Osmotic Pressure Example
An Egg in Karo Syrup
An excellent example of a semipermeable membrane is that inside the shell of an egg. After shell removal is accomplished with acetic acid, the membrane around the egg can be used to demonstrate osmosis. Karo syrup is essentially pure sugar, with very little water in it, so its osmotic pressure is very low. Placed in the syrup for 36 hours, the egg in the image below had most of the liquid of the eggwhite removed. What remained was essentially the membrane plus the yoke of the egg.
The egg's membrane is permeable to water molecules but not to the sugar molecules. Within an hour after the egg was placed in the syrup as shown at left, there is a visible layer around the egg. This is interpreted as a layer into which water molecules from inside the egg have penetrated, reducing the concentration of the syrup. Changing the concentration of the sugar solution changes its index of refraction. At certain angles, this change in index of refraction leads to total internal reflection, creating the mirror-like appearance of part of the layer.
Kinetic theory concepts
Applications of kinetic theory