When ${\mathrm{PCl}}_3$  reacts with sulphuric acid, sulphuryl chloride is formed as one of the products. This shows that sulphuric acid

When PCl₃​ reacts with sulphuric acid, sulphuryl chloride is formed as the final product. This shows that sulphuric acid has two hydroxyl groups in its structure.

$2{\mathrm{PCl}}_3+3{\mathrm{H}}_2{\mathrm{SO}}_4\to 3{\mathrm{SO}}_2{\mathrm{Cl}}_2+2{\mathrm{H}}_3{\mathrm{PO}}_3$