I accidentally added way too much Potassium Metabisulfite (KMBS) to my must/wine sample due to a miscalculation on our part. When I perform the SO2 titration I have to use more than a full syringe (5mL) of the SO2 Titrant to get a reading. What can I do? What should I do?

When testing for Free SO2, if you follow the procedures in the normal way and you end up using 5mL + 2.6mL more from a second syringe then your calculation at the end would not need to change. You would simply multiply total volume by 20 as stated in the manual, which would be 7.6*20 = 152

If you know you have high SO2 values and you want to use less of your SO2 Titrant (to conserve your reagents) you can use 10mL of your wine, add 15mL of DI water and then follow the remaining steps as usual, adding your Reactant and Acid solutions and titrating with the SO2 Titrant. This procedure would change the formula you use to calculate your ppm of SO2. Using the large formula for calculating Free SO2 content, listed in the manual (currently on page 6 of the SC-100A manual) your value for ‘S’ would change to 10mL of your wine sample (where normally this is 25mL). And then you can proceed with the calculation of the equation. You will not be able to simply use the 20*V calculation.

Here is the full equation:                                    ppm SO2 = (64*V*N*1000)/2*S  (listed in the manual)

For example: If you use a 10mL wine sample (S), perform the test and you use 3.5 mL of your SO2 Titrant (V), the equation would look like this:

ppm SO2 = (64*3.5*0.0156*1000)/2*10              =             174.72 ppm Free SO2

*When adding DI water to your wine sample, do not worry. This will not affect your SO2 values. Adding this water allows you to bring up your sample volume to a more manageable volume but will not affect your SO2 readings.