Oxygen/Acetylene

[Knoxville]

I saw a friend of mine this weekend make a 5 gallon oxy/actylene bomb. For the time involved and cost of the gas, it was one heck of an explosion. He placed a 55 gallon drum upside down on the bucket and used an electric spark to ignite. It launced the 55 gallon drum almost 60 feet into the air. I was just amazed!!! Now I'm curious as to how violent of an explosion this was. Anyone have any number or info on the resulting explosion from mixing Oxygen/Acetylene in a true 50/50 mixture? VOD? Thanks in advance.

[Kleng]

1 part Acetylene and 2 parts Oxygen I guess.

[ShadowMyGeekSpace]

Why 1:2 ratio? The optimum burn ratio is 1:1.1-1:1.5, or for simplicity 1:1.

edit:

Never mind. I'm thinking of the optimum ratio for welding(1:1.1-1:1.5), not explosive power.

[Cindor]

I've read that between 3% and 87% of acetylene in a closed area is explosive.

[ShadowMyGeekSpace]

I've read that between 3% and 87% of acetylene in a closed area is explosive.There's a big difference inbetween 3% and 87%, and we're looking for the optimum ratio of fuel to air/oxygen.

[lucas]

Easiest way is to light the torch, adjust for a neutral flame and then snuff. The cone should be convex and the should be no obvious feather to the flame. If the cone is concave or deformed the flame is oxidising and if there is a feather around the cone then there is excess fuel.

[Chris The Great]

Um, guys, let's think about this.

2C2H2 + 5O2 -> 4CO2 + 2H2O

2 acetylene : 5 oxygen by volume for maximum energy release. Simple.

[shooter3]

Word of caution; I've made these for over 30 years and last Fall I had my first accident(posted on another thread). I had one go off in my hand.

Lucky for me I was just starting to fill the bag. I'm 90% sure that it was caused by the plastic bag sparking as the two sides of the bag separated(It was a very dry fall day).

Fill the container remotely if possible. If it's small, and you simply have to fill the bag by hand, pre fill it with air and put a spoon of salty water in and shake.That should short out any static electricity.

[Knoxville]

I've read about various methods of filling a container to put the oxy/acetylene in, but have not read my method on here. I fill my containers pretty accurately to 1:1 ratio. I have never used any sort of bags as a container for the gas. I always use a 20oz soda pop bottle, 2L bottles, gallon milk jugs, 2.5 gallon jugs, or on a froggy day, a 5 gallon bucket. Next to where our welding equipment is, we have a 30 gallon trough to throw hot parts into to cool down after cutting or a little welding. If a person was the use the 2L bottle, they would fill the bottle with water and place the original cap back onto it. Hold the bottle under the water in the tank and remove the cap. Turn on only the oxygen and place the tip in the water and the nozzle up in the bottle. This has to be done with the bottom of the bottle parallel with the top of the water. You can draw a mark on your container or just eye ball where you think half is. The oxygen bubbles will force the water out of the bottle and push it back into the trough. Once half full, put the cap back on or have someone turn the oxygen off and turn the acetylene on. Repeat process until all water is forced from the container. This is done under water so it does minimize static electricity.

[FullMetalJacket]

Unfortunately I forget the precise ratio, but it was quite a small percentage of C2H2, and in that ratio the mixture would detonate as a HE.

[Jacks Complete]

Just blow into the plastic bag, your breath will be more than enough to deal with the static.

The 3% to 87% mix is too wide, I think. That's more like Hydrogen's range.

Acetylene will explosively blow itself and its container to bits, even without oxygen. Just beat or drop an acetylene cylinder. They often explode hours later.

[nbk2000]

Giving it a dusting of graphite dust, or a spray of anti-static, would be very prudent, and doesn't introduce any moisture into the reaction.

In fact, putting some metal powder of a combustible nature in the bag would be an extra. ;)

[Thorr]

Um, guys, let's think about this.

2C2H2 + 5O2 -> 4CO2 + 2H2O

2 acetylene : 5 oxygen by volume for maximum energy release. Simple.

wrong, you must work out the atomic mass of the reactants before making any sort of assumption on percentage ratios.
2(24+2) + 5(32)
52 + 160 <52 +160= 212)
therefore
52/212 160/212
=0.2453... =0.7547...

