BiC6H5O7 398.08 -- 813-93-4.
Bismuth Citrate contains not less than 49 percent and not more than 54 percent of bismuth (Bi).
Identification
A: Infrared Absorption 197K : on the undried specimen. B: When strongly heated, the salt chars, and on ignition leaves a more or less blackened residue having a yellow surface. The residue is soluble in warm nitric acid, and this solution, when dropped into a large excess of water, produces a white turbidity. C: Dissolve 1 g in ammonia. When treated with hydrogen sulfide in excess, a black precipitate is obtained. Filter this mixture, drive off the excess hydrogen sulfide by heating, and allow to cool. To a portion of this cooled solution add an excess of calcium hydroxide and boil: a white precipitate is formed. Reserve a second portion of the cooled solution for the test for Limit of nitrate. Arsenic: the limit is 10 microgm per g. Limit of nitrate: To the second portion of cooled solution reserved from Identification test C, add an equal volume of sulfuric acid, mix, and allow to cool. Into the liquid, drop a crystal of ferrous sulfate, and allow to stand for 30 minutes: no brown or brownish black color appears around the crystal. Limit of copper, lead, and silver: To pass the test; 10 microgm per g. Limit of soluble bismuth: To pass the test. Assay:Transfer about 300 mg of Bismuth Citrate, accurately weighed, to a porcelain crucible, and ignite. Allow to cool, add 2 mL of nitric acid to the residue, drop-wise, and warm until complete solution has been effected. Add about 60 mL of water and 0.3 mL of xylenol orange and titrate with 0.05 N edta disodium to a yellow endpoint. Each mL of 0.05 N edta disodium is equivalent to 10.45 mg of bismuth (Bi).
