RESIDUE ON IGNITION & SULFATED ASH

 The Residue on Ignition / Sulfated Ash test utilizes a procedure to measure the amount of residual substance not volatilized from a sample when the sample is ignited in the presence of sulfuric acid according to the procedure described below. This test is usually used for determining the content of inorganic impurities in an organic substance.

The tests Residue on ignition & Sulfated ash both are same.

Procedure: Weigh accurately 1 to 2 g of the substance, or the amount specified in the individual monograph, in a suitable crucible (silica, platinum, quartz, or porcelain) that previously has been ignited at 600 ± 50 for 30 minutes, cooled in a desiccator (silica gel or other suitable desiccant), and weighed. Moisten the sample with a small amount (usually 1 mL) of sulfuric acid. Heat, gently at first, at a temperature as low as practicable until the substance is thoroughly charred, cool, then, unless otherwise directed in the individual monograph, moisten the residue with a small amount (usually 1 mL) of sulfuric acid, heat gently until white fumes are no longer evolved, and ignite at 600 ± 50 , unless another temperature is specified in the individual monograph, until the carbon is consumed. Ensure that flames are not produced at any time during the procedure. Cool in a desiccator (silica gel or other suitable desiccant), weigh, and calculate the percentage of residue. Unless otherwise specified, if the amount of the residue so obtained exceeds the limit specified in the individual monograph, repeat the moistening with sulfuric acid, heating and ignition as before, until constant weight is attained or until the percentage of residue complies with the limit in the individual monograph.