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Lakeshore
An author of no particular popularity

Jay Lake
Date: 2007-09-11 18:35
Subject: [science] "Burning" water
Security: Public
Tags:links, science, tech
tharain asks if these stories about are real:

Radio frequencies help burn saltwater

PESWiki article.

I object strenuously to the phrase "burning water", and I don't see what the net energy budget here is. My teeny weeny knowlege of physics and chemistry says that must be one hell of a radio signal. kadath, dirkcjelli, any of you other tech head wants to comment?
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Patron Saint of Pessimism: Action Card Lab Gremlin
User: woodrunner
Date: 2007-09-12 02:14 (UTC)
Subject: (no subject)
Keyword:Action Card Lab Gremlin
In one analytical chemistry application, radiofrequency generators can strip electrons from gases and cause an electron cascade, which in turn becomes a plasma. The plasma itself is described as a plume which can have different gradients of temperature depending on where you point an infrared thermometer.

The gases used in the applications are typically noble gases, such as argon or neon (less frequently) and helium. I have heard of researchers experimenting with other gases such as nitrogen and oxygen, with varying successes in terms of analytical applications.

The radiofrequencies used for plasma generation by electron cascade are in the MHz range.

Liquids put through a plasma tend to douse it because of the heavy load (and solutions to be analyzed for elemental content are nebulized to a fine mist to avoid this issue), so I'm assuming the guy isn't lighting a plasma and then pouring saltwater through.

I'd assume that in order to apply the same principle to a liquid, one would need "one hell of a radio signal", as you said. Assuming that this is the case, the radiofrequency would strip an electron from the water molecule. I can see it destabilizing the molecule into OH- and H+, but there is a chock full of other elements in saltwater that, when separated into their atomic components, would have higher affinities for that errant hydrogen atom.

I don't see hydrogen alone "burning" as a result of radiofrequency generation application. You need to strip an electron from the gaseous state of the element in order to create a plasma, and H+ doesn't have any electrons to spare.

Maybe more learned minds than mine can clarify this, I'm all sorts of curious now.

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Jay Lake
User: jaylake
Date: 2007-09-12 04:02 (UTC)
Subject: (no subject)
Thanks! My fumbling intuition seems to have been essentially correct.
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Patron Saint of Pessimism: Action Card Lab Gremlin
User: woodrunner
Date: 2007-09-12 10:30 (UTC)
Subject: (no subject)
Keyword:Action Card Lab Gremlin
You're welcome! :)
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(no subject) - (Anonymous)
(no subject) - (Anonymous)
Jay Lake
User: jaylake
Date: 2007-09-12 04:02 (UTC)
Subject: Re: Oh sweet jesus, reading that wiki link made me stupider.
Thenk yew.
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Patron Saint of Pessimism: Action Card Lab Gremlin
User: woodrunner
Date: 2007-09-12 10:28 (UTC)
Subject: Re: Oh sweet jesus, reading that wiki link made me stupider.
Keyword:Action Card Lab Gremlin
I tried to read the wiki link but I didn't get past a couple of sentences, so I'm glad to hear I avoided losing a few neurons in the process!

If the plume is yellow-orange, then all he's burning is sodium, not hydrogen. Hydrogen burns clear, with no change to the plume colour.

If he's been talking to "scientists" who were "baffled", they certainly weren't quantum chemists either!

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(no subject) - (Anonymous)
Kevin Roche
User: kproche
Date: 2007-09-12 16:30 (UTC)
Subject: (no subject)
It may not be sodium combustion so much as the simple presence of excited sodium ions in the flame. 26 years ago I was doing an experiment as a summer intern where we were attempting FM laser spectroscopy of ionic species in flames, and we decided to look for sodium ions (by way of aspirating a NaCl/water solution into the flame).

We very quickly discovered that we didn't need the salt; our technique was so sensitive that it detected the sodium that distilled water leached out of the walls of Pyrex (which back then was sodium borosilicate glass).
We finally had to resort to an all Teflon (high density PTFE, technically) capped bottle and hose just to be able to take a sodium ion-free background spectrum.

This reminds me of all the improper calorimetry being done in the "cold fusion" experiments.


By the way, Jay, if you didn't see it in my LJ yesterday, our current "racetrack" memory project (and my boss) were featured in yesterday's New York Times. They even mention me by name :-)
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Patron Saint of Pessimism: Action Card Lab Gremlin
User: woodrunner
Date: 2007-09-12 21:01 (UTC)
Subject: (no subject)
Keyword:Action Card Lab Gremlin
I'm glad to hear I'm not the only one with issues with sodium in the blanks! Now I just have to convince the boss to spring for the $$$ calibrated volumetric flasks so that I can make untainted calibration solutions.

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Patron Saint of Pessimism: Action Card Lab Gremlin
User: woodrunner
Date: 2007-09-12 20:58 (UTC)
Subject: (no subject)
Keyword:Action Card Lab Gremlin
I'm not sure what the sodium combustion process is, though sodium by itself as a metal will burn in air. Strip the chloride from the salt, assume the sodium atom lumps with the other sodium lumps and becomes the metal, and exposed to air, it'll oxidize... um...

If he's burning saltwater, I don't think the yellow-orange color is a function of the plume temperature, since sodium emits an orange wavelength as it is ionized/excited. I see that when I analyze samples by ICP that have a high sodium content.

I can't believe Wiki posted the story...!!!!

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Kevin Roche
User: kproche
Date: 2007-09-12 21:30 (UTC)
Subject: (no subject)
Since he's dealing with salt water, the sodium is already in solution as dissociated sodium ions. If the process is nebulizing and heating the solution, you'll see sodium's ionic spectra.

Our sample excitation device in the laser experiment was just a lab gas burner (like a Bunsen burner) equipped with a fluid aspirator.
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Donald
User: tharain
Date: 2007-09-15 02:08 (UTC)
Subject: (no subject)
Thank you. =-) You certainly have the sources.
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