Siphon in a Vacuum - Periodic Table of Videos
Why Physics Stack Exchange recommends it
Physics Stack Exchange users link it as the demonstration that a siphon can keep running in a vacuum, which they use to challenge the idea that atmospheric pressure drives a siphon.
Recommended by 1 people across 1 different months, 2013 to 2023.
What it is
A short Periodic Table of Videos piece in which chemists operate a siphon inside a vacuum chamber, using an ionic liquid that does not boil off under extreme low pressure. It accompanies a J. Chem. Educ. paper and is presented by the Periodic Videos team, filmed by Brady Haran.
Cited in 1 Wikipedia article, including Siphon.
What people said
Recommends Farcher · 2023-10 · Physics Stack Exchange · on “Weird fluid motion”
You have made a siphon and there are two two theories regarding as to how a siphon works. The first is that a pressure difference is created between the low pressure at the inlet due to liquid being sucked away from that region and the higher atmospheric pressure acting on the liquid surface which then pushes the liquid through the siphon. This theory was found not to be completely satisfactory when it was found that siphons work when the atmospheric pressure is very low, Can a Siphon Work In Vacuo? [this video] and also are able to raise the liquid to a greater distance than one would expect with the ambient atmospheric pressure, Negative Pressures and the First Water Siphon Taller than 10.33 Me
Cites N. Virgo · 2013-10 · Physics Stack Exchange · on “Do siphons really require air pressure to function?”
There is a video on YouTube [this video] of such an experiment. The corresponding paper is as follows: Can a Siphon Work In Vacuo? [LINK] Adrian L. Boatwright, Simon Puttick and Peter Licence. J. Chem. Educ., 2011, 88 (11), pp 1547–1550. DOI: 10.1021/ed2001818 After watching the video (but not reading the paper), my first thought was that the liquid in question has unusually strong intermolecular forces. If it didn't then it wouldn't be able to remain a liquid in such a strong vacuum. This must mean that this liquid can be held under a much higher degree of tension than something like water. This means that this experiment can't rule out the possibility that air pressure is important for the oper
Cites KingLogic · 2020-05 · Physics Stack Exchange · on “A contradiction from two reliable sources on the principle of how siphons work”
At 39:08 of Lecture 28 of 8.01x by Walter Lewin [LINK] , a water siphon would not work if the distance is over 10 meters due to the barometric pressure. However, this claim is seemingly refuted by Periodic Videos [this video] , where at 1:20 he said that the idea that atmospheric pressure pushes the liquid through the siphon is incorrect. At 4:57, he did the siphon experiment under vacuum with an ionic liquid and successfully operated the siphon. Is Walter Lewin's statement inaccurate, or is something else, such as viscosity, at play?
Cites red whisker · 2020-10 · Physics Stack Exchange · on “Effect of cohesion and tensile strength on the working of siphons”
My understanding of siphons is that air pressure is able to lift (because of lower pressure at the top of the siphon) the liquid up the shorter arm and then gravity pulls it down the longer arm. However, siphons can work in vacuum under special conditions. Wikipedia [LINK] states that the liquid siphons because of cohesion and tensile strength provided the liquid is pure, degassed and the surface (of the tube) is clean. For example, in this [this video] YouTube video, based on this paper [LINK] (not free), they use a fluid with strong intermolecular attractions. The pressure explanation tells that the diameter of the tubes is immaterial. However, it seems that if tension is the driving force behi