Sulfate is a chemical compound that contains a certain group of associated atoms of sulfur and oxygen. This group is known as the sulfate radical. The radical has an electrical charge of -2. Most sulfates are stable compounds, formed in crystals. Common sulfates are celestite, a sulfate of strontium; Epsom salt, a sulfate of magnesium; and gypsum, a sulfate of calcium. Many sulfates are soluble in water, but some, such as barium, strontium, and lead sulfates, do not dissolve in water.
Sulfates have a number of important industrial uses. Copper sulfate, also known as blue vitriol, is used in many industries, including dyeing and calico printing, a process of imprinting color designs on cloth. Iron sulfate is used in making ink and as a medicine. Zinc sulfate is used in surgery as an antiseptic, in calico printing, and in making drying oils for varnishes. Some baking powders contain alum, a double sulfate of potassium and aluminum.
