UMN CDMS Wiki archive
start › cdms › plasticscintillator › ebook › updatedbpoprocedure

Purifying Benzoyl Peroxide

Equipment

  • 250 mL Erlenmeyer flask
  • magnetic teflon stir bar
  • magnetic stir plate
  • vacuum flask
  • Büchner funnel / funnel paper
  • vacuum desiccator
  • vacuum aspirator
  • scroll pump

Chemicals

  • Unpurified benzoyl peroxide
  • methanol or petroleum ether
  • chloroform

1. Dissolve impurities

This procedure should be done for small amounts (<5 grams) of benzoyl peroxide ONLY as it can be explosive. Be sure this is done in the fume hood with the glass as low as feasibly possible.

In order to dissolve the benzoyl peroxide in chloroform, add small amounts of chloroform to an Erlenmeyer flask until the benzoyl peroxide in the flask dissolves. While adding the chloroform, the Erlenmeyer should be placed on the magnetic stir plate with a stir rod inside.

Precipitate out the purified benzoyl peroxide by adding in the exact same volume of methanol or petroleum ether. Now that the impurities in the benzoyl peroxide have been dissolved out, and only the pure benzoyl peroxide is left in the precipitate. The stir rod can either be removed now magnetically or during during the vacuum filtration.

2. Remove precipitate from liquid

In order to remove the precipitate from the liquid, a vacuum filtration setup must be used. The rubber line from the vacuum aspirator (attached to the water line in the fume hood) must be attached to the hose barb on the vacuum flask. A hose clamp might be necessary to insure a tight fit, but be careful not to break the glass! The Büchner funnel (ceramic funnel) is placed over the opening of the vacuum flask with a rubber cone in between to ensure a tight seal. Funnel paper (I recommend 2 pieces) should be placed over the top to block the holes. With the water running to generate vacuum, spray a little methanol on top of the filter paper so that it sticks to the bottom of the funnel. The mixture containing the benzoyl peroxide precipitate should be poured slowly into the funnel. After all visible liquid has been pulled through the funnel, transfer the purified benzoyl peroxide from the funnel paper to a clean watch glass. The liquid in the vacuum flask is organic waste. Do not mix this waste with styrene.

3. Dry under vacuum

The watch glass should be placed in the vacuum desiccator and connected to a vacuum pump in room temperature for 24 hours. The vacuum pump is the scroll pump found in the Cryo-lab (PAN 43). After 24 hours, the dried and purified benzoyl peroxide should be placed in a vial that has been wrapped in aluminum foil to block all light and placed in the refrigerator in Noireaux's lab (PAN 484).