to the precipitate.Draw air through the funnel for 5 min. Disconnect the pressure tubing from the side arm of the filter flask. Discard the filtrate in the bottom of the filter flask following the directions of your laboratory instructor. III. Isolating the Product by Gravity Filtration Place a clean filtering funnel in a funnel stand or in a utility clamp attached to a ring stand, as shown in Figure 4. Fold a piece of filter paper as shown in Figure 5. Fold the circle of filter paper exactly in half, as shown in Figure 5(b). Make a second fold, as shown in Figure 5(c), so that the edges of the filter paper do not quite match, as shown in Figure 5(d).Make certain the angle formed by the two edges of the paper is about 5 to 10 degrees. Tear off the corner of the smaller section of the fil- ter paper, as shown in Figure 5(e). Place the torn cor- ner in the paper cone, so that the mass of the paper at the end of the experiment will be the same as at the beginning. Place a 150-mL beaker under the funnel so that the stem of the funnel touches the side of the beaker, to 4 SYNT 341/Synthesis of Strontium Iodate Monohydrate Figure 1 A vacuum filtration apparatus Figure 2 Transferring a supernatant liquid from a beaker to a Büchner funnel Figure 3 Transferring precipitate from a beaker to a Büchner funnel Figure 4 A gravity filtration assembly FOR REVIEW ONLY - NOT FOR SALE OR CLASSROOM USE
eliminate splattering during filtration. Moisten the filter paper in the funnel with ice-cold distilled water from a wash bottle. Firmly press the edges of the filter paper against the funnel so that the paper adheres tightly to the funnel. This seal increases the filtration rate while preventing loss of product. Add sufficient ice-cold dis- tilled water to the funnel to fill the stem of the funnel. Decant as much of the supernatant liquid as possi- ble into the funnel. To prevent splashing and loss of precipitate, use a glass stirring rod to guide the liquid from the beaker into the funnel, as shown in Figure 6. Transfer the precipitate from the beaker to the fun- nel using a stream of ice-cold distilled water from the wash bottle, as shown in Figure 7.Wash as much of the precipitate as possible from the beaker into the funnel. Transfer any remaining precipitate using a stirring rod fitted with a rubber policeman. After you have trans- ferred the precipitate, position the stirring rod so that the attached rubber policeman is directly above the funnel.Direct a stream of distilled water from the wash bottle onto the policeman. Allow the washings to go into the funnel. Use a gentle stream of ice-cold water from a wash bottle to wash the precipitate down the sides of the filter paper cone into the bottom of the cone. Discard the filtrate in the beaker following the di- rections of your laboratory instructor. IV. Processing the Precipitate Carefully remove the filter paper and precipitate from the funnel. Place the paper and precipitate on your preweighed watch glass. If you used gravity filtration, carefully unfold the filter paper, and place it and the contents on the watch glass.