A copper-sulphur compound (old name is copper vitriol), which presents itself as a powder of transparent blue crystals; without water content this is a white powder. It is used - often in combination with copper citrate and silver chloride - to remove the wine faults of Böckser and Käseln (since the substance is undesirable in wine, it is subsequently removed by silica sol ). The chemical was formerly used extensively to control pests on vines, potato plants and fruit trees. It is also used to dehydrate alcohol.
Copper sulphate is also a component of Bordeaux broth, which used to be widely used as the main agent against various fungal diseases such as downy mildew. Today it is increasingly being replaced by synthetic fungicides. In some countries, such as Germany, copper sulphate is now banned as a plant protection agent because many soils have become excessively enriched with copper, which is harmful to health in higher quantities, as a result of decades of excessive use. See also under Agents used in winemaking.