Naphtholphthalein

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
Naphtholphthalein
Names
IUPAC name
3,3-bis(4-hydroxynaphthalen-1-yl)-2-benzofuran-1-one
Other names
1-Naphtholphthalein, alpha-naphtholphthalein, naphtholphthalein blue
Identifiers
3D model (JSmol)
97816
ChemSpider
ECHA InfoCard 100.008.979
UNII
Properties
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) [1]
Insoluble
Hazards
Main hazards Irritant
GHS pictograms [1]
GHS Signal word Warning
GHS hazard statements
H315, H319, H335[1]
P261, P305+351+338[1]
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

References

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