Calculating Dilution Solutions

A dilution solution contains solute (or stock solution) and a solvent (called diluent). These two components proportionally combine to create a dilution. You can identify a dilution solution by the amount of solute in the total volume, expressed as a proportion. For example, a chemical may be prepared in a 1:10 dilution of alcohol, indicating that a 10 mL bottle contains one milliliter of chemical and nine milliliters of alcohol. You can calculate the necessary volume of each component to prepare a dilution solution.

Step 1

Write down the desired final volume of the solution–for example, 30 mL.

Step 2

Write down the desired dilution in the form of a proportion–for example, 1:20 dilution, also known as the dilution factor.

Step 3

Convert the dilution factor to a fraction with the first number as the numerator and the second number as the denominator. For example, a 1:20 dilution converts to a 1/20 dilution factor.

Step 4

Multiply the final desired volume by the dilution factor to determine the needed volume of the stock solution. In our example, 30 mL x 1 ÷ 20 = 1.5 mL of stock solution.

Step 5

Subtract this figure from the final desired volume to calculate the volume of diluent required–for example, 30 mL – 1.5 mL = 28.5 mL.

Step 6

Measure the amount of stock solution required — in our example, 1.5 mL — and dispense this into a large measuring cup.

Step 7

Measure the amount of diluent required — in our example, 28.5 mL — and dispense this into the large measuring cup.

Step 8

Mix the solution with the glass stirring rod. You now have your 1:20 dilution solution.

Things Needed

• Graduated cylinder
• Measuring cup
• Glass stirring rod
• Calculator