(kal' see um kar' bo nate).
Carbonic acid, calcium salt (1:1);
Calcium carbonate (1:1) [471-34-1].
Calcium Carbonate, dried at 200 for 4 h, contains calcium equivalent to NLT 98.0% and NMT 100.5% of calcium carbonate (CaCO3).
• A. Identification TestsGeneral, Calcium 191: The addition of acetic acid to it produces effervescence (presence of carbonate), and the resulting solution, after boiling, meets the requirements of the tests.
• Titrimetry 541
Sample: 200 mg of Calcium Carbonate, previously dried at 200 for 4 h
Blank: 100 mL of water and 15 mL of 1 N sodium hydroxide
(See Titrimetry 541.)
Mode: Direct titration
Titrant: 0.05 M edetate disodium VS
Indicator: 300 mg of hydroxy naphthol blue
Endpoint detection: Visual, change to distinct blue
Analysis: Transfer the Sample to a 250-mL beaker. Moisten thoroughly with a few mL of water, and add, dropwise, sufficient 3 N hydrochloric acid to dissolve. Add 100 mL of water, 15 mL of 1 N sodium hydroxide, and 300 mg of hydroxy naphthol blue. Titrate with the Titrant. Calculate the percentage of calcium carbonate (CaCO3) in the Sample taken:
Result = [(V B) × M × F × 100]/W
Acceptance criteria: 98.0%100.5% on the dried basis
• Acid-Insoluble Substances
Sample: 5.0 g
Analysis: Mix the Sample with 10 mL of water, and add hydrochloric acid, dropwise, with agitation, until it ceases to cause effervescence, then add water to make the mixture measure 200 mL, and filter. Wash the insoluble residue with water until the last washing shows no chloride, and ignite and weigh the residue.
Acceptance criteria: NMT 0.2%; the weight of the residue does not exceed 10 mg.
• Barium: A platinum wire, dipped in the filtrate obtained in the test for Acid-Insoluble Substances and held in a nonluminous flame, does not impart a green color.
• Heavy Metals 231
Test preparation: Mix 1.0 g with 5 mL of water, slowly add 8 mL of 3 N hydrochloric acid, and evaporate on a steam bath to dryness. Dissolve the residue in 20 mL of water, filter, and add water to the filtrate to make 25 mL.
Acceptance criteria: NMT 20 ppm
• Iron 241
Sample solution: 40 mg in 5 mL of 2 N hydrochloric acid. Transfer to a beaker with the aid of water, and dilute with water to 10 mL.
Standard solution: Transfer 4.0 mL of the Standard Iron Solution, prepared as directed in Iron 241, to a beaker, and dilute with water to 10 mL.
Analytical wavelength: 530 nm
Analysis: Separately to the Sample solution and Standard solution add 2 mL of citric acid solution (1 in 5) and 2 drops of thioglycolic acid, adjust with ammonia TS to a pH of 9.5 ± 0.1, dilute with water to 20 mL, and allow to stand for 5 min. Dilute with water to 50 mL. Concomitantly determine the absorbances of the solutions from the Sample solution and the Standard solution.
Acceptance criteria: NMT 0.1%; the absorbance of the solution from the Sample solution does not exceed that of the Standard solution.
• Lead 251
Sample solution: 1.0 g in 5 mL of water
Analysis: To the Sample solution slowly add 8 mL of 3 N hydrochloric acid, evaporate on a steam bath to dryness, and dissolve the residue in 5 mL of water.
Acceptance criteria: NMT 3 ppm
• Limit of Fluoride
[NotePrepare and store all solutions in plastic containers. ]
Solution A: 294 mg/mL of sodium citrate dihydrate in water
Sample: 2.0 g
Standard stock solution: 1.11 mg/mL of USP Sodium Fluoride RS in water
Standard solution: Combine 20.0 mL of the Standard stock solution with 50.0 mL of Solution A, and dilute with water to 100.0 mL. [NoteEach mL of this solution contains 100 µg of fluoride ion ]
Electrode system: Use a fluoride-specific ion-indicating electrode and a silversilver chloride reference electrode connected to a pH meter capable of measuring potentials with a minimum reproducibility of ±0.2 mV (see pH 791).
Standard response line: Transfer 50.0 mL of Solution A and 4.0 mL of hydrochloric acid to a beaker, and add water to make 100 mL. Add a plastic-coated stirring bar, insert the electrodes into the solution, stir for 15 min, and read the potential, in mV. Continue stirring, and at 5-min intervals add 100, 100, 300, and 500 µL of the Standard solution, reading the potential 5 min after each addition. Plot the logarithms of the cumulative fluoride ion concentrations (0.1, 0.2, 0.5, and 1.0 µg/mL) versus potential, in mV.
Analysis: Transfer the Sample to a beaker containing a plastic-coated stirring bar, add 20 mL of water and 4.0 mL of hydrochloric acid, and stir until dissolved. Add 50.0 mL of Solution A and sufficient water to make 100 mL of test solution. Rinse and dry the electrodes, insert them into the Sample solution, stir for 5 min, and read the potential, in mV. From the measured potential and the Standard response line, determine the concentration, C, in µg/mL, of fluoride ion in the Sample solution. Calculate the content of fluoride in the specimen taken:
Result = (V × C)/W
Acceptance criteria: 50 ppm
• Limit of Magnesium and Alkali Salts
Sample solution: 1.0 g
Analysis: Mix the Sample with 35 mL of water. Carefully add 3 mL of hydrochloric acid, heat the solution, and boil for 1 min. Rapidly add 40 mL of oxalic acid TS, and stir vigorously until precipitation is well-established. Add immediately to the warm mixture 2 drops of methyl red TS and then 6 N ammonium hydroxide, dropwise, until the mixture is just alkaline. Cool to room temperature, transfer to a 100-mL graduated cylinder, dilute with water to 100 mL, mix, and allow to stand for 4 h or overnight. Filter, and to 50 mL of the clear filtrate in a platinum dish add 0.5 mL of sulfuric acid, and evaporate the mixture on a steam bath to a small volume. Carefully heat over a free flame to dryness, and continue heating to complete decomposition and volatilization of ammonium salts. Finally, ignite the residue to constant weight.
Acceptance criteria: NMT 1.0%; the weight of the residue is NMT 5 mg.
• Mercury, Method IIa 261
Mercury stock solution and Standard mercury solution: Proceed as directed in Mercury 261.
Standard solution: Proceed as directed in Mercury 261, except use 3 mL of hydrochloric acid instead of 3 mL of sulfuric acid.
Sample stock solution: 4.0 g in a 100-mL beaker, and cautiously dissolve in 14 mL of 6 N hydrochloric acid
Sample solution: Proceed as directed in Mercury 261 using the Sample stock solution, except use 3 mL of hydrochloric acid instead of 3 mL of sulfuric acid.
Samples: Standard solution and Sample solution
Proceed as directed in Mercury 261.
Acceptance criteria: 0.5 ppm
• Loss on Drying 731: Dry a sample at 200 for 4 h: it loses NMT 2.0% of its weight.
• Packaging and Storage: Preserve in well-closed containers.
• USP Reference Standards 11
USP Sodium Fluoride RS
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 2442Pharmacopeial Forum: Volume No. 27(6) Page 3255