Sciencemadness Discussion Board

Useing a balloon for a oxyhydrogen explosive?

crazedguy - 27-1-2011 at 19:55

So I came up with the idea that you could put a balloon on a water bottle and capture the gases made by electrolysis.
The point of this would be to either tape a fuse to the balloon which would provide a sufficient bang, but I think it may be possible to get a better bang by strapping a small flash powder fire cracker to it.

So the question is would this provide better bang by setting it off with a small flash powder bomb would that get a full detonation, or would it be the same as just using a fuse?
I know that by adding 1 gram flash to set it off will be slightly louder but would it achieve full detonation. (1 gram-ish)

Would a balloon full of oxyhydrogen float?

Bert - 27-1-2011 at 20:20

Yes, it will go bang. No, it isn't a good idea. If you must try it, use remote electrical ignition NOT a hand lit fuse, and be aware that static electricity can easily ignite the contents unexpectdly during filling and handling.

crazedguy - 27-1-2011 at 20:26

Static is a good point I will spray the balloon with anti static spray, and use my wrist strap while I tie it.
And you didn't answer the question, will it go high order, a full detonation?

[Edited on 28-1-2011 by crazedguy]

holmes1880 - 27-1-2011 at 21:50

You're not detonating hydrogen with an FP firecracker. But you can burn off your face with it. From what I've seen, oxyacetyline is more powerful and equally dangerous.

Gases are the most volatile forms and static loves baloons. Put two and two together.

SB15 - 27-1-2011 at 22:02

Oxygen/Hydrogen will undergo DDT, but the runup distance at atmospheric pressure is typically larger than what a balloon would supply.

Flash powder ignition may work, but you'd be better off using an actual high explosive blasting cap to initiate detonation. I've used my DOP*/ETN compound caps to initiate oxygen/propane, oxygen/propylene, and oxygen/acetylene, with the adjacent peak pressure recording gauges reading much higher than the predicted adiabatic combustion pressures in all cases.

*Deadly Organic Peroxide, TCAP or HMTD. Replace with silver acetylide if possible.

[Edited on 1-28-2011 by SB15]

crazedguy - 27-1-2011 at 22:19

Well I just don't want to use a H.E. cap, but I figure flash ruptures its case above the speed out sound so it should be able to transfer a shock wave through the oxyhydrogen maybe.

DNA - 28-1-2011 at 00:29

Another problem is that hydrogen is a very small molecule, so it will just diffuse through the balloon, and there will be a invisible cloud of hydrogen OUTSIDE and AROUND the balloon.
So be very careful with this.

ScienceSquirrel - 28-1-2011 at 05:36

You are better off using propane. The balloon is easy to fill from a blowlamp and it can be ignited with a piece of string as a fuse. Stand well back as it produces a sizable fireball from even a small balloon.
Adding air or oxgen will make quite an explosion.
Have a look at YouTube for videos.

hissingnoise - 28-1-2011 at 05:49

Marking the valves of an oxyacetylene torch to give a neutral flame, filling a balloon or large plastic bag with the ensuing mixture and igniting it remotely would wake all the people unfortunate enough to be your neighbours . . .
What fun?


-=HeX=- - 28-1-2011 at 06:27

Perhaps foaming the gas mix in a polymeric bubble mix to form a 'foam' ala LEXFOAM could be interesting, IIRC nbk coined the idea. It would be fairly cool to fill a void with the shit then ignite it...

grndpndr - 28-1-2011 at 07:01

I had the same Idea OT(Hiss. neutral mix) using acetylene for obvious reasons
as a rifle target using tracers.Obviously the practice would have to be limited to winter around here but I dont think it illegal,after all binary explosives are sold for the same purposes but at exorbitant $.A good size party balloon makes a hell of a bang.Should one be unfortunate enough to be holding said balloon and it detonated your eardrums are at serious peril of being perforated.Maybe Kewl but sounds like fun to me:P

[Edited on 28-1-2011 by grndpndr]

The WiZard is In - 28-1-2011 at 07:04

Quote: Originally posted by crazedguy  
So I came up with the idea that you could put a balloon on a water bottle and capture the gases made by electrolysis.

Essays on Science and Society
Adam Hart-Davis
James Watt and the Lunaticks of Birmingham
Science 292 [5514] 55-56 6 April 2001

"The Luna Society* believed in argument and cooperation. They had long
discussions about why thunder rumbles and decided the best way to test their
various theories was by experiment. Boulton made a 5-foot-diameter balloon
from varnished paper, and they filled it with a terrifying mixture of air and
hydrogen ("inflammable air from iron"), They lit a fuse underneath, released the
balloon in to the night sky on a clam, clear evening and waited for the bang.
unfortunately, the fuse was rather long, and they all assumed it must have gone
out; so they to talk among themselves, when there was a colossal explosion, and
they all said, "There it goes!" and forgot to listen for the rumble! [James] Watt
was at home 3 miles away and wrote that the bang was "instantaneous and
lasted about one second." This seems self-contradictory, but in any case, the
experiment failed to produce a simple answer to the original question."

*The Luna Society started ca. 1765 was started by Erasmus Darwin (grandfather
of Charles D.), included among others; William Small teacher and mentor of
Thomas Jefferson, James Watt (who did not invent the steam engine), Joseph
Priestly, and potter Josiah Wedgwood, Darwin's other grandfather.



————————
"Watt's third lucky break came in the shape of the new boring machine invented
by ironmaster John "Iron-mad" Wilkinson. Wilkinson was a splendid
larger-than-life character who wanted to make everything from iron. ….. in a
corner of his office he kept his own iron coffin, which he proudly showed off to
visitors. (This caused some trouble when he died, for his wooden coffin turned
out to be too big to fit in the iron one; so they had to bury him temporarily in the
garden while they cast another iron coffin. Then they dug him up, put his wooden
coffin in the new iron one, and found it would not fit in the hole in the rock. So
again they buried him temporarily, blasted a bigger hole, dug him up,
successfully buried him, and placed a large iron obelisk on the grave.

Unfortunately, the house changed hands a few years later, and the new owners
did not like this great 20-ton iron pillar in front of their sitting-room window; so
poor Iron-mad was dug up yet again and buried for the fourth time at Lindale in
the Lake District.)"

grndpndr - 28-1-2011 at 07:24

'Lunatiks of Birmingham' seems appropriate.Cast Iron coffin! How many pallbearers?!LOL

The WiZard is In - 28-1-2011 at 10:20

Quote: Originally posted by grndpndr  
'Lunatiks of Birmingham' seems appropriate.Cast Iron coffin! How many pallbearers?!LOL


Buried in the Lake District.... a Lunatick... brings to mind
two poets.


djh
----
“The paradox of the fall of the Shah,” Mr. Milani says, “lies in the
strange reality that nearly all advocates of modernity formed an
alliance against the Shah and chose as their leader the biggest
foe of modernity.” The Iranians have already paid dearly for this
folly. What price the rest of the world will pay remains an
open question.

John Muravchik
Wall Street Journal 19I11
Review of : Abbas Milani - A Monarch Dethroned
Palgrave Mcmillian

crazedguy - 28-1-2011 at 10:27

Quote: Originally posted by hissingnoise  
Marking the valves of an oxyacetylene torch to give a neutral flame, filling a balloon or large plastic bag with the ensuing mixture and igniting it remotely would wake all the people unfortunate enough to be your neighbours . . .
What fun?


I live next to a welding shop, so access to oxy isn't a problem, but that is not the point.
The correct way to do that is to set it to a perfect flame and tap it on something so it goes out.
You all are missing the point will it become a full detonation by using a small flash bomb to set it off, and would it float.
Of course it would be easier to buy the materials but that is not the fun part.

SB15 - 28-1-2011 at 10:52

Quote: Originally posted by hissingnoise  
Marking the valves of an oxyacetylene torch to give a neutral flame, filling a balloon or large plastic bag with the ensuing mixture and igniting it remotely would wake all the people unfortunate enough to be your neighbours . . .
What fun?



It's much easier to use volume measurements to achieve a stoichiometric ratio of gas in the balloon. Let's see, for acetylene it would be...

2C<sub>2</sub>H<sub>2</sub> + 5O<sub>2</sub> -> 4CO<sub>2</sub> + 2H<sub>2</sub>O

5molO<sub>2</sub>/7mol*100% = 71.4% O<sub>2</sub>
2molC<sub>2</sub>H<sub>2</sub>/7mol*100% = 28.6% C<sub>2</sub>H<sub>2</sub>

So figure 70/30 for a decent approximation.

Assuming a large 20cm diameter spherical party balloon, that gives:

V<sub>total</sub> = 4/3*pi*r<sup>3</sup>
V<sub>total</sub> = 4/3*pi*(10cm)<sup>3</sup>
V<sub>total</sub> = 4.2*10<sup>3</sup>cm<sup>3</sup>

We would obviously add the acetylene first, as it is the smaller fraction, then add the oxygen to mix the oxidizer and fuel effectively. So, the radius of the balloon after adding the correct quantity of fuel would be:

r<sub>fuel</sub> = (3*(V*0.3)/4*pi)<sup>1/3</sup>
r<sub>fuel</sub> = (3*((4.2*10<sup>3</sup>cm<sup>3</sup>;)*0.3)/4*pi)<sup>1/3</sup>
r<sub>fuel</sub> = 6.7cm

So fill the balloon to d = (6.7*2) = 13.4cm with acetylene, then add oxygen until the diameter reaches 20cm. Very simple, and a hell of a lot easier than trying to snuff out a torch flame and fill the balloon with mixed gases.

