Surfactant Science - Traube’s Rule

While it doesn’t come up too often when creating cosmetic formulations, it is useful for cosmetic chemists to know the concept of Traube’s Rule. At the very least it will help you understand why some of your raw materials contain one surfactant over another and could give you a clue on how to fix potential stability problems.

Traube’s Rule

Traube’s Rule is a relationship between hydrocarbon chain length and surfactant activity. It states that for every extra CH2 group in a surfactant molecule, the surface activity approximately triples.

So, shorter chain length molecules have less surface activity than higher chain length molecules. In terms of cleansing or emulsification that means you can get away with using a much lower concentration of a longer chain length surfactant.

Let’s look at the example of Sodium Lauryl Sulfate (C12) and Sodium Cetyl Sulfate (C16).

Using Traube’s Rule we know that the Sodium Cetyl Sulfate will have 81 times the surface activity of Sodium Lauryl Sulfate at the same concentration. Theoretically, that would be a big cost savings if you switched over your formulas!

But alas, it doesn’t quite work that way. You see Traube’s Rule only applies to dilute aqueous solutions of surfactants. Solutions that are so dilute that the surfactants don’t form micelles. That wouldn’t apply to most cosmetics.

However, this represents the edges of scientific research and it might be interesting to do an experiment to see what the lowest level of surfactant you could use to have a functional, consumer acceptable cleansing product. Maybe Traube’s Rule could help.

Decreasing surface activity

Incidentally, there is a similar but opposite effect if you increase the length of the hydrocarbon chain using ethylene oxide which is hydrophilic. That means molecules with higher numbers of PEG will be more water soluble than ones with lower numbers.

References

Interested in more detail about this and other surfactant subjects?  Check out this link.

Related Articles

How to Become a Cosmetic Chemist

The job of a cosmetic chemist, or as they call it in the UK a cosmetic scientist, requires you to do a wide variety of things both in and out of the lab. Your main responsibility will be that of a formulator. This means you mix raw materials together to create cosmetic products like lipstick, nail polish, skin lotions, shampoos, toothpaste and any other type of personal care product.

Cosmetic Science Programs Around the World

A list of cosmetic science schools and other programs that teach you how to create your own cosmetic formulas and beauty products. If you are truly interested in making products like it is done in the cosmetic industry or in getting a job as a cosmetic chemist, the following courses are legitimate programs recognized by people and companies in the cosmetic industry.

Responses

Your email address will not be published. Required fields are marked *


Free Report

Sign up now to get a free report "How to Duplicate any cosmetic formula". Plus a 4-part introduction to cosmetic science mini-course.

We respect your email privacy