MadSci Network: Chemistry

Re: Is there a way to measure carbonation levels?

Date: Mon Oct 18 13:56:30 1999
Posted By: Kieran Kelly, MadSci Admin
Area of science: Chemistry
ID: 940189675.Ch

Tough problem.  The carbonated beverage industry uses an apparatus called a 
Zahm & Nagel 
tester to measure CO2 pressure inside a sealed container.  They then compare the 
pressure they measure with a temperature/pressure/solubility curve for carbon 
dioxide to determine exactly how much CO2 is in there.  This equipment is not 
something you will have lying around your classroom...  I suppose your choices 
are either: try to make the equivalent of a Zahm & Nagel tester, or use a 
titration method.  

The ZN tester is essentially a pressure gauge with an angled point strong enough 
to pierce the bottle cap or can.  You would need to make sure the seal is tight 
so you don't lose any CO2 to the atmosphere (which is why the gauge is mounted 
on the two rails).  Rather clumsy and could be difficult to use.

On the other hand, you should already have what you need to titrate carbonic 
acid, using phenolphthalein as an indicator.  CO2 reacts with water to form 
carbonic acid so, if you titrate the soda right after you open it, you should 
get a fairly accurate measure of the CO2 content.  This method will run 
into problems if you want to titrate a cola or a darkly-colored beverage so you 
might think about using a pH meter to identify the titration endpoint (around pH 
= 7).

Good luck with your experiments!  I kinda miss playing with soda...


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