Hydrotalcite Tablets

Action and use

Antacid.

Definition

Hydrotalcite Tablets contain Hydrotalcite.

Content of hydrotalcite, Al₂Mg₆(OH)₁₆CO₃,4H₂O

90.0 to 110.0% of the stated amount.

Identification

Add 20 mL of 2m hydrochloric acid to a quantity of the powdered tablets containing 1.0 g of Hydrotalcite, shake and filter. Add 30 mL of water to the filtrate and boil. Add 2m ammonia until just alkaline to methyl red, continue boiling for 2 minutes and filter. Wash the precipitate with 50 mL of a hot 2% w/v solution of ammonium chloride and dissolve in 15 mL of 2m hydrochloric acid. The resulting solution yields the reaction characteristic of aluminium salts, Appendix VI.

Neutralising capacity

Weigh and powder 20 tablets, pass the powder as completely as possible through a sieve of nominal mesh aperture about 225 µm and remix the sifted powder. Mix a quantity equivalent to one tablet with a small quantity of water, added slowly with stirring, to give a smooth paste and add gradually sufficient further quantities of water to produce 100 mL. Warm to 37°, add 100 mL of 0.1m hydrochloric acid VS previously heated to 37° and stir continuously using a paddle stirrer at a rate of about 200 revolutions per minute, maintaining the temperature at 37°. The pH of the solution at 37°, after 10 minutes and after 20 minutes, is 3.0 to 4.2, Appendix V L. Add 12 mL of 0.5m hydrochloric acid VS at 37°, stir continuously for 1 hour, maintaining the temperature at 37°, and titrate with 0.1m sodium hydroxide VS to pH 3.5. Subtract the number of mL of 0.1m sodium hydroxide VS from 160 mL to obtain the number of mL of 0.1m hydrochloric acid VS required for neutralisation. Not less than 130 mL of 0.1m hydrochloric acid VS is required to neutralise one tablet.

Assay

Weigh and powder 20 tablets. To a quantity of the powder containing 0.3 g of Hydrotalcite add 2 mL of 7m hydrochloric acid and heat on a water bath for 15 minutes. Allow to cool, add 250 mL of water and 50 mL of 0.05m disodium edetate VS and neutralise with 1m sodium hydroxide using methyl red solution as indicator. Heat the solution on a water bath for 30 minutes and allow to cool. Add 3 g of hexamine and titrate the excess of disodium edetate with 0.05m lead nitrate VS using xylenol orange solution as indicator. Each mL of 0.05m disodium edetate VS is equivalent to 15.09 mg of Al₂Mg₆(OH)₁₆CO₃,4H₂O.