Aqueous solution of orthoboric acid can be titrated against sodium hydroxide using phenolphthalein indicator only in presence of

An aqueous solution of boric acid undergoes titration with NaOH using phenolphthalein as an indicator, only in the presence of cis-glycerol and catechol. Both cis-glycerol and catechol are polyhydroxy compounds and orthoboric acid (or boric acid) forms a stable cyclic complex in the polyhydroxy compounds. This helps in the release of H⁺ as H₃O⁺ in the solution. This indicates that polyhydroxy compounds increase the acidic strength of boric acid, thereby can be titrated with sodium hydroxide using phenolphthalein.