Chemical Biology 3OA3, September 2009 Page 69 Step 2 . When a hot filtration is necessary, the solid should be dissolved as much as possible in a test tube as described above. Alternatively, the solid can be dissolved in the Craig tube and the liquid transferred to the test tube using a Pasteur pipette preheated with hot solvent. To draw the liquid into the pipette, expel the air from the pipette and then place the end of the pipette on the bottom of the tube, being careful not to trap any solid in the pipette. The small space between the pipette and the bottom of the tube should allow you to draw up the liquid without removing any solid. Rinse the Craig tube with a few drops of hot solvent, and then add these to the test tube. This procedure serves to perform a rough pre-filtration to remove larger pieces of solid. The Craig tube is then washed and dried. Step 3 . The test tube containing the mixture is then heated in the sand bath, adding 5-10 drops of solvent to ensure that premature crystallization doesn't occur during the filtration step. To filter
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