Abstract: An apparatus for the controlled cooling of chemical tanks containing a chemical which must be kept at a first prescribed temperature includes at least one heat-exchanger coil immersed inside a chemical tank and through which there is made to circulate a flow of an inert gas. The apparatus includes a storage system for storing and cooling a prescribed volume of inert gas at a second prescribed temperature lower than the first prescribed temperature, feeding means for feeding the storage means with inert gas coming from a main supply line, and valve means interposed between the storage means and an inlet of the at least one heat-exchanger coil for controlling the supply of cooled inert gas to the heat-changer coil.