Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Astringent.
DEFINITION
Mixture of esters of glucose with gallic acid and 3-galloylgallic acid.
CHARACTERS
Appearance
Yellowish-white or slightly brown amorphous light powder or shiny plates.
Solubility
Very soluble in water, freely soluble in acetone, in ethanol (96 per cent) and in glycerol (85 per cent), practically insoluble in methylene chloride.
IDENTIFICATION
A. Dilute 0.1 mL of solution S (see Tests) to 5 mL with water R. Add 0.1 mL of ferric chloride solution R1. A blackish-blue colour is produced which becomes green on the addition of 1 mL of dilute sulfuric acid R.
B. To 1 mL of solution S, add 3 mL of a 1 g/L solution of gelatin R. The mixture becomes turbid and a flocculent precipitate is formed.
C. Dilute 0.1 mL of solution S to 5 mL with water R. Add 0.3 mL of barium hydroxide solution R. A greenish-blue precipitate is formed.
TESTS
Solution S
Dissolve 4.0 g in carbon dioxide-free water R and dilute to 20 mL with the same solvent.
Appearance of solution
Solution S is not more opalescent than reference suspension II (2.2.1).
Dextrins, gum, salts, sugars
To 2 mL of solution S, add 2 mL of ethanol (96 per cent) R. The solution is clear. Add 1 mL of ether R. The solution remains clear for at least 10 min.
Resins
To 5 mL of solution S, add 5 mL of water R. The mixture remains clear (2.2.1) for at least 15 min.
Loss on drying (2.2.32)
Maximum 12.0 per cent, determined on 0.200 g by drying at 105 °C.
Sulfated ash (2.4.14)
Maximum 0.1 per cent, determined on 1.0 g.
STORAGE
Protected from light.
