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sanity gone
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I've been working on this with my own twist.
The electrodes are both graphite enclosed by PVC tubes (I did some percise drilling into my makeshift reaction chamber.) The PVC pipes the two gasses
into a container with dH2O under UV lamp. I'm trying to think of a way to safely dispose excess HCL gas, but I'm thinking of running the
excess gas under water to form some amount of HCL. I don't know if this will work.
I wrote a quick equation on my TI-83 and it says 262g of NaCl would make a concentrated acid in 250ml of H2O, although I could of easily not done the
math right (I tend to make mistakes when doing speed stochiometry)
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Esplosivo
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| Quote: |
but I'm thinking of running the excess gas under water to form some amount of HCL.
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I know the amount of HCl is relatively small but be careful for suckback. Why not use the inverted funnel method. Excess gas will also bubble through
but the method prevents suckback.
Theory guides, experiment decides.
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Tacho
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UV light. I like that, thank you.
Does anybody know if borosilicate glass is somewhat transparent to short UV (germicide lamps)?
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Esplosivo
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Glass is somewhat 'impermeable' to UV but only to a small extent. UV has a high penetration power so 'thin' glass would not effect
the UV to any large extent.
If you know the reaction between any alkane with Cl2 you know it requires sunlight/UV. Well if the mixture is placed in a closed borosilicate glass
container proceeds normally.
Theory guides, experiment decides.
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axehandle
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Slightly OT: Are there UV <b>diodes</b> on the market? A glass one could be INSIDE the chamber given adequate cooling.
My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35
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t_Pyro
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Isn't the Blu-ray disc read using a UV laser? Then there has to be UV diodes in the market, although their power output might not be sufficient
for the current application...
Edit:
See these pages:
http://www.brightsurf.com/news/nov_03/SNL_news_111903.php
http://physicsweb.org/article/news/5/6/3
[Edited on 17-6-2004 by t_Pyro]
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axehandle
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It only has to be a very narrow confined beam to initiate the reaction in a point of the gas mix, then the reaction will self-propagate, right?
My PGP key, Fingerprint 5D96 E09E 365D 1867 2DF5 C2FE 4269 9C19 E079 CD35
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t_Pyro
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Yes, but depending on the rate of evolution of the Chlorine, the LED solution might, or might not be sufficient. It's still better than nothing,
though.
An alternative solution using Mercury vapour lamps:
http://www.safetyline.wa.gov.au/pagebin/pg000106.htm
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Tacho
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UV germicide lamps are very common and easy to buy. I have a couple from my eprom erasers. One is very large, like 30 or 40 cm (many eproms at once).
A glass tube along the lamp, wrapped with aluminum foil, will make, at least, pretty and tan molecules.
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sanity gone
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I don't know where to find the lamp, but the activation energy required in terms of light is 491.5nm.
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Esplosivo
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Are you sure the wavelength require to break the Cl-Cl is 491.5nm? If that is so the blue/violet visible light starts from 400nm. I see 491.5nm too
low as an activation energy for the rxn.
Theory guides, experiment decides.
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sanity gone
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From http://chemed.chem.purdue.edu/genchem/demosheets/10.7.html
| Quote: |
The enthalpy for the overall reaction is -184.6 kJ per two moles of HCl. However, the enthalpy for the initial step is 243.36 kJ per mole of Cl2.
This corresponds to the energy carried by photons with a wavelength of 491.5 nm This reaction is catalyzed by light toward the violet end of the
visible spectrum.
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Tacho
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| Quote: | Originally posted by sanity gone
I don't know where to find the lamp, but the activation energy required in terms of light is 491.5nm. |
UV range goes up to 400nm. So I guess the lamps I have are energetic enough (longer wavelenght, less energetic).
Edit: In fact, the reaction seems to be triggered by strong lights in general. Short wavelenghts are just to make it a reliable catalyst.
[Edited on 17-6-2004 by Tacho]
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Esplosivo
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Great! UV lamps will be therefore more than enough for the reaction to start. There are so many types of lamps which give UV light. There are many
types of 'bulbs' emitting UV near the visible light spectrum - check out the phosphorescent tubes used in discos for example (also used in
those thingies to attract and kill insects with an electrical shock through a grid, don't remeber what they are called)
Theory guides, experiment decides.
