Barium Sulfate for Suspension
» Barium Sulfate for Suspension is a dry mixture of Barium Sulfate and one or more suitable dispersing and/or suspending agents. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of barium sulfate (BaSO4). It may contain one or more suitable colors, flavors, fluidizing agents, and preservatives.
Packaging and storage Preserve in well-closed containers.
Identification Ignite a 1-g portion to constant weight: the ignited residue meets the requirements for Identification tests A and B under Barium Sulfate.
pH 791: between 3.5 and 10.0, in a 60% (w/w) aqueous suspension, or constituted for its intended use as directed in the labeling.
Loss on drying 731 Dry it at 105 for 4 hours: it loses not more than 1.0% of its weight.
Assay Weigh accurately a quantity of Barium Sulfate for Suspension, equivalent to about 0.60 g of barium sulfate (BaSO4), in a tared platinum crucible, and ignite over a low flame until any organic matter is thoroughly carbonized. Cool, cautiously add 0.5 mL of nitric acid and 0.5 mL of sulfuric acid, and continue the ignition over a low flame until the residue becomes gray in color, then ignite over the full heat of a blast burner. Allow the contents of the crucible to cool to room temperature.
[note 1If the specimen contains a silicate, such as bentonite, proceed as follows. Add 10 mL of water and 1 mL of sulfuric acid to the residue in the crucible, mix, and add 10 mL of hydrofluoric acid. Heat gently over a low flame until fumes of sulfur trioxide appear. Add 5 mL more of hydrofluoric acid, heat again over a low flame to the appearance of dense fumes, and continue heating until the sulfuric acid has been completely volatilized. Allow the contents of the crucible to cool. ]
[note 2If the specimen does not contain a silicate, omit the treatment of the specimen with hydrofluoric and sulfuric acids. ]
Add to the treated or untreated specimen in the platinum crucible 10 g of anhydrous sodium carbonate, fuse over a blast burner until a clear melt is obtained, and heat for an additional 30 minutes. Proceed as directed in the Assay under Barium Sulfate, beginning with Cool, place the crucible in a 400-mL beaker.
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USP35NF30 Page 2307Pharmacopeial Forum: Volume No. 28(1) Page 39