EDIT:

Quote:
You all are missing the point will it become a full detonation by using a small flash bomb to set it off, and would it float.


Yes, it will float. At STP, the density of air is approximately 1.3g/L. The density of the stoichiometric oxygen/hydrogen mixture will be:

p = 2/3*(2.0g/molH<sub>2</sub>*22.4L/mol) + 1/3*(32.0g/molO<sub>2</sub>*22.4L/mol)
p = 0.54g/L

As for the second part of the question, no, you will not achieve a full detonation unless you use a HE initiator. Hydrogen/oxygen will transition to detonation on its own, possibly even in a volume as small as a balloon, but even with a FP device as the ignition source, the reaction will primarily consist of an accelerating deflagration. It doesn't do you much good if the flame front accelerates beyond the local speed of sound when 95% of the fuel mixture has already been consumed.

Gas explosions are not very simple.

[Edited on 1-28-2011 by SB15]

ScienceSquirrel - 28-1-2011 at 12:09

I have seen Dr Bunhead detonating balloons filled with a mixture of fuel gas and oxygen.
The balloons were strung together with Visco fuse to ignite them and they detonated quite loudly. I think if you get the mixture right there is very little difficulty in getting a good explosion.
Here is a link to Dr Bunhead's page, his show is worth seeing if you get the chance;

http://www.bunhead.com/index.htm

acetylene by its lonesome

The WiZard is In - 28-1-2011 at 12:48

MA Nettleton
Gaseous Detonations : Their Nature, Effects and Control
Chapman Hall 1987

p. 73

4.3 Gases and vapours which are detonable in the absence of an oxident

"Probably the most important detonable gases and vapours in
the context of amounts produced and transported are gaseous
acetylene...."

Table 4.1 Experimental data on detonation properties of
exothermically-decomposed vapours.

100% C2H2

Detonation velocity in tube of infinite diameter 1.92 km/s
Pressure to which D=infinity applies (Nm-sq) 8.1x10 5th
Pressure limit (Nm-sq.) appx. 1.5 x 10 5th*

*There is some evidence suggesting that the pressure limit may
be lower when powerful imitators are used. The corresponding
detonation velocity may also be lower.


djh
----
The Fate of the Kilo Weighs Heavily On the Minds of Metrologist
Jeanne Whalen
Wall Street Journal 28I11

During the tea break at the London meeting [British Royal Society], delegates
mused on the importance of accuracy. Duncan Burns, a 75-year-old chemistry
professor, recalled the time he confused centigrade with Fahrenheit while
cooking resins in the laboratory at his first job. “I started a bloody great fire!” He
said.

----
Reminds upon me of the airliner that had to make an emergency landing when it
ran out of fuel! The pilot though he had X-gallons of fuel. The aircraft had been
fueld with X-liters. The NASA probe that crash landed … one group of engineers
was planning landing speed in meters/second … the others feet/second.


crazedguy - 28-1-2011 at 13:44

Well I dont like primaries so I will probably try this soon but just with a fuse and then try with the flash powder, then compare and decide if its worth it.
But thanks for the info definitely.

ScienceSquirrel - 28-1-2011 at 17:04

Acetylene / oxygen is a good mix in the right proportions.
A big balloon filled with this will produce an ear cracking explosion.
No need for a detonator, a simple string fuse will do!

grndpndr - 28-1-2011 at 20:14

+1 Earsplitting! literally if to close. Marking the valves I would think be at least as accurate. Ive yet to see a balloon that was anything but vaguely spherical.KISS

@ Wizard,Just 2?

[Edited on 29-1-2011 by grndpndr]

[Edited on 29-1-2011 by grndpndr]

[Edited on 29-1-2011 by grndpndr]

SB15 - 28-1-2011 at 22:30

Quote: Originally posted by grndpndr  
KISS


What, you think a volume formula and a bit of intermediate algebra is anything but simple? Remember that the name of this site is Sciencemadness, and using a crude guess at flame stoichiometry to approximate valve positions is anything but scientific; it's caveman-esque at best.

If one is actually looking to properly experiment with detonating oxygen acetylene mixtures, they should make a decent effort to control variables in their tests. Volume as a function of radius is an acceptable method; using a fixed volume metering apparatus and Boyle's law is better. Marking the valves will get you your 1337 K3WL explosion, but it better satisfies the 'stupid' component of your acronym than the 'simple' part.

grndpndr - 29-1-2011 at 00:46

If you were working with a repeatable spereical shape all this would be relavent.Balloons are not a reliable means to measure volume or ratios by thier circumference since there not speres nor are they of a repeatable shape are they?!

So it stands to reason if you dont have a consistent shape how can you calculate volume by simply measuring circumference of an inconsistent shape then assuming volume equates to a sphere which a balloon is not?Its a built in inconsistency that throws the entire premise of kilter

Given those facts it seems a more reliable way to have a correct ratio of gases is by filling the balloon with a known mixture.The only really precise method I can think of to verify volume of an irregular shape is by displacement or actually measuring the amount of gas used in filling the balloon.

Finally, Theres really no need to be so thin skinned/hostile towards those with differeing opinions.If the acronym KISS upset you that would be your cross to bear.It wasnt addressed at you it was simply a generalization.If I can arrive at the same or better results by a simpler method Ill do so.If that offends your scientific sensibilities thats unfortunate for you.You are more than welcome to think of me as a caveman.Not unflattering at all given our ancestor's adaptability,capacity to survive in an infinetly hostile enviroment.

Back to the topic at hand as Im sure many of you know small disposable tanks of oxygen and mapp gas (methyacetylene/propadiene,C4H10) are available at any hardware store
worth the name and it might be a respectable substitute for acetylene although what the effect of the excess hydrogen would have I leave to the more learned among you.

Whether or not std propane torch fittings work on the 02 or MAPP gas I dont know but I would doubt thier compatibility w/propane torch's causing extra $ outlays.Still in the vien of fun
as a rifle target using tracers from .22lr to a high power mil caliber or even improvised homemade tracers for which there are volumes of info it still sounds FUN despite....:(


SB15 - 29-1-2011 at 10:27

Quote:
If you were working with a repeatable spereical [sic] shape all this would be relavent [sic].Balloons are not a reliable means to measure volume or ratios by thier [sic] circumference since there not speres [sic] nor are they of a repeatable shape are they?!


I happen to have some spherical party balloons lying around, so I inflated a few to a consistent diameter and measured the diameter along the x and y axis of each.

#1
X axis: 18.4cm
Y axis: 20.1cm
= 8.5% variation
#2
X axis: 19.7cm
Y axis: 22.3cm
= 11.7% variation
#3
X axis: 19.0cm
Y axis: 20.5cm
= 7.4% variation

In my world, that's called 'pretty flipping consistent and spherical'.

Quote:
So it stands to reason if you dont [sic] have a consistent shape how can you calculate volume by simply measuring circumference of an inconsistent shape then [sic] assuming volume equates to a sphere which a balloon is not?Its a built in inconsistency that throws the entire premise of [sic] kilter


Technically, the specific shape doesn't actually matter. As long as the volume scales as a known function of the radius, this type of methodology can be applied.

Balloons are sufficiently close to spherical to make the approximation of volume scaling as a cubic function of radius. Regardless of whether or not they are truly spheres, diameter measurements will be much more accurate than guessing at valve positions.

Quote:
Given those facts it seems a more reliable way to have a correct ratio of gases is by filling the balloon with a known mixture.


A known mixture? How can you possibly *know* the mixture is stoichiometric based only on observing flame characteristics? Aside from the obvious observation difficulties, the changes in ambient pressure at the torch tip when the flame is extinguished and a pressure vessel is being filled can have a very significant effect on the composition of the gas flow. This is uncertainty you can't control.

Quote:
The only really precise method I can think of to verify volume of an irregular shape is by displacement or actually measuring the amount of gas used in filling the balloon.


The 'proper' method involves trapping each gas at a known pressure in a vessel of measured volume, then using a valve to fill the balloon with each volume. Slightly adapted versions of Boyle's law and the Ideal Gas Law can be used to design and optimize this system, but as the explanation would be well over the heads of most 'experimenters' on this forum, I won't get into it unless someone specifically asks.

Quote:
Finally, Theres [sic] really no need to be so thin skinned/hostile towards those with differeing [sic] opinions.If the acronym KISS upset you that would be your cross to bear.It wasnt [sic] addressed at you it was simply a generalization.If I can arrive at the same or better results by a simpler method Ill do so.If that offends your scientific sensibilities thats [sic] unfortunate for you.You are more than welcome to think of me as a caveman.Not unflattering at all given our ancestor's adaptability,capacity to survive in an infinetly [sic] hostile enviroment [sic].


I'm not upset about anything. I'm simply stating that discussions of such poorly controlled and inconsistent methods as marking the valves on a torch have no place on a scientific forum.

Quote:
Back to the topic at hand as Im [sic] sure many of you know small disposable tanks of oxygen and mapp gas (methyacetylene [sic]/propadiene,C4H10) are available at any hardware store
worth the name and it might be a respectable substitute for acetylene although what the effect of the excess hydrogen would have I leave to the more learned among you.


Methyl acetylene and propadiene (C<sub>3</sub>H<sub>4</sub>, they are structural isomers) MAPP blends are no longer readily available in most areas of the world. They have been replaced by a similar product which is comprised of ~99.5% propylene (C<sub>3</sub>H<sub>6</sub>;). Not quite as energetic, but more so than propane.

