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Water and what make gas?

  1. Aug 7, 2007 #1
    Hello:

    I was reading about the super fast chemical reaction which occurs in an airbag to release gas and produce a harmless byproduct from the normally caustic chemicals used.

    This made me wonder if a life vest could be inflated with a chemical reaction which reacts with water (as opposed to electricity in the case or the air bag). Of course one would not want the reaction to happen as fast as an air bag deploys, but does anyone know of any gas producing substances that when in contact with water (or other chemicals) produce enough gas volume to inflate a vest? Harmless chemicals would be best of course (or ones that become harmless during the reaction process).

    Any suggestions?
    Robhoski@yahoo.com

    Thanks
    Robert
     
  2. jcsd
  3. Aug 7, 2007 #2

    mgb_phys

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    Main problem would be making a system where water could flow in to start the reaction but the gas produced couldn't leak out.
    Another problem is that the gas produced from an explosive airbag is hot, this is an advantage in the air bag because it speeds the inflation but then slowly collapses the airbag as the gas cools - not the behaviour you want in a life jacket.

    You would probably still need some sort of trigger because you wouldn't want the system to be affected by moisture in the air, this would have to be a purely mechanical system because you don't want to include a power source in a device which is going to sit unused and untested for years.

    You could use a gas generator in place of the compressed air bottle normally fitted but it would weigh as much, cost more to produce and be a safety hazard on aircraft.
     
  4. Aug 7, 2007 #3

    chemisttree

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    You could use a mixture of ammonium phosphate and sodium bicarbonate (alka seltzer) if you could wait long enough for the inflation. Any mixture of a solid acid and bicarbonate would work (ie. citric acid + sodium bicarb).
     
  5. Aug 7, 2007 #4
    But wouldn't that take a lot of material to produce the volume needed? You wouldn't want to wait too long glug glug glug.
     
  6. Aug 7, 2007 #5
    Hey MGB ... thanks for the post and regarding the system to allow water in to start the reaction I was thinking "heart valve" when you mentioned it. Should be some method available to allow water in first and then seal for the remainder of the reaction. Makes me wonder how one would assure getting enough water in first before sealing. Hmmmmmm....
     
  7. Aug 7, 2007 #6
    How about this idea ... are there any chemical formulas that when exposed to water make a buoyant foam? That would be cool!
     
  8. Aug 7, 2007 #7

    chroot

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    Life vests in aircraft use ten-cent CO2 cartridges. They weigh almost nothing, cost almost nothing, inflate the vest in seconds, and are easy for the users to operate. Why reinvent the wheel? The cost of a one-way valve alone would defeat any economic advantage over the CO2 cartridge.

    - Warren
     
  9. Aug 7, 2007 #8
    Well ... I just know that when the horse and buggy were adequate enough to haul your butt down to the store for a loaf of bread, that many people probably wondered why you would ever need a car. They cost more, had more parts to break down, they weighed more than a horse, and they required training to operate. But they sure caught on.
     
  10. Aug 7, 2007 #9

    chroot

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    Your analogy is inappropriate for so many reasons it's almost laughable. Are you kidding me?

    - Warren
     
  11. Aug 7, 2007 #10

    mgb_phys

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  12. Aug 7, 2007 #11
    I believe it ... there is nothing new under the sun.

    Warren ... I liked my analogy ... I didn't waste too much time thinking of the perfect comparison because, like your reply, it didn't seem to be productive todo so. Keep an open mind my friend. Not everything is immediately apparent.
     
  13. Aug 7, 2007 #12

    chroot

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    You do understand the economic prinicple that makes the CO2 cartridge such a perfect solution to this problem, don't you? CO2 cartridges are used everywhere. Their integration into all sorts of products means the economy of scale comes into play, and you can buy them for next to nothing.

    As soon as you begin describing an invention, and mention anything so unique as a one-way valve for water but not gas, alarm bells begin ringing in my head. I'm an engineer and an entrepreneur myself, and I'm well aware of the forces that can make or break a design's profit margin.

    I see no actual advantages of your water-activated life vest over the existing CO2-inflated life vest, yet see a whole host of unique problems that might only be solved by unique design. If you ask me, the idea is dead in the water already. (Yes, pun intended.)

    - Warren
     
  14. Aug 7, 2007 #13

    mgb_phys

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    For lifejackets the CO2 cartridge and air chamber are probably ideal.
    There may be other areas where a chemical system is better, an oil retention system that sprayed a liquid that formed a floating foam barrier on contact with water to contain a leak.
    It's interesting that areas which need the fastest deployed mechanical motion, like airbags or guns use chemistry rather than mechanicla means.
     
  15. Aug 7, 2007 #14
    Bravo MGB ... a wise statement indeed. It's not always about the cheapest method being the best.

    How quickly some people will dismiss the value of an idea if it doesn't seem to add up financially.
     
  16. Aug 7, 2007 #15

    chroot

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    If it doesn't make sense financially, it will never sell. Do you not understand this?

    And I've yet to see any reason why the CO2-powered life vest is not, in fact, the best idea.

    - Warren
     
  17. Aug 7, 2007 #16
    The life vest application is only suggested as a representative benchmark for the sake of discussion. Do you understand that Warren? It is only to offer a starting point to work from. I'm not suggesting we make a chemically operated life vest here in this forum (although I do not think it is beyond reason to consider it). The idea is to exchange information about chemically reactive substances which may or may not be activated my water to produce a buoyant foam or inflate an object. Now go lay down by your dish.
     
  18. Aug 7, 2007 #17

    chroot

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    Your very first post described a chemically operated life vest. I'm simply responding to what you posted. And, btw, your little jabs about my lack of creativity seem pretty silly -- I hold two patents, one of which made a million dollars in the last fiscal year.

    - Warren
     
  19. Aug 7, 2007 #18
    No wonder its all about the money ... sorry for poking fun back at you. Really I'm glad you have done well with your patent. You are one of the few that do well in that arena. Do you mind sharing the concept of your patent?
     
  20. Aug 7, 2007 #19

    chroot

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    http://www.freepatentsonline.com/20070052849.html

    Well, the reason I'm "all about the money" is not because I'm rich, or value being rich above all else. The reason is that a device that you intend to sell in bulk -- like a life vest marketed to airlines -- absolutely has to outperform its competition in price or it will not be considered. The CO2 vest works very well, and is cheap. It's a formidable opponent, one that I would not consider taking on.

    - Warren
     
  21. Aug 7, 2007 #20
    Warren;
    I understand your view. A simple, "remember it has to be affordable in order to sell" comment would suffice.

    Some things sell regardless of price. Not to mass market consumers though. Usually to governmental agencies who could care less how they spend your tax dollars:)

    I'm glad it's not just about the money for you. That reminds me of an old saying, "the poor are lucky because they still believe money can buy happiness, ... the rich have already discovered it is not true."

    I believe in doing what you love to do and working toward allowing your passions in life to sustain you. Not always easy I know, but a goal worth pursuing.
     
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