<multiply by 100 and round off to get percentage ratios>

--> 25 : 75

-->this comes out as a 1:3 ratio

[another_number]

wrong, you must work out the atomic mass of the reactants before making any sort of assumption on percentage ratios.


Apparently you've never heard of gas laws before? All you need is the equation and under ideal circumstances your ratio is done.

C2H2 + 5/2 O2 --> 2 CO2 + H20

1 litre of acetylene for 2.5 litres of oxygen gas.

++++++=

Ratios by volume or by weight?

There can be two different answers to the same question, both of which are correct.

NBK

[another_number]

Ratios by volume or by weight?

There can be two different answers to the same question, both of which are correct.

NBK

Kind of complicated to get the mass of gas, but true. My apologies to Thorr, as I didn't realise he was doing the ratio by mass.

[Ricky]

There is some info here, you need calcium carbide to obtain a volume of acetylene by ratio from calcium carbide and water.
calcium carbide, 64,10 g/mol
CaC2 + 2 H2O => C2H2 + Ca(OH)2
It`s easy, place some calcium carbide in a beaker and with a funnel some distilled H2O is dropped into the beaker. I belive the process is a little bit exotermic.

[Cindor]

Yeah, but just a little bit...nothing considerable if you use a little bit extra water... a good one is: instead of water use hidrogen peroxide, highly concentrated... then you got C2H2 + O2 in the same conteiner with just one step, since H2O2 decomposed giving O2 and water, and the water with the CaC2 gives you acetylene :D

[Sausagemit]

I never thought of using H2O2 and CaC2 before, sounds interesting and dangerous. :D

I bet one could make a very simple and effective device out of H2O2 and CaC2 if one were so inclined. What I would do is take a 2 liter bottle, drill a small hole in the the top, insert a wire for ignition (and of course silicone the crap out of the hole so no leakage occurs). Rig up something to drop the carbide into the H2O2 when you want too. Suck most of the air out of the bottle and have fun. In fact, I may try this if I can find my CaC2.

The only problem I can think of is the H2O2 screwing with the ignitor. Has anybody dipped nichrome wire ignitors in wax or some other form of waterproofing with any degree of success?

Calcium Carbide is fun to screw around with to any degree though. For such things as starting fires with water, putting in toilets with soap and then lighting them and thus creating a flaming toilet, ect.

[Cindor]

When I use Cac2 and H2O2 I do this:
Take some stones of carbide (the sharper the best) and put then in a bottle, and put a ballon with 75 - 100 ml 30% Hperoxide inside the bottle, but not touching the carbide, hanging from the neck and close it.
Previously you need to drill a hole, and put 2 wires with a waterproof charge (I use flash powder), and close it with some epoxy or somthing.
At the time you wanna use it you just open it, let the ballon fall slowly, close it and shake it. Wait a couple of seconds and shoot.
Is not a perfect burning, but it will make a very big shockwave.

[NoltaiR]

While I am sure you guys could debate proper equation balancing all day.. I used to play with this stuff back in the day and I would have to agree with the 1:3 ratio.

And as elementary as the whole oxygen/acetlyene mix is, anyone who has actually seen it explode has a respect for it. There is not a whole lot of purpose this explosive can be used for since it is a gas and requires considerable more volume than it's solid or liquid counterparts.

...but it sure is fun to watch :)

An interesting idea would be (although this could be VERY dangerous if you are not careful) to take 2 large, durable balloons. Fill one balloon with a small amount of gasoline.. small meaning in relation to the total volume of the balloon. Then stick the other balloon inside of it and fill with oxygen/acetlyne mix.

So what you end up with (assuming this idea actually is possible outside of my imagination) is a very simple FAE. Someone should try this.. the only problem I see is the gasoline trying to come out as you fill the inner balloon with the gaseous mixture.

But if this does work.. I could forsee some very large explosions.. especially if you enriched the oxygen ratios to compensate for the added amount of fuel.

[FUTI]

*me thinking about this*
1. acetylene has widest range in which it can explode in mixture with air from 2 % to 85% IIRC
2. acetylene is also known for its nasty ability to be prone to explode under high pressure even alone (that is why they add acetone and other stuff to the high pressure containers)
3. if you mix above proposed components in high pressure container (I guess above 20atm will be fine)...it will generate acetylene and oxygen (and do not forget the heat)...pressure will rise...*something might burst*...please post a video/picture if you test this

In one of my first posts I had similar idea with carbide but I didn't propose usage of H2O2...that is why I like this forum, this can be interesting idea Cindor...what does Merck index say about compatibility of those substances, or is it even stupid to ask :)?

