#Reference [[Water Purification Processes]] ![[Screen Shot 2022-02-13 at 5.40.01 PM.jpg]] ## ISO 3696:1987 Grade 1 = Purest | Parameter | Grade 1 | Grade 2 | Grade 3 | | ------------------------------------------------------------------- | ------- | ------- | ------- | | pH value at 25°C | - | - | 5.0-7.0 | | Max conductivity at 25°C (μS/cm) | 0.1 | 1.0 | 5.0 | | Max oxygen content (mg/l) | - | 0.08 | 5.0 | | Max absorbance at 254nm, 1cm optical path length (absorbance units) | 0.001 | 0.01 | - | | Max residue after evaporation at 110°C (mg/kg) | - | 1 | 2 | | Max SiO2 content (mg/l) | 0.01 | 0.02 | - | ## ASTM D1193-06 Type 1 (Purest): requires 0.2 μm membrane filter Type 2: prepared by distillation Type 3: requires 0.45 μm membrane filter. | Parameter | Type I | Type II | Type III | Type IV | | -------------------------------- | ------ | ------- | -------- | -------- | | Max conductivity at 25°C (μS/cm) | 0.056 | 1.0 | 0.25 | 5.0 | | Max resistivity at 25°C (MΩ-cm) | 18.0 | 1.0 | 4.0 | 0.2 | | pH at 25°C | - | - | - | 5.0-8.0 | | Max TOC (μg/l) | 50 | 50 | 200 | No limit | | Max Sodium (μg/l) | 1 | 5 | 10 | 50 | | Max Silica (μg/l) | 3 | 3 | 500 | No limit | | Max Chloride (μg/l) | 1 | 5 | 10 | 50 | | | | | | |