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The total gas pressure in beer is measured after the beer has been forcefully shaken. The carbon dioxide is then bound through the addition of potassium hydroxide. The amount of air in the beer contributes the remaining volume of gas. Once the value for the total pressure has been corrected by subtracting the quantity of air present in the beer, the carbon dioxide can be measured [1].

This device makes use of a method patented and entitled by Anton Paar "Multiple Volume Expansion". Here, the volume in the measuring chamber is increased in two separate steps, and at the end of each step the equilibrium pressure and temperature are recorded for use in the calculation. The true carbon dioxide content is determined independently of any other gases which may be dissolved in the beverage [1, 2, 3].

The figure below depicts the calibration correcting for air in the sample and shows how the effect of any dissolved gases other than CO₂ (air or nitrogen) on the result of the analysis is eliminated using the volumetric expansion employed in this method. The CO₂ content is determined after two separate volumetric expansions in the measuring chamber. If no dissolved other gases are present in the sample, the two results are identical, and no correction is necessary. If gases other than CO₂ are dissolved in the sample, this causes the result to be lower after the larger volumetric expansion (the second measurement) than the result at smaller volumetric expansion (the first measurement). A correction value is calculated based upon the difference between the two results, which completely eliminates the influence of the dissolved foreign gases (air or nitrogen) on the ultimate result of the analysis.