1,185,495. Ion exchange. PERMUTIT CO. Ltd. 30 Aug., 1968 [12 June, 1967], No. 27063/67. Heading B1J. An ion exchange resin, for use in a process for softening or demineralising water by passing the water upwards through the bed of resin in an absorber, is regenerated by intermittently removing individual slugs of resin from the bottom of the absorber, each slug being caused to move upwards through a regenerator such that in the regenerator the slug forms a layer of greater depth than transverse dimension, the slug being regenerated by downward flow of regenerant and each regenerated slug being withdrawn from the regenerator downwards to and through an outlet from which it is returned to the top of the bed of the absorber. A plant suitable for carrying out the ion exchange and regeneration comprises an absorber 1, having water inlet 4 and outlet 6 and containing two slugs of resin 35 and 36, which is connected to a transfer vessel 8, of appropriate size to hold one slug of resin, into which the lowermost slug of resin 35 falls when valve 10 is opened, the space in the absorber being filled by a slug of regenerated resin 38 from an opentopped feed pot 29 after the remaining portion of resin 36 has settled, said feed pot preferably being furnished with vertical baffles 30 which cause the resin to move vertically downwards without any appreciable lateral movement. The slug of resin 35 is caused to move to regenerator 2 by means of a downward flow of water from pipe 11 and in doing so causes the slug 37 to rise in the regenerator tube. Regeneration of the slug 37 is carried out by means of regenerant fluid from distributor 15, the airflow being at pipe 25; after the resin has been backwashed and an opening valve 28, the upper slug of resin 37 is passed to the feed pot 29 by means of a flow of water from pipe 22.