Osmotic Pressure, Hydrostatic Pressure
Osmosis of a sucrose solution through a semi-permeable dialysis membrane bag is demonstrated. The 20 thumbnail images summarize the content of the video. Click an image to see the image gallery.
An acidic sucrose solution containing methyl red indicator is poured into a semi-permeable dialysis membrane bag. The indicator is red in this acidic solution. The membrane bag is immersed in a neutral solution.
The solution inside the membrane turns yellow as the neutral liquid diffuses into the bag. The indicator is yellow at neutral pH. The level of the liquid in the column rises as this change occurs. The pressure in the column forces some of the solution containing indicator out of the bottom of the dialysis bag. In this neutral solution, the indicator is yellow. When acid is added to the solution in the beaker, the indicator color turns to pink.
A sucrose solution containing red-colored methyl red indicator at a pH of 4.5 is added to a semi-permeable dialysis membrane bag. The membrane bag is immersed in a solution of pH 7.0. The solution inside the membrane becomes yellow as the pH is raised due to the flow of pH 7.0 solution into the dialysis membrane. The column also rises as this change occurs.
The pressure exerted by the column forces some of the solution in the dialysis membrane bag out of the bottom of the dialysis bag. The presence of this yellow solution is observed by adding acid to the beaker to change the yellow methyl red to the more intense red color.
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