Leonard Shapiro 1974 <p> Solutions containing in excess of 200<i>μ</i>g/ml of silica form polymers which do not react with molybdate in the spectrophotometric determination of silica. Fluoride ions catalyze the depolymerization of silica so that precise spectrophotometric determinations of silica can be made, even when silica is present predominantly as polymers.</p> application/pdf en U.S. Geological Survey Spectrophotometric determination of silica at high concentrations using fluoride as a depolymerizer article