Happy Ada Lovelace Day!
Ada Lovelace Day is a yearly celebration of women in science, increasing the profile of women in science, technology, engineering and maths and creating more role models in doing so. Each year, many grassroots events are organised around the world for Ada Lovelace Day, one of which is blogging about any woman in science you admire. We've picked a remarkable citizen scientist from many years ago named Agnes Pockels, whose work on surface tension paved the way for many scientists later on.
Pockels was born in Venice, which at the time (1862) was part of the Austrian empire and in which her father was stationed as a soldier. When she was about 9, her father caught malaria and both her parents were in extremely poor health for the rest of their lives. They moved to Braunschweig (Brunswick in English) where her father retired. Agnes attended the local girls' school but by her late teens was an almost full-time carer for her parents.
She loved science, but her school did not teach physics and women could not attend university. Hower, her younger brother, Friedrich, did learn science at school and shared his science textbooks with her. They seem to have talked and done experiments in their kitchen. They noticed that if you add even a very small amount of detergent to some water, it will have a major effect on the surface: a paper boat floating on the water, for example, will be propelled away from the detergent as it spreads out across the surface.
Surface tension is the tendency for the surface of a liquid to behave like a thin elastic sheet. Water, for example, likes to take up the least volume possible, so it will form a round raindrop. The molecules of water on its surface are exposed to water on one side and air on the other; they will cling to their fellow water molecules and are thus slightly pulled inwards. You can see a remarkable demonstration of this from the International Space Station, where gravity does not interfere with water. It also explains why some insects are able to walk on water: the surface doesn't want to "break".
Different liquids have different surface tensions, and if you add impurities to water, its surface tension changes. (The Royal Society of Chemistry has a suggested set of experiments on this if you want to try them.) Pockels was the first person to design equipment to measure this. She used items from her own home: a large trough to fill with water, and a small disk - in fact, a ceramic button - on a thread; the changing force it took to remove the button would measure the surface tension. The trough was divided into two sections by a bridge. If a drop of impurity was added on one side, it would spread out across the surface - but not on the far side. The bridge could then be used to compress or spread out the impurity. Today, the nearest equivalent of Pockels's apparatus is the Langmuir-Blodgett trough.
While Agnes juggled her DIY science with with her care duties, Friedrich went to university to study physics (and became a scientist himself) and presumably continued to send her books. It may have been him who alerted Agnes to the fact that professional scientists such as Lord Rayleigh were beginning to do experiments in the lab similar to her own. Agnes wrote a letter in German to Lord Rayleigh: "MY LORD,-Will you kindly excuse my venturing to trouble you with a German letter on a scientific subject?" He was so impressed that he had it translated into English and wrote a letter asking that it be published in Nature, which it was - but sadly after 126 years is still behind a paywall.
She wrote at the time that "For various reasons I am not in a position to publish my observations in scientific periodicals" but although she never received a position at any academic institution, she did indeed publish some papers later in life. One of her discoveries was that while adding detergent to water lowers the surface tension (this is how it works!), sugar increases it unless you bring the sugar to the surface! More importantly, other scientists who followed up her work learned about bilayers. These are composed of hydrophobic (water-hating) and hydrophilic (water-loving) compounds and that these often occur together in nature, the hydrophillic end will plunge into water while the hydrophobic end will try to bury itself in any other substance. This can cause mixing and lift off any dirt in the substance. Our own body cells are made of a phospholipid bilayer, which allows us to control how much water comes into and out of them. Langmuir and Blodgett, who used apparatus so similar to Pockels's, discovered that single water-surface monolayers (which you can create by sliding the bridge across to just the right amount) can be transferred to solids, and that these layers can be stacked on top of each other - which are major results for what is now called materials science.
Have you got a favourite historical DIY Scientist or citizen scientist to tell us about? Please let us know, or write your own post for our #CitSciStories: we'd love to hear from you.