Weigh and finely powder not less than 20 tablets. Weigh accurately a portion of the powder, equivalent to about 800 mg of magnesium gluconate, transfer to a suitable crucible, and ignite, gently at first, until free from carbon. Cool the crucible, add 25 ml of water and 5 ml of hydrochloric acid, and stir. Heat on a steam bath for 5 minutes, and filter, rinsing the filter wiht several portions of water. Dilute the combined filtrate and washings wiht water to about 150 ml. Add ammonai-ammonium chloride buffer TS untip the solution is neutral to litmus. Add 5 ml of ammonia-ammonium chloride buffer TS and 0.1 ml of eriochrom black TS, and titrate wiht 0.05 M disodium ethylenediaminetetraacetate VS to a blue endpoint. Each ml of 0.05 M disodium ethylenediaminetetraacetate is equivalent to 20.73 mg of C12H22MgO14