A method for the automated production of liquid SO.sub.2 having a purity above 99.9% from elemental sulfur and pure oxygen, in the presence of SO.sub.2 recirculated from a closed circuit production system. The temperature of the combustion is controlled by means of pre-defined S, O.sub.2 and SO.sub.2 ratios. The automation is made based on oxygen sensors and on sulfur and SO.sub.2 flow meters with their respective control connections and proportional valves permitting a fine control of the sulfur combustion reaction. Liquefaction of gaseous SO.sub.2 produced is carried out alternatively by a cool plant working between -10 and -60.degree. C. or with a compression unit working at a pressure between 3.8 and 5.0 bar. The automation permits an optimum temperature control and a clean production of SO.sub.2.