The main retardion resins are a low affinity for non-electrolyte, coupled with an ability to selectively retard ionic substances. They can therefore be used not only for salting non-ionic solutions, but also for separating unwanted ions from ionic substances. In addition to retention of ions, retardion resins absorb acids and can be used for such purposes as removing excess acid following acid hydrolysis of proteins. The relative mobility of snake polymer chains provides the possibility of very close contact between oppositely charged groups on retardion resins and is a prime reason for the characteristics of these materials.