BaSO4 233.39

Sulfuric acid,barium salt (1:1).
Barium sulfate (1:1) [7727-43-7].

Packaging and storage— Preserve in well-closed containers.

Identification—

pHá791ñ: between 3.5and 10.0,in a 10%(w/w)aqueous suspension.

Heavy metals á231ñ— Boil 4.0g with a mixture of 2mLof glacial acetic acid and 48mLof water for 10minutes.Dilute with water to 50mL,filter,and use 25mLof the filtrate:the limit is 0.001%.

Limit of sulfide— To 10g in a 500-mLconical flask add 100mLof 0.3Nhydrochloric acid.Cover the mouth of the flask with a circle of filter paper that has been moistened at the area over the mouth of the flask with 0.15mLof lead acetate TS,the paper being held in place with a string tied around the neck of the flask.Boil the mixture gently for 10minutes,taking care to avoid spattering the paper.Any darkening of the paper is not greater than that produced by a similarly treated control consisting of 100mLof 0.3Nhydrochloric acid containing 5µg of sulfide:not more than 0.5µg per g is found.

Limit of acid-soluble substances— Cool the mixture obtained in the test for Limit of sulfide,add water to restore approximately the original volume,and filter it through paper that previously has been washed with a mixture of 10mLof 3Nhydrochloric acid and 90mLof water,returning the first portions,if necessary,to obtain a clear filtrate.Evaporate 50mLof the filtrate on a steam bath to dryness,and add 2drops of hydrochloric acid and 10mLof hot water.Filter again through acid-washed paper,prepared as directed above,wash the filter with 10mLof hot water,and evaporate the combined filtrate and washings in a tared dish on a steam bath to dryness.The residue,when dried at 105for 1hour,weighs not more than 15mg:not more than 0.3%of acid-soluble substances is found.

Limit of soluble barium salts— Treat the residue obtained in the test for Limit of acid-soluble substanceswith 10mLof water,pass the solution through a filter previously washed with 100mLof 0.3Nhydrochloric acid,and add 0.5mLof 2Nsulfuric acid.Any turbidity formed within 30minutes is not greater than that produced in a similarly treated control consisting of 10mLof water containing 0.5mLof 2Nsulfuric acid and 50µg of barium:not more than 0.001%of soluble barium salts is found.

Assay— Accurately weigh not less than 0.58g and not more than 0.62g of Barium Sulfate in a tared platinum crucible,add 10g of anhydrous sodium carbonate,and mix by rotating the crucible.Fuse over a blast burner until a clear melt is obtained,and heat for an additional 30minutes.Cool,place the crucible in a 400-mLbeaker,add 250mLof water,stir with a glass rod,and heat to dislodge the melt.Remove the crucible from the beaker,and wash with water,collecting the washings in the beaker.Rinse the inside of the crucible with 2mLof 6Nacetic acid and then with water,again collecting the washings in the beaker,and continue heating and stirring until the melt is disintegrated.Cool the beaker in an ice bath until the precipitate settles,decant the clear liquid through filter paper (Whatman No.40,or equivalent),taking care to transfer as little precipitate as possible to the paper.Wash twice by decantation as follows.Wash down the inside of the beaker with about 10mLof cold sodium carbonate solution (1in 50),swirl the contents of the beaker,allow the precipitate to settle,and decant the supernatant through the same filter paper as before,transferring as little precipitate as possible.Place the beaker containing the bulk of the barium carbonate precipitate under the funnel,wash the filter paper with five 1-mLportions of 3Nhydrochloric acid,and wash the paper with water.[NOTE—The solution may be slightly hazy.]Add 100mLof water,5.0mLof hydrochloric acid,10.0mLof ammonium acetate solution (2in 5),25mLof potassium dichromate solution (1in 10),and 10.0g of urea.Cover the beaker with a watch glass,and digest at 80to 85for not less than 16hours.Filter while hot through a tared,fine-porosity,sintered-glass crucible,transferring all of the precipitate with the aid of a rubber-tipped stirring rod.Wash the precipitate with potassium dichromate solution (1in 200),and finally with about 20mLof water.Dry at 105for 2hours,cool,and weigh:the weight of the barium chromate so obtained,multiplied by 0.9213,represents the weight of BaSO4.

Expert Committee:(RMI)Radiopharmaceuticals and Medical Imaging Agents

USP28–NF23Page 219

Phone Number:1-301-816-8305