Sulfate content—
Transfer about 1 g, accurately weighed, to a 250-mL beaker, and dissolve in about 100 mL of water. Neutralize the solution with 7.5 N ammonium hydroxide to litmus paper, and warm. Filter, and wash the filter with warm water. Neutralize the filtrate with 6 N hydrochloric acid to litmus, and add an additional 4 mL of 6 N hydrochloric acid. Heat the solution to boiling, and add, with constant stirring, sufficient boiling barium chloride TS to precipitate all of the sulfate. Add an additional 2 mL of
barium chloride TS, and digest on a steam bath for 1 hour. Filter the mixture through ashless filter paper, transferring the residue quantitatively to the filter, and wash the residue with hot water until no precipitate is obtained when 1 mL of
silver nitrate TS is added to 5 mL of washing. Transfer the paper containing the residue to a tared crucible. Char the paper, without burning, and ignite the crucible and its contents to constant weight. Perform a blank determination concurrently with the test specimen determination, and subtract the weight of residue obtained from that obtained in the test specimen determination to obtain the weight of residue attributable to the sulfate content of the specimen: not less than 15.0% is found, calculated on the dried and butyl alcohol-free basis.
Butyl alcohol—
Ceric ammonium nitrate solution—
Dissolve 20 g of ceric ammonium nitrate in 4 N nitric acid to obtain 100 mL of solution.
Standard preparations—
Transfer about 3 g of butyl alcohol, accurately weighed, to a 1000-mL volumetric flask containing 800 mL of water, shake to dissolve, dilute with water to volume, and mix (Standard preparation 1). Transfer 10.0 mL of Standard preparation 1 and 1 drop of dimethicone to a 50-mL distilling flask equipped with a condenser and an extension that reaches into a collecting tube maintained in an ice-water bath. Distill slowly, and collect about 8 mL of distillate. Warm the distillate to ambient temperature, and transfer with the aid of water to a 10-mL volumetric flask. Dilute with water to volume, and mix (Standard preparation 2).
Test preparation—
Transfer an accurately weighed specimen, equivalent to about 30 mg of butyl alcohol, to a 50-mL distilling flask equipped with a condenser and an extension that reaches into a collecting tube maintained in an ice bath. Add 25 mL of water and 1 drop of dimethicone to the distilling flask. Distill slowly, and collect about 8 mL of the distillate. Warm the distillate to ambient temperature, and transfer with the aid of water to a 10-mL volumetric flask. Dilute with water to volume, and mix.
Procedure—
To four separate test tubes add, respectively, 5.0 mL of
Standard preparation 1, 5.0 mL of
Standard preparation 2, 5.0 mL of
Test preparation, and 5.0 mL of water to provide a blank. To each add 2.0 mL of
Ceric ammonium nitrate solution, and mix. Concomitantly determine the absorbances of the solutions from the
Standard preparations and the
Test preparation at the wavelength of maximum absorbance at about 475 nm, with a suitable spectrophotometer, using the blank to set the instrument to zero. In a suitable determination, the absorbance of the solution from
Standard preparation 2 is not less than 98.0% of the absorbance of the solution from
Standard preparation 1. Calculate the percentage of butyl alcohol in the specimen taken by the formula:
1000(WS / WU)(AU / AS),
in which
WS is the weight, in g, of butyl alcohol taken to prepare
Standard preparation 1,
WU is the weight, in mg, of specimen taken, and
AU and
AS are the absorbances of the solutions from the
Test preparation and
Standard preparation 2, respectively: not more than 15.0% is found.
197U
—
for 3 hours: it loses not more than 2.0% of its weight.