CaCO3 100.09

Carbonic acid,calcium salt (1:1).

Calcium carbonate (1:1) [471-34-1].

Packaging and storage— Preserve in well-closed containers.

Identification— The addition of acetic acid to it produces effervescence (presence of carbonate),and the resulting solution,after boiling,responds to the tests for Calcium á191ñ.

Loss on drying á731ñ— Dry it at 200for 4hours:it loses not more than 2.0%of its weight.

Acid-insoluble substances— Mix 5.0g with 10mLof water,and add hydrochloric acid,dropwise,with agitation,until it ceases to cause effervescence,then add water to make the mixture measure 200mL,and filter.Wash the insoluble residue with water until the last washing shows no chloride,and ignite:the weight of the residue does not exceed 10mg (0.2%).

Limit of fluoride— [NOTE—Prepare and store all solutions in plastic containers.]

Arsenic,Method Iá211ñ— Slowly dissolve 1.0g in 15mLof hydrochloric acid,and dilute with water to 55mL:the resulting solution meets the requirements of the test,the addition of 20mLof 7Nsulfuric acid specified under Procedurebeing omitted.The limit is 3ppm.

Barium— Aplatinum wire,dipped in the filtrate obtained in the test for Acid-insoluble substancesand held in a nonluminous flame,does not impart a green color.

Lead á251ñ— Mix 1.0g with 5mLof water,slowly add 8mLof 3Nhydrochloric acid,evaporate on a steam bath to dryness,and dissolve the residue in 5mLof water:the limit is 3ppm.

Iron— Dissolve 40mg in 5mLof 2Nhydrochloric acid,transfer to a beaker with the aid of water,and dilute with water to 10mL.Prepare a Standard solution by transferring 4.0mLof Standard Iron Solution,prepared as directed under Iron á241ñ,to a beaker and by diluting with water to 10mL.To each beaker add 2mLof citric acid solution (1in 5)and 2drops of thioglycolic acid,adjust to a pHof 9.5±0.1with ammonia TS,dilute with water to 20mL,mix,and allow to stand for 5minutes.Dilute with water to 50mL,and mix.Concomitantly determine the absorbances of the solutions from the specimen and the Standard solution at the wavelength of maximum absorbance at about 530nm with a suitable spectrophotometer,using water as the blank:the absorbance of the solution from the specimen under test does not exceed that of the Standard solution (0.1%).

Mercury,Method IIa á261ñ— Transfer 4.0g to a 100-mLbeaker,and cautiously dissolve in 14mLof 6Nhydrochloric acid.Use 3mLof hydrochloric acid instead of 3mLof sulfuric acid when preparing the Standard Preparationand the Test Preparation:the limit is 0.5µg per g.

Limit of magnesium and alkali salts— Mix 1.0g with 35mLof water,carefully add 3mLof hydrochloric acid,heat the solution,and boil for 1minute.Rapidly add 40mLof oxalic acid TS,and stir vigorously until precipitation is well established.Add immediately to the warm mixture 2drops of methyl red TSand then 6Nammonium hydroxide,dropwise,until the mixture is just alkaline.Cool to room temperature,transfer to a 100-mLgraduated cylinder,dilute with water to 100mL,mix,and allow to stand for 4hours or overnight.Filter,and to 50mLof the clear filtrate in a platinum dish add 0.5mLof 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.The weight of the residue does not exceed 5mg (1.0%).

Heavy metals á231ñ— Mix 1.0g with 5mLof water,slowly add 8mLof 3Nhydrochloric acid,and evaporate on a steam bath to dryness.Dissolve the residue in 20mLof water,filter,and add water to the filtrate to make 25mL:the limit is 0.002%.

Organic volatile impurities,Method IVá467ñ: meets the requirements.

Assay— Transfer about 200mg of Calcium Carbonate,previously dried at 200for 4hours and accurately weighed,to a 250-mLbeaker.Moisten thoroughly with a few mLof water,and add,dropwise,sufficient 3Nhydrochloric acid to dissolve.Add 100mLof water,15mLof 1Nsodium hydroxide,and 300mg of hydroxy naphthol blue,and titrate with 0.05Medetate disodium VSuntil the solution is a distinct blue in color.Each mLof 0.05Medetate disodium is equivalent to 5.004mg of CaCO3.

Expert Committee:(DSN)Dietary Supplements:Non-Botanicals

USP28–NF23Page 319

Phone Number:1-301-816-8389