Quote:
Whether or not std propane torch fittings work on the 02 or MAPP gas I dont know but I would doubt thier compatibility w/propane torch's causing extra $ outlays.


They are indeed compatible with propane torches and fittings. Propylene/oxygen would make a rather respectable balloon filling mixture, but it would be far less likely to DDT than either acetylene or hydrogen.

[Edited on 1-29-2011 by SB15]

"I though he was amply forewarned."

The WiZard is In - 29-1-2011 at 14:06

Safety&Hygiene News
October 1988.

I got the call right after I got back from church. Ed had gone in early on a Sunday
morning to work on developing a hydrogen sensor and got blown to smithereens.
He was working with a bootleg mixture of six percent hydrogen and twenty
percent oxygen. It's highly detonable, and an explosion was fairly predictable. "It
blew him to bits," recalls the safety manager for a division of an aerospace
company.

He was working on developing an improved way to detect criticality problems in a
nuclear reactor. He asked me a few weeks before how to handle the gas safely. He
should've been behind sandbag barricades, operating the valves remotely. I sent
him a letter, and pointed out that the mixture he wanted to use was illegal to
transport across state lines. He was a knowing participant.

I though he was amply forewarned. He was a graduate engineer. He knew the haz-
ards. According to his notes, he was metering hydrogen and oxygen into a very
small test chamber and getting variations he couldn't account for. He needed to
narrow the cause of the fluctuations, and he said he needed to get a calibrated gas
source. So he bootlegged it in.

The explosion cost about $125,000 in damages. It made a shambles of the shop. A
couple of cars were destroyed. And it caused some damage across the street. It
was pretty spectacular.

He had two grown children and a youngster. He was in his late 30's or early 40's. It
was interesting: he was sort of an aging flower child - this was back in the early
70's - and at his funeral they scattered rose petals over the water by Santa Barbara.
There were not enough of his ashes left.

His family ended up getting about a $1.2 million settlement. They sued the gas
supplier. It never even got to court.


djh
---
The average women would rather have
beauty than brains because the average
man can see better than he can think.

Anon.


ScienceSquirrel - 29-1-2011 at 14:56

The Science Squirrel guide to safe gas explosions;

1) Take a 5 -10 litre balloon and fill it with the stochiometric mixture of fuel gas and oxygen. Assume that the balloon is a perfect sphere and base your calculations on this. You can allow for quite a bit in the way of errors. Your mixture can be too rich in oxygen or fuel and it will still explode. Some fuel gases are more forgiving than others

2) Tape the full balloon to a support and attach a piece of thick string as a fuse. Do this on a windless and rain free night. Light the string and retreat to a safe distance, 25 yards / metres is more than enough.

3) Watch the flash and hear the bang. It is about like a 12 guage / bore on this scale but pretty harmless as there is very little blast wave and no debris.
It is an STP gas explosion, it will make a flash and a bang, it is not going to blow you to smithereens!

crazedguy - 30-1-2011 at 13:00

What would be a good household item to make the electrode out of, my plan is to stick something through a water bottle with the balloon on the end.
or what is a good metal to use that won't rust/ decompose

"For fools rush in where angles fear to tread."

The WiZard is In - 30-1-2011 at 14:08

Oxygen - acetylene

http://tinyurl.com/4mpskdw
http://wn.com/oxygen_acetylene_huge_bomb

Man charged after explosion in Oneonta welding class
http://www.wktv.com/news/local/47519762.html

>> "gagage bag" acetylene explosion <<
yields 4 880 Google hits.... have fun.

{I was looking for the news report of the garbage bag
full of acetylene going off in the back seat of someones
car while they were driving...!}


djh
---
The explosion removed the windows,
the door and most of the chimney.
It was the sort of thing you expected in
the Street of Alchemists. The neighbours
preferred explosions, which were at least
identifiable and soon over. They were better
than the smells, which crept up on you.

Terry Pratchett




ScienceSquirrel - 30-1-2011 at 15:45

Nobody should fill garbage bags or airbeds with fuel gas / oxygen or air mixtures and ignite them.
You will have tens or even hundreds of litres of gas and the explosion will be huge and could be dangerous and might be illegal.
If you live in a country district and go for five litres or so in a balloon, it will make a safe explosion that could be mistaken for a backfire. Legally it will probably fall into a grey area or may even be legal. In the UK small gas explosions in balloons are a mainstay of chemical demonstrations so I reckon they are legal.
Really it is a backfire but not from a car! :D
Do some research, plan out what you are going to do and stick to the plan.
If it goes wrong, give up the experiment and start again.
I have done a lot of dangerous chemistry and never had a serious accident but I started off handling safe chemicals and developed a good technique.
Do it on a small scale and make it bigger if you need to and rehearse things. You do not want to do your first gas explosion in front of an audience.

crazedguy - 30-1-2011 at 15:49

Still don't know a good metal for electrolysis, but had the idea that I could just put electrodes through a 2 litre bottle take most the air out start electrolysis and put an electronic ignition system on the cap.
With that system it could be at higher pressures than a balloon.
I have oxyacetylene cylinders at my house I might try those sometime.
Would aluminium or some screws or nails work well for electrodes?

grndpndr - 31-1-2011 at 05:48

Ill let your assertion that approx 10% variation in volume
"is pretty flippant consisent in your world" speak for itself.

"inconsistent methods have no place on a scientific forum"





If You have determined a repeatable ,simple method of filling a balloon or plastic bag with a stoichiometric gas mix using commonly available materials thats more accurate that a neutral flame and marked valves lets hear it!(then prove it)Then Ill be dazzled by your brilliance and baffled by your bullshit.Till then...

SB15 - 31-1-2011 at 07:23

Quote:
Ill let your assertion that approx 10% variation in volume
"is pretty flippant consisent [sic] in your world" speak for itself.

"inconsistent methods have no place on a scientific forum"


I'm sorry, but if this is your only response to my comments, and you still believe that marking the valves on a torch will get you even close to <10% experimental error, then you are clearly too stupid to be participating in this discussion. Move on.

Quote:
If You have determined a repeatable ,simple method of filling a balloon or plastic bag with a stoichiometric gas mix using commonly available materials thats [sic] more accurate that a neutral flame and marked valves lets hear it!(then prove it)Then Ill be dazzled by your brilliance and baffled by your bullshit.Till then...


It's not rocket science. 2 valves, a trapped volume of known value, a pressure gauge, and Boyle's law are all you need. If you can't figure it out from that description, you have no business playing around with such sensitive and powerful gas mixtures.

[Edited on 1-31-2011 by SB15]

crazedguy - 31-1-2011 at 09:30

Quote: Originally posted by SB15  
Quote:
Ill let your assertion that approx 10% variation in volume
"is pretty flippant consisent [sic] in your world" speak for itself.

"inconsistent methods have no place on a scientific forum"


I'm sorry, but if this is your only response to my comments, and you still believe that marking the valves on a torch will get you even close to <10% experimental error, then you are clearly too stupid to be participating in this discussion. Move on.

Quote:
If You have determined a repeatable ,simple method of filling a balloon or plastic bag with a stoichiometric gas mix using commonly available materials thats [sic] more accurate that a neutral flame and marked valves lets hear it!(then prove it)Then Ill be dazzled by your brilliance and baffled by your bullshit.Till then...


It's not rocket science. 2 valves, a trapped volume of known value, a pressure gauge, and Boyle's law are all you need. If you can't figure it out from that description, you have no business playing around with such sensitive and powerful gas mixtures.

[Edited on 1-31-2011 by SB15]


You have been on this forum for less than a month and have less than 20 post, maybe try to be a little more reasonable and not act like a troll.

SB15 - 31-1-2011 at 11:48

Quote: Originally posted by crazedguy  
You have been on this forum for less than a month and have less than 20 post, maybe try to be a little more reasonable and not act like a troll.


Are you one of those individuals who believes that post count and longevity on a forum determine one's level of knowledge?

Yeah, I've been here for a month. I'm also an engineering student with extensive experience in the field of gas explosions, and was a member of the E&W forum for 4 years before it shut down.

It just so happens that I know a thing or two about the topic of this thread, and am not subtle about conveying my knowledge of techniques that do and do not work effectively. I also expect the people who make and use energetic materials as a hobby to posses more knowledge of scientific methods than the average K3Wl who fills balloons with random gas mixtures in hopes of making a 'big boom'. If that's trolling to you, maybe you need to find a different forum to post on.

Before you question my knowledge of gas explosions, have a look at how I've applied them in the past.

The explosion blasted out the win dows of two homes

The WiZard is In - 31-1-2011 at 12:35

Clearwater Times .Tuesday July 6, 2004 .‎
St. Petersburg Times - Jul 6, 2004
LARGO — The explosion blasted out the windows of two homes. ...
at a neighborhood Fourth of July party mixed oxygen and
acetylene in a plastic garbage bag, ...

http://tinyurl.com/4ezyrua


Found it.

Strange-Looking Car Leads To Explosives Charges
Balloon Filled With Acetylene Bound For Super Bowl Party

http://www.thedenverchannel.co.../6790966/detail.html


I remember an explosion in a Manhattan, NY welding supply
store. Don't be knowing if it was caused by leaking acetylene
or propane or ??

