Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Antidiarrhoeal.
DEFINITION
Activated Attapulgite is a purified native hydrated magnesium aluminium silicate essentially consisting of the clay mineral palygorskite that has been carefully heated to increase its adsorptive capacity.
CHARACTERISTICS
A light, cream or buff, very fine powder, free or almost free from gritty particles.
IDENTIFICATION
A. Ignite 0.5 g with 2 g of anhydrous sodium carbonate for 20 minutes, cool and extract with 25 mL of boiling water. Cool, filter, wash the residue with water and add the washings to the filtrate. Reserve the residue for test
B. Cautiously acidify the combined filtrate and washings with hydrochloric acid, evaporate to dryness, moisten the residue with 0.2 mL of hydrochloric acid, add 10 mL of water and stir. A white, gelatinous precipitate is produced.
B. Wash the residue reserved in test A with water and dissolve in 10 mL of 2M hydrochloric acid. To 2 mL of the solution add a 10% w/v solution of ammonium thiocyanate. An intense red colour is produced.
C. To 2 mL of the solution obtained in test B add 1 mL of strong sodium hydroxide solution and filter. To the filtrate add 3 mL of ammonium chloride solution. A gelatinous white precipitate is produced.
D. To 2 mL of the solution obtained in test B add ammonium chloride and an excess of 13.5M ammonia and filter. To the filtrate add 0.15 mL of magneson reagent and an excess of 5M sodium hydroxide. A blue precipitate is produced.
TESTS
Acidity or alkalinity
pH of a 5% w/v suspension in carbon dioxide-free water, after shaking for 5 minutes, 7.0 to 9.5, Appendix V L.
Arsenic
To 0.13 g add 5 mL of water, 2 mL of sulfuric acid and 10 mL of sulfur dioxide solution and evaporate on a water bath until the sulfur dioxide solution is removed and the volume reduced to about 2 mL. Transfer the solution to the generator flask with the aid of 5 mL of water. The resulting solution complies with the limit test for arsenic, Appendix VII (8 ppm).
Acid-soluble matter
Boil 2 g with 100 mL of 0.2M hydrochloric acid under a reflux condenser for 5 minutes, cool and filter. Evaporate 50 mL of the filtrate to dryness. The residue, after ignition at about 600° for 30 minutes, weighs not more than 0.25 g.
Water-soluble matter
Boil 10 g with 100 mL of water under a reflux condenser for 5 minutes, cool and filter. Evaporate 50 mL of the filtrate to dryness. The residue, after ignition at 600° for 30 minutes, weighs not more than 50 mg.
Adsorptive capacity
In a stoppered bottle shake 1.0 g, in very fine powder, with 50 mL of a 0.12% w/v solution of methylene blue for 5 minutes, allow to settle and centrifuge. The colour of the clear supernatant solution is not more intense than that of a 0.0012% w/v solution of methylene blue.
Loss on drying
When dried to constant weight at 105°, loses not more than 4.0% of its weight. Use 1 g.
Loss on ignition
When ignited at 600°, loses not more than 9.0% of its weight. Use 1 g.
