Abstract：A determination method of silicon dioxide in siliceous refractory materials by potassium fluosilicate precipitation-acid base titration method was established. Neither a platinum crucible nor the volatilization of silicon by hydrofluoric acid was needed. The determination accuracy and precision were investigated. The interference factors and possible interference mechanism were discussed. The samples were melted in a silver or nickel crucible with sodium hydroxide, during which the silicon dioxide in sample was converted into sodium silicate. Then, potassium fluoride solution was added into strong acid solution containing excessive potassium chloride to form potassium fluosilicate precipitation. After filtration and washing, the precipitates were dissolved in boiling water. The generated hydrofluoric acid through hydrolysis was titrated with standard sodium hydroxide solution using phenolphthalein as indicator. It was generally considered that, when the ratio between mass fraction of silicon dioxide and aluminum oxide in sample was higher or equal to 3.5, the aluminum oxide had no influence on the determination. This method has been applied to the determination of silicon dioxide in siliceous refractory materials such as siliceous sandstone and silica brick. The measurement results were consistent with the certified values. Moreover, the repeatability was very good.
