3Zn(OH)2·2ZnCO3 549.01
Basic zinc carbonate.
Zinc subcarbonate [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%).
