Question

Why boric acid is strong acid in presence of poly hydroxy compounds?

Answer 1

The postulated existence of complexes of boric acid with polyhydroxy organic com- pounds in ... hydroxy compounds will complex with boric .... fied to pH 2 with 5 ml of 0.1 N HCl. 

Answer 2

is obtained from borax by treating with dil. HCl or dil.H2SO4 ,

Na2B4O7 + 2HCI + 5H2O ———→ 2NaCI + 4H3BO3        

It can also be obtained from the mineral colemanite by passing SO2  through a mixture of powdered mineral in boiling water,

Ca2B6 O11 + 4SO2 + 11H2O ——→ 2Ca ( HSO3)2 + 6H3BO3

Properties: (a) It is a very weak monobasic acid, does not act as a proton doner but behaves as a Lewis acid i.e. it accepts a pair of electrons from OH- ion of H2O , 

H3BO3 + H2O ——→ [B (OH )4 ]- + H+           

It acts as a strong acid in presence of polyhydroxy compounds such as glycerol, mannitol etc. and can be titrated against strong alkali .