»Precipitated Sulfur contains not less than 99.5 percent and not more than 100.5 percent of S, calculated on the anhydrous basis.
Packaging and storage Preserve in well-closed containers.
Identification It burns in the air, forming sulfur dioxide, which can be recognized by its characteristic odor.
Reaction Agitate 2.0 g with 10 mL of water, and filter: the filtrate is neutral to litmus.
Water, Method I 921: not more than 0.5%.
Residue on ignition 281: not more than 0.3%.
Other forms of sulfur Shake 1.0 g with 5 mL of carbon disulfide: it dissolves quickly, with the exception of a small amount of insoluble matter that is usually present.
Assay Using about 60 mg of Precipitated Sulfur, accurately weighed, proceed as directed under Oxygen Flask Combustion 471, using a 1000-mL flask and using a mixture of 10 mL of water and 5.0 mL of hydrogen peroxide TS as the absorbing liquid. When the combustion is complete, fill the lip of the flask with water, loosen the stopper, then rinse the stopper, the sample holder, and the sides of the flask with water, and remove the stopper assembly. Heat the contents of the flask to boiling, and boil for about 2 minutes. Cool to room temperature, add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N sodium hydroxide is equivalent to 1.603 mg of S.