Specifications of Basic Zinc Carbonate USP Grade:
Zinc Carbonate USP Grade
3Zn(OH)2-2ZnCO3 549.01
Basic zinc carbonate.
Zinc subcarbonate [CAS 3486-35-9]
Zinc Carbonate contains the equivalent of not less than 70.0 percent of ZnO. (This 70%
ZnO is equivalent to 56.1% Zinc. We can also offer Zinc Carbonate of minimum 60% Zinc
content.)
Identification: A solution of it in a slight excess of hydrochloric acid responds
to the tests for Zinc.
Insoluble matter: Dissolve 10-g Zinc Carbonate in a mixture of 100 mL of water
and 7 mL of sulfuric acid, and heat on a steam bath for 1 hour. Filter the solution
through a tarred sintered-glass crucible, wash with hot water, dry the crucible at 105 ,
cool, and weigh: the residue weighs not more than 20 mg (0.02%).
Chloride: A 1.0-g Zinc Carbonate dissolved in a mixture of 20 mL of water and 3
mL of nitric acid shows no more chloride than corresponds to 0.03 mL of 0.02 N
hydrochloric acid (0.002%).
Sulfate: Dissolve 10.0-g Zinc Carbonate in a mixture of 75 mL of water and 10 mL
of hydrochloric acid, and filter. Neutralize the filtrate with ammonium hydroxide,
dilute with water to 100 mL, and mix. To 10.0 mL of this solution add 1 mL of 0.6 N
hydrochloric acid and 1 mL of barium chloride TS, mix, and allow to stand for 10
minutes. This test solution shows no more turbidity, if any, 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 test solution (0.01%).
Iron: Dissolve 1.0-g Zinc Carbonate in 20 mL of water and 3 mL of hydrochloric
acid: the limit is 0.002%.
Lead: the limit is 5 ppm.
Substances not precipitated by ammonium sulfide: Dissolve 1.0-g Zinc Carbonate 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 about 30 minutes.
Dilute with water to 100 mL, and allow the precipitate to settle. Decant the supernatant
through a filter, and transfer 50 mL of the clear filtrate to a tarred dish, evaporate
to dryness, ignite, gently at first and finally at 800 ± 25 , cool, and weigh: the
weight of the residue does not exceed 2 mg (0.4%).
Assay: Transfer about 2.0 g of Zinc Carbonate, accurately weighed, 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 consumed is equivalent to 40.69 mg of ZnO.
