Naphtholphthalein

Naphtholphthalein
Names
	Preferred IUPAC name 3,3-Bis(4-hydroxynaphthalen-1-yl)-2-benzofuran-1(3H)-one
	Other names 1-Naphtholphthalein, alpha-naphtholphthalein, naphtholphthalein blue
Identifiers
CAS Number	596-01-0 ;
3D model (JSmol)	Interactive image;
Beilstein Reference	97816
ChemSpider	62215 ;
ECHA InfoCard	100.008.979
PubChem CID	68993;
UNII	2QEG1706NN ;
CompTox Dashboard (EPA)	DTXSID70208273 ;
	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	418.448 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
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Irritant
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P305+P351+P338
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

α-Naphtholphthalein (C₂₈H₁₈O₄) is a phthalein dye used as 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

^ ^a ^b ^c ^d α-Naphtholphthalein

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[sigma-1] α-Naphtholphthalein

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