Famous Females: Agnes Pockels

SURFACE SCIENCE!

INSPIRING WOMEN

Welcome to Yellow Scope's ‘Famous Females’ series, where we highlight amazing women scientists of the past and present!

Throughout history, women have struggled to find a place in the world of science. Even if a woman made a scientific breakthrough, a man would often end up taking the credit (*cough* Rosalind Franklin, *cough* Nettie Stevens...).

However, this edition depicts a great example of men showing encouragement and honesty toward the brilliant woman they saw making important strides.

AGNES POCKELS (1862 – 1935)

Women interested in STEM can struggle with opportunity, but it was worse back in the day. In the late 1800s, Agnes Pockels had everything taken away from her but the kitchen sink, literally! She did science with dishwater!

Agnes lived in Germany and loved physics in school. She wanted to study it in college, but girls weren’t allowed into higher education there at the time. Even when that changed, her ailing parents prevented her from attending.

So Pockels stayed at home to care for them, mostly cooking and cleaning. Water became her constant companion, and she started noticing things and asking questions.

Agnes wanted to know how the surface of water worked. What happened if she added soap? Oil? Salt? How could she find out?

POCKELS' TROUGH

From household supplies, Pockels created a trough to hold water filled to the brim, then separated the top of the water in half with a tin strip. By sliding it back and forth she could change the surface area of each side.

Using a small button hanging from a wooden balance, she was able to measure the difference in surface tension under various conditions. This (modified) method is still used today!

Her big discovery? Surface tension dropped when she added detergent to one side!

Why is this? Well, we now know water is very attracted to itself. It doesn't like air nearly as much, so water molecules in contact with air at the surface hold on desperately to their watery neighbors instead, creating a strong surface tension.

Soap molecules have chemically different ends. One is a water-loving (hydrophilic) head and the other a water-fearing (hydrophobic) tail.

When you add soap to water, all the heads dive in, but the tails stick out into the air. They all line up at the surface like buoys so that the tails touch the least amount of water as possible, covering the surface.

Water is attracted to the water-loving heads of the soap. Now that the top water molecules have soap above them instead of air, they can be attracted upwards too, instead of just side to side. This weakens the attraction between the surface water molecules, reducing surface tension.

GOOD MEN NOT HARD TO FIND

By now her younger brother became her ally. He was in college studying physics and sent her books and papers on the subject so she could teach herself.

She eventually wrote to a man studying similar properties named Lord Rayleigh. Luckily his wife knew German, and was able to translate the letter to English.

Check out Pockels' fancy prose:

“My lord, will you kindly excuse my venturing to trouble you with a German letter on a scientific subject? Having heard of the fruitful researches carried on by you last year on the hitherto little understood properties of water surfaces, I thought it might interest you to know of my own observations on the subject.”

To his great credit, he sent her observations to be published in the journal Nature. He wrote that Pockels:

"...with very homely appliances has arrived at valuable results...The later sections seem to me very suggestive, raising, if they do not fully answer, many important questions.”

And so, Agnes Pockels became a founder of ‘surface science’. Without ever holding a single job, she published many more papers.

In 1931, at 71 years old, she was awarded an honorary doctorate from the Technology University of Brunswick. She died at 73.

As you’ll see in the next edition, her trough was improved upon, and eventually led to another famous female inventing invisibility. Wait, what? Stay tuned!