Separation of a bipyridylium salt from a solution containing it

摘要

Bipyridylium salts are separated from solutions thereof by contacting the solution with a cation exchange resin whereby the bipyridylium salt is preferentially absorbed on the cation-exchange resin. The absorbed salt may be recovered by, for example, elution with a dilute aqueous mineral acid and the solution of bipyridylium so obtained concentrated to give the solid salt. In the example N,N1-dimethyl-4,41 -bipyridylium dichloride is separated from a solution thereof in water with methyl pyridinium chloride by elution with hydrochloric acid of the cation-exchange resin charged with said solution.