Changes
→Formulae with chemic module
\usemodule[chemic]
\startformula
\chemical{2H_2,+,0_2O_2,->,2H_202H_2O}
\stopformula
</texcode>
\usemodule[chemic]
\startformula
\chemical{2H_2,+,0_2O_2,->,2H_202H_2O}
\stopformula
</context>