Prepare a flask B as follows: Place 50 cm of the dried tetrahydrofuran provided into a 100 cm round bottomed flask and stopper it with a Suba seal. Next, the air in the flask needs to be replaced by pure Nitrogen, and this is achieved by passing a steady stream of nitrogen through the solvent for about 7 min. The procedure is to insert an exit hypodermic needle and a thick metal capillary from one of the nitrogen supply lines with a postive pressure - shown here. The solvent should bubble gently.
Now replace the exit needle with a length of steel capillary tubing and push the other end through the stopper of flask A. Insert an exit needle into flask A, turn off its Nitrogen supply at the side-arm tap and then transfer the solvent as shown from flask B to flask A. This is achieved by lowering the transfer tube below the solvent level in B; it may need to be moved during the transference as the level drops and should be continued until no solvent remains in flask B.
Remove both the outlet needle and transfer tube from flask A and turn off the Nitrogen supply to flask B. Repeatedly swirl flask A over 15-20 minutes taking care to avoid breaking the flask with the heavy amalgam. During this time the deep purple colour of the mixture turns to dark orange-brown. Clamp the flask and allow the excess amalgam to settle out for 4-5 minutes.