Zinc Carbonate
3Zn(OH)2·2ZnCO3 549.01
Basic zinc carbonate;
Zinc subcarbonate
[3486-35-9].
(zink kar' bo nate).
3Zn(OH)2·2ZnCO3 549.01
Basic zinc carbonate;
Zinc subcarbonate
[3486-35-9].DEFINITION
Zinc Carbonate contains the equivalent of NLT 70.0% of ZnO.
IDENTIFICATION
• A. Identification Tests—General, Zinc 
191
191
Sample solution:
Dissolve in a slight excess of hydrochloric acid.
Acceptance criteria:
Meets the requirements
ASSAY
• Procedure
Analysis:
Transfer 2.0 g to a 125-mL conical flask, add 50.0 mL of 1 N sulfuric acid VS, and swirl to dissolve. Add 3 drops of methyl orange TS, and titrate with 1 N sodium hydroxide VS to a yellow endpoint. Each mL of 1 N sulfuric acid is equivalent to 40.69 mg of ZnO.
Acceptance criteria:
NLT 70.0%
IMPURITIES
• Chloride and Sulfate, Chloride 221
221
Sample solution:
Dissolve 1.0 g in a mixture of 20 mL of water and 3 mL of nitric acid.
Acceptance criteria:
The Sample solution shows no more chloride than corresponds to 0.03 mL of 0.02 N hydrochloric acid (0.002%).
• Sulfate
Sample solution:
Dissolve 10.0 g in a mixture of 75 mL of water and 10 mL of hydrochloric acid, and filter. Neutralize the filtrate with ammonium hydroxide, and dilute with water to 100 mL.
Analysis:
To 10.0 mL of the Sample solution add 1 mL of 0.6 N hydrochloric acid and 1 mL of barium chloride TS, and allow to stand for 10 min.
Acceptance criteria:
The Sample solution shows no more turbidity than that produced in a solution containing 0.10 mL of 0.02 N sulfuric acid and the same quantities of reagents used to prepare the Sample solution (0.01%).
• Iron 241
241
Sample solution:
Dissolve 1.0 g in 20 mL of water and 3 mL of hydrochloric acid.
Acceptance criteria:
NMT 0.002%
• Lead
Standard lead solution:
Prepare as directed in the test for Heavy Metals 231.
231.
Sample solution:
Transfer 10.0 g to a 100-mL volumetric flask, add 20 mL of nitric acid and 10 mL of water, swirl to dissolve, and dilute with water to volume.
Blank:
Nitric acid in water (1 in 25)
Instrumental conditions
Mode:
Atomic absorption spectrophotometry
Analytical wavelength:
217.0 nm (lead emission line)
Lamp:
Lead hollow-cathode
Flame:
Air–acetylene
Analysis:
Add 10.0 mL of Sample solution to each of three 25-mL volumetric flasks. To the respective volumetric flasks add 0, 5.0, and 10.0 mL of Standard lead solution, and dilute with water to volume. These solutions contain 0, 0.002, and 0.004 mg/mL of added lead, respectively. Determine the absorbances of these three solutions. Plot the absorbances of the three solutions versus their contents of added lead, in mg/mL, as furnished by the Standard lead solution. Draw a straight line (calibration curve) best fitting the three points, and extrapolate the line until it intersects the concentration axis. From the intercept determine the concentration, in mg/mL, of lead in the Sample solution.
Calculate the quantity, in ppm, of lead in the specimen:
Result = (V1/W) × (V2/V3) × (C/F)
| V1 | = | = total volume of Sample solution, 100 mL |
| W | = | = weight of specimen (g) |
| V2 | = | = final volume of the solution used for analysis, 25 mL |
| V3 | = | = volume of Sample solution used for analysis, 10 mL |
| C | = | = concentration of lead in the Sample solution, as determined from the calibration curve (mg/mL) |
| F | = | = conversion factor, 0.001 µg/mg |
Acceptance criteria:
NMT 5 ppm
• Insoluble Matter
Sample solution:
Dissolve 10 g in a mixture of 100 mL of water and 7 mL of sulfuric acid.
Analysis:
Heat the Sample solution on a steam bath for 1 h. Filter the solution through a tared sintered-glass crucible, wash with hot water, and dry the crucible at 105
. Cool, and weigh.
. Cool, and weigh.
Acceptance criteria:
The residue weighs NMT 2 mg (0.02%).
• Substances Not Precipitated by Ammonium Sulfide
Sample solution:
Dissolve 1.0 g in 10 mL of water and 2 mL of sulfuric acid. Dilute with water to 80 mL, add 10 mL of ammonium hydroxide, and pass hydrogen sulfide through the solution for 30 min. Dilute with water to 100 mL, and allow the precipitate to settle. Decant the supernatant through a filter. Use the clear filtrate.
Analysis:
Transfer 50 mL of the Sample solution to a tared dish, and evaporate to dryness. Ignite, gently at first, and finally at 800 ± 25. Cool, and weigh.
. Cool, and weigh.
Acceptance criteria:
The weight of the residue is NMT 2 mg (0.4%).
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in tight containers.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Feiwen Mao, M.S.
Senior Scientific Liaison 1-301-816-8320 |
(SM32010) Monographs - Small Molecules 3 |
USP35–NF30 Page 5068