Sodium Hydroxide is used for measuring the acid concentration of wine must. To use you will need to accurately measure a 15.0 millilitre or "mL" sample into the container and add 4 or 5 drops of indicator solution. Fill the syringe to the 10 mL mark with the 0.2 N. sodium hydroxide solution. Add sodium hydroxide solution drop-by-drop to the sample. With white musts or wines, you will see that each drop creates a fleeting pink zone which vanishes when the sample is swirled. Keep adding the sodium hydroxide until the pink flush just becomes persistent throughout the whole sample, but does not become bright red. This is your "endpoint".