00:00:02.100 --> 00:00:06.120 Once you've done your recrystallisation and you've got your hot filtrate this 00:00:06.120 --> 00:00:08.430 needs to be cooled to room temperature. 00:00:08.430 --> 00:00:11.790 If you want to do this quickly can use an ice bath. 00:00:11.790 --> 00:00:16.030 However you will get best crystals if you allow it to cool down slowly. 00:00:16.030 --> 00:00:22.590 If you do need to do this quickly, then use an ice bath, immerse your flask in the ice. 00:00:22.900 --> 00:00:26.280 If you want to leave this for a while make sure you clamp your flask. 00:00:27.980 --> 00:00:31.380 You can see the crystals are already coming out of solution. 00:00:31.380 --> 00:00:35.850 Make sure you allow the filtrate to cool to room temperature or below the 00:00:35.850 --> 00:00:38.610 crystals can then be collected by filtration. 00:00:38.610 --> 00:00:42.930 It's a good idea, however to keep the filtrate just in case you don't get a 00:00:42.930 --> 00:00:45.540 good yield. 00:00:45.540 --> 00:00:48.540 We're going to use a Buchner funnel to collect the crystals. 00:00:49.370 --> 00:00:55.610 Turn the water aspirator on full and connect it to the flask, so we apply 00:00:55.610 --> 00:01:03.050 reduced pressure to the flask. Make sure the funnel is well sealed. 00:01:06.880 --> 00:01:10.700 You can use a few drops of the solvent to seal the filter paper. 00:01:17.960 --> 00:01:22.240 Then carefully pour a small amount at a time with the filtrate containing the 00:01:22.250 --> 00:01:25.250 crystals into the middle of the filter paper. 00:01:57.630 --> 00:02:00.630 You can use some of the cold solvent to rinse the flask. 00:02:03.650 --> 00:02:07.010 Swirl it around to try to get the remainder of the solid out. 00:02:26.120 --> 00:02:30.780 You can now use a small amount of the cold solvent to rinse the crystals don't 00:02:30.780 --> 00:02:37.230 use too much though as you will start to dissolve them. Take the tubing off the flask 00:02:37.230 --> 00:02:46.230 before you turn the tap off. Otherwise you will get water sucked back into the flask. 00:02:48.280 --> 00:02:52.920 If you have got less material you could use a Hirsch funnel instead which works in the same 00:02:52.930 --> 00:02:55.270 principles as a Buchner funnel. 00:02:57.250 --> 00:03:00.810 You've got a filter paper covering the holes in the bottom of the funnel 00:03:01.800 --> 00:03:05.700 and a side arm which is attached to the water aspirator. 00:03:07.750 --> 00:03:11.380 Obviously the volume for the filtrate is a lot small as you need to make sure 00:03:11.380 --> 00:03:14.380 you're not filtering too much. 00:03:16.850 --> 00:03:18.650 Once you have separated your products 00:03:18.650 --> 00:03:22.950 it's a good idea, if you have time, to dry it in a vacuum desiccator. 00:03:23.280 --> 00:03:26.900 Carefully remove the filter paper from the Buchner funnel. 00:03:32.930 --> 00:03:37.930 Place it onto a bigger piece of filter paper and sandwich it between another piece. 00:03:44.920 --> 00:03:48.370 Then turn the edges over to make a parcel. 00:03:48.370 --> 00:03:52.810 It's a good idea to do this because when you come to open the vacuum desiccator 00:03:52.810 --> 00:03:57.099 after drying the crystals. They can easily be disturbed by the air flow 00:03:57.099 --> 00:04:02.800 through the tap whilst the pressures are equalising. This is a vacuum desiccator, 00:04:02.800 --> 00:04:07.810 if you take the outside cover off you'll see that there is a drying agent in the 00:04:07.810 --> 00:04:12.400 base, covered by a metal gauze, which is where we're going to put our compound. 00:04:12.400 --> 00:04:18.100 You can use a variety of drying agents but this is anhydrous calcium chloride. 00:04:21.460 --> 00:04:25.920 We're going to put our compound on top of the gauze and put the lid on. What 00:04:25.930 --> 00:04:29.680 we're going to do here is create a very dry atmosphere using this drying agent 00:04:29.680 --> 00:04:35.200 under reduce pressure because we're going to do this under reduce pressure 00:04:35.200 --> 00:04:37.740 we need to put a cover over the desiccator. 00:04:41.560 --> 00:04:43.320 Turn the aspirator on, 00:04:45.820 --> 00:04:53.919 make sure the tap is open and attach the tubing. Leave this for five minutes or 00:04:53.919 --> 00:04:57.520 so, close the tap, 00:04:59.800 --> 00:05:02.800 remove the tubing and turn the water tap off. 00:05:11.780 --> 00:05:16.460 When you come to open the desiccator, make sure you open the tap slowly so the 00:05:16.470 --> 00:05:19.470 flow of air back into the desiccator is slow. 00:05:27.820 --> 00:05:31.020 Once the pressure is equalised take the cover off, 00:05:34.820 --> 00:05:37.820 Remove the lid, and take the crystals out. 00:05:43.020 --> 00:05:46.820 The crystals should now be dry and ready to have a melting point taken, 00:05:46.830 --> 00:05:49.270 or further characterisation
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