Method of preparing phthalide

An improvement in a process for preparing phthalide by reacting chlorophthalide with hydrogen in the presence of a catalyst at a temperature between 50 DEG and 350 DEG C., the improvement residing in carrying out the process in the absence of a hydrogen chloride acceptor, flowing the chlorophthalide continuously in fluid form through a solid catalyst bed in a reactor, passing the hydrogen through in such an excess so as to sweep off the hydrogen chloride formed and withdrawing phthalide in fluid form.