The store fronted on 52nd St between 10th and 11th avenue,
the roll down steel front gate looked like it had been kicked by Paul
Bunion. The rear of the building facing 54st backed up on to a
small parking lot. One of my fellow employees had bought a new
car and he a two other coworker were looking at. They hadn't
gotten twenty feet away - back to work when the rear brick wall of
the welding store fell on his brand new car.

One store employee suffered a broken leg. After the accident
they stored all of their tanks outside.




crazedguy - 31-1-2011 at 12:49

This is probably my favourite F/A explosion, caused by leaking gas when the pressure dropped the operator just cranked the pressure up, the spark was cause when two trains full of children passing by each other caused sparks.
http://en.wikipedia.org/wiki/Ufa_train_disaster



Quote: Originally posted by SB15  
Quote: Originally posted by crazedguy  
You have been on this forum for less than a month and have less than 20 post, maybe try to be a little more reasonable and not act like a troll.


Are you one of those individuals who believes that post count and longevity on a forum determine one's level of knowledge?
[/url]


I really don't care what your prerequisites are trolling is trolling, I am not saying that I'm smarter than you because I have more post point is you don't just act like your better than every one else.
Ghandi-To think your better than one is to be worse than all.
You obviously don't like that someone would challenge your knowledge, maybe explain your points before getting angry and calling people names over the internet because that solves nothing.

ScienceSquirrel - 31-1-2011 at 15:17

Woohoo, you two big darlings must really fancy each other to get all hissy like this! :P

ScienceSquirrel - 31-1-2011 at 17:20

Quote: Originally posted by The WiZard is In  
Clearwater Times .Tuesday July 6, 2004 .‎
St. Petersburg Times - Jul 6, 2004
LARGO — The explosion blasted out the windows of two homes. ...
at a neighborhood Fourth of July party mixed oxygen and
acetylene in a plastic garbage bag, ...

http://tinyurl.com/4ezyrua


Found it.

Strange-Looking Car Leads To Explosives Charges
Balloon Filled With Acetylene Bound For Super Bowl Party

http://www.thedenverchannel.co.../6790966/detail.html


I remember an explosion in a Manhattan, NY welding supply
store. Don't be knowing if it was caused by leaking acetylene
or propane or ??

The store fronted on 52nd St between 10th and 11th avenue,
the roll down steel front gate looked like it had been kicked by Paul
Bunion. The rear of the building facing 54st backed up on to a
small parking lot. One of my fellow employees had bought a new
car and he a two other coworker were looking at. They hadn't
gotten twenty feet away - back to work when the rear brick wall of
the welding store fell on his brand new car.

One store employee suffered a broken leg. After the accident
they stored all of their tanks outside.





A garbage bag holds 70 litres in the UK. I would guess that a US garbage bag is a similar size.
No one is suggesting making gas explosions on this scale.
Keep it small, 1 -5 litres and do some research before the demo and it is safe.
There is a big difference between 7, 70 and 700 litres, scale is important in practical chemistry!

crazedguy - 31-1-2011 at 18:23

Well yeah common sense is a must when doing stupid things.

grndpndr - 1-2-2011 at 10:37

@ Wizard.. I believe I saw the explosion your referring to on hist
Tv.Traced to a engineering flaw ganging a couple dozen acetylene tanks to a manifold system.In any event It was spectacular.
As far as legallitys Im sure intent has a great deal to do with legality.Using a dangerous explosive gas mix device in a crowd is far different than as a target in a unpopulated western area of grasslands.

@ SB 15.. It might be helpful at this point to tone down the discussion.My opinion is that you have still not demonstrated a practical method of filling a supposedly sperical balloon let alone odd shaped containers.Every post contains requirements for more.More gauges more this that?You mention filling a container with a known volume.How have you evacuated the container to ensure you have a pure gas?Then the problem of moving that gas into the container w/o dilution etc.How do you propose to do that w/o pressurizing the container?From a practical standpoint I do not see how this is supposed to work.If that makes me as you have said stupid then draw the stupid man a picture of this device.A simple request.Even a description of how!

Versus the simplicity and built in accuracy of precision adjustable valves with scribe marks allowing the same ratio of gas every time with the aid of the constant pressure/volume requlators/high pressure tanks.A system engineered over decades to do just what we want. Deliver a known ratio of gas capable of filling any shape- size container w/o calculations resulting innacuracys.
Precision designed /manufactured to deliver the basics of successful welding, consistent pressure/volume.How is that so difficult to understand?Yes there are some subjective elements mainly the operators perc ception of a neutral flame but I very much doubt that varys among professional welders by 10%.As others have said it doesnt take a perfectly stoichiometric ratio to make an explosive gas composition.I still maintain despite my alleged stupidity my method is far more practical/repeatable than your paper dreams.
Unlike you I have done these things in actual practice safely and very effectively, not on a piece of paper using nonexistent hardware/ or actual experimentation. Paper and pen is fundamental but theres also a recognized place for empirical evidence/actual experimentation as the ultimate test as most engineers will attest and as daily life and engineering failures prove.

If you care to reply doing so in a gentelmanly manner might assist your argument greatly rather than using insulting language which doesnt speak highly of your personality or intelligence. Or perhaps you are a troll as has been suggested.
We shall see.

@ SB15,as I think you suggested a volume gauge would be more than helpful in conjunction with a regulated supply of gases.
One could fill the container with the calculated volume of each gas resulting in a more accurate mix regardless of the shape size of the container.Unfortunately this beingfb a HOBBYIST site
many here dont even have access to industrial gases let alone
oxyacetlene welding rigs/additional gauges.Calcium carbide/water..what are the resulting constituent gases there.The fewer variables the better ,thats what I see with the oxyacetylene welding rig.[Edited on 1-2-2011 by grndpndr]

[Edited on 1-2-2011 by grndpndr]

SB15 - 1-2-2011 at 12:06

Quote:
It might be helpful at this point to tone down the discussion.My opinion is that you have still not demonstrated a practical method of filling a supposedly sperical balloon let alone odd shaped containers.


Didn't you see the video I posted? It demonstrates rather effectively the precision of a volumetric gas meter. The projectile launcher demonstrated uses a valve that is normally calibrated to open at ~95% of the peak theoretical deflagration pressure of the gas mixture used, and the metering setup delivers very consistent operation at all pressure ranges, and with all fuel gas/oxidizer mixtures. Granted, that's a constant volume/variable pressure setup, but the method of measurement is the same as it would be here.

Quote:
Every post contains requirements for more.More gauges more this that?


Nope, I've been talking about the same thing from the beginning. The meter for each gas requires a trapped volume (2 valves is the easiest way to set this up) and a device for measuring the pressure in the trapped volume. It only becomes reasonably complicated when you're dealing with 3 or more gases at a time.

Quote:
You mention filling a container with a known volume.How have you evacuated the container to ensure you have a pure gas?


That'll only be an issue for the first few fills. Afterward, the atmosphere in the trapped volume will be comprised entirely of the gas from the supply tank, provided you keep the valves closed between fills.

Quote:
Then the problem of moving that gas into the container w/o dilution etc.How do you propose to do that w/o pressurizing the container?


You don't want to avoid pressurizing the container. The reading on the pressure gauge is how you determine the molar quantity of gas you're measuring.

Assuming the process is adiabatic, Boyle's law is used to calculate the pressure required in the gas meter, assuming we know its volume, as well as the volume of gas required at the ~0.6PSIG the balloon will contain.

P<sub>1</sub>V<sub>1</sub> = P<sub>2</sub>V<sub>2</sub>

Quote:
From a practical standpoint I do not see how this is supposed to work.If that makes me as you have said stupid then draw the stupid man a picture of this device.A simple request.Even a description of how!


Here's a crude 5 minute MS Paint rendering of what it would look like. Calculations would need to be done to account for the extra volume of the connecting fittings. I would also add a quick connect fitting to allow the metering setup to be disconnected from the rest of the setup, as the exterior of the gauges are susceptible to blast overpressure.

Nothing is to scale BTW.



Quote:
Versus the simplicity and built in accuracy of precision adjustable valves with scribe marks allowing the same ratio of gas every time with the aid of the constant pressure/volume requlators/high pressure tanks.A system engineered over decades to do just what we want. Deliver a known ratio of gas capable of filling any shape- size container w/o calculations resulting innacuracys.
Precision designed /manufactured to deliver the basics of successful welding, consistent pressure/volume.How is that so difficult to understand?Yes there are some subjective elements mainly the operators perc ception of a neutral flame but I very much doubt that varys among professional welders by 10%.


Again, welding setups are designed to supply a consistent supply of oxidizer and fuel when the gas is burning, and with zero pressure feedback into the system. You have provided nothing to suggest that stoichiometry is maintained when the flame is extinguished and backpressure is feeding into the torch head. Assuming this has no significant effect may not be wrong, but it's crude, unverified methodology. A shot in the dark, essentially.

Quote:
As others have said it doesnt take a perfectly stoichiometric ratio to make an explosive gas composition.


Certainly not. There are many ways to produce an explosion from fuel gases. Hell, filling a balloon with a random mixture of oxygen and propane/propylene/acetylene is very likely to produce a good bang. A K3Wl can also fill a steel pipe with black powder from crushed up model rocket engines and make one hell of a loud bang. Doesn't mean either method is worthy of scientific discussion.

Quote:
I still maintain despite my alleged stupidity my method is far more practical/repeatable than your paper dreams.


Well, that's where you'd be wrong.

