[aradontheline]

hello everybody,
I don't know if this is the right place to ask this question, I hope though.
there is a step in the project I am working on, in which there should be a chemical reaction to produce enough gas to fill a tube.
Just like what happens in airbags. But there are some differences in the process that I am looking for comparing to what happens in airbags.
first of all I need the raw material to be as cheap as possible.
The reaction doesn't need to happen very fast like in the airbags, actually it could even last for an hour.
And the reaction products shouldn't be flammable, explosive or corrosive.

So if anybody could give me a clue I really would be thankful.
Arad

[enahs]

Ever throw an alka seltzer into water?


Or baking soda + vinegar.

[fledarmus]

Do you actually need a chemical reaction to do this? The reason airbags use chemical reactions is that they need something filled very fast, and an explosive creates a lot of gas very fast. If you've got an hour, it would probably be cheaper and safer to use compressed air. If you want it to look like a chemical reaction, it's easy enough to simulate something like a baking soda/vinegar reaction by running an air tube into the bottom of the vessel you are supposed to be running the reaction in, and letting the air bubble up through the water.

You could also put a lot of dry ice in your tube and let it evaporate, filling the tube with carbon dioxide.

[aradontheline]

Thank u guys.
Dear Fledarmus the tube I am talking about is about 500 m long with a diameter of about 20 cm that had been divided in sections of 20 m length.
right now every section is filled with air using a blower. The operation is carried out on the rivers, lakes , seas by means of a small ship. the tube is rolled out and every section filled with air and mean while it is leaving the ship into water. it is a time consuming labor.
I was wondering if there is a material available that could react and produce enough gas as the tube sections enter water.
Dear enahs , well thank u for your suggestions, right now I'm checking your suggestion, but I am afraid they may be kind of expensive

[enahs]

You can buy baking soda (sodium bicarbonate) and vinegar (acetic acid) fairly cheap in bulk quantities. Do not get them from the grocery store.

It is probably the cheapest method I can think of. But fledramus idea of dry ice is a lot easier. If you would use it a lot, you could purchase your own dry ice maker.

[fledarmus]

Wow, that's a big tube to fill with a chemical reaction. Just doing a rough back-of-the-envelope calculation and assuming that carbon dioxide is an ideal gas at STP, you're looking at over 600 L of gas for every 20m section, which would require over 2 kg of sodium bicarbonate per section, close to 60 kg total. You'd also need almost that much glacial acetic acid (that's concentrated, not vinegar - vinegar is about 5% acetic acid, so add another 19 times that weight in water if you're using vinegar). That's going to make for a very heavy tube.

For dry ice, you get off a little easier - only about 1.2 kg of dry ice per section, but then you'd have to find a way to get it into the sections. I think handling the air hoses would be easier.

[408]

I would just use a gas generating compound.  Triaminoguanidinium azotetrazolate comes to mind.  Or if you want to go traditional, sodium azide.

leave the baking soda and vinegar to the kindergarteners... 

[aradontheline]

Oh , thank u very much guys. very interesting answers.
right now I am checking the possibilities and see if there is a chance to find the right chemical or I should give it up.

Actually cause I am not looking for a fast reaction I thought there may be such a chemical to produce enough gas for me to fill the tubes automatically.
Well as I said before the task of filling the tubes is difficult and it limits the expansion of tube.

[408]

I don't want to buy what you are selling.

[aradontheline]

Oh, please 408, U gona love it. I need to finish it, it could be helpful for protection of environment against oil pollution.

[408]

There was a spam post I replied to, which has since been deleted. 

I have another idea.  Smokeless powder for firearms.  Ignite an amount in a small, lightly confined capsule to fill the tube with gas.