Osmosis experiments

Visking tubing is an artificial partially permeable membrane:

  • smaller molecules like water and glucose pass through its microscopic holes
  • larger molecules like starch and sucrose cannot pass through it

The slideshow shows a typical experiment using Visking tubing and sucrose solution:

Part one of four. A beaker of water. A capillary tube with visking tubing attached is partly submerged. The visking tubing contains a sucrose solution. The liquid rises up the capillary tube.

Visking tubing experiment

1. The Visking tubing is partly submerged into water and the liquid rises

The sucrose solution is hypertonic to the water – it is a more concentrated solution. There is a net movement of water molecules, by osmosis, from the water outside to the sucrose solution inside the Visking tubing. This makes the liquid level in the capillary tube rise.

A less concentrated solution is hypotonic to a more concentrated solution, while two solutions at the same concentration are isotonic.

The table summarises the results of the four combinations of water and 10% sucrose in the experiments, showing the movement of water and solute across a concentration gradient.

Liquid outsideLiquid insideWater movesSolute movesResult
Water10% sucroseOutside → insideInside → outsideLiquid level rises
10% sucroseWaterInside → outsideOutside → insideLiquid level falls
WaterWaterNo movementNo movementNo visible change
10% sucrose10% sucroseNo movementNo movementNo visible change