Boron does not dissolves in:

Crystalline boron shows inert behavior and does not react with HCl.

When Boron reacts with alkali, it forms boric acid and evolves hydrogen gas. Reaction of boron with NaOH:

$2\mathrm{B}+6\mathrm{NaOH}\to 2{\mathrm{Na}}_3{\mathrm{BO}}_3+3{\mathrm{H}}_2$

Boron react with SiO₂ to form boric acid and Si.

$4\mathrm{B}+3{\mathrm{SiO}}_2\to 3\mathrm{Si}+2{\mathrm{B}}_2{\mathrm{O}}_3$

Boron react with concentrated nitric acid and produces boric acid and NO

$\mathrm{B}+{\mathrm{HNO}}_3+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_3{\mathrm{BO}}_3+\mathrm{NO}$