Quote:
Unlike you I have done these things in actual practice safely and very effectively, not on a piece of paper using nonexistent hardware/ or actual experimentation. Paper and pen is fundamental but theres also a recognized place for empirical evidence/actual experimentation as the ultimate test as most engineers will attest and as daily life and engineering failures prove.


So... where did you get the idea that I've only done these things on paper? Since you obviously missed it, here's the video again:

http://www.youtube.com/watch?v=BhHvxfDg-uw

Paper dreams do not send alkaline D cells through multiple layers of 1/16" steel using only air/propane mixtures. I'm not just some number wielding theorist.

Quote:
Unfortunately this beingfb a HOBBYIST site
many here dont even have access to industrial gases let alone
oxyacetlene welding rigs/additional gauges.


Fortunately, my system can be adapted to ordinary Bernzomatic oxygen/propane/propylene tanks using fittings from any hardware store.

Quote:
Calcium carbide/water..what are the resulting constituent gases there.


Mostly acetylene, with a bit of hydrogen sulfide and hydrogen phosphide mixed in. Technical grade calcium carbide is pretty impure stuff, but the stoichiometry shouldn't be affected significant by the trace contaminates.

However, that does bring up one of the disadvantages of a volumetric metering system: You can't use acetylene. Why? Well, it has the potential to explosively decompose above 15PSIG or so, so it's not wise to pressurize it. Oxygen/propylene is what I would go with.

peach - 1-2-2011 at 12:26

Pay particular attention to the cylinder yards who have put effort into stopping gas explosions and what the results are when it unexpectedly gets out of control.

The second video is what I would consider the most interesting, as it shows a real world problem developing and, despite the authorities moving everyone a long way back, it's still not far enough. To put the weights into a US format, the cylinders weigh about as much as a person, yet are flying around like they're made of paper.

Acetylene is the favourite fuel gas of welders due to it releasing so much energy when it burns. It is also unstable under more than approximately 15psi of pressure.

That is thousand of dollars worth of gas going up. About the same amount as the laundry bill for anyone standing nearby when it started.

The last three videos show the results of mixing the gas with oxygen. And it is not something you should be attempting if you haven't been using cylinders for a good long while.

I also find it irresponsible to be making these things look so cool without noting the extreme danger involved, as these are things people can get or already have to hand, and are likely to try; using their dad's oxy/acetylene torch for example.

In the last video, for instance, it shows the snooker player running from the table as the fuse is burning.

In reality, the caravan likely wasn't even filled with the gas and the fuse probably wasn't even connected to it at that point. They have filmed him running, then filled the caravan with a hose, from a long way away, and set it off. Probably with a squibb so they don't have to go near the caravan again. I wouldn't be surprised if they also had some method of flushing the thing with air or checking if there's acetylene left in it, should it not go off and they need to go back to it. I'd add to that, they may have even stripped the caravan of the more substantial metal parts.

You can see pieces of the caravan flying past the snooker table. That is a dangerous misrepresentation of reality given the ease with which it can be repeated by kids.

<iframe sandbox title="YouTube video player" class="youtube-player" type="text/html" width="640" height="510" src="http://www.youtube.com/embed/fesgl5Cs5FY" frameborder="0" allowFullScreen></iframe>

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[Edited on 1-2-2011 by peach]

The WiZard is In - 1-2-2011 at 14:45

Quote: Originally posted by SB15  

Again, welding setups are designed to supply a consistent supply of oxidizer and fuel when the gas is burning, and with zero pressure feedback into the system. You have provided nothing to suggest that stoichiometry is maintained when the flame is extinguished and backpressure is feeding into the torch head. Assuming this has no significant effect may not be wrong, but it's crude, unverified methodology. A shot in the dark, essentially.



Ahhhh.... with my cutting torch the acetylene pressure is 15+ psig
and the O2 even higher. You would need a really tough balloon to
get back pressure. Just adjust your torch for a neutral flame, stick
it into a bucket of water to extinguish - sign will - fill bag(s).

Want I want is a way to fill a bag with my Plasma torch!!!
Bet they could do it on the Enterprise.



djh
----
…Though the nominative diarrhea of the solar system may
have gone a little far, a well-chosen name is both
picturesque and memorable. Perhaps, therefore, it is time
to change the convention and give such a name to an
extrasolar planet. And an ideal candidate [Kepler-10b] has
just turned up—one that matches one of astronomy’s own
myths: the legendary, non-existent planet Vulcan.

…smallest extrasolar planet yet discovered. Its diameter is a
mere 1.4 times that of Earth, though it weighs 4.6 terrestrial
masses.

…its high mass probable means it is made of iron, an
appropriate material for a planet named after a divine
smith.

The Economist
15i11


peach - 1-2-2011 at 16:20

I was just watching that second video again and noticed that at 0:34, there are plumes of thick black smoke pouring out of the cars parked in front of the yard. And it looks like it's coming from the windows of the cars.

The insides of the cars are on fire, yet there is a distinct lack of things on fire or broken around them.

INSURANCE JOB!

---------

Wizard, you are a strange and amusing man, as I have likely said before. ;)

To put a rest to the oxy/acetylene torch debacle, one could simply try filling balloons with the torch out and then light the torch to see how the mix is combusting. Welders will look for a perfect mix based on the configuration of the cones and also how the flame behaves when put against something.

One method I've heard of guys using is to simply set the flame to rich to begin with, wave it over some metal, to deposit carbon, then raise the O2 content until it will burn off the carbon and back it down a little.

The are a number of variations on that, based on whether or not it will produce reducing or oxidizing results when something is heated in the flame.

Alternatively, watch the gauges as you add the balloon for an increase in the pressure the second stage reads. Or fill a none elastic container and then push the gas into the balloon.

Short of hooking your source or generator up to a gas chromatograph, you're not getting much better.

With acetylene being so unstable under pressure, you are likely going to get more exciting results from treating it to the loving care of a high pressure shock wave. Precisely how it behaves, and how filling balloons affects the back pressure, I must admit, has never crossed my mind as a particularly important issue as I get my card out to pay for another cylinder of the two.

When a roughly ideal mix will do the things demonstrated in the video above, I fail to see why a number of you are so concerned over the remaining few percent.

I'm not even sure why you'd really want to be doing that in the first place.

If you want to make a loud bang or blow something up, there are vastly superior alternatives. You'll never match the energy density of a solid explosive using these gas mixes. And why do you want to blow something up? Unless you're mining, I don't see much use to that. The irony being, they use fairly simple stuff for blasting.

So... I don't get it.

[Edited on 2-2-2011 by peach]

crazedguy - 1-2-2011 at 21:39

Its called a regulator for a reason.

Alright to my question that has yet to be answered,
what would make a good anode or cathode or both.
From these household metals or say one that I may have forgot.
copper, zinc, lead, aluminum, stainless, brass, tin, pot metals
so which would be best electrodes?
Thanks in advance

grndpndr - 1-2-2011 at 23:10

Im sorry best electrodes for producing what (gas)?I missed that.
And a few other points.:D

FWIW i thought the discussion after advising we(SB/Myself) tone it down a bit far more productive.I think everyone had good points particularly safety.I know these things are very dangerous Im only proposing a 1-2 liter balloon size as a target.Still very unpleasant to have detonate next to you quite possibly perforating an eardrum/causing burns if close enough.
Similar to a primary in many ways except I dont think the gas mix will vaporize a couple fingers/hand.Still NOT to be taken lightly and not yet something ive tried but seriously considered.
If you have looked at the cost of the commercial binary tgts you might understand my interest.

In retrospect likely a bad Idea.

In a perfect world w/adequate funds a system could be designed
that operated remotely OT fitting the balloons to nipples and filling them with the appropriate gas mix.Of course someone would shoot a hole in a gas line w/o steel plate protection:(

Many of you seen test videos of high pressure cylinder penetrate a concrete block wall w/o detonation deflagration but By gas pressure alone the heavy cylinders are launched at amazing velocity/kinetic energy.If ignited a RP(Gas)C!

ScienceSquirrel - 2-2-2011 at 04:52

I have filled balloons using cylinders; just slip it over the nipple, part fill the balloon with hydrogen, pinch the neck and slip it off the nipple, slip on to the second nipple and add a shot of oxygen. Then slip it off and tie the neck.
Optimum ratio is somewhere around 2:1 hydrogen to oxygen but as anyone who has popped hydrogen in a test tube will know it is not critical.
You can fill a balloon from a welder as well. Just slip it over the end and add some acetylene, then put a shot of oxygen in, slip it off and tie the neck.
Ratios are not critical in gas explosions, really you can judge it by eye with a bit of experience.
As long as you stick to balloons and use a modicum of care and common sense thay are noisy but very safe.
If you start filling up garbage bags, plastic or glass bottles or caravans :(
You are going to be one sorry maimed or even dead little bunny!

crazedguy - 2-2-2011 at 09:06

The gas I want to produce is hydrogen and oxygen by electrolysis of water.

ScienceSquirrel - 2-2-2011 at 09:46

Hydrogen diffuses through rubber quite fast.
I think you will find that it will diffuse out at such a rate that you will end up with a balloon filled mostly with oxygen, unless you put a lot of current in electrolysis is quite slow.
Why not do the logical thing and use sodium hydroxide and aluminium or such like?

grndpndr - 2-2-2011 at 18:19

Zinc/HCI reaction?
Zinc from an alkaline battery casing/acid from Hardware.
Used this to fill balloons as lighter than air as a boy.Hindenburg
minus the aluminized airplane dope covering :(

Twospoons - 2-2-2011 at 18:35

I have done this with a plastic shopping bag. Electrolyser made using stainless plates - four cell, driven at 20A, NaOH electrolyte. Took about 5 minutes to fill the bag. I'd estimate around 2 to 3 litres of gas. Goes with one hell of a bang. Ear protection is essential. Video on Youtube - posted by 'Grogyan'.

