Dissolve about 450 mg of the sample, accurately weighed, in 25 ml of
water, add 5 ml of ammonia/ammonium chloride buffer TS and 0.1 ml of
eriochrome black TS and titrate with 0.05 M disodium
ethylenediaminetetraacetate until the solution is blue in colour. Each ml of
0.05 M disodium ethylenediaminetetra-acetate is equivalent to 10.16 mg of
MgCl2 · 6H2O.