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 rarr 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`
`NaBO_(2) + 2H_(2)O hArr B(OH)_(3) + NaOH`
However, when certain polyhydroxy compounds such as catechol, glycerol, mannitol or sugarsor any other cis-1,2,3 is added to titration solution, the metaborate ion combaines with polyhydroxy compound to form a complex.

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