in toys, for example as a component of disappearing inks, or disappearing dye on the Hollywood Hair Barbie hair. Color loss of phenolphthalein in 1% wt/vol sodium carbonate and saturated lime water solution due to decomposition to 2-(4-hydroxybenzoyl)benzoic acid and phenol.

Empirical Formula (Hill Notation) C 20 H 14 O 4. The weak acid has no color while its ion gives bright pink color. Phenolphthalein is slightly soluble in water and usually is dissolved in alcohols for use in experiments. When a 1% phenolphthalein solution is applied to normal concrete, it turns bright pink. Phenolphthalein can be synthesized by condensation of phthalic anhydride with two equivalents of phenol under acidic conditions (hence the name). NACRES NA.47

In strongly basic solutions, phenolphthalein is converted to its In(OH)3− form, and its pink color undergoes a rather slow fading reaction[citation needed] and becomes completely colorless above 13.0 pH. Phenolphthalein is a potent laxative, which If you are on a personal connection, like at home, you can run an anti-virus scan on your device to make sure it is not infected with malware. A false positive can result from the presence of substances with catalytic activity similar to hemoglobin. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox.

This article was most recently revised and updated by, https://www.britannica.com/science/phenolphthalein, Community College of Rhode Island - Phenolphthalein, National Center for Biotechnology Information - PubChem - Phenolphthalein, phenolphthalein - Student Encyclopedia (Ages 11 and up). Let us know if you have suggestions to improve this article (requires login). EC Number 201-004-7.

Answer: a Explanation: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanationof the Assertion.

What color is phenolphthalein in a neutral solution?
What *that* means is that you can use any indicator that changes colour between a pH value of about 4 and 10 (for safety). It belongs to the class of dyes known as phthalein dyes. In the ink, it is mixed with sodium hydroxide, which reacts with carbon dioxide in the air. Phenolphthalein, which is closely related to the triphenylmethane dyes, was discovered in 1871 by the German chemist Adolf von Baeyer, who prepared it by fusing phenol and phthalic anhydride in the presence of sulfuric acid or zinc chloride, the procedure still employed. A dry sample is collected with a swab or filter paper. Phenolphthalein's pH sensitivity is exploited in other applications: concrete has naturally high pH due to the calcium hydroxide formed when Portland cement reacts with water. This will be explored further down this page. [19], 3,3-Bis(4-hydroxyphenyl)-2-benzofuran-1(3, 3,3-Bis(4-hydroxyphenyl)isobenzofuran-1(3, InChI=1S/C20H14O4/c21-15-9-5-13(6-10-15)20(14-7-11-16(22)12-8-14)18-4-2-1-3-17(18)19(23)24-20/h1-12,21-22H, InChI=1/C20H14O4/c21-15-9-5-13(6-10-15)20(14-7-11-16(22)12-8-14)18-4-2-1-3-17(18)19(23)24-20/h1-12,21-22H, O=C1OC(c2ccccc12)(c3ccc(O)cc3)c4ccc(O)cc4, Except where otherwise noted, data are given for materials in their, Calcium release activated channel § Structure, "Phenolphthalein Exposure Causes Multiple Carcinogenic Effects in Experimental Model Systems", 10.1002/(SICI)1098-2280(1998)31:2<113::AID-EM3>3.0.CO;2-N, "3 Versions of Ex-Lax Are Recalled After F.D.A. In a similar application, some spackling used to repair holes in drywall contains phenolphthalein. What this all means, if you haven't followed, is that two drops of added acid change the pH from 11 to 3.

Omissions? [13], Phenolphthalein has been added to the European Chemicals Agency's candidate list for Substances of Very High Concern (SVHC).[14].

As the concrete reacts with carbon dioxide in the atmosphere, pH decreases to 8.5-9.

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Announcing our NEW encyclopedia for Kids! A positive test indicates the sample contains hemoglobin and, therefore, is likely blood. Proposes Ban on Ingredient", "Ovarian Cancer Risk and Use of Phenolphthalein-Containing Laxatives", "Phenolphthalein - Substance Information - ECHA", Page on different titration indicators, including phenolphthalein, 4'-O-β-D-Glucosyl-9-O-(6''-deoxysaccharosyl)olivil, https://en.wikipedia.org/w/index.php?title=Phenolphthalein&oldid=985067843, Articles with changed DrugBank identifier, Pages using collapsible list with both background and text-align in titlestyle, Articles containing unverified chemical infoboxes, Articles with unsourced statements from April 2020, Creative Commons Attribution-ShareAlike License, Insoluble in benzene and hexane; very soluble in ethanol and ether; slightly soluble in DMSO, An animation of the pH dependent reaction mechanism: H, This page was last edited on 23 October 2020, at 19:21. The neutral point is indicated by the color change of a pH indicator mixed in with the unknown solution. Your IP: 104.131.158.169 As an indicator of a solution’s pH, phenolphthalein is colourless below pH 8.5 and attains a pink to deep red hue above pH 9.0. Phenolphthalein is a potent laxative, which acts within 6–8 hours; its effects may last 3–4 days. Phenolphthalein is another commonly used indicator for titrations, and is … Phenolphthalein has been used for over a century as a laxative, but is now being removed from over-the-counter laxatives[7] because of concerns over carcinogenicity.

Since phenolphthalein is colourless in acid and intensely red in base, it is commonly used as a pH indicator in titrations and also as the active ingredient…, In general, organic compounds are substances that contain carbon (C), and carbon atoms provide the key structural framework that generates the vast diversity of organic compounds.

Basic salt is formed when a strong base and a weak acid react with each other.

Phenolphthalein adopts at least four different states in aqueous solution as a result of pH changes. It also serves as a component of universal indicator, together with methyl red, bromothymol blue, and thymol blue.[2]. Phenolphthalein, (C20H14O4), an organic compound of the phthalein family that is widely employed as an acid-base indicator. In schools, phenolphthalein pH indicator is used in a student activity demonstrating first hand how an “infectious agent” is transmitted through a population.

However, if it remains colorless, it shows that the concrete has undergone carbonation. Phenolphthalein, (C20H14O4), an organic compound of the phthalein family that is widely employed as an acid-base indicator.

When applied, the basic spackling material retains a pink color; when the spackling has cured by reaction with atmospheric carbon dioxide, the pink color fades.[5].

Methyl orange changes color at the pH of mid strength acid. A few drops of alcohol, then a few drops of phenolphthalin, and finally a few drops of hydrogen peroxide are dripped onto the sample. Completing the CAPTCHA proves you are a human and gives you temporary access to the web property. Phenolphthalein was used widely in over-the-counter laxatives, but in 1999 the U.S. Food and Drug Administration banned its use in such medicines because animal studies indicated that it may cause cancer in humans.

If the sample contains hemoglobin, it will turn pink immediately upon addition of the peroxide, because of the generation of phenolphthalein.

In the methyl orange case, the half-way stage where the mixture of red and yellow produces an orange colour happens at pH 3.7 - nowhere near neutral.

It was discovered in 1871 by Adolf von Baeyer. • Corrections?


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