In the qualitative analysis of $BO _{3}^{3-}$ radical, mixture is heated with conc. $H _{2} SO _{4}$ and little alcohol when trialkyl borate is obtained. The vapours of trialkyl borate $B ( O R)_{3}$ or $R_{3} BO _{3}$ burn with green edged flame.
$2 BO _{3}^{3-}+3 H _{2} SO _{4} \longrightarrow 3 SO _{4}^{2-}+2 H _{3} BO _{3} $
$H _{3} BO _{3}+3 R OH \longrightarrow \underset{\text{Trialkaly borate}}{R_{3} BO _{3}}+3 H _{2} O$