SULPHATED ASH

1. PROCEDURE:  
2. Ignite the silica, platinum, porcelain or quartz crucible at 600°C ± 50°C for about
3. 30 minutes. Allow to cool in a desiccator for about 30mins (Silica gel or other suitable
4.  desiccant) and weigh (W₁ g).        
5. Transfer accurately about 1 to 2 g of the sample or the amount specified in the
6. individual Standard testing procedure into the crucible. Take the weight accurately (W₂ g). 
7. (3) Moisten the substance with a small amount (usually 1mL) of sulphuric acid and heat   
8. gently at low temperature as practical until the sample is thoroughly charred.  
9. Cool and moisten the residue with a small amount (usually 1mL) of sulphuric acid.          
10. (4)Heat gently until white fumes no longer are evolved, and ignite at 600 ± 50 °C, in a muffle furnace unless temperature is specified in the individual monograph, until the carbon is consumed. Ensure that the flames are not produced at any time during the analysis.                                                                                                                                                                                                                                                       
11. (5)Cool in a desiccator for about 30 minutes (Silica gel or other suitable desiccant), weigh
12. accurately (W₃ g), and calculate the percentage of residue.      
14.                                                                (W₃ – W₁)                                                                     
15.                  % of Sulphated ash   =   ------------------------ x 100                                     
16.                                                                (W₂ - W₁)       
17.  
18. (6)     If the amount of residue so obtained exceeds the limit specified in the individual 
19. specification, again moisten the residue with 1mL of sulfuric acid, heat and ignite as before for 30minutes until constant weight is attained or until the percentage of residue complies   with the limit in the individual monograph.                                            
20. (7)Continue the ignition until constant weight (two consecutive weighings do not differ by more than 0.50mg per g of substance taken) is attained, unless otherwise specified in the individual monograph.
21. Note:
22. (1)Conduct the ignition in a well-ventilated hood, but protected from air currents and at  
23. as low a temperature as is possible to effect the complete combustion of the carbon.
24. (2)A muffle furnace may be used, if desired, and its use is recommended for the final ignition at 600 ± 50°C

General testing procedure, sulphated ash, carbon, platinum,