FAQ: What is Bocksin?
Answered by Ken Beard

Answer: Bocksin is a solution of silicum dioxide used to remove hydrogen sulfide (H2S) odors from wine (the dreaded rotten egg smell). If caught early, most H2S problems can be eliminated by vigorously splash racking the wine, but if the odor persists Bocksin may be the answer. A third level of defense against H2S is the use of copper sulfate, but CuS04  is toxic, so if you don’t have a degree in organic chemistry or vast experience as a winemaker – don’t use it.

To use Bocksin, add approximately 2 teaspoons per 5 gallons of wine. Stir the wine thoroughly, wait 24 hours and then rack the wine without disturbing the sediment.

The downside to Bocksin is that it tends to leave the wine cloudy (so it may be necessary to fine), and occasionally there will be a loss of aromatic complexity. However, these minor problems are usually preferable to throwing out the wine because it smells like hydrogen sulfide.