Phenolphthalein

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Phenolphthalein
Phenolphthalein bottle sample solutions.jpg
Phenolphthalein sample (center) with original bottle (left) and in solution at acidic and neutral pH (colorless) and basic pH (pink)
Names
IUPAC name
3,3-bis(4-hydroxyphenyl)isobenzofuran-1(3H)-one
Systematic IUPAC name
Phenolphthalein
Other names
HIn
phph
Identifiers
Jmol-3D images Image
Properties
C20H14O4
Molar mass 318.33 g/mol
Appearance White powder
Odor Odorless
Density 1.3 g/cm3 (at 20 °C)
Melting point 262.5 °C (504.5 °F; 535.6 K)[1]
Boiling point Decomposes
0.04 g/100 ml
Solubility Very soluble in acetone, ethanol and pyrene
Soluble in chloroform, diethyl ether, and toluene
Slightly soluble in carbon disulfide
Insoluble in benzene, hexane, petroleum ether
Vapor pressure 6.7·10-13 mm Hg at 25 °C
Hazards
Safety data sheet Acros Organics
Flash point Non-flammable
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Phenolphthalein is an organic chemical compound, often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions.

Properties

Chemical

Phenolphthalein is colorless at acidic and neutral pH and pink at basic pH.

Physical

Phenolphthalein is a white solid, poorly soluble in water but very soluble in acetone and ethanol.

Availability

Phenolphthalein is sold by various chemical suppliers.

Preparation

Phenolphthalein can be prepared by reacting phenol with phthalic anhydride, in the presence of anhydrous aluminium chloride and zinc chloride. Thionyl chloride can substitute aluminium chloride.

2 C6H5OH + C6H4C2O3 → C20H14O4

Projects

  • Base indicator
  • Ferroxyl indicator solution
  • Kastle–Meyer test

Handling

Safety

Phenolphthalein, if taken orally, is mildly toxic, a suspected carcinogen and a powerful laxative. Several decades ago, it was commonly used as such in medicine. Today, less toxic laxatives are used.

Storage

Phenolphthalein should be kept in closed bottles, away from acidic vapors.

Disposal

Can be destroyed with a strong oxidizer, such as Fenton's reagent, chromic acid or piranha solution, neutralized and poured down the drain.

Gallery

References

  1. Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V4 3297

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