Abstract: A machine for pumping liquid chlorine employs an upright shaft sump pump which is confined in a hermetically sealed housing and has a tubular supporting element surrounding the pump shaft. The latter is mounted in overhung position and is adjacent to a pressure pipe which conveys the pressurized liquid. The shaft seal is kept out of contact with the liquid by the housing as well as by a body of inert gas which is supplied to the interior of the housing and to the space between the shaft and the tubular element at a pressure depending on the pressure of inflowing liquid chlorine and being sufficiently high to prevent the inflow of liquid chlorine into the housing and/or tubular element when the pump is idle. The main impeller on the pump shaft is made integral with an auxiliary impeller which constitutes a hydrodynamic shaft seal and prevents the flow of conveyed liquid chlorine into the tubular element from below.