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". When titrating reds, work with a brightly lit background. As you add sodium hydroxide solution, the red of the grapes will gradually disappear and turn to a greyish shade. When the sample is a definite greyish - greenish shade, you are close to the endpoint. The endpoint is reached as a reddish tinge reappears due to the colour change of the indicator solution.This is sold as a replacement and is to be used with our Acid Testing Kits (MSR005).