The Capillary Action of Gasoline: Debunking the Gravity-based Siphon Theory

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Discussion Overview

The discussion revolves around the mechanisms behind siphoning liquids, specifically challenging the gravity-based siphon theory proposed by Dr. Stephen Hughes. Participants explore the roles of atmospheric pressure, capillary action, and hydrostatic pressure in the siphoning process, with a focus on gasoline and comparisons to juice boxes. The conversation includes theoretical considerations and personal observations.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant argues that the traditional definition of siphon based on atmospheric pressure is incorrect, suggesting that capillary action is the primary mechanism for siphoning gasoline.
  • Another participant counters that their experience with juice boxes indicates that pressure applied by fingers can influence the flow of liquid, implying that external pressure may play a significant role.
  • A different participant emphasizes that siphoning is influenced by the total difference in pressure, particularly hydrostatic pressure, rather than just differential air pressure.
  • Concerns are raised about the conditions under which juice boxes are filled, suggesting that positive pressure may affect the flow of liquid when a straw is inserted.
  • One participant proposes a hypothesis that ethanol, lacking hydrogen bonding capillary action, should not be siphonable, and expresses intent to test this hypothesis.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms of siphoning, with no consensus reached on the primary driving forces. The discussion remains unresolved regarding the roles of capillary action, atmospheric pressure, and hydrostatic pressure.

Contextual Notes

Participants note the dependence of their arguments on specific conditions, such as the density of liquids and the physical state of juice boxes. The discussion highlights the complexity of siphoning mechanisms without resolving the underlying assumptions.

  • #31


I think a 10m+ siphon would work, just very slowly. The top of the tube would be full of water vapor instead of liquid.

Suppose the source body has a surface elevation of 10 meters, the tube goes up 20 meters and then down 30 meters to the destination body. Water travels up 10 meters from the source as liquid, then vaporizes. It then travels up another 10 meters and down 20 as vapor. It condenses 10 meters above the destination body. The weight of 10m of liquid + 20m of vapor > 10m liquid + 10m vapor so the siphon keeps going.

May be tricky to get started.
 
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  • #32


SAFETY WARNING: Isopropyl Alcohol is toxic and must not be swallowed, nor inhaled, nor allowed contact with the eyes. I only got a little in my mouth, and spat it out and rinsed my mouth immediately.

***

I've just performed my experiment:

I used a store-bought 91% solution of isopropyl alcohol, a miniature (2 oz) martini glass as my donor tank, a miniature (2ox) gravy boat as my receptor tank, and a straw from a juice box for my hose (yes, I actually bought one just for this experiment).

Observations: having initiated flow via oral suction, flow continued as long as the mouth of the short end of the straw remained submerged beneath the surface of the liquid within the donor tank.

Measurements Taken: HEY, C'MON! I was working with tiny little glass vessels and a tiny little drinking straw that I could hardly hold in my hands. If want measurements, YOU take them!

Conclusions (keeping in mind my "Possible Sources of Error" discussion below):

1) Isopropyl alcohol is capable of being siphoned, thus suggesting that intermolecular hydrogen bonding is neither a significant nor a necessary force for the operation of a siphon system;

2) Isopropyl alcohol tastes terrible!

Possible Sources of Error:

!) The physical-chemical properties of ethyl alcohol and isopropyl alcohol may differ with regard to intermolecular attraction;

2) The 9% H2O content may have provided sufficient intermolecular hydrogen bonding to maintain the flow (although it wasn't a drip, but a good, strong flow).

***

Now I'll spend the rest of my life looking in vain for a laboratory that will have me!
 
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