complex salt


a salt that contains one or more complex ionsCompare double salt



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What does complex salt mean?

A complex salt is a salt that contains one or more complex ions—ions with metal centers and different molecules attached. In chemistry, a salt is any compound composed of oppositely charged ions. These ions are negative (called anions) and positive (called cations), resulting in a charge of zero. Complex salts are distinguished from simple salts and double salts, which have different makeups. Complex salts include potassium ferricyanide (used to create dyes and in blueprint paper) and potassium argentocyanide (used in silver plating).

Why is complex salt important?

The salt we put on food (sodium chloride, a.k.a. table salt) is just one of the compounds in chemistry known as salts. But sodium chloride is a simple salt. When two simple salts are combined to form a new crystal structure, you get a double salt. So what’s a complex salt? You might not associate salt with metal, but in chemistry, there is a connection. When a metal combines with another metal, it forms an alloy (bronze is an alloy of copper and tin, for example). When a metal combines with oxygen, it forms an oxide. And when a metal combines with a nonmetal, it forms a salt. Some of these are simple salts, some are double salts, and others are complex salts, meaning “a salt that contains two different types of metal atoms, one of which does not separate when it's in a solution.” That last part is one of the defining characteristics of complex salts—they do not completely dissolve. When you put regular old table salt (which is a simple salt) in water, you know that it will dissolve completely. When you put a double salt in water, it separates into its component ions and dissolves. But the makeup of a complex salt ensures that it does not fully dissolve. It’s this characteristic that makes complex salts useful for several applications, such as in dyes. (And that makes them likely to be something you mix up in chem lab.)

Did you know ... ?

Prussian blue is a dark blue pigment that is made with potassium ferricyanide, a complex salt. It has been used in famous paintings, such as Starry Night by Vincent van Gogh and The Great Wave off Kanagawa by Katsushika Hokusai.

What are real-life examples of complex salt?

It’s usually chemists who discuss complex salts, but they can be used in diverse applications, ranging from dyes to semiconductor materials.

Getty / Vincent van Gogh


What other words are related to complex salt?

Quiz yourself!

True or false? Complex salts produce simple salts when dissolved in water.

Scientific definitions for complex salt

complex salt

A salt that contains two different types of metal atoms, one of which does not ionize when in solution. Mercury iodide (HgI2) is a complex salt. Compare double salt simple salt.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.