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2-[Bis(4-hydroxyphenyl)methyl]benzoic acid;


Molecular structure:






White to almost white powder

White powder

Melting Point

It melts at about 260℃


Related substances



Heavy metals            









Loss on drying



Sulphated ash









Y and M <100cfu/g

E-coli Absent

Staphylococcus Aureus Absent

Pseudomonas Aeruginosa Absent

Albicans Saccharomyces Absent


The results conforms with enterprise standards


Chemical properties

Phenolphthalein is a weak organic acid. It is white or slightly yellowish fine crystals at room temperature. It is odorless and tasteless. It is insoluble in water but soluble in alcohol (ethanol) and ether. Dissolve in alcohol solution to make acid-base indicator, which is colorless in acid solution, red in alkali solution or carbonate solution of alkali metal, but if concentrated alkali solution, it will produce colorless trimetal Salt, the red faded. In view of this characteristic, it is often used as an indicator of acid-base titration in the laboratory, and the pH value of the color change range is 8.2 to 10.0, from colorless to red. When the phenolphthalein reagent is dropped into water or a neutral, acidic aqueous solution, a white turbidity will appear. This is due to the fact that alcohol is easily soluble in water, and the phenolphthalein which is difficult to dissolve in the reagent is precipitated.

Other main uses are as follows:

Pharmaceutical raw materials in the pharmaceutical industry: suitable for habitual stubborn constipation, with various dosage forms such as tablets and suppositories

Used in organic synthesis: mainly used to synthesize plastics, especially synthetic diazonaphthone polyaryl ether ketone polyaryl ether ketone polymer, which has excellent heat resistance, water resistance, chemical resistance Corrosion, heat aging resistance and good processability, the fibers, coatings and composite materials made from it are soon widely used in electronic and electrical appliances, mechanical equipment, transportation, aerospace, atomic energy engineering and military fields.

Used for acid-base indicator, indicator for non-aqueous solution titration, and reagent for chromatographic analysis. Phenolphthalein can be prepared by mixing phthalic anhydride with phenol and co-heating with sulfuric acid.

Phenolphthalein test paper

Phenolphthalein test paper is one of the simple test papers commonly used in chemical analysis. It has strong pertinence, it is red when meeting alkali, and it is colorless in acidic and neutral solution. Check if there is ammonia in the air, it will also appear light red. The preparation method is simple, soak the filter paper in the phenolphthalein solution, absorb and reach saturation, then take out and dry it.

Pharmacology and Toxicology

Phenolphthalein can be used to treat habitual refractory constipation. It mainly acts on the colon. After oral administration, it slowly decomposes under the action of small intestine alkaline intestinal fluid to form soluble sodium salts, thereby stimulating the nerve plexus in the intestinal wall. Peristalsis increases, and at the same time it can inhibit the absorption of water in the intestine, allowing water and electrolytes to accumulate in the colon and produce a laxative effect. Its effect is mild and rarely causes intestinal spasm.


After oral administration, about 15% is absorbed. The absorbed drugs are mainly excreted in urine or feces in the form of glucuronide, and partly excreted into the intestinal cavity through bile, where they are reabsorbed in the intestine to form intestinal-hepatic circulation and prolong the effect. time. Soft stools are excreted 4 to 8 hours after medication, and it takes 3 to 4 days for one-time administration.

Adverse reactions

Phenolphthalein mainly acts on the large intestine, producing semi-liquid stool within 4 to 8 hours with little or no colic. As a result of enterohepatic circulation, the effect of a single dose can last 3 to 4 days. This drug is an active member of many laxative formulations that can be legally sold without a doctor’s prescription. Serious adverse effects are rare but can occur in overdose. Phenolphthalein should be avoided for the elderly because its long-lasting effect can seriously deplete water and electrolytes. Dermatitis (fixed rash, itching, burning sensation, blistering, and residual pigmentation) can occur in allergic patients. There have been reports of fatal allergic reactions, but it has not been determined to have an absolute pathogenic relationship with phenolphthalein. Non-thrombocytopenic purpura has been reported occasionally, and dehydration and electrolyte disturbance due to excessive diarrhea may occur even after long-term application. Phenolphthalein makes alkaline urine or feces pink.


Phenolphthalein may cause irreversible damage to the body. Wear protective clothing and gloves when using.




Store in a dry, well-ventilated place away from direct sunlight.


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