Optimization of Oxalic Acid Volume in Total Silica Analysis by Molybdosilicate Method

Abstract

Oxalic acid is used to remove iron and phosphate interferences in the molybdosilicate method of total silica analysis. Optimization of the volume of oxalic acid to be used for geothermal samples has been studied to standardize the procedure at different PNOC-EDC laboratories. Based on the experiments conducted using 15% (w/v) oxalic acid, the optimum volume is 1 ml for a total sample volume of 100 ml. With this amount, the results show better linearity, accuracy and reproducibility. It also improves the laboratory procedure by reducing the bleaching effect caused by the breakdown of the yellow silicomolybdate complex by oxalates, especially in samples with negligible interference. Compared to using greater volumes of oxalic acid, the probability for this reaction to occur is minimized. Thus, more timing allowance is created.