Question

yellow, green or red, the test is positive. The color of the solution depends on the concentration of 3. Observe the color of your negative and positive controls. Note which one has a red color. 4 After the dialysis of the NaCi-elucose-red dye solution has progressed for an hour, test the water outside the dialysis bag (your experimental data) for the presence of Ci and glucose same way you did for your controls in steps 1 and 2. Observe if any of the red dye has come out of the bag. Write glucose in this solution. down your results in the table 1. PART. B. OSMOSIS 1. Take a piece of dialysis bag tubing and allow it to soak in a beaker of water to soften it. When the tubing is completely soft, tie a knot at one end. 2. Fill the bag with a 10% sucrose solution and then place a piece of long, narrow glass tubing into the sucrose solution in the dialysis bag. The glass tubing should be new (used one will not work). Tie the dialysis tubing tightly around the glass tubing eliminating all air bubbles! 3. Rinse the assembly in tap water and make sure that the sugar solution does not leak from the dialysis bag. Place this set-up in a beaker of tab water and with the aid of a glass- marking pencil place a mark on the glass tubing at the height where the sucrose solution is. 4. Allow the set-up to remain in the beaker of water throughout the laboratory period with frequent observations of the height of the liquid level in the glass tubing. Using a ruler, measure every 10 min the distance from the first mark to the new surface of the sucrose solution in the tube. Record your observations in the Table 2. sucroses REPORT Table 1. Dialysis results. Testing for ions: Sample Test for Cl' Test for glucose Test for Congo red dye with Visual observation with Reaction Reaction Tests used AgNO Benedict solution Deionized water (negative control) Original red dye-glucose-NaCl solution (positive control) Experimental sample (from the beaker after the dialysis is over) 61

Answer 1

Testing for halide ions like chlorine, fluoride, bromide and iodide is performed using silver nitrate and ammonia solution. In the presence of chloride ions, a white precipitate of silver chloride will be formed.

Benedict's solution identifies reducing sugars (free ketone or aldehyde functional groups). These reducing sugars, reduce the copper (II) ions in the Benedict's solution to copper (I) ions, resulting in a red/brick red colour.

Congo red stain is used to stain for plant and fungi cell walls and the outer membrane of Gram negative bacteria.