Chapter 7, Problem 75E

${\text{Co}}_a{\text{S}}_b{\text{O}}_c\cdot \text{X}{\text{H}}_{\text{2}}\text{O}$ is the general formula of a certain hydrate. When $43.0\text{g}$ of the compound is heated to drive off the water, $26.1\text{g}$ of anhydrous compound is left. Further analysis shows that the percentage composition by mass of the anhydrate is $42.4\%\text{Co}$, $23.0\%\text{S}$, and $34.6\%\text{O}$. Find the empirical formula of (a) the anhydrous compound and (b) the hydrate. (Hint: treat the anhydrous compound and water just as you treated elements in calculating $\text{X}$ in the formula of the hydrate.)