${\text{CO}}_2^{}+\text{C}\stackrel{\text{above}}{\to }2\text{CO}{\text{CO}}_2^{}+\text{C}\underset{\text{below}}{\overset{\text{above}}{\to }}2\text{CO}{\text{CO}}_2^{}+\text{C}\underset{\text{below}}{\overset{\text{above}}{\to }}2\text{CO}A\stackrel{+{\text{H}}_2^{}\text{O}}{\to }BA\stackrel{+{\text{H}}_2^{}\text{O}}{\to }B{\text{SO}}_4^{2-<!--\; -\; -->}+{\text{Ba}}_{}^{2+}⟶<!--\; ⟶\; -->{\text{BaSO}}_4^{}\downarrow <!--\; \downarrow \; -->A\stackrel{\text{enclose spaces!}}{\leftrightarrow }{A}^{\prime }$