Abstract: In a process for manufacturing sulphuric acid by catalytic conversion of gaseous sulphur dioxide to sulphur trioxide in the presence of dry air and under high pressure, the improvement comprising feeding the converted gas stream under high pressure to an absorbing unit, circulating essentially sulphur dioxide-free sulphuric acid through the absorbing unit to absorb the sulphur trioxide and unconverted sulphur dioxide from said converted gas stream, depressurizing the acid, simultaneously stripping the sulphur dioxide from the acid by means of air or a sulphur dioxide-free gas and removing moisture from said air or sulphur dioxide-free gas by means of said acid, cooling the resulting essentially sulphur dioxide-free acid and recirculating at least part of it to the absorbing unit. In a preferred embodiment, the process comprises the additional step of condensing part of the sulphur trioxide and unconverted sulphur dioxide constituting the converted gas stream and feeding the remainder to the absorbing unit.