A product of the interaction of phenol and phthalic anhydrid.

Properties : Phenolphthalein occurs as white, or grayish-white crystals or as an amorphous powder; slightly soluble in water and freely soluble in alcohol. Its solutions in acid liquids are colorless, but turn led when the liquid is made alkaline.

Action and Uses: Phenolphthalein acts as a purgative, but appears to possess no further physiologic action, except that it may cause some irritation of the rectum and lower bowel.

Dosage: The dosage must vary according to its effect, from 0.05 gm. to 0.5 gm., or from 1 to 8 grains. A case of mild poisoning is reported from taking 1 gm. (15 grains).