Knowing how to calculate dilutions is crucial to the safe practice of aromatherapy.

1. 1:4 Serial Dilution Table
2. Serial Dilution Table
3. Serial Dilution Definition
4. Serial Dilution Calculator
5. Serial Dilution Steps

It’s not enough to simply say “dilute before use on the skin”—this is insufficient information. You need to know which dilutions are safe and how to calculate them. With that information, you can use a chart like this to guide accurate dilution.

At the second table (serial dilution station): Begin with a sterile field by using a paper towel (obtain or share) to wipe the desktop with 70% EtOH (95% will dehydrate the bacteria rather than being absorbed to kill them). It is necessary to do this once at the beginning of the lab, but use your judgement if you think it needs to be done again. Serial Dilutions. Serial dilutions involve diluting a stock or standard solution multiple times in a row. Typically, the dilution factor remains constant for each dilution, resulting in an exponential decrease in concentration. For example, a ten-fold serial dilution could result in the following concentrations: 1 M, 0.1 M, 0.01 M, 0.001 M,.

To avoid the risk of skin allergy:

• Clove bud oil should be used at no more than 0.5%
• Holy Basil oil can be used at up to 1%

To avoid the risk of phototoxicity:

• Lemon oil should be used at no more than 2%
• Grapefruit oil can be used at up to 4%

Essential Calculation Class

You love essential oils, and you got hooked into aromatherapy – but nobody told you there will be math. Join Hana Tisserand as she guides you through calculations and conversions with ease, giving you simple tools and making sure you get it, so you will never again have to ask: “How many drops is that?”

When you're thinking about dilution, it helps to simplify your actions into dilution factors. When we said the diluted coffee was

'1/10th as strong as the original'

that was a dilution factor. We could also have said

'the dilution factor was 1/10', or

'the dilution factor was 0.1'.

Here are a few more for you to try:

1. 1 mL coffee + 4 mL water =
2. 1 mL coffee + 9mL water =
3. 1 mL + 99mL water =

As you've probably guessed, this works exactly the same whether you're talking about caffeine or meningicocci. Here's what a dilution factor of 0.01 looks like on the lab bench:

Notice that it really doesn't matter how much of the original stock you started with, as long as you had enough to put 1 mL into the new container. What matters is how much you transfer and how much water you add.

It's possible to write an algebraic expression for the dilution factor, but it's almost more trouble than it's worth, because it sounds so complex. But for what it's worth, the dilution factor for 1 mL stock + 99 mL water is:

amount transferred / total amount =

amount transferred / (amount transferred + amount water added) =

1:4 Serial Dilution Table

1 / (1+99) = 1/100 = 0.01.

Serial Dilution Table

Below is an applet to practice finding dilution factors, and also to determine how much water to add to achieve a given dilution. You should practice this until it is second nature!!

Can you do it in your sleep? OK, then go on to the next page...

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Serial Dilution Definition

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Serial Dilution Calculator

Serial Dilution Steps

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