S 32.07

Sulfur.
Sulfur [7704-34-9].

Packaging and storage— Preserve in well-closed containers.

Solubility in carbon disulfide— One g dissolves slowly and usually incompletely in about 2mLof carbon disulfide.

Identification— It burns in the air to sulfur dioxide,which can be recognized by its characteristic odor.

Residue on ignition á281ñ: not more than 0.5%.

Arsenic,Method Iá211ñ— Prepare the Test Preparationas follows.Digest 750mg of Sublimed Sulfur with 20mLof 6Nammonium hydroxide for 3hours,filter,and evaporate the clear filtrate on a steam bath to dryness.Add 15mLof 2Nsulfuric acid and 1mLof 30percent hydrogen peroxide solution,evaporate to strong fumes of sulfur trioxide,cool,add cautiously 10mLof water,and again evaporate to strong fumes,repeating,if necessary,to remove any trace of hydrogen peroxide.Cool,and dilute cautiously with water to 35mL.The limit is 4ppm.

Assay— Proceed as directed under Oxygen Flask Combustion á471ñ,using a 1000-mLflask and using about 60mg of Sublimed Sulfur,previously dried over phosphorus pentoxide for 4hours and accurately weighed,as the sample and a mixture of 10mLof water and 5.0mLof hydrogen peroxide TSas the absorbing liquid.When the combustion is complete,fill the lip of the flask with water,loosen the stopper,then rinse the stopper,sample holder,and sides of the flask with water,and remove the stopper assembly.Heat the contents of the flask to boiling,and boil for about 2minutes.Cool to room temperature,add phenolphthalein TS,and titrate with 0.1Nsodium hydroxide VS.Perform a blank determination,and make any necessary correction.Each mLof 0.1Nsodium hydroxide is equivalent to 1.603mg of S.

Expert Committee:(PA7)Pharmaceutical Analysis 7

USP28–NF23Page 1838

Phone Number:1-301-816-8394