What Is a Hydrate in Chemistry?

There are a number of phenomena that occur naturally in the world around us but that our science is only now beginning to understand. One such occurrence is the formation of the hydrate, a chemical compound created with a number of different molecules and one common denominator: water.

Definition

A hydrate is a molecule that contains some type of water. Often, a base molecule is taken and a water molecule is added to it, in order to create another molecule with different properties. In some instances, the water molecules become a part of the structure of the original molecule. In others, the water is attached to the center of the original molecule, rather than blending into the structure. This process is called water of hydration.
For example, chloral hydrate (as seen in the illustration) is a hydrate of the molecule chloral. Choral reacts with water to form an entirely different substance--the choral hydrate--which is one of the fundamental ingredients in the pesticide DDT and acts as a sedative.

History

Research into the properties and uses of hydrates began in the early 1800s as part of research being carried out by Humphry Davy and Michael Faraday. While experimenting with mixtures of chlorine and water, the scientists noticed that there were strange formations that were crystallizing in the samples when they were well above the freezing point of water. They developed the theory that the molecules were stabilizing themselves by bonding with another, more stable molecule in the vicinity.
It wasn't until the 1930s that another scientist, E.G. Hammerschmidt, determined that these oddities were responsible for causing blockages in natural gas lines that ran through cold areas.
By the 1970s, conditions for methane hydrate formation had been isolated. It was thought that methane hydrate would be a naturally occurring form of gas energy. Russian efforts produced methane hydrates from the depths of the ocean, encouraging research to go a step further in the creation and application of hydrates as a natural energy source.

Function

Hydrates change the base molecule that the water bonds itself to, and the result is a compound that is as flexible as it is numerous. Different hydrates have different uses, and some are used every day.
Hydrates are commonly found in skin care products such as moisturizer, shampoo and lip balm. Hydrates replace the skin's moisture and repair tissue damaged by cold and dryness.
Hydrates are used in many industrial processes, especially when two compounds need to be separated. An example of this is desalination, or the removal of salt from water. The hydrate is combined with the raw salt water, and the bonds within the molecules change. There are some molecules that are more readily combined than others, and by using this principle it is possible to create fresh water from salt water. The same principle also works with gases.

Considerations

It is possible for a hydrate to lose its water molecule; when this occurs, it is called an anhydride.
For example, sodium hydroxide is a compound that is commonly known as lye. In this, its hydrated form, it is a common ingredient in soaps, detergents and drain cleaners. Lye is a toxic chemical often used in its raw form as the decomposing agent used with the carcasses of farm animals and roadkill. With the water in the chemical compound removed, however, the hydrate becomes the anhydride sodium oxide. Sodium oxide is one of the critical components in the making of glass.

Potential

The potential of these naturally occurring hydrates has intrigued scientists for decades, especially methane hydrate. In this combination, the water molecule completely surrounds the methane molecule without actually bonding to it. It is thought by the scientific community that there is a possibility to harness the energy stored in methane hydrate for a future energy source. Under the right conditions--which research has found at the bottom of several seas--methane hydrate can be produced inexpensively and in mass quantities. There are, however, a number of issues that need to be overcome first, including questions of safe drilling practices and the stability of the environment in which the hydrate is found.