Lowers acidity levels. Tartaric acid drops out as potassium bitartrate. Will be more effective if wine is cold stabilized after addition. Not recommended for acid reductions greater than 2 grams/liter(g/l) as higher amounts will effect wine flavor.
1.0 g/liter of potassium carbonate will lower acidity by ~ 1.0 g/liter. Normal acidity levels for must/juice and wine are as follows.
Must/Juice g/L Finished Wine g/L
Dry White 7.0-9.0 5.0-7.5
Dry Red 6.0-8.0 4.0-5.5
Sweet White/Red 7.5-9.0 5.5-7.5
An acid test kit can be used to determine acidity of your must or wine.