Ciric acid is a weak organic acid and its ionization is very small in aqueous solution. On the other hand solution of FeCl3 undergoes hydrolysis to form Fe(OH)3 increasing H-ions conc. in solution which further decrease the ionization of the acid. Therefore a basic medium should be used to decrease the conc. of hydroxyl ions to prevent hydrolysis of Fe(OH)3 and to increase the ionization of acid.

Dear Wael,

In the reaction of trisodium citrate and ferric chloride. I suggest adding the Na3-citrate into the FeCl3 soln, because in opposite order FeOOH will be deposited due to alkaline pH of trisodium citrate.

Citric acid is a tribasic acid, but the second and mainly the third acid dissociation constant value show that it is a weak acid. So, when you used NaHCO3, only the first acid fucntion was substituted with sodium. All three had to be sodium substituted.

The system not as easy, because of complex formation, basic salt formaton, etc., so the molar ratio should be kept to be 1:1.

Ciric acid is a weak organic acid and its ionization is very small in aqueous solution. On the other hand solution of FeCl3 undergoes hydrolysis to form Fe(OH)3 increasing H-ions conc. in solution which further decrease the ionization of the acid. Therefore a basic medium should be used to decrease the conc. of hydroxyl ions to prevent hydrolysis of Fe(OH)3 and to increase the ionization of acid.