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What is Phenolphthalein CAS 77-09-8

Views: 1     Author: Site Editor     Publish Time: 22-04-2022      Origin: Site



Melting point: 261-263℃ (lit.)

Boiling point: 417.49℃(rough estimate)

Density: 1.27 g/cm3 at 32℃

Refractive index: 1.5400 (estimate)

Flash point: 24℃


CAS 77-09-8


Phenolphthalein is a weak organic acid. It is a white or slightly yellow crystal at room temperature. It is odorless and tasteless. It is insoluble in water but easily soluble in alcohol (ethanol) and ether. Dissolved in alcohol solution to make acid-base indicator, it is colorless in acid solution, red in alkali solution or alkali metal carbonate solution, but if it is in concentrated alkali solution, it will produce colorless trimetallic Salt, the redness fades. In view of this characteristic, it is often used as an indicator for acid-base titration in the laboratory. When the phenolphthalein reagent is dropped into water or a neutral or acidic aqueous solution, white turbidity will appear. This is because alcohol is easily soluble in water, so that phenolphthalein, which is insoluble in water, is precipitated in the reagent.


The main uses of phenolphthalein: 1. Pharmaceutical raw materials in the pharmaceutical industry: suitable for habitual stubborn constipation, in various dosage forms such as tablets and suppositories. 2. Used in organic synthesis: mainly used in the synthesis of plastics, especially in the synthesis of naphthalene ketone polyaryletherketone polyaryletherketone polymers, which have excellent heat resistance, water resistance, chemical resistance Corrosion, heat aging resistance and good processability, fibers, coatings and composite materials made of it are soon widely used in electronic appliances, mechanical equipment, transportation, aerospace, atomic energy engineering and military fields. 3. Used as acid-base indicator, indicator for non-aqueous titration, and reagent for chromatographic analysis.

Pharmacological action

Phenolphthalein is a stimulant laxative that mainly acts on the large intestine. After oral administration, it forms soluble sodium salts in the alkaline environment of the intestinal tract, stimulates the inner plexus of the intestinal wall, directly acts on the intestinal smooth muscle, and increases the intestinal peristalsis. At the same time, phenolphthalein inhibits the absorption of water in the intestinal tract, so that water and electrolytes accumulate in the colon, resulting in a laxative effect. The strength of its action is related to the alkaline size in the intestine, and its effect is mild, rarely causing intestinal spasm.


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