An anion desilicizer is a "poor mans" demineralizer consisting of a strong cation exchanger in the sodium form (a water softener) followed by a strong base anion exchanger in the hydroxide form. Thank goodness there are not too many of these critters around anymore. They have most of the
disadvantages of a demineralizer and few of the advantages. However, they do remove silica along
with the other anions.