Pigments & Colorants
REACH
Phenolphthalein
CAS Number
77-09-8
EC Number
201-004-7
Industries: Textiles, Leather & Paper
What is Phenolphthalein?
Phenolphthalein (CAS 77-09-8) is a pH-sensitive indicator compound that transitions from colorless to vivid pink-red under alkaline conditions.
Where is Phenolphthalein used?
- Titration and analytical chemistry: standard tool
- Industrial settings: colorimetric marker for detecting alkalinity in substrates, coatings, and treated surfaces
- Printing and packaging: indicator solutions test paper substrates for compatibility with inks and adhesives
- Textile and leather: verify pH of dye baths, wash liquors, and finishing treatments where residual alkali affects quality
- Concrete and construction material testing: standard reagent for carbonation depth assessment on cut surfaces, revealing the boundary between carbonated and uncarbonated zones
- Personal care: bench-level QC tool to confirm alkalinity of cream, soap, and hair relaxer formulations
Other Names (Synonyms)
Prulet|Ex-Lax|Alpha-di(p-hydroxyphenyl)phthalide|3,3-Bis(p-hydroxyphenyl)phthalide|3,3-Bis(4-hydroxyphenyl)phthalide|3,3-Bis(4-hydroxyphenyl)-2-benzofuran-1(3H)-one|3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone|Phenolax
What are the physical properties of Phenolphthalein?
Melting Point 262.5 °C
Boiling Point 417.49°C (rough estimate)
Density 1.277 g/cm³ @ Temp: 32 °C
Flash Point 24 °C
Appearance white to light yellow crystal powde
Color White to yellow-white
Odor Odorless
Form Solid
Water Solubility <0.1 g/100 mL
Vapor Pressure <0.00001 Pa ( 50 °C)
Refractive Index 1.5400 (estimate)
pH 7.8～10.0
Log P 2.410
How is Phenolphthalein classified and handled safely? Learn More
Danger
GHS08· Health Hazard GHS07· Irritant
Hazard Statements
H317 May cause an allergic skin reaction
H319 Causes serious eye irritation
H341 Suspected of causing genetic defects
H350 May cause cancer
Precautionary Statements
P203 Obtain, consult and follow expert instructions for use.
P260 Do not breathe dust/fume/gas/mist/vapours/spray.
P261 Avoid breathing dust/fume/gas/mist/vapours/spray.
P264 Wash … thoroughly after handling.
Which trade and regulatory codes apply to Phenolphthalein?
HS Code 29322910
Storage Class 6.1C - Combustible acute toxic Cat.3
toxic compounds or compounds which causing chronic effects
WGK (Germany) 3