Purification of d,d'-2,2'(ethylenediimino)di-1-butanol dihydrochloride

In a process for preparing d,d'-2,2'-(ethylenediimino)di-1-butanol dihydrochloride comprising the steps of

• reacting excess d-2-amino-1-butanol with ethylene dichloride,
• adding to the reaction mixture thus formed sufficient finely divided sodium hydroxide to neutralize hydrogen chloride formed therein,
• distilling off unreacted d-2-amino-1-butanol, adding sufficient of a 2 to 4 carbon alkanol to the residue to dissolve the thus formed d,d'-2,2'-(ethylenediimino)di-1-butanol, separating sodium chloride therefrom,
• adding hydrogen chloride to the resulting solution to form d,d'-2,2'-(ethylenediimino)di-1-butanol dihydrochloride, and separating the same from said alkanol, the improvement which comprises:
• reacting a 2 carbon alkanol solution of d,d'-2,2'-(ethylenediimino)di-1-butanol with an essentially stoichiometric amount of hydrogen chloride at 40.degree.-60.degree.C. in the presence of about 7% to 10% by weight water, based on the total weight of the reaction mixture to form d,d'-2,2'-(ethylenediimino)di-1-butanol dihydrochloride,
• slowly cooling the resulting aqueous alkanol solution to 0 to -10.degree.C. to precipitate said dihydrochloride,
• separating said dihydrochloride from said aqueous alkanol solution,
• washing said dihydrochloride with a 2 to 4 carbon alkanol, and drying the same.