[Ricky]

Yes there is definately a problem there, lab equipment is advised for the carbide process if you bubble acetytyene through any solution. Water is poison for that. 100 g CaC2 will give around 26 litre acetylene.
It looks interesting, CaC2 and H2O2 for a dangerous acetylene/oxygen mix.

[vod8750]

I worked in a fabrication company out in the countryside for a while and now and again when I'd be alone in the workshop (which wasnt very often) I'd fill 500ml plastic bottles with oxy/acetylene mix and throw them in a fire. I found the best way to fill them was to fill the bottles with water first, hold the bottle upside down so the opening is underwater then stick the torch into the opening underwater and turn on the gas. That way you know that all the gas in the bottle is the stuff you need.
I experimented with a few ratios(roughly): 75%acelylene/25%oxygen, 50:50 and 25acetylene/75oxygen. If i remember right the 25:75(more oxygen) ratio gave the loudest bang when it was just thrown into a fire. Even then it was only just louder than a bp banger!
I obviously would have got way better results if I had an elecrical ignitor inside the bottle or a fuse or something like that but I just didnt have them convenient at the time. I havnt tried it since though!

Another time I tried to make a pressure bomb using water and CaC2 in a 500ml soft drink bottle and igniting the generated acetylene after with a tin can of burning petrol beside it.
The only problem was that there wasnt enough generated acetylene to burst the bottle so after a while I just said to hell with it and used a long stick to spill the burning petrol over the bottle since acetylene is explosive under pressure. When the fire burned through the bottle or heated the acetylene to the right temperature(I dont know which) I got a really loud bang and a quick flash of fire. I've got the whole thing on video!:D

Only thing is other than how loud it was I didnt get any other signs of how powerful it was as I did it on grass on level ground! Has anyone any idea of how powerful acetylene under pressure really is? Does it have to be ignited by a spark in the pressurised container and does it have to be under a certain pressure to be truly explosive?

[FullMetalJacket]

Vod: That is so incredibly unsafe I don't want to think about it.

[Bert]

I learned the hard way about the dangers of this mix. So have many others.
http://darwinawards.com/personal/personal2002-29.html

http://tinyurl.com/gxld5

I would not use this again.

[megalomania]

One of the maintenance guys where I work told me he used to work at another plant where this guy would crawl up onto a machine and fall asleep. One day they filled two of the very large 60 gallon plastic trash bags with acetylene and oxygen from a welding torch and let it drift up. I forget how they said they had them timed for ignition, a cigarette maybe, but they both floated up on either side and blew up within a second of each other.

Apparently he was so scared he almost jumped off the machine, only to find about 20 guys standing around at the bottom laughing at him. Doing what comes naturally to a man caught sleeping and made the butt of a joke, he almost started a fight.

Let this be a lesson to you; company executives only work from 10-4, 10-2 on Fridays, so there is no one around to hassle the night shift :)

[Jacks Complete]

Mega, lower executives are always on 'duty', having sold their souls to the company, but they never actually work!

Calcium carbide is about the greatest thing ever. I think I still have some stashed someplace.

[vod8750]

Wow thanks Bert! I dont think I'll be doing that again!

Although the plastic bottles took about 10 seconds to explode after they got thrown in the fire so in that time I was a good 50m or more away. I wouldnt even think about using a garbage bag as my container! I'd be scared stiff of static!

And I did use a very long stick to knock over the can of petrol and again it took a good 10 seconds or more to explode so I had plenty of time to put some distance(and concrete) between the bottle and me!

[IronMongrel]

An interesting article from the 1911 Britanica with reference to the explosive power of liquified acetylene

http://www.1911encyclopedia.org/Acetylene

When I was at college doing my c&g in oxy/acetylene we where taught that the oxygen bottle was the real menace.

[CreepingEagle]

I'm 90% sure that it was caused by the plastic bag sparking as the two sides of the bag separated(It was a very dry fall day).

What about using a lubricated condom? I know they can blow up fairly easy....and I'm no chemist, but wouldnt all the water based lube prevent any static electricity? I havnt tried it and dont plan on it untill I've learned more. But like I said I'm no chemist, this is just what came to mind. So please tell me if I'm right or wrong or if I'm about to blow my head off :P