3.2 Experiment: Osmosis 3 sets of 15 cm dialysis tubing were obtained, they had been presoaked in dH 2 O. 1 set of 15 cm dialysis tubing was used in another section of this experiment so a longer set of presoaked dialysis tubing was cut to 15 cm. One end of each dialysis tube was folded then tied with dental floss. The bags were then numbered one to four. Each bag was filled with 10 mL of a different solution. The first bag was filled with dH 2 O, bag two was filled with 15% sucrose solution, bag three was filled with 30% sucrose solution, and bag four was filled with dH 2 O. After each bag was filled, excess air was pushed out and the open end was folded and tied using dental floss. Next, the weight of each bag was recorded. Four beakers were obtained and marked one through four. Beakers one through three were filled with 100 mL of dH 2 O and beaker four was filled with 100 mL of 30% sucrose solution. The bags were placed in the correspondingly numbered beaker. After 15 minutes, the bags were removed from their beakers and the excess liquid was blotted off then the weight of each bag was recorded. This step was repeated at 30, 45, and 60 minutes. The results for this experiment are shown in table 2.
Westenberger 7 3.3 Experiment: Selective Permeability of Membranes A 15 cm section of dialysis tubing that had been soaked in dH 2 O was obtained instead of a 25 cm section. One end of was folded and tied with dental floss. The bag was then filled with 20 mL, rather than 25 mL because of the smaller bag size, of 1% sodium sulfate (Na 2 SO 4 ) and 1% soluble starch. The open end of the bag was then folded and tied using dental floss. A 400 mL beaker was acquired and 100 mL of 1% albumin and 1% sodium chloride (NaCl) solution was added to it. The bag was then placed into the beaker solution and left for 75 minutes. Eight test tubes were obtained and numbered. After 75 minutes, 20 mL of the beaker solution was poured into a 25 mL graduated cylinder so that 5 mL of this solution could be poured into four of the test tubes. Next, three drops of iodine solution were added to test tube one, if starch is present the solution would turn blue-black. Three drops of 2% barium chloride (BaCl 2 ) were added to test tube two, if sulfate is present a precipitate will form. In test tube three, three drops of silver nitrate (AgNO 3 ) were added to test for chloride ion, if the test is positive a milky white precipitate would form. Three drops of biuret reagent were added to test tube four to test for the presence of protein, if there was a change in color from blue to pinkish- violet then protein is present. The results are presented in table 3. Another 25 mL graduated cylinder was obtained and filled with the contents of the dialysis bag. Five mL of the solution was added to the other four test tubes. The test tubes were then tested for starch, sulfate, chloride, and protein using the same procedures. The results are displayed in table 4.
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- Spring '14
- Osmosis, Semipermeable membrane