This method is used for the determination of volatile acidity in wines and musts. The applicable range of this method is 0.012 to 0.120 g/100ml. The range can be extended by sample dilution.
The sample is diluted and treated with hydrogen peroxide to oxidize interfering sulfite compounds. It is then distilled at 120°C under acidic conditions. The volatile acids are condensed and combined with a weakly buffered solution of bromophenol blue. Changes in pH due to the presence of the volatile acids cause a proportional color change that is read at 440 nm. Results are expressed as g/100ml of acetic acid.
The distillation eliminates interferences from colored wine samples and separates volatile from nonvolatile acids. Treatment with hydrogen peroxide eliminates interferences from sulfites. Particulate matter should be removed or centrifuged to prevent clogging in the system.