The Straight Dope

Go Back   Straight Dope Message Board > Main > General Questions

Closed Thread
 
Thread Tools Display Modes
  #1  
Old 03-28-2003, 10:48 AM
Ein Stein Ein Stein is offline
Guest
 
Join Date: Mar 2003
Preserving Soda Fizz

You can buy closures which include a hand pump for compressing air into a partially filled soda bottle which is supposed to preserve the fizz? Can that actually work? I thought the space would have to be filled with carbon dioxide to have any effect.
Advertisements  
  #2  
Old 03-28-2003, 11:11 AM
FatBaldGuy FatBaldGuy is offline
Guest
 
Join Date: Jan 2001
We have bought these in the past, and they do work. My (limited) understanding of the principle is that by keeping a high level of air pressure within the bottle the carbon dioxide dissolved in the soda stays there, rather than evaporating into thin air (excuse the pun).
  #3  
Old 03-28-2003, 11:20 AM
Ein Stein Ein Stein is offline
Guest
 
Join Date: Mar 2003
I'm agraid that's a rather lame reply - I'm surprised you bothered.

The concentration of solute [in this case carbon dioxide] is supposed to be proportional to the partial pressure of that gas in the atmosphere over the solution [Henry's Law or something like that]. There is only a few hundred part per million of CO2 in the air so I don't see how that can be reponsible for maintaining the fizz.

Can anybody provide more insight here?
  #4  
Old 03-28-2003, 11:37 AM
RealityChuck RealityChuck is offline
Charter Member
 
Join Date: Apr 1999
Location: Schenectady, NY, USA
Posts: 39,986
It's not the CO2 in the air in the bottle; it's the partial pressure of all the air.

If the air is of lower pressure than pressure on the CO2 in the liquid, the CO2 will will bubble up until it reaches equilibrium. If the pressure in the air above is the same as the pressure of the CO2 in the liquid, then it will remain in equilibrium and won't escape from the liquid. If the air above is at a higher pressure, some of the air will dissolve back into the liquid.

The air in an unopened soda bottle is just plain air, and the liquid can go a very long time before losing its fizz. Similarly, if you shake a bottle of soda, and then let it sit for a day or so, the CO2 will redissolve and you won't have the bubling up you usually get when you shake the bottle.

I haven't tried the pump closures, and they may have other problems (e.g., they may leak, negating any advantage). But the theory is sound.
__________________
"East is East and West is West and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does."
Purveyor of fine science fiction since 1982.
  #5  
Old 03-28-2003, 11:52 AM
Ein Stein Ein Stein is offline
Guest
 
Join Date: Mar 2003
That's gotta be wrong too. I'm new to this board but so far I think you're a bunch of poseurs. I just looked up Henry's Law:

Henry's law is states that, at a given temperature, the amount of gas dissolved in a solute is directly proportional to the pressure of the gas above the substance. This can be represented by the equation where the pressure is measured in atmospheres and the Henry's Law constant is also measured in atmospheres and where is the mole fraction of gas.

So that says that it's NOT the total pressure of gas above the solution that is relevant. Only the proportion of the headspace gas that is CO2 is relevant. I know that bottles are factory-filled with CO2 in the headspace so it makes no sense that replacing it with air will do anything according to Henry's Law.
  #6  
Old 03-28-2003, 11:57 AM
Ike Witt Ike Witt is online now
Charter Member
 
Join Date: Aug 1999
Location: Lost in the mists of time
Posts: 13,082
If you want to maintain the fizz in an opened 2 litre bottle of soda, all you have to do is squeeze in the sides a little. Pour yourself a glass, and then squeeze in the sides so the liquid is near where it would be when the bottle is new. The next day, the bottle will have expanded out to its original size and the pop will still fizz. AFAIK, you want to limit the area that the CO2 can expand into.
  #7  
Old 03-28-2003, 12:04 PM
Ein Stein Ein Stein is offline
Guest
 
Join Date: Mar 2003
Wrong AGAIN! Squeezing the bottle reduces the area above the liquid temporarily until more dissolved CO2 escapes to equilibrate the pressure to atmospheric. Hence, a decrease in dissolved CO2 concentration and LESS fizz.
  #8  
Old 03-28-2003, 12:18 PM
Ike Witt Ike Witt is online now
Charter Member
 
Join Date: Aug 1999
Location: Lost in the mists of time
Posts: 13,082
Quote:
Originally posted by Ein Stein
Wrong AGAIN! Squeezing the bottle reduces the area above the liquid temporarily until more dissolved CO2 escapes to equilibrate the pressure to atmospheric. Hence, a decrease in dissolved CO2 concentration and LESS fizz.
No. It isn't wrong. I do this all the time and soda that would normally be flat after 2 days is still fizzy after 4 days.
  #9  
Old 03-28-2003, 12:22 PM
Whiskey-Hotel Whiskey-Hotel is offline
Guest
 
Join Date: Mar 2003
How's this for an answer. Why don't you: a) buy one and try it out yourself; or b) Just drink all the damn soda at one sitting and back off on the belligerent attitude a bit.
  #10  
Old 03-28-2003, 12:31 PM
Ein Stein Ein Stein is offline
Guest
 
Join Date: Mar 2003
Attitude shmattitude. Only a controlled experiment can determine if that product works. And the point here is to explain on why or how it can work.

Are you all unemployed and on Prozac?
  #11  
Old 03-28-2003, 12:49 PM
Ein Stein Ein Stein is offline
Guest
 
Join Date: Mar 2003
I just thought of why you morons think that pump works: when you repressurize the bottle, it will then hiss when you release it. That gives the PERCEPTION of fizz but it's actually just a sound effect. I bet if you did a double blind test, you would find the soda is equally flat in the pumped bottle as the control.

Plenty of people think that copper or magnetic bracelets cure arthritis but it doesn't. There's a sucker born every minute.
  #12  
Old 03-28-2003, 01:22 PM
cmyk cmyk is offline
Member
 
Join Date: Mar 2001
Location: The Mitt
Posts: 13,787
Quote:
Originally posted by Ein Stein
Plenty of people think that copper or magnetic bracelets cure arthritis but it doesn't. There's a sucker born every minute.
Sounds to me like someone's been burned, before.
  #13  
Old 03-28-2003, 01:22 PM
Zazie Zazie is offline
Guest
 
Join Date: Jul 2001
I bought one of those "devices" and it does work, I was surprised.
And Ein Stein, you know it all anyway so why do you ask?
  #14  
Old 03-28-2003, 01:36 PM
bibliophage bibliophage is offline
Charter Member
Charter Member
 
Join Date: Apr 2000
Location: Maine
Posts: 10,057
Ein Stein, insulting other posters outside the BBQ Pit is not permitted here. If you repeat the behavior you are subject to being banned.

bibliophage
moderator GQ
  #15  
Old 03-28-2003, 02:12 PM
Jonas Marainen Jonas Marainen is offline
Guest
 
Join Date: Jun 2000
Quote:
Originally posted by Ein Stein
That's gotta be wrong too. I'm new to this board but so far I think you're a bunch of poseurs. I just looked up Henry's Law:

Henry's law is states that, at a given temperature, the amount of gas dissolved in a solute is directly proportional to the pressure of the gas above the substance. This can be represented by the equation where the pressure is measured in atmospheres and the Henry's Law constant is also measured in atmospheres and where is the mole fraction of gas.

So that says that it's NOT the total pressure of gas above the solution that is relevant. Only the proportion of the headspace gas that is CO2 is relevant.
I believe that you are overlooking the simple fact that the partial pressure of the CO2 is proportional to the total pressure of the gas mixture (i.e. the air). So, when you compress air into the soda bottle, you are increasing the partial pressure of CO2. Given that higher partial pressure of CO2, the amount of C02 that can remain dissolved in the soda increases (Henry's Law).

In essence, if you want to maintain the fizz in your soda, you have to choices: increasing the proportion of CO2 in the gas mixture above the soda, or increasing the total pressure and therefore also the partial CO2 pressure.

And, as a word of advise, you are much more likely to get helpful answers to your questions if you refrain from insulting those who try to help you.
  #16  
Old 03-28-2003, 03:17 PM
Ein Stein Ein Stein is offline
Guest
 
Join Date: Mar 2003
Wrong yet again! Increasing the pressure of an air mixture that doesn't include CO2 does NOT increase the partial pressure of CO2.



You guys are a fountain of misinformation. I am banning myself. This board is pathetic. I'd like to know it all but I'm not going to learn it here.
  #17  
Old 03-28-2003, 03:21 PM
FatBaldGuy FatBaldGuy is offline
Guest
 
Join Date: Jan 2001
Who says that air doesn't include C02?

By the way, Good Riddance!
  #18  
Old 03-28-2003, 03:27 PM
Q.E.D. Q.E.D. is offline
Charter Member
 
Join Date: Jan 2003
Location: Richmond, VA
Posts: 22,536
Air contains about 1.5% CO2. So, nyah!
__________________
SnUgGLypuPpY -- TakE BaCk tHe PiT!
  #19  
Old 03-28-2003, 03:49 PM
Ein Stein Ein Stein is offline
Guest
 
Join Date: Mar 2003
I can't help myself...........

The concentration of CO2 in the atmosphere is about 350 ppm. That about 0.035% not 1.5%. You can look that up, you don't have to make it up. So that's approximately nothing as I said at the beginning.
  #20  
Old 03-28-2003, 04:10 PM
Splanky Splanky is offline
Guest
 
Join Date: Nov 2002
And compared to Bill Gate's yearly income, mine is approximately nothing.
  #21  
Old 03-28-2003, 04:11 PM
Harmonix Harmonix is offline
Guest
 
Join Date: Nov 2002
Quote:
Wrong AGAIN! Squeezing the bottle reduces the area above the liquid temporarily until more dissolved CO2 escapes to equilibrate the pressure to atmospheric. Hence, a decrease in dissolved CO2 concentration and LESS fizz.
Well that guy was a asshole.

but anyway, this question interests me. Wouldn't the plastic bottles tendency to reform push outward against atmospheric pressure along with the partial pressure of the co2 gas? Thus when plastic reforms the co2 gas partial pressure is still actually lower then atmospheric. I'd be willing to bet by the time it takes that to happen you'd open the sucker up and drink it again. Thus, more fizz.

also, where the fuck does he get off saying there would be LESS fizz? a squeezed then reformed bottle has exactly the same area as an unsqueezed bottle. Both equilibrate the CO2 to atmopsheric pressure. The only reason I can think of is that atmopsheric pressure increases more quickly due to less space in a squeezed bottle and therefore there is a greater rate of escape through the cap early on in the timeline of this CO2 equilibration. Then this becomes a calculus question as to wether escape over time in squeezed bottle is greater then lower escape over time + equilibration to atmospheric in an unsqueezed bottle. We have at least circumstantial evidence that the an unsqueezed bottle retains more CO2.

Quote:
So that says that it's NOT the total pressure of gas above the solution that is relevant. Only the proportion of the headspace gas that is CO2 is relevant. I know that bottles are factory-filled with CO2 in the headspace so it makes no sense that replacing it with air will do anything according to Henry's Law.
You sir, are a double moron. You're thinking in terms of IDEAL gases. In real life gas has VOLUME. Increasing TOTAL air pressure above WILL aid in keeping CO2 in. Simply because such a high pressure of gas above will knock the CO2 gases back down. toward the soda. Thus there would be less area of equilibration for the CO2 gas. Now eventually the CO2 gas will equlibrate to around atmospheric, but it'll take ALOT longer. This however brings up the question if the regular air dissolves into soda. Since I don't know the properties of Soda, I will not comment.

This is of course all theory. Do your double blind test, and shut up already.
  #22  
Old 03-28-2003, 04:13 PM
Harmonix Harmonix is offline
Guest
 
Join Date: Nov 2002
Oh yea, Einstein was a humble man. You are insulting his namesake.
  #23  
Old 03-28-2003, 04:15 PM
Splanky Splanky is offline
Guest
 
Join Date: Nov 2002
I was thinking the exact same thing, Harmonix.
  #24  
Old 03-28-2003, 04:23 PM
FatBaldGuy FatBaldGuy is offline
Guest
 
Join Date: Jan 2001
After reading all this discussion, I did some Googling on the subject. A chemistry professor at Montana State University did a study which was published in the Journal of Chemical Engineering
Quote:
The chemistry of the loss of carbonation from carbonated beverages on storage was considered. Increasing the pressure of CO2(g) will restore carbonation, but an increase in pressure adding air should not affect the equilibria. It can and does, however, affect the kinetics-the rate at which a new equilibrium is established. Thus the Fizz Keeper is effective for storage of resealed pop containers for hours, but not for periods of weeks or months.
As much as it pains me to admit it, ein stein was at least partially right. But that doesn't excuse the attitude.
  #25  
Old 03-28-2003, 04:43 PM
Whiskey-Hotel Whiskey-Hotel is offline
Guest
 
Join Date: Mar 2003
Really now. I would've thought that, after a troll rips the soda bottle in two, preserving carbonation would be tha last thing on its mind.
  #26  
Old 03-28-2003, 04:44 PM
ZenBeam ZenBeam is offline
Guest
 
Join Date: Oct 1999
I mostly agree that the pump won't help. We had one and it didn't seem to help any. It won't increase the partial pressure of CO2 by much, just the partial pressure of air. I seem to recall, however, that increasing the pressure on a liquid increases its ability to keep gas in solution, so that may have a (probably small) effect.

What we found kept the soda fizzy was storing the bottle on a shelf, rather than on a door. All that agitation every time you open the door brings the CO2 out of solution faster.
  #27  
Old 03-28-2003, 05:03 PM
bibliophage bibliophage is offline
Charter Member
Charter Member
 
Join Date: Apr 2000
Location: Maine
Posts: 10,057
Harmonix, the use of insults by one poster does not relieve you of the duty to refrain from them yourself.

Since Ein Stein seems intent on not coming back, I'll close this thread to remove the temptation.

bibliophage
moderator GQ
Closed Thread



Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 02:00 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@chicagoreader.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Publishers - interested in subscribing to the Straight Dope?
Write to: sdsubscriptions@chicagoreader.com.

Copyright 2017 Sun-Times Media, LLC.