My electrolyser could sustain a hydrogen flame on the end of a 1" pipe (just). So a decent flow is possible if you have enough juju.

grndpndr - 2-2-2011 at 18:51

Sure,SS kitchen flatware.

peach - 4-2-2011 at 11:53

Quote: Originally posted by crazedguy  
The gas I want to produce is hydrogen and oxygen by electrolysis of water.


This is demonstrated in GCSE (16 y/o) level chemistry in the UK using a Hofmann Voltameter <----- This is August Wilhelm von Hofmann from the 19th Century, not Albert (the LSD guy) from the 20th.

The apparatus is simply two burettes standing upside down. There is a tiny platinum electrode in what would normally be the tops of the burettes, but that are now the bottoms (other electrodes can be used, and you can also buy short lengths of platinum wire or mesh cheaper than you'd think; it only has to be a tiny piece, not a $3k engagement ring).

It's filled with distilled water, which won't conduct on it's own. A tiny amount of acid is added to make it conduct. The water splits and you get hydrogen in one burette and oxygen in the other.

The demonstration uses the Hofmann apparatus, with the two marked burettes, so the teacher can show very graphically, and with measurements from the burettes, that there is twice as much gas in one than in the other, as evidence that one is filling with hydrogen and the other with oxygen as a result of the H2O splitting.

Samples of the gases will then be taken by sticking a test tube over the top, opening the tap to collect some, and trying to ignite the result in the test tubes.

One will do nothing, but will reignite a blown out splint. The other will produce the infamous 'squeaky pop', but not relight the blown out splint.

This is an excellent method of demonstrating it because it shows the results in different formats. Some people learn by tactile, visual results, yet are poor at the theory, others are incapable of visualising something but are much stronger with numbers. Combining the two universally gives better results. Having an engineer who can both use SolidWorks models, but appreciates the finer details of how something is going to behave in the complex world of reality. Those perfect combinations don't exist, so engineering teams are used instead, and meeting rooms full of biscuits, tea and whiteboards; and the project leader can then include the word 'synergy' in their reports. :P The same is true of pretty much all science projects; e.g. google data mining / this forum.



The electrolysis method is scaled up in Brown's gas (oxyhydrogen) generators.

These are more commonly used by jewellers, who want a very clean flame and to be able to simply fill the thing with water and switch it on and off to get the gas on demand. Rather than having big, dangerous, expensive cylinders hanging around their workshop. Jewellers tend to use very small torches, because the rings and necklaces are so tiny. Some of the torches actually use syringe blades as the nozzles, to get a tiny, tiny, invisible flame. The generators for those aren't much bigger than a lunch box and can go on the desk.

They come on a number of sizes and numerous different models. RioGrande is a very famous, and huge, supplier of the jewellery industry. They have some of the generators in their catalogue, along with a billion other things related to making shiny, expensive stuff.

People who work with materials that need to be extremely pure like hydrogen fuelled flames, as there is no carbon involved, which will embrittle some metals, make jewellery look messy and weaken some glass work.

QuickFit produce some of the best lab glass available. I have spoken with them a few times and have a hand written note from them beside me now, along with a free wash bottle and some details of how they produce the glass. They use natural gas and oxygen torches, and natural gas annealing ovens.

There are generators big enough to run a big welding torch. However, I have not once seen a gas welder actually using one (who wasn't trying to sell it). There is a video knocking around of a guy demonstrating larger scale brazing with one, but he makes a somewhat odd claim about the flame "adjusting it's own temperature" depending on what it's hitting, to the extent that he implies (if I remember correctly) that it wouldn't burn your skin if pointed directly at it (which he doesn't do). What he may be seeing is that the generator can't produce enough of the gas to heat large work pieces, so they are cooler than the flame temperature alone. This is a common mistake in electronics soldering as well, that you should use a low wattage iron for sensitive work. In reality, that means it takes longer to heat the part to the soldering temperature and the components end up roasting hot as you wait; and the heat conducts from the lead to the insides.

Gas welding and cutting is rarely used now when it's not heating something BIG. For example, gas cutting torches can cut metal over a foot thick. There are no plasma cutters or lasers available that can compete with that. Thermal (oxygen) lances can cut metal feet thick, and can also do cement based materials and clays.

Gas torches are still common around heavy industry, like shipbuilding. As they require no electricity or special optics, they are also used for rescue work and in remote locations where a plug socket isn't available. Thermal lances are used for heavy demolition and are sometimes used to open the plugs in iron foundries. They burn colder than acetylene, and don't produce a true flame, but don't rely on fuel evaporating or boiling out of cylinders, so they can have huge BTU ratings.

A side effect of cutting things that thick with gas is that the torches rip through cylinders. It is easier, and cheaper, to buy the cylinders rather than start generating the Brown's gas on demand.

As an example of the difference in power between electric (plasma / arc) and gas methods, ESAB will sell you a gas torch that can output around 80 to 90kW of heat, with a normal mains ring managing around 2 to 3kW before you run it into the Brown's gas generator and subsequently suffer losses. 80 to 90kW is three times what the grid fuse on my house can manage, ignoring all the internal wiring and breakers.

Acetylene torches burn at 3300C, 700C hotter than hydrogen torches. This means the work piece heats up a lot quicker.

There are only two higher temperature fuels known. Cyanogen at 4525C and Dicyanoacetylene 4990C. They produce such hot flames due to the massive amount of energy stored in the Carbon to Nitrogen triple bonds.

Both of them are highly toxic, entirely ruling them out in any realistic production environment.

Other gases used include MAPP and Propylene. Both burn colder than acetylene, but have some advantages in terms of handling and cost.

Plumbers use MAPP quite often, as it is burns hotter (warming the copper to it's soldering point quicker) than propane but can be bottled in little disposable cylinders. Acetylene can not. MAPP is also more expensive than propane, meaning you need to be used to working quickly and cleanly not to end up wasting money using it in the first place; e.g. not leaving the torch light whilst you do something else. MAPP smells like acetylene, but not quite as nice. :D

For disposable cylinders, as you'd get from Bernzomatic, oxygen comes in reds, propane in blues, MAPP in yellows. The gas is universally more expensive, quite a lot more, than it is to buy in refillable cylinders.

A number of people have built their own Brown's gas generators. You can find them by googling things like "DIY Brown's gas".

Reacting aluminium kitchen foil with concentrated NaOH or KOH will produce very large volumes of hydrogen very quickly.

I can envisage people trying to fill solid walled objects with acetylene over 15psi, and having it go off in their face. Oxygen enriched atmospheres will allow things to combust at massively reduced spark energies. Oil can combust INSIDE regulators and hoses when high pressure oxygen is added. Welders have even caught fire dusting their greasy overalls off with the oxygen from their torch. In the same way, pressurising a mixture of fuel gas and oxygen, by blowing it into none elastic container, is a bad, bad, bad idea. As another for instance, if you fill it cold, and then set it outside and get ready to do something, the heat from the sun hitting it could be enough raise the pressure and set it off.

The simplest method to get the largest bang realistically possible from a gas mixture is acetylene mixed with oxygen, into a balloon.

[Edited on 4-2-2011 by peach]

gnitseretni - 4-2-2011 at 12:19

I remember when researching HHO cells that you could get a flame using hydrogen that was hotter than an acetylene/oxygen flame. I forgot the name. I don't mean hydrogen/oxygen. They passed the hydrogen through an arc, which would rip apart the molecule or something, and on the other side of the arc it would recombine and it is this recombining of the molecules that generates tons of heat.

EDIT: it's called "Atomic hydrogen welding" ;)

[Edited on 4-2-2011 by gnitseretni]

peach - 4-2-2011 at 12:25

Atomic hydrogen welding

That's not combustion welding, it's more akin to an arc method.

For instance, some welders will use MAG welding, metal active gas, wherein some of the gas mix is oxygen or CO2, which will react in the arc to increase the heat, but also lower the purity of the work.

It is going to be impossible for someone who is still working on basic electrolysis to deal with atomic hydrogen, let alone bottle it. Since atomic hydrogen tends to recombine to H2 rather quickly. This is also similar to free radical experiments, wherein the radicals will recombine so rapidly the containers will pop as the radicals react.

We were shown a demonstration of this in A-Level organics. The teacher placed a transparent film canister on the desk and proceeded to run a free radical polymerisation by illuminating the canister with a bright lamp. The top of the canister quickly went airborne.

There are also plasma welders, which are a blend between a plasma cutter and a TIG set. Thermal Arc sell them.

Plasma cutters work around 20 to 30 thousand C. But, in terms of hot stuff, the JET experiment here in the UK has repeatedly produced stable plasmas well over 100 million degrees Celsius which will, of coarse, melt EVERYTHING on the periodic table; with the core of the sun being a mere 15 million.

CERN's Large Hadron Collider has managed beam lines with proton energies that correspond to a temperature of about 40,000 trillion Kelvin. They actually have two, and point them end to end into each other, for double the effect on collision and have gone up to 6 milllion, trillion kelvin for a lead nucleus.

The LHC is the highest energy particle accelerator on earth.

