FI-Photometric Determination of Dissolved Silica in Geothermal Water

A flow injection analytical installation was fabricated for the photometric determination of silicate based on its reaction with ammonium molybdate and applied to the determination of dissolved silica in geothermal water. Various working parameters of the instrument including concentration of ammonium molybdate solution and acidity for the color reaction, lengths of reaction coils, definite volume of reagent ring, flow-rate at the out-let of the system and etc. were tested and optimized. Sampling frequency of 60 samples per hour was attained by this method. Range of linearity for SiO2 was found between 20-800 mg·L-1. In the analysis of substantial samples by the present method, results of SiO2 contents found were in consistency with the results found by the standard method of GB/T 12148-2006.