loses all or most of its activity during hydrogenation in order to maintain a given level of catalytic activity with the catalytic mass it is necessary for the catalyst in the reaction medium to be gradually replaced this replacement is effected by feeding fresh catalyst to the reaction vessel and removing a quantity of reaction medium which contains an amount of catalyst equal to that supplied the fed catalyst may consist of a mixture of fresh catalyst and of recycled catalyst recycled catalyst is catalyst that has been washed prior to re use 1 a quantity of catalyst in excess of 1 part by weight per 100 parts of liquid reaction medium hexamethylenediamine water and sodium hydroxide the upper limit depending solely on the fluidity of the reaction medium the preferred range is from 3 to 35 parts per 100 parts by weight of the liquid reaction medium 2 a quantity of sodium hydroxide in the range of 0 2 to 12 moles per kilogram of catalyst and preferably between 1 and 3 moles per kilogram of catalyst 3 a quantity of water in the range of 2 to 130 moles per mole of sodium hydroxide and preferably between 7 and 70 moles per mole of sodium hydroxide substantially similar results in the production of the amine can be obtained by using instead of sodium hydroxide a hydroxide of any other of the alkali metals throughout the following description however reference will be made to the preferred sodium hydroxide the liquid part of the reaction medium under the starting conditions already specified and within the preferred range of ratio of water to sodium hydroxide consists of two phases one phase amounting to 0 5 5 0 parts per 100 parts of the other phase.