C₆H₅NO₂    123.11
3-Pyridinecarboxylic acid.
Nicotinic acid   [59-67-6]

>> Niacin contains not less than 99.0 percent and not more than 101.0 percent of C₆H₅NO₂, calculated on the dried basis.

Packaging and storage -- Preserve in well-closed containers.
USP Reference standards (11) - USP Niacin RS.
Identification -
  A: Infrared Absorption (197M).
  B: Ultraviolet Absorption (197U) -
  Solution: 1 to 50,000.
  Medium: water.
  Ratio: A₂₃₇/A₂₆₂, between 0.35 and 0.39.

Loss on drying (731) - Dry it at 105° for 1 hour: it loses ot more than 1.0% of its weight.
Residue - on ignition (281): not more than 0.1%.
Chloride (221) - A 0.50-g portion shows no more chloride than corresponds to 0.15 mL of 0.020 N hydrochloric acid (0.02%).

Sulfate (221) - A 0.50-g portion shows no more sulfate than corresponds to 0.10mL of 0.020 N sulfuric acid (0.02%).

Heavy Metals, Method I (231) - Mix 1g with 4 mL of 1 N acetic acid, dilute with water to 25 mL, heat gently until solution is complete, and cool: the limit is 0.002%.

Ordinary impurities (466) -
  Test solution: water.
  Standard solution: water.
  Eluant: a mixture of methanol and 0.1 N hydrochloric acid (9:1).
  Visualization: 1.

Organic volatile impurities, Method IV (467): meets the requirements.
  Test preparation - Transfer 100 mg of Niacin to a vial, add 5 mL water, seal the vial, and heat to 80° for 60 minutes.
Assay - Transfer about 200 mg of Niacin, accurately weighed, to a 500 mL volumetric flask, add water to dissolve, dilute with water to volume, and mix. Concomitantly determine the absorbances of this solution and a solution of USP Niacin RS in teh same medum, at a concentration of about 20 µg per mL, in 1-cm cells at the wavelength of maximum absorbance at about 262 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in mg, of C₆H₅NO₂ in the Niacin taken by the formula: