The invention relates to a cylinder for storing coolant, with which a heat exchanger of an air-conditioning circuit is to be provided, said cylinder defining a first cavity (2) accommodating a desiccator, and a second cavity (3) capable of enabling fluid communication with said circuit. Said cylinder is configured such that said first (2) and second (3) cavities remain isolated from each other up to a first inner pressure threshold, and are placed in fluid communication once said second cavity (3) is subjected to a second inner pressure threshold that is greater than the first threshold. The invention also relates to a condenser provided with such a cylinder.