Assay Procedures Of active oxygen of APS and PPS. Persulfates or their solutions can be conveniently assayed by the methods described below.Â
All reagents, chemicals, and apparatus used are common, off-the-shelf items, and can be purchased from commercial supply houses.
Assay Procedures APS and PPS
Solids by
To a 250 mL Erlenmeyer flask, add about 1 gram of sample weighed to the nearest milligram and about 50 mL of 1N H2SO4.Â
Dissolve the sample and add exactly 40 mL of 0.5 N ferrous ammonium sulfate solution.Â
Swirl constantly while adding the ferrous ammonium sulfate solution. Let this stand for one minute and titrate with 0.5 N KMnO4 to a permanent pink endpoint or with 0.5 N Ce(SO4)2 to a Ferroin indicator endpoint.Â
The calculations require a blank titration on exactly 40 mL of ferrous ammonium sulfate solution, as used above, in 50 mL of the 1 N H2SO4.Â
% active oxygen =Â Â Â Â Â Â Â Â Â Â Â ( A - B )C*0.8Â Â Â Â Â Â
                              D
% ammonium persulfate =Â Â Â Â ( A - B)C*11.4
                              D
% potassium persulfate =Â Â Â Â Â ( A - B)C*13.5
                              D Â
% sodium persulfate =Â Â Â Â Â Â Â ( A - B)C*11.9
                              D
A = mL KMnO4 or Ce(SO4)2 solution used for titrating the blank.
B = mL KMnO4 or Ce(SO4)2 solution used for titrating the sample.
C = Normality of the KMnO4 or Ce(SO4)2 solution used.
D = Weight of sample in grams.
Solutions by
To a 250 mL Erlenmeyer flask, pipette 2-20 mL of persulfate solution (depending on the approximate solution concentration).Â
Add about 50 mL of about 1 N H2SO4 solution. Add exactly 40 mL of 0.5 N ferrous ammonium sulfate solution. Swirl constantly while adding the ferrous ammonium sulfate solution.
Let stand for one minute and titrate with 0.5 N KMnO4 to a permanent pink endpoint or with 0.5 NÂ Ce(SO4)2 to a Ferroin indicator endpoint.Â
The calculations require a blank titration on exactly 40 mLÂ of ferrous ammonium sulfate solution, as used above, in 50 mL of the 1 N H2SO4.
gm/l active oxygen =Â Â Â Â Â Â Â Â Â Â Â Â ( A - B )C*8.0Â Â Â Â Â Â Â
                              D
gm/l ammonium persulfate =Â Â Â Â Â ( A - B)C*114
                              D
gm/l potassium persulfate =Â Â Â Â Â ( A - B)C*135
                              D Â
gm/l sodium persulfate =Â Â Â Â Â Â Â ( A - B)C*119
                              D
A = mL KMnO4 or Ce(SO4)2 solution used for titrating the blank.
B = mL KMnO4 or Ce(SO4)2 solution used for titrating the sample.
C = Normality of the KMnO4 or Ce(SO4)2 solution used.
D = Volume of sample in milliliters.
