| Sulphated Ash Or Residue On Ignition Analysis |
| 1.0 PROCEDURE 1.1 Apparatus : Silica crucible tongue thermostatic gloves 1.2 Reagent : Sulphuric acid 1.3 Method : 1.3.1 Ignite a suitable crucible (for example, silica, platinum, porcelain or quartz) at 600 ± 50 °C for 30 min, allow to cool in a desiccators over silica gel or other suitable desiccant and weigh (W1). 1.3.2 Place the crucible on the weighing balance pan and tare it and take the prescribed amount of the substance to be examined in the crucible and take the final weigh of the sample (W2). 1.3.3 Moisten the substance to be examined with a small amount of sulphuric acid (usually 1 ml) and heat gently at as low a temperature as practicable until the sample is thoroughly charred. 1.3.4 After cooling, moisten the residue with a small amount of sulphuric acid (usually 1 ml), heat gently until white fumes are no longer evolved and ignite at 600 ± 50°C until the residue is completely incinerated. 1.3.5 Ensure that flames are not produced at any time during the procedure. Allow the crucible to cool in a desiccator over silica gel or other suitable desiccant and weigh. 1.3.6 If the amounts of the residue so obtained exceeds the prescribed limit, repeat the moistening with sulphuric acid and ignition, as previously, for 30 min periods until 2 consecutive weighing’s do not differ by more than 0.50 mg. and take the final weigh (W3) and calculate the percentage of residue with the help of the given formula. 1.3.7 To measure of sulphated ash by The amounts of substance used for the test (usually 1 to 2 gm) is chosen so that, at the prescribed limit the mass of the residue (usually about 1 mg) can be measure with sufficient accuracy. % Sulphated ash = W3-W1 x 100 / W2Where, W1 = weight of the empty crucible. W2 = weight of the sample taken. W3 = weight of the crucible with residue. |