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  1. #1
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    Default What gas is this?

    I was pumping water out of an aquarium and the intake hose before the pump kinked, at the kink there was a stream of "air" bubbles that formed due to high vacuum. It would seem that the bubbles would go back into solution pretty quick but the bubbles went through the pump and continued all the way down a 50 foot exit hose. Now, let's say we put a 'T' in the line with a tube sticking up to collect these bubbles into a large container. Seeing as though water is only composed of oxygen and hydrogen what would this "air" be composed of? Would it be breathable?

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    Quote Originally Posted by Bluechipx View Post
    I was pumping water out of an aquarium and the intake hose before the pump kinked, at the kink there was a stream of "air" bubbles that formed due to high vacuum. It would seem that the bubbles would go back into solution pretty quick but the bubbles went through the pump and continued all the way down a 50 foot exit hose. Now, let's say we put a 'T' in the line with a tube sticking up to collect these bubbles into a large container. Seeing as though water is only composed of oxygen and hydrogen what would this "air" be composed of? Would it be breathable?
    a low vacuum such as the aquarium pump wouldn't be able to disassociate hydrogen and oxygen, even a high vac alone doesn't do that in the absence of other energy input (I don't think). Seems to me I's obviously "air", with a variable O2 content depending on the conditions in the tank. if you trap some, and it IS explosive, that might prove me wrong though!

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    But there can be all matter of gases dissolved in the water. When you pull a partial vacuum on it they come out. For an aquarium it is most likely just air, but could well have some carbon dioxide content as well.

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    Just dissolved air at a guess though with organic crap maybe a bit of methane, l had a fish tank once, that thing could get stinky, strange slimes and biofilm, not sorry it’s gone, fish were more work than I thought
    Mark

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    Air, cavitation. Same air bubbles that release just before water boils. The vacuum lowers the boiling point. Designers of pumping systems usually check for positive suction head at pumps.

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    Quote Originally Posted by deltap View Post
    Air, cavitation. Same air bubbles that release just before water boils. The vacuum lowers the boiling point. Designers of pumping systems usually check for positive suction head at pumps.
    I'll agree that the 'air' generated at the vacuum of cavitation is the same as the 'air' that comes from boiling water, but what is it's actual composition? Is it breathable?

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    Quote Originally Posted by Bluechipx View Post
    I'll agree that the 'air' generated at the vacuum of cavitation is the same as the 'air' that comes from boiling water, but what is it's actual composition? Is it breathable?
    Almost all normal air that you breath, plus a small amount of fish farts would be my guess.

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    It sounds like you are looking at a machine that would extract oxygen from seawater I'm sure you could do it but it is going to contain ll sorts of things you don't want. You can separate the O2 with pressure swing adsorption or a membrane system, but I believe the O2 level is low at depths where such a system would be useful and the helium level is lower. It wold be cheaper to send down extra tanks.

    Bill

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    It's just air... 20% oxygen 80% nitrogen. That's what the fish breath, their gills are designed to pull the O2 out of it.
    Dennis

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    Quote Originally Posted by Bluechipx View Post
    I'll agree that the 'air' generated at the vacuum of cavitation is the same as the 'air' that comes from boiling water, but what is it's actual composition? Is it breathable?

    Boiling water is just that
    Steam Water as a gas

    Peter

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    Does your fish tank have an ................."AERATOR" ??

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    Methane.....Your single handily contributing to Michigan's global warming quota !

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    This whole thread reminds me of why WC Fields said he never drank water - because of what fish did in it.

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    Quote Originally Posted by Scottl View Post
    This whole thread reminds me of why WC Fields said he never drank water - because of what fish did in it.
    This thread has reminded me how badly basic k-12 education has fallen over the years....

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    I suppose there could be small quantities of pure O2 or CO2 produced by plant life and trapped in the mud. probably just air.
    Bil lD

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    Default Wtf

    Thread closed in 4 3 2.......

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    I've seen bubbles form in a gasoline siphon hose the same way. What is outgassing from the gasoline to form those bubbles?

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    No, it's just the air bubbles in the intake tube rising to the top.

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    Quote Originally Posted by petersen View Post
    Does your fish tank have an ................."AERATOR" ??
    Good point. If it does, the dissolved gas is probably near saturation and it wouldn't take much pressure drop to pull some out. Deaerating a liquid is interesting. The air comes out first in foam which rises in the container just like beer or soda, then it suddenly drops. Increasing the vacuum starts vaporizing the water or solvents if there are any. Water will boil, but an odd form, not like you see in cooking.

    Deaerating things like castagble resins is standard practice when it is molded to avoid having a porous part. Stirring in some air is almost unavoidable when mixing unless you have a gun with a mixing nozzle.

    Bill

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    If the graph below is correct, at room temperature the solubility of oxygen in water is 1.7 mmoles/liter. Nitrogen is about 0.6 mmoles per liter. Air is about 80% N2 and 20% O2, so that would mean that at equilibrium you have about .34mmole/liter O2, and about 0.48 mmole/liter N2 dissolved. Draw that down to total vacuum, and the gas in the bubble is about 41% O2. So the bubble, under some reasonable assumptions is somewhat O2 enriched air.

    Yes, you could breath it, but why would you want to?



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