Varying the concentration of solutions

Experiment 3: Effect of graded series of hypotonic saline solutions

What factors & particle properties determine how quickly substances move across an RBC membrane to cause the RBC to swell and lyse?

We will explore that in three Experiments 3, 4 and 5.

In Experiment 3, which you will do on this page, we will expand what we did in Experiments 1 and 2, using a range of saline concentrations.

Recall that in Experiment 1 we used 100% Physiological saline and Distilled water (i.e., 0% Physiological Saline). We found that lysis was instantaneous in the second solution and never happened in the first solution.

In Experiment 2 we used 50% Physiological Saline (hypotonic saline) and found lysis occurred with a time value between instantaneous and never! Not very satisfactory science if all we test and see is "Never", "Immediate", and "Somewhere-in-between"! We have no idea what is the shape of the curve between % Physiological saline and Time for lysis!

So now we are going to create a series of other hypotonic saline solutions between 0% Physiological saline (Distilled water) and 100% Physiological saline, and test for lysis. This should give us a series of values that allows us to draw a curve for the relationship between % Physiological saline and Time for lysis.

That is what we will do in Experiment 3, as you can see in the Table below


  1. Using the proportions shown in the table below, mix a solution containing both distilled water and physiological saline in your test tube.
  2. Add some blood to your test tube and time how long it takes for the mixture to clear up enough to see the light.
  3. Record the time taken for your solution in the table below.
  4. Repeat for other mixtures and record your results in the table.

Note: If lysis doesn't occur within 90 seconds, we assume it will never occur, and you should enter a value of 90 seconds for that trial.

Distilled water volume (mL) Isotonic saline volume (mL) End product Haemolysis time (s)
4 1 20% saline
3 2 40% saline
2 3 60% saline
1 4 80% saline