In a wine laboratory, analyzing wine for TA, VA and S02 involves the use of a sodium hydroxide (NaOH) reagent. Winemakers usually buy sodium hydroxide solution of a known concentration. This reagent is relatively unstable and its concentration changes over time. To ensure the accuracy of analytical results it is important to periodically check the concentration (Normality) of sodium hydroxide. If the concentration has changed then it must be readjusted to the original concentration or the new concentration (Normality) value needs to be used in calculations.