Completeness of solution—
Place 5 Tablets in a 250-mL beaker containing 150 mL of water at 25
. Stir for 5 minutes: all of the Tablets dissolve to give a clear or practically clear solution.
Identification—
A:
Dissolve a quantity of Tablets, equivalent to about 1 g of saccharin, in 10 mL of water, filter if necessary, and to the solution add 5 mL of 3 N hydrochloric acid: a white precipitate of saccharin is formed. Collect the precipitate on a filter, wash with small portions of cold water until the last washing is practically free from chloride, and dry it at 105
for 2 hours: the saccharin so obtained melts between 226
and 230
, the procedure for
Class I being used (see
Melting Range or Temperature 
741
).
[NOTE—Use also in Identification tests B and C.]
B:
Dissolve about 100 mg in 5 mL of sodium hydroxide solution (1 in 20), evaporate to dryness, and gently fuse the residue over a small flame until it no longer evolves ammonia. Allow the residue to cool, dissolve in 20 mL of water, neutralize with 3 N hydrochloric acid, and filter: the addition of a drop of
ferric chloride TS to the filtrate produces a violet color.
C:
Mix 20 mg with 40 mg of resorcinol, add 10 drops of sulfuric acid, and heat the mixture in a suitable liquid bath of 200
for 3 minutes. Allow it to cool, and add 10 mL of water and an excess of 1 N sodium hydroxide: a fluorescent green liquid results.
Assay—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of saccharin, to a 100-mL volumetric flask, add about 50 mL of water, agitate until the tablet material is dissolved or evenly dispersed, dilute with water to volume, and mix. Transfer 10.0 mL to a separator, add 2 mL of 3 N hydrochloric acid, and extract with five 20-mL portions of a solvent composed of chloroform and alcohol (9:1). Collect the combined extracts in a beaker, and evaporate on a steam bath to dryness with the aid of a current of air. Dissolve the residue in 10 mL of sodium hydroxide solution (1 in 250), transfer the solution with the aid of water to a 200-mL volumetric flask, dilute with water to volume, and mix. Concomitantly determine the absorbances of this solution and a Standard solution of
USP Saccharin RS in the same medium having a known concentration of about 50 µg per mL, in 1-cm cells at the wavelength of maximum absorbance at about 269 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in mg, of saccharin (C
7H
5NO
3S) in the portion of Tablets taken by the formula:
(2C)(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Saccharin RS in the Standard solution; and
AU and
AS are the absorbances of the solution from the Tablets and the Standard solution, respectively.
