Barium, complex with polysaccharides

Alkali-earth metals (calcium, barium, and magnesium) complex with polysaccharides extensively (Reisenhofer et al., 1984). Calcium has a smaller atomic and ionic radius than does sodium and, because it has two valence electrons, it is endowed with greater polarizing and bonding ability than Na+. Ca and Ca2+ easily form insoluble complexes with oxygenated compounds. Polysaccharide salts of alkali-earth metals are generally insoluble. 

Whereas all of the methods proposed for large-scale fractionation of starch that have been discussed depend directly on the ability of amylose to form itLsoluble complexes with polar organic compounds. Cantor and Wimmer s process is based on a totally different principle. If a molecularly disperse solution of starch contains a sufficient amount of calcium chloride and caustic alkali is added, a rapid and quantitative precipitation of the starch occurs, because of the formation of complexes (of calcium hydroxide with the starch polysaccharides) which are insoluble in an aqueous, saturated solution of calcium hydroxide. The same phenomenon is observed with the hydroxides of barium and strontium. 

---