Dissolve about 0.400 g of the dried sample in a mixture of 100 ml of carbon
dioxide-free water and 25 ml of dilute sulphuric acid TS. Titrate the solution
at once with 0.1 N iodine, adding a few drops of starch TS as indicator as
the end-point is approached. Each ml of 0.1 N iodine is equivalent to 9.905
mg of C6H7O6Na.