Phenolphthalein: Difference between revisions
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== Description == | == Description == | ||
[[[SliderGallery rightalign|phenolphthalein.jpg~Chemical structure]]] | |||
Pale yellow powder that is used as a pH indicator. Phenolphthalein is a triphenylmethane salt whose three aromatic rings produce a red chromophore in basic and neutral solutions. The conjugation is disrupted in acidic solutions resulting in a clear solution. Thus phenolphthalein is an effective acid base indicator for titrations of mineral acids, organic acids and alkalis. It is prepared as a 1% solution in ethanol. In solutions with a pH below 8.5 | Pale yellow powder that is widely used as a pH indicator. Phenolphthalein was first synthesized in 1871 by German chemist Adolf von Baeyer by reacting phenol and phthalic anhydride, initially intended as a dye. It is a triphenylmethane salt whose three aromatic rings produce a red chromophore in basic and neutral solutions. The conjugation is disrupted in acidic solutions resulting in a clear solution. Thus, phenolphthalein is an effective acid-base indicator for titrations of mineral acids, organic acids and alkalis. It is prepared as a 1% solution in ethanol. In solutions with a pH below 8.5 phenolphthalein is colorless; for solutions above pH 9 are bright pink-red. | ||
== Synonyms and Related Terms == | == Synonyms and Related Terms == | ||
3,3-bis(p-hydroxyphenyl)phthalide; 3,3-bis(4-hydroxyphenyl)-1(3H)-isobenzofuranore | 3,3-bis(p-hydroxyphenyl)phthalide; 3,3-bis(4-hydroxyphenyl)-1(3H)-isobenzofuranore | ||
== Risks == | |||
== | |||
* Toxic by ingestion, even small amounts will cause illness. | |||
* Suspected carcinogen. | |||
* Contact may cause irritation. | |||
* ThermoFisher: [https://www.fishersci.com/store/msds?partNumber=P79500&productDescription=PHENOLPHTHALEIN+CERT+ACS+500G&vendorId=VN00033897&countryCode=US&language=en SDS] | |||
== Physical and Chemical Properties == | |||
* Appearance = white powder | |||
* Soluble in ethanol, ether and alkalis. | |||
* Insoluble in water, benzene, hexane. | |||
* Solution: Dissolve 1 g phenolphthalein in 50 ml ethanol and add 50 ml water. | |||
* Composition = (C6H4OH)2C2O2C6H4 (mol. wt. = 318.33 g.mol.) | |||
* CAS = 77-09-8 | |||
* Melting Point = 258-262 C | |||
* Density = 1.299 g/ml | |||
== | ==Resources and Citations== | ||
* G.S.Brady, ''Materials Handbook'', McGraw-Hill Book Co., New York, 1971 Comment: p. 184 | * G.S.Brady, ''Materials Handbook'', McGraw-Hill Book Co., New York, 1971 Comment: p. 184 | ||
* Richard S. Lewis, ''Hawley's Condensed Chemical Dictionary'', Van Nostrand Reinhold, New York, 10th ed., 1993 | * Richard S. Lewis, ''Hawley's Condensed Chemical Dictionary'', Van Nostrand Reinhold, New York, 10th ed., 1993 | ||
* S.R.Trotman, E.R. Trotman, ''Textile Analysis'', J.B. Lippincott Company, Philadelphia, 1932 | * S.R.Trotman, E.R. Trotman, ''Textile Analysis'', J.B. Lippincott Company, Philadelphia, 1932 | ||
* ''The Merck Index'', Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 | * ''The Merck Index'', Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 | ||
* Thomas B. Brill, ''Light Its Interaction with Art and Antiquities'', Plenum Press, New York City, 1980 | * Thomas B. Brill, ''Light Its Interaction with Art and Antiquities'', Plenum Press, New York City, 1980 | ||
* ''CRC Handbook of Chemistry and Physics'', Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: Solution: Dissolve 1 g phenolphthalein in 50 ml alcohol and add 50 ml water. | * ''CRC Handbook of Chemistry and Physics'', Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: Solution: Dissolve 1 g phenolphthalein in 50 ml alcohol and add 50 ml water. | ||
* Wikipedia: [https://en.wikipedia.org/wiki/Phenolphthalein Phenolphthalein] Accessed Feb. 2026 | |||
[[Category:Materials database]] | [[Category:Materials database]] | ||
Latest revision as of 13:00, 25 February 2026
Description
Pale yellow powder that is widely used as a pH indicator. Phenolphthalein was first synthesized in 1871 by German chemist Adolf von Baeyer by reacting phenol and phthalic anhydride, initially intended as a dye. It is a triphenylmethane salt whose three aromatic rings produce a red chromophore in basic and neutral solutions. The conjugation is disrupted in acidic solutions resulting in a clear solution. Thus, phenolphthalein is an effective acid-base indicator for titrations of mineral acids, organic acids and alkalis. It is prepared as a 1% solution in ethanol. In solutions with a pH below 8.5 phenolphthalein is colorless; for solutions above pH 9 are bright pink-red.
Synonyms and Related Terms
3,3-bis(p-hydroxyphenyl)phthalide; 3,3-bis(4-hydroxyphenyl)-1(3H)-isobenzofuranore
Risks
- Toxic by ingestion, even small amounts will cause illness.
- Suspected carcinogen.
- Contact may cause irritation.
- ThermoFisher: SDS
Physical and Chemical Properties
- Appearance = white powder
- Soluble in ethanol, ether and alkalis.
- Insoluble in water, benzene, hexane.
- Solution: Dissolve 1 g phenolphthalein in 50 ml ethanol and add 50 ml water.
- Composition = (C6H4OH)2C2O2C6H4 (mol. wt. = 318.33 g.mol.)
- CAS = 77-09-8
- Melting Point = 258-262 C
- Density = 1.299 g/ml
Resources and Citations
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 184
- Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
- S.R.Trotman, E.R. Trotman, Textile Analysis, J.B. Lippincott Company, Philadelphia, 1932
- The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983
- Thomas B. Brill, Light Its Interaction with Art and Antiquities, Plenum Press, New York City, 1980
- CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: Solution: Dissolve 1 g phenolphthalein in 50 ml alcohol and add 50 ml water.
- Wikipedia: Phenolphthalein Accessed Feb. 2026