CONTINUOUS CRYSTALLISATION METHOD

The invention provides a method of purifying 5-acetamido-N, N'-bis(2,3-dihydroxypropyl)- 2,4,6-triiodoisophathalamide, comprising adding a portion of acid to a stream comprising crude 5-acetamido-N, N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodoisophathalamide in a solvent and continuously crystallising the 5-acetamido-N, N'-bis(2,3-dihydroxypropyl)-2,4,6- triiodoisophathalamide from the crude 5-acetamido-N, N'-bis(2,3-dihydroxypropyl)-2,4,6- triiodoisophathalamide, with removal of at least a fraction of the solvent, wherein the crystallisation is carried out in a continuous reactor, wherein the continuous reactor is a plug flow reactor. At least three further portions of acid are added to the continuous reactor during the crystallisation. La invención proporciona un método para purificar 5-acetamido-N,N'-bis(2,3-dihidroxipropil)-2,4,6-triyodoisoftalami da, que comprende agregar una porción de ácido a una corriente que comprende 5-acetamido-N,N'-bis(2,3-dihidroxipropil)-2,4,6-triy odoisoftalamida cruda en un disolvente y cristalizando continuamente la 5-acetamido-N,N'-bis(2,3-dihidroxipropil)-2,4,6- triyodoisoftalamida a partir de la 5-acetamido-N,N'-bis(2,3-dihidr oxipropil)-2,4,6-triyodoisoftalamida cruda, con eliminación de al menos una fracción del disolvente, en donde la cristalización se lleva a cabo en un reactor continuo, en donde el reactor continuo es un reactor de flujo pistón. Se añaden al menos tres porciones más de ácido al reactor continuo durante la cristalización.