00:00:01.140 --> 00:00:04.440 The technique of liquid-liquid extraction is a form of solvent 00:00:04.440 --> 00:00:08.880 extraction which is often referred to simply as a separation. We do this using 00:00:08.880 --> 00:00:11.370 the separating funnel as shown on the screen. 00:00:11.370 --> 00:00:14.490 The technique can be used in a range of contexts and it's important that you 00:00:14.500 --> 00:00:17.400 understand why you're carrying out a separation in the experiment that you're 00:00:17.400 --> 00:00:22.499 doing. In this demonstration we have a solution of a product of a reaction in 00:00:22.499 --> 00:00:25.679 an organic solvent which in this case is diethyl ether. 00:00:25.679 --> 00:00:29.609 We are going to wash the solution with water to remove impurities which are 00:00:29.609 --> 00:00:30.779 water soluble. 00:00:30.779 --> 00:00:34.590 The first step is to remove the magnetic stirring flee from the reaction flask. 00:00:35.219 --> 00:00:38.919 We need to wash this with ether to ensure that we don't lose any of our product. 00:00:40.640 --> 00:00:44.140 We now need to pour the solution of our product into the separating funnel 00:00:44.140 --> 00:00:49.920 taking care to avoid any spillages, so it's wise to use a small glass funnel as we pour. 00:00:51.780 --> 00:00:56.740 Then we can rinse our reaction flask with more ether to ensure that no product is lost. 00:01:02.940 --> 00:01:06.860 Now we add the water which we are using to wash our reaction mixture with. 00:01:06.960 --> 00:01:09.440 It's important that you pay attention to your script which may 00:01:09.450 --> 00:01:13.350 specify a different solvent and a particular volume that you need to work with. 00:01:14.280 --> 00:01:17.700 Next, you need to place a stopper in the neck of the separating funnel and you 00:01:17.700 --> 00:01:20.700 must ensure that you don't allow this to fall out any point while you're handling 00:01:20.700 --> 00:01:22.500 the apparatus. 00:01:22.500 --> 00:01:26.010 Secure the stopper with one hand and carefully invert the separating funnel. 00:01:26.670 --> 00:01:30.330 Now you can gently shake the funnel while periodically opening the tap to release 00:01:30.330 --> 00:01:31.170 pressure. 00:01:32.780 --> 00:01:36.420 Normal you carry out these steps several times to ensure thorough mixing of the 00:01:36.420 --> 00:01:41.729 two layers and then with the tap closed you can carefully replace the funnel in 00:01:41.729 --> 00:01:43.689 the ring on the clamp stand. 00:01:48.260 --> 00:01:52.280 Here you can clearly see the two separate layers in the funnel. In this 00:01:52.280 --> 00:01:56.030 case the denser aqueous layer is at the bottom and the ether layer is on top. 00:01:56.750 --> 00:01:59.899 However you should never make assumptions about which layers is which and you 00:01:59.899 --> 00:02:03.200 may be given instructions that tell you how to test which layer is organic 00:02:03.200 --> 00:02:05.130 and which is aqueous. 00:02:05.130 --> 00:02:08.610 Before running any solvent out of the funnel you must first remove the stopper. 00:02:08.610 --> 00:02:13.050 Not doing so is a common error which will prevent the solvent from running freely. 00:02:14.500 --> 00:02:18.060 Now you should place an appropriately sized conical flask under the separating 00:02:18.060 --> 00:02:22.080 funnel before carefully opening the tap to allow the lower layer to run out. 00:02:22.080 --> 00:02:25.349 You should watch patiently as the interface between the two layers moves 00:02:25.349 --> 00:02:29.130 towards the tap. So you are able to stop the flow once all of the lower layer has 00:02:29.130 --> 00:02:30.300 been removed. 00:02:30.300 --> 00:02:33.680 Remember that in this case the lower layer was the aqueous layer. 00:02:35.680 --> 00:02:39.740 Now you can remove this flask and place a second clean conical flask under the 00:02:39.750 --> 00:02:42.750 separating funnel to collect the upper layer. 00:02:55.180 --> 00:02:58.860 As always you should check your script to see what you've got to do next. 00:02:59.079 --> 00:03:02.680 You may be expected to return one of the layers to the separating funnel to carry 00:03:02.680 --> 00:03:07.299 out further extraction steps. In this case however, we are simply going to dry 00:03:07.299 --> 00:03:11.560 the organic layer using magnesium sulfate other drying agents that may be 00:03:11.560 --> 00:03:14.709 used could include calcium chloride and sodium sulfate. 00:03:14.709 --> 00:03:19.750 So make sure you read the script before proceeding. If the drying agent forms 00:03:19.750 --> 00:03:21.280 clumps as shown here 00:03:21.280 --> 00:03:25.600 that's a sign that the solution is still wet and that more drying agent is required. 00:03:27.420 --> 00:03:30.940 When you can see a snow storm effect like this you know that the solution is 00:03:30.950 --> 00:03:33.590 dry and that no more drying agent is needed. 00:03:33.590 --> 00:03:37.670 You can now remove the drying agent by gravity filtration before consulting the 00:03:37.670 --> 00:03:40.470 script once again to identify your next step.
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