Boric acid can be titrated against sodium hydroxide using methyl orange as indicator only in the presence of polyhydroxy compounds wlike catechol, manniton etc. explain.

Explanation

`B(OH)_(3)` reacts with NaOH to form sodium metaborate.
`B(OH)_(3)+NaOH to Na^(+)BO_(2)^(-)+2H_(2)O`
the end point during the titration of `H_(3)BO_(3)` with NaOH is not sharp since `NaBO_(2)` undergoes excessive hydrolysis to give back `H_(3)BO_(3)` and `NaOH`. however, when certain polyhydroxy compounds such as catechol, glycerol, mannitol or sugars are added to the titration solution the metaborate ion combines with polyhydroxy compound to for a complex.

Due to the formation of this complex, `BO_(2)^(-)` ion does not undergoes hydrolysis. As a result, boric acid behaves as a strong monobasic acid and the end point can thus be easiliy detected.