From household cleaners to laboratory samples, simple dilutions are all around you. Learning how to use dilution ratios to make dilutions from concentrated solutions or samples is a valuable skill both inside and outside the chemistry lab.
TL;DR (Too Long; Didn't Read)
A 1:4 dilution ratio means that a simple dilution contains one part concentrated solution or solute and four parts of the solvent, which is usually water. For example, frozen juice that requires one can of frozen juice plus four cans of water is a 1:4 simple dilution.
What Is a Solution?
Before you can make a simple dilution, it is a good idea to understand the terminology since some of the words sound similar. A solution is a liquid mixture where a smaller amount of a substance called a solute is mixed into a larger amount of a solvent like water. A solution with a great deal of solute is concentrated while a solution with a smaller amount of solute is dilute.
Sometimes you must use a concentrated solution and add more solvent (water) to create a simple dilution. To visualize, household bleach is a solution that contains sodium hypochlorite and water. This solution is much too concentrated to use directly from the bottle, so you add water in a spray bottle, bowl or the basin of the washing machine to create a simple dilution of bleach.
What Is a Dilution Ratio?
When you make a simple dilution that contains one part concentrated solution and four parts water as a solvent, you are using a 1:4 dilution ratio. This means there are five total parts in the diluted solution you have in the end. There are two simple ways to figure out how much solute and solvent you will need: measuring parts based on the amount of solute you have or measuring parts using your intended final volume.
Starting With the Solute
The first option works best when you know precisely how much solute or concentrated solution you have or want to use. For example, to make a simple dilution using a 1:4 dilution ratio with a 10 mL sample in a laboratory, you know that one part equals your 10 mL sample. If you multiply that one part (10 mL) by four parts, you know that you should add 40 mL of water to your sample, resulting in a 1:4 ratio (10 mL: 40 mL).
This strategy also works well for making a simple dilution when your end volume doesn’t really matter. For example, if you are making a dilution of bleach for household cleaning, you can quickly mix one part bleach (one ¼ cup scoop) with four parts water (1 cup since ¼ times 4 equals 1) to make your 1:4 dilution ratio.
Starting With Final Volume
If your simple dilution requires a more precise final volume, you should first determine how many total parts your final solution will contain. In a 1:4 ratio, there are five total parts (since 1 part plus 4 parts is 5 parts). You can then divide the end volume by the total parts to determine the volume of one part. For example, if you know you need 40 ounces of that 1:4 bleach dilution, you can divide 40 ounces by 5 parts and find that each part is 8 ounces. Using simple subtraction, you know you will need 8 ounces of bleach and 32 ounces of water.
Whether you are making simple dilutions to use in your home or in a laboratory, understanding dilution ratios is an invaluable skill.