Sorbate DOES NOT kill yeast! It only prevents the yeast from budding, and inhibits renewed yeast activity under the correct conditions. Although sorbate prevents yeast refermentation, it may not stop an active (or sluggish) fermentation. You should add .5 to .75 grams per gallon of Sorbate WITH .5 gram KMETA per gallon to effectively stop fermentation.
One out of every four people suffer from mental illness. Think of your three best friends - if they are OK, then it's you!