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7.6 ACID-INSOLUBLE ASH

          Use Method I unless otherwise indicated in the monograph.

Method I

          Boil the total ash for 5 minutes with 25 mL of dilute hydrochloric acid, collect the insoluble matter on an ashless filter paper,wash with hot water until the filtrate is neutral, and ignite at about 500°. Calculate the percentage of acid-insoluble ash with reference to the air-dried substance.

Method II

          Place the total ash or the sulfated ash, as directed in the monograph, in a crucible, add 15 mL of water and 10 mL of hydrochloric acid, cover with a watch glass, and boil for 10 minutes; allow to cool. Collect the insoluble matter on an ashless filter paper, wash with hot water until the filtrate is neutral is neutral, ignite to dull redness (550° to 700°), cool in a desiccator and weigh. Reheat until the difference between two successive weighings is not more than 1 mg. Calculate the percentage of acid-insoluble ash with reference to the airdried substance.

APPENDICES • 7.6 ACID-INSOLUBLE ASH
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หมายเหตุ / Note : THP 2021 Page 926