Crystalline Oxalic acid is ${\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_4.2{\mathrm{H}}_2\mathrm{O}$. Its molecular weight is 126. Amorphous Oxalic acid is ${\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_4$ with molecular weight of 90.

Equivalent weight=$\frac{\mathrm{Molecular} \mathrm{weight}}{\mathrm{Basicity} \mathrm{of} \mathrm{acid} \mathrm{or} \mathrm{No} \mathrm{of} {\mathrm{e}}^{-1} \mathrm{transfered} \mathrm{by} \mathrm{one} \mathrm{molecule}}$=$\frac{126}{2}=63$