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Marvin
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Last I looked blu-ray was just a spec and semiconductor blue lasers with a decent (more than a few hours) lifespan had yet to be produced.
UV LEDs are available but rather expensive last I looked, 370nm ish and rather weak compaired to mercury tubes.
Important note for anyone using the voltage multiplier - If using mains power directly make sure the live wire is the lower one in Tacho's
circuit diagram, ie it is isolated by the first capacitor in the ladder.
Ideally the current to the cell would be enough that a tiny jet of gasses could be lit and the spark would just be backup. This would be in a small
chamber isolated by inert metal gauze for example, so in the event ignition failed totally unburned gas leaving the tiny burning chamber could not be
ignited later on (like a Davy lamp).
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Tacho
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Yes, Explosivo, UV does the trick!
I used a 15W, 43.5cm long, germicidal lamp. Part#G1578. It looks like a 20W fluorescent lamp but it’s not white, it’s transparent.
The reaction tube (about 50cm, soda-lime glass) and the lamp were wrapped in al foil, to improve light use and protect my eyes. I kept some distance
between lamp and tube, in case the tube explodes.
I run 2.5A through the cell for 45 minutes, passed the gases through the tube and the output seems to be only HCl (a test for Cl2 would be easy but
wasn’t done). The output seems to be irregular, in bursts. It passes over 20ml of water that becomes acidic.
Efficiency still seems to be lousy. It took more than 5ml (sorry, I stopped measuring at 5ml. I don’t have much time, you see. I have a life outside
the attic) of the acidic water to neutralize an alkaline solution that was neutralized by 0,2ml of 7% HCl (approximate numbers, please, don’t quote
me on that!).
Apparently it catalyses H2+O2 too, because there was condensation inside the tube, but it could be just mist from the cell.
Ooouuuww! You should see that setup working in the dark! Sci-fi scene! A picture of that will qualify me for a straightjacket! No less!
[Edited on 18-6-2004 by Tacho]
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Esplosivo
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Congratulations Tacho.
| Quote: |
Apparently it catalyses H2+O2 too, because there was condensation inside the tube, but it could be just mist from the cell.
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HCl sort of absorbs water from the air and dissolves in it. This condensation could be due to the HCl formed dissolving in water vapour in the air.
Theory guides, experiment decides.
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sanity gone
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BTW how basic is the NaOH soln?
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Tacho
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| Quote: | Originally posted by sanity gone
BTW how basic is the NaOH soln? |
I just dissolved some NaOH in water with a bit of phenolphtalein. Then I put equal volumes of this solution in two flasks and titrated with the two
HCl solutions.
The test was comparative between the two HCl solutions, one with a known concentration. I was looking for a proportion, any NaOH concentration would
work.
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Tacho
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That's the beast:
The aluminum foil is, of course, unwrapped. Notice the new H2 Cl2 generator, all made of soft plastic.
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sanity gone
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This is my idea for the generator:
Two towers connected by graphite salt bridge each contain a graphite electrode. Tubing is ran from the electrode from each tower into a reaction
chamber under UV light. Then the HCl gas is pumped into water using the inverted funnel method.
Here is a MSPAINT sketch of my idea:
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Esplosivo
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The graphite rod connecting the two 'towers' will not act as a salt bridge. As shown in the setup you have drawn there will be effectively
two cells, such that H2 and Cl2 are produced in both cells! Modifing the app by simply using a salt bridge instead of the graphite rod would do the
trick.
Theory guides, experiment decides.
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sanity gone
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oops... I didn't mean graphite salt bridge, I meant just salt bridge.
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Esplosivo
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The app is similar to Tacho's one but I think (at least it's my opinion) that there is a disadvantage using your apparatus. If I remeber
correctly HCl gas is hygroscopic right? Therefore it will absorb moisture from the air and dissolve in it. This will cause Hydrochloric acid to
collect in the container and not pass to the 'inverted-funnel - water' setup.
Btw, what are you intending to use as a power supply? A normal car-battery charger?
Theory guides, experiment decides.
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sanity gone
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For my power supply I have a AC inverter that will give me 12V DC with positive/negative terminals.
And using Tacho's setup probally will work better, but I'm curious to see how an alternative will work so I designed this yesterday.
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