[Edited on 4-2-2011 by peach]

The WiZard is In - 4-2-2011 at 14:20

Quote: Originally posted by peach  


The LHC is the highest energy particle accelerator on earth.
[Edited on 4-2-2011 by peach]


Actually. For a lot less money I have found that by sucking
cement dust through the plastic hose on my shop vac I can
generate voltages high enough to create the elusive Higg's Boson.
I am storing them as generated in a Bose-Einstein Condensate in the
back of my freezer. Couple of dozen more and a Nobel Prize
is mine for the asking.


djh
----
Do you believe that the sciences would ever had
arisen and became great if there had not beforehand
been magicians, alchemists, astrologers and WiZards,
who thirsted and hungered after abscondite and
forbidden powers?

Friedrich Nietzsche
Die fröhliche Wissenschaft, IV, 1886

crazedguy - 4-2-2011 at 15:07

Quote: Originally posted by peach  


There are also plasma welders, which are a blend between a plasma cutter and a TIG set. Thermal Arc sell them.
[Edited on 4-2-2011 by peach]

I'm guessing your just talking about the sets that combine both into the case, and just use some of the same innards like the transformer and such?

Quote: Originally posted by The WiZard is In  
Quote: Originally posted by peach  


The LHC is the highest energy particle accelerator on earth.
[Edited on 4-2-2011 by peach]


Actually. For a lot less money I have found that by sucking
cement dust through the plastic hose on my shop vac I can
generate voltages high enough to create the elusive Higg's Boson.
I am storing them as generated in a Bose-Einstein Condensate in the
back of my freezer. Couple of dozen more and a Nobel Prize
is mine for the asking.

Hahahaha are you going to be the first nobel prize winner from this site?

peach - 4-2-2011 at 16:02

Quote:
I'm guessing your just talking about the sets that combine both into the case, and just use some of the same innards like the transformer and such?


Nope, they're designed to weld using a plasma jet, as opposed to cut or use an arc directly (as GTAW / TIG does).

Here's a description of the process

Last time I checked, Thermal Arc were the only big name company making plasma welders. I have owned a high end TIG set from both Thermal Arc and ESAB, and used other well known brands, and Thermal Arc is in the same band of quality; the TA one was a 400 amp DC set (I think that's been discontinued), and the ESAB was the newer CaddyTig 2200i TA34 AC/DC.

You could probably use a DC welding set as a power supply for electrolysis, if you've got one handy; as well as other bits of electrochemistry, like plating.

Thermal Arc's site

[Edited on 5-2-2011 by peach]

watson.fawkes - 4-2-2011 at 17:36

Quote: Originally posted by peach  
Atomic hydrogen welding

That's not combustion welding, it's more akin to an arc method.
It's combustion, all right, or at least chemical recombination with oxygen, which is more-or-less the same thing. The way to think of it is that the arc is a point-of-use atomic hydrogen generator, through inefficient brute dissociation of H2. So you're actual burning 2 H + O2 rather than H2 + O2. Admittedly it looks like an arc, but the arc does not directly heat the weldment. The energy from the arc is transferred into the system according to the enthalpy of the reaction 2 H --> H2, released in the combustion process, leading to the higher flame temperature.

peach - 4-2-2011 at 17:59

Quote: Originally posted by watson.fawkes  
So you're actual burning 2 H + O2 rather than H2 + O2.


As I understand it, oxygen isn't part of the equation. The heat comes from the atomic hydrogen recombining to H2.

crazedguy - 4-2-2011 at 20:48

I know quite a bit about welding but have never heard of paw welding actually, I could try using my welder for electrolysis, but its a mig and for some reason that seems like it would be hard on the machine even though its doing what its suppose to completing a circuit that is.
Two things I will probably try either using a power supply for a computer, or something with propane because I know there is an oxyacetylene set around house or just put propane in a balloon and fill it up with air.

peach - 4-2-2011 at 21:28

If the welder has a current limit built into it (and it should do, given the likely hood of it happening), it should be able to withstand being shorted.

MIG welders are constant voltage supplies, whereas TIG are constant current.

The newer generations of computer processors use absolutely staggering amounts of current. It's amazing when you think about it, that they contain such super precise, microscopic, delicate elements, yet have what is not far off a welder attached to them. They are all powered by switch mode supplies. Switch modes are incredible compared to linear supplies, in terms of their space, weight and power saving. Linear supplies are the weapon of choice for extremely precise and quiet output. Walt Jung is famous for designing a linear regulator that produces less noise in it's output than a battery - the so called 'Super Regulator', favoured by audiophiles, and much discussed at diyAudio.

Switch mode supplies also require someone who has a high level of ability with electronics to design them to take a universal input, to regulate under all conditions, feature low noise in the output and emit little RF noise. This makes small production runs of them expensive, particularly if the output doesn't adhere to one of the standards used with semiconductors (for which there are premade controllers and layouts). Since computer PSU's are churned out by the million and go obsolete quickly, you can find them for next to nothing, or in bins.

The way they are built is far more technically complex than a linear regulator, making it less of a simple task to regulate the output voltage and current. Whether or not that's an issue in your experiment is another thing. Most bits of chemistry aren't bothered by a bit of electrical noise from a switch mode supply, and you can dump voltage or limit current using brute force resistance if need be; not particularly pretty or compact, but effective.

As MIG welders are relatively low voltage devices, it won't take a lot of resistance in their way to reduce the current. But the resistor will get hot. I have seen people using some very unique methods of controlling when building DIY plasma cutters.

The amount of current flowing will also depend on how much acid you use in the water. You could simply start with pure water, and add acid until you're happy with the current and rate of evolution.

Since I was on my way down to recharge my cup of coffee, I thought I'd take a photo of some linear supplies I have. These are rated at 6Vdc and 30amps each. Something that should be immediately apparent is that they are big compared to a computer PSU (they're about a sack of cement in weight each), and it's not due to them using older technology, but an inherent side effect of how they regulate the output;



Because the supplies filter mains frequency electricity, they need very large capacitors


SM power supplies use very high frequencies, and the magnetic field from an inductor is proportional to the frequency of the current through it, so they can use tiny magnetics. These mains frequency ones, however, have to use big lumps of iron in the transformer. The rest of the supply is made up from pass transistors mounted to heat sinks. The transistors are functioning like variable resistors, and simply dump unwanted voltage across themselves. This makes them get very hot. Even if you're not bothered about the wasted electricity, you need to be bothered about the heat. Without the big heat sinks, the transistors would cook themselves almost instantly. Switch mode supplies don't 'dump' unwanted voltage or current, they generate it on demand. There was a big boom in welding when inverters, which are switch mode, came out, and you could suddenly have really high current supplies in something you could actually move without a crane. The fancy ones from ESAB, Lincoln, Miller and Thermal Arc with all the digital controls on the front are a result of someone putting a lot of effort into designing the switch mode supply. It is basically a mini power station, rebuilding the power and allowing you to shape into different waveforms, currents, voltages, frequencies, pulse widths, durations and all the other colours of the rainbow - they're high output waveform generations more than power supplies, in my opinion


[Edited on 5-2-2011 by peach]

crazedguy - 5-2-2011 at 13:40

Those are pretty cool power supplies, I don't think ill use my welder for a power source its cold out side and the welder is in the garage and don't want to set it up inside.
Not sure how I will use a computer power supply to make it work with all those leads that come off of a psu but ill figure something out.
Wish I had a tig welder, used to be really good at doing Al when I had welding class, I used to think I wanted to be a welder.
Never could convince my dad to buy a tig to fix the boat.

peach - 5-2-2011 at 18:12

There are endless guides about wiring computer PSU's up to use them as fixed voltage supplies, so I won't explain it here. Google for 'lab (or bench or DIY) supply computer PSU'. It's as complex as gather the wiring spools together into a group and finding the one the PSU uses as a 'wake up' signal when the button is pushed on the front.

AC TIG sets certainly are appealing but, having bought one, I discovered the amount of things I wanted to weld that needed the AC simply wasn't enough to justify the cost of having AC on it. Most people never encounter magnesium in welding, so that leaves aluminium. And quite a lot of things made from aluminium can be made from steels, just using less of it.

More of the things I'm interested in are stainless, which wants DC. And a DC only set is a lot cheaper.

If you need to fix aluminium, and can't spend out on an AC set, there are hard soldering / brazing kits you can get with special fluxes that will let you do it with gas torches. Something that doesn't work with normal rods and torches.

Failing that, break out the pop riveter. :D Riveting is still a good idea on long welds. The Liberty / Victory ships of WW2 used an entirely welded hull. Which then tore open in the sea. The rivets where put back after enough of them sank.

[Edited on 6-2-2011 by peach]

grndpndr - 5-2-2011 at 19:21

Constance Tipper of Cambridge University proved the fracture problem was caused by cold temp steel embrittlement not the welds themselves.The fix wasnt to replace welding but reinforcement.A total of some 3-12 liberty ships were lost directly attributable to cracking out of some 2700 liberty ships built.Not a bad safety record structurally speaking considering
an emergency wartime measure.The ships were intended to have a service life of 5yrs.Most were sold following the war and eventually(commercial interests) just scrapped due to old age/economic decisions not structural worrys.FWIW

Source; Wikipedia

peach - 5-2-2011 at 20:53

This same riveting analogy occurs in the molecular structure of the metal it's self, via things called Cottrell atmospheres

grndpndr - 6-2-2011 at 05:18

Good Stuff, Thanks!:D

The Titanic disaster may not have been so disaterous(smaller open sea hull failure,longer time afloat) had the steel not suffered the same embrittlement(poor quality steel/riveted hull).Of course the iceberg had some effect.

[Edited on 6-2-2011 by grndpndr]

watson.fawkes - 6-2-2011 at 12:46

Quote: Originally posted by peach  
Quote: Originally posted by watson.fawkes  
So you're actual burning 2 H + O2 rather than H2 + O2.
As I understand it, oxygen isn't part of the equation. The heat comes from the atomic hydrogen recombining to H2.
You are correct. I was mistaken.

peach - 6-2-2011 at 15:48

Quote: Originally posted by grndpndr  
Good Stuff, Thanks!:D

The Titanic disaster may not have been so disaterous(smaller open sea hull failure,longer time afloat) had the steel not suffered the same embrittlement(poor quality steel/riveted hull).Of course the iceberg had some effect.

[Edited on 6-2-2011 by grndpndr]


I seem to remember the titanic also had another problem in that the interior walls, that were supposed to seal off the flooded sections, didn't run continuously up through her.

When one section flooded badly enough, the water would rise up a few decks and spill over into the next section. This was offset by the bilge and trimming pumps shifting the water, but those pumps aren't designed to prevent gross flooding.

It pains me to say it, but the Titanic was registered to the port of Liverpool and had Liverpool on the hull. That same port is within walking distance of my house and I routinely drive past the shipyards. One of my friends in school did his apprenticeship at the Cammell Laird yard and I get the gas for science experiments from the suppliers of the local shipyards. A substantial number of the naval vessels were built at Lairds; aircraft carriers, submarines, destroyers...

I will try to dodge some embarrassment by stating that the Titanic was actually built in Belfast, in Ireland, and set sail from Southampton. The three chief designers were staff at the Harland and Wolff yard in Belfast - so I'm pointing fingers for the blame at them! :D

I think there were 16 wall sections in total. Knowing what the ship was designed for, I wouldn't be surprised if at some point in it's design at least one person had said to the yard, "We can't have those big steel walls on the upper decks, they look terrible!"

Liverpool is the closest dock to Ireland, and I routinely see tanker trucks of Guinness going by. In fact, someone wrote to the local paper complaining about the noise. The ship's construction was founded in Liverpool, hence it being her port of register.

As with all accidents, one of the positive outcomes is being aware of how significant a previously overlooked problem can be in preventing a recurrence.

[Edited on 6-2-2011 by peach]

White Yeti - 31-7-2011 at 09:28

I would go with a long fuse. The shock wave from a firecracker will not provide better combustion than a fuse. The best way to ignite this stuff would probably be to put a spark gap in the centre of the balloon. That will give you the bang you're looking for.

jock88 - 22-3-2013 at 12:01




I was going to do the following very kewl display. I have not seen a similar idea on youtube or SciMad which I find surprising.

Make soap bubbles (lots of them) using an explosive mixture of Propane/Oxygen and stream them into a flame where they will pop/explode like firecrackers.

This is simple to do. Take a oxy/propane torch and extinguish a neutralized flame by swirling the cutter in some water. You are then left with explosive gas which you can use to blow bubbles using the end of a childs bubble blower gun.

The bubbles will be streamed towards a flame.
Has anyone done this?
It will be done in a large open shed.

Ral123 - 22-3-2013 at 12:36

http://www.youtube.com/watch?v=ypTADUYQ5ZI
hydrogen/oxygen is weak due to it's low density, butane/oxygen is the most powerful, readily made mixture.

jock88 - 22-3-2013 at 13:46


Thats one big balloon. I will have lots and lots of small bubbles.

Morgan - 2-5-2014 at 18:29

A long tube instead of a balloon.
Google translation
"Long hydrogen + oxygen collected by electrolysis tube by sealing the to fire someone."
爆鳴発火チューブ
https://www.youtube.com/watch?v=bCpjDWsIIvQ

Fenir - 3-5-2014 at 12:49

I was under the impression that the rivets on the Titanic failed due to high sulphur content.

gregxy - 13-5-2014 at 10:54

I remember going to a science fair (maker fair, I don't remember)
Someone had made a machine for demonstrating H2 O2 explosions. They had soapy water with electrodes underneath the surface. The gas released would form soap bubbles and you could ignite them with a spark device. The whole thing was enclosed in lexan, and in spite of this the "bang" from even a 1" bubble was uncomfortably loud! I think this gas mixture must make the DDT very rapidly since I don't think a simple unenclosed burning gas would produce a bang.

I also made a propane powered potato cannon, with a mixing device to insure it had a near stociometric mixture. It would go bang without any potato in the barrel (just the open barrel) and the shock wave from the open barrel could blow holes through thick cardboard. The runup distance for propane is definitely quite long but with it enclosed so much and ignited from multiple points (it had 2 spark gaps in series) I think its possible it made DDT.

Bert - 13-5-2014 at 19:45

The physicists and engineers my dad worked with in the early 1960's were not averse to a large explosion, alcohol, a summer pig roast party or (best of all worlds!) a combination of these three things.

They would take the largest diameter roll of plastic film tube from a bag making machine in the supply department at their research facility, a (certainly unauthorized and hideously expensive!) chemically pure Hydrogen gas bottle and a welding Oxygen Dewar, go out to the area behind the physical science lab machine shop where they held summer picnic parties and make 50 foot by 2 foot gas balloons with a "black cat" firecracker & a long piece of visco fuse as a detonator.

When sufficiently well lubricated, these PhD lunatics would turn loose one of these infernal devices as the announcement that the roasted pig was about to be served...

I don't really know what a normal childhood is like, mine was probably a lot more fun.

[Edited on 14-5-2014 by Bert]

Antiswat - 14-5-2014 at 02:38

H2SO4 and zinc seems as a great idea however, the H2SO4 wont boil out and doesnt need to be concentrated to work decently

if you strap a fuse to it make sure it bends away from the balloon, and its placed underneath the balloon, and if you want it even safer then put some masking tape around the fuse so sparks wont ignite it too early
also use a storm lighter and direct the flame away from the balloon
try not to have direct contact with the balloon and body parts

and most of all dont use flying fish fuse mounted on top of the superlight hydrogen balloon. lol.

Bert - 14-5-2014 at 05:12

No Hydrogen tanks around our house. No strong acids available to a 9 year old kid... But books and cooking/cleaning supplies were. I found a mention of hot solutions of washing soda (Sodium carbonate) in water mixed with Aluminum producing Hydrogen gas.

Well! A beer bottle filled with Aluminum foil chaff, water and washing soda from my buddy up the streets laundry room were cooking on the (GAS!!!) stove within minutes. A balloon was stretched over the top of the bottle...

We generated enough Hydrogen for a pretty good pop, before the bottle cracked from thermal stress, Hydrogen leaked and the balloon went off still on our makeshift gas generator. We were watching this process from REALLY CLOSE. With no safety equipment of any kind.

It was a good thing we weren't able to obtain acid or lye, boiling Sodium carbonate/Sodium aluminate solution was nasty enough.

Antiswat - 10-6-2014 at 10:31

sodium carbonate really???
can you not.. im already surprised..
i might need to look into this, could be very useful especially as i always rolls up aluminium foil when im 'done' with it to keep a smaller scrap pile of large surface aluminium

i still think i topped you in messing up, bert..

37% H2SO4
steel pot
seemingly didnt react with steel, supposing it was 'acid resistant steel'
gas stove
a few 100 mL, sure
about 20 minutes later i went back out to check up on it, finding a thick fog of SO3 as i opened the door, stepped back to fill my lounges up and then i dived into the hell of reality
boiling highly concentrated H2SO4 reacting with steel
my mom has since then accused me of nicking her pan lid, which i never touched, no clue what pan lid even, i had to throw away the steel pot, sandpaper didnt work at all

good thing i never got to order a package with oxidizers and metal fuels back then, shit could have escalated

once also managed to get a dangerous amount of hydrogen in a barn as i had a few friends over and decided to just watch them fuck shit up with a bottle of HCl and aluminium foil, using waaaay too much, and me just sitting at a chair watching, seeing them learn from mistakes
good luck their lighters didnt work, there was a good chance the entire building could have blown up from a lighter

Pyro_cat - 17-10-2019 at 20:05

Quote: Originally posted by crazedguy  
So I came up with the idea that you could put a balloon on a water bottle and capture the gases made by electrolysis.
The point of this would be to either tape a fuse to the balloon which would provide a sufficient bang, but I think it may be possible to get a better bang by strapping a small flash powder fire cracker to it.

So the question is would this provide better bang by setting it off with a small flash powder bomb would that get a full detonation, or would it be the same as just using a fuse?
I know that by adding 1 gram flash to set it off will be slightly louder but would it achieve full detonation. (1 gram-ish)

Would a balloon full of oxyhydrogen float?


This is old thread I know but I want to add to it.

When I was experimenting with the gas balloons I tried spraying the balloons with starting fluid to get a flame all the way around them hoping to ignite as much of the gas as possible at once like a 'fat man' implosion or at least not have any gases pushed away from a single ignition point and dissipated.

The flame would completely surround the balloon before it ruptured and ignited and it seemed to increase intensity but without a high speed camera I don't know if I was getting multiple ignition points.

Use a long thin tube to fill balloons, no reason to ever be real close to them.

Slow mo - balloon popping. https://www.youtube.com/watch?v=KdtSN7Zl9WQ

[Edited on 18-10-2019 by Pyro_cat]