MadSci Network: Chemistry

Re: How can you determin the alcohol percentage in beer?

Date: Tue Mar 9 19:27:18 1999
Posted By: Dr. Michael Weibel, Battelle Chemist
Area of science: Chemistry
ID: 920811447.Ch

Hello Wim.  

This is a question I had several years ago.  There are published 
techniques in the literature (one such technique resides in an older 
edition of Skoog and West's Analytical Chemistry text...maybe 2nd 

The most available (and probably simplest) method for performing this 
experiment will be with a GC.  If you make dilute solutions of beer (I 
think that there are too many dissolved solids in undiluted beer, which 
will coat the GC column and may cause future problems)that has been left 
out for several hours to allow carbonation to disperse (I recall that 
dissolved carbonation is an interference), and then run against dilute 
ethanol solutions (to generate a calibration curve), you should be able to 
determine what the alcohol % is in the original beer.

As a side note:  % alcohol is typically expressed as % weight/weight 
(called percent by weight) or % volume/volume (called percent by volume).  
the % by weight is the weight of alcohol divided by the weight of the 
whole solution.  The percent by volume is the volume of alcohol divided by 
the total volume.  If the concentration is X% volume/volume, then the 
concentration % weight/weight is about 0.8 * % volume/volume since the 
density of alcohol is about 0.8 g/mL and that of water is about 1 g/mL, 
assuming dilute solution so that the solution is effectively all water.  
As such, % by volume will always be larger.

I hope this helps.  If you are looking for a procedure, try a few 
analytical chemistry texts.  Please feel free to email me if you have 
further questions.

Best Regards,


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