Centrifugation (high-speed rotation) will be used to rapidly settle precipitates in solution. When loading test tubes into the centrifuge, two tubes of approximately equal volume must be placed opposite each other to balance the rotor. If other groups are not ready to centrifuge, you can simply put deionized water into an extra test tube for balance. Note the letter or number near the position of your
tube(s) so you can identify it (them) when centrifugation is complete. Never put stoppers or other items in the centrifuge with your tubes. Only test tubes are allowed in the centrifuge!
Figure 1

Figure 1

Always close the lid to the centrifuge while it is rotating. Many newer centrifuges have a safety switch that will not allow them to turn while the lid is open. Make sure that the lid is completely shut and the safety knob is turned to engage the safety switch. Then turn the timer knob to about 30 seconds. Turning the timer knob to zero or turning the safety knob on the lid will turn off the centrifuge. Do NOT open the lid to the centrifuge until the rotor has slowed down to prevent injury. Do NOT slow the rotor with your hand! This can result in injury AND it will stir up the solution you were attempting to separate by centrifugation. Wait for the rotor to come to a complete stop before attempting to remove your test tubes. After about 30 seconds of centrifugation most precipitates will have settled. And the liquid above it can be decanted (poured off).