Measuring Soda Carbonation

[tkmacon4]

What is an easy way to measure carbonation in soda? Would like to see which type soda has the most carbonation, i.e. coke, sprite, mountain dew.... Thanks,

[deleted-71712]

Hi tkmacon4,

Welcome to the forum! Sounds like you've come up with a fun idea for a project.

I did a quick internet search, and one simple and inexpensive method would be to build a CO2 trap using a glass measuring cup (or maybe a graduated cylinder borrowed from your school's lab) turned upside down in a deep bowl of water. You would want there to be no air in the measuring cup initially, and you would run a tube from a freshly opened bottle to inside the cup:

http://en.allexperts.com/q/Science-Kids ... soda-1.htm
http://en.allexperts.com/q/Science-Kids ... eryday.htm

As the gas escapes from the liquid, it will accumulate inside the cup, and when it finishes (which could take more than a day, for planning purposes :) ), you can read the volume from the measuring cup. Make sure to plug the bottle's opening well with something like silly putty. One thing to consider is that cold soda will lose CO2 more slowly, which will mean that less will escape while you're setting up the connection, but the experiment will take longer to complete. If the description of the CO2 trap doesn't make sense, let me know and I'll draw you a picture, since there aren't any.

So, before you take the measurements, do you have a hypothesis? Which drinks do you think have the most carbonation, and why? Your reasons could be manufacturer's claims, people's opinions, etc.

Best wishes,
Amanda

[deleted-71712]

Oh, one more thing: One way this could go wrong is if the measuring cup tips over and allows air to escape, and it certainly doesn't sound like you'll be able to sit there the whole time. If the cup is made of something relatively heavy like glass *and* the CO2 it collects takes up less than half of its volume, it should probably be stable. I'm not sure whether the instructions linked were based on 2-liter bottles or single-serving bottles, so you might want to do a test run while you still have plenty of time to complete the experiment. You could also put something heavy on top of the cup.

It might be a good idea to measure a few bottles of each drink, since there can be variation from bottle to bottle. If time becomes an issue, you could consider building more than one trap so you can measure multiple bottles at the same time.

Good luck!

Amanda

[occammd]

I have been doing what you said for 2 hours and the Co2 is going away. Do you have any suggestions on what I should do?

From: Sean
4th grade.

[deleted-71712]

Hi Sean,

Welcome to the forum. What do you mean by "going away"? Is the CO2 not being trapped by your upside-down cup? Or is it being trapped by the cup, but you aren't sure what to do next?

If no gas is appearing in the upside-down cup, then you probably have a leak somewhere between the soda bottle and the cup. What kind of tube did you use? Did you plug the gap between the bottle mouth and tube with something impermeable to air, such as silly putty?

Another thing to note is that the links describing this set-up (I haven't done the experiment myself) said it could take over a day for all CO2 to escape from the soda, and you've only waited two hours. That said, it should lose CO2 more quickly at the beginning, so you probably should have seen a visible accumulation of gas by now.

If the CO2 is being trapped by the upside-down cup -- first, your soda is probably not completely flat after 2 h, so wait until the volume of gas in the cup has stopped increasingly -- at least a day. If you used a measuring cup, then you can read the volume from the side of the cup (make sure you're not holding it at an angle). If you didn't use a measuring cup, then you can do this instead: mark the level of the gas on the side of the upside-down cup (holding it level) -- you could use a piece of tape if you don't want to write on the cup or if the water washes away the mark. Then, take the cup out, and fill it with water to the level you marked. Pour this into a measuring cup (or graduated cylinder if you have it) and see what the volume is.

Again, I'm not totally clear on the problem you're having, so if you clarify what you have done and what you need help with, I can probably give better advice.

Amanda

[sciencebuddy]

Hi tkmacon4,

It seems like you're doing fine with the actual set up.

My only suggestion is that it is absolutely vital to do 3 trials per soda type. Otherwise, your results will not be valid.
It's difficult to believe that the amount of gas is completely consistent for one brand. However, one of the things you should look for is how big the variation is.