Clamp a wide-necked 250 ml round-bottomed flask in a water bath on a magnetic stirrer/hot plate. Place 150 ml n-pentane and a magnetic stirrer bar into the flask and attach a reflux condenser. Then, slowly, and with rapid stirring (to prevent the beads from sticking together), add about half of the dried polyStyrene beads. When all of the beads (total 10 g) have been added, gently reflux the contents of the flask at 40 ฐC for about 2 hours. Finally, remove the condenser, pour off the n-pentane, and allow the beads to cool to room temperature.