What is the serial dilution technique?
Suppose you have a solution of concentration 10 mol/dm^3. You want to make a 1:10 dilution of the solution. To do this, mix 1 part solution with 9 parts water. So if, for example, you take 1ml of the solution and mix it with 9ml of water, you will have made a 1:10 dilution. So now the concentration is 1 mol/dm^3. Now, to make a 1:100 dilution of the original solution, you can just make a 1:10 dilution of the second solution because that is already a 1:10 dilution of the first. So, take 1ml of the 1 mol/dm^3 solution and mix it with 9ml of water, and now you have a 1:100 dilution which has a concentration of 0.1 mol/dm^3. You can keep doing it this way to create serial dilutions of 1:1000, 1:10000, 1:100000 etc.