The molarity of $1 \mathrm{~L}$ orthophosphoric acid $\left(\mathrm{H}_3 \mathrm{PO}_4\right)$ having $70 \%$ purity by weight (specific gravity $1.54 \mathrm{~g} \mathrm{~cm}^{-3}$) is __________ $\mathrm{M}$.

(Molar mass of $\mathrm{H}_3 \mathrm{PO}_4=98 \mathrm{~g} \mathrm{~mol}^{-1}$)