ASTM D5799 Standard Test Method for Determination of Peroxides in Butadiene
8. Procedure
8.1 Remove the oxygen from a 250-mL Erlenmeyer flask by adding several pellets (approximately 1 cm in size) of dry ice and allowing the CO2 to displace the air. This will take approximately 5 min.
8.2 Record the weight to one decimal place of the sample cylinder, and then transfer approximately 100 mLs of butadiene sample from the cylinder to the 250 mL Erlenmeyer flask containing several pellets of dry ice. Reweigh the sample cylinder and record the weight of the sample as the difference of the two weights. (Warning - Butadiene is a flammable gas under pressure.)
8.3 Place the flask in a water bath at 60°C in a well ventilated hood. Allow the butadiene to evaporate while keeping an inert atmosphere above the liquid butadiene by continuing to add pellets of dry ice at intervals until all the butadiene has evaporated. (Warning - Peroxides are unstable and react violently when taken to dryness. Peroxides at the levels experienced during the test method evaluation have not caused a problem, but caution needs to be exhibited in handling by the use of personal protective equipment.)
8.4 Remove the flask from the water bath and allow to cool to ambient temperature. Add 50 mL of 94 % acetic acid and 0.20 +/- 0.02 g of sodium fluoride. Add several more pellets of dry ice to the flask and allow to stand for 5 min.
8.5 Add 6.0 +/- 0.2 g of sodium iodide to the flask and immediately connect to the Liebig condenser. Turn on the heating mantle and reflux the solution for 25 +/- 5 min. Keep the equipment away from strong light during refluxing.
8.6 At the end of the reaction period, turn off the heating mantle and remove the flask with condenser from the mantle. Immediately add 100 mL of water through the top of the condenser followed by several pellets of dry ice.
8.7 Maintaining an inert atmosphere with CO2 pellets, remove the flask from the condenser and allow to cool to ambient temperature. Cold water may be used to assist in this step. Titrate the liberated iodine with 0.1 N sodium thiosulfate until a clear endpoint is reached.
8.8 Repeat 8.4 through 8.7 for the reagent blank.
