Item | Standard I | Standard II | Standard III | Standard IV | Standard V |
Fe | 10 ppm max | 30 ppm max | 50 ppm max | 150 ppm max | 1500 ppm max |
Na2S | 60% min | 60% min | 60% min | 60% min | 60% min |
Water insolubles | 0.03% max | 0.18% max | 0.18% max | 0.30% max | 0.40% max |
Na2CO3 | 1.80% max | 1.80% max | 1.80% max | 3.00% max | 5.00% max |
Na2SO3 | 1.00% max | 1.80% max | 2.00% max | 2.00% max | 2.00% max |
Na2S2O3 | 2.00% max | 2.00% max | 2.00% max | 2.00% max | 2.00% max |
Colour | Yellow | Red |