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Baking Soda and Vinegar?

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Unread postAuthor: SpudBlaster15 » Fri Jun 10, 2011 3:27 pm

tbillion wrote:1.36 is the number of atmospheres in the jug? what is an atmosphere 4.7 is atmospheric pressure? increasing the volume to place in the jug by 5 i get because i want 5 psi. where did the 1.36 and the 4.7 come from is where i am lost at this point. gases is new science to me.


Ino is pretty terrible at chemistry ( :wink: ), so I'll explain this a bit more thoroughly.

One atmosphere is equivalent to 14.7PSI absolute pressure. You are looking to raise the internal pressure in the jug to 5PSI gauge pressure, which is the differential between the interior of the container and the atmosphere. This can also be expressed as 19.7PSI absolute pressure.

Dividing the absolute pressure after the addition by the initial (atmospheric) pressure will give you the ratio of the final pressure to the starting pressure, which is actually 1.34, not 1.36 as was stated above.

Finally, multiplying this ratio (1.34) by the starting volume (5L) and subtracting the initial volume gives you the final atmospheric pressure gas volume equivalent which must be added to the vessel in order to raise the pressure by 0.34atm (5PSI).

V<sub>addition</sub> = (1.34*5L) - 5L
V<sub>addition</sub> = 1.7L

Using Boyle's law is much simpler, but the above approach is more intuitive.

EDIT: Also, way to kick up a 5 year old thread, for a second I thought BLB had actually returned to the forum. :cry:
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Last edited by SpudBlaster15 on Fri Jun 10, 2011 3:33 pm, edited 2 times in total.
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Unread postAuthor: saefroch » Fri Jun 10, 2011 3:30 pm

Atmospheric pressure in psi is 14.7

Almost no appreciable amount of CO<sub>2</sub> will be dissolved in the water... and the use of a dessicant would just take up even more volume in the chamber... that's before you consider the fact that vinegar is only 5% acetic acid, so you have a whole heck of a lot of water to absorb.

If using sulfuric acid and a metal (as it is now called, tech's diagram is fairly ancient), the gas produced will be hydrogen, which really doesn't appreciably react with water.

Concentrated acids are very dangerous, I highly recommend against using them.
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Unread postAuthor: tbillion » Fri Jun 10, 2011 3:39 pm

5 years old but still full of useful information that is new to me!, thanks for the thorough explanation!

I have been using high concentrated acids for years, for different purposes. for my purpose now, if I use a high concentrated acid, and only need to create a minimal amount of gas to inflate something so that it will not collapse upon itself when outside pressure is applied then I am interested. In this solution I need to be super mindful of the weight of the reactants due to the fact that the more they weigh will reduce my over all buoyancy.
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Unread postAuthor: tbillion » Fri Jun 10, 2011 3:42 pm

also found nothing when i searched tech's diagram.. care to shed more light on that?
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Unread postAuthor: Technician1002 » Fri Jun 10, 2011 5:40 pm

I just googled the image of the extinguisher. Most of the time the manufacture did not provide any refill instructions as you had to use a fire extinguisher service company to maintain certification. I don't know the acid strength or quantity of bicarb in the water. Sorry I don't have any more details on those antiques.
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Unread postAuthor: inonickname » Fri Jun 10, 2011 8:39 pm

SpudBlaster15 wrote:
tbillion wrote:1.36 is the number of atmospheres in the jug? what is an atmosphere 4.7 is atmospheric pressure? increasing the volume to place in the jug by 5 i get because i want 5 psi. where did the 1.36 and the 4.7 come from is where i am lost at this point. gases is new science to me.


Ino is pretty terrible at chemistry ( :wink: ), so I'll explain this a bit more thoroughly.

One atmosphere is equivalent to 14.7PSI absolute pressure. You are looking to raise the internal pressure in the jug to 5PSI gauge pressure, which is the differential between the interior of the container and the atmosphere. This can also be expressed as 19.7PSI absolute pressure.

Dividing the absolute pressure after the addition by the initial (atmospheric) pressure will give you the ratio of the final pressure to the starting pressure, which is actually 1.34, not 1.36 as was stated above.

Finally, multiplying this ratio (1.34) by the starting volume (5L) and subtracting the initial volume gives you the final atmospheric pressure gas volume equivalent which must be added to the vessel in order to raise the pressure by 0.34atm (5PSI).

V<sub>addition</sub> = (1.34*5L) - 5L
V<sub>addition</sub> = 1.7L

Using Boyle's law is much simpler, but the above approach is more intuitive.

EDIT: Also, way to kick up a 5 year old thread, for a second I thought BLB had actually returned to the forum. :cry:


You bastard :P the 1.36 came from using 20 instead of 19.7. Or I guess he might have a gauge that reads to 0.1 PSI? :roll:
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Unread postAuthor: tbillion » Fri Jun 17, 2011 9:47 pm

well thanks to all that helped when i first read this forum I didn't even know that a gas law was what I was looking for, thank you for putting up with my questions I really appreciate that!

If you would like to see how i have applied this information you can check my temporary website @ http://travisgillespie.netau.net/
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