Hydrogen estimation

$$ \% H = \frac{2}{18} \times \frac{\mathrm{mass of } H_2O}{\mathrm{mass of organic compound}} \times 100 = \frac{1}{9} \times \frac{\mathrm{mass of } H_2O}{W} \times 100 $$
Percentage of hydrogen calculated from mass of H₂O produced during combustion (W = mass of compound).