Safety Emporium for all your lab and safety needs

Anhydride

Glossary Index

Anorexia

MSDS Topics	Free Sites	FAQ's	Regulations	Glossary	Software	Suppliers
	Books	Forum	Poll	Fun stuff	Quiz	Store
Understand your MSDS with the MS-Demystifier				Search ALL our MSDS info

Anhydrous

Definition

• An anhydrous material does not contain any water (H₂O) molecules.

Additional Info

Many substances occur naturally as hydrates, compounds that have a specific number of water molecules (H2O) attached to them. This water can often be removed by heating and/or vacuum to give the anhydrous material. Anhydrous materials can absorb water from their surroundings and find use as desiccants (drying agents). Examples include the packets of silica gel one finds in some consumer goods, as well as dehumidifying sachets used in clothes closets. See our entry on hygroscopic for more details. Anhydrous materials differ from anhydrides. Anhydrides react irreversibly with the oxygen-hydrogen bonds of water to form new compounds whereas anhydrous compounds simply form reversible adducts with water molecules. The hydrated forms of the compounds shown below can be converted into the anhydrous forms by heating. This provides a convenient way of recycling (regenerating or reactivating) the drying agent. In each example below, note the double arrows between the products and reactants that indicate a reversible chemical reaction.

Get drying tubes, drying chambers and other organic laboratory equipment and glassware from Safety Emporium.

MSDS Relevance

Some anhydrous materials are considered water reactive materials, meaning that they could release a large amount of heat possibly leading to a pressure or chemical explosion. Use such materials only with proper precautions and training and pay very careful attention to the firefighting procedures listed on the MSDS!

Further Reading

• Drying Organic Solutions at CU Boulder. Check out the great pictures.
• QuickTime movies that show how chemists dry organic solutions with anhydrous magnesium sulfate and use a simple desiccator by Professor Dan Straus at San Jose State University.
• J.T. Baker (Mallinckrodt Baker) has a handy Desiccant Selection Guide.
• Common desiccant types and additional information at SorbentSystems.com.
• Multisorb has a reprint of an article titled Protection of Pharmaceutical and Diagnositc Products Through Desiccant Technology as well as various product information.

See also: anhydride, hygroscopic.

Additional definitions from Google and OneLook.

Disclaimer: The information contained herein is believed to be true and accurate, however ILPI makes no guarantees concerning the veracity of any statement. Use of any information on this page is at the reader's own risk. ILPI strongly encourages the reader to consult the appropriate local, state and federal agencies concerning the matters discussed herein.