What are the uses of phenolphthalein 77-09-8 ?

   The discoloration range of phenolphthalein is 8.2 ~ 10.0, so phenolphthalein can only test for bases but not acids.

   Phenolphthalein is a weak organic acid with a colorless lactone structure at pH<8.2 and a red quinone structure at pH>8.2. 

   The quinone form or quinone form of phenolphthalein is very unstable in alkaline media and will slowly be converted into colorless carboxylate form; In the presence of a stronger lye, it will immediately change into a colorless carboxylate form. So, when phenolphthalein drops into the concentrated lye, it starts to turn red, and soon the red color fades to colorless.

   Phenolphthalein is a fine white or yellowish crystal, less soluble in water but more soluble in alcohol. So phenolphthalein is usually prepared into alcohol solution for use. When phenolphthalein is dropped into water or a neutral, acidic aqueous solution, a white turbidity will appear. This is due to the fact that alcohol can be missolvable with water in any proportion, resulting in the precipitation of the water-insoluble phenolphthalein in the reagent.

   The main uses of phenolphthalein are:

(1) For alkali indicator, non-aqueous titration indicator, color layer analysis reagent.

(2) For organic synthesis: It is mainly used for the synthesis of plastics, especially the synthesis of diazanazone polyaryl ether ketone polyaryl ether ketone polymer. This kind of polymer has excellent heat resistance, water resistance, chemical corrosion resistance, heat aging resistance and good processing formability. Many of the fibers, coatings and composite materials made from them are widely used in electronic and electrical appliances, mechanical equipment, transportation, aerospace, atomic engineering and military fields;

(3) Pharmaceutical raw materials: pharmaceutical laxative, can stimulate the intestinal wall, cause intestinal peristalsis to promote defecation. Suitable for habitual stubborn constipation, tablets, suppositories and other dosage forms;