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Phthalic Anhydride

CAS Number:85‑44‑9

Synonyms:1,2‑Benzenedicarboxylic anhydride; Phthalic acid anhydride; 1,3‑Isobenzofurandione

Chemical Formula:C₈H₄O₃

Product Introduction

A white to pale-yellow crystalline solid (flakes or lumps) with a pungent, acrid odor. It is the principal industrial feedstock for phthalate plasticizers, alkyds, polyester resins, dyes, and lacquers.

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Physical & Chemical Properties

Property	Value
Appearance	White crystalline flakes or granules
Odor	Strong, acrid/choking
Density	~1.53 g/cm³ @ 20 °C
Melting Point	~131–134 °C
Boiling Point / Sublime	~284–295 °C (sublimes)
Vapor Pressure	~0.00052 mmHg @ 25 °C
Solubility in Water	~0.62 g/100 g @ 20 °C
Flash Point	~152 °C (closed cup)
Vapor Density	~5× air

Applications

Precursor for alkyd resins, polyester resins, and glyptal (coatings and laminates)
Manufacture of plasticizers (e.g., phthalate esters for PVC)
Used in the synthesis of dyes, pigments (anthraquinone, fluorescein), and epoxy hardeners
Intermediate for producing phenolphthalein, phthalimide, and phthalein dyes