PSN-L Email List Message
Subject: Re: Modified sound card and datalogging and geophones
From: "Charles R. Patton" charles.r.patton@........
Date: Sun, 24 Jul 2005 15:56:24 -0700
No, no direct experience with this mechanism of maiming myself. Have
screwed up in other ways, but fortunately survived with only scars! I
agree that a balloon directly is probably hard to self charge and cause
problems due to Faraday cage effect and its high resistance somewhat
shielding the interior from a direct spark. However it is also easy for
me to imagine filling a few balloons, stuffing them into a trunk and
transporting somewhere. Balloons being what they are and most times
being sealed by tying off the necks, which doesn't always work so well,
leaking at a slow rate. Now the trunk is filling with stoimetric
acetylene/oxygen. Experimenter opens trunk, the trunk light switch
sparks, and I leave the train of events from there to your imagination.
I do not have the information for spark energy necessary to set off
but a quick Google search at;
"_Ease of ignition_: Acetylene is a very easy gas to ignite. In fact,
the energy from a static spark capable of igniting acetylene is lower
than for any other fuel gas except hydrogen. The ignition energy of
acetylene in air is approximately seventeen times lower than that of
methane. (Think coal mine explosions.) The static charge developed by
walking across a carpet floor on a dry day can be 1700 times greater
than that needed to ignite acetylene. When mixed with pure oxygen, the
ignition energy of acetylene is almost 100 times lower than it is in air."
This is not the description of a hard-to-ignite substance.
Add to this fact the information that basically acetylene will burn from
2.5% to 81% and explosively decompose at 100%. You have some pretty
potent stuff to get into trouble with. As much as I love fireworks,
this is something I would think twice about before using. Years ago,
somebody told me about filling a dry cleaning bag full of acetylene/O2.
I don't remember the particulars, but the impression stayed with me that
I didn't want to repeat his experiment. He was a long way away, and
still got knocked over.
Further searching at:
found this table quoted:
Chemical Minimum ignition energy
( mJ )
Methane 0.30 0.003
Propane 0.26 0.002
n-Hexane 0.29 0.006
Acetylene 0.017 0.0002
Ethylene 0.07 0.001
Benzene 0.22 -
Acetone 1.15 0.0024
Ammonia >1000 -
Diethyl ether 0.20 0.0013
Methanol 0.14 -
Hydrogen 0.017 0.0012
The above information comes from a US Dept of the Interior
Bureau of Mines Bulletin 680. " Investigation of Fire and
explosion Accidents in the Chemical, Mining, and Fuel-related
Industries - A Manual. by Joseph M. Kuchta.
Acetylene is shown to be six times more sensitive than H2/02 and the
most sensitive in the table above. . Interesting.
I find the discussion interesting and in no-way want to censor it. But
I have great respect for self responsibility, and I don't wish ill will
and bad results from lack of knowledge. I'm just trying to point out to
anyone thinking about playing with some of these ideas -- remember young
people read this list also -- that there are some important
considerations that I would at least like them to consider before
proceeding. I survived my experiments, but a couple could have had some
very serious results, and I continue to learn something new every day,
including these discussions.
>In a message dated 24/07/2005, charles.r.patton@........ writes:
>Earlier someone mentioned the idea of pre-filling some balloons with oxygen
>/ acetylene. DON'T. You have small bombs now that are extremely sensitive
>to ESD. Small spark, whole tamale goes off in your face, trunk, whatever.
>Spark so easy as most likely using plastic, rubber, etc, that is not ESD
>treated. Even in the open, you're looking for trouble.
> Is this advice the result of actual experiments trying to detonate C2H2
>/ O2 mixtures, or is it just general prudent advice without any experimental
>testing? Please send me the reference.
> We did some experiments trying to set off H2 / O2 mixtures many years
>ago and found that the mixture seemed much more difficult to ignite than we
>had expected. We were working both with gas mixtures and also with pastes of
>solid O2 in liquid H2, which could potentially give a very serious explosion.
>We were not able to ignite the mixtures with static charge found on a hair
>comb or by rubbing a balloon with fur. A high energy spark plug gave reliable
>ignition as did sparks from the an energetic 'tesla sources.
> Can you give a reference to look up for the enegry dischage which will
>produce ignition C2H2 and O2 mixtures pleae?
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