Naphtholphthalein

Naphtholphthalein
Names
	IUPAC name 3,3-bis(4-hydroxynaphthalen-1-yl)-2-benzofuran-1-one
	Other names 1-Naphtholphthalein, alpha-naphtholphthalein, naphtholphthalein blue
Identifiers
CAS Number	596-01-0
Beilstein Reference	97816
ChemSpider	62215
Jmol 3D model	Interactive image
PubChem	68993
	SMILES C1=CC=C2C(=C1)C(=CC=C2O)C3(C4=CC=CC=C4C(=O)O3)C5=CC=C(C6=CC=CC=C65)O ;
Properties
Chemical formula	C28H18O4
Molar mass	418.45 g·mol−1
Appearance	Colorless-reddish to blue-green solid
Melting point	238–240 °C (460–464 °F; 511–513 K)
Solubility in water	Insoluble
Vapor pressure	{{{value}}}
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

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α-Naphtholphthalein (C₂₈H₁₈O₄) is a pH indicator with a visual transition from colorless/reddish to greenish/blue at pH 7.3–8.7.

Naphtholphthalein (pH indicator)
below pH 7.3		above pH 8.7
7.3	⇌	8.7

References

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