Standard solution—
Dissolve an accurately weighed quantity of
USP Dextrose RS in water, and dilute quantitatively with water to obtain a solution having a known concentration of about 10 mg per mL.
Procedure—
Transfer 25.0-mL portions of
alkaline cupric tartrate TS to each of two boiling flasks. Bring the contents of one of the flasks to boiling, and titrate with
Standard solution to within 0.5 mL of the anticipated endpoint. Again heat the flask, with swirling, boil moderately for 2 minutes, add 2 drops of methylene blue solution (1 in 100), immediately add about 2 drops of the
Standard solution from the buret, and again bring to a boil. Allow the cuprous oxide to settle slightly, and observe the color of the supernatant. Complete the titration within 3 minutes by adding
Standard solution dropwise, and boiling after each addition, to the disappearance of the blue color, determined by viewing against a white background in daylight or under equivalent illumination. If more than 0.5 mL of the titrant was required after the addition of the indicator, repeat the titration, adding the necessary volume of titrant before adding the indicator. Bring the contents of the second flask to boiling, and similarly titrate with
Test solution. Calculate the
Dextrose equivalent, on the dried basis, taken by the formula:
[100 / (1
0.01
A)](
CS /
CU)(
VS /
VU),
in which
A is the percentage
Loss on drying of the Dextrates taken;
CU is the concentration, in mg per mL, of Dextrates in the
Test solution;
CS is the concentration, in mg per mL, of
USP Dextrose RS in the
Standard solution, and
VU and
VS are the titrated volumes, in mL, of the
Test solution and the
Standard solution, respectively.
791
:
between 3.8 and 5.8, determined in a 1 in 5 solution in carbon dioxide-free water.
for 16 hours in a convection oven: the anhydrous form loses not more than 2.0% of its weight; the hydrated form loses between 7.8% and 9.2% of its weight.