Final answer:
Metallic salts, like those of aluminum, copper, iron, and chromium, are used as mordants in conjunction with natural dyes to bind color to fabric and can alter the color outcome by forming coordination complexes with the dyes.
Step-by-step explanation:
Metallic salts used with natural dyes can act as mordants, which are substances that bind the dye to the fabric. Some of the metallic salts used include salts of aluminum, such as alum, copper salts like copper sulfate, iron salts such as ferrous sulfate, and chromium salts like potassium dichromate. These salts can affect the color outcome by forming a coordination complex with the natural dye, which can alter the perceived color. For example, cobalt salts containing Co²⁺ cations can create a variety of colors by changing the species surrounding the cobalt ion. The presence of water molecules in the coordination sphere around the central cobalt ion changes the distances among species and the color of the material, producing bright colors often found in transition metal compounds, such as cobalt (II) nitrate, potassium chromate, and copper (II) sulfate.