The observation that commercial fluosilicic acids dissolved silicic acid, up to about 30g/litre, led initially to the presumption that some hydrofluoric acid was present in them. Analysis by published acidimetric methods indicated the absence of hydrofluoric acid and failed to distinguish between the silica-enriched acid and the original acid. Equilibrium studies indicated the modifications required in the acidimetric method to permit its use in characterizing the silica-enriched fluosilicic acids. The modified method functions equally well for the low-silica fluosilicic acids (mixtures of hydrofluoric and fluosilicic acids). Any homogenous liquid reaction product in the system water-silica-hydrogen fluoride may, therefore, be characterized by this method. Accuracy is within 1% in moderately high concentrations.
