When sourcing Phosphoric Acid, the concentration (typically 75%, 85%, or 95%) and purity grade are the most critical factors. For the food industry, you must ensure it meets Food Grade (FCC) standards with strict limits on heavy metals like Arsenic (<3ppm) and Fluorine (<10ppm). For industrial uses like metal treatment or fertilizer production, Technical Grade is sufficient, but you should still verify the Iron (Fe) and Sulfate (SO4) content to prevent unwanted chemical reactions in your processes.