Phenolphthalein

Phenolphthalein

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
SMILES O=C1OC(c2ccccc12)(c3ccc(O)cc3)c4ccc(O)cc4
Properties
Chemical formula	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)
Boiling point	Decomposes
Solubility in water	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

• 

  Phenolphthalein's color in basic solution.

• 

  Phenolphthalein sample (middle), and dissolved in an acid (left) and a base (right).

References

Relevant Sciencemadness threads

• Phenolphthalein Decomposition
• Phenolphthalein ( 3,3-bis(4-hydroxyphenyl)isobenzofuran-1(3H)-one ), h